Systems and methods for treating black liquor solutions

Abstract

Disclosed herein are systems and methods for concentrating a black liquor solution using a pressure driven filtration process. The systems and methods described herein integrate multiple unit operations with a graphene oxide membrane filtration apparatus to achieve concentration of a black liquor stream. These systems and methods provide a lower energy, more economical solution than currently employed thermal evaporation techniques.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to and the benefit of U.S. Provisional Patent Application 63 / 437,963, filed January 9, 2023, entitled “Systems and Methods for Processing Black Liquor Solutions,” the disclosure of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present disclosure relates to systems and methods for concentrating black liquor solutions using pressure driven filtration processes, and more particularly to systems and methods that integrate multiple unit operations with graphene oxide membranes to achieve a solution for lower energy and more economical concentration of black liquor streams. BACKGROUND

[0004] Black liquor is a byproduct of the kraft pulping process that is produced during the digestion of pulping wood to produce cellulose fibers for paper pulp and paper products. Black liquor contains residual pulping residuals, primarily lignin and hemicellulose, inorganic chemicals from the kraft process (e.g., sodium hydroxide and sodium sulfate), and other extractives contained in the wood (e.g., tall oil). Paper mills typically use multi-effect thermal evaporators to treat black liquor to increase the solids content in the black liquor from 10-15% to 65-80%. The high solids content black liquor is then burned in a recovery boiler to produce steam that provides energy to the paper mill and recovers chemicals used in the digestion process. Thermal evaporation is a slow and energy intensive process that has a considerable impact on kraft mill energy consumption, efficiency, and cost. Therefore, there is a need in the art for new systems and methods for treating black liquor that address the shortcomings of thermal evaporators and provide a way to reduce costs and improve plant operating efficiency. SUMMARY

[0005] Embodiments described herein generally relate to systems and methods for concentrating black liquor solutions using pressure driven filtration processes, including graphene oxide membranes. One aspect of the disclosure relates to a system comprising: a feed preparation assembly, a first filtration module, a second filtration module, a third filtration module, and a fourth filtration module. The feed preparation assembly is configured to receive a black liquor feed having an initial total concentrate with dissolved and suspended solids, the feed preparation assembly further configured to remove suspended solids from the black liquor feed to produce a conditioned feed. The first filtration module includes a graphene oxide membrane. The first filtration module is fluidly coupled to the feed preparation assembly and configured to contact the conditioned feed with the graphene oxide membrane at a predetermined temperature to produce a first concentrate and a first permeate. The second filtration module is fluidly coupled to the first filtration module. The second filtration module is configured to receive the first permeate and produce a second concentrate and a second permeate. The third filtration module is fluidly coupled to the second filtration module. The third filtration module is configured to receive the second permeate and produce a third concentrate and a third permeate. The fourth filtration module is disposed downstream of the third filtration module. The fourth filtration module is configured to receive the third permeate and produce a treated permeate, wherein the first, second, and third concentrates are combined to produce a treated concentrate having a total solids concentration higher than the initial total solids concentration.

[0006] In some embodiments, the feed preparation assembly is further configured to remove a portion of the dissolved solids from the black liquor feed to produce the conditioned feed.

[0007] In some embodiments, the initial total solids concentration is about 10 to 15 wt.%, and the graphene oxide membrane produces the first permeate having a total solids concentration of no more than about 7 wt.%.

[0008] In some embodiments, the graphene oxide membrane produces the first concentrate having a total solids concentration of at least about 15 wt.%.

[0009] In some embodiments, the predetermined temperature is at least about 70 °C.

[0010] In some embodiments, the graphene oxide membrane has a total solids rejection rate of at least about 50% at the predetermined temperature and a pressure of no more than 800 psi.

[0011] In some embodiments, the first filtration module further includes a primary stage housing the graphene oxide membrane, the primary stage configured to recycle a portion of the first concentrate to the conditioned feed.

[0012] In some embodiments, the filtration module further comprises a primary stage and a secondary stage. The primary stage houses a first graphene oxide membrane. The primary stage is configured to (1) contact the conditioned feed with the first graphene oxide membrane to produce an intermediate concentrate, and (2) recycle a portion of the intermediate concentrate to the conditioned feed. The secondary stage houses a second graphene oxide membrane. The secondary stage is disposed downstream of the primary stage and is configured to contact the intermediate concentrate with the second graphene oxide membrane to produce the first concentrate.

[0013] In some embodiments, the secondary stage is configured to recycle a portion of the first concentrate to the conditioned feed.

[0014] In some embodiments, the feed preparation assembly comprises one or more tubular ceramic membranes.

[0015] In some embodiments, the second filtration module comprises a polymer membrane. The second filtration module is configured to contact the first permeate with the first polymer membrane to produce a second concentrate and a second permeate.

[0016] In some embodiments, the first permeate is contacted with the first polymer membrane at a temperature of no more than about 50 °C and a pressure of about 700-1100 psi.

[0017] In some embodiments, the polymer membrane produces the second permeate having a total solids concentration of no more than about 3 wt.%. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 An exemplary system for processing a black liquor (BL) feed is schematically shown in accordance with one embodiment.

[0019] Figure 2 A diameter distribution of fibers recovered from a black liquor feed is shown using scanning electron microscopy (SEM) analysis.

[0020] Figure 3 Table 1 is a table describing a list of feed treatment and / or separation equipment that can be included in a feed preparation assembly, with their estimated minimum pore size and ability to operate continuously.

[0021] Figure 4 Figure 1 is a plot of total dissolved solids of permeate (permeate TDS) as a function of volume concentration factor (VCF) for a black liquor feed treated with exemplary ceramic membranes.

[0022] Figure 5 Figure 2 is a plot of differential pressure as a function of time measured across a set of membranes included in a filtration module that flow untreated black liquor (BL) feed and black liquor (BL) feed treated with a feed preparation assembly comprising a 50 pm felted bag filter.

[0023] Figure 6 A feed preparation assembly integrating a heat exchanger and a feed treatment / separation apparatus for treating a black liquor (BL) feed is illustratively shown in accordance with one embodiment.

[0024] Figure 7 is a schematic illustration of an arbitrary size graphene oxide membrane configuration in accordance with some embodiments, in which two graphene oxide membranes are disposed parallel to each other to receive a feed and produce a concentrate fluid and a permeate fluid.

[0025] Figure 8A is a plot of the total solids rejection rate as a function of time for an exemplary polymeric reverse osmosis (RO) membrane operating in a black liquor solution at 63 °C.

[0026] Figure 8B is a plot of the total solids rejection rate as a function of time for an exemplary graphene oxide membrane operating in a black liquor solution at 70 °C.

[0027] Figure 9A is a plot of the flux in gallons per square foot per day (GFD) as a function of the total solids concentration present in the feed for a polymeric reverse osmosis (RO) membrane.

[0028] Figure 9B is a plot of the flux in gallons per square foot per day (GFD) as a function of the total solids concentration present in the feed for a high solids content reverse osmosis (RO) polymeric membrane.

[0029] Figure 10A is a plot of the flux in gallons per square foot per day (GFD) as a function of time for a polymeric ultrafiltration (UF) membrane having a molecular weight cut-off of about 10 kDa during operation in a black liquor feed.

[0030] Figure 10B is a plot of the flux in gallons per square foot per day (GFD) as a function of time for a graphene oxide membrane during operation in a black liquor feed.

[0031] Figure 11 is a plot of the flux in gallons per square foot per day (GFD) as a function of the total dissolved solids of the concentrate produced by a nanofiltration (NF) membrane and a reverse osmosis (RO) membrane.

[0032] Figure 12A is a table describing a comparison of the concentrations of species of the treated permeate and the combined condensate from the evaporator system.

[0033] Figure 12BTable summarizing the total concentration of dissolved solids and conductivity of the permeate product after each filtration module according to one embodiment.

[0034] Figure 13 An exemplary system for treating black liquor (BL) feed according to one embodiment is schematically illustrated.

[0035] Figure 14 A plot of membrane flux (in gallons per square foot per day (GFD)), permeate conductivity (mS / cm), and permeate refractive index (Brix) as a function of feed total dissolved solids (TDS) for black liquor conditioning according to one embodiment is shown for a graphene oxide membrane coated on a nanofiltration membrane used as a support (e.g., GO / NF membrane) and a graphene oxide membrane coated on a reverse osmosis membrane used as a support (e.g., GO / RO membrane).

[0036] Figure 15 Table summarizing the flux in (GFD) and permeate total dissolved solids (TDS) for graphene oxide membranes operated at different operating pressures in a black liquor feed according to one embodiment.

[0037] Figure 16 Table summarizing the number of filtration modules and type of membrane included in each filtration module for a system for treating black liquor (BL) feed according to one embodiment. DETAILED DESCRIPTION

[0038] Black liquor is a byproduct of the kraft pulping process, produced during the conversion of wood into cellulose fibers for use in pulp and paper products. Black liquor produced in a pulp mill can contain sodium sulfate, sodium carbonate, sodium hydrosulfide, sodium thiosulfate, and / or sodium hydroxide, residual fibers from the pulping process, and larger size (e.g., high molecular weight) organic species including hemicellulose, cellulose, and lignin, among others. In some examples, a black liquor stream can have a total solids concentration in the range of about 10 to 20 wt.%. Existing methods and / or approaches for treating a black liquor stream generally include feeding the black liquor into a series of thermal evaporators to remove water until the solids content in the black liquor is increased to about 65 to 80 wt.%. The black liquor with high solids content is then fed into a recovery boiler to generate steam and recover pulping chemicals used during the kraft pulping process. The evaporated water is condensed and recycled for future use within the plant. This method and / or approach for treating black liquor is energy intensive and accounts for about 30% of the total kraft pulp mill energy consumption.

[0039] Pressure driven membrane separations are a technology that can be up to 90% more energy efficient than thermal evaporation because the need for liquid to vapor phase transition in a thermal evaporator is eliminated by the separation of material species through a membrane. Thus, the use of pressure driven membranes to treat black liquor provides an opportunity to save costs for a mill by reducing energy usage and / or consumption. Polymeric membranes constitute one of the most common types of membranes used in pressure driven separation and / or purification applications. Polymeric membranes lead the membrane separation industry due to their high performance, ease of mass production, and overall cost. Polymeric membranes can be prepared using a variety of monomers selected to impart the desired properties to the membrane, including temperature stability, mechanical strength, and / or affinity for the particular material species and / or components to be separated. Polymeric membranes, and more specifically reverse osmosis (RO) membranes, have been used commercially in a wide range of applications including water purification, desalination, wastewater treatment, biological purification, and concentration, removal, and purification of different salts, small molecules, and macromolecules. Despite these advantages, the use of (RO) membranes to treat black liquor is limited. Most (RO) membranes are designed to separate material species at moderate temperatures, for example 35-45°C. Black liquor is produced at higher temperatures, for example 90°C, and thus treating black liquor requires membranes that can exhibit thermal stability, high performance, and durability under those operating conditions. The use of heat exchangers to reduce the temperature of the black liquor solution and enable the use of (RO) membranes has proven to be impractical due to the associated operating costs. Additionally, reducing the temperature of the black liquor can result in precipitation of one or more components and / or material species having limited solubility in the black liquor stream. Precipitation of solid material species from the black liquor stream can cause membrane fouling and an increase in the pressure differential across the membrane, which can significantly reduce the durability of the membrane. The present disclosure provides systems and methods for treating black liquor that address the limitations of existing membranes and exhibit one or more superior performance over existing membranes. At least by integrating different unit operations including graphene oxide membranes and (RO) membranes in a particular sequence and / or method, the systems and methods described herein can enable concentration of black liquor and provide a lower cost and higher energy efficiency alternative to existing art thermal evaporators.

[0040] Reference will now be made to the drawings, Figure 1A schematic diagram of an example system 1000 for processing black liquor feed is shown, according to one embodiment. The system 1000, which can also be referred to herein as a "black liquor processing system 1000" or a "processing system 1000," can be configured to receive a black liquor (BL) feed 100 and process it to produce a treated concentrate 110 and a treated permeate 120 having a set of desired and / or target properties (e.g., a target electrical conductivity and / or a target total dissolved solids (TDS)). The processing system 1000 includes a feed preparation assembly 130, a filtration module and / or assembly 140, a filtration module and / or assembly 150, a filtration module and / or assembly 160, and a filtration module and / or assembly 170. Optionally, in some embodiments, the processing system 1000 can include storage assemblies 141, 151, and 161 coupled to the filtration modules 140, 150, and 160, respectively. Figure 1 A feed preparation assembly 130 of the processing system 1000 is shown, which can receive a BL feed 100, perform one or more preparation and / or conditioning steps, and produce a conditioned feed 101. The BL feed 100 can be any suitable black liquor stream produced in a mill having a total solids concentration in the range of about 10 to 20 wt.%.

[0041] The feed preparation assembly 130 can be configured to perform one or more preparation and / or conditioning steps to remove material suspended on the BL feed 100, including a portion (or all) of large size organic species classes produced during the pulping process and / or dissolved in the BL feed 100. For example, in some embodiments, the feed preparation assembly 130 can be configured to remove a substantial portion of residual fibers and other suspended material present in the BL feed 100. In other embodiments, the feed preparation assembly 130 can be configured to remove a substantial portion of residual fibers and other suspended material, as well as a portion of large size organic species classes (e.g., hemicellulose, cellulose, lignin, etc.) dissolved in the BL feed 100. In other words, the feed preparation assembly 130 can be configured to receive a BL feed 100 containing an initial amount of dissolved and suspended solids (e.g., an initial total amount of solids) and remove a portion of the initial total amount of solids in the BL feed 100, thereby producing a conditioned feed 101. In some embodiments, the feed preparation assembly 130 can be configured to remove a certain percentage of the initial total amount of solids in the BL feed 100, including, for example, about 10%, about 15%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about 90%, or about 100%, including all values and ranges therebetween. In some embodiments, the feed preparation assembly 130 can include one or more heat exchangers Figure 1The conditioned feed 101 can be directed and / or flowed to the filtration module 140 at the predetermined temperature for further processing until a treated concentrate 110 and a treated permeate 120 are produced, as further described herein. Optionally, in some embodiments, the conditioned feed 101 can be stored in a storage compartment 141 prior to being directed to the filtration module 140, as further described herein.

[0042] The feed preparation assembly 130 can include any suitable feed treatment and / or separation equipment configured to receive the BL feed 100 and remove suspended solids and / or large size dissolved organic species on the BL feed 100 to produce the conditioned feed 101. The suspended solids present in the BL 100 feed are primarily comprised of residual fibers produced during the kraft pulping process having a concentration of about 10-1000 mg / L, and large size dissolved organic species including, for example, hemicellulose, cellulose, lignin. Removal of these fibers and large size dissolved organic species protects the pumps, membranes, heat exchangers, and other components of the treatment system 1000 from fouling and / or accumulation of debris that leads to reduced flow rates, increased pressure drops, overheating, and / or other undesirable effects. Fouling of the membranes and / or other components of the treatment system 1000 can be extremely difficult to reverse, thus potentially leading to permanent degradation of performance.

[0043] The feed preparation assembly 130 can include feed treatment and / or separation equipment characterized by small pore size separation media, high stability at elevated temperatures and alkaline conditions, and the ability to operate continuously with minimal number of cleaning cycles. In particular, the feed preparation assembly 130 can include one or more feed treatment and / or separation equipment that includes separation media having an average pore size that is smaller than the average size of the fibers and other materials suspended on the BL feed 100. As such, the BL feed 100 flowing through and / or past the feed treatment and / or separation equipment included in the feed preparation assembly 130 results in the retention of a substantial portion of the fibers and other materials suspended on the BL feed 100. In some embodiments, the separation media can also retain a portion (or all) of the large size dissolved organic species (e.g., hemicellulose, cellulose, lignin, etc.), while allowing the remaining portion and / or fraction of the large size dissolved organic species and other dissolved solids including sodium sulfate, sodium carbonate, sodium bisulfide, etc., and other species including sodium sulfate, sodium carbonate, sodium bisulfide, etc., to pass through. Figure 2 is an outlier box plot showing the diameter distribution of fibers recovered from the black liquor feed, obtained by analyzing scanning electron microscope (SEM) images of the recovered fibers. Figure 2A rectangular box encloses the obtained primary diameter data is shown. More specifically, the lower end of the rectangular box represents the 25th percentile of the diameter data (~ 15 μιη), the upper end of the rectangular box represents the 75th percentile of the diameter data (~ 23 μιη), and the horizontal line within the rectangular box represents the median diameter (~ 18 μιη). From Figure 2 the lower and upper ends of the rectangular box in FIG. 6, vertical lines extending indicate the outermost data points that are within 1.5 times the interquartile range. Observing Figure 2 the data shown in FIG. 6, it is revealed that the majority of fibers suspended in the black liquor feed have diameters between about 5 and 25 μιη. Accordingly, in some embodiments, the feed preparation assembly 130 can include one or more feed treatment and / or separation devices characterized by a pore size that prevents passage of any fibers and / or suspended material having a size of about 5 μιη or greater.

[0044] In some embodiments, the feed preparation assembly 130 can include one or more feed treatment and / or separation devices characterized by an average pore size of no greater than about 25 μιη, no greater than about 10 μιη, no greater than about 9 μιη, no greater than about 8 μιη, no greater than about 7 μιη, no greater than about 6 μιη, no greater than about 5 μιη, no greater than about 4 μιη, no greater than about 3 μιη, no greater than about 2 μιη, no greater than about 1 μιη, no greater than about 0.9 μιη, no greater than about 0.8 μιη, no greater than about 0.7 μιη, no greater than about 0.6 μιη, no greater than about 0.5 μιη, no greater than about 0.4 μιη, no greater than about 0.3 μιη, no greater than about 0.2 μιη, or no greater than about 0.1 μιη, including all values and ranges therebetween.

[0045] In some embodiments, the feed preparation assembly 130 can include one or more feed treatment and / or separation devices characterized by a molecular weight cut-off (MWCO) of about 1 kDa, about 2 kDa, about 4 kDa, about 6 kDa, about 8 kDa, about 10 kDa, about 12 kDa, about 14 kDa, about 16 kDa, about 18 kDa, about 20 kDa, about 25 kDa, about 50 kDa, about 100 kDa, about 150 kDa, or about 200 kDa, including all values and ranges therebetween.

[0046] In some embodiments, the feed preparation assembly 130 can include one or more pressure screens, wedge wire filters, centrifugal devices, screen or felt sock-like filters, etc., featuring average pore sizes consistent with the ranges disclosed above (e.g., average pore sizes of about 0.1 to 25 pm). In some embodiments, the feed preparation assembly 130 can include clean-in-place (CIP) mechanisms that enable the feed preparation assembly 130 to operate continuously, avoiding interruptions due to the accumulation of fibers and other materials removed from the BL feed 100 over time. For example, in some embodiments, the feed preparation assembly 130 can include CIP mechanisms such as backflushing, mechanical cleaning, or chemical treatment. In preferred embodiments, the feed preparation assembly 130 can include one or more ceramic membranes having any suitable shape / form (e.g., tubular and / or planar or flat sheet). The ceramic membranes can include single-pass and / or multi-pass geometries containing separation media having average pore sizes of about 1 kDa to about 10 pm. The ceramic membranes can be configured to have average pore sizes that are smaller than the average size of the fibers and other materials suspended in the BL feed 100, such that the ceramic membranes prevent those materials from passing through (e.g., the ceramic membranes retain residual fibers and other materials of suspended material). Additionally, the average pore sizes of the ceramic membranes can also facilitate the removal and / or rejection of a portion of the large size dissolved organic species (e.g., hemicellulose, cellulose, lignin, etc.). For example, in some embodiments, the ceramic membranes can remove and / or reject a certain percentage of the large size organic species dissolved in the BL feed 100, the percentage being about 10%, about 15%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about 90%, or about 100%, including all values and ranges therebetween.

[0047] In some embodiments, feed preparation assembly 130 can include a first set of feed treatment and / or separation devices characterized by small pore sizes (e.g., average pore sizes of about 1 kDa to about 10 μιη) and a second set of feed treatment and / or separation devices characterized by medium average pore sizes (e.g., average pore sizes of about 10 to 100 μιη). In some embodiments, the first set of feed treatment and / or separation devices can include, for example, one or more ceramic membranes, filter presses, and / or wedge wire. The first set of feed treatment and / or separation devices of feed preparation assembly 130 can be used to remove fibers suspended in BL feed 100 that come from the digestion of pulped wood in the kraft process. In some embodiments, the first set of feed treatment and / or separation devices can also remove a portion (or all) of the large size dissolved organic species (e.g., hemicellulose, cellulose, lignin, etc.). In some embodiments, the second set of feed treatment and / or separation devices can include, for example, one or more bag filters, candle filters, pressure screens, and / or belt filters. The second set of feed treatment and / or separation devices can be used to remove other materials having an average particle size greater than 10 μιη on BL feed 100. In such embodiments, feed preparation assembly 130 can be configured to receive BL feed 100 and then pass BL feed 100 through the second set of feed treatment and / or separation devices (in series, in parallel, and / or in a series / parallel combination). Exposure of BL feed 100 to the second set of feed treatment and / or separation devices can facilitate the removal of very large species suspended on BL feed 100 that can cause extensive damage if not removed first and / or increased pressure drops on the first set of feed treatment and / or separation devices having much smaller average pore sizes. After BL feed 100 is exposed to the second set of feed treatment and / or separation devices, BL 100 feed can then be directed to the first set of feed treatment and / or separation devices to remove suspended fibers and / or large size dissolved organic species produced in the kraft process.

[0048] BL feed 100. In such embodiments, feed preparation assembly 130 can be configured to receive BL feed 100 and then pass BL feed 100 through the second set of feed treatment and / or separation devices (in series, in parallel, and / or in a series / parallel combination). Exposure of BL feed 100 to the second set of feed treatment and / or separation devices can facilitate the removal of very large species suspended on BL feed 100 that can cause extensive damage if not removed first and / or increased pressure drops on the first set of feed treatment and / or separation devices having much smaller average pore sizes. After BL feed 100 is exposed to the second set of feed treatment and / or separation devices, BL 100 feed can then be directed to the first set of feed treatment and / or separation devices to remove suspended fibers and / or large size dissolved organic species produced in the kraft process.

[0049] BL feed 100. In such embodiments, feed preparation assembly 130 can be configured to receive BL feed 100 and then pass BL feed 100 through the second set of feed treatment and / or separation devices (in series, in parallel, and / or in a series / parallel combination). Exposure of BL feed 100 to the second set of feed treatment and / or separation devices can facilitate the removal of very large species suspended on BL feed 100 that can cause extensive damage if not removed first and / or increased pressure drops on the first set of feed treatment and / or separation devices having much smaller average pore sizes. After BL feed 100 is exposed to the second set of feed treatment and / or separation devices, BL 100 feed can then be directed to the first set of feed treatment and / or separation devices to remove suspended fibers and / or large size dissolved organic species produced in the kraft process.

[0050] Figure 3 A table is shown that describes a list of various feed treatment and / or separation devices that can be included in feed preparation assembly 130, with their estimated minimum pore sizes and ability to operate continuously. In some embodiments, each of the above feed treatment and / or separation devices, including Figure 3those shown in FIG. 1, can be operated in multiple stages (or "stages" or "phases") and / or passes, as desired, to achieve desired reductions in fiber content and / or other suspended solids and a portion (or all) of the large size dissolved organic species. In some embodiments, the feed preparation assembly 130 can include various feed treatment and / or separation devices coupled and / or combined to achieve desired removal of fibers and / or other materials suspended in the BL feed 100. For example, in some embodiments, the feed preparation assembly 130 can include one or more wedge wire filters and one or more tubular ceramic membranes fluidly coupled and / or combined to achieve desired levels of removal of fibers and other suspended materials present in the BL feed 100.

[0051] As noted above, in some embodiments, the feed preparation assembly 130 can include one or more ceramic membranes (tubular and / or flat sheet) having an average pore size of about 1 kDa to about 10 pm. In particular, in some embodiments, the feed preparation assembly 130 can include one or more tubular ceramic membranes arranged and / or disposed in a series, parallel, and / or series / parallel combination configuration, wherein the tubular ceramic membranes comprise a separation media having a relatively small average pore size of no greater than about 100 nm, no greater than about 80 nm, no greater than about 60 nm, no greater than about 40 nm, no greater than about 20 nm, no greater than about 15 nm, no greater than about 10 nm, no greater than about 8 nm, no greater than about 7 nm, no greater than about 5 nm, no greater than about 4 nm, or no greater than about 3 nm, including all values and ranges therebetween. In some embodiments, the feed preparation assembly 130 can include one or more tubular ceramic membranes arranged and / or disposed in a series, parallel, and / or series / parallel combination configuration, wherein the tubular ceramic membranes comprise a separation media having a relatively small average pore size of no more than about 300 kDa, no more than about 250 kDa, no more than about 200 kDa, no more than about 150 kDa, no more than about 100 kDa, no more than about 80 kDa, no more than about 60 kDa, no more than about 40 kDa, no more than about 20 kDa, no more than about 10 kDa, no more than about 5 kDa, no more than about 1 kDa, no more than about 800 Da, no more than about 700 Da, no more than about 600 Da, no more than about 500 Da, or no more than about 400 Da, including all values and ranges therebetween. Use of tubular ceramic membranes having such small average pore sizes can facilitate removal of suspended fibers and large size dissolved organic species (e.g., hemicellulose, cellulose, lignin, etc.), resulting in a concentrate stream (not shown in FIG. 1) and a permeate stream (e.g., adjusted feed 101 in FIG. 1) characterized by a relatively low amount of total dissolved solids (TDS). Figure 1 Figure 1 As noted above, in some embodiments, the feed preparation assembly 130 can include one or more ceramic membranes (tubular and / or flat sheet) having an average pore size of about 1 kDa to about 10 pm. In particular, in some embodiments, the feed preparation assembly 130 can include one or more tubular ceramic membranes arranged and / or disposed in a series, parallel, and / or series / parallel combination configuration, wherein the tubular ceramic membranes comprise a separation media having a relatively small average pore size of no greater than about 100 nm, no greater than about 80 nm, no greater than about 60 nm, no greater than about 40 nm, no greater than about 20 nm, no greater than about 15 nm, no greater than about 10 nm, no greater than about 8 nm, no greater than about 7 nm, no greater than about 5 nm, no greater than about 4 nm, or no greater than about 3 nm, including all values and ranges therebetween. In some embodiments, the feed preparation assembly 130 can include one or more tubular ceramic membranes arranged and / or disposed in a series, parallel, and / or series / parallel combination configuration, wherein the tubular ceramic membranes comprise a separation media having a relatively small average pore size of no more than about 300 kDa, no more than about 250 kDa, no more than about 200 kDa, no more than about 150 kDa, no more than about 100 kDa, no more than about 80 kDa, no more than about 60 kDa, no more than about 40 kDa, no more than about 20 kDa, no more than about 10 kDa, no more than about 5 kDa, no more than about 1 kDa, no more than about 800 Da, no more than about 700 Da, no more than about 600 Da, no more than about 500 Da, or no more than about 400 Da, including all values and ranges therebetween. Use of tubular ceramic membranes having such small average pore sizes can facilitate removal of suspended fibers and large size dissolved organic species (e.g., hemicellulose, cellulose, lignin, etc.), resulting in a concentrate stream (not shown in FIG. 1) and a permeate stream (e.g., adjusted feed 101 in FIG. 1) characterized by a relatively low amount of total dissolved solids (TDS). Figure 4 As noted above, in some embodiments, the feed preparation assembly 130 can include one or more ceramic membranes (tubular and / or flat sheet) having an average pore size of about 1 kDa to about 10 pm. In particular, in some embodiments, the feed preparation assembly 130 can include one or more tubular ceramic membranes arranged and / or disposed in a series, parallel, and / or series / parallel combination configuration, wherein the tubular ceramic membranes comprise a separation media having a relatively small average pore size of no greater than about 100 nm, no greater than about 80 nm, no greater than about 60 nm, no greater than about 40 nm, no greater than about 20 nm, no greater than about 15 nm, no greater than about 10 nm, no greater than about 8 nm, no greater than about 7 nm, no greater than about 5 nm, no greater than about 4 nm, or no greater than about 3 nm, including all values and ranges therebetween. In some embodiments, the feed preparation assembly 130 can include one or more tubular ceramic membranes arranged and / or disposed in a series, parallel, and / or series / parallel combination configuration, wherein the tubular ceramic membranes comprise a separation media having a relatively small average pore size of no more than about 300 kDa, no more than about 250 kDa, no more than about 200 kDa, no more than about 150 kDa, no more than about 100 kDa, no more than about 80 kDa, no more than about 60 kDa, no more than about 40 kDa, no more than about 20 kDa, no more than about 10 kDa, no more than about 5 kDa, no more than about 1 kDa, no more than about 800 Da, no more than about 700 Da, no more than about 600 Da, no more than about 500 Da, or no more than about 400 Da, including all values and ranges therebetween. Use of tubular ceramic membranes having such small average pore sizes can facilitate removal of suspended fibers and large size dissolved organic species (e.g., hemicellulose, cellulose, lignin, etc.), resulting in a concentrate stream (not shown in FIG. 1) and a permeate stream (e.g., adjusted feed 101 in FIG. 1) characterized by a relatively low amount of total dissolved solids (TDS). Figure 1 ​101 in the conditioned feed 101) produced by the feed preparation assembly 130 comprising different tubular ceramic membranes operating on the BL feed 100. More specifically, Figure 4 The permeate TDS (%) is shown as a function of the volume concentration factor (VCF, the ratio of the volume and / or volume flow rate of the BL feed 100 to the volume and / or volume flow rate of the generated permeate stream) for a first tubular ceramic membrane having an average pore size of about 0.1 μm and a second tubular ceramic membrane having an average pore size of about 15 kDa. Figure 4 It was shown that, for a wide range of volume concentration factors, reducing the average pore size of the tubular ceramic membrane from 0.1 mm to 15 kDa resulted in the formation of a permeate with a significantly lower TDS. For example, exposing the BL feed 100 to a tubular ceramic membrane having an average pore size of approximately 15 kDa at a VCF of 3.0 produced a permeate with a TDS of approximately 10.8%. Exposing the same BL feed 100 to a tubular ceramic membrane having an average pore size of 0.1 μm at the same VCF of 3.0 produced a permeate with a TDS of approximately 12.6%.

[0052] Reducing TDS in the BL feed 100 using tubular ceramic membranes having a small average pore size (such as those described above) can enable the system 1000 to achieve performance targets (e.g., a treated concentrate 110 and a treated permeate 120 having a set of desired and / or target properties (e.g., a target conductivity and / or target TDS)) with a reduced number of filtration modules and / or passes, as further described herein. In other words, in some embodiments, using a feed preparation assembly 130 comprising one or more tubular ceramic membranes having a small average pore size (e.g., those described above) enables the system 1000 to produce a conditioned feed 101 having a low TDS (e.g., about 4 to about 18 wt. % TDS). This low TDS in the conditioned feed 101 requires a reduced number of passes and / or filtration modules to produce a concentrate 110 and a permeate 120 having a set of desired and / or target properties (e.g., a target conductivity and / or TDS), thereby avoiding the need for, e.g., Figure 1 The illustrated processing system 1000 may be used to process all channels and / or filter modules as needed. Figure 13 Such embodiments are further disclosed.

[0053] The feed preparation assembly 130 can have a direct impact on the differential pressure (dP) observed across a set of filtration modules 140, 150, 160, and 170. Inefficient removal of fibers and other materials suspended in the BL feed 100 can result in increased dP caused by fibers becoming stuck, fixed, pinned, and / or attached to, for example, the membrane feed spacers of the filtration modules. Figure 5A plot showing differential pressure as a function of time measured across a set of membranes included in the treatment system 1000 (e.g., a set of membranes included in the filtration modules 140, 150, 160, and 170 shown in Figure 1 FIG. 1) as the untreated BL feed 100 and the conditioned feed 101 (e.g., a black liquor feed treated with the feed preparation assembly 130 including a 50 pm felt bag filter) are flowed. The dP curve observed for the untreated BL feed 100 remains relatively constant for the first day of operation and then gradually increases until almost doubling the initial differential pressure after only 8 days of operation of the treatment system 1000. The increasing dP observed in the untreated BL feed 100 can result in reduced membrane flux, loss of performance, and mechanical failure of the membranes and / or other components of the filtration modules, resulting in higher operating costs and limited efficiency. The dP curve observed for the conditioned feed 101 shows an initial differential pressure of similar magnitude to the untreated BL feed 100. However, unlike the untreated BL feed 100, the conditioned feed 101 remains relatively constant during the first 8 days, which is indicative of the impact of the feed preparation assembly 130 on the stability of the treatment system 1000.

[0054] As noted above, in some embodiments, the feed preparation assembly 130 can include one or more heat exchangers (not shown in Figure 1 FIG. 1) that can be used to adjust the conditioned feed 101 to a predetermined temperature prior to directing the conditioned feed 101 to the filtration module 140 for further treatment. In some embodiments, the BL feed 100 can be directed to a feed treatment and / or separation device to produce the conditioned feed 101, and then the conditioned feed 101 can be sent to a heat exchanger to adjust its temperature to a predetermined value (e.g., a predetermined temperature). Figure 6 A schematic diagram illustrating such an embodiment is shown. More specifically, Figure 6It is shown that the feed preparation assembly 130 can include a heat exchanger 132 disposed downstream of the feed treatment and / or separation device 134. The feed treatment and / or separation device 134, which can also be referred to herein as the "separation device 134," can be similar to and / or the same as any of the feed treatment and / or separation devices disclosed above. The separation device 134 can receive the hot BL feed 100 and remove residual fibers and other materials suspended in the BL feed 100. Optionally, in some embodiments, the separation device 134 can also remove a portion of the large size dissolved organic species, such as hemicellulose, cellulose, lignin. Because sufficiently high temperatures (e.g., above 75 °C) can cause damage to one or more subassemblies of the separation device 134 (e.g., damage to filters, screens, membranes, and / or ancillary subassemblies), in some embodiments, the separation device 134 can include a cooling system. For example, in some embodiments, the separation device 134 can include a passive cooling system. The passive cooling system can include a non-insulated pipe, a membrane enclosure, or a combination thereof. In some embodiments, the passive cooling system can include a suitable heat sink configured to conduct heat away from one or more subassemblies of the separation device 134, such as membranes, screens, and / or filters. The heat sink can be formed of any suitable metal (e.g., copper, aluminum, steel, etc.). In some implementations, the heat sink can include fins configured to dissipate heat into the ambient air. Additionally or alternatively, in some embodiments, the separation device 134 can include an active cooling system. The active cooling system can include a fan for improving heat dissipation from the fins of one or more heat sinks. In some embodiments, the active cooling system can also include a water sprayer for spraying water onto parts and / or subassemblies of the separation device 134.

[0055] As noted above, the separation apparatus 134 can remove residual fibers and other suspended materials from the hot BL feed 100; producing a hot conditioned feed 101. The hot conditioned feed 101 can be directed to a heat exchanger 132 to be cooled to a predetermined temperature before being directed to the filtration module 140. The heat exchanger 132 can be any suitable heat exchanger configured to cool the hot conditioned feed 101 by transferring heat from the hot conditioned feed 101 to a working fluid. In some embodiments, the heat exchanger 132 can be a convection / conduction heat exchanger (e.g., the heat exchanger 132 utilizes transfer of thermal energy from a surface by movement of a cooling fluid relative to a surface of a housing containing the hot conditioned feed 101). Here, it is important to note that the term "hot BL feed 100" indicates that the temperature of the BL feed 100 entering the separation apparatus 134 is higher than the "hot conditioned feed 101" entering the heat exchanger 132. Similarly, the term "hot conditioned feed 101" indicates that the temperature of the conditioned feed 101 entering the heat exchanger 132 is higher than the cold conditioned feed 101 exiting the heat exchanger. During heat exchange, the hot conditioned feed 101 can be cooled by about tens of degrees. In exemplary embodiments, the hot conditioned feed 101 can be cooled by at least about 10 degrees Celsius (10 °C) and no more than about 40 °C.

[0056] In some embodiments, the feed preparation assembly 130 can include a heat exchanger, which can be used to adjust the conditioned feed 101 to a predetermined temperature. In some embodiments, the predetermined temperature of the conditioned feed 101 can be at least about 60 °C, at least about 65 °C, at least about 70 °C, at least about 75 °C, at least about 80 °C, at least about 85 °C, at least about 90 °C, or at least about 95 °C, including all values and ranges therebetween. In some embodiments, the predetermined temperature of the conditioned feed 101 can be less than about 96 °C, less than about 92 °C, less than about 88 °C, less than about 84 °C, less than about 80 °C, less than about 76 °C, less than about 72 °C, less than about 68 °C, or less than about 64 °C, less than about 60 °C, including all values and ranges therebetween.

[0057] Combinations of the above-noted ranges for the predetermined temperature of the conditioned feed 101 are also possible (e.g., at least about 60 °C to less than about 90 °C or at least about 68 °C to less than about 80 °C).

[0058] Further details of the integration of the heat exchanger with the feed processing and / or separation equipment 134 are described in the disclosure of International Patent Application No. PCT / US2022 / 080120, entitled “Heat Exchanger Integration with Membrane System for Evaporator Pre-concentration,” filed on November 18, 2022 (the '120 Application), which is incorporated herein by reference. Alternatively, in some embodiments (not shown), the feed preparation assembly 130 may include a heat exchanger disposed downstream of one or more feed processing and / or separation equipment, wherein the heat exchanger is configured to adjust the temperature of the conditioned feed 101 prior to directing the conditioned feed 101 to the filtration module 140.

[0059] The filtration module 140 can be any suitable filtration device that is fluidly coupled to the feed preparation assembly 130 and is configured to receive the conditioned feed 101 at a predetermined temperature and produce a concentrate 102 and a permeate 103. Optionally, in some embodiments, the filtration module 140 can include a storage assembly 141 that can be used to hold and / or store the conditioned feed 101 for a period of time prior to its processing. The storage assembly 141 can include and / or be one or more tanks of any suitable shape, size, and / or capacity. The storage assembly 141 can include one or more valves, inlets, or ports (not shown) that are configured to allow liquid to flow into or out of the tanks of the storage assembly 141 (e.g., to at least partially fill one or more tanks, collect samples for quality control purposes, etc.).

[0060] Filtration module 140 (also referred to herein as "filtration assembly 140" or "first filtration module, channel, and / or assembly" of processing system 1000) is positioned downstream of feed preparation assembly 130, as shown in FIG. Figure 1 As shown. The filter module 140 includes one or more graphene oxide membranes. According to one or more configurations, the graphene oxide membrane can be disposed on the filter module 140. For example, in some embodiments, the filter module 140 may include two or more graphene oxide membranes disposed parallel to each other, such as Figure 7The filtration module 140 can receive the conditioned feed 101 at a predetermined temperature, then flow, direct, and / or contact the conditioned feed 101 with graphene oxide membranes included in the filtration module 140. Selected species included in the conditioned feed 101 can be allowed to diffuse through the graphene oxide membrane(s) to produce a permeate fluid, such as the permeate 103. Other species present on the conditioned feed 101 can be rejected by the graphene oxide membrane (e.g., prevented from diffusing through the graphene oxide membrane), and thus produce a concentrate fluid, such as the concentrate 102.

[0061] In some embodiments, the graphene oxide membranes can be disposed on a support substrate configured to provide mechanical stability to the graphene oxide membranes. The support substrate can include a plurality of planar polymer sheets that combine to form a spiral filtration configuration. For example, in some embodiments, the spiral filtration configuration and / or module can include a plurality of planar polymer sheets stacked on one another. The plurality of stacked planar polymer sheets can be wound around a core tube. In some embodiments, prior to being wound around the core tube, adjacent planar polymer sheets can be separated by sheets of feed channel spacers to form leaves, and each leaf can be separated by a sheet of permeate spacer. When the planar polymer sheets, one or more feed channel spacers, and one or more permeate spacers are wound around the core tube, each permeate spacer can form a permeate channel. In such embodiments, the support substrate can include a material selected from polypropylene, polystyrene, polyethylene, polyox, polyethersulfone, polytetrafluoroethylene, polyvinylidene fluoride, polymethyl methacrylate, polydimethylsiloxane, polyester, cellulose, cellulose acetate, cellulose nitrate, polyacrylonitrile, fiberglass, quartz, alumina, silver, polycarbonate, nylon, Kevlar, or other aramid, or polyether ether ketone. In some embodiments, the support substrate can be and / or include any suitable membrane, such as an ultrafiltration (UF) membrane, a nanofiltration (NF) membrane, and / or a reverse osmosis (RO) membrane.

[0062] In some embodiments, the filtration module 140 can process the conditioned feed 101 in multiple stages as needed, with the concentrate from each stage being fed to a subsequent stage(s). For example, as shown in FIG. 1, in some embodiments, the filtration module 140 can include a primary stage 142 and one or more optional auxiliary stages 143 fluidically coupled to and disposed in series downstream of the primary stage 142. The primary stage 142 and the auxiliary stages 143 can each include and / or house one or more graphene oxide membranes according to any suitable configuration, including, for example, a spiral filtration configuration. Figure 1 Figure 7 ​The primary stage 142 can receive the adjusted feed 101 and then flow, direct, and / or contact it with the graphene oxide membranes disposed therein to produce a primary stage concentrate and a primary stage permeate. The primary stage concentrate produced by the primary stage 142 can be directly fed to the secondary stage 143 disposed downstream. The secondary stage 143 can receive the primary stage concentrate and produce the concentrate 102 and a secondary permeate. The primary and secondary permeates produced in the primary stage 142 and secondary stage 143, respectively, can be combined to produce the permeate 103. Figure 1

[0063] In some embodiments, the primary stage 142 and the secondary stage 143 can each be configured to recirculate a portion and / or fraction of the concentrate product in each stage, as shown. To achieve this, each stage can be equipped with a recirculation pump (not shown) to enable higher recovery and lower energy consumption of the treatment system 1000. More specifically, recirculating a portion of the concentrate produced in a certain stage to the feed of that stage allows the earlier stages (e.g., the primary stage 142 and those secondary stages 143 disposed closer to the primary stage 142) to operate at lower solids than the final secondary stage 143 (e.g., the secondary stage 143 disposed further downstream of the primary stage 142). This improves flux by reducing the osmotic pressure of the adjusted feed 101 and prevents membrane fouling. Figure 1

[0064]

[0065] The graphene oxide membranes included in the filtration module 140 can be similar to and / or the same as the graphene oxide membranes disclosed in U.S. Patent No. 11,097,227, entitled “Durable Graphene Oxide Membranes,” issued August 24, 2021 (“864 Patent”), International Patent Application No. PCT / US2022 / 078051, entitled “Filtration Apparatus Containing Alkylated Graphene Oxide Membrane,” filed October 13, 2022 (“051 Application”); and U.S. Patent No. 11,123,694, entitled “Filtration Apparatus Containing Graphene Oxide Membrane,” issued September 21, 2021 (“694 Patent”), which are incorporated by reference herein.

[0066] ​​​It is important to note that the integration of graphene oxide membranes in filtration module 140 enables and / or facilitates the treatment of black liquor (e.g., conditioned feed 101) at temperatures between about 60 to 90 °C and elevated pH (e.g., 11-13) to produce and / or generate (1) a concentrate 102 that is primarily comprised of organic species such as lignin and hemicellulose, and (2) a permeate 103 that is primarily comprised of monovalent and divalent inorganic salts and a small amount of organic species. The ability to operate at such high temperatures stems from the thermal stability of graphene oxide membranes and their chemical stability under harsh alkaline conditions (e.g., pH = 11 to 13). The integration of graphene oxide membranes with treatment system 1000 provides a method of concentrating black liquor streams using pressure driven membranes, separating a majority of the large organic species present in black liquor in a first filtration module (e.g., filtration module 140). This is a result that cannot be achieved using conventional (RO) membranes disclosed in the prior art.

[0067] As noted above, the graphene oxide membranes included in filtration module 140 allow for the treatment of conditioned feed 101 at temperatures between about 60 to 90 °C to produce and / or generate concentrate 102. Concentrate 102 is primarily comprised of organic species, such as lignin and hemicellulose. In some embodiments, concentrate 102 can have a total solids concentration of at least about 10 wt.%, at least about 11 wt.%, at least about 12 wt.%, at least about 13 wt.%, at least about 14 wt.%, at least about 15 wt.%, at least about 16 wt.%, at least about 17 wt.%, at least about 18 wt.%, at least about 19 wt.%, at least about 20 wt.%, at least about 21 wt.%, at least about 22 wt.%, at least about 23 wt.%, at least about 24 wt.%, or at least about 25 wt.%, including all values and ranges therebetween.

[0068] Combinations of the above-mentioned ranges for total solids concentration in concentrate 102 are also possible (e.g., at least about 15 wt.% to less than about 25 wt.%, or at least about 13.5 wt.% to less than about 22 wt.%).

[0069] The graphene oxide membranes included in the filtration module 140 also allow for the separation of the conditioned feed 101 at temperatures between about 60 to 90 °C to produce and / or generate a permeate 103 that primarily contains smaller divalent and monovalent salts, including, for example, sodium hydroxide (NaOH) and sodium sulfate (Na2S04). In some embodiments, the permeate 103 can have a total solids concentration of no more than about 9.0 wt.%, no more than about 8.0 wt.%, no more than about 7.5 wt.%, no more than about 7.0 wt.%, no more than about 6.5 wt.%, no more than about 6.0 wt.%, no more than about 5.5 wt.%, no more than about 5.0 wt.%, no more than about 4.5 wt.%, no more than about 4.0 wt.%, no more than about 3.5 wt.%, no more than about 3.0 wt.%, or no more than about 2.5 wt.%, including all values and ranges therebetween.

[0070] Combinations of the above-mentioned ranges for the total solids concentration in the permeate 103 are also possible (e.g., at least about 3.0 wt.% to less than about 7.0 wt.%, or at least about 3.5 wt.% to less than about 6.0 wt.%).

[0071] Unlike graphene oxide membranes, (RO) membranes are designed for processes such as desalination and wastewater treatment, which are typically performed at low temperatures near and / or close to room temperature (e.g., 25 °C). As a result, the materials used to manufacture (RO) membranes, as well as other components (or assemblies) for (RO) membrane systems, are typically limited to a maximum temperature range of 35 to 45 °C. Due to the associated operating expenses, as well as the limited solubility of some species and / or components of black liquor that can precipitate out of the black liquor solution, it has proven impractical to use heat exchangers to reduce the temperature of the black liquor such that conventional (RO) membranes can be used to treat the black liquor. Precipitation of one or more species and / or components in the black liquor can increase the likelihood of membrane fouling, which in turn can result in a decrease and / or deterioration of the performance and durability of the membrane.

[0072] Figure 8A A plot of the total solids rejection rate as a function of time is shown for a filtration module including a (RO) membrane operated in a black liquor solution at a temperature of 63 °C. Figure 8A A plot of the total solids rejection rate as a function of time is shown for a filtration module including a graphene oxide membrane operated in a conditioned feed 101 at a temperature of 70 °C and a pressure of about 300 psi. Figure 8B A plot of the total solids rejection rate as a function of time is shown for a filtration module 140 including a graphene oxide membrane operated in a conditioned feed 101 at a temperature of 70 °C and a pressure of about 300 psi. Figure 8BThe graphene oxide membranes are shown to maintain a stable total solids rejection of at least 60% over a continuous operating time span of over 200 days, demonstrating excellent stability. The total solids rejection can be measured by electrical conductivity (Cond) and / or refractive index (RI), and the total solids rejection is calculated as

[0073] In some embodiments, the graphene oxide membranes included in the filtration module 140 can exhibit a total solids rejection of at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, or at least about 95%, including all values and ranges therebetween, at an operating temperature of about 60 to 90 °C. In some embodiments, the graphene oxide membranes included in the filtration module 140 can exhibit a total solids rejection of no more than about 94%, no more than about 88%, no more than about 84%, no more than about 80%, no more than about 76%, no more than about 72%, no more than about 68%, no more than about 64%, no more than about 60%, no more than about 56%, no more than about 52%, no more than about 48%, or no more than about 44%, including all values and ranges therebetween, at an operating temperature of about 60 to 90 °C.

[0074] Combinations of the above-mentioned ranges for the total solids rejection of the graphene oxide membranes are also possible (e.g., at least about 60% less than about 90% or at least about 68% to less than about 80%).

[0075] As noted above, the integration of the graphene oxide membranes in the filtration module 140 enables and / or facilitates the treatment of the black liquor (e.g., the conditioned feed 101) at temperatures between about 60 to 90 °C to produce and / or generate a concentrate 102 that primarily contains organic species such as lignin and hemicellulose. Prior to treatment through the filtration module 140, the conditioned feed 101 can have a total solids concentration in the range of about 4 to 18 wt.%. The filtration module 140 can treat the conditioned feed 101 and produce a concentrate 102 having a total solids concentration in the range of 15 to 25 wt.%. Conventional (RO) membranes cannot operate at this range of solids concentrations. The ultra-tight pores of (RO) membranes provide a barrier to even very small species (e.g., monovalent salts). As a result, the osmotic pressure, i.e., the minimum pressure that must be applied to the conditioned feed 101 being treated in the filtration module 140 to achieve flow through the membrane, exceeds the pressure rating (e.g., at least about 1200 psi or higher) of both (RO) membranes and standard pressure vessels. In contrast, the graphene oxide membranes have a looser inter-pore spacing that allows monovalent salts and some divalent salts to pass through while retaining larger species such as lignin and hemicellulose. Thus, the osmotic pressure of the conditioned feed 101 being treated in the filtration module 140 having graphene oxide membranes is significantly reduced, allowing operation at moderate pressures (e.g., at pressures equal to and / or below about 800 psi).

[0076] In some embodiments, the graphene oxide membranes included in the filtration module 140 can be subjected to an osmotic pressure of less than about 800 psi, less than about 500 psi, less than about 480 psi, less than about 460 psi, less than about 440 psi, less than about 420 psi, less than about 400 psi, less than about 380 psi, less than about 360 psi, less than about 320 psi, less than about 300 psi, less than about 280 psi, less than about 260 psi, less than about 220 psi, less than about 200 psi, less than about 180 psi, less than about 160 psi, less than about 140 psi, less than about 120 psi, less than about 100 psi, less than about 80 psi, less than about 70 psi, less than about 60 psi, or less than about 50 psi, including all values and ranges therebetween. In some embodiments, the graphene oxide membranes included in the filtration module 140 can be subjected to an osmotic pressure of at least about 50 psi, at least about 75 psi, at least about 100 psi, at least about 125 psi, at least about 150 psi, at least about 175 psi, at least about 200 psi, at least about 250 psi, at least about 300 psi, at least about 350 psi, at least about 400 psi, at least about 450 psi, at least about 500 psi, at least about 600 psi, at least about 700 psi, or at least about 800 psi, including all values and ranges therebetween.

[0077] Combinations of the above-mentioned ranges for osmotic pressure experienced by the graphene oxide membranes are also possible (e.g., osmotic pressures of about 200 psi to about 800 psi, about 250 psi and about 480 psi).

[0078] Notably, in some embodiments, the conditioned feed 101 can be directed and / or flowed to the filtration module 140 under a pump pressure. In some embodiments, the osmotic pressure of the conditioned feed 101 in the filtration module 140 can be a percentage of the pump pressure. For example, in some embodiments, the osmotic pressure of the conditioned feed 101 can be about 50% or less, about 45% or less, about 40% or less, about 35% or less, or about 30% or less of the pump pressure. The osmotic pressure is less than the pump pressure to allow some overpressure to drive flux and transport. Selection of the predetermined operating pressure can increase the flux of the graphene oxide membranes, as well as increase the TDS obtained in the permeate stream of the membranes. For example, Figure 15 A table summarizing the flux (GFD) and total dissolved solids (TDS, wt%) of the permeate of graphene oxide membranes included in the filtration module 140 operating at different operating pressures in the conditioned feed 101 is shown. Figure 15 The data included in Table 2 was recorded for the filtration module 140 including graphene oxide membranes disposed on a polyethersulfone (PES) ultrafiltration (UF) membrane serving as a support substrate, operating at 70 °C in the conditioned feed 101 treated in the feed preparation assembly 130 including a tubular ceramic membrane having an average pore size of about 15 kDa. Figure 15 An increase in pressure from 300 psi to 500 and 800 psi is shown to result in an increase in flux and a decrease in permeate solids.

[0079] Figure 9A and 9B A graph showing the flux in gallons per square foot per day (GFD) of a polymeric (RO) membrane as a function of the total solids concentration present in the feed is shown. Figure 9A and 9B The (RO) membrane is highlighted as not being able to operate in solutions containing high total dissolved solids concentrations, such as the conditioned feed 101 and / or other black liquor streams, due to low flux. Figure 9A A conventional (RO) membrane, such as a polyamide Filmtec TMflux (gallons per square foot per day, GFD) of a SW30 membrane (Dow Filmtec® SW30 membrane, DuPont) as a function of total solids concentration (wt.%) in the feed. The flux through the (RO) membrane decreased by over 50% as the total solids concentration in the feed increased from about 3.4 wt.% to about 7.2 wt.%. Based on a linear fit, the flux through the (RO) membrane was predicted to reach zero at a total solids concentration of about 10.2 wt.% in the feed, which is well below the desired operating range required for the first filtration module 140.

[0080] Even (RO) membranes designed for higher solids operation do not exhibit suitable performance for treating the conditioned feed 101 and / or other black liquor streams. Figure 9B (RO) membranes designed for operation in high concentrations of solids (e.g., polyamide Filtec® SW30 membranes, Dow) are described. TM Fortilife TM flux (gallons per square foot per day, GFD) of a SW30 membrane (Dow Filmtec® SW30 membrane, DuPont) as a function of total solids concentration (wt.%) in the feed. The flux through the (RO) membrane decreased by over 50% as the total solids concentration in the feed increased from about 3.4 wt.% to about 7.2 wt.%. Based on a linear fit, the flux through the (RO) membrane was predicted to reach zero at a total solids concentration of about 10.2 wt.% in the feed, which is well below the desired operating range required for the first filtration module 140.

[0081] The use of ultrafiltration (UF) membranes for treatment of black liquor has also proven unsuccessful. Despite the fact that (UF) membranes can have larger pore sizes than conventional (RO) membranes, and are therefore not limited by osmotic potential, their use for treating black liquor streams (e.g., BL feed 100) is hindered due to fouling. Due to the high total concentration of solids contained in the conditioned feed 101 and / or other black liquor streams, and the various constituent species, ultrafiltration membranes can be prone to fouling. In some examples, the species contained in the conditioned feed 101 and / or other black liquor streams can interact with the UF membrane and cause irreversible fouling. Figure 10A A graph showing the flux of an ultrafiltration (UF) polymer membrane (e.g., a polyethersulfone (PES) membrane) having a molecular weight cut-off of about 10 kDa as a function of time during operation in a black liquor feed similar to the conditioned feed 101 is shown. Figure 10A It is shown that, within the first 100 hours of membrane operation, the flux decreased from 7 GFD to less than 2 GFD due to fouling of the (RO) membrane. In contrast, Figure 10B A graph showing the flux of a graphene oxide membrane included in the filtration module 140 as a function of time during operation in the conditioned feed 101 is shown. When compared to the (UF) membrane shown in FIG. 2, Figure 10A The graphene oxide membrane exhibits superior flux stability when compared to the (UF) membrane shown in FIG. 2. After an initial drop from about 7.5 GFD to about 5 GFD within the first 24 hours of operation, Figure 10BThe flux of the graphene oxide membrane is shown to be stable for the remainder of the test. The stability of the flux observed for the graphene oxide membrane provides evidence of the resistance of the graphene oxide membrane to degradation due to fouling in the conditioned feed 101.

[0082] Returning to Figure 1 , the treatment system 1000 also includes a filtration module 150. The filtration module 150 can be any suitable filtration device fluidly coupled to the filtration module 140 and configured to receive the permeate 103 and produce a concentrate 104 and a permeate 105. Optionally, in some embodiments, the filtration module 150 can include a storage assembly 151 that can be used to hold and / or store the permeate 103 for a period of time prior to treatment of the permeate 103. The storage assembly 151 can be similar and / or identical to the storage assembly 141 described above with reference to the filtration module 140. Accordingly, no further description of the storage assembly 151 will be provided herein.

[0083] The filtration module 150, which can also be referred to herein as a “filtration assembly 150” or a “second filtration module, channel, and / or assembly” of the treatment system 1000, is disposed downstream of the filtration module 140, as shown in Figure 1 . The filtration module 150 can be similar to the filtration module

[0084] 140 described above. Accordingly, portions and / or aspects of the filtration module 150 can be similar and / or substantially identical to portions and / or aspects of the filtration module 140, and thus will not be described in detail herein. The filtration module 150 can include one or more high total dissolved solids reverse osmosis (RO) membranes, one or more nanofiltration (NF) membranes, or a combination thereof. For example, in some embodiments, the filtration module 150 can include one or more high total dissolved solids (RO) membranes, such as, for example, polyamide Filmtec TM Fortilife TM XC120 (DuPont), which can operate at total dissolved solids concentrations of up to about 12 wt.%. In some embodiments, the filtration module 150 can include one or more (NF) membranes having a MWCO of about 0.1-1.0 kDa and capable of operating at a pH of 0-14 at temperatures of up to 50 or 60 °C. For example, the filtration module 150 can include one or more (NF) membranes, such as, for example, Kovalus (formerly Koch Separation Solution) SelRO MPS-34 and / or Unisol AMS NanoPro B-4021 membranes. Depending on one or more configurations, the (RO) membranes and / or (NF) membranes can be disposed on the filtration module 150. For example, in some embodiments, the filtration module 150 can include two or more (RO) or (NF) membranes disposed in parallel with one another, as shown in Figure 7The filtration module 150 can receive the permeate 103 and then flow, direct it, and / or bring it into contact with the membrane. Selected species contained in the permeate 103 (e.g., small size monovalent species such as NaOH and a small amount of divalent salt) can be allowed to diffuse through the membrane to produce the permeate 105. Other species present on the permeate 103 (e.g., the remaining organic species, divalent salt (such as Na2S04), and some monovalent salt that managed to diffuse through the graphene oxide membrane of the filtration module 140) can be rejected by the membrane, thereby producing the concentrate 104.

[0085] Figure 11 A plot of flux in gallons per square foot per day (GFD) for a nanofiltration (NF) membrane (Unisol B-4021) and a reverse osmosis (RO) membrane (FilmTec XC120) as a function of concentrate TDS (e.g., the TDS of the concentrate stream produced by the membrane). Figure 11 The (NF) and (RO) membranes exhibit the expected decrease in flux and / or flux reduction as the concentrate TDS increases from 8.5% to about 10.5%. A comparison of the rate of flux reduction for the (NF) and (RO) membranes (e.g., the slope of the (RO) and (NF) curves in Figure 11 Figure 3) indicates that the (NF) membrane can operate at higher concentrate TDS without sacrificing and / or losing as much flux as the (RO) membrane. Thus, in some embodiments, the filtration module 150 can include one or more (NF) membranes, such as those described above.

[0086] In some embodiments, the filtration module 150 can process the permeate 103 in multiple stages as needed, with the concentrate from each stage being fed to the subsequent stage(s). For example, as shown in Figure 1 Figure 4, in some embodiments, the filtration module 150 can include a primary stage 152 and one or more optional secondary stages 153 fluidically coupled to and disposed in series downstream of the primary stage 152. The primary stage 152 and the secondary stages 153 can each include and / or house one or more RO or NF membranes disposed according to any suitable configuration, including, for example, the parallel configuration shown in Figure 7 Figure 3. The primary stage 152 can receive the permeate 103 and then flow, direct it, and / or bring it into contact with the (RO) or (NF) membranes to produce a primary concentrate and a primary permeate. The primary concentrate produced by the primary stage 152 can be fed directly to the secondary stage 153 disposed downstream. The secondary stage 153 can receive the primary concentrate and produce the concentrate 104 and a secondary permeate. The primary and secondary permeates produced in the primary stage 142 and the secondary stage 143, respectively, can be combined to produce the permeate 105 shown in Figure 1 Figure 4. Figure 4.

[0087] As described above with respect to the primary stage 142 and the auxiliary stage 143, the primary stage 152 and the auxiliary stage 153 can each be configured to recirculate a portion and / or fraction of the concentrate product in each stage, as shown in Figure 1 To accomplish this, each stage can be fitted with a recirculation pump (not shown) to enable higher recovery and lower energy consumption of the treatment system 1000.

[0088] The RO or NF membranes in the filtration module 150 enable treatment of the permeate 103 to produce and / or generate (1) a concentrate 104 that primarily contains remaining organic species, divalent salts (such as sodium sulfate (Na2S04)), and some monovalent salts; and (2) a permeate 105 that primarily contains monovalent salts (such as sodium hydroxide (NaOH)) and a small amount of divalent salts. Notably, because the graphene oxide membrane in the filtration module 140 produces a permeate 103 having a lower solids level and a much smaller flow rate than the solids level and flow rate observed for the conditioned feed 101, in some embodiments, the permeate 103 can be cooled (without producing precipitation and / or fouling of the membrane) and then passed to the RO or NF membranes in the filtration module 150 to remove the remaining constituents of the conditioned feed 101. To cool the permeate 103 prior to entry into the filtration module 150, the treatment system 1000 can include one or more heat exchangers (not shown in Figure 1 ) disposed between the filtration modules 140 and 150 (e.g., one or more heat exchangers disposed downstream of the filtration module 140 and upstream of the filtration module 150). These heat exchangers can be configured to receive the permeate 103 and cool and / or adjust the temperature of the permeate 103 to a suitable operating temperature for the filtration membranes included in the filtration module 150. For example, in some embodiments, the permeate 103 can be cooled in the heat exchanger prior to entry into the filtration module 150 such that the RO or NF membranes in the filtration module 150 can operate at a temperature of up to about 50 °C, up to about 46 °C, up to about 42 °C, up to about 38 °C, or up to about 35 °C, including all values and ranges therebetween.

[0089] As described above, in some embodiments, the RO or NF membranes included in the filtration module 150 allow for treatment of the permeate 103 at a temperature of up to about 50 °C to produce and / or generate the permeate 105. The permeate 105 primarily contains monovalent salts such as sodium hydroxide (NaOH) and a small amount of divalent salts. In some embodiments, the permeate 105 can have a total solids concentration of no more than about 2.5 wt.%, no more than about 2.0 wt.%, no more than about 1.5 wt.%, no more than about 1.0 wt.%, or no more than about 0.5 wt.%, including all values and ranges therebetween.

[0090] Combinations of the above-mentioned ranges for the total solids concentration in the permeate 105 are also possible (e.g., at least about 1.0 wt.% to less than about 5.0 wt.%, or at least about 3.5 wt.% to less than about 4.0 wt.%).

[0091] In some embodiments, the RO or NF membranes included in the filtration module 150 can operate at a pressure (e.g., a pumping pressure) of less than about 1100 psi, less than about 1050 psi, less than about 1000 psi, less than about 950 psi, less than about 900 psi, less than about 850 psi, less than about 800 psi, less than about 750 psi, or less than about 700 psi, including all values and ranges therebetween. In some embodiments, the RO or NF membranes included in the filtration module 150 can operate at a pressure (e.g., a pumping pressure) of at least about 700 psi, at least about 800 psi, at least about 900 psi, at least about 1000 psi, or at least about 1100 psi, including all values and ranges therebetween.

[0092] Combinations of the above-mentioned ranges for the operating pressure of the RO or NF membranes in the filtration module 150 are also possible (e.g., a pressure of about 700 psi to about 1100 psi, about 850 psi, and about 1050 psi).

[0093] Figure 1 The treatment system 1000 is shown to also include a filtration module 160. The filtration module 160 can be any suitable filtration device fluidly coupled to the filtration module 150 and configured to receive the permeate 105 and produce a concentrate 106 and a permeate 107. Optionally, in some embodiments, the filtration module 160 can include a storage assembly 161, which can be used to hold and / or store the permeate 105 for a period of time prior to treatment of the permeate 105. The storage assembly 161 can be similar to and / or the same as the storage assemblies 141 and 151 described above with reference to the filtration modules 140 and 150. Accordingly, no further description of the storage assembly 161 will be provided herein.

[0094] The filtration module 160, which can also be referred to herein as a "filtration assembly 160" or a "third filtration module, channel, and / or assembly" of the treatment system 1000, is disposed downstream of the filtration module 150, as shown. The filtration module 160 can be similar to the filtration modules 140 and / or 150 described above. Accordingly, portions and / or aspects of the filtration module 160 can be similar to and / or substantially the same as portions and / or aspects of the filtration modules 140 and 150, and thus will not be described in detail herein. The filtration module 160 includes one or more (RO) membranes, preferably those having high monovalent salt rejection. For example, in some embodiments, the filtration module 160 can include (RO) membranes, such as polyamide FilmTec Figure 1 The treatment system 1000 is shown to also include a filtration module 160. The filtration module 160 can be any suitable filtration device fluidly coupled to the filtration module 150 and configured to receive the permeate 105 and produce a concentrate 106 and a permeate 107. Optionally, in some embodiments, the filtration module 160 can include a storage assembly 161, which can be used to hold and / or store the permeate 105 for a period of time prior to treatment of the permeate 105. The storage assembly 161 can be similar to and / or the same as the storage assemblies 141 and 151 described above with reference to the filtration modules 140 and 150. Accordingly, no further description of the storage assembly 161 will be provided herein.

[0094] The filtration module 160, which can also be referred to herein as a "filtration assembly 160" or a "third filtration module, channel, and / or assembly" of the treatment system 1000, is disposed downstream of the filtration module 150, as shown. The filtration module 160 can be similar to the filtration modules 140 and / or 150 described above. Accordingly, portions and / or aspects of the filtration module 160 can be similar to and / or substantially the same as portions and / or aspects of the filtration modules 140 and 150, and thus will not be described in detail herein. The filtration module 160 includes one or more (RO) membranes, preferably those having high monovalent salt rejection. For example, in some embodiments, the filtration module 160 can include (RO) membranes, such as polyamide FilmTec Figure 1 The treatment system 1000 is shown to also include a filtration module 160. The filtration module 160 can be any suitable filtration device fluidly coupled to the filtration module 150 and configured to receive the permeate 105 and produce a concentrate 106 and a permeate 107. Optionally, in some embodiments, the filtration module 160 can include a storage assembly 161, which can be used to hold and / or store the permeate 105 for a period of time prior to treatment of the permeate 105. The storage assembly 161 can be similar to and / or the same as the storage assemblies 141 and 151 described above with reference to the filtration modules 140 and 150. Accordingly, no further description of the storage assembly 161 will be provided herein.

[0094] The filtration module 160, which can also be referred to herein as a "filtration assembly 160" or a "third filtration module, channel, and / or assembly" of the treatment system 1000, is disposed downstream of the filtration module 150, as shown. The filtration module 160 can be similar to the filtration modules 140 and / or 150 described above. Accordingly, portions and / or aspects of the filtration module 160 can be similar to and / or substantially the same as portions and / or aspects of the filtration modules 140 and 150, and thus will not be described in detail herein. The filtration module 160 includes one or more (RO) membranes, preferably those having high monovalent salt rejection. For example, in some embodiments, the filtration module 160 can include (RO) membranes, such as polyamide FilmTecTM SW30 membrane (DuPont).

[0095] According to one or more configurations, the RO membrane can be disposed on the filtration module 160. For example, in some embodiments, the filtration module 160 may include two or more (RO) membranes disposed parallel to each other, such as Figure 7 107. A filtration module 160 may receive permeate 105 and then flow, direct, and / or contact permeate 105 with a (RO) membrane. Selected species contained in permeate 105 (e.g., small-sized monovalent salts and NaOH) may diffuse through the (RO) membrane to produce permeate 107. Other species present in permeate 105 may be rejected by the (RO) membrane (e.g., some monovalent salts and remaining divalent salts), thereby producing a concentrate 106.

[0096] In some embodiments, the (RO) membrane in the filtration module 160 can operate at temperatures up to about 50°C, up to about 46°C, up to about 42°C, up to about 38°C, or up to about 35°C, including all values ​​and ranges therebetween.

[0097] As described above, in some embodiments, the (RO) membrane included in the filtration module 160 allows the permeate 105 to be processed at temperatures up to about 50° C. to produce and / or generate the permeate 107. The permeate 107 primarily contains small amounts of monovalent salts and NaOH. In some embodiments, the permeate 107 may have a total solids concentration of no more than about 0.5 wt%, no more than about 0.4 wt%, no more than about 0.3 wt%, no more than about 0.2 wt%, no more than about 0.1 wt%, no more than about 0.09 wt%, no more than about 0.08 wt%, no more than about 0.07 wt%, no more than about 0.06 wt%, or no more than about 0.05 wt%, including all values ​​and ranges therebetween.

[0098] Combinations of the above-referenced ranges for total solids concentration in permeate 107 are also possible (eg, at least about 1.0 wt % to less than about 0.4 wt %, or at least about 0.5 wt % to less than about 0.7 wt %).

[0099] The (RO) membrane included in the filtration module 160 can be operated at a pressure similar to the pressure disclosed above for the (RO) membrane included in the filtration module 150. That is, in some embodiments, the (RO) membrane included in the filtration module 160 can be operated at a pressure (e.g., pumping pressure) of less than about 1100 psi, less than about 1050 psi, less than about 1000 psi, less than about 950 psi, less than about 900 psi, less than about 850 psi, less than about 800 psi, less than about 750 psi, or less than about 700 psi, including all values ​​and ranges therebetween. In some embodiments, the (RO) membrane included in the filtration module 160 can be operated at a pressure (e.g., pumping pressure) of at least about 700 psi, at least about 800 psi, at least about 900 psi, at least about 1000 psi, or at least about 1100 psi, including all values ​​and ranges therebetween.

[0100] Combinations of the above-mentioned ranges of operating pressures for the (RO) membranes in the filtration module 160 are also possible (eg, pressures of about 700 psi to about 1100 psi, about 850 psi, and about 1050 psi).

[0101] In some embodiments, permeate 107 may be returned to the mill for reuse in applications such as pulp washing. Alternatively, in other embodiments where further processing may be required (e.g., further reducing the permeate conductivity), permeate 107 may be directed to a filtration module 170, such as Figure 1 Filter module 170, which may also be referred to herein as "filter assembly 170" or "fourth filter module, channel and / or assembly" of treatment system 1000, is disposed downstream of filter module 160, as shown. Figure 1 As shown. Filtration module 170 can be similar to filtration modules 140, 150, and / or 160 described above. Therefore, portions and / or aspects of filtration module 170 can be similar and / or substantially the same as portions and / or aspects of filtration modules 140, 150, and 160 and are therefore not described in detail herein. Filtration module 170 includes one or more (RO) membranes similar to those used in filtration module 160. For example, in some embodiments, filtration module 170 may include a (RO) membrane, such as a polyamide FilmTec TM SW30 membrane (DuPont).

[0102] According to one or more configurations, the (RO) membrane can be disposed on the filtration module 170. For example, in some embodiments, the filtration module 170 may include two or more (RO) membranes disposed parallel to each other, such as Figure 7The filter module 170 can receive the permeate 107 and then flow, direct it, and / or contact it with the (RO) membrane. Selected species contained in the permeate 107, such as trace monovalent salts in amounts similar to those found in evaporator condensate obtained when treating black liquor with existing thermal evaporators, can be allowed to diffuse through the (RO) membrane to produce a process permeate 120. Other species present on the permeate 107 can be rejected by the (RO) membrane, such as monovalent salts, resulting in a concentrate 108. The treated permeate 120 can be sent to and / or returned to the mill for reuse in applications such as pulp washing.

[0103] In some embodiments, the concentrates 102, 104, and 106 can be combined into a treated concentrate 110 that is characterized by a higher total solids concentration relative to the BL feed 100. In some cases, the treated concentrate 110 can be sent to and / or fed to an evaporator of the mill for further concentration. In some embodiments, the concentrate 108 can optionally be returned as a feed to the filter module 160, as shown. Figure 1 Alternatively, in other embodiments, the concentrate 108 can be combined with the concentrates 102, 104, and 106 to produce the treated concentrate 110. In some embodiments, the treated concentrate 110 and the treated permeate 120 can be fed back to a heat exchanger included in the feed preparation assembly 130 to adjust the temperature of the BL feed 100.

[0104] In some embodiments, the (RO) membrane in the filter module 170 can operate at a temperature of up to about 50°C, up to about 46°C, up to about 42°C, up to about 38°C, or up to about 35°C, including all values and ranges therebetween.

[0105] As noted above, in some embodiments, the (RO) membrane included in filtration module 170 allows for treatment of permeate 107 at temperatures up to about 50 °C to produce and / or generate treated permeate 120. Treated permeate 120 consists of trace amounts of monovalent salts in amounts similar to those found in evaporator condensate obtained when treating black liquor with existing thermal evaporators. In some embodiments, treated permeate 120 can have a total solids concentration of no more than about 0.1 wt.%, no more than about 0.09 wt.%, no more than about 0.08 wt.%, no more than about 0.07 wt.%, no more than about 0.06 wt.%, no more than about 0.05 wt.%, no more than about 0.04 wt.%, no more than about 0.03 wt.%, no more than about 0.02 wt.%, no more than about 0.01 wt.%, no more than about 0.009 wt.%, no more than about 0.008 wt.%, no more than about 0.007 wt.%, no more than about 0.006 wt.%, no more than about 0.005 wt.%, no more than about 0.004 wt.%, no more than about 0.003 wt.%, no more than about 0.002 wt.%, or no more than about 0.001 wt.%, including all values and ranges therebetween.

[0106] Combinations of the above-noted ranges for total solids concentration in treated permeate 120 are also possible (e.g., at least about 0.1 wt.% to less than about 0.01 wt.%, or at least about 0.08 wt.% to less than about 0.05 wt.%).

[0107] In some embodiments, the (RO) membrane included in filtration module 170 can operate at a pressure (e.g., a pumping pressure) of less than about 500 psi, less than about 450 psi, less than about 400 psi, less than about 350 psi, less than about 300 psi, less than about 250 psi, or less than about 200 psi, including all values and ranges therebetween. In some embodiments, the (RO) membrane included in filtration module 160 can operate at a pressure (e.g., a pumping pressure) of at least about 200 psi, at least about 300 psi, at least about 400 psi, or at least about 500 psi, including all values and ranges therebetween.

[0108] Combinations of the above-noted ranges for operating pressure of the (RO) membrane in filtration module 170 are also possible (e.g., a pressure of about 200 psi to about 500 psi, about 280 psi, and about 450 psi).

[0109] Figure 12A A table is shown that depicts a comparison of the concentration of species in treated permeate and combined condensate from an evaporator system. Figure 12AIt is shown that treatment of a black liquor stream, such as BL feed 100, can be accomplished using a pressure driven separation system, such as treatment system 1000. Treatment system 1000 can produce a stream, such as treated permeate 120, having a chemical composition similar to that obtained by a thermal evaporator disclosed in the prior art, thereby avoiding the need for a liquid to gas phase transition required in a thermal evaporator and thus enabling cost savings for a plant by reducing energy usage and / or consumption. Figure 12B A summary of the total concentration of solids in the permeate stream produced during operation of treatment system 1000 is provided, providing evidence of removal of a large number of species contained in the black liquor, enabling recycling of water in the plant.

[0110] Figure 13 is a schematic diagram of an exemplary system 2000 for treating a black liquor feed according to one embodiment. System 2000, which can also be referred to herein as "black liquor treatment system 2000" or treatment system 2000" can be configured to receive a black liquor (BL) feed 200 and treat it to produce a treated concentrate 210 and a treated permeate 220 having a set of desired and / or target properties, such as a target conductivity and / or a target TDS. System 2000 includes a feed preparation assembly 230, a filtration module and / or assembly 240, and a filtration module and / or assembly 250. Optionally, in some embodiments, system 2000 can also include a filtration module and / or assembly 260, and storage assemblies 241, 251, and 261 coupled to filtration modules 240, 250, and 260, respectively. Figure 13 It is shown that in some embodiments, filtration module and / or assembly 240 can be configured to receive a feed 200 and produce a permeate 220 and a concentrate 210. Filtration module and / or assembly 240 can be configured to produce a permeate 220 having a target conductivity and / or a target TDS. Filtration module and / or assembly 240 can be configured to produce a concentrate 210 having a target conductivity and / or a target TDS. Filtration module and / or assembly 240 can be configured to produce a permeate 220 having a target conductivity and / or a target TDS, and a concentrate 210 having a target conductivity and / or a target TDS. Figure 1The treatment system 2000 can utilize a reduced number of filtration channels and / or modules (e.g., filtration modules 240 and 250) to produce a treated permeate 220 compared to the treatment system 1000 that includes four filtration channels and / or modules (e.g., filtration modules 140, 150, 160, and 170). In such embodiments, the treatment system 2000 can be designed to operate under different treatment conditions compared to the treatment system 1000. For example, the treatment system 2000 can be designed to operate with a BL feed 200 that has a different composition (e.g., a lower total solids concentration) compared to the BL feed 100. The BL feed 200 can be obtained and / or acquired, for example, from a washer section of a mill. The BL feed 200 obtained from a washer section of a mill can have a total solids concentration that is lower than the typical 10-20 wt.% described above with reference to the BL feed 100. For example, in some embodiments, the BL feed 200 can be any suitable black liquor stream produced in a mill having a total solids concentration (TDS) in a range of about 1 to 9 wt.%. In some embodiments, the treatment system 2000 can be designed to produce a treated permeate 220 that is characterized by a different set of desired and / or target properties than those of the treated permeate 120 described above with reference to the treatment system 1000. For example, the treatment system 2000 can be designed to produce a treated permeate 220 that primarily contains monovalent salts such as sodium hydroxide (NaOH) and a small amount of divalent salts. In some embodiments, the treated permeate 220 can have a total solids concentration of no more than about 4.0 wt.%, no more than about 3.5 wt.%, no more than about 3.0 wt.%, no more than about 2.5 wt.%, no more than about 2.0 wt.%, no more than about 1.5 wt.%, no more than about 1.0 wt.%, no more than about 0.9 wt.%, no more than about 0.8 wt.%, no more than about 0.7 wt.%, no more than about 0.6 wt.%, no more than about 0.5 wt.%, no more than about 0.4 wt.%, no more than about 0.3 wt.%, no more than about 0.2 wt.%, or no more than about 0.1 wt.%, including all values and ranges therebetween. In some embodiments, the treatment system 2000 can be designed such that the filtration modules 240 and 250 produce permeates (e.g., permeates 203 and 220) having a set of desired and / or target properties that are defined by their color rather than their conductivity, as in the treatment system 1000. For example, in some embodiments, the treatment system 2000 can be designed to produce one or more permeate streams that are visually clear when viewed through a pre-determined sized container (e.g., a 1-20 mL vial). As Figure 13As shown, in some embodiments, the treatment system 2000 can include an optional filtration pass and / or module 260. In such embodiments, the treatment system 2000 can be designed to operate in a BL feed 200 (e.g., a BL feed having a total solids concentration in the range of 10 to 20 wt.%) similar and / or the same as the BL feed 100, and produce a treated permeate 220 having similar and / or the same characteristics as the treated permeate 120 described above with reference to the treatment system 100. Figure 1 The treated permeate 120 described above with reference to the treatment system 100. More specifically, in those embodiments, the treatment system 2000 can include a feed preparation assembly 230 that includes one or more ceramic membranes having a relatively small pore size separation medium (e.g., about 1 kDa to about 10 pm), as described above with reference to the feed preparation assembly 130. The ceramic membranes can be any suitable shape / form (e.g., tubular and / or planar or flat sheet), and include single pass and / or multi-pass geometries. The feed preparation assembly 230 produces an adjusted feed 201, which can be further processed through the filtration passes and / or modules 240, 250, and 260 to produce a treated concentrate 210 and a treated permeate 220. In some embodiments, the treatment system 2000 can be designed to operate such that one or more concentrate streams produced in the filtration modules 240, 250, and 260 are not combined to produce the treated concentrate 210, as described above with reference to the treatment system 100. Figure 13 As shown, in some embodiments, the treatment system 2000 can be configured to divert the concentrate 204 and the concentrate 206 produced in the filtration modules 250 and 260, respectively, to different processes, and produce the treated concentrate 210 directly from the filtration module 240 (e.g., from the concentrate 202).

[0111] Returning to Figure 13feed preparation assembly 130 described above with reference to system 1000. Accordingly, portions and / or aspects of feed preparation assembly 230 that are similar and / or substantially identical to portions and / or aspects of feed preparation assembly 130 are not described in detail herein. Feed preparation assembly 230 can receive black liquor (BL) feed 200, perform one or more preparation and / or conditioning steps, and produce conditioned (Cond) feed 201. In some embodiments, BL feed 200 can be any suitable black liquor stream produced in a mill having a total solids concentration in the range of about 10 to 20 wt.%. Alternatively, in some embodiments, BL feed 200 can be any suitable black liquor stream produced in a mill having a total solids concentration in the range of about 1 to 9 wt.%. Feed preparation assembly 230 can remove material suspended on BL feed 200, including a portion (or all) of large size organic species classes produced during the pulping process and / or dissolved in BL feed 200. For example, in some embodiments, feed preparation assembly 230 can be configured to remove a majority of residual fibers and other suspended material present in BL feed 200. In other embodiments, feed preparation assembly 230 can be configured to remove a majority of residual fibers and other suspended material, as well as a portion of large size organic species classes dissolved in BL feed 200 (e.g., hemicellulose, cellulose, lignin, etc.). In some embodiments, feed preparation assembly 230 can be configured to remove a certain percentage of large size organic species classes dissolved in BL feed 100, including, for example, about 10%, about 15%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about 90%, or about 100%, including all values and ranges therebetween. In some embodiments, feed preparation assembly 230 can include one or more heat exchangers (not shown in FIG. 2) that can be used to adjust conditioned feed 201 to a predetermined temperature. Conditioned feed 201 can then be directed and / or flowed to filtration module 240 for further processing at the predetermined temperature until treated concentrate 210 and treated permeate 220 are produced, as described further herein. Optionally, in some embodiments, conditioned feed 201 can be stored in storage compartment 241 prior to being directed to filtration module 240. Figure 13

[0112] ​The feed preparation assembly 230 includes one or more tubular ceramic membranes having a single-pass and / or multi-pass geometry and comprising separation media having an average pore size of about 1 kDa to about 10 pm. The tubular ceramic membranes can be configured to have an average pore size that is smaller than the average size of the fibers and other materials suspended on the BL feed 200, such that the tubular ceramic membranes prevent those materials from passing through (e.g., the tubular ceramic membranes repel the residual fiber and other material suspended materials). Additionally, the average pore size of the tubular ceramic membranes can also facilitate the removal and / or rejection of a portion of the large size dissolved organic species (e.g., hemicellulose, cellulose, lignin, etc.). For example, in some embodiments, the tubular ceramic membranes can remove and / or reject about 10%, about 15%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about 90%, or about 100% of the large size organic species dissolved in the BL feed 200, including all values and ranges therebetween.

[0113] The feed preparation assembly 230 includes one or more tubular ceramic membranes having a single-pass and / or multi-pass geometry and comprising separation media having an average pore size of about 1 kDa to about 10 pm. The tubular ceramic membranes can be configured to have an average pore size that is smaller than the average size of the fibers and other materials suspended on the BL feed 200, such that the tubular ceramic membranes prevent those materials from passing through (e.g., the tubular ceramic membranes repel the residual fiber and other material suspended materials). Additionally, the average pore size of the tubular ceramic membranes can also facilitate the removal and / or rejection of a portion of the large size dissolved organic species (e.g., hemicellulose, cellulose, lignin, etc.). For example, in some embodiments, the tubular ceramic membranes can remove and / or reject about 10%, about 15%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about 90%, or about 100% of the large size organic species dissolved in the BL feed 200, including all values and ranges therebetween.

[0114] The feed preparation assembly 230 can receive the BL feed 200 and produce a conditioned (Cond) feed 201 having a predetermined temperature and a predetermined TDS. For example, in some embodiments, the feed preparation assembly 230 can produce a conditioned feed 201 having a predetermined temperature and a predetermined and / or target TDS of about 4 to about 18 wt.%. The conditioned feed 201 can then be conveyed and / or flowed to the first pass and / or filtration module 240, as further described herein.

[0115] The filtration module 240 can be similar to the filtration module 140 described above with reference to the system 1000. Accordingly, portions and / or aspects of the filtration module 240 that are similar and / or substantially identical to portions and / or aspects of the filtration module 140 are not described in detail herein. The filtration module 240 can be any suitable filtration device fluidly coupled to the feed preparation assembly 230 and configured to receive the conditioned feed 201 at the predetermined temperature and TDS, perform one or more separation steps, and produce a concentrate 202 and a permeate 203. Optionally, in some embodiments, the filtration module 240 can include a storage assembly 241, which can be used to house and / or store the conditioned feed 201 for a period of time prior to its processing. The storage assembly 241 can include and / or be one or more tanks having any suitable shape, size, and / or capacity. The storage assembly 241 can include one or more valves, inlets, or ports (not shown) configured to allow liquid to flow into or out of the tanks of the storage assembly 241 (e.g., to at least partially fill one or more of the tanks, collect a sample for quality control purposes, etc.).

[0116] Filtration module 240, which may also be referred to herein as "filtration component 240" or "first filtration module, channel and / or component" of processing system 2000, is positioned downstream of feed preparation component 230, as shown in FIG. Figure 7 As shown. The filter module 240 includes one or more graphene oxide membranes. According to one or more configurations, the graphene oxide membrane can be disposed on the filter module 240. For example, in some embodiments, the filter module 240 can include two or more graphene oxide membranes disposed parallel to each other, such as Figure 10A 201. The filtration module 240 may receive a conditioned feed 201 at a predetermined temperature and then flow, direct, and / or contact the conditioned feed 201 with a graphene oxide membrane contained within the filtration module 240. Selected species included in the conditioned feed 201 may be allowed to diffuse through the graphene oxide membrane to produce a permeate fluid, such as permeate 203. Other species present on the conditioned feed 201 may be repelled by the graphene oxide membrane (e.g., prevented from diffusing through the graphene oxide membrane) and thereby produce a concentrate fluid, such as concentrate 202.

[0117] In some embodiments, the graphene oxide membrane can be disposed and / or coated on a support substrate configured to provide mechanical and / or thermal stability to the graphene oxide membrane. The support substrate can include a plurality of flat polymer sheets that are combined to form a spiral filtration configuration. In some embodiments, the support substrate can be and / or include a nanofiltration (NF) membrane exhibiting similar and / or identical properties to the (NF) membranes described above with reference to filtration module 150. For example, in some embodiments, the (NF) membrane used as a support for the graphene oxide membrane can exhibit a MWCO of about 0.1-1.0 kDa, and be capable of operating at a temperature of up to 50 or 60 °C at a pH of 0-14. In some embodiments, the support substrate can be and / or include an ultrafiltration (UF) membrane. For example, in some embodiments, the support substrate can be and / or include an ultrafiltration (UF) membrane, such as a polyethersulfone (PES, UP010P Mann+Hummel) membrane having a molecular weight cut-off (MWCO) of about 10 kDa. In preferred embodiments, the graphene oxide membrane can be disposed on a support comprising a nanofiltration (NF) membrane, such as a Kovalus (formerly Koch Separation Solutions) SelRO MPS-34 and / or Unisol AMS NanoPro B-4021 membrane. A graphene oxide membrane coated on a nanofiltration (NF) membrane used as a support can be referred to herein as a GO / NF membrane. In other embodiments, the support substrate can be and / or include a reverse osmosis (RO) membrane exhibiting similar and / or identical properties to the (RO) membranes described above with reference to filtration module 150. For example, in some embodiments, the (RO) membrane used as a support for the graphene oxide membrane can be and / or include a high total dissolved solids RO membrane, such as a polyamide FilmTec TM Fortilife TM XC120 (DuPont), which can operate at a total dissolved solids concentration of up to about 12 wt.%. A graphene oxide membrane coated on a RO membrane used as a support can be referred to herein as a GO / RO membrane.

[0118] The GO / NF and GO / RO membranes in the filtration module 240 can enable and / or facilitate the processing of black liquor (e.g., conditioned feed 201) at a temperature between about 60-90°C and an elevated pH of about 11-13 to produce and / or generate (1) a concentrate 202 containing primarily organic species such as lignin and hemicellulose, and (2) a permeate 203 containing primarily monovalent and divalent inorganic salts and minor amounts of organic species. In some embodiments, disposing and / or coating a graphene oxide (GO) membrane on a nanofiltration (NF) membrane serving as a support can produce a GO / NF membrane that exhibits sufficient thermal, mechanical, and chemical stability to operate at the elevated temperatures and elevated pH of the conditioned feed 201. Similarly, in some embodiments, disposing and / or coating a graphene oxide (GO) membrane on a reverse osmosis (RO) membrane serving as a support can produce a GO / RO membrane that exhibits sufficient thermal, mechanical, and chemical stability to operate at the elevated temperatures and elevated pH of the conditioned feed 201. The ability to operate at such high temperatures and elevated pH stems from the properties that the graphene oxide membrane imparts to GO / NF and / or

[0119] Thermal and chemical stability of GO / RO membranes. In some embodiments, the filtration module 240

[0120] The long-term durability of the GO / NF membranes and GO / RO membranes can be affected and / or caused to be affected by the selection of the particular nanofiltration (NF) membrane and / or reverse osmosis (RO) membrane. In other words, the specific properties of the nanofiltration (NF) membrane and / or reverse osmosis (RO) membrane selected for use as a support for the GO / NF membrane and / or GO / RO membrane can enable the filtration module 240 to operate continuously without exhibiting the degradation exhibited by the nanofiltration (NF) membrane and / or reverse osmosis (RO) membrane, for example, Figure 13 As shown, the integration of GO / NF membranes and / or GO / RO membranes with treatment system 2000 provides a method for concentrating a black liquor stream using pressure-driven membranes, separating most of the large organic species present in the black liquor in the first filtration module (e.g., filtration module 240). This is a result that cannot be achieved using conventional membranes disclosed in the prior art.

[0121] In some embodiments, the filtration module 240 may process the conditioned feed 201 in multiple stages as needed, with the concentrate from each stage being fed to the subsequent stage(s). Figure 7As shown, in some embodiments, the filtration module 240 may include a main stage 242 and one or more optional auxiliary stages 243, wherein the one or more optional auxiliary stages 2430 are fluidly coupled to the main stage 242 and arranged in series downstream of the main stage 242. The main stage 242 and the auxiliary stage 243 may each include and / or house one or more filtration stages according to any suitable configuration, including, for example, Figure 13 The main stage 242 may receive the conditioned feed 201 and then flow, guide and / or contact the conditioned feed 201 with a graphene oxide membrane supported on a nanofiltration membrane (e.g., a GO / NF membrane) or a reverse osmosis membrane (GO / RO membrane) used as a support to produce a main concentrate and a main permeate. The main concentrate produced by the main stage 242 may be directly fed to the auxiliary stage 243 provided downstream. The auxiliary stage 243 may receive the main concentrate and produce a concentrate 202 and an auxiliary permeate. The main and auxiliary permeates produced in the main stage 242 and the secondary stage 243, respectively, may be combined to produce Figure 13 Permeate 203 is shown.

[0122] In some embodiments, the main stage 242 and auxiliary stage 243 may each be configured to recirculate a portion and / or fraction of the concentrate product in each stage, e.g. Figure 14 As shown. To achieve this, each stage can be equipped with a recirculation pump (not shown) to enable higher recovery rates and lower energy consumption of the treatment system 2000. More specifically, recycling a portion of the concentrate produced in a stage to the feed of that stage allows the earlier stages (e.g., the main stage 242 and those auxiliary stages 243 located downstream near the main stage 242) to operate at lower solids than the final auxiliary stage 243 (e.g., the auxiliary stage 243 located further downstream from the main stage 242). This improves flux and prevents membrane fouling by reducing the osmotic pressure of the conditioning feed 201.

[0123] Figure 14 The performance of an exemplary filtration module 240 operating on a conditioned feed 201 to produce a permeate 203 is shown, recorded at an operating temperature of 35°C and a pressure of 750 psi. More specifically, Figure 14 Graphs are shown of flux in gallons per square foot per day (GFD), permeate conductivity (mS / cm), and permeate refractive index (Brix) as a function of total dissolved solids (TDS) of black liquor (BL) feed, produced by graphene oxide membranes coated on nanofiltration membranes used as supports (e.g., GO / NF membranes) and graphene oxide membranes coated on reverse osmosis membranes used as supports (e.g., GO / RO membranes). Notably, Figure 14 The BL feed in is produced by treating and / or conditioning black liquor using a feed preparation assembly 230 comprising a tubular ceramic membrane having an average pore size of about 15 kDa.Figure 13 The GO / NF and GO / RO membranes were shown to be able to treat BL feed 201 having a wide range of total dissolved solids between about 10% to 13%, producing permeate with high flux and high rejection rates.

[0124] In some embodiments, the graphene oxide membranes included in the filtration module 240 (e.g., GO / NF membranes and / or GO / RO membranes) can exhibit a total solids rejection rate of at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, or at least about 95%, including all values and ranges therebetween, at an operating temperature of about 60-90 °C. In some embodiments, the graphene oxide membranes included in the filtration module 240 can exhibit a total solids rejection rate of no more than about 94%, no more than about 88%, no more than about 84%, no more than about 80%, no more than about 76%, no more than about 72%, no more than about 68%, no more than about 64%, no more than about 60%, no more than about 56%, no more than about 52%, no more than about 48%, or no more than about 44%, including all values and ranges therebetween.

[0125] Combinations of the above-mentioned ranges for total solids rejection rate of the graphene oxide membranes are also possible (e.g., at least about 60% less than about 90% or at least about 68% to less than about 80%).

[0126] In some embodiments, the graphene oxide membrane included in the filtration module 240 (e.g., a GO / RO membrane and / or a GO / NF membrane) can withstand an osmotic pressure of less than about 800 psi, less than about 750 psi, less than about 700 psi, less than about 650 psi, less than about 600 psi, less than about 550 psi, less than about 500 psi, less than about 480 psi, less than about 460 psi, less than about 440 psi, less than about 420 psi, less than about 400 psi, less than about 380 psi, less than about 360 psi, less than about 320 psi, less than about 300 psi, less than about 280 psi, less than about 260 psi, less than about 220 psi, less than about 200 psi, less than about 180 psi, less than about 160 psi, less than about 140 psi, less than about 120 psi, less than about 100 psi, less than about 80, less than about 70 psi, less than about 60 psi, or less than about 50 psi, including all values ​​and ranges therebetween. In some embodiments, the graphene oxide membrane included in the filtration module 240 can withstand an osmotic pressure of at least about 50 psi, at least about 75 psi, at least about 100 psi, at least about 125 psi, at least about 150 psi, at least about 175 psi, at least about 200 psi, at least about 250 psi, at least about 300 psi, at least about 350 psi, at least about 400 psi, at least about 450 psi, at least about 500 psi, at least about 550 psi, at least about 600 psi, at least about 650 psi, at least about 700 psi, at least about 750 psi, or at least about 800 psi, including all values ​​and ranges therebetween.

[0127] Combinations of the above-mentioned ranges of osmotic pressures to which the graphene oxide membrane in the filtration module 240 is subjected are also possible (e.g., about 200 psi to about 750 psi, about 250 psi, and about 100 psi).

[0128] 480 psi osmotic pressure). Notably, in some embodiments, the conditioned feed 201 can be directed and / or flowed to the filtration module 240 at pumping pressure. In some embodiments, the osmotic pressure of the conditioned feed 201 in the filtration module 240 can be a percentage of the pumping pressure. For example, in some embodiments, the osmotic pressure of the conditioned feed 201 can be about 50% or less, about 45% or less, about 40% or less, about 35% or less, or about 30% or less of the pumping pressure. The osmotic pressure is less than the pumping pressure to allow for some overpressure to drive flux and transport.

[0129] Back to Figure 13The treatment system 2000 also includes a filtration module 250. The filtration module 250 can be any suitable filtration device fluidly coupled to the filtration module 240 and configured to receive the permeate 203 and produce a concentrate 204 and a treated permeate 220. Optionally, in some embodiments, the filtration module 250 can include a storage assembly 251 that can be used to hold and / or store the permeate 203 for a period of time prior to treatment of the permeate 203. The storage assembly 251 can be similar to and / or the same as the storage assembly 241 described above with reference to the filtration module 240. Accordingly, no further description of the storage assembly 251 will be provided herein.

[0130] The filtration module 250, which can also be referred to herein as a "filtration assembly 250" or a "second filtration module, channel, and / or assembly" of the treatment system 2000, is disposed downstream of the filtration module 240, as shown in Figure 7 The filtration module 250 can include one or more reverse osmosis (RO) membranes, one or more nanofiltration (NF) membranes, or a combination thereof. For example, in some embodiments, the filtration module 250 can include one or more high total dissolved solids (TDS) RO membranes, such as FilmTec TM Fortilife TM XC120 (DuPont), which can operate at a maximum of about 12 wt% total dissolved solids concentration. In some embodiments, the filtration module 250 can include one or more reverse osmosis (RO) membranes, such as FilmTec TM SW30 membranes (DuPont). In some embodiments, the filtration module 250 can include one or more (NF) membranes having a MWCO of about 0.1-1.0 kDa and capable of operating at a pH of 0-14 at temperatures up to 50 or 60 °C. For example, the filtration module 250 can include one or more (NF) membranes, such as Kovalus (formerly Koch Separation Solutions) SelRO MPS-34 and / or Unisol AMS NanoPro B-4021 membranes. Depending on one or more configurations, the (RO) membranes and / or (NF) membranes can be disposed on the filtration module 250. For example, in some embodiments, the filtration module 250 can include two or more (RO) or (NF) membranes disposed in parallel with one another, such as Figure 132. Filtration module 250 may receive permeate 203 and then flow, direct, and / or contact permeate 203 with a membrane. Selected species contained in permeate 203 (e.g., some small-sized monovalent species (e.g., NaOH) and small amounts of divalent salts) may be caused to diffuse through the membrane to produce treated permeate 220. Other species present on permeate 103 (e.g., remaining organic species that manage to diffuse through the graphene oxide membrane of filtration module 240, divalent salts such as Na2SO4, and some monovalent salts) may be rejected by the membrane to produce concentrate 204.

[0131] In some embodiments, the filtration module 250 may process the permeate 203 in multiple stages as desired, with the concentrate from each stage being fed to the subsequent stage(s). Figure 7 As shown, in some embodiments, the filter module 250 may include a primary

[0132] 252 and one or more optional auxiliary stages 253, which are fluidly coupled to the main stage

[0133] 252 and are arranged in series downstream of the main stage 252. The main stage 252 and the auxiliary stage 253 may each include and / or house one or more (RO) or (NF) membranes arranged according to any suitable configuration, including, for example Figure 13 The primary stage 252 may receive the permeate 203 and then flow, direct, and / or contact the permeate 203 with a (RO) and / or (NF) membrane to produce a primary concentrate and a primary permeate. The primary concentrate produced by the primary stage 252 may be fed directly to the secondary stage 253 disposed downstream. The secondary stage 253 may receive the primary concentrate and produce a concentrate 204 and a secondary permeate. The primary and secondary permeates produced in the primary stage 242 and the secondary stage 243, respectively, may be combined to produce a primary concentrate. Figure 13 Treated permeate 220 is shown.

[0134] As described above with respect to the main stage 242 and the auxiliary stage 243, the main stage 252 and the auxiliary stage 253 can each be configured to recycle a portion and / or fraction of the concentrate produced in each stage, such as Figure 13 To achieve this, each stage may be equipped with a recirculation pump (not shown) to enable higher recovery rates and lower energy consumption of the treatment system 2000.

[0135] The RO or NF membranes in the filtration module 250 enable the permeate 203 to be processed to produce and / or generate (1) a concentrate 204 containing primarily residual organic species, divalent salts such as sodium sulfate (Na2SO4) and some monovalent salts; and (2) a permeate 220 containing primarily monovalent salts such as sodium hydroxide (NaOH) and a small amount of divalent salts. Notably, because the graphene oxide membranes in the filtration module 240 produce a permeate 203 having a lower solids level and a much smaller flow rate than those observed for the conditioned feed 201, in some embodiments, the permeate 203 can be cooled (without precipitation and / or fouling of the membrane) and then passed to the RO or NF membranes in the filtration module 250 to remove the remaining components of the conditioned feed 201. To cool the permeate 203 before it enters the filtration module 250, the treatment system 2000 may include one or more heat exchangers ( Figure 13 140 and upstream of filtration module 150). These heat exchangers can be configured to receive permeate 203 and cool and / or adjust the temperature of permeate 203 to a suitable operating temperature for the filtration membranes included in filtration module 250. For example, in some embodiments, permeate 203 can be cooled in a heat exchanger before entering filtration module 250 so that the RO or NF membranes in filtration module 250 can operate at temperatures up to about 50° C., up to about 46° C., up to about 42° C., up to about 38° C., or up to about 35° C., including all values ​​and ranges therebetween.

[0136] As described above, in some embodiments, the RO or NF membrane included in the filtration module 250 allows the permeate 203 to be treated at temperatures up to about 50° C. to produce and / or generate the treated permeate 220. The treated permeate 220 contains primarily monovalent salts such as sodium hydroxide (NaOH) and small amounts of divalent salts. In some embodiments, the treated permeate 220 may have a total solids concentration of no more than about 4.0 wt%, no more than about 3.5 wt%, no more than about 3.0 wt%, no more than about 2.5 wt%, no more than about 2.0 wt%, no more than about 1.5 wt%, no more than about 1.0 wt%, no more than about 0.9 wt%, no more than about 0.8 wt%, no more than about 0.7 wt%, no more than about 0.6 wt%, no more than about 0.5 wt%, no more than about 0.4 wt%, no more than about 0.3 wt%, no more than about 0.2 wt%, or no more than about 0.1 wt%, including all values ​​and ranges therebetween.

[0137] Combinations of the above-mentioned ranges for the total solids concentration in the treated permeate 220 are also possible (e.g., at least about 0.1 wt.% to less than about 1.0 wt.%, or at least about 0.5 wt.% to less than about 0.8 wt.%).

[0138] In some embodiments, the RO or NF membranes included in the filtration module 250 can operate at a pressure (e.g., a pumping pressure) of less than about 1100 psi, less than about 1050 psi, less than about 1000 psi, less than about 950 psi, less than about 900 psi, less than about 850 psi, less than about 800 psi, less than about 750 psi, or less than about 700 psi, including all values and ranges therebetween. In some embodiments, the RO or NF membranes included in the filtration module 250 can operate at a pressure (e.g., a pumping pressure) of at least about 700 psi, at least about 800 psi, at least about 900 psi, at least about 1000 psi, or at least about 1100 psi, including all values and ranges therebetween.

[0139] Combinations of the above-mentioned ranges for the operating pressure of the RO or NF membranes in the filtration module 250 are also possible (e.g., a pressure of about 700 psi to about 1100 psi, about 850 psi, and about 1050 psi).

[0140] Figure 13 It is shown that the treatment system 2000 can optionally include a filtration module 260. In such embodiments, the filtration module 260 can be any suitable filtration device fluidly coupled to the filtration module 250 (e.g., downstream of the filtration device 250) and configured to receive the optional permeate 205 and produce a concentrate 206 and a treated permeate 220. In some embodiments, the filtration module 260 can include a storage assembly 261, which can be used to house and / or store the permeate 205 for a period of time prior to treatment of the permeate 205. The storage assembly 261 can be similar to and / or the same as the storage assemblies 241 and 251 described above with reference to the filtration modules 240 and 250. Accordingly, no further description of the storage assembly 261 will be provided herein.

[0141] The filtration module 260, which can also be referred to herein as the “filtration assembly 260” or the “third filtration module, channel, and / or assembly” of the treatment system 2000, can be disposed downstream of the filtration module 250, as shown in FIG. 2, and / or upstream of the filtration module 250, as shown in FIG. 3. Figure 7The filtration module 260 can be similar to the filtration modules 240 and / or 250 described above. Thus, portions and / or aspects of the filtration module 260 can be similar and / or substantially identical to portions and / or aspects of the filtration modules 240 and 250, and thus are not described in detail herein. The filtration module 260 includes one or more (RO) membranes, preferably those having high monovalent salt rejection. For example, in some embodiments, the filtration module 260 can include (RO) membranes such as the SW30 membranes (DuPont) and / or the SW30HR-LE membranes (DuPont). TM SW30 membranes (DuPont).

[0142] According to one or more configurations, the (RO) membranes can be disposed on the filtration module 260. For example, in some embodiments, the filtration module 260 can include two or more (RO) membranes disposed parallel to one another, such as the SW30 membranes (DuPont) and / or the SW30HR-LE membranes (DuPont). Figure 13 The filtration module 260 can receive the permeate 205 and then flow, direct, and / or contact it with the (RO) membranes. Selected species contained in the permeate 205 (e.g., small-sized monovalent salts and NaOH) can be diffused through the (RO) membranes to produce a treated permeate 220. Other species present on the permeate 205 can be rejected by the (RO) membranes (e.g., some monovalent salts and remaining divalent salts), thereby producing a concentrate 206. In some embodiments, the concentrate 206 can be combined with the concentrates 204 and 202 to produce a treated concentrate 210, as shown in FIG. 2B. Figure 16

[0143] In some embodiments, the (RO) membranes in the filtration module 260 can operate at temperatures up to about 50°C, up to about 46°C, up to about 42°C, up to about 38°C, or up to about 35°C, including all values and ranges therebetween.

[0144] The (RO) membranes included in the filtration module 260 can operate at similar pressures to those disclosed above with respect to the (RO) membranes included in the filtration module 250. That is, in some embodiments, the (RO) membranes included in the filtration module 260 can operate at a pressure (e.g., a pumping pressure) of less than about 1100 psi, less than about 1050 psi, less than about 1000 psi, less than about 950 psi, less than about 900 psi, less than about 850 psi, less than about 800 psi, less than about 750 psi, or less than about 700 psi, including all values and ranges therebetween. In some embodiments, the (RO) membranes included in the filtration module 260 can operate at a pressure (e.g., a pumping pressure) of at least about 700 psi, at least about 800 psi, at least about 900 psi, at least about 1000 psi, or at least about 1100 psi, including all values and ranges therebetween.

[0145] ​Combinations of the above-mentioned ranges for the operating pressure of the (RO) membranes in the filtration modules 260 are also possible (e.g., pressures of about 700 psi to about 1100 psi, about 850 psi, and about 1050 psi).

[0146] As described above, the treatment system 2000 includes a reduced number of filtration pathways and / or filtration modules as compared to the treatment system 1000. In some embodiments, the filtration modules 240, 250, and 260 of the treatment system 2000 can include a combination of graphene oxide (GO) membranes, nanofiltration (NF) membranes, and reverse osmosis (RO) membranes, as summarized in Table 2. ​

[0147] While the present teachings have been described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments or examples. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those of ordinary skill in the art.

[0148] While various inventive embodiments have been described and illustrated herein, it will be appreciated that various modifications are possible within the scope of the inventive embodiments without materially departing from the invention. More generally, the present teachings are applicable to any liquid filtration system that includes a plurality of filtration modules, each filtration module including a plurality of filtration pathways. Accordingly, all matter contained herein should be interpreted as illustrative only and not limiting as to the scope and spirit of the inventive embodiments. Accordingly, while the inventive embodiments have been described with reference to particular embodiments, it will be understood that various modifications can be made both to the details of the inventive embodiments and to the overall systems and methods described herein, and that such modifications are intended to be within the scope of the inventive embodiments. The inventive embodiments relate to each individual feature, system, article, material, kit, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and / or methods, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.

[0149] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.

[0150] The indefinite articles "a" and "an," as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean "at least one." Any range of values, when recited, is inclusive of the ends of the range.

[0151] ​As used in this specification and claims, the terms "substantially," "approximately," and "about" generally refer to plus or minus 10% of the stated value, eg, approximately 100 includes 90 to 110.

[0152] The phrases “and / or” used in the specification and claims should be understood to mean “either or both” of the elements so combined, i.e., elements present in combination in some cases and separately in other cases. Multiple elements listed with “and / or” should be interpreted in the same manner, i.e., “one or more” of the elements so combined. In addition to the elements specifically identified by the “and / or” clause, other elements may optionally be present, whether related or unrelated to those specifically identified. Thus, as a non-limiting example, a reference to “A and / or B,” when used in conjunction with open language such as “comprising,” may refer to only A (optionally including elements other than B) in one embodiment; only B (optionally including elements other than A) in another embodiment; and both A and B (optionally including other elements) in another embodiment; and so on.

[0153] As used in the specification and claims, "or" shall be understood to have the same meaning as "and / or" as defined above. For example, when separating items in a list, "or" or "and / or" shall be interpreted as inclusive, i.e., including at least one of a plurality or series of elements, but also including more than one, and optionally, additional unlisted items. Only terms that clearly indicate the contrary, such as "only one" or "exactly one", or when used in the claims, "consisting of" will refer to including a plurality of elements or exactly one element of a list of elements. In general, when the term "or" is preceded by an exclusive term, such as "either", "one of", "only one of", or "exactly one of", the term "or" as used herein shall only be interpreted to indicate exclusive alternatives (i.e., "one or the other, but not both"). When used in the claims, "consisting essentially of" shall have its ordinary meaning as used in the art of patent law.

[0154] As used in the specification and claims, the phrase "at least one" with respect to a list of one or more elements should be understood to mean at least one element selected from any one or more elements in the list of elements, but not necessarily including at least one of every element specifically listed in the list of elements, and not excluding any combination of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified in the list of elements to which the phrase "at least one" refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, "at least one of A and B" (or equivalently,

[0155] "At least one of A or B," or equivalently, "at least one of A and / or B") may refer in one embodiment to at least one, optionally including more than one A, with no B (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A (and optionally including elements other than A); in yet another embodiment, to at least one A, optionally including more than one A, and at least one B, optionally including more than one B (and optionally including other elements); and so on.

[0156] In the claims and the preceding description, all transitional phrases such as "comprises," "comprising," "with," "having," "containing," "involving," "having," "consisting of," and the like are to be construed as open-ended, meaning including but not limited to. As provided in Section 2111.03 of the U.S. Patent Office Manual of Patent Examining Procedures, only the transitional phrases "consisting of" and "consisting essentially of" are to be considered closed or semi-closed transitional phrases, respectively.

[0157] As used herein, the term "room temperature" may refer to a temperature of about 15°C, about 16°C, about 17°C, about 18°C, about 19°C, about 20°C, about 21°C, about 22°C, about 23°C, about 24°C, or about 25°C. In some embodiments, room temperature is about 20°C.

[0158] As used herein, the term "substantially the same" means that a first value is within 10% of a second value. For example, if A is substantially the same as B, and B is 100, then A can have a value in the range of 90 to 110. If A is substantially the same as B, and B is 200, then A can have a value in the range of 180 to 220.

[0159] The claims should not be construed as limited to the described order or elements unless stated to that effect. However, it should be understood that various changes in form and details may be made by one skilled in the art without departing from the spirit and scope of the appended claims. Protection is claimed for all embodiments that come within the spirit and scope of the appended claims and their equivalents.

Claims

1. A system comprising: a feed preparation assembly configured to receive a black liquor feed having an initial total concentration of dissolved solids and suspended solids, the feed preparation assembly further configured to remove a portion of the suspended solids from the black liquor feed to produce a conditioned feed; a first filtration module comprising an oxidized graphene membrane, the first filtration module fluidly coupled to the feed preparation assembly and configured to contact the conditioned feed with the oxidized graphene membrane at a predetermined temperature to produce a first concentrate and a first permeate; a second filtration module fluidly coupled to the first filtration module, the second filtration module configured to receive the first permeate and produce a second concentrate and a second permeate; a third filtration module fluidly coupled to the second filtration module, the third filtration module configured to receive the second permeate and produce a third concentrate and a third permeate; and a fourth filtration module disposed downstream of the third filtration module, the fourth filtration module configured to receive the third permeate and produce a treated permeate, wherein the first concentrate, the second concentrate, and the third concentrate are combined to produce a treated concentrate having a total concentration of solids that is higher than the initial total concentration of solids.

2. The system of claim 1, wherein the feed preparation assembly is further configured to remove a portion of the dissolved solids from the black liquor feed to produce the conditioned feed.

3. The system of claim 1, wherein the initial total concentration of dissolved solids and suspended solids is between about 10 wt% and 15 wt%, and the oxidized graphene membrane produces the first permeate having a total concentration of solids that is no more than about 9 wt%.

4. The system of any one of claims 1-3, wherein the oxidized graphene membrane produces the first concentrate having a total concentration of solids that is at least about 18 wt%.

5. The system of any one of claims 1-4, wherein the predetermined temperature is at least about 70 °C.

6. The system of claim 5, wherein the oxidized graphene membrane has a total solids rejection rate of at least about 50% at the predetermined temperature and a pressure of no more than 800 psi.

7. The system of claim 1, wherein the first filtration module further comprises a primary stage housing the oxidized graphene membrane, the primary stage configured to recycle a portion of the first concentrate to the conditioned feed.

8. The system of claim 1, wherein the first filtration module further comprises: a primary stage housing a first oxidized graphene membrane, the primary stage configured to (1) contact the conditioned feed with the first oxidized graphene membrane to produce an intermediate concentrate, and (2) recycle a portion of the intermediate concentrate to the conditioned feed; and a secondary stage housing a second oxidized graphene membrane, the secondary stage disposed downstream of the primary stage and configured to contact the intermediate concentrate with the second oxidized graphene membrane to produce the first concentrate. the secondary stage configured to recycle a portion of the first concentrate to the intermediate concentrate.

10. The system of any one of claims 1-9, wherein the feed preparation assembly comprises one or more tubular ceramic membranes.

9. The system of claim 8, wherein, ​ ​ 11. The system of claim 1, wherein the second filtration module further comprises: a primary stage housing a first polymer membrane, the first stage of the second filtration module configured to (1) contact a first permeate with the first polymer membrane to produce an intermediate concentrate, and (2) recirculate a portion of the intermediate concentrate to the first permeate; and a secondary stage housing a second polymer membrane, the secondary stage disposed downstream of the primary stage, the secondary stage configured to (1) contact the intermediate concentrate with the second polymer membrane to produce a second concentrate, and (2) recirculate a portion of the second concentrate to the intermediate concentrate.

12. The system of claim 11, wherein the first permeate is contacted with the first polymer membrane at a temperature of no more than about 50 °C and a pressure of about 700-1100 psi.

13. The system of any one of claims 11-12, wherein the polymer membrane produces a second permeate having a total concentration of solids of no more than about 3 wt.%.

14. The system of any one of claims 11-13, wherein the polymer membrane comprises a nanofiltration membrane.

15. The system of any one of claims 11-13, wherein the polymer membrane comprises a reverse osmosis membrane.

16. The system of claim 1, wherein the feed preparation assembly comprises a heat exchanger configured to adjust the conditioned feed to the predetermined temperature.

17. A system comprising: a feed preparation assembly configured to receive a black liquor feed having an initial total concentration of dissolved solids and suspended solids, the feed preparation assembly comprising: a tubular ceramic membrane configured to remove at least one of a portion of the suspended solids or a portion of the dissolved solids from the black liquor feed to produce a conditioned feed; and a heat exchanger fluidly coupled to the tubular ceramic membrane, the heat exchanger configured to cool the conditioned feed to a predetermined temperature; a first filtration module comprising an oxidized graphene membrane, the first filtration module fluidly coupled to the feed preparation assembly and configured to contact the conditioned feed at the predetermined temperature with the oxidized graphene membrane to produce a first concentrate and a first permeate; and a second filtration module fluidly coupled to the first filtration module, the second filtration module configured to receive the first permeate and produce a second concentrate and a treated permeate, wherein the first concentrate and the second concentrate are combined to produce a treated concentrate having a total concentration of solids that is higher than the initial total concentration of solids.

18. The system of claim 17, wherein the initial total concentration of dissolved solids and suspended solids is between about 1 wt.% and 9 wt.%.

19. The system of any one of claims 17-18, wherein the oxidized graphene membrane comprises a support comprising at least one of a nanofiltration membrane, an ultrafiltration membrane, or a reverse osmosis membrane.

20. The system of any one of claims 17-19, wherein the predetermined temperature is at least about 70 °C.

21. The system of any one of claims 17-20, wherein the graphene oxide membrane has a total solids rejection rate of at least about 50% at the predetermined temperature and a pressure of no more than 800 psi.

22. The system of claim 17, wherein the first filtration module further comprises: a primary stage housing a first graphene oxide membrane, the primary stage configured to (1) contact the adjusted feed with the first graphene oxide membrane to produce an intermediate concentrate, and (2) recycle a portion of the intermediate concentrate to the adjusted feed; and a secondary stage housing a second graphene oxide membrane, the secondary stage disposed downstream of the primary stage and configured to contact the intermediate concentrate with the second graphene oxide membrane to produce a first concentrate. the secondary stage configured to recycle a portion of the first concentrate to the intermediate concentrate.

23. The system of claim 22, wherein, 24. The system of claim 17, wherein the second filtration module further comprises: a primary stage housing a first polymeric membrane, the first stage of the second filtration module configured to (1) contact a first permeate with the first polymeric membrane to produce an intermediate concentrate, and (2) recycle a portion of the intermediate concentrate to the first permeate; and a secondary stage housing a second polymeric membrane, the secondary stage disposed downstream of the primary stage, the secondary stage configured to (1) contact the intermediate concentrate with the second polymeric membrane to produce a second concentrate, and (2) recycle a portion of the second concentrate to the intermediate concentrate.

25. The system of claim 24, wherein the polymeric membrane comprises at least one nanofiltration membrane.

26. The system of claim 24, wherein the polymeric membrane comprises at least one reverse osmosis membrane.

27. The system of any one of claims 24-26, wherein the first permeate is contacted with the polymeric membrane at a temperature of no more than about 50 °C and a pressure of about 700-1100 psi.

28. The system of any one of claims 24-27, wherein the polymeric membrane produces a treated permeate having a total concentration of solids of no more than about 3 wt.%.

29. The system of claim 17, wherein the tubular ceramic membrane has a separation media having an average pore size of no more than about 10 pm. ​ ​

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