Process and method for reducing lithium concentration in effluent

Abstract

A process and system are provided for reducing the concentration of lithium using direct lithium extraction (DLE) in a lithium-bearing aqueous effluent, for example from a chemical production process. The system and process comprise using direct lithium extraction to produce a DLE Li-depleted effluent with a concentration of lithium within effluent discharge limits. The DLE Li- depleted effluent may then be directly or indirectly discharged into a body of water. The system and process also result in an DLE Li-rich effluent with a high concentration of lithium that may be further processed for lithium recovery or management.

Description

PROCESS AND METHOD FOR REDUCING LITHIUM CONCENTRATION IN EFFLUENTFIELD

[0001] This specification relates to treatment of lithium bearing effluents.BACKGROUND

[0002] Wastewater and other chemical treatment plant effluents that are to be discharged into a body of water are subject to evolving regulations regarding what substances and in what amounts or concentrations such wastewater or effluents may contain when discharged into the body of water. In particular, the maximum concentrations of certain substances per amount of discharged effluent may be legally mandated to help minimize harm to the environment. Lithium for example is one such substance whose concentration in a wastewater or effluent is typically required to be below a select threshold set by local, national and / or international effluent regulations at the time it is discharged into a body of water.

[0003] Typically, there are stringent regulatory I legal limits regarding the lithium concentration allowed in effluent discharged into a body of water. To comply with such limits, a Zero-Liquid-Discharge (ZLD) method is conventionally used to treat such lithium-bearing effluents. The ZLD method comprises a very complex, expensive and long-lead process flowsheet that is based on achieving no discharge of liquid whatsoever, and typically comprises the use of a crystallizer that utilizes exotic materials of construction.

[0004] The ZLD process concentrates effluents to very high levels of dissolved salts, often leading to very corrosive conditions, which then may require the use of exotic materials (such as titanium or high-Cr alloys) to handle the corrosive substances. This may result in high capital costs, and long lead-times to fabricate and supply the crystal I izer(s) and / or ancillary components. The ZLD process may also use centrifuges for removal of crystallized solids, which in turn could also require exotic materials of construction, and therefore increase pressure on cost and schedule. In addition to this, the ZLD process requires the effluent to be fully evaporated, which is very energy intensive. This adds to the operating cost of the process, and may also consequently add to the carbon-footprint of the project, depending on the energy source used.BRIEF DESCRIPTION OF THE FIGURES

[0005] Figure 1 is a flow sheet of embodiments of the invention as described herein.

[0006] Figure 2 is a further flow sheet of an embodiment of the process as described herein.

[0007] Figure 3 is a graph showing the proportion of concentrations of components in an effluent passing through to the raffinate for an ion exchange process for DLE in accordance with an embodiment of the present disclosure.DETAILED DESCRIPTION

[0008] The present invention is for a process of reducing the concentration of lithium (Li) (including lithium ions and lithium complexes) using direct lithium extraction (DLE), in Li- rich aqueous effluents, for discharge into a body of water. Treatment of the Li-rich aqueous effluent with DLE may produce a treated effluent (also referred to herein as a DLE Li-depleted effluent) for eventual discharge into the body of water. The treatment may comprise producing the treated effluent solely using DLE. DLE may comprise one or more treatment processes, for example, such as ion exchange in combination with membrane processes. The Li-rich effluents subject to the DLE treatment may be from processes which process or produce Li chemicals or complexes or products. These processes may include residential or industrial plants, chemical plants, or any other facilities or similar operations for which there is lithium in the effluents and where such effluents are intended to be discharged to a body of water. The process of the present invention may form part of a waste water treatment process or plant. Discharging the DLE Li-depleted effluent into the body of water may be directly or indirectly after the DLE process is performed on the Li-rich effluent.

[0009] The term ’’bodies of water” in this disclosure means any source of water which may be used or is accessible to other living organisms including plants, animals, or humans, and which may be subject to regulations regarding the amount or concentration of lithium that may be discharged therein to protect against harm to the environmental or living organisms. Such bodies of water include but are not limited to creeks, rivers, ground water, lakes, seas, oceans, bays, canals and estuaries. The treated effluent (i.e. the DLE Li-depleted effluent, with or without additional treatment) may be discharged directly or indirectly into a body of water after the DLE process. For example, the DLE Li-depleted effluent may be first discharged into an industrial park sewage line or an effluent collection pipeline, and the contents of theindustrial park sewage line or effluent collection pipeline may, in-turn, ultimately be discharged into the body of water. The body of water may be, for example, a body of water accessed downstream or at a later time by a living organism such as for drinking or survival, irrigation, or other purposes. The DLE Li-depleted effluent may be subjected to additional non-DLE treatment downstream before being discharged into the body of water. The body of water may be subject to regulatory, contractual, legal or other regulations, restrictions, or limitations on substance discharge concentrations and such discharge limits may be impacted by the type of body of water. For clarity, a body of water in the present disclosure does not include a source which already contains a high amount of lithium therein such as a lithium brine deposit.

[0010] The term “effluents” in this disclosure means an aqueous solution, which may or may not contain solids, that has been received from an upstream process and that would conventionally be intended for disposal.

[0011] Facilities and operations that may produce an effluent containing lithium include lithium carbonate, lithium hydroxide, lithium sulphate, or lithium phosphate facilities, cathode active materials (CAM) facilities, or Li metal and / or Li alloy production facilities. For example, effluents may be generated from the processing of ores or lithium bearing brines for the production of lithium products such as lithium carbonates, lithium hydroxides or lithium sulphates, and these effluents may contain lithium, for example, bleeds from lithium precipitation or impurity removal steps. In another example, Li-rich effluent may be received from the production of CAM, in the washing of CAM materials to remove excess lithium by solubilizing this fraction, and removing the resulting lithium effluent from the CAM product by filtration. Such effluents containing lithium may not be able to be discharged into a body of water if the lithium concentration is too high. Where the lithium concentration is too high, a method of reducing such lithium concentration in the effluent to the acceptable level was conventionally not available. Accordingly, such Li-rich effluent was instead treated using the ZLD process such that no aqueous effluent remained and hence there was no need to discharge anything into a body of water. In an aspect of this invention, an effluent containing lithium that would conventionally be treated using the ZLD process is instead treated using DLE. The Li-rich effluent may be treated with DLE alone or in combination with other treatment processes, and the resulting DLE Li-depleted effluent (containing a reduced amount of lithium as compared to the original Li-rich stream) may be discharged into a body of water as treated effluent. In an embodiment, the DLE Li-depleted effluent may be subjected to further treatmentto remove residual lithium and / or other impurities prior to discharge into the body of water. For example, the removal of such lithium and / or other harmful impurities from the DLE Li-depleted effluent after DLE treatment may involve additional treatment such as membrane separation, precipitation of impurities through oxidation or reduction, modification of pH and / or temperature to alter chemistry, removal of solids using clarification, thickening and / or filtration, and additional pH and temperature adjustment to satisfy discharge criteria.

[0012] In some cases, the concentration of lithium is governed by local, national or international discharge requirements and may be required to be on the order of milligrams of lithium per Litre of effluent (mg / L), for example 5 mg / L or less, 4 mg / L or less, 3 mg / L or less, 2 mg / L or less, 1 mg / L or less, or 0.5 mg / L or less of lithium per liter of effluent. Effluents as described herein may include liquid solutions discharged from an operation or plant which is to be discarded, and which may contain one or more impurities in the aqueous form that need to be removed prior to discharge of the liquid solution into the environment such as a body of water where the water is used downstream for other purposes and / or by other users. Such effluents may also be referred to as wastewater, or a waste stream, and in some cases may also contain some solids. The use of DLE alone or in combination with other treatment processes, for effluent treatment is provided herein as a process that is less costly and / or quicker to deliver, when compared to treatment of the Li-rich effluent stream performed using ZLD, for example.

[0013] DLE is a process unit operation that preferentially removes lithium ion or lithium complex from other constituents present in an aqueous solutions. In most forms, DLE may also extract other constituents present in the aqueous solutions, but, the process may be configured to have a preference for Li over any other constituents. DLE may be comprised of various technologies and configurations, which include but are not limited to, and may be a combination of, adsorption, ion exchange, solvent extraction, membrane separation and chemical precipitation processes. Membrane separation may comprise any one or more of reverse osmosis, nanofiltration and ultrafiltration membranes. Each of membrane separation and chemical precipitation, may not be sufficient to meet discharge criteria alone, and may need to be combined with one another and / or one or more other DLE process, and potentially in a particular order, to meet target lithium discharge requirements. The one or more other DLE processes may comprise ion exchange columns, carousels, stirred bed reactors, moving bed reactors including fluidised or elutriate beds, mixers, and settlers and would followtreatment of the effluent with membrane separation and / or chemical precipitation. In other examples, the DLE process may comprise any one or more of agitated tanks, pumps and filters. Any one or more of the devices or apparatuses discussed in the above examples may also be combined with any other example to provide the DLE process. For example, membrane separation may be used to extract lithium from an effluent and direct the extracted lithium to a smaller concentrated stream, a DLE process such as ion exchange may then be used to extract lithium from the concentrated stream to produce a solution (DLE Li-rich effluent) from which lithium may be precipitated and a treated effluent (DLE Li-depleted effluent, with or without additional treatment) may meet discharge limits with respect to lithium concentrations.

[0014] The DLE process, as discussed above, may use, for example, standard equipment, and does not necessarily need the effluent to be concentrated as in the ZLD process. Both of these aspects may result in a lower capital cost, with more attractive delivery schedules compared to ZLD. Furthermore, the process may be less energy intensive than the use of ZLD for treating the effluent, which may result in a lower operating costs. Should ZLD still be used to treat an effluent from the process, for instance to treat the DLE Li-rich effluent or the Li-production effluent, the process is envisioned to reduce the volume of effluent to be treated by ZLD considerably, for example, by as much as 70% or greater.

[0015] Figure 1 illustrates a process flowsheet 100 for treating Li-rich effluent according to embodiments of the invention that is able to meet low lithium threshold values in DLE Li-depleted effluent discharge streams using DLE, without the need for treatment of the effluent using a ZLD process. In one aspect, ZLD is entirely removed from the flowsheet. In another aspect, ZLD, to a lesser extent than conventional ZLD methods, may be used for secondary treatment of a Li-Production effluent downstream of the DLE process. The dashed lines in Figure 1 are representative of optional or variants of the process flowsheet. The process according to an aspect of the invention comprises receiving a lithium-bearing aqueous effluent or Li-rich effluent 110 as a feed stream from an upstream lithium processing facility or process, and treating the Li-rich effluent using DLE 111 to produce a DLE Li-depleted effluent 112 and a DLE Li-rich effluent 114. The DLE Li-depleted effluent may then be directly or indirectly discharged into a body of water as treated effluent 120. The Li-rich effluent 110 may be, for example, from a chemical plant or other industrial processing facility for processing lithium or lithium complexes. The process may optionally include pre-treatment 116 upstream of the DLE, and additional treatment 118 of the DLE Li-depleted effluent 112 downstream ofthe DLE prior to discharging the DLE Li-depleted effluent into a body of water. The DLE Li- depleted effluent 112 (before or after additional treatment depending on discharge criteria) may be discharged to the body of water as a treated effluent 120 with an acceptable concentration of lithium. An acceptable concentration of lithium may be a concentration of lithium on the order of mg / L, for example less than 5mg / L, or a nominal amount of lithium, depending on the body of water. For example, a body of water intended for use as drinking water or which is used by animals and fish downstream may have more stringent discharge limits than a body of water intended only for irrigation downstream.

[0016] The process may further include treating or recycling the DLE Li-rich effluent 114. In an example, the DLE Li-rich effluent may be recycled back to the lithium processing plant that first produced the Li-rich effluent stream 110, or may be treated by additional treatment 122 such as, for example ZLD, precipitation, or a further DLE. The DLE Li-rich effluent may be sent to a Li-production process to produce a lithium product and may include a recycling step for the resulting Li-production effluent 132 that is discharged from the Li- production process 124. The DLE Li-rich effluent 114 may ultimately be used to obtain substances of further commercial value such as lithium carbonate or lithium hydroxide. The process may include the addition of a non-lithium or low-lithium bearing aqueous solution 126 addition to any number of steps in the process. A low-lithium solution for example may comprise lithium concentrations within the allowed discharge limits. In addition, Figure 1 further provides a process with optional waste streams that may be further processed or recycled or disposed, for example an optional pre-treatment waste stream 128, an optional additional treatment waste stream 130, and an optional lithium production effluent stream 132. These waste streams may be further processed similar to the DLE Li-rich effluent 114 stream, for example, the Li-production effluent 132 may be recycled back upstream to the lithium production plant that produced the Li-rich effluent 110 or back to the DLE step to manage lithium in the process. In an example, the Li-production effluent 132 or the DLE Li-rich effluent 114 may be further treated by a ZLD process. Since the volume of DLE Li-rich effluent 114 or the volume of the Li production effluent 132 is much less than the original volume of Li-rich effluent 110 that would have been treated with ZLD in a conventional process, the size of the ZLD for treating the DLE Li-rich effluent 114 or the Li production effluent 132 may be much smaller. A smaller ZLD processes may be less costly in both capital cost and operating cost.

[0017] The Li-rich effluent 110 may, for example, comprise a lithium concentration of 20 g / L or less, for example 15 g / L or less, 10 g / L or less, 5 g / L or less, 1 g / L or less, or 10 mg / L or less. The Li-rich effluent 110 may be received from an upstream industrial chemical complex, for example a battery, wastewater or other chemical facility where lithium reports to and is found in the effluent. After receiving the Li-rich effluent, the process as described herein includes preferentially removing lithium ions or lithium complexes from the effluent using DLE. The DLE may be positioned in place or selected as a replacement for a ZLD process for treating Li-rich effluent from the Li processing plant, or to reduce the size of the ZLD. The DLE process outputs a DLE Li-depleted effluent 112 and a DLE Li-rich effluent 114. For example, the DLE Li-depleted effluent 112 is a lithium depleted effluent which comprises no lithium or low levels of lithium, such as levels below an effluent discharge limit. In an example, the DLE Li-depleted effluent comprises a lower concentration of lithium as compared to the Li-rich effluent 110 such that the DLE Li-depleted effluent 112 may be sufficiently low in lithium so it can be discharged to the body of water, or the DLE Li-depleted effluent 112 may require additional treatment. For example, the DLE Li-depleted effluent 112 may be the final treated effluent that is sent to a body of water, or may be subjected to further treatment as further discussed herein. The body of water where the treated effluent 120 is sent may be for example a natural body of water such as a river, stream, ground water, the sea, ocean or a lake, which water may have further uses downstream of the treated effluent discharge. In an example, the DLE Li-depleted effluent may comprise a lithium concentration on the order of mg / L, or no lithium. For example, the DLE Li-depleted effluent may comprise a lithium concentration of 5 mg / L or less, 4 mg / L or less, 3 mg / L or less, 2 mg / L or less, 1 mg / L or less, 0.5 mg / L or less or 0 mg / L. The DLE Li-rich effluent comprises a lithium concentration that may be higher than the concentration of lithium in the Li-rich effluent 110. The DLE Li-rich effluent 114 may be further processed or recycled for lithium management or recovery, for example to recover the contained lithium, for sale to the market, or recycled for further treatment, to enable it to be sold. In another example, the DLE Li-rich effluent may be recycled back to the DLE or to the □-processing plant.

[0018] The process may optionally include a pre-treatment step upstream of the DLE. The pre-treatment step may include any one or more of filtration of impurities, pH adjustment, temperature adjustment, precipitation, membrane concentration, and adjustments of other properties of the wastewater stream. In an example, the Li-bearing aqueous effluent (or Li-richeffluent), may be first treated in a pre-treatment step which may be necessary to remove impurities, and / or to adjust pH, temperature or other properties of the feed solution, prior to the use of DLE and / or to optimize the process. In addition to this, pre-treatment may also remove some of the lithium prior to DLE, for instance using precipitative techniques to generate lithium carbonate or lithium phosphate which may be extracted in a waste stream 128 from the pretreatment step.

[0019] The process may optionally include additional treatment of the DLE Li-depleted effluent 112 downstream of the DLE. This treatment may comprise for example, residual lithium and / or heavy metal removal and / or pH adjustment, to meet additional aspects of effluent discharge criteria. The treated DLE Li-depleted effluent 112 may then be discharged to the environment as treated effluent 120.

[0020] Some industrial or residential processes may also produce effluents that do not contain lithium or that contain low levels of lithium, for example levels of lithium below the allowed discharge levels, but which still need to be treated, prior to discharge. In an example, these non-lithium or low lithium effluents 126 can be added to the process described herein. For example, the non-lithium or low lithium effluents can be added to DLE Li-depleted effluent 112 which the lithium has been extracted from. This may allow for consolidation of the streams prior to additional treatment using a common system, which may enable that treatment to occur in a capital-effective manner. Blending of non-lithium or low lithium effluents 126 with the DLE Li-depleted effluent, or discharge from additional treatment, may further reduce the lithium concentration in the final treated effluent 120. Other variants of the process described herein may include mixing the Li-rich effluents 110 with non-lithium or low lithium bearing effluents 126, prior to the DLE unit, for example, before or after pre-treatment (if present). These variants and flowsheet options may be done in isolation, or in combination with one-another.

[0021] Figure 2 illustrates a flow sheet of an embodiment of a treatment process 200 for an effluent or feed containing lithium 210 in accordance with the present disclosure. In Figure 2, a DLE process 211 comprises an ion exchange 230 and a reverse osmosis (RO) 240. In an example, as shown in Figure 2, an effluent feed containing lithium 210 is sent to the DLE 211 ion exchange process 230 at 1 m3 / hr. The ion exchange process 230 may include for example the stages of adsorption 232, washing 234, desorption 236, and washing again 238, before being sent back to the adsorption step 232. A lithium concentration in the resulting raffinate 212 from the ion exchange process 230 may still be above the lithium dischargecriteria, such as may be set out by regulators. A reverse osmosis process 240 may therefore be included in the DLE process 211 , in conjunction with the ion exchange process 230 to remove the residual lithium in stream 212 to at or below the specified concentration limits according to the discharge criteria. Treatment of the effluent with the reverse osmosis process 240 may occur subsequent to the treatment of the effluent with the ion exchange process 230. DLE Li-depleted effluent 219 as a treated effluent, comprising an appropriate lithium discharge limit, may then result from the reverse osmosis process 240, which may be additionally treated or discharged directly to a body of water. Retentate stream 214 may be combined with the ion exchange eluate 216 from desorption stage 236, to produce a DLE Li-rich effluent 218 for treatment in a Li precipitation process 224 to recover lithium products. The resulting Li- production effluent from Li precipitation may be recycled to back into the DLE process, or to the upstream Li processing plant, or sent for further treatment, for example to additional DLE or a ZLD process. The DLE Li-depleted effluent 219 may exit the DLE process at, for example, 0.95 m3 / hr while the Li-production effluent may exit the process at a much lower rate, for example 0.22 m3 / hr. As such, only a small proportion of the volume of the Li-rich feed stream 210 containing a lithium concentration above the discharge limit needs to be handled downstream. It may be handled by recycling or additional treatment. In an example, ZLD may be used for additional treatment of the Li-production effluent 226. The ZLD may be operated at a much lower flowrate than what the conventional ZLD process would need to treat in Li- rich feed stream 210.

[0022] In another aspect, the invention as disclosed herein comprises a system for reducing lithium concentration in an aqueous effluent. The system includes a DLE module fluidly connected to an effluent outlet from a residential or industrial processing facility or operation which produces lithium-bearing effluents, for example from a chemical, or wastewater plant. The DLE further includes a DLE Li-depleted effluent outlet and a DLE Li-rich effluent outlet. The DLE module may include adsorption, ion exchange, solvent extraction, membrane separation and / or chemical precipitation. Where membrane separation and / or chemical precipitation is used for the DLE process, further additional DLE steps before or after the membrane separation and / or chemical precipitation may be required, for example, ion exchange columns, carousels, stirred bed reactors, mixers, and / or settlers. The DLE process may comprise any one or more of, ion exchange columns, carousels, stirred bed reactors, moving bed reactors including fluidised or elutriate beds, mixers, settlers, reverse osmosismembranes, nanofiltration membranes, ultrafiltration membranes, agitation tanks, pumps and other filters to ultimately achieve the discharge criteria established by regulators for any given site. Any one or more of the devices or apparatuses discussed in the above examples may also be combined with any other to provide the DLE process. The system may include a pretreatment module upstream of the DLE and downstream of the Li-rich effluent outlet. The pretreatment module may be used for any one or more of the following processes: filtration of impurities, pH adjustment, membrane concentration, temperature adjustment, precipitation, and adjustments of other properties of the effluent from the effluent outlet. The system may further include additional treatment downstream of the DLE, such as for example, a pH adjuster or heavy metal removal device. In a further option, the system may include a number of connections to a non-lithium or low lithium bearing aqueous effluent which may or may not contain solids, for example, from the same or a different outlet of the processing facility, or from a different processing facility. The non-lithium or low lithium bearing effluent may be connected to the system upstream or downstream of the DLE, and may be before or after pretreatment, or before or after any additional downstream treatment before final treated effluent discharge to a body of water. The DLE system may be a replacement for an existing ZLD system used to treat the Li-rich effluent to produce a DLE Li-depleted effluent, or substantially reduce the flowrate of the effluent which may be treated using ZLD. For example, a ZLD process may be used downstream of the DLE Li-rich effluent outlet of the DLE to treat DLE Li-rich effluent which is provided at a substantially reduce the flowrate as compared to the Li-rich effluent from the processing facility. The system may also include a connection between the DLE Li-rich effluent outlet and a lithium production plant or process, or may be connected to further treatment or processing for recovering lithium from the DLE Li-rich effluent. The DLE Li-rich effluent may be further treated to precipitate out the lithium, and the resulting Li- production effluent may be recycled, for example recycled back to the DLE, or further treated downstream.

[0023] The DLE Li-rich effluent may be sent for further recycling and recovery of lithium or to a lithium production plant or process as previously discussed. A waste portion of the DLE Li-rich effluent, before or after recycling or lithium production may be sent to a further waste processing step, for example, the DLE Li-rich effluent waste stream may be sent to a ZLD in whole or in part, or in another example, may be sent to a subsequent DLE process. The ZLD for treating the DLE Li-rich effluent waste stream may be smaller as compared to aconventional effluent treatment process that uses ZLD. The system and process as disclosed herein may therefore incorporate a DLE process for treating Li-rich effluent from a processing facility to produce a DLE Li-depleted effluent as a replacement for large, expensive ZLD processes, while including a much smaller and more cost efficient ZLD process to treat DLE Li-rich effluent waste streams expelled from the DLE process.EXPERIMENTAL RESULTS

[0024] An example of the process as described herein was tested. A resin-based ion exchange process was employed as part of a DLE process to remove lithium from an effluent feed. The effluent feed composition used in the experiment is shown in Table 1 , which presents the target (calculated) concentration of lithium and other key elements, as well as the measured concentrations. The feed solution was synthetic and was prepared from LiOH, □2804, NaCI, NaOH, KOH, MgCh, CaCh, B(OH)a and deionized water.TABLE 1 : Effluent Feed

[0025] The feed was passed through a DLE comprising a column containing weak acid cation exchange resin in H+form (Purolite PPC104Plus). Samples were taken of the DLE resin ion exchange process at various bed volume (BV) intervals and analyzed. The results are shown in Table 2, and Figure 3. Figure 3 is a graph providing an example of an ion exchange process for DLE comprising the proportion of the concentration of each component in the effluent passing through to the raffinate. Based on the results, approximately 70% of the lithium may be extracted from the effluent feed in a single pass through the DLE resin ion exchange.TABLE 2Feed 4028 329 281 <0.01 59 195 121.3 858 40 6 0 6 105 2.02.8 1364 60 14 0 2 209 2.24.1 1360 88 24 <0.01 0 208 2.45.2 1377 90 30 <0.01 0 208 2.65.6 1512 106 46 0 0 207 9.66.6 1807 133 63 <0.01 0 205 11.87.7 2247 169 87 <0.01 0 207 128.7 2584 201 113 <0.01 0 209 12Loaded resin, 22,302 2,008 1 ,740 515 - N / A mg / L

[0026] The DLE process may further comprise reverse osmosis to further treat the ion exchange raffinate to further reduce the lithium concentration to at or below discharge criteria levels. In this example experiment, the DLE process comprises the combination of the ion exchange followed by reverse osmosis. The reverse osmosis membranes may recover greater than or equal to 95% of the water contained in the ion exchange raffinate as a DLE Li-depleted effluent that may be discharged into a body of water. The contained lithium is concentrated into the retentate stream from the reverse osmosis step. The retentate stream may be further combined with the ion exchange eluate stream to produce a DLE Li-rich effluent that may be processed, for instance by lithium carbonate precipitation. The retentate from reverse osmosis, DLE Li-rich effluent, or the waste stream from lithium carbonate precipitation may be recycled or sent to other downstream waste management processes. In one example, the Li-production waste stream may be sent to a ZLD circuit. The ZLD circuit may be smaller than the conventional ZLD circuit which would have been required to treat the initial Li-rich effluent from the processing facility.

[0027] An aspect of the invention as disclosed herein provides for a new use of direct lithium extraction for reducing lithium concentration in an aqueous effluent before discharge to a body of water. For example, use of the DLE according to aspect as described herein may include treatment of aqueous effluent from an industrial or residential chemical production or wastewater treatment plant or system.

Claims

CLAIMS:We claim:

1. A process for reducing a lithium concentration in a lithium-bearing aqueous effluent to meet a discharge limit, the process comprising, receiving a lithium-bearing effluent, preferentially removing lithium ions or lithium complexes from the lithium-bearing aqueous effluent using direct lithium extraction (DLE) to produce a DLE Li-rich effluent, and a DLE Li- depleted effluent as a treated effluent.

2. The process of claim 1 , wherein the lithium-bearing aqueous effluent is a select effluent that is conventionally treated with a zero-liquid discharge (ZLD) process, and wherein the DLE process is used in place of the ZLD process to treat the select lithium-bearing aqueous effluent to produce the DLE Li-depleted effluent as the treated effluent.

3. The process of claim 1 or 2 wherein the DLE Li-depleted effluent comprises a lithium concentration that is less than the concentration of lithium in the lithium-bearing aqueous effluent or less than a discharge limit.

4. The process of any one of claims 1 to 3 wherein the DLE Li-depleted effluent downstream of the DLE comprises a lithium concentration on the order of mg / L, for example 2 mg / L or less or 0.5 mg / L or less.

5. The process of any one of claims 1 to 4 further comprising discharging the DLE Li- depleted effluent to a body of water as the treated effluent.

6. The process of any one of claims 1 to 5 comprising receiving the lithium bearing aqueous effluent from a chemical processing plant or system, a wastewater treatment plant or a residential operation and discharging at least a portion of the DLE Li-depleted effluent to a body of water as the treated effluent.

7. The process of any one of claims 1 to 6 wherein the lithium bearing aqueous effluent is combined with a non-lithium or low lithium bearing effluent upstream of the DLE.

8. The process of any one of claims 1 to 7 further comprising a pre-treatment step upstream of the DLE.

9. The process of claim 8 wherein the pre-treatment step comprises any one or more of filtration of impurities, pH adjustment, temperature adjustment, precipitation, membrane separation, and adjustments of other properties of the effluent.

10. The process of any one of claims 1 to 9 wherein at least a portion of the DLE Li-rich effluent is precipitated or filtered to remove a solid lithium product so as to result in a Li- production effluent, and wherein the Li-production effluent is recycled upstream of the DLE.

11. The process of any one of claims 1 to 10 wherein at least a portion of the DLE Li-rich effluent is sent to a downstream lithium production plant.

12. The process of any one of claims 1 to 11 wherein the DLE Li-depleted effluent is combined in whole or in part with a non-lithium or low-lithium bearing effluent.

13. The process of any one of claims 1 to 12 further comprising additional treatment to at least a portion of the DLE Li-depleted effluent downsteam of the DLE to produce the treated effluent prior to discharge into a body of water.

14. The process of claim 13 further comprising combining the treated effluent or the DLE Li-depleted effluent before additional treatment, in whole or in part with a non-lithium or low lithium bearing effluent.

15. The process of claim 13 or 14 wherein the additional treatment comprises one or more of heavy metal removal and pH adjustments.

16. The process of any one of claims 13 to 15 wherein the treated effluent is discharged to a body of water, wherein water in the body of water is used directly or indirectly by animals, for drinking or survival, for irrigation, or for other processes with limits on lithium concentration levels.

17. The process of any one of claims 1 to 16 wherein removing the lithium ions or lithium complexes using DLE comprises any one or more of the following processes: adsorption, ion exchange, solvent extraction, membrane separation and chemical precipitation.

18. The process of any one of claims 1 to 17 wherein the lithium-bearing aqueous effluent comprises a lithium concentration of 20 g / L or less.

19. The process of any one of claims 1 to 18 wherein at least a portion of the DLE Li-rich effluent, before or after additional treatment or lithium production, is sent to a zero liquid discharge (ZLD) process.

20. A system for reducing lithium concentration in an aqueous effluent, the system comprising, a direct lithium extraction (DLE) module in fluid communication with an upstream lithium processing facility effluent outlet, wherein the DLE comprises an DLE Li-rich effluent outlet for a lithium concentrated stream and a DLE Li-depleted effluent outlet for a treated effluent stream.

21. The system of claim 20 wherein the DLE Li-depleted effluent outlet is connected to a downstream body of water with discharge limits on lithium concentration.

22. The system of claim 20 or 21 wherein the DLE module comprises any one or more of, adsorption, ion exchange, solvent extraction, membrane separation and chemical precipitation.

23. The system of any one of claims 20 to 22 wherein the DLE module comprises any one or more of ion exchange columns, carousels, stirred bed reactors, moving bed reactorsincluding fluidised or elutriate beds, mixers, settlers, reverse osmosis membranes, nanofiltration membranes, ultrafiltration membranes, agitation tanks, pumps and other filters.

24. The system of any one of claims 20 to 23 further comprising a pre-treatment module between the lithium processing facility effluent outlet and the DLE module.

25. The system of claim 24 wherein the pre-treatment module comprises any one or more of filtration of impurities, pH adjustment, temperature adjustment, precipitation, and adjustments of other properties of the aqueous effluent from the upstream lithium processing facility effluent outlet.

26. The system of any one of claims 20 to 25 further comprising additional treatment downstream of the DLE Li-depleted effluent outlet.

27. The system of claim 26 wherein the additional treatment comprises any one or more of heavy metal removal and pH adjustments.

28. The system of any one of claims 20 to 27 further comprising a non-lithium or low lithium bearing effluent connected to any one or more of, (i) an aqueous lithium bearing effluent upstream of the DLE but downstream of the lithium processing plant effluent outlet, and (ii) the DLE Li-depleted effluent outlet.

29. The system of claim 26 or 27 further comprising a non-lithium or low lithium bearing effluent connected to the DLE Li-depleted effluent upstream or downstream of the additional treatment.

30. The system of any one of claims 20 to 29 wherein the lithium processing facility effluent outlet is from a chemical production plant or system, a wastewater treatment plant or system, a residential operation or other lithium processing facility.

31. The system of any one of claims 20 to 30 further comprising a zero liquid discharge (ZLD) system connected to and downstream of the DLE Li-rich effluent outlet.

32. Use of direct lithium extraction (DLE) for reducing lithium concentration in an aqueous effluent to below discharge concentration limits of a body of water before discharge to the body of water.

33. Use of DLE according to claim 32, wherein the aqueous effluent is from a chemical processing plant or system, a wastewater treatment plant or system, a residential operation or other lithium processing facility that handles / processes lithium including lithium complexes, compounds and chemicals.

Images