Salt recovery solution and method of use

Abstract

The present disclosure relates to a salt recovery solution and a method for separating salt from an aqueous solution. The disclosure also relates to a salt recovery solution and a method for using the same to concentrate a salt or brine solution by recovering water from the salt or brine solution. The salt recovery solution comprises at least two or more components independently selected from any combination of a), b), c), and d). a) is a linear, branched or optionally substituted cyclic C4-C9 ether-containing compound; b) is a straight or branched C3 to C9 alkyl substituted with -OH; c) is a linear, branched, or cyclic C4-C9 ketone or C4-C9 diketone, and d) is a linear or branched C3 to C9 ester-containing compound.

Description

[Technical Field]

[0001] The present disclosure relates to salt recovery solutions and methods for separating salt from aqueous solutions. The present disclosure also relates to salt recovery solutions and methods of use for concentrating salt or brine solutions by recovering water from the salt or brine solution. [Background technology]

[0002] Extracting salts from aqueous solutions is typically an energy-intensive and time-consuming process, requiring water removal and salt crystallization. As reported by Tong et al. (2016), zero waste discharge (ZLD) is an ambitious wastewater management strategy that eliminates all liquid waste from a plant or facility boundary and recovers a significant portion of the water for reuse. However, achieving ZLD is generally characterized by energy intensive use and high costs. As a result, while ZLD has long been considered a technology, it has not been economically viable and has only been applied in limited cases. In recent years, greater awareness of the dual challenges of water scarcity and aquatic pollution has revived global interest in ZLD. Stricter regulations, rising wastewater treatment costs, and the increasing value of freshwater have made ZLD a beneficial or even necessary option for wastewater management. The global ZLD market is estimated to reach at least $100-200 million in annual investment and is rapidly expanding from developed countries in North America and Europe to emerging economies such as China and India. Early ZLD systems were based on stand-alone heating, and wastewater was typically evaporated in a brine concentrator followed by a brine crystallizer or evaporation pond. The condensed distillate in the ZLD system was collected for reuse, while the solids produced were sent to landfills or recovered as a valuable salt byproduct. Such systems have operated successfully for 40 years and are still being built, but they require significant energy and capital. Reverse osmosis (RO), a membrane-based technology widely applied for desalination, has been incorporated into ZLD systems to improve energy and cost efficiency. However, while RO is much more energy-efficient than thermal evaporation, it is only applicable to feedwaters with a limited salinity range. Therefore, other salt concentration technologies capable of treating higher salinity feedwaters, such as electrodialysis (ED), forward osmosis (FO), and membrane distillation (MD), have recently emerged as alternative ZLD technologies for further concentrating wastewater beyond RO. ZLD holds great promise for reducing water pollution and increasing water supplies, but its feasibility will depend on the balance between the benefits associated with ZLD, energy consumption, and capital / operating costs.

[0003] It is an object of the present invention to provide a solution that overcomes these difficulties, or at least to provide a useful alternative. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Tong et al.American Chemical Society 6846 DOI:10.1021 / acs.est.6b01000 Environ.Sci.Technol.2016,50,6846-6855 Summary of the Invention

[0005] In a first aspect, the present invention provides a salt recovery solution suitable for recovering salt from a salt-containing aqueous solution, the salt recovery solution comprising at least two or more components independently selected from any combination of a), b), c) and d); a) is a linear, branched, or optionally substituted cyclic C4-C9 ether-containing compound; b) is a straight or branched C3-C9 alkyl substituted with -OH; c) is a linear, branched, or cyclic C4-C9 ketone or C4-C9 diketone; d) is a linear or branched C3 to C9 ester-containing compound; wherein at least one component of the salt recovery solution is substantially immiscible with a 1 molar aqueous sodium chloride solution at or above 20 degrees Celsius and 1 atmosphere pressure.

[0006] In one embodiment, the ether-containing compound may be a diether or polyether. In one embodiment, the C4 to C9 ether-containing compound is selected from one or more of 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 2-ethyltetrahydrofuran, 3-ethyltetrahydrofuran, dioxane, 2,2-dimethoxypropane, 2-phenoxyethanol, 1-ethoxypropane, and C4 to C9 glycol ethers, or combinations thereof.

[0007] In one embodiment, the straight chain or branched C3-C9 alkyl substituted with -OH is selected from one or more of 1-butanol, 2, butanol, and 1-pentanol, or a combination thereof.

[0008] In one embodiment, the C4 to C9 glycol ether is chosen from one or more of propylene glycol methyl ether, dipropylene glycol dimethyl ether (and isomeric mixtures thereof), dipropylene glycol methyl ethyl acetate, dipropylene glycol n-propyl ether, propylene glycol n-butyl ether, dipropylene glycol n-butyl ether, tripropylene glycol n-butyl ether, propylene glycol phenyl ether, propylene glycol diacetate, or combinations thereof.

[0009] In one embodiment, the C4 to C9 ketone or diketone is selected from one or more of acetonylacetone, 2-butanone, or cyclohexanone. In one embodiment, the C3-C9 ester is ethyl acetate or methyl acetate.

[0010] In one embodiment, the salt recovery solution is a combination of 2-methyltetrahydrofuran and acetonylacetone. In one embodiment, the salt recovery solution is a combination of 2-methyltetrahydrofuran and 1-butanol.

[0011] In one embodiment, the salt recovery solution is a combination of 2-methyltetrahydrofuran and 1-pentanol. In one embodiment, the salt recovery solution is a combination of ethyl acetate and 2-butanone.

[0012] In one embodiment, the salt recovery solution is a combination of ethyl acetate and 2-methyltetrahydrofuran. In one embodiment, the salt recovery solution is a combination of ethyl acetate and 1-butanol.

[0013] In one embodiment, the salt recovery solution is a combination of ethyl acetate and acetonylacetone. In one embodiment, the salt recovery solution is a combination of methyl acetate and 2-butanone.

[0014] In one embodiment, the salt recovery solution is a combination of ethyl acetate and 2-phenoxyethanol. In one embodiment, the salt-containing aqueous solution is an industrial brine.

[0015] In another aspect, the present invention provides a method for recovering salt from an aqueous solution, the method comprising: (a) adding a first aqueous solution containing the salt to a salt recovery solution; and (b) passing the salt recovery solution through the passageway to precipitate the salt on the passageway.

[0016] In one embodiment, the method is a zero waste discharge method. In one embodiment, the process is a countercurrent process. In one embodiment, the method is a non-membrane method.

[0017] In one embodiment, the method is a non-osmotic method. In another aspect, the present invention provides a method for concentrating a salt-containing aqueous solution, the method comprising: (a) adding said salt-containing aqueous solution to a salt recovery solution as defined above; and (b) passing water from the salt-containing aqueous solution through the salt recovery solution.

[0018] In one embodiment, the precipitated salts form part of an aqueous layer that is separate from the salt recovery solution. In one embodiment, the method is a non-membrane method. In one embodiment, the method is a non-osmotic method.

[0019] In one embodiment, the method is a non-membrane and non-osmotic method. In one embodiment, the method concentrates the first aqueous solution by at least 20%, hi other embodiments, the method concentrates the first aqueous solution by at least 30%, or by at least 40%, or by at least 50%, or by at least 60%, or by at least 70%, or by at least 80%, or by at least 90%.

[0020] In one embodiment, the method is a minimal emission method. In one embodiment, the process is a zero waste discharge process. In one embodiment, the aqueous solution is an industrial brine.

[0021] The foregoing summary broadly describes the features and technical advantages of certain embodiments of the present invention. Further technical advantages are set forth below in the detailed description and examples.

[0022] The novel features believed characteristic of the present invention will be better understood from the detailed description when considered in conjunction with any accompanying figures and examples. However, the figures and examples provided herein are intended to help explain or further the understanding of the invention and are not intended to limit the scope of the invention. [Brief explanation of the drawings]

[0023] [Figure 1]FIG. 1 shows a schematic plot of water recovery for each state of a five-stage countercurrent absorption process for a commercial brine. [Figure 2] FIG. 2 shows a flow diagram giving the five stage absorption where water is absorbed from the brine / salt solution in five stages. DETAILED DESCRIPTION OF THE INVENTION

[0024] In the following description, numerous example configurations, parameters, etc. are set forth. However, it should be recognized that such description is not intended to limit the scope of the present invention, but is provided as a description of example embodiments.

[0025] definition In each instance herein, in the description, embodiments, and examples of the present invention, the terms "comprising," "including," and the like, are to be read expansively and without limitation. Thus, throughout the description and claims, unless the context clearly dictates otherwise, the words "comprising," "comprising," and the like, are to be interpreted in an inclusive sense, i.e., "including, but not limited to," as opposed to an exclusive sense.

[0026] The term "about" or "approximately" typically means within 20%, more preferably within 10%, and most preferably even within 5% of a given value or range. Alternatively, the term "about" means within a logarithm (i.e., an order of magnitude), preferably within 2-fold of a given value.

[0027] As used herein, the term "minimal discharge" refers to a method of treating salt water or brine in which minimal effluent or discharge is left behind. As used throughout this specification, the term "brine" or "brine solution" refers to an aqueous solution having a salt concentration in the water. The salt in the water may include sodium chloride, aluminum sulfate, etc., although a wide range of salt solutions is contemplated, which may contain any number of ranges of cations and anions. The concentration of salt in the aqueous solution may range from about 3.5% (a typical concentration in seawater) to much higher concentrations, such as 25%, including brine solutions used in salted foods. Other brine wastewater solutions from textile processing, the semiconductor industry, or the oil, mining, and gas industries are also applicable for use with the present salt recovery solutions and methods defined herein.

[0028] As used herein, the term "zero waste discharge" as used throughout this specification means a wastewater treatment method that leaves no effluent or discharge. As used herein, the term "C3-C9 alkyl" refers to a fully saturated branched or unbranched hydrocarbon moiety, which may be a straight or branched chain in the specified range of 3 to 9 carbons. Preferably, the alkyl contains 3 to 7 carbon atoms, or 3 to 6 carbon atoms. Representative examples of C3-C9 alkyl include, but are not limited to, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, 3-methylhexyl, 2,2-dimethylpentyl, 2,3-dimethylpentyl, n-heptyl, and the like.

[0029] As used herein, the term "C4-C9 ether-containing compound" refers to a 4-, 5-, 6-, 7-, 8-, or 9-membered saturated, unbranched, branched, or cyclic ether. Representative unbranched C4-C9 ether groups include, but are not limited to, methoxyethane, 1-methoxypropane, 1-methoxybutane, 1-methoxypentane, 1-methoxyhexane, 1-methoxyheptane, and 1-methoxyoctane, ethoxyethane, 1-ethoxypropane, 1-ethoxybutane, 1-ethoxypentane, 1-ethoxyhexane, 1-ethoxyheptane, 1-propoxypropane, 1-propoxybutane, 1-propoxypentane, 1-propoxyhexane, 1-butoxybutane, and 1-butoxypentane. Representative branched C4-C9 ether groups include, but are not limited to, 2-methoxypropane, 2-ethoxypropane, 1-isopropoxypropane, 1-isopropoxybutane, 1-isopropoxypentane, 1-isopropoxyhexane, 2-methoxy-2-methylpropane, 2,2-dimethoxypropane, 2-ethoxy-2-methylpropane, 2-methyl-2-propoxypropane, 1-(tert-butoxy)butane, 1-(tert-butoxy)pentane, 2-(tert-butoxy)-2-methylpropane, 2-isopropoxy-2-methylpropane, 2-(tert-butoxy)butane, and 1-(tert-butoxy)-2,2-dimethylpropane. Representative cyclic C4-C9 ether groups include, but are not limited to, oxetane, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 2-ethyltetrahydrofuran, 3-ethyltetrahydrofuran, 2-methyltetrahydro-2H-pyran, 3-methyltetrahydro-2H-pyran, 4-methyltetrahydro-2H-pyran, 2,4-dimethyltetrahydro-2H-pyran, 2-ethyltetrahydro-2H-pyran, 3-ethyltetrahydro-2H-pyran, 4-ethyltetrahydro-2H-pyran, oxepane, oxocane, oxanane, 1,3-dioxolane, dioxane, 1,4-dioxepane, 1,5-dioxocane, 1,5-dioxanane, and 2-phenoxyethanol.In one embodiment, the C4 to C9 ether-containing compound may be substituted with one or more —OH groups. In one embodiment, the C4 to C9 ether-containing compound may be a diether or polyether, such as 2,2-dimethoxypropane.

[0030] The term "C4 to C9 ketone or diketone" refers to a C4 to C9 membered linear, branched, or cyclic compound containing one or two ketone functional groups. Representative examples of C4 to C9 membered ketones include, but are not limited to, butanone, pentanone, hexanone, cyclohexanone, 4-methylcyclohexanone, heptanone, 1,2-diketone, 2,3-pentanedione, octanone, nonanone, heptane-2,6-dione, acetonylacetone, and methyl ethyl ketone.

[0031] As used herein, the term "C3-C9 ester-containing compound" refers to a 4-, 5-, 6-, 7-, 8-, or 9-membered saturated, unbranched, or branched ester. Representative C3-C9 ester-containing compounds as used herein include, but are not limited to, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, butyl butyrate, isopentyl acetate, 3,3-dimethylbutyl acetate, 3,3-dimethylbutyl propionate, isopropyl propionate, tert-butyl propionate, ethyl propionate, methyl pivalate, and ethyl pivalate.

[0032] As used herein, the term "C4-C9 glycol ether" refers to a 4-, 5-, 6-, 7-, 8-, or 9-membered saturated, unbranched, branched, or unbranched glycol ether, including, but not limited to, propylene glycol methyl ether, dipropylene glycol methyl ethyl acetate, dipropylene glycol dimethyl ether (and isomeric mixtures thereof), dipropylene glycol n-propyl ether, propylene glycol n-butyl ether, dipropylene glycol n-butyl ether, tripropylene glycol n-butyl ether, propylene glycol phenyl ether, and propylene glycol diacetate.

[0033] The present disclosure provides salt recovery solutions suitable for recovering salts from aqueous solutions such as industrial brines. While the disclosed salt recovery solutions are suitable for fairly acidic brines, it should be understood that the described salt recovery solutions can be used over a wide pH range. The described salt recovery solutions are also suitable for use with brines having highly soluble salts that tend toward supersaturated solutions. Industrial brines can be highly diverse in nature. It should be understood that any inorganic cation or inorganic anion, and combinations thereof, can produce inorganic salts, and the present disclosure contemplates application to all such salts. It is contemplated that a very wide range of salts may be recoverable from aqueous solutions using the salt recovery solutions described herein. As a non-limiting example, a typical industrial brine may have the following composition, including several different salts: JPEG0007772725000001.jpg47117

[0034] Recovering or precipitating salt from industrial brines or aqueous solutions helps liberate the water within the brine or aqueous solution, freeing it for subsequent water recovery. Extracting or recovering water from wastewater solutions is desirable, with the ultimate goal being to recover or extract substantially all of the water from the aqueous system to result in minimal liquid discharge or zero liquid discharge (ZLD). The described salt recovery solutions work by extracting water from the aqueous solution; in other words, water moves from the aqueous solution to the salt recovery solution. In doing so, salts dissolved in the aqueous solution lose their solvent (water) and precipitate. The water that moves into the salt recovery solution can be separated and recovered from the salt. This provides a viable, energy-efficient method for physically separating salt and water from brine solutions.

[0035] the salt recovery solution comprises at least two or more components independently selected from any combination of a), b), c), and d); a) is a linear, branched, or optionally substituted cyclic C4-C9 ether-containing compound; b) is a straight or branched C3-C9 alkyl substituted with -OH, and c) is a linear or branched C4-C9 ketone or a C4-C9 diketone, and d) is a linear or branched C3 to C9 ester-containing compound; wherein at least one component of the salt recovery solution is substantially immiscible with a 1 molar aqueous sodium chloride solution at or above 20 degrees Celsius and 1 atmosphere pressure.

[0036] Many combinations of components have been found to be suitable as salt recovery solutions, including, but not limited to: A combination of a substituted cyclic C4-C9 ether-containing compound and a C4-C9 diketone, A. A combination of a substituted cyclic C4-C9 ether-containing compound and a linear C3-C9 alkyl substituted with —OH; B. A combination of a C3-C9 ester and a linear C3-C9 alkyl substituted with —OH; C. A combination of a C3-C9 ester and a C4-C9 diketone, D. Combinations of substituted cyclic C4-C9 ether-containing compounds, linear C3-C9 alkyl substituted with -OH, and linear C3-C9 alkyl substituted with -OH; E. Combinations of substituted cyclic C4-C9 ether-containing compounds, C4-C9 diketones and linear C3-C9 alkyls substituted with -OH; F. Combinations of substituted cyclic C4-C9 ether-containing compounds, C4-C9 diketones and C3-C9 alkyls substituted with -OH; G. A combination of 2-methyltetrahydrofuran and acetonylacetone, H. A combination of 2-methyltetrahydrofuran and 1-butanol, I. A combination of 2-methyltetrahydrofuran and 2-butanol, J. A combination of 2-methyltetrahydrofuran and 1-pentanol, K. A combination of 2-methyltetrahydrofuran and methyl ethyl ketone, L. A combination of ethyl acetate and acetonylacetone, M. A combination of ethyl acetate and 1-butanol, N. A combination of 2-methyltetrahydrofuran, 1-butanol and acetonylacetone, O. 2-methyltetrahydrofuran; a combination of 1-butanol and 1-propanol, P. A combination of 2-methyltetrahydrofuran, 1-butanol and 3-methyl-1-butanol, Q. Combination of 2-methyltetrahydrofuran, 1-butanol and 1,4-butanediol R. A combination of methyl acetate and 2-butanone, S. A combination of ethyl acetate and di(propylene glycol) dimethyl ether (mixture of isomers), T. A combination of ethyl acetate and 2-phenoxyethanol, U. A combination of ethyl acetate and 2-dimethoxypropane, V. A combination of ethyl acetate and cyclohexanone, W. A combination of 2-methyltetrahydrofuran and methyl acetate.

[0037] The components defined above create a solution through which water can easily move. The molar ratio of the components of the salt recovery solution can vary widely, but there are preferred molar ratios that can be determined for each combination of components. The molar ratio can vary anywhere from 1:99 or 99:1 for each combination of components. More preferably, the molar ratio can be from about 1:50 or 50:1, or about 1:30 or 30:1, or about 1:10 or 10:1, or about 1:5 or 5:1, or about 1:3 or 3:1, or about 1:2 or 2:1, or about 1:1.

[0038] It should be understood that it is possible to optimize the molar ratio combinations for the specific combinations as well as for specific aqueous solutions. In one embodiment, the molar ratio combinations for several specific combinations for a simple salt solution containing 300 g / liter sodium chloride were found to be optimized as follows: A. A combination of 2-methyltetrahydrofuran and acetonylacetone in a molar ratio of about 1:1 to about 1:10, or in a molar ratio of about 2:1 to about 3:2. B. A combination of 2-methyltetrahydrofuran and 1-butanol in a molar ratio of about 1:1 to about 1:10, or about 3:2 to about 3.7, or about 2:1 to about 3:2. C. A combination of 2-methyltetrahydrofuran and 1-pentanol in a molar ratio of about 1:1 to about 1:10, or in a molar ratio of about 2:1 to about 3:2. D. A combination of ethyl acetate and 2-butanone in a molar ratio of about 1:1 to about 1:10. E. A combination of ethyl acetate and 2-methyltetrahydrofuran in a molar ratio of about 1:1 to about 1:10. F. A combination of ethyl acetate and 1-butanol in a molar ratio of about 1:1 to about 1:10. G. A combination of ethyl acetate and acetonylacetone in a molar ratio of about 1:1 to about 1:10. The optimized molar ratio is the molar ratio that can result in the most rapid and efficient passage or extraction of water from the salt-containing aqueous solution to the salt recovery solution. This means that zero waste discharge goals can be more easily achieved with the optimized molar ratio. The ZLD ratio is the amount of salt recovery solution that needs to be added to extract all the water from the original aqueous solution. The lower the ZLD ratio, the more efficient the extraction of water from the salt-containing aqueous solution and the less salt recovery solution is required. A ZLD ratio of less than about 50 is preferred. A ZLD ratio higher than 50 will also work, but will simply require a larger amount of salt recovery solution to achieve the ZLD.

[0039] It should also be understood that when selecting components for a salt recovery solution, it is important that minimal or no salt crossover into the salt recovery solution is observed. The purpose of the solution is to separate salt from the water of a salt-containing aqueous solution. Therefore, the most desirable combination can also be determined by the combination that exhibits minimal salt crossover at the selected molar ratio. This will vary from salt recovery solution to salt recovery solution.

[0040] In another aspect, the present invention provides a method for concentrating a salt-containing aqueous solution, said method comprising the steps of: (a) adding said salt-containing aqueous solution to a salt recovery solution as defined above; and (b) passing water from the salt-containing aqueous solution into the salt recovery solution;

[0041] In one embodiment, the method does not require a membrane to achieve separation of salt from water. In one embodiment, the method is a non-osmotic method.

[0042] In one embodiment, the method concentrates the first aqueous solution by at least 20%, hi other embodiments, the method concentrates the first aqueous solution by at least 30%, or by at least 40%, or by at least 50%, or by at least 60%, or by at least 70%, or by at least 80%, or by at least 90%.

[0043] In one embodiment, the process is a minimum discharge process, preferably a zero waste discharge process. In one embodiment, the aqueous solution is industrial brine. In a further embodiment, the salt recovery solution is recovered by removing the water extracted therein. This process can be carried out using known techniques for removing or liberating water from salt recovery solutions. Once the water has been removed from the salt recovery solution, it can be recycled for use in further separation processes. The process can be converted into a continuous process. The process can be utilized on a large scale. A suitable process for removing or liberating water from a salt recovery solution is described in International Patent Application PCT / NZ2020 / 050034, published as WO 2020 / 204733, the contents of which are incorporated herein by reference.

[0044] It should be understood that the method may include the further step of adding an additive to the salt recovery solution to further release water retained within the salt recovery solution. In one embodiment, the additive is citric acid. In one embodiment, the citric acid is a concentrated solution of citric acid containing between about 200 and 450 grams of citric acid per liter of water. In another embodiment, the citric acid is anhydrous citric acid that is added directly to the salt recovery solution.

[0045] It should be appreciated that the molar ratio of at least one component a)-c) to the other components independently selected from a)-c) is present in a ratio of about 1:99 or 99:1, and can be from about 1:99 or 99:1, or from about 1:50 or 50:1, or from about 1:10 or 10:1, or from about 1:5 or 5:1, or from about 1:3 or from about 3:1, or from about 1:2 or from about 2:1. In a preferred embodiment, the molar ratio is about 1:1. A chemical engineer will be able to routinely determine the optimum molar ratio depending on the purpose for which the salt recovery solution will be used.

[0046] In a further embodiment, the salt-containing aqueous solution is salt water or brine. It should be understood that the salt-containing aqueous solution may require an optional pretreatment step before being exposed to the salt recovery solution. Such pretreatment may require, for example, a filtration step to remove any undissolved solids or clays.

[0047] Example The examples described herein are provided for the purpose of illustrating particular embodiments of the invention and are not intended to limit the invention in any way. Those skilled in the art, utilizing the disclosure and teachings herein, will be able to create other embodiments and variations without undue experimentation. All such embodiments and variations are considered to be part of the present invention.

[0048] EXAMPLES Preparation and Testing of Various Salt Recovery Solutions All salt recovery solutions were made using two components, Component A and Component B. For each type of salt recovery solution, Component A and Component B were varied according to a molar ratio. The resulting solution was mixed with a salt-containing aqueous solution (brine). The ratio at which complete salt precipitation, i.e., zero liquor discharge (ZLD) condition, existed was determined.

[0049] A standard salt solution was used as an aqueous solution prepared by dissolving sodium chloride (NaCl) in water at a concentration of 300,000 ppm. The compounds used in formulating the salt recovery solution were 2-methyltetrahydrofuran (MeTHF), 1-butanol, 2,5-hexanedione (acetonylacetone), 1-pentanol, ethanol acetate, and 2-butanone.

[0050] Apparatus used: After adding the brine solution to the salt recovery solution, the samples were mixed for 30 seconds on a vortex mixer. After thorough mixing, the samples were centrifuged at 4000 rpm for 1 minute to allow the precipitated salts to settle to the bottom of the sample tube.

[0051] The table below shows the various compounds used in preparing the salt recovery solution.

[0052] [Table 1]

[0053] Example 1 MeTHF and acetonylacetone The salt recovery solution was prepared using MeTHF and acetonylacetone. These individual components were mixed in different molar ratios to determine the ZLD ratio of the NaCl brine solution (300,000 ppm), as shown in Table 2 below.

[0054] [Table 2]

[0055] Example 2 MeTHF and 1-butanol The salt recovery solution was prepared using MeTHF and 1-butanol. These individual components were mixed in different molar ratios to determine the ZLD ratio of the NaCl brine solution (300,000 ppm), as shown in Table 3 below.

[0056] [Table 3]

[0057] Example 3 MeTHF and 1-pentanol The salt recovery solution was prepared using MeTHF and 1-pentanol. These individual components were mixed in different molar ratios to determine the ZLD ratio of the NaCl brine solution (300,000 ppm), as shown in Table 4 below.

[0058] [Table 4]

[0059] Example 4 Ethyl acetate and 2-butanone The salt recovery solution was prepared using ethanol, acetic acid, and 2-butanone. These individual components were mixed in different molar ratios to determine the ZLD ratio of the NaCl brine solution (300,000 ppm), as shown in Table 5 below.

[0060] [Table 5]

[0061] Example 5 Ethyl acetate and MeTHF The salt recovery solution was prepared using acetic acid, ethanol, and MeTHF. These individual components were mixed in different molar ratios to determine the ZLD ratio of the NaCl brine solution (300,000 ppm), as shown in Table 6.

[0062] [Table 6]

[0063] Example 6 Ethyl acetate and 1-butanol The salt recovery solution was prepared using ethyl acetate and 1-butanol. These individual components were mixed in different molar ratios to determine the ZLD ratio of the NaCl brine solution (300,000 ppm), as shown in Table 7.

[0064] [Table 7]

[0065] Example 7 Ethyl acetate and acetonylacetone The salt recovery solution was prepared using ethyl acetate and acetonylacetone. These individual components were mixed in different molar ratios to determine the ZLD ratio of the NaCl brine solution (300,000 ppm), as shown in Table 8.

[0066] [Table 8]

[0067] Example 8 Methyl acetate and 2-butanone The salt recovery solution was prepared using methyl acetate and 2-butanone. These individual components were mixed in different molar ratios to determine the ZLD ratio of the NaCl brine solution (300,000 ppm), as shown in Table 9.

[0068] [Table 9]

[0069] Example 9 Ethanol Acetate and Di(propylene glycol) Dimethyl Ether, Mixture of Isomers The salt recovery solution was prepared using ethanol acetate and di(propylene glycol) dimethyl ether, an isomer mixture. These individual components were mixed in different molar ratios to determine the ZLD ratio of the NaCl brine solution (300,000 ppm), as shown in Table 10.

[0070] [Table 10]

[0071] Example 10 Ethanol Acetate and 2-Phenoxyethanol The salt recovery solution was prepared using ethanol acetate and 2-phenoxyethanol. These individual components were mixed in different molar ratios to determine the ZLD ratio of the NaCl brine solution (300,000 ppm), as shown in Table 11.

[0072] [Table 11]

[0073] Example 11 Ethanol Acetate and 2-Dimethoxypropane The salt recovery solution was prepared using ethanol acetate and 2-dimethoxypropane. These individual components were mixed in different molar ratios to determine the ZLD ratio of the NaCl brine solution (300,000 ppm), as shown in Table 12.

[0074] [Table 12]

[0075] Example 12 Ethanol Acetate and Cyclohexanone The salt recovery solution was prepared using ethanol, acetic acid, and cyclohexanone. These individual components were mixed in different molar ratios to determine the ZLD ratio of the NaCl brine solution (300,000 ppm), as shown in Table 13.

[0076] [Table 13]

[0077] Example 13 MeTHF and methyl acetate The salt recovery solution was prepared using MeTHF and methyl acetate. These individual components were mixed in different molar ratios to determine the ZLD ratio of the NaCl brine solution (300,000 ppm), as shown in Table 14.

[0078] [Table 14]

[0079] These salt recovery solution results demonstrate that it is possible to obtain highly effective salt recovery solutions with low ZLD ratios to effectively separate salt from water in brine solutions. These results demonstrate the potential and applicability of these salt recovery solutions for achieving ZLD with industrial brines at lower energy requirements. These results are encouraging, as many ZLD ratios were shown to be less than 50, and many less than 30. While the ZLD ratios in Example 5 are greater than 50, it should be understood that modifications can be made to the components of Example 5, such as the addition of additional components to create a ternary system, which can significantly alter the ZLD potential.

[0080] Example 14 Modifying the Salt Recovery Solution to a Ternary System In Examples 1-7 above, the salt recovery solutions were formulated to contain two components (binary systems). In the following examples, an additional component was added to see the effect of a ternary system on the ZLD ratio and water absorption performance of the resulting salt recovery solutions.

[0081] The ternary salt recovery solution was mixed with a standard aqueous solution consisting of a concentration of 300,000 ppm NaCl. The percentage at which complete salt precipitation, i.e., zero liquor discharge (ZLD) conditions, existed was determined.

[0082] Several combinations (both binary and ternary) were also tested against a commercially available synthetic brine sample whose composition closely matches that of the mining wastewater stream. The following ternary salt recovery solution was prepared as shown in Table 15. The salt recovery solution was composed of three compounds, Compound A, Compound B, and Compound C. In this example, Compound A was MeTHF and Compound B was 1-butanol. The additional Compound C used was acetonylacetone, 1-propanol, 1-pentanol, 3-methyl-1-butanol, and 1,4-butanediol. The table below shows the different compounds selected as part of the salt recovery solution composition.

[0083] [Table 15]

[0084] The molar ratio of compound C was varied from 0.1 to 0.3 to determine its effect on the water absorption performance of the salt recovery solution. The ZLD ratios of the ternary salt recovery solutions were determined for standard NaCl brine at a concentration of 300,000 ppm.

[0085] A brine sample was prepared containing sodium chloride (NaCl) at a concentration of 300,000 ppm in deionized water. 5 mL of the salt recovery solution was collected in a centrifuge tube. 100 μL of brine sample was added to each tube to determine the ZLD ratio. Table 16 below shows various molar ratios of compounds in the salt recovery solution and their ZLD ratios for standard NaCl brine.

[0086] [Table 16]

[0087] It can be seen from Table 16 that the ZLD ratio can be changed very significantly by the addition of a third component when compared to the observed ZLD ratio (see Table 3 in Example 2 above) for the binary system MeTHF and 1-butanol in a 0.5:0.5 molar ratio, which has a ZLD of 15. A ternary system of MeTHF, 1-butanol, and 1,4-butanediol in a 0.5:0.2:0.3 molar ratio, respectively, gave a ZLD ratio of 5, which appears to be very promising.

[0088] A synthetic brine solution was prepared using aluminum sulfate (Al2(SO4)3.18H2O), calcium chloride (CaCl2), calcium sulfate (CaSO4), iron sulfate (FeSO4.7H2O), and magnesium sulfate (MgSO4) to mimic the low pH of commercially available brine from mining wastewater streams. The composition of the commercial synthetic brine contained primarily sulfate salts with a pH of 1.74. The composition was as shown in Table 17.

[0089] [Table 17]

[0090] Several of the binary and ternary systems tested above were analyzed against a commercially available synthetic brine. Brine solution was added to the salt recovery solution in 100 μl increments to the volumes shown in Table 18 below, until the brine solution passed through the salt recovery solution and formed a "heavy brine layer" below the salt recovery solution. Heavy brine is simply brine solution that has been depleted in water. The samples were mixed on a vortex mixer for 30 seconds. After thorough mixing, the samples were centrifuged for 1 minute to allow the precipitated salts to settle to the bottom of the sample tube. The ZLD ratio was determined by calculating the ratio of the volume of salt recovery solution (ml) divided by the volume of brine (ml) added. The results are shown in Table 18.

[0091] [Table 18]

[0092] The results in the table show that a wide range of ZLD ratios were observed for the commercially available synthetic brines. The ZLD ratios are all very promising, except for the combinations of ethyl acetate and MeTHF and ethyl acetate and 2,2-dimethoxypropane. However, it is anticipated that further refinement of the ethyl acetate and MeTHF systems and ethyl acetate and 2,2-dimethoxypropane systems may be possible by converting them to ternary systems, which may result in lower ZLD ratios for similar synthetic brines. It should be understood that a range of combinations may be useful and appropriate, depending on the application and results to be achieved. For example, it is anticipated that quaternary combinations may also be suitable for some applications.

[0093] With reference to Figure 1, it should be understood that different countercurrent absorption methods can also be utilized. Figure 1 shows a five-stage countercurrent absorption method to reach complete crystallization, and the ratio of salt recovery solution to brine was confirmed at 40:1 in a cascade configuration to reduce the amount of salt recovery solution (absorption) required. The salt recovery solution was ethyl acetate to butanol. The brine was a commercially available brine with a range of chlorides and sulfates, a pH less than 2, and a density of 1.13 g / ml after filtration through a 0.45 μm membrane.

[0094] Figure 1 shows the water recovery rate at each different absorption stage. Complete crystallization is achieved in the fifth stage. By using five absorption stages, the ZLD ratio was determined to be 40:1, which is significantly lower than the ZLD ratio of single-stage absorption (700:1). Through numerous experiments to optimize the ratio of salt recovery solutions for the five stages of countercurrent absorption, a ratio of 40:1 was obtained. This ZLD ratio was the lowest ratio at which the brine reached complete crystallization.

[0095] Referring to Figure 2, a process flow diagram is shown illustrating how a five-stage countercurrent absorption process can be set up. A brine or salt tank is fed to absorption stage 1, and once water has been absorbed from the brine into the salt recovery solution, the brine is then fed to absorption stage 2, which recovers additional water from the now water-depleted brine. This cycle is repeated until all the water has been recovered from the brine. As shown in Figure 1, five stages of water recovery or absorption were required to achieve ZLD.

[0096] The present invention and its embodiments have been described in detail. However, the scope of the present invention is not intended to be limited to the particular embodiments of any method, manufacture, composition of matter, compound, means, sequences, and / or steps described herein. Various modifications, substitutions, and variations can be made to the disclosed materials without departing from the spirit and / or essential characteristics of the invention. Accordingly, those skilled in the art will readily appreciate from this disclosure that subsequent modifications, substitutions, and / or variations that perform substantially the same function or achieve substantially the same results as the embodiments described herein can be utilized in accordance with such related embodiments of the present invention. Accordingly, it is intended that the following claims encompass within their scope such modifications, substitutions, and variations of the combinations, kits, compounds, means, sequences, and / or steps disclosed herein.

Claims

1. A salt recovery solution suitable for recovering salt from a salt-containing aqueous solution, said salt recovery solution comprising at least two or more components independently selected from any combination of a), b), c), and d); a) is a linear, branched, or optionally substituted cyclic C ４ ~C ９ is an ether-containing compound, b) is a linear or branched C substituted with —OH ３ ~C ９ is alkyl, c) is a linear, branched or cyclic C ４ ~C ９ Ketone or C ４ ~C ９ is a diketone, d) is a linear or branched C ３ ~C ９ an ester-containing compound, The salt recovery solution, wherein at least one component of the salt recovery solution is substantially immiscible with 1 molar aqueous sodium chloride at or above 20 degrees Celsius and at 1 atmosphere.

2. 10. The salt recovery solution of claim 1, wherein the linear, branched, or optionally substituted cyclic C4 to C9 ether-containing compound is a diether or polyether.

3. The linear, branched, or optionally substituted cyclic C ４ ~C ９ The ether-containing compound is 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 2-ethyltetrahydrofuran, 3-ethyltetrahydrofuran, dioxane, 1-ethoxypropane, C ４ ~C ９ 3. The salt recovery solution of claim 1 or claim 2, wherein the salt is selected from one or more of: a hydroxybenzoate, ...

4. The linear or branched C substituted with —OH ３ ~C ９ The salt recovery solution of any one of claims 1 to 3, wherein the alkyl is selected from one or more of 1-butanol, 2-butanol, 1-pentanol, or combinations thereof.

5. 5. The salt recovery solution of any one of claims 1 to 4, wherein the linear, branched, or optionally substituted cyclic C4 to C9 ether-containing compound is selected from one or more of propylene glycol methyl ether, dipropylene glycol methyl ethyl acetate, dipropylene glycol n-propyl ether, propylene glycol n-butyl ether, dipropylene glycol n-butyl ether, tripropylene glycol n-butyl ether, propylene glycol phenyl ether, propylene glycol diacetate, or combinations thereof.

6. The linear, branched or cyclic C ４ ~C ９ The salt recovery solution of any one of claims 1 to 5, wherein the ketone or C4 to C9 diketone is selected from one or more of acetonylacetone, 2-butanone, or cyclohexanone.

7. The linear or branched C ３ ~C ９ The salt recovery solution of any one of claims 1 to 6, wherein the ester-containing compound is methyl acetate or ethyl acetate.

8. 10. The salt recovery solution of claim 1, wherein the salt recovery solution is a combination of 2-methyltetrahydrofuran and acetonylacetone.

9. 10. The salt recovery solution of claim 1, wherein the salt recovery solution is a combination of 2-methyltetrahydrofuran and 1-butanol.

10. 10. The salt recovery solution of claim 1, wherein the salt recovery solution is a combination of 2-methyltetrahydrofuran and 1-pentanol.

11. 10. The salt recovery solution of claim 1, wherein the salt recovery solution is a combination of ethyl acetate and 2-butanone.

12. 10. The salt recovery solution of claim 1, wherein the salt recovery solution is a combination of ethyl acetate and 2-methyltetrahydrofuran.

13. 10. The salt recovery solution of claim 1, wherein the salt recovery solution is a combination of ethyl acetate and 1-butanol.

14. 10. The salt recovery solution of claim 1, wherein the salt recovery solution is a combination of ethyl acetate and acetonyl acetone.

15. The salt recovery solution of any one of claims 1 to 14, wherein the salt-containing aqueous solution is an industrial brine.

16. A method for recovering salt from a salt-containing aqueous solution, comprising: a) adding said salt-containing aqueous solution to a salt recovery solution as defined in any one of claims 1 to 15; b) precipitating the salts as they pass through the salt recovery solution.

17. 17. The method of claim 16, wherein the method is a countercurrent method.

18. 1. A method for concentrating a salt-containing aqueous solution, comprising: (a) adding the salt-containing aqueous solution to a salt recovery solution as defined in any one of claims 1 to 15; and (b) passing water from the salt-containing aqueous solution into the salt recovery solution.

19. 20. The method of claim 18, wherein the method concentrates the salt-containing aqueous solution by at least 20%.

20. 20. The method of claim 18 or 19, wherein the method concentrates the salt-containing aqueous solution by at least 30%.

21. 21. The method of any one of claims 18 to 20, wherein the method concentrates the salt-containing aqueous solution by at least 40%.

22. 22. The method of any one of claims 18 to 21, wherein the method concentrates the salt-containing aqueous solution by at least 50%.

23. 23. The method of any one of claims 18 to 22, wherein the method concentrates the salt-containing aqueous solution by at least 60%.

24. 24. The method of any one of claims 18 to 23, wherein the method concentrates the salt-containing aqueous solution by at least 70%.

25. 25. The method of any one of claims 18 to 24, wherein the method concentrates the salt-containing aqueous solution by at least 80%.

26. 26. The method of any one of claims 18 to 25, wherein the method concentrates the salt-containing aqueous solution by at least 90%.

27. 27. The method of any one of claims 18 to 26, wherein the salt-containing aqueous solution is an industrial brine.

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