WO2013005694A1 - Method for separating and recovering alkali metal, and apparatus for separating and recovering alkali metal - Google Patents

Method for separating and recovering alkali metal, and apparatus for separating and recovering alkali metal Download PDF

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Publication number
WO2013005694A1
WO2013005694A1 PCT/JP2012/066798 JP2012066798W WO2013005694A1 WO 2013005694 A1 WO2013005694 A1 WO 2013005694A1 JP 2012066798 W JP2012066798 W JP 2012066798W WO 2013005694 A1 WO2013005694 A1 WO 2013005694A1
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water
alkali metal
nanofiltration membrane
unit
concentration
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PCT/JP2012/066798
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French (fr)
Japanese (ja)
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寛生 高畠
谷口　雅英
佐々木　崇夫
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東レ株式会社
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/027—Nanofiltration
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
    • C22B3/22—Treatment or purification of solutions, e.g. obtained by leaching by physical processes, e.g. by filtration, by magnetic means, or by thermal decomposition
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/30—Wastewater or sewage treatment systems using renewable energies
    • Y02W10/37—Wastewater or sewage treatment systems using renewable energies using solar energy

Definitions

  • the present invention relates to a method and apparatus for recovering alkali metals such as lithium and potassium from lake water, groundwater, industrial wastewater and the like.
  • lithium carbonate is used for a surface acoustic wave filter in addition to an electrode material of a lithium ion battery and a heat-resistant glass additive.
  • High purity products are used as filters and transmitters for mobile phones and car navigation systems.
  • Lithium bromide is used as a refrigerant absorbent for large-scale air-conditioning absorption refrigerators in buildings and factories, and lithium hydroxide is used as a raw material for grease and lithium batteries (primary and secondary) for automobiles.
  • Applications of metallic lithium include foil as a negative electrode material for primary batteries and raw materials for butyl lithium for synthetic rubber catalysts.
  • salt lake brine and ore are contained in salt lake brine and ore, and it is advantageous to recover resources from salt lake brine in terms of production cost.
  • the composition is largely classified into chloride brine, sulfate brine, carbonate brine, and calcium brine.
  • sulfate brine which has the largest amount of resources, has a low solubility of sulfate during the purification process. Many of them form salts or contain a lot of alkaline earth metal salts or sulfates, and it is difficult to efficiently recover lithium.
  • Patent Documents 1 and 2 As measures to solve this, methods using adsorbents (Patent Documents 1 and 2) and the like have been proposed. However, the cost is difficult, and it has been established as a technique for stably recovering lithium at a low cost. Absent. Conventional low-cost methods include drying the brine in the sun and removing impurities while concentrating, but when the lithium concentration is low or the alkaline earth metal salt or sulfate concentration is high, etc. There was a problem that it was difficult to apply. Furthermore, electrodialysis and membrane filtration are being studied (Non-Patent Document 1), but they have not been put into practical use.
  • An object of the present invention is to provide a method and an apparatus for efficiently recovering alkali metals from raw water containing alkali metals such as lithium and potassium such as lake water, groundwater, and industrial wastewater.
  • the present invention relates to the following (1) to (7).
  • the nanofiltration membrane is used to permeate and separate the raw water containing alkali metal to obtain nanofiltration membrane permeated water and nanofiltration membrane concentrated water, and the nanofiltration membrane permeated water is permeated and separated using a concentration unit. To obtain concentrated unit concentrated water, and recover at least part of the alkali metal contained in the concentrated unit concentrated water.
  • the concentration unit comprises any one of a reverse osmosis membrane unit, a distillation unit, and a membrane distillation unit.
  • the concentration unit includes a mechanism that cools and recovers low-concentration water using raw water having a temperature lower than the temperature of the supply water supplied to the concentration unit. Alkali metal separation and recovery method.
  • a nanofiltration membrane unit that obtains nanofiltration membrane permeated water and nanofiltration membrane concentrated water by permeating and separating raw water containing alkali metal using a nanofiltration membrane, and permeating and separating the nanofiltration membrane permeated water.
  • An alkali metal separation and recovery apparatus comprising: a concentration unit for obtaining concentrated unit concentrated water; and a recovery unit for recovering at least a part of the alkali metal contained in the concentrated unit concentrated water.
  • the present invention makes it possible to efficiently recover alkali metals such as lithium and potassium from raw water in which various solutes coexist.
  • FIG. 1 is a schematic flowchart showing one embodiment of the alkali metal separation and recovery method according to the present invention.
  • FIG. 2 is a schematic flow diagram showing an embodiment of the alkali metal separation and recovery method for refluxing the concentrated unit waste water to the supply water according to the present invention.
  • FIG. 3 is a schematic flow diagram showing one embodiment of an alkali metal separation and recovery method for refluxing concentrated unit waste water to pretreated water according to the present invention.
  • FIG. 4 is a schematic flow diagram showing one embodiment of the alkali metal separation and recovery method according to the present invention, in which the concentration unit is a heat utilization type concentration unit.
  • FIG. 1 An example of the execution flow of the alkali metal recovery of the present invention is shown in FIG.
  • raw water 1 containing alkali metal is temporarily stored in a raw water tank 2, then processed by a pretreatment unit 4 by a supply pump 3, and the pretreated supply water is a booster pump 5.
  • the nanofiltration membrane unit 6 Is sent to the nanofiltration membrane unit 6 to obtain nanofiltration membrane permeated water and nanofiltration membrane concentrated water 7 from which alkali metal is permeated and separated.
  • the permeated water of the nanofiltration membrane unit 6 is sent to the concentrating unit 9 by the booster pump 8 to obtain the concentrating unit waste water 10 in which the alkali metal has a low concentration and the concentrated unit concentrated water 11 in which the alkali metal is concentrated.
  • the concentrated unit concentrated water 11 is sent to the recovery unit 12 to recover the alkali metal 13 (embodiments (1) and (2)).
  • the size of the alkali metal on the supply water side is smaller than other alkaline earth metals, so that it is not blocked by the nanofiltration membrane.
  • the alkali metal concentration in the permeate does not exceed the alkali metal concentration in the raw water, so by concentrating the permeate of the nanofiltration membrane with a concentration unit, Alkali metal can be efficiently recovered in the post-processing recovery unit (effect of the embodiment (1)).
  • the alkali metal that is the subject of the present invention is preferably one containing at least lithium, and in salt lake brine etc. for carrying out the method of the present invention, among alkali metals such as sodium, potassium, rubidium, cesium and the like in addition to lithium.
  • At least one metal, alkaline earth metal such as magnesium, calcium, strontium, typical elements (aluminum, tin, lead, etc.), transition elements (iron, copper, cobalt, manganese, etc.), and one or more conjugates
  • a compound composed of a salt with a base for example, chloride ion, nitrate ion, sulfate ion, carbonate ion, acetate ion, etc.
  • a base for example, chloride ion, nitrate ion, sulfate ion, carbonate ion, acetate ion, etc.
  • the concentration of each of these components is not particularly limited, but from the viewpoint of separation and recovery efficiency, the lithium ion concentration of the feed water after dilution is preferably in the range of 0.5 ppm to 10,000 ppm, more preferably 5 ppm to 5000 ppm.
  • An aqueous solution having a range of 50 ppm to 2000 ppm is preferably used as the raw water.
  • the purification inhibitor when a desired purified alkali metal salt such as lithium carbonate or potassium chloride is separated and recovered by post-treatment, the purification inhibitor may be an alkaline earth metal salt or sulfate that easily produces a hardly soluble salt, Examples of such organic substances include magnesium salts and / or sulfates.
  • the magnesium ion concentration in the alkali metal salt aqueous solution to be supplied water is 1000 times or less than the lithium ion concentration. The efficiency is preferably 500 times or less, more preferably 100 times or less, more preferably 100 times or less.
  • the magnesium ion concentration in the aqueous solution containing the alkali metal salt is 7 times or less than the lithium ion concentration in the aqueous solution. Until then, it is preferable to perform the removal treatment by the nanofiltration membrane unit. If this ratio exceeds 7 times, the recovery efficiency of the purified alkali metal salt is significantly reduced.
  • the weight of the purification inhibiting substance at this time is calculated based on the weight in terms of ions such as magnesium ions and sulfate ions.
  • the weight in terms of lithium ion and the weight of the purification inhibitor can be determined by quantifying various ion concentrations in an aqueous solution containing an alkali metal salt, for example, by ion chromatography.
  • salt lake brine contains magnesium ions and sulfate ions in the range of 100 ppm to 30,000 ppm.
  • the nanofiltration membrane referred to here is a membrane defined by IUPAC as “a pressure-driven membrane in which particles and polymers of a size smaller than 2 nm are blocked”, but is effective for application to the present invention.
  • the membrane has a charge on the membrane surface, and has improved ion separation efficiency by a combination of separation by pores (size separation) and electrostatic separation by charge on the membrane surface. It is preferable to apply a nanofiltration membrane that is capable of removing polymers by size separation while separating metal ions and other ions having different charge characteristics by charging.
  • the glucose removal rate when a 1000 ppm isopropyl alcohol aqueous solution at 25 ° C. and pH 6.5 and a 1000 ppm glucose aqueous solution at 25 ° C. and pH 6.5 were permeated at an operating pressure of 0.5 MPa, respectively.
  • Is 90% or more, and a nanofiltration membrane having a difference between glucose removal rate and isopropyl alcohol removal rate of 30% or more is used, regardless of the total salt concentration, alkali metal salts, especially lithium salts and purification inhibitors Is particularly preferred since the separation of is achieved with very high efficiency.
  • the nanofiltration membrane unit 6 is composed of modularized nanofiltration membranes. For example, one or a plurality of spiral nanofiltration membrane elements connected to each other and housed in a container, or connected in series or in parallel. Refers to
  • nanofiltration membrane unit 6 With respect to the nanofiltration membrane unit 6, one-stage processing is also possible, and in the case of increasing the recovery rate, there is no problem in making the so-called multistage in which the concentrated water is further processed by the next nanofiltration membrane unit 6. It is possible to set appropriately so that the performance of the filtration membrane can be expressed highly.
  • the nanofiltration membrane unit 6 has different performance at each stage. In order to make the nanofiltration membrane units 6 different, it is easy to make the nanofiltration membranes different. In order to efficiently permeate the alkali metal and block other solutes in the present invention, the molecular weight and charge characteristics of the nanofiltration membrane are changed according to the supply water quality gradually changing in each stage of the nanofiltration membrane unit 6. It is possible to increase the separation efficiency by optimizing. In particular, since the permeation amount decreases due to pressure loss due to flow resistance and decrease in effective filtration pressure due to an increase in feed water concentration from the previous stage to the subsequent stage, the pure water permeability of the nanofiltration membrane in the subsequent stage is improved. The larger one is preferable.
  • the pure water feeding performance here can be measured by allowing pure water applied with pressure (usually 0.3 to 0.5 MPa) to pass through the nanofiltration membrane, and is measured at a standard temperature (usually 25 ° C.). It is a value obtained by measuring the membrane area and the amount of water permeated per unit time.
  • the concentration of the feed water increases as the latter stage increases, but not a small amount of alkali metal ions permeate through the nanofiltration membrane.
  • the ratio of the concentration of polyvalent ions such as ions) increases, and the alkali metal content of the permeated water also decreases from the previous stage. Therefore, it is preferable to use a nanofiltration membrane with higher separation performance as the latter stage.
  • the ratio of the sulfate ion permeability to the alkali metal permeability the ratio of the first stage nanofiltration membrane unit is smaller than the ratio of the final stage nanofiltration membrane unit, thereby making the present invention more efficient. Can be realized.
  • Such a nanofiltration membrane can be realized by increasing the pore diameter (fractionated molecular weight) while increasing the surface charge of the nanofiltration membrane in the subsequent stage as compared with the previous stage.
  • a method for increasing the surface charge for example, as shown in the literature (Photoinduced grafting of ultrafiltration membranes: comparison of poly (ether sulfone) and poly (sulfone), B. Kaeselev et al., Journal of Membrane Science) Examples thereof include a method in which radicals (active sites) are produced by UV, electron beam, plasma, etc., and graft polymerization is performed, and a method in which a polymer chain is cleaved with an oxidizing agent or the like.
  • a polycondensation reaction between a polyfunctional amine and a polyfunctional acid halide is performed from the viewpoint of achieving both high water permeability and separation performance and high potential for comprehensive membrane performance.
  • a composite semipermeable membrane having an ultrathin film layer of the obtained crosslinked polyamide on a microporous support membrane is preferred.
  • aliphatic polyamide is the main component (that is, the number of amide bonds of aliphatic polyamide is larger than that of aromatic polyamide), and high permeation performance is required.
  • an aromatic polyamide is a main component.
  • piperazine-based amines and derivatives thereof represented by the formula [I] are preferable, and piperazine, 2,5-dimethylpiperazine, 2-methylpiperazine, 2,6-dimethylpiperazine, 2,3,5- Examples include trimethylpiperazine, 2,5-diethylpiperazine, 2,3,5-triethylpiperazine, 2-n-propylpiperazine, 2,5-di-n-butylpiperazine and the like. Among them, it is particularly preferable to use piperazine or 2,5-dimethylpiperazine, which can obtain a nanofiltration membrane having higher solute removal performance and water permeation performance with a wide composition ratio.
  • R1 to R8 are selected from H, OH, COOH, SO 3 H, NH 2 or C1 to C4 linear or cyclic saturated or unsaturated aliphatic groups.
  • the polyfunctional amine is an amine having two or more amino groups in one molecule, and includes an o-aromatic diamine having two amino groups in the ortho position (o-). Those are preferred.
  • polyfunctional amines include m-aromatic diamines having two amino groups at the meta position (m-), p-aromatic diamines having two amino groups at the para position (p-), and aliphatic systems. At least one selected from the group consisting of amines and derivatives thereof, among them, having a dense and rigid structure, can provide a membrane having excellent blocking performance and water permeability performance, and further excellent durability and particularly heat resistance. It is also preferable that an easy m-aromatic diamine or p-aromatic diamine is contained.
  • o-phenylenediamine is preferably used as the o-aromatic diamine.
  • m-aromatic diamine m-phenylenediamine is preferable, but 3,5-diaminobenzoic acid, 2,6-diaminopyridine and the like can also be used.
  • p-aromatic diamine p-phenylenediamine is preferable, but 2,5-diaminobenzenesulfonic acid, p-xylylenediamine and the like can also be used.
  • the molar ratio of these polyfunctional amines in the film-forming stock solution can be appropriately selected depending on the amine and acid halide used. However, the higher the addition ratio of o-aromatic diamine, the better the water permeability. On the other hand, the blocking performance of the entire solute is reduced. Moreover, the separation performance of multivalent ions and monovalent ions is improved by increasing the number of aliphatic polyfunctional amines. This makes it possible to obtain the liquid separation membrane of the present invention that satisfies the desired water permeation performance, ion separation performance, and blocking performance of the entire solute.
  • the heat stability is lowered. Therefore, when heat resistance is important, the heat resistance can be improved by reducing the number of aliphatic amines.
  • polyfunctional acid halides are acid halides or polyfunctional acid anhydride halides having two or more carbonyl halide groups in one molecule, and the function of separating crosslinked polyamide by reaction with the above polyfunctional amine.
  • there is no particular limitation as long as it forms a layer For example, 1,3,5-cyclohexanetricarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3,5-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,3 -A mixture of benzenedicarboxylic acid and acid halide of 1,4-benzenedicarboxylic acid.
  • dicarboxylic acids and tricarboxylic acids represented by the formulas [II] and [III] are preferable, particularly good for economics, because the film-forming property is good, the entire solute blocking performance is uniform, and there are few defects and variations.
  • trimesic acid chloride which is an acid halide of 1,3,5-benzenetricarboxylic acid, is preferable.
  • R is selected from H or a C1-C3 hydrocarbon.
  • R is selected from H or a C1-C3 hydrocarbon.
  • the polyfunctional acid anhydride halide is a carbonyl halide of benzoic anhydride or phthalic anhydride having one or more acid anhydride moieties and one or more halogenated carbonyl groups in one molecule.
  • Trimellitic anhydride halides and derivatives thereof represented by the following general formula [IV] are preferably used.
  • X1 and X2 are any of C1-C3 linear or cyclic saturated or unsaturated aliphatic group, H, OH, COOH, SO 3 H, COF, COCl, COBr, COI To be elected.
  • an acid anhydride may be formed between X1 and X2.
  • X3 is selected from any of C1 to C3 linear or cyclic saturated or unsaturated aliphatic groups, H, OH, COOH, SO 3 H, COF, COCl, COBr, and COI.
  • Y is selected from H, F, Cl, Br, I or C1-C3 hydrocarbons.
  • the pressure of the feed water of each stage in addition to making the nanofiltration membranes of the front stage and the rear stage different from each other, it is also preferable to increase the pressure of the feed water of each stage.
  • the pressure is increased by a booster pump or the like to increase the processing performance of the subsequent stage.
  • the water permeability of the rear stage can be substantially increased.
  • the purified alkali metal salt can be separated and recovered by a crystallization operation induced by concentration of an aqueous solution, heating, cooling, or addition of a nucleating agent. It is preferred that the sulfate is removed. Therefore, the removal rate of magnesium sulfate is 90% or more when passing through a 2000 ppm magnesium sulfate aqueous solution at 25 ° C. and pH 6.5 and a 2000 ppm lithium chloride aqueous solution at 25 ° C. and pH 6.5 at an operating pressure of 0.5 MPa, preferably 95%.
  • % Or more more preferably 97% or more, and using a nanofiltration membrane having a lithium chloride removal rate of 70% or less, preferably 50% or less, more preferably 30% or less, depending on the total salt concentration. Separation of lithium salt and purification inhibitor is achieved with extremely high efficiency.
  • the reverse osmosis membrane method refers to a reverse osmosis membrane having an alkali metal removal rate of 95% or more.
  • the concentration unit 16 when using a concentration unit such as a distillation method or a membrane distillation method that uses thermal energy as a driving force for separation, as shown in FIG. 4, the concentration unit 16 at any point before entering the concentration unit 16 from raw water. It is also a preferred embodiment to take a method in which the supplied water is preheated by, for example, the heating unit 17 and the low-concentration water generated by concentration is recovered with cooling water.
  • the direct contact method which is one of the membrane distillation methods, is a method in which only water permeates from the high-temperature water to the cooling water through the membrane, and the high-temperature water is concentrated, which is very preferable for application of the present invention. .
  • the position of the heating unit 17 is not particularly limited as long as it is after the nanofiltration membrane unit 6 is removed from the raw water, but there is a pretreatment or the like before the supply to the concentration unit 16.
  • the performance may be affected if the pretreatment involves filtration or chemical reaction.
  • the temperature is high before the supply to the nanofiltration membrane unit, the water permeability and separation performance of the nanofiltration membrane may change significantly, and the concentrated water of the nanofiltration membrane will become high-temperature drainage. Because it leads to energy loss, design attention is required.
  • the heat generated by the pump is large, the temperature can be raised by the pump.
  • the purified alkali metal salt is recovered.
  • the purified alkali metal salt can be recovered by a known method of recovering potassium chloride by utilizing the temperature dependency of solubility or adding a poor solvent such as ethanol.
  • a lithium salt it is recovered as lithium carbonate, for example, by adding a carbonate to an aqueous solution, taking advantage of its low solubility compared to other alkali metal salts. This is because sodium carbonate and potassium carbonate have a sufficiently high solubility in water (20 g or more per 100 mL of water), whereas the solubility of lithium carbonate is only 1.33 g per 100 mL of water at 25 ° C, and the solubility is higher at higher temperatures. It uses the decline.
  • the residual liquid after the alkali metal is recovered by the recovery unit can be drained or can be refluxed to the supply water depending on the alkali metal content.
  • the nanofiltration membrane unit concentrated water has pressure energy, it is preferable to apply an energy recovery unit because it saves energy.
  • nanofiltration membrane unit concentrated water is generally drained because it contains a large amount of alkali metal production inhibitor, but the concentration of alkali metal ions to be recovered is less than the other components, but the concentration of raw water exceeds the concentration. Therefore, it can be reused as feed water after the concentration of the production inhibitor is reduced by ion exchange or adsorption.
  • the pretreatment unit 4 is not particularly limited, and can be appropriately selected such as removal of turbid components and sterilization depending on the raw aqueous state.
  • pretreating raw water and modifying it to a water quality suitable for the nanofiltration membrane supply water it is possible to reduce the burden on the nanofiltration membrane and to operate while stably holding the nanofiltration membrane.
  • turbidity treatment such as sand filtration, microfiltration membrane, ultrafiltration membrane
  • turbidity treatment such as sand filtration, microfiltration membrane, ultrafiltration membrane
  • a bactericidal agent Chlorine is preferably used as the disinfectant, and for example, chlorine gas or sodium hypochlorite may be added to the feed water as free chlorine so as to be in the range of 1 to 5 mg / l.
  • chlorine gas or sodium hypochlorite may be added to the feed water as free chlorine so as to be in the range of 1 to 5 mg / l.
  • the specific bactericidal agent does not have chemical durability.
  • the disinfectant ineffective near the feed water inlet side of the nanofiltration membrane unit 6.
  • free chlorine its concentration is measured, and the addition amount of chlorine gas and sodium hypochlorite is controlled based on this measured value, or a reducing agent such as sodium bisulfite is added.
  • a flocculant such as polyaluminum chloride, sulfate band, iron (III) chloride.
  • the agglomerated supply water is then subjected to sand filtration after settling on an inclined plate or the like, or by filtration through a microfiltration membrane or an ultrafiltration membrane in which a plurality of hollow fiber membranes are bundled. It can be set as the feed water suitable for letting the latter nanofiltration membrane unit 6 pass.
  • sand filtration when sand filtration is used for pretreatment, it is possible to apply gravity-type filtration that naturally flows down, or it is possible to apply pressure-type filtration in which a pressure tank is filled with sand. .
  • sand to be filled single-component sand can be applied.
  • anthracite, silica sand, garnet, pumice, and the like can be combined to increase filtration efficiency.
  • the microfiltration membrane and the ultrafiltration membrane are not particularly limited, and a flat membrane, a hollow fiber membrane, a tubular membrane, a pleated shape, or any other shape can be used as appropriate.
  • the material of the membrane is not particularly limited, and it is possible to use an inorganic material such as polyacrylonitrile, polyphenylene sulfone, polyphenylene sulfide sulfone, polyvinylidene fluoride, polypropylene, polyethylene, polysulfone, polyvinyl alcohol, cellulose acetate, or ceramic. it can. Moreover, even if it is a filtration system, any of the pressure filtration system which pressurizes and filters supply water, and the suction filtration system which sucks and filters the permeation
  • agglomerated membrane filtration or membrane-based activated sludge method in which a microfiltration membrane or an ultrafiltration membrane is immersed in a coagulation sedimentation tank or a biological treatment tank for filtration, may be applied preferable.
  • the organic matter when the supply water contains a lot of soluble organic matter, the organic matter can be decomposed by adding chlorine gas or sodium hypochlorite. Removal is possible.
  • a chelating agent such as an organic polymer electrolyte or sodium hexametaphosphate may be added, or exchanged with soluble ions using an ion exchange resin or the like.
  • iron or manganese when iron or manganese is present in a soluble state, it is preferable to use an aeration oxidation filtration method or a contact oxidation filtration method.
  • the alkali metal concentration in the nanofiltration membrane concentrated water is reduced by reducing the alkali metal concentration in the raw water. And the loss of alkali metal can be reduced.
  • alkaline earth metals have a high rejection rate in the nanofiltration membrane unit, so the concentration gradually increases, and depending on the operating conditions, it becomes a scale and precipitates on the surface of the nanofiltration membrane, reducing the performance of the nanofiltration membrane. Since the nanofiltration membrane is damaged, it has an advantage that it is difficult to precipitate the scale, which is preferable.
  • Concentration unit wastewater is water that has already been pretreated and may not require the same pretreatment process. In this case, by returning the concentrated unit waste water to the pretreatment water, the burden on the pretreatment process can be reduced, and energy saving and cost reduction can be achieved.
  • the present invention relates to a device for recovering alkali metals such as lithium and potassium from lake water, groundwater, industrial wastewater and the like, and a method for operating the same, and concentrates, separates by adding dilution water to raw water containing alkali metals, Alkali metals can be efficiently separated and recovered from water containing various solutes that are difficult to recover.

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Abstract

The present invention relates to a method for separating and recovering an alkali metal, which comprises: a step for obtaining nanofiltration membrane permeated water and nanofiltration membrane concentrated water by subjecting raw water that contains an alkali metal to separation by permeation with use of a nanofiltration membrane; a step for obtaining concentration unit concentrated water by subjecting the nanofiltration membrane permeated water to separation by permeation with use of a concentration unit; and a step of recovering at least some of the alkali metal that is contained in the concentration unit concentrated water.

Description

アルカリ金属分離回収方法およびアルカリ金属分離回収装置Alkali metal separation and recovery method and alkali metal separation and recovery apparatus
　本発明は、湖水、地下水、産業廃水などからリチウムやカリウムなどのアルカリ金属を回収する方法および装置に関するものである。 The present invention relates to a method and apparatus for recovering alkali metals such as lithium and potassium from lake water, groundwater, industrial wastewater and the like.
　近年、世界の経済発展に伴い、鉱物資源の需要拡大が著しい。しかし、半導体産業をはじめとして広く工業的に不可欠な鉱物資源のうち、地殻中の埋蔵量が多いものであっても、採掘や精錬のコストが高く経済的に採算が取れない資源や、特定地域に資源が局在化しており、これまで採掘が見合わせられてきたものも少なくなかった。一方で、環境問題も大きくクローズアップされてきており、循環型社会構築が望まれている。特に、二酸化炭素排出削減で注目を浴びている点から、電気自動車、それに使用されるモーターやバッテリー開発が加速されている。特に、バッテリーに関しては、リチウムイオン二次電池が、そのエネルギー密度、軽量さから電気自動車の主力バッテリーとして期待されている。リチウム化合物の用途として、例えば炭酸リチウムはリチウムイオン電池の電極材や耐熱ガラス添加剤のほか、弾性表面波フィルター向けにも用いられる。特に高純度のものは、携帯電話、カーナビ等フィルター及び発信器として使用されている。臭化リチウムの用途はビル、工場などの大型空調用吸収式冷凍機の冷媒吸収材として、水酸化リチウムの用途は自動車等のグリース及びリチウム電池（一次、二次）向けの原料である。金属リチウムの用途は一次電池の負極材としての箔及び合成ゴム触媒用のブチルリチウム向け原料などである。 In recent years, with the global economic development, the demand for mineral resources has increased significantly. However, among the mineral resources that are widely industrially indispensable including the semiconductor industry, even if the reserves in the crust are large, resources that are not economically profitable due to high mining and refining costs, and certain areas However, many resources have been postponed until now. On the other hand, environmental problems have been greatly highlighted, and the construction of a recycling society is desired. In particular, the development of electric vehicles, motors used in them, and batteries are accelerating because they are attracting attention for reducing carbon dioxide emissions. In particular, regarding batteries, lithium ion secondary batteries are expected as the main battery of electric vehicles because of their energy density and light weight. As an application of the lithium compound, for example, lithium carbonate is used for a surface acoustic wave filter in addition to an electrode material of a lithium ion battery and a heat-resistant glass additive. High purity products are used as filters and transmitters for mobile phones and car navigation systems. Lithium bromide is used as a refrigerant absorbent for large-scale air-conditioning absorption refrigerators in buildings and factories, and lithium hydroxide is used as a raw material for grease and lithium batteries (primary and secondary) for automobiles. Applications of metallic lithium include foil as a negative electrode material for primary batteries and raw materials for butyl lithium for synthetic rubber catalysts.
　リチウムは、塩湖かん水、および鉱石中に含まれており、生産コスト面で塩湖かん水からの資源回収が有利である。これらは、主にチリ，ボリビア、アルゼンチンに存在し、埋蔵量も多い。組成としては、大きく、塩化物かん水，硫酸塩かん水，炭酸塩かん水，カルシウムかん水に分類されるが、このなかで、もっとも資源量が多い硫酸塩かん水は、精製の過程で硫酸塩が難溶性の塩を形成したり、アルカリ土類金属塩や硫酸塩を多く含有したりするものが多く、効率的にリチウム回収することが困難であった。 リ チ ウ ム Lithium is contained in salt lake brine and ore, and it is advantageous to recover resources from salt lake brine in terms of production cost. These exist mainly in Chile, Bolivia, and Argentina, and have large reserves. The composition is largely classified into chloride brine, sulfate brine, carbonate brine, and calcium brine. Among these, sulfate brine, which has the largest amount of resources, has a low solubility of sulfate during the purification process. Many of them form salts or contain a lot of alkaline earth metal salts or sulfates, and it is difficult to efficiently recover lithium.
　これを解決する方策として、吸着剤による方法（特許文献１，２）などが提案されているが、コストが高いことが難点であり、低コストで安定的にリチウムを回収する技術として確立されていない。従来の低コスト方法としては、かん水を天日乾燥して、濃縮しつつ不純物を取り除く方法が挙げられるが、リチウム濃度が低い場合やアルカリ土類金属塩や硫酸塩の濃度が高い場合などには適用困難という問題があった。さらに、電気透析法や膜濾過法も検討されつつある（非特許文献１）が、実用化に至っていない。 As measures to solve this, methods using adsorbents (Patent Documents 1 and 2) and the like have been proposed. However, the cost is difficult, and it has been established as a technique for stably recovering lithium at a low cost. Absent. Conventional low-cost methods include drying the brine in the sun and removing impurities while concentrating, but when the lithium concentration is low or the alkaline earth metal salt or sulfate concentration is high, etc. There was a problem that it was difficult to apply. Furthermore, electrodialysis and membrane filtration are being studied (Non-Patent Document 1), but they have not been put into practical use.
　一方、同じアルカリ金属であるカリウムは，肥料をはじめ，食品，飼料，工業薬品，医薬品などに多用されている。現在、リチウムのような深刻な資源問題にはなっていないものの、発展途上国の爆発的な人口増加・経済成長に伴う資源の枯渇が懸念されている。 On the other hand, potassium, which is the same alkali metal, is frequently used for fertilizers, foods, feeds, industrial chemicals, pharmaceuticals and the like. Although it is not currently a serious resource problem like lithium, there is concern about the depletion of resources due to explosive population growth and economic growth in developing countries.
日本国特開2009-161794号公報Japanese Unexamined Patent Publication No. 2009-161794 日本国特開平4-293541号公報Japanese Laid-Open Patent Publication No.4-293541
　本発明の目的は、湖水、地下水、産業廃水などのリチウムやカリウムなどのアルカリ金属を含有する原水からアルカリ金属を効率的に回収する方法および装置を提供することにある。 An object of the present invention is to provide a method and an apparatus for efficiently recovering alkali metals from raw water containing alkali metals such as lithium and potassium such as lake water, groundwater, and industrial wastewater.
　前記課題を解決するために、本発明は以下の（１）～（７）に関する。 In order to solve the above problems, the present invention relates to the following (1) to (7).
　（１）ナノ濾過膜を用いてアルカリ金属を含有する原水を透過分離してナノ濾過膜透過水とナノ濾過膜濃縮水を得ること、濃縮ユニットを用いて該ナノ濾過膜透過水を透過分離して濃縮ユニット濃縮水を得ること、及び該濃縮ユニット濃縮水に含まれるアルカリ金属の少なくとも一部を回収すること、を含むアルカリ金属分離回収方法。 (1) The nanofiltration membrane is used to permeate and separate the raw water containing alkali metal to obtain nanofiltration membrane permeated water and nanofiltration membrane concentrated water, and the nanofiltration membrane permeated water is permeated and separated using a concentration unit. To obtain concentrated unit concentrated water, and recover at least part of the alkali metal contained in the concentrated unit concentrated water.
　（２）前記原水を前処理することで前処理水を得て、前記ナノ濾過膜を用いて該前処理水を透過分離することを特徴とする（１）に記載のアルカリ金属分離回収方法。 (2) The alkali metal separation and recovery method according to (1), wherein pretreatment water is obtained by pretreatment of the raw water, and the pretreatment water is permeated and separated using the nanofiltration membrane.
　（３）前記濃縮ユニットから排出された濃縮ユニット排水の少なくとも一部を、原水または前処理水に還流することを特徴とする（１）または（２）に記載のアルカリ金属分離回収方法。 (3) The alkali metal separation and recovery method according to (1) or (2), wherein at least a part of the concentration unit drainage discharged from the concentration unit is returned to raw water or pretreated water.
　（４）前記前処理が除濁処理であって、前記濃縮ユニット排水の少なくとも一部を用いて、除濁処理設備を洗浄することを特徴とする（２）または（３）に記載のアルカリ金属分離回収方法。 (4) The alkali metal according to (2) or (3), wherein the pretreatment is a turbidity treatment, and the turbidity treatment facility is washed using at least a part of the drainage of the concentration unit. Separation and recovery method.
　（５）前記濃縮ユニットが、逆浸透膜ユニット、蒸留ユニット、膜蒸留ユニットのいずれかで構成されることを特徴とする（１）～（４）のいずれかに記載のアルカリ金属分離回収方法。 (5) The alkali metal separation and recovery method according to any one of (1) to (4), wherein the concentration unit comprises any one of a reverse osmosis membrane unit, a distillation unit, and a membrane distillation unit.
　（６）前記濃縮ユニットが、濃縮ユニットに供給される供給水の温度よりも低温の原水を用いて低濃度水を冷却回収する機構からなることを特徴とする（４）または（５）に記載のアルカリ金属分離回収方法。 (6) The concentration unit includes a mechanism that cools and recovers low-concentration water using raw water having a temperature lower than the temperature of the supply water supplied to the concentration unit. Alkali metal separation and recovery method.
　（７）ナノ濾過膜を用いてアルカリ金属を含有する原水を透過分離してナノ濾過膜透過水とナノ濾過膜濃縮水を得るナノ濾過膜ユニットと、該ナノ濾過膜透過水を透過分離して濃縮ユニット濃縮水を得る濃縮ユニットと、該濃縮ユニット濃縮水に含まれるアルカリ金属の少なくとも一部を回収する回収ユニットとを備えたアルカリ金属分離回収装置。 (7) A nanofiltration membrane unit that obtains nanofiltration membrane permeated water and nanofiltration membrane concentrated water by permeating and separating raw water containing alkali metal using a nanofiltration membrane, and permeating and separating the nanofiltration membrane permeated water. An alkali metal separation and recovery apparatus comprising: a concentration unit for obtaining concentrated unit concentrated water; and a recovery unit for recovering at least a part of the alkali metal contained in the concentrated unit concentrated water.
　本発明によって、様々な溶質が共存する原水からリチウムやカリウムなどのアルカリ金属を効率的に回収することが可能となる。 The present invention makes it possible to efficiently recover alkali metals such as lithium and potassium from raw water in which various solutes coexist.
図１は、本発明に係る、アルカリ金属分離回収方法の一実施態様を示す概略フロー図である。FIG. 1 is a schematic flowchart showing one embodiment of the alkali metal separation and recovery method according to the present invention. 図２は、本発明に係る、濃縮ユニット排水を供給水に還流するアルカリ金属分離回収方法の一実施態様を示す概略フロー図である。FIG. 2 is a schematic flow diagram showing an embodiment of the alkali metal separation and recovery method for refluxing the concentrated unit waste water to the supply water according to the present invention. 図３は、本発明に係る、濃縮ユニット排水を前処理水に還流するアルカリ金属分離回収方法の一実施態様を示す概略フロー図である。FIG. 3 is a schematic flow diagram showing one embodiment of an alkali metal separation and recovery method for refluxing concentrated unit waste water to pretreated water according to the present invention. 図４は、本発明に係る、濃縮ユニットが熱利用型の濃縮ユニットであるアルカリ金属分離回収方法の一実施態様を示す概略フロー図である。FIG. 4 is a schematic flow diagram showing one embodiment of the alkali metal separation and recovery method according to the present invention, in which the concentration unit is a heat utilization type concentration unit.
　以下、本発明の望ましい実施の形態の一例を、図面を用いて説明する。ただし、本発明の範囲はこれらの実施態様に限られるものではない。 Hereinafter, an example of a preferred embodiment of the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to these embodiments.
　本発明のアルカリ金属回収の実施フローの一例を図１に示す。図１に示すアルカリ金属回収装置では、アルカリ金属を含有する原水１が原水タンク２で一旦貯留された後、供給ポンプ３によって前処理ユニット４で処理され、前処理された供給水は昇圧ポンプ５でナノ濾過膜ユニット６に送られ、アルカリ金属が透過分離されたナノ濾過膜透過水とナノ濾過膜濃縮水７を得る。ナノ濾過膜ユニット６の透過水は、昇圧ポンプ８で濃縮ユニット９に送られ、アルカリ金属が低濃度となる濃縮ユニット排水１０とアルカリ金属が濃縮された濃縮ユニット濃縮水１１を得る。濃縮ユニット濃縮水１１は、回収ユニット１２に送られ、アルカリ金属１３が回収される（実施形態（１）及び（２））。 An example of the execution flow of the alkali metal recovery of the present invention is shown in FIG. In the alkali metal recovery apparatus shown in FIG. 1, raw water 1 containing alkali metal is temporarily stored in a raw water tank 2, then processed by a pretreatment unit 4 by a supply pump 3, and the pretreated supply water is a booster pump 5. Is sent to the nanofiltration membrane unit 6 to obtain nanofiltration membrane permeated water and nanofiltration membrane concentrated water 7 from which alkali metal is permeated and separated. The permeated water of the nanofiltration membrane unit 6 is sent to the concentrating unit 9 by the booster pump 8 to obtain the concentrating unit waste water 10 in which the alkali metal has a low concentration and the concentrated unit concentrated water 11 in which the alkali metal is concentrated. The concentrated unit concentrated water 11 is sent to the recovery unit 12 to recover the alkali metal 13 (embodiments (1) and (2)).
　本発明のようにアルカリ金属を含有する原水をナノ濾過膜で処理する場合、供給水側のアルカリ金属が他のアルカリ土類金属などに比べてサイズが小さいため、ナノ濾過膜で阻止されずに選択的に透過側に移動するものの、通常、その透過水におけるアルカリ金属濃度が原水におけるアルカリ金属濃度以上の濃度になることはないため、ナノ濾過膜の透過水を濃縮ユニットで濃縮することによって、後処理の回収ユニットにおいてアルカリ金属を効率的に回収することができる（実施形態（１）の効果）。 When raw water containing alkali metal is treated with a nanofiltration membrane as in the present invention, the size of the alkali metal on the supply water side is smaller than other alkaline earth metals, so that it is not blocked by the nanofiltration membrane. Although it selectively moves to the permeate side, usually the alkali metal concentration in the permeate does not exceed the alkali metal concentration in the raw water, so by concentrating the permeate of the nanofiltration membrane with a concentration unit, Alkali metal can be efficiently recovered in the post-processing recovery unit (effect of the embodiment (1)).
　本発明の対象となるアルカリ金属は、少なくともリチウムを含むものであれば好ましく、本発明の方法を実施する塩湖かん水などにおいては、リチウム以外にナトリウム、カリウム、ルビジウム、セシウムなどのアルカリ金属のうち少なくとも一つの金属と、マグネシウム、カルシウム、ストロンチウムなどのアルカリ土類金属の他、典型元素（アルミニウム、スズ、鉛など）、遷移元素（鉄、銅、コバルト、マンガンなど）、および１種以上の共役塩基（例えば塩化物イオン、硝酸イオン、硫酸イオン、炭酸イオン、酢酸イオンなど）との塩からなる化合物が溶存している。これらの各成分の濃度は特に限定されないが、分離回収の効率の点から希釈後の供給水のリチウムイオン濃度が0.5ppm以上10000ppm以下の範囲であることが好ましく、より好ましくは5ppm以上5000ppm以下の範囲であり、さらに好ましくは50ppm以上2000ppm以下の範囲である水溶液を原水とすることが好ましい。 The alkali metal that is the subject of the present invention is preferably one containing at least lithium, and in salt lake brine etc. for carrying out the method of the present invention, among alkali metals such as sodium, potassium, rubidium, cesium and the like in addition to lithium. At least one metal, alkaline earth metal such as magnesium, calcium, strontium, typical elements (aluminum, tin, lead, etc.), transition elements (iron, copper, cobalt, manganese, etc.), and one or more conjugates A compound composed of a salt with a base (for example, chloride ion, nitrate ion, sulfate ion, carbonate ion, acetate ion, etc.) is dissolved. The concentration of each of these components is not particularly limited, but from the viewpoint of separation and recovery efficiency, the lithium ion concentration of the feed water after dilution is preferably in the range of 0.5 ppm to 10,000 ppm, more preferably 5 ppm to 5000 ppm. An aqueous solution having a range of 50 ppm to 2000 ppm is preferably used as the raw water.
　ここで、例えば炭酸リチウムや塩化カリウムなど、所望の精製アルカリ金属塩を後処理で分離回収するにあたり、その精製阻害物質としては難溶性塩を生成しやすいアルカリ土類金属塩や硫酸塩、地殻中の有機物などが挙げられ、マグネシウム塩および／または硫酸塩などが例示される。本発明では、アルカリ金属塩水溶液から精製アルカリ金属塩を分離回収する効率の観点から、供給水となるアルカリ金属塩水溶液中のマグネシウムイオン濃度がリチウムイオン濃度に比して１０００倍以下であることが好ましく、より好ましくは５００倍以下、さらに好ましくは１００倍以下であると効率的である。 Here, for example, when a desired purified alkali metal salt such as lithium carbonate or potassium chloride is separated and recovered by post-treatment, the purification inhibitor may be an alkaline earth metal salt or sulfate that easily produces a hardly soluble salt, Examples of such organic substances include magnesium salts and / or sulfates. In the present invention, from the viewpoint of the efficiency of separating and recovering the purified alkali metal salt from the alkali metal salt aqueous solution, the magnesium ion concentration in the alkali metal salt aqueous solution to be supplied water is 1000 times or less than the lithium ion concentration. The efficiency is preferably 500 times or less, more preferably 100 times or less, more preferably 100 times or less.
　本発明では、ナノ濾過膜ユニットで精製阻害物質を除去する処理工程を行うにあたり、アルカリ金属塩を含む水溶液中のマグネシウムイオン濃度が、該水溶液中のリチウムイオン濃度に比して７倍以下となるまで、ナノ濾過膜ユニットによる除去処理を行うことが好ましい。この比が７倍を超えると、精製アルカリ金属塩の回収効率が著しく低下する。なお、この時の精製阻害物質重量は、マグネシウムイオンや硫酸イオンなどのイオン換算重量で計算される。また、リチウムイオン換算重量および精製阻害物質重量は、例えばイオンクロマトグラフ測定によりアルカリ金属塩を含む水溶液の各種イオン濃度を定量することで求められる。 In the present invention, when performing the treatment step of removing the purification inhibitor with the nanofiltration membrane unit, the magnesium ion concentration in the aqueous solution containing the alkali metal salt is 7 times or less than the lithium ion concentration in the aqueous solution. Until then, it is preferable to perform the removal treatment by the nanofiltration membrane unit. If this ratio exceeds 7 times, the recovery efficiency of the purified alkali metal salt is significantly reduced. The weight of the purification inhibiting substance at this time is calculated based on the weight in terms of ions such as magnesium ions and sulfate ions. The weight in terms of lithium ion and the weight of the purification inhibitor can be determined by quantifying various ion concentrations in an aqueous solution containing an alkali metal salt, for example, by ion chromatography.
　原水中の精製阻害物質の含有量は、精製阻害物質の組成や原水の性状によって異なるが、例えば塩湖かん水ではマグネシウムイオン、硫酸イオンがそれぞれ100ppm以上30000ppm以下の範囲で含まれている。 The content of the purification inhibitor in the raw water varies depending on the composition of the purification inhibitor and the properties of the raw water. For example, salt lake brine contains magnesium ions and sulfate ions in the range of 100 ppm to 30,000 ppm.
　ここでいうナノ濾過膜とは、ＩＵＰＡＣで「２ｎｍより小さい程度の粒子や高分子が阻止される圧力駆動の膜」と定義される膜であるが、本発明への適用に効果的なナノ濾過膜は、膜表面に荷電を有し、細孔による分離（サイズ分離）と膜表面の荷電による静電気的な分離の組み合わせによって特にイオンの分離効率を向上させたものが好ましく、回収目的とするアルカリ金属イオンとそのほかの荷電特性が異なるイオンを荷電によって分離しつつ、サイズ分離による高分子類の除去が可能なナノ濾過膜を適用することが好ましい。 The nanofiltration membrane referred to here is a membrane defined by IUPAC as “a pressure-driven membrane in which particles and polymers of a size smaller than 2 nm are blocked”, but is effective for application to the present invention. Preferably, the membrane has a charge on the membrane surface, and has improved ion separation efficiency by a combination of separation by pores (size separation) and electrostatic separation by charge on the membrane surface. It is preferable to apply a nanofiltration membrane that is capable of removing polymers by size separation while separating metal ions and other ions having different charge characteristics by charging.
　本発明に適したナノ濾過膜としては、特に0.5MPaの操作圧力で25℃、pH6.5の1000ppmイソプロピルアルコール水溶液および25℃、pH6.5の1000ppmグルコース水溶液をそれぞれ透過させた時のグルコース除去率が９０％以上であり、かつ、グルコース除去率とイソプロピルアルコール除去率の差が３０％以上であるナノ濾過膜を用いることで、総塩濃度によらずアルカリ金属塩、中でもリチウム塩と精製阻害物質の分離が極めて高効率で達成されるため特に好ましい。 As a nanofiltration membrane suitable for the present invention, the glucose removal rate when a 1000 ppm isopropyl alcohol aqueous solution at 25 ° C. and pH 6.5 and a 1000 ppm glucose aqueous solution at 25 ° C. and pH 6.5 were permeated at an operating pressure of 0.5 MPa, respectively. Is 90% or more, and a nanofiltration membrane having a difference between glucose removal rate and isopropyl alcohol removal rate of 30% or more is used, regardless of the total salt concentration, alkali metal salts, especially lithium salts and purification inhibitors Is particularly preferred since the separation of is achieved with very high efficiency.
　また、ナノ濾過膜ユニット６は、ナノ濾過膜をモジュール化したものから構成され、例えば、スパイラル型のナノ濾過膜エレメントを単数もしくは複数連結して容器に収納したものやそれを直列や並列に接続したものを指す。 The nanofiltration membrane unit 6 is composed of modularized nanofiltration membranes. For example, one or a plurality of spiral nanofiltration membrane elements connected to each other and housed in a container, or connected in series or in parallel. Refers to
　ナノ濾過膜ユニット６に関しては、１ステージ処理も可能であるし、回収率を高める場合は、濃縮水をさらに次のナノ濾過膜ユニット６で処理する、いわゆるマルチステージにすることも問題なく、ナノ濾過膜の性能を高く発現できるように適宜設定することが可能である。 With respect to the nanofiltration membrane unit 6, one-stage processing is also possible, and in the case of increasing the recovery rate, there is no problem in making the so-called multistage in which the concentrated water is further processed by the next nanofiltration membrane unit 6. It is possible to set appropriately so that the performance of the filtration membrane can be expressed highly.
　マルチステージにする場合、それぞれのステージで異なる性能のナノ濾過膜ユニット６にすると好適である。ナノ濾過膜ユニット６が異なるようにするためには、ナノ濾過膜を異なるようにすることが簡便である。本発明においてアルカリ金属を効率的に透過させて他の溶質を阻止するために、ナノ濾過膜ユニット６の各ステージにおいて徐々に変化する供給水質に応じて、ナノ濾過膜の分画分子量や荷電特性を最適化することによって分離効率を高めることが可能となる。特に、前ステージから後ステージになるに従って、流動抵抗による圧力損失や供給水濃度の上昇による有効濾過圧力減少によって、透過量が減少するため、後ステージのナノ濾過膜の純水透水性能が前ステージよりも大きい方が好ましい。 In the case of a multi-stage, it is preferable that the nanofiltration membrane unit 6 has different performance at each stage. In order to make the nanofiltration membrane units 6 different, it is easy to make the nanofiltration membranes different. In order to efficiently permeate the alkali metal and block other solutes in the present invention, the molecular weight and charge characteristics of the nanofiltration membrane are changed according to the supply water quality gradually changing in each stage of the nanofiltration membrane unit 6. It is possible to increase the separation efficiency by optimizing. In particular, since the permeation amount decreases due to pressure loss due to flow resistance and decrease in effective filtration pressure due to an increase in feed water concentration from the previous stage to the subsequent stage, the pure water permeability of the nanofiltration membrane in the subsequent stage is improved. The larger one is preferable.
　ここでいう純水送水性能とは、ナノ濾過膜に圧力（通常０．３～０．５ＭＰａ）をかけた純水を透過させることによって測定することができ、標準温度（通常２５℃）において単位膜面積、単位時間あたりに透過した水の量を測定して得られる値である。 The pure water feeding performance here can be measured by allowing pure water applied with pressure (usually 0.3 to 0.5 MPa) to pass through the nanofiltration membrane, and is measured at a standard temperature (usually 25 ° C.). It is a value obtained by measuring the membrane area and the amount of water permeated per unit time.
　さらに、供給水の濃度は後ステージほど上昇するが、アルカリ金属イオンは少なくない量がナノ濾過膜を透過するため、後ステージの供給水ほどアルカリ金属濃度に対するその他の溶質（アルカリ土類金属や硫酸イオンのような多価イオン）濃度の比率が高くなり、透過水のアルカリ金属含有率も前段より低下する。そのため、後ステージほど分離性能の高いナノ濾過膜を用いることが好ましい。具体的には、アルカリ金属透過率に対する硫酸イオン透過率の比について、第１ステージのナノ濾過膜ユニットにおける比が最終ステージのナノ濾過膜ユニットにおける比よりも小さくすることによって、本発明をより効率的に実現することが可能となる。このようなナノ濾過膜は、前ステージよりも後ステージのナノ濾過膜の表面荷電を強くしつつ、細孔径（分画分子量）を大きめにすることによって、実現することができる。表面荷電を強くする方法としては、例えば、文献（Photoinduced grafting of ultrafiltration membranes: comparison of poly(ether sulfone) and poly(sulfone), B. Kaeselevら，ジャーナルオブメンブレンサイエンス）に示されるように膜表面にＵＶ、また、電子線、プラズマなどでラジカル（活性点）をつくってグラフト重合させるといった方法や、酸化剤などで高分子鎖を断裂するなどの方法が例として挙げられる。また、本発明に適用するナノ濾過膜としては、透水性能と分離性能を両立し、総合的な膜性能のポテンシャルが高いという観点から、多官能アミンと多官能酸ハロゲン化物との重縮合反応により得られる架橋ポリアミドの超薄膜層を微多孔性支持膜上に有してなる複合半透膜であることが好ましい。 Furthermore, the concentration of the feed water increases as the latter stage increases, but not a small amount of alkali metal ions permeate through the nanofiltration membrane. The ratio of the concentration of polyvalent ions such as ions) increases, and the alkali metal content of the permeated water also decreases from the previous stage. Therefore, it is preferable to use a nanofiltration membrane with higher separation performance as the latter stage. Specifically, regarding the ratio of the sulfate ion permeability to the alkali metal permeability, the ratio of the first stage nanofiltration membrane unit is smaller than the ratio of the final stage nanofiltration membrane unit, thereby making the present invention more efficient. Can be realized. Such a nanofiltration membrane can be realized by increasing the pore diameter (fractionated molecular weight) while increasing the surface charge of the nanofiltration membrane in the subsequent stage as compared with the previous stage. As a method for increasing the surface charge, for example, as shown in the literature (Photoinduced grafting of ultrafiltration membranes: comparison of poly (ether sulfone) and poly (sulfone), B. Kaeselev et al., Journal of Membrane Science) Examples thereof include a method in which radicals (active sites) are produced by UV, electron beam, plasma, etc., and graft polymerization is performed, and a method in which a polymer chain is cleaved with an oxidizing agent or the like. In addition, as a nanofiltration membrane applied to the present invention, a polycondensation reaction between a polyfunctional amine and a polyfunctional acid halide is performed from the viewpoint of achieving both high water permeability and separation performance and high potential for comprehensive membrane performance. A composite semipermeable membrane having an ultrathin film layer of the obtained crosslinked polyamide on a microporous support membrane is preferred.
　さらに、高分離効率が求められる前ステージにおいては、脂肪族系ポリアミドを主成分（すなわち、脂肪族ポリアミドのアミド結合数が芳香族ポリアミドのアミド結合よりも多い。）とし、高透過性能が求められる後ステージのナノ濾過膜としては、芳香族系ポリアミドを主成分とすることが好ましい。 Furthermore, in the previous stage where high separation efficiency is required, aliphatic polyamide is the main component (that is, the number of amide bonds of aliphatic polyamide is larger than that of aromatic polyamide), and high permeation performance is required. As the nanofiltration membrane of the subsequent stage, it is preferable that an aromatic polyamide is a main component.
　脂肪族アミンとしては、[I]式に示すようなピペラジン系アミン及びその誘導体が好ましく、ピペラジン、２，５－ジメチルピペラジン、２－メチルピペラジン、２，６－ジメチルピペラジン、２，３，５－トリメチルピペラジン、２，５－ジエチルピペラジン、２，３，５－トリエチルピペラジン、２－ｎ－プロピルピペラジン、２,５－ジ－ｎ－ブチルピペラジンなどが例示される。中でもより高い溶質除去性能、水透過性能を有するナノ濾過膜を幅広い組成比で得ることができるピペラジンや２，５－ジメチルピペラジンを用いることが特に好ましい。 As the aliphatic amine, piperazine-based amines and derivatives thereof represented by the formula [I] are preferable, and piperazine, 2,5-dimethylpiperazine, 2-methylpiperazine, 2,6-dimethylpiperazine, 2,3,5- Examples include trimethylpiperazine, 2,5-diethylpiperazine, 2,3,5-triethylpiperazine, 2-n-propylpiperazine, 2,5-di-n-butylpiperazine and the like. Among them, it is particularly preferable to use piperazine or 2,5-dimethylpiperazine, which can obtain a nanofiltration membrane having higher solute removal performance and water permeation performance with a wide composition ratio.
Figure JPOXMLDOC01-appb-C000001
Figure JPOXMLDOC01-appb-C000001
［I］式中、Ｒ１～Ｒ８はＨ，ＯＨ，ＣＯＯＨ，ＳＯ３Ｈ，ＮＨ２またはＣ１～Ｃ４の直鎖状あるいは環状の飽和、不飽和脂肪族基のいずれかから選ばれる。 [I] In the formula, R1 to R8 are selected from H, OH, COOH, SO 3 H, NH 2 or C1 to C4 linear or cyclic saturated or unsaturated aliphatic groups.
　芳香族系ポリアミドの場合、多官能アミンとしては、一分子中に２個以上のアミノ基を有するアミンであり、オルト位（ｏ－）に２個のアミノ基を有するｏ－芳香族ジアミンを含むものが好ましい。さらに多官能アミンとしては、メタ位（ｍ－）に２個のアミノ基を有するｍ－芳香族ジアミン、パラ位（ｐ－）に２個のアミノ基を有するｐ－芳香族ジアミンならびに脂肪族系アミンおよびその誘導体からなる群から選ばれる少なくとも１種、中でも、緻密で剛直な構造を有するために阻止性能と透水性能のポテンシャルに優れ、さらに耐久性、特に耐熱性に優れた膜を得ることが容易なｍ－芳香族ジアミンやｐ－芳香族ジアミンを含んでいることも好ましい。 In the case of an aromatic polyamide, the polyfunctional amine is an amine having two or more amino groups in one molecule, and includes an o-aromatic diamine having two amino groups in the ortho position (o-). Those are preferred. In addition, polyfunctional amines include m-aromatic diamines having two amino groups at the meta position (m-), p-aromatic diamines having two amino groups at the para position (p-), and aliphatic systems. At least one selected from the group consisting of amines and derivatives thereof, among them, having a dense and rigid structure, can provide a membrane having excellent blocking performance and water permeability performance, and further excellent durability and particularly heat resistance. It is also preferable that an easy m-aromatic diamine or p-aromatic diamine is contained.
　ここで、ｏ－芳香族ジアミンとして好ましく用いられるのはｏ－フェニレンジアミンである。ｍ－芳香族ジアミンとしては、ｍ－フェニレンジアミンが好ましいが、３，５－ジアミノ安息香酸や２，６－ジアミノピリジン等を用いることもできる。ｐ－芳香族ジアミンとしてはｐ－フェニレンジアミンが好ましいが、２，５－ジアミノベンゼンスルホン酸やｐ－キシリレンジアミン等を用いることもできる。 Here, o-phenylenediamine is preferably used as the o-aromatic diamine. As the m-aromatic diamine, m-phenylenediamine is preferable, but 3,5-diaminobenzoic acid, 2,6-diaminopyridine and the like can also be used. As the p-aromatic diamine, p-phenylenediamine is preferable, but 2,5-diaminobenzenesulfonic acid, p-xylylenediamine and the like can also be used.
　これら多官能アミンの製膜原液中におけるモル比は、用いるアミンおよび酸ハロゲン化物によって適宜最適な組成比を選ぶことができるが、ｏ－芳香族ジアミンの添加比率が高いほど透水性は向上し、反面、溶質全体の阻止性能は低下する。また、脂肪族多官能アミンを多くすることで、多価イオンと一価イオンの分離性能が向上する。これによって目的とする透水性能とイオン分離性能、溶質全体の阻止性能を満足する本発明の液体分離膜を得ることが可能となる。 The molar ratio of these polyfunctional amines in the film-forming stock solution can be appropriately selected depending on the amine and acid halide used. However, the higher the addition ratio of o-aromatic diamine, the better the water permeability. On the other hand, the blocking performance of the entire solute is reduced. Moreover, the separation performance of multivalent ions and monovalent ions is improved by increasing the number of aliphatic polyfunctional amines. This makes it possible to obtain the liquid separation membrane of the present invention that satisfies the desired water permeation performance, ion separation performance, and blocking performance of the entire solute.
　また、アミン成分として脂肪族アミンが多いと耐熱安定性が低下するため、耐熱性を重視したい場合は、脂肪族アミンを少なくすることによって耐熱性の向上を達成することもできる。 In addition, when there are a large number of aliphatic amines as the amine component, the heat stability is lowered. Therefore, when heat resistance is important, the heat resistance can be improved by reducing the number of aliphatic amines.
　一方、多官能酸ハロゲン化物としては、一分子中に２個以上のハロゲン化カルボニル基を有する酸ハロゲン化物や多官能酸無水物ハロゲン化物で、上記多官能アミンとの反応により架橋ポリアミドの分離機能層を形成するものであれば特に限定されるものではない。例えば1,3,5-シクロヘキサントリカルボン酸、1,3-シクロヘキサンジカルボン酸、1,4-シクロヘキサンジカルボン酸、1,3,5-ベンゼントリカルボン酸、1,２,4-ベンゼントリカルボン酸、1,3-ベンゼンジカルボン酸、1,4-ベンゼンジカルボン酸の酸ハロゲン化物の混合物などである。中でも、製膜性が良好で、全溶質阻止性能が均質で欠陥やばらつきの少ない膜を得やすい、[II]式、[III]式で表されるジカルボン酸やトリカルボン酸が好ましく、とくに、経済性、取り扱い易さ、反応の容易さ等の点から、1,3,5-ベンゼントリカルボン酸の酸ハロゲン化物であるトリメシン酸クロライドが好ましい。 On the other hand, polyfunctional acid halides are acid halides or polyfunctional acid anhydride halides having two or more carbonyl halide groups in one molecule, and the function of separating crosslinked polyamide by reaction with the above polyfunctional amine. There is no particular limitation as long as it forms a layer. For example, 1,3,5-cyclohexanetricarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3,5-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,3 -A mixture of benzenedicarboxylic acid and acid halide of 1,4-benzenedicarboxylic acid. Among them, dicarboxylic acids and tricarboxylic acids represented by the formulas [II] and [III] are preferable, particularly good for economics, because the film-forming property is good, the entire solute blocking performance is uniform, and there are few defects and variations. From the viewpoints of properties, ease of handling, reaction, and the like, trimesic acid chloride, which is an acid halide of 1,3,5-benzenetricarboxylic acid, is preferable.
Figure JPOXMLDOC01-appb-C000002
Figure JPOXMLDOC01-appb-C000002
［II］式中、ＲはＨまたはＣ１～Ｃ３の炭化水素から選ばれる。 [II] In the formula, R is selected from H or a C1-C3 hydrocarbon.
Figure JPOXMLDOC01-appb-C000003
Figure JPOXMLDOC01-appb-C000003
［III］式中、ＲはＨまたはＣ１～Ｃ３の炭化水素から選ばれる。 [III] In the formula, R is selected from H or a C1-C3 hydrocarbon.
　また、多官能酸無水物ハロゲン化物としては、一分子中に１個以上の酸無水物部分と１個以上のハロゲン化カルボニル基を有し、無水安息香酸、無水フタル酸のカルボニルハロゲン化物である、下記一般式[IV]で表されるトリメリット酸無水物ハロゲン化物及びその誘導体が好ましく用いられる。 The polyfunctional acid anhydride halide is a carbonyl halide of benzoic anhydride or phthalic anhydride having one or more acid anhydride moieties and one or more halogenated carbonyl groups in one molecule. Trimellitic anhydride halides and derivatives thereof represented by the following general formula [IV] are preferably used.
Figure JPOXMLDOC01-appb-C000004
Figure JPOXMLDOC01-appb-C000004
［IV］式中、Ｘ１およびＸ２は、Ｃ１～Ｃ３の直鎖状あるいは環状の飽和、不飽和脂肪族基、Ｈ，ＯＨ，ＣＯＯＨ，ＳＯ３Ｈ，ＣＯＦ，ＣＯＣｌ，ＣＯＢｒ，ＣＯＩのいずれかから選ばれる。または、Ｘ１とＸ２との間で酸無水物を形成していても良い。Ｘ３はＣ１～Ｃ３の直鎖状あるいは環状の飽和、不飽和脂肪族基、Ｈ，ＯＨ，ＣＯＯＨ，ＳＯ３Ｈ，ＣＯＦ，ＣＯＣｌ，ＣＯＢｒ，ＣＯＩのいずれかから選ばれる。ＹはＨ，Ｆ，Ｃｌ，Ｂｒ，ＩまたはＣ１～Ｃ３の炭化水素から選ばれる。 [IV] In the formula, X1 and X2 are any of C1-C3 linear or cyclic saturated or unsaturated aliphatic group, H, OH, COOH, SO 3 H, COF, COCl, COBr, COI To be elected. Alternatively, an acid anhydride may be formed between X1 and X2. X3 is selected from any of C1 to C3 linear or cyclic saturated or unsaturated aliphatic groups, H, OH, COOH, SO 3 H, COF, COCl, COBr, and COI. Y is selected from H, F, Cl, Br, I or C1-C3 hydrocarbons.
　ところで、前ステージと後ステージのナノ濾過膜を異なるようにする以外に、それぞれのステージの供給水を昇圧することも好ましい。すなわち、前ステージの濃縮水を後ステージの供給水とするにあたって、ブースターポンプなどで昇圧し、後ステージの処理性能を上げるという方法である。これによって、後ステージの透水性を実質的に上げることが可能となる。 Incidentally, in addition to making the nanofiltration membranes of the front stage and the rear stage different from each other, it is also preferable to increase the pressure of the feed water of each stage. In other words, when the concentrated water of the previous stage is used as the supply water of the subsequent stage, the pressure is increased by a booster pump or the like to increase the processing performance of the subsequent stage. As a result, the water permeability of the rear stage can be substantially increased.
　さらに、一般に、前記精製アルカリ金属塩は水溶液の濃縮や加熱、冷却、または核化剤の添加などで誘起される、晶析操作によって分離回収が可能であることから、これらを阻害するマグネシウム塩および／または硫酸塩が除去されることが好ましい。そこで、0.5MPaの操作圧力で25℃、pH6.5の2000ppm硫酸マグネシウム水溶液および25℃、pH6.5の2000ppm塩化リチウム水溶液をそれぞれ透過させた時の硫酸マグネシウム除去率が９０％以上、好ましくは９５％以上、さらに好ましくは９７％以上であり、かつ、塩化リチウム除去率が７０％以下、好ましくは５０％以下、さらに好ましくは３０％以下であるナノ濾過膜を用いることで、総塩濃度によらずリチウム塩と精製阻害物質の分離が極めて高効率で達成される。 Furthermore, in general, the purified alkali metal salt can be separated and recovered by a crystallization operation induced by concentration of an aqueous solution, heating, cooling, or addition of a nucleating agent. It is preferred that the sulfate is removed. Therefore, the removal rate of magnesium sulfate is 90% or more when passing through a 2000 ppm magnesium sulfate aqueous solution at 25 ° C. and pH 6.5 and a 2000 ppm lithium chloride aqueous solution at 25 ° C. and pH 6.5 at an operating pressure of 0.5 MPa, preferably 95%. % Or more, more preferably 97% or more, and using a nanofiltration membrane having a lithium chloride removal rate of 70% or less, preferably 50% or less, more preferably 30% or less, depending on the total salt concentration. Separation of lithium salt and purification inhibitor is achieved with extremely high efficiency.
　また、濃縮ユニットは、例えば、蒸留、膜分離、吸脱着、イオン交換、など、様々な方法を適用可能であるが、アルカリ金属は不揮発性でサイズが非常に小さいため、逆浸透膜法、蒸留法、膜蒸留法（膜を利用した純水分離・濃縮方法）、を用いて濃縮すると効率的で好ましく、とくに逆浸透膜法が、アルカリ金属阻止性能や省エネの観点から好ましい（実施形態（５））。なお、ここで、逆浸透膜とは、アルカリ金属除去率９５％以上の逆浸透膜のことを指す。 In addition, various methods such as distillation, membrane separation, adsorption / desorption, and ion exchange can be applied to the concentration unit. However, since alkali metals are non-volatile and very small in size, the reverse osmosis membrane method, distillation Method, membrane distillation method (pure water separation / concentration method using membrane) is efficient and preferable, and reverse osmosis membrane method is particularly preferable from the viewpoint of alkali metal blocking performance and energy saving (Embodiment (5 )). Here, the reverse osmosis membrane refers to a reverse osmosis membrane having an alkali metal removal rate of 95% or more.
　また、蒸留法や膜蒸留法といった熱エネルギーを分離の駆動力とする濃縮ユニットを用いる場合は、図４に例示するように、原水から濃縮ユニット１６に入る前のいずれかのポイントで濃縮ユニット１６の供給水を、例えば、加熱ユニット１７で予め加温しておき、濃縮によって発生する低濃度水を冷却水で回収するという方法をとることも好ましい実施態様である。とくに、膜蒸留法の一つである直接接触式は、膜を介して高温水から冷却水に水分のみが透過し、高温水が濃縮される方法であるため、本発明の適用に非常に好ましい。加熱ユニット１７の設置位置については、原水からナノ濾過膜ユニット６を出たあとまでであれば、とくに位置に制約はないが、濃縮ユニット１６への供給までの間に前処理等が存在する場合に、それらの前で昇温させると、前処理が濾過や化学反応を伴うものであれば、その性能に影響が出る可能性がある。また、ナノ濾過膜ユニットへの供給前で温度が高い場合は、ナノ濾過膜の透水性能や分離性能が大きく変化する可能性があることや、また、ナノ濾過膜の濃縮水が高温排水になり、エネルギーロスにつながるため、設計上の注意が必要である。さらに、ポンプの発熱が大きな場合は、ポンプでの昇温も可能である。 Further, when using a concentration unit such as a distillation method or a membrane distillation method that uses thermal energy as a driving force for separation, as shown in FIG. 4, the concentration unit 16 at any point before entering the concentration unit 16 from raw water. It is also a preferred embodiment to take a method in which the supplied water is preheated by, for example, the heating unit 17 and the low-concentration water generated by concentration is recovered with cooling water. In particular, the direct contact method, which is one of the membrane distillation methods, is a method in which only water permeates from the high-temperature water to the cooling water through the membrane, and the high-temperature water is concentrated, which is very preferable for application of the present invention. . The position of the heating unit 17 is not particularly limited as long as it is after the nanofiltration membrane unit 6 is removed from the raw water, but there is a pretreatment or the like before the supply to the concentration unit 16. In addition, when the temperature is raised in front of them, the performance may be affected if the pretreatment involves filtration or chemical reaction. In addition, if the temperature is high before the supply to the nanofiltration membrane unit, the water permeability and separation performance of the nanofiltration membrane may change significantly, and the concentrated water of the nanofiltration membrane will become high-temperature drainage. Because it leads to energy loss, design attention is required. Furthermore, when the heat generated by the pump is large, the temperature can be raised by the pump.
　本発明では、濃縮ユニットによるアルカリ金属塩の濃縮の後に、精製アルカリ金属塩の回収を行う。 In the present invention, after the alkali metal salt is concentrated by the concentration unit, the purified alkali metal salt is recovered.
　精製アルカリ金属塩の回収は、例えばカリウム塩の場合、溶解度の温度依存性を利用、またはエタノールなどの貧溶媒を添加して塩化カリウムを回収する公知の方法で回収を行うことができる。リチウム塩の場合は、他のアルカリ金属塩に比べて溶解度が小さいことを利用して、例えば炭酸塩を水溶液に添加することで炭酸リチウムとして回収する。これは炭酸ナトリウムや炭酸カリウムは水への溶解度が十分高い（水100mLに対し20g以上）ことに対し、炭酸リチウムの溶解度が25℃で水100mL対して1.33gしか溶けず、さらに高温では溶解度が低下することを利用したものである。 For example, in the case of a potassium salt, the purified alkali metal salt can be recovered by a known method of recovering potassium chloride by utilizing the temperature dependency of solubility or adding a poor solvent such as ethanol. In the case of a lithium salt, it is recovered as lithium carbonate, for example, by adding a carbonate to an aqueous solution, taking advantage of its low solubility compared to other alkali metal salts. This is because sodium carbonate and potassium carbonate have a sufficiently high solubility in water (20 g or more per 100 mL of water), whereas the solubility of lithium carbonate is only 1.33 g per 100 mL of water at 25 ° C, and the solubility is higher at higher temperatures. It uses the decline.
　回収ユニットでアルカリ金属を回収した後の残液は、排水することもできれば、そのアルカリ金属含有量によっては、供給水に還流させることも可能である。また、ナノ濾過膜ユニット濃縮水は、圧力エネルギーを有しているため、エネルギー回収ユニットを適用すれば、省エネルギーになるため好ましい。また、ナノ濾過膜ユニット濃縮水はアルカリ金属の生成阻害物質を多く含有するため排水するのが一般的であるが、回収したいアルカリ金属イオンが他の成分よりも比率は少ないとはいえ原水濃度以上に含有されているため、イオン交換や吸着によって生成阻害物質濃度を低減した後に、供給水として再利用することも可能である。 The residual liquid after the alkali metal is recovered by the recovery unit can be drained or can be refluxed to the supply water depending on the alkali metal content. Moreover, since the nanofiltration membrane unit concentrated water has pressure energy, it is preferable to apply an energy recovery unit because it saves energy. In addition, nanofiltration membrane unit concentrated water is generally drained because it contains a large amount of alkali metal production inhibitor, but the concentration of alkali metal ions to be recovered is less than the other components, but the concentration of raw water exceeds the concentration. Therefore, it can be reused as feed water after the concentration of the production inhibitor is reduced by ion exchange or adsorption.
　また、前処理ユニット４は、特に制約されるものではなく、原水性状によって、濁質成分の除去や殺菌など適宜選択することができる。原水を前処理し、ナノ濾過膜供給水に適した水質に改質することによって、ナノ濾過膜の負担を低減し、ナノ濾過膜を安定的に保持しながら運転することが可能となる。 Further, the pretreatment unit 4 is not particularly limited, and can be appropriately selected such as removal of turbid components and sterilization depending on the raw aqueous state. By pretreating raw water and modifying it to a water quality suitable for the nanofiltration membrane supply water, it is possible to reduce the burden on the nanofiltration membrane and to operate while stably holding the nanofiltration membrane.
　供給水の濁質を除去する必要がある場合は、前処理ユニット４として砂濾過や精密濾過膜、限外濾過膜などの除濁処理を適用することが効果的である。このときバクテリアや藻類などの微生物が多い場合は、殺菌剤を添加することも好ましい。殺菌剤としては塩素を用いることが好ましく、たとえば塩素ガスや次亜塩素酸ナトリウムを遊離塩素として１～５ｍｇ／ｌの範囲内となるように供給水に添加するとよい。なお、前処理ユニット４の後段のナノ濾過膜ユニット６で使用されるナノ濾過膜によっては特定の殺菌剤に化学的な耐久性がない場合があるので、その場合は、なるべく供給水の上流側で添加し、さらに、ナノ濾過膜ユニット６の供給水入口側近傍にて殺菌剤を無効にすることが好ましい。例えば、遊離塩素の場合は、その濃度を測定し、この測定値に基づいて塩素ガスや次亜塩素酸ナトリウムの添加量を制御したり、亜硫酸水素ナトリウムなどの還元剤を添加したりするとよい。 When it is necessary to remove the turbidity of the supplied water, it is effective to apply turbidity treatment such as sand filtration, microfiltration membrane, ultrafiltration membrane as the pretreatment unit 4. At this time, when there are many microorganisms such as bacteria and algae, it is also preferable to add a bactericidal agent. Chlorine is preferably used as the disinfectant, and for example, chlorine gas or sodium hypochlorite may be added to the feed water as free chlorine so as to be in the range of 1 to 5 mg / l. In addition, depending on the nanofiltration membrane used in the nanofiltration membrane unit 6 subsequent to the pretreatment unit 4, there may be a case where the specific bactericidal agent does not have chemical durability. Further, it is preferable to make the disinfectant ineffective near the feed water inlet side of the nanofiltration membrane unit 6. For example, in the case of free chlorine, its concentration is measured, and the addition amount of chlorine gas and sodium hypochlorite is controlled based on this measured value, or a reducing agent such as sodium bisulfite is added.
　また、濁質以外にバクテリアやタンパク質、天然有機成分などを含有する場合は、ポリ塩化アルミニウム、硫酸バンド、塩化鉄（III）などの凝集剤を加えることも効果的である。凝集させた供給水は、その後に斜向板などで沈降させた上で砂濾過を行ったり、複数本の中空糸膜を束ねた精密濾過膜や限外濾過膜による濾過を行ったりすることによって後段のナノ濾過膜ユニット６を通過させるのに適した供給水とすることができる。特に、凝集剤の添加にあたっては、凝集しやすいようにｐＨを調整することが好ましい。 In addition, in the case of containing bacteria, proteins, natural organic components, etc. in addition to turbid substances, it is also effective to add a flocculant such as polyaluminum chloride, sulfate band, iron (III) chloride. The agglomerated supply water is then subjected to sand filtration after settling on an inclined plate or the like, or by filtration through a microfiltration membrane or an ultrafiltration membrane in which a plurality of hollow fiber membranes are bundled. It can be set as the feed water suitable for letting the latter nanofiltration membrane unit 6 pass. In particular, when adding the flocculant, it is preferable to adjust the pH so as to facilitate aggregation.
　ここで、前処理に砂濾過を用いる場合は、自然に流下する方式の重力式濾過を適用することもできれば、加圧タンクの中に砂を充填した加圧式濾過を適用することも可能である。充填する砂も、単一成分の砂を適用することが可能であるが、例えば、アンスラサイト、珪砂、ガーネット、軽石など、を組み合わせて、濾過効率を高めることが可能である。精密濾過膜や限外濾過膜についても、特に制約はなく、平膜、中空糸膜、管状型膜、プリーツ型、その他いかなる形状のものも適宜用いることができる。膜の素材についても、特に限定されるものではなく、ポリアクリロニトリル、ポリフェニレンスルフォン、ポリフェニレンスルフィドスルフォン、ポリフッ化ビニリデン、ポリプロピレン、ポリエチレン、ポリスルホン、ポリビニルアルコール、酢酸セルロースや、セラミック等の無機素材を用いることができる。また、濾過方式にしても供給水を加圧して濾過する加圧濾過方式や透過側を吸引して濾過する吸引濾過方式のいずれも適用可能である。特に、吸引濾過方式の場合は、凝集沈殿槽や生物処理槽に精密濾過膜や限外濾過膜を浸漬して濾過する、いわゆる凝集膜濾過や膜利用活性汚泥法（ＭＢＲ）を適用することも好ましい。 Here, when sand filtration is used for pretreatment, it is possible to apply gravity-type filtration that naturally flows down, or it is possible to apply pressure-type filtration in which a pressure tank is filled with sand. . As the sand to be filled, single-component sand can be applied. For example, anthracite, silica sand, garnet, pumice, and the like can be combined to increase filtration efficiency. The microfiltration membrane and the ultrafiltration membrane are not particularly limited, and a flat membrane, a hollow fiber membrane, a tubular membrane, a pleated shape, or any other shape can be used as appropriate. The material of the membrane is not particularly limited, and it is possible to use an inorganic material such as polyacrylonitrile, polyphenylene sulfone, polyphenylene sulfide sulfone, polyvinylidene fluoride, polypropylene, polyethylene, polysulfone, polyvinyl alcohol, cellulose acetate, or ceramic. it can. Moreover, even if it is a filtration system, any of the pressure filtration system which pressurizes and filters supply water, and the suction filtration system which sucks and filters the permeation | transmission side are applicable. In particular, in the case of a suction filtration method, so-called agglomerated membrane filtration or membrane-based activated sludge method (MBR), in which a microfiltration membrane or an ultrafiltration membrane is immersed in a coagulation sedimentation tank or a biological treatment tank for filtration, may be applied preferable.
　一方、供給水に溶解性の有機物が多く含まれている場合は、塩素ガスや次亜塩素酸ナトリウムの添加によってそれら有機物を分解することができるが、加圧浮上や活性炭濾過を行うことによっても除去が可能である。また、溶解性の無機物が多く含まれている場合は、有機系高分子電解質やヘキサメタ燐酸ソーダなどのキレート剤を添加したり、イオン交換樹脂などを用いて溶解性イオンと交換したりするとよい。また、鉄やマンガンが可溶な状態で存在しているときは、曝気酸化濾過法や接触酸化濾過法などを用いることが好ましい。 On the other hand, when the supply water contains a lot of soluble organic matter, the organic matter can be decomposed by adding chlorine gas or sodium hypochlorite. Removal is possible. In addition, when a large amount of soluble inorganic substance is contained, a chelating agent such as an organic polymer electrolyte or sodium hexametaphosphate may be added, or exchanged with soluble ions using an ion exchange resin or the like. Further, when iron or manganese is present in a soluble state, it is preferable to use an aeration oxidation filtration method or a contact oxidation filtration method.
　また、図２に例示するように濃縮工程で生成する濃縮ユニット排水の少なくとも一部を原水として還流すれば、原水中のアルカリ金属濃度を低減させることによってナノ濾過膜濃縮水中のアルカリ金属濃度を低減させ、アルカリ金属のロスを減じることができる。さらに、アルカリ土類金属はナノ濾過膜ユニットでの阻止率が高いため、濃度が次第に上がり、運転条件によってはスケールとなってナノ濾過膜の表面に析出し、ナノ濾過膜の性能を低下させたり、ナノ濾過膜を損傷させたりすることになるため、スケールを析出しにくくすることができるという利点も併せ持っているため、好ましい。 Further, as illustrated in FIG. 2, if at least a part of the concentration unit waste water generated in the concentration step is refluxed as raw water, the alkali metal concentration in the nanofiltration membrane concentrated water is reduced by reducing the alkali metal concentration in the raw water. And the loss of alkali metal can be reduced. In addition, alkaline earth metals have a high rejection rate in the nanofiltration membrane unit, so the concentration gradually increases, and depending on the operating conditions, it becomes a scale and precipitates on the surface of the nanofiltration membrane, reducing the performance of the nanofiltration membrane. Since the nanofiltration membrane is damaged, it has an advantage that it is difficult to precipitate the scale, which is preferable.
　さらに、図３に例示するように、濃縮工程で生成する濃縮ユニット排水の少なくとも一部を前処理水に還流することもさらに好ましい。濃縮ユニット排水は、既に前処理された水であり、同じ前処理工程を必要としないことがある。この場合、濃縮ユニット排水を前処理水に還流することで、前処理工程の負担を軽減し、省エネやコスト削減を図れる。 Furthermore, as illustrated in FIG. 3, it is further preferable that at least a part of the concentration unit waste water generated in the concentration step is returned to the pretreated water. Concentration unit wastewater is water that has already been pretreated and may not require the same pretreatment process. In this case, by returning the concentrated unit waste water to the pretreatment water, the burden on the pretreatment process can be reduced, and energy saving and cost reduction can be achieved.
本発明を詳細にまた特定の実施態様を参照して説明したが、本発明の精神と範囲を逸脱することなく様々な変更や修正を加えることができることは、当業者にとって明らかである。
本出願は、２０１１年７月４日出願の日本特許出願２０１１－１４８０１４に基づくものであり、その内容はここに参照として取り込まれる。 Although the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2011-148014 filed on Jul. 4, 2011, the contents of which are incorporated herein by reference.
　本発明は、湖水、地下水、産業廃水などからリチウムやカリウムなどのアルカリ金属を回収する装置およびその運転方法に関するものであり、アルカリ金属を含有する原水に希釈水を添加することによって濃縮，分離，回収が困難な多種の溶質が含まれる水からアルカリ金属を効率的に分離回収することができる。 The present invention relates to a device for recovering alkali metals such as lithium and potassium from lake water, groundwater, industrial wastewater and the like, and a method for operating the same, and concentrates, separates by adding dilution water to raw water containing alkali metals, Alkali metals can be efficiently separated and recovered from water containing various solutes that are difficult to recover.
１：原水
２：原水タンク
３：供給ポンプ
４：前処理ユニット
５：昇圧ポンプ
６：ナノ濾過膜ユニット
７：ナノ濾過膜濃縮水
８：昇圧ポンプ
９：濃縮ユニット
１０：濃縮ユニット排水
１１：濃縮ユニット濃縮水
１２：回収ユニット
１３：回収されたアルカリ金属
１４：回収ユニット残液（排水）
１５：濃縮ユニット排水（還流水）
１６：濃縮ユニット（熱法）
１７：加熱ユニット 1: Raw water 2: Raw water tank 3: Supply pump 4: Pretreatment unit 5: Booster pump 6: Nanofiltration membrane unit 7: Nanofiltration membrane concentrated water 8: Booster pump 9: Concentration unit 10: Concentration unit drainage 11: Concentration unit Concentrated water 12: recovery unit 13: recovered alkali metal 14: recovery unit residual liquid (drainage)
15: Concentration unit drainage (reflux water)
16: Concentration unit (thermal method)
17: Heating unit

Claims (7)

  1. 　ナノ濾過膜を用いてアルカリ金属を含有する原水を透過分離してナノ濾過膜透過水とナノ濾過膜濃縮水を得ること、濃縮ユニットを用いて該ナノ濾過膜透過水を透過分離して濃縮ユニット濃縮水を得ること、及び該濃縮ユニット濃縮水に含まれるアルカリ金属の少なくとも一部を回収すること、を含むアルカリ金属分離回収方法。 Permeate the raw water containing alkali metal using a nanofiltration membrane to obtain nanofiltration membrane permeated water and nanofiltration membrane concentrated water, and permeate and separate the nanofiltration membrane permeated water using a concentration unit. Obtaining concentrated water, and recovering at least a part of the alkali metal contained in the concentrated water in the concentrated unit.
  2. 　前記原水を前処理することで前処理水を得て、前記ナノ濾過膜を用いて該前処理水を透過分離することを特徴とする請求項１に記載のアルカリ金属分離回収方法。 2. The alkali metal separation and recovery method according to claim 1, wherein pretreatment water is obtained by pretreatment of the raw water, and the pretreatment water is permeated and separated using the nanofiltration membrane.
  3. 　前記濃縮ユニットから排出された濃縮ユニット排水の少なくとも一部を、原水または前処理水に還流することを特徴とする請求項１または２に記載のアルカリ金属分離回収方法。 3. The alkali metal separation and recovery method according to claim 1, wherein at least a part of the concentration unit waste water discharged from the concentration unit is returned to raw water or pretreated water.
  4. 　前記前処理が除濁処理であって、前記濃縮ユニット排水の少なくとも一部を用いて、除濁処理設備を洗浄することを特徴とする請求項２または３に記載のアルカリ金属分離回収方法。 4. The alkali metal separation and recovery method according to claim 2, wherein the pretreatment is a turbidity treatment, and the turbidity treatment facility is washed using at least a part of the drainage of the concentration unit.
  5. 　前記濃縮ユニットが、逆浸透膜ユニット、蒸留ユニット、膜蒸留ユニットのいずれかで構成されることを特徴とする請求項１～４のいずれかに記載のアルカリ金属分離回収方法。 The method for separating and recovering alkali metal according to any one of claims 1 to 4, wherein the concentration unit comprises any one of a reverse osmosis membrane unit, a distillation unit, and a membrane distillation unit.
  6. 　前記濃縮ユニットが、濃縮ユニットに供給される供給水の温度よりも低温の原水を用いて低濃度水を冷却回収する機構からなることを特徴とする請求項４または５に記載のアルカリ金属分離回収方法。 6. The alkali metal separation and recovery according to claim 4 or 5, wherein the concentration unit comprises a mechanism for cooling and recovering low concentration water using raw water having a temperature lower than that of the feed water supplied to the concentration unit. Method.
  7. 　ナノ濾過膜を用いてアルカリ金属を含有する原水を透過分離してナノ濾過膜透過水とナノ濾過膜濃縮水を得るナノ濾過膜ユニットと、該ナノ濾過膜透過水を透過分離して濃縮ユニット濃縮水を得る濃縮ユニットと、該濃縮ユニット濃縮水に含まれるアルカリ金属の少なくとも一部を回収する回収ユニットとを備えたアルカリ金属分離回収装置。 Nanofiltration membrane unit to obtain nanofiltration membrane permeated water and nanofiltration membrane concentrated water by permeation separation of raw water containing alkali metal using nanofiltration membrane, and concentration unit concentration by permeating and separating nanofiltration membrane permeated water An alkali metal separation and recovery device comprising a concentration unit for obtaining water and a recovery unit for recovering at least a part of the alkali metal contained in the concentrated water.
PCT/JP2012/066798 2011-07-04 2012-06-29 Method for separating and recovering alkali metal, and apparatus for separating and recovering alkali metal WO2013005694A1 (en)

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