CN117448572A - Method for deeply removing calcium and magnesium - Google Patents
Method for deeply removing calcium and magnesium Download PDFInfo
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- CN117448572A CN117448572A CN202210843163.0A CN202210843163A CN117448572A CN 117448572 A CN117448572 A CN 117448572A CN 202210843163 A CN202210843163 A CN 202210843163A CN 117448572 A CN117448572 A CN 117448572A
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- magnesium
- calcium
- lithium
- sulfate solution
- phosphate
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- 239000011575 calcium Substances 0.000 title claims abstract description 115
- 239000011777 magnesium Substances 0.000 title claims abstract description 108
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 title claims abstract description 101
- 238000000034 method Methods 0.000 title claims abstract description 95
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 title claims abstract description 91
- 229910052791 calcium Inorganic materials 0.000 title claims abstract description 87
- 229910052749 magnesium Inorganic materials 0.000 title claims abstract description 87
- INHCSSUBVCNVSK-UHFFFAOYSA-L lithium sulfate Inorganic materials [Li+].[Li+].[O-]S([O-])(=O)=O INHCSSUBVCNVSK-UHFFFAOYSA-L 0.000 claims abstract description 95
- RBTVSNLYYIMMKS-UHFFFAOYSA-N tert-butyl 3-aminoazetidine-1-carboxylate;hydrochloride Chemical compound Cl.CC(C)(C)OC(=O)N1CC(N)C1 RBTVSNLYYIMMKS-UHFFFAOYSA-N 0.000 claims abstract description 95
- 239000012535 impurity Substances 0.000 claims abstract description 89
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 77
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 74
- 239000007788 liquid Substances 0.000 claims abstract description 51
- 239000002893 slag Substances 0.000 claims abstract description 50
- 238000006243 chemical reaction Methods 0.000 claims abstract description 35
- 238000000926 separation method Methods 0.000 claims abstract description 30
- 239000000047 product Substances 0.000 claims abstract description 28
- 229910019142 PO4 Inorganic materials 0.000 claims abstract description 27
- 239000010452 phosphate Substances 0.000 claims abstract description 27
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims abstract description 27
- KMQAPZBMEMMKSS-UHFFFAOYSA-K calcium;magnesium;phosphate Chemical compound [Mg+2].[Ca+2].[O-]P([O-])([O-])=O KMQAPZBMEMMKSS-UHFFFAOYSA-K 0.000 claims abstract description 19
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims abstract description 15
- ZFXVRMSLJDYJCH-UHFFFAOYSA-N calcium magnesium Chemical compound [Mg].[Ca] ZFXVRMSLJDYJCH-UHFFFAOYSA-N 0.000 claims abstract description 12
- 239000007795 chemical reaction product Substances 0.000 claims abstract description 8
- 239000000243 solution Substances 0.000 claims description 118
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 26
- 238000001556 precipitation Methods 0.000 claims description 26
- 239000010413 mother solution Substances 0.000 claims description 25
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 23
- 229910052708 sodium Inorganic materials 0.000 claims description 23
- 239000011734 sodium Substances 0.000 claims description 23
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 14
- 238000000605 extraction Methods 0.000 claims description 9
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 7
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 claims description 6
- ASTWEMOBIXQPPV-UHFFFAOYSA-K trisodium;phosphate;dodecahydrate Chemical group O.O.O.O.O.O.O.O.O.O.O.O.[Na+].[Na+].[Na+].[O-]P([O-])([O-])=O ASTWEMOBIXQPPV-UHFFFAOYSA-K 0.000 claims description 6
- 229910000027 potassium carbonate Inorganic materials 0.000 claims description 3
- 239000011347 resin Substances 0.000 abstract description 26
- 229920005989 resin Polymers 0.000 abstract description 26
- 239000001506 calcium phosphate Substances 0.000 abstract description 11
- 229910000389 calcium phosphate Inorganic materials 0.000 abstract description 11
- 235000011010 calcium phosphates Nutrition 0.000 abstract description 11
- GVALZJMUIHGIMD-UHFFFAOYSA-H magnesium phosphate Chemical compound [Mg+2].[Mg+2].[Mg+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O GVALZJMUIHGIMD-UHFFFAOYSA-H 0.000 abstract description 11
- 239000004137 magnesium phosphate Substances 0.000 abstract description 11
- 229910000157 magnesium phosphate Inorganic materials 0.000 abstract description 11
- 229960002261 magnesium phosphate Drugs 0.000 abstract description 11
- 235000010994 magnesium phosphates Nutrition 0.000 abstract description 11
- 230000008901 benefit Effects 0.000 abstract description 10
- 238000001179 sorption measurement Methods 0.000 abstract description 10
- QORWJWZARLRLPR-UHFFFAOYSA-H tricalcium bis(phosphate) Chemical compound [Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O QORWJWZARLRLPR-UHFFFAOYSA-H 0.000 abstract description 7
- 230000007613 environmental effect Effects 0.000 abstract description 5
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 36
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 22
- 230000000694 effects Effects 0.000 description 22
- 229910001425 magnesium ion Inorganic materials 0.000 description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 21
- 238000005406 washing Methods 0.000 description 16
- 229910001424 calcium ion Inorganic materials 0.000 description 15
- 238000011084 recovery Methods 0.000 description 15
- 239000000203 mixture Substances 0.000 description 13
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 12
- 229910001448 ferrous ion Inorganic materials 0.000 description 12
- 238000002386 leaching Methods 0.000 description 12
- 239000000706 filtrate Substances 0.000 description 11
- 239000003513 alkali Substances 0.000 description 10
- 238000001914 filtration Methods 0.000 description 8
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 description 8
- 239000012452 mother liquor Substances 0.000 description 8
- 238000001514 detection method Methods 0.000 description 7
- 229910001386 lithium phosphate Inorganic materials 0.000 description 7
- 238000003756 stirring Methods 0.000 description 7
- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 0.000 description 7
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 6
- 229910003002 lithium salt Inorganic materials 0.000 description 6
- 159000000002 lithium salts Chemical class 0.000 description 6
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 5
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 5
- 229910001416 lithium ion Inorganic materials 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 238000006386 neutralization reaction Methods 0.000 description 5
- 238000003828 vacuum filtration Methods 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 4
- 238000001704 evaporation Methods 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 238000009616 inductively coupled plasma Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 229910052938 sodium sulfate Inorganic materials 0.000 description 4
- 235000011152 sodium sulphate Nutrition 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 239000002699 waste material Substances 0.000 description 4
- 238000004065 wastewater treatment Methods 0.000 description 4
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- CNLWCVNCHLKFHK-UHFFFAOYSA-N aluminum;lithium;dioxido(oxo)silane Chemical compound [Li+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O CNLWCVNCHLKFHK-UHFFFAOYSA-N 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 239000013522 chelant Substances 0.000 description 3
- 230000020477 pH reduction Effects 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 229910052642 spodumene Inorganic materials 0.000 description 3
- MYRTYDVEIRVNKP-UHFFFAOYSA-N 1,2-Divinylbenzene Chemical compound C=CC1=CC=CC=C1C=C MYRTYDVEIRVNKP-UHFFFAOYSA-N 0.000 description 2
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 2
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 description 2
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 2
- 150000001342 alkaline earth metals Chemical class 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- PTMHPRAIXMAOOB-UHFFFAOYSA-L phosphoramidate Chemical compound NP([O-])([O-])=O PTMHPRAIXMAOOB-UHFFFAOYSA-L 0.000 description 2
- 238000004537 pulping Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 238000000638 solvent extraction Methods 0.000 description 2
- 238000001149 thermolysis Methods 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 229910018119 Li 3 PO 4 Inorganic materials 0.000 description 1
- 206010027339 Menstruation irregular Diseases 0.000 description 1
- 229910019440 Mg(OH) Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- -1 and simultaneously Chemical compound 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000002241 glass-ceramic Substances 0.000 description 1
- 239000004519 grease Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 230000001050 lubricating effect Effects 0.000 description 1
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 1
- 235000019341 magnesium sulphate Nutrition 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 238000010979 pH adjustment Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000001172 regenerating effect Effects 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 239000010865 sewage Substances 0.000 description 1
- 239000002562 thickening agent Substances 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
Classifications
-
- 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
- C22B3/44—Treatment or purification of solutions, e.g. obtained by leaching by chemical processes
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D15/00—Lithium compounds
- C01D15/06—Sulfates; Sulfites
-
- 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
- C22B26/10—Obtaining alkali metals
- C22B26/12—Obtaining lithium
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Geochemistry & Mineralogy (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
The invention provides a method for deeply removing calcium and magnesium, which comprises the following steps: adjusting the pH value of the lithium sulfate solution to perform primary impurity removal to obtain primary impurity removal products; carrying out first solid-liquid separation on the first-stage impurity removal product to obtain first-stage slag and impurity removal liquid; adjusting the pH value of the impurity removing liquid and reacting with carbonate to perform secondary impurity removal to obtain a secondary impurity removing product; performing second solid-liquid separation on the second-stage impurity removal product to obtain calcium magnesium slag and crude lithium sulfate solution; carrying out deep calcium and magnesium removal on the crude lithium sulfate solution and phosphate reaction to obtain a reaction product; and carrying out third solid-liquid separation on the reaction product to obtain refined lithium sulfate solution and lithium-containing calcium magnesium phosphate mixed slag. The method for deeply removing the calcium and the magnesium through the low solubility product of the calcium phosphate and the magnesium phosphate has the advantages of simple operation of the whole process flow, high reaction efficiency, low equipment investment, simple operation, environmental protection, no pollution and the like compared with a resin adsorption method for removing the calcium and the magnesium.
Description
Technical Field
The invention belongs to the technical field of calcium and magnesium removal, and particularly relates to a method for deeply removing calcium and magnesium, in particular to a method for deeply removing calcium and magnesium in the process of preparing lithium salt by extracting lithium from ores.
Background
Lithium is an important and emerging industrial resource and strategic resource, and is widely applied to the fields of batteries, lubricating grease, glass ceramics, medicines, fuels, catalysts and the like, and particularly in the field of new energy in recent years, lithium is very focused and is known as "21 st century energy metal".
At present, the most widely used and mature ore lithium extraction method is the sulfuric acid method. After the spodumene is subjected to the conversion of a crystal form of early high-temperature roasting and the roasting of sulfuric acid, the acid clinker mainly contains lithium sulfate, the lithium sulfate is dissolved into a liquid phase through the neutralization and water leaching processes, but the impurity content in a leaching solution is higher, most of aluminum and iron are removed through neutralization, but the existence of alkaline earth metals such as calcium, magnesium and the like can be separated out in the subsequent evaporation and crystallization process, so that the heat exchange effect is affected by the scaling of a heat exchanger, and the scaling is cleaned by stopping at an irregular period, so that the running efficiency of equipment is reduced, and the production cost is increased; most importantly, the quality of the subsequent preparation of lithium salt is affected, and the economic benefit is reduced, so that calcium and magnesium in the leaching solution are required to be thoroughly removed.
At present, the most widely applied method for industrially removing calcium and magnesium is resin adsorption to remove the calcium and magnesium, and the selective adsorption of the resin on the calcium and magnesium can be utilized to remove the calcium and magnesium to below 5ppm; however, the resin has high price, the investment of the whole set of equipment is large, the adsorption capacity of the resin to calcium and magnesium is small, the resin has certain loss in the running process, and new resin needs to be replaced at irregular intervals, so that the production cost is further increased; in the operation process, the resin needs to be eluted and regenerated frequently, and the process is complicated; in addition, the process of eluting with hydrochloric acid can cause system sewage, needs to be treated, and the process of eluting with sulfuric acid is easy to cause resin caking due to low solubility of calcium sulfate, so that the adsorption effect of the resin is reduced.
In addition, there is a method of deeply removing calcium and magnesium by adding EDTA in the production, but the addition amount of EDTA must be excessive, and the excessive EDTA can affect the quality of the subsequent products. The method can further remove calcium and magnesium deeply by a solvent extraction method, but the solvent extraction method has long process flow and high production cost, and the organic solvent can enter the solution in a dissolving and entrainment mode to influence the quality of the finished product.
Disclosure of Invention
In view of the above, the invention aims to provide a method for deeply removing calcium and magnesium, which has the advantages of high reaction efficiency, low equipment investment, simple operation, high lithium recovery rate, low running cost, no wastewater treatment, environmental protection, no pollution or high economic benefit.
The invention provides a method for deeply removing calcium and magnesium, which comprises the following steps:
adjusting the pH value of the lithium sulfate solution to perform primary impurity removal to obtain primary impurity removal products;
carrying out first solid-liquid separation on the first-stage impurity removal product to obtain first-stage slag and impurity removal liquid;
adjusting the pH value of the impurity removing liquid and reacting with carbonate to perform secondary impurity removal to obtain a secondary impurity removing product;
performing second solid-liquid separation on the second-stage impurity removal product to obtain calcium magnesium slag and crude lithium sulfate solution;
carrying out deep calcium and magnesium removal on the crude lithium sulfate solution and phosphate reaction to obtain a reaction product;
and carrying out third solid-liquid separation on the reaction product to obtain refined lithium sulfate solution and lithium-containing calcium magnesium phosphate mixed slag.
According to the embodiment of the invention, the lithium sulfate solution is generated in the process of extracting lithium from the ore by a sulfuric acid method; the lithium sulfate solution is obtained by acidification roasting, slurrying leaching, neutralization and filtration in the lithium extraction process of spodumene sulfuric acid method.
The invention provides a method for deeply removing calcium and magnesium in the process of preparing lithium salt by extracting lithium from ore, which utilizes calcium phosphate (solubility product at room temperature: 2.0 multiplied by 10) -29 ) Magnesium phosphate (solubility product at room temperature: 6.31X10 -26 ) The lower solubility product deeply removes calcium and magnesium; compared with the traditional method for removing calcium and magnesium by resin adsorption, the method has the advantages of reverse reactionHigh reaction efficiency, low equipment investment, simple operation, high lithium recovery rate, low running cost, no wastewater treatment, environmental protection, no pollution or high economic benefit, etc.
According to the embodiment of the invention, the pH value of the lithium sulfate solution is adjusted by adopting a sodium thermal precipitation mother solution;
the pH value of the impurity removing liquid is adjusted by adopting a sodium thermal precipitation mother liquid;
the mother solution for heat separation sodium is mother solution obtained by freeze separation sodium and separation during the process of producing lithium hydroxide by liquid-alkali conversion method, and re-dissolving, evaporating, crystallizing and separating sodium sulfate.
According to the invention, the pH value of the lithium sulfate solution and the impurity removing solution is adjusted by adopting the heat-precipitation sodium mother solution to perform primary impurity removing and secondary impurity removing, so that not only is the consumption of alkali saved, but also the problems of treatment of heat-precipitation sodium mother solution impurities and removal of ferrous ions in a lithium sulfate solution leaching system are solved.
According to an embodiment of the present invention, the crude lithium sulfate solution and phosphate react with an excess of phosphate; the amount of phosphate is in accordance with Ca in the crude lithium sulfate solution 2+ 、Mg 2+ With PO (PO) 3 3- The calculated amount of 20-100% of the theoretical amount of the reaction is added.
The invention ensures the removal effect of calcium and magnesium by adding excessive phosphate, so that the content of calcium and magnesium in the refined magnesium sulfate solution obtained by the invention is lower.
According to an embodiment of the invention, the phosphate is selected from sodium phosphate dodecahydrate;
the temperature of the deep calcium and magnesium removal is 50-90 ℃;
the time for deeply removing calcium and magnesium is more than or equal to 30min.
According to the embodiment of the invention, the obtained lithium-containing calcium-magnesium phosphate mixed slag further comprises:
and returning the lithium-containing calcium magnesium phosphate mixed slag to react with the impurity removing liquid, and circularly using the lithium-containing calcium magnesium phosphate mixed slag for the second-stage impurity removal.
The invention circularly uses the lithium-containing calcium-magnesium phosphate mixed slag to remove calcium and magnesium in the two-stage impurity removal process, and simultaneously releases the lithium-containing calcium-magnesium phosphate mixed slagThe lithium is introduced into the solution to improve the recovery rate of lithium by converting lithium phosphate into calcium phosphate and magnesium phosphate precipitate with a solubility product of at least 10 orders of magnitude lower, and by using lithium phosphate (solubility product at room temperature: 2.37X10) -4 ) The solubility product difference between the calcium phosphate and the magnesium phosphate perfectly releases lithium ions in the lithium phosphate back into the solution, so that the recovery rate of lithium is ensured.
According to the embodiment of the invention, the pH value of the lithium sulfate solution is adjusted to 9-10;
the temperature of the first section of impurity removal is 50-90 ℃;
the time for removing the impurities in the first section is more than or equal to 30min.
According to the embodiment of the invention, the pH value of the impurity removing liquid is adjusted to 12-13;
the carbonate is at least one selected from sodium carbonate and potassium carbonate;
the dosage of the carbonate is according to Ca in the impurity removing liquid 2+ 、Mg 2+ With CO 3 2- The calculated amount of 5-10% of the theoretical amount of the reaction mass excess is added.
According to the embodiment of the invention, the temperature of the two-stage impurity removal is 50-90 ℃;
the time of the second-stage impurity removal is more than or equal to 30min.
According to an embodiment of the present invention, ca in the purified lithium sulfate solution 2+ And Mg (magnesium) 2+ The total content of (2) is less than 5ppm.
The method for deeply removing calcium and magnesium provided by the invention is used for removing Ca in lithium sulfate solution 2+ And Mg (magnesium) 2+ Has better removal effect.
Drawings
Fig. 1 is a process flow diagram of a method for deeply removing calcium and magnesium in a process of preparing lithium salt from ore Dan Dili in an embodiment of the invention.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides a method for deeply removing calcium and magnesium, which comprises the following steps:
adjusting the pH value of the lithium sulfate solution to perform primary impurity removal to obtain primary impurity removal products;
carrying out first solid-liquid separation on the first-stage impurity removal product to obtain first-stage slag and impurity removal liquid;
adjusting the pH value of the impurity removing liquid and reacting with carbonate to perform secondary impurity removal to obtain a secondary impurity removing product;
performing second solid-liquid separation on the second-stage impurity removal product to obtain calcium magnesium slag and crude lithium sulfate solution;
carrying out deep calcium and magnesium removal on the crude lithium sulfate solution and phosphate reaction to obtain a reaction product;
and carrying out third solid-liquid separation on the reaction product to obtain refined lithium sulfate solution and lithium-containing calcium magnesium phosphate mixed slag.
In some embodiments of the invention, the lithium sulfate solution is produced during a sulfuric acid process ore lithium extraction process. The invention has no special limitation on the sulfuric acid method ore lithium extraction process, and the sulfuric acid method ore lithium extraction process well known to the skilled in the art is adopted, namely, the sulfuric acid method lithium extraction process is carried out by acidizing roasting, slurrying leaching, neutralizing and filtering to obtain a lithium sulfate solution; the lithium sulfate solution contains alkaline earth metal impurities such as calcium and magnesium.
In some embodiments of the invention, the lithium sulfate solution comprises:
12-18 g/L Li + ；
200-1000 ppm Ca 2+ ；
200-1000 ppm of Mg 2+ ；
Fe of 1-20 ppm 2+ ；
1 to 30ppm of Al 3+ ；
83-125 g/L SO 4 2- 。
In some embodiments of the invention, the Li + The content of (C) can be 13g/L, 14g/L, 15g/L, 16g/L,17g/L；Ca 2+ May be 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm; mg of 2+ May be 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm; fe (Fe) 2+ May be 2ppm, 4ppm, 6ppm, 8ppm, 10ppm, 12ppm, 14ppm, 16ppm, 18ppm; al (Al) 3+ May be 2ppm, 4ppm, 6ppm, 8ppm, 10ppm, 12ppm, 14ppm, 16ppm, 18ppm, 20ppm, 22ppm, 24ppm, 26ppm, 28ppm; SO (SO) 4 2- The content of (C) may be 85g/L, 90g/L, 95g/L, 100g/L, 105g/L, 110g/L, 115g/L, 120g/L.
The method for deeply removing calcium and magnesium is particularly suitable for removing impurities from lithium sulfate waste liquid generated by extracting lithium from sulfuric acid method ores, and the lithium sulfate waste liquid contains a large amount of Ca 2+ And Mg (magnesium) 2+ The invention uses phosphate to remove the calcium and magnesium ions in the solution, and returns the obtained phosphate slag to remove the calcium and magnesium again, so that the Li in the lithium sulfate solution can be recovered + The recovery rate of lithium is improved; the method provided by the invention can be used for well treating and utilizing the lithium sulfate waste liquid.
In some embodiments of the invention, the lithium sulfate solution may be a sodium thermal precipitation mother liquor for pH adjustment; the mother solution for heat separation sodium is mother solution obtained by freeze separation sodium and separation during the process of producing lithium hydroxide by liquid-alkali conversion method, and re-dissolving, evaporating, crystallizing and separating sodium sulfate. In some embodiments of the invention, the thermolysis sodium mother liquor may be a mixed solution of saturated sodium sulfate and lithium sulfate, lithium hydroxide. In some embodiments of the invention, OH in the thermolysis sodium mother liquor - The content of (C) may be 25-70 g/L, such as 30g/L, 35g/L, 40g/L, 45g/L, 50g/L, 55g/L, 60g/L, 65g/L.
In some embodiments of the invention, the pH of the lithium sulfate solution may be adjusted to 9 to 10, such as 9.2, 9.4, 9.5, 9.6, 9.8. Therefore, the pH value range can lead ferrous ions in the lithium sulfate solution to be completely precipitated and partial magnesium ions to be precipitated, thereby effectively reducing the impurity content in the lithium sulfate solution and being beneficial to the follow-up impurity removal. It will be appreciated that in some embodiments of the invention, the major components in the length of slag are magnesium ions and ferrous ions.
In some embodiments of the invention, the temperature of the one stage of removal may be 50-90 ℃, such as 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃; the time for removing impurities in the first stage can be more than or equal to 30min, such as 35min, 40min, 45min, 50min, 55min and 60min. Therefore, in the temperature and time range, a section of impurity removing effect is better, all ferrous ions and part of magnesium ions in the lithium sulfate solution can be effectively removed, the temperature range is favorable for filtering, the filtering effect and efficiency are improved, and if the reaction time is too short, the reaction is possibly incomplete, so that the impurity removing effect is reduced.
In some embodiments of the present invention, a section of impurity removal uses an alkaline material, such as a sodium thermal precipitation mother liquor, to precipitate calcium ions and magnesium ions in a lithium sulfate solution, so that a large amount of calcium ions and magnesium ions in the lithium sulfate solution are precipitated first, which is beneficial to further adopting phosphate to deeply remove the lithium sulfate, and the reaction mainly occurs:
Ca 2+ +2OH - ＝Ca(OH) 2 ↓
Mg 2+ +2OH -- ＝Mg(OH) 2 ↓。
the pH of the lithium sulfate solution is regulated by adopting the lithium hydroxide heat-precipitation sodium mother solution to perform one-stage impurity removal, so that not only is the consumption of alkali saved, but also the problems of impurities in the lithium hydroxide heat-precipitation sodium mother solution and ferrous ions in a leaching system are solved.
The method of the first solid-liquid separation is not particularly limited, and any solid-liquid separation apparatus known to those skilled in the art may be used, such as one or more of a filter press, a decanter centrifuge, a sedimentation thickener, a floating ball clarifier, a bag filter, and a separation column.
In some embodiments of the present invention, the second stage of impurity removal may first adjust the pH of the impurity removal solution with an alkaline substance and then react it with carbonate, so that the carbonate precipitates calcium ions and magnesium ions better, and the method provided by the present invention has better calcium and magnesium removal effect.
In some embodiments of the present invention, the pH of the impurity removing solution may be a sodium-precipitation mother solution, where the sodium-precipitation mother solution is identical to the sodium-precipitation mother solution in the above technical solution, and will not be described herein. The adoption of the heat-precipitation sodium mother solution can not only save the consumption of alkali, but also solve the problems of impurities in the heat-precipitation sodium mother solution of lithium hydroxide and ferrous ions in a leaching system.
In some embodiments of the present invention, the pH of the impurity removing liquid may be adjusted to 12-13, such as 12.2, 12.4, 12.6, 12.8. Therefore, the above pH range is more suitable for calcium and magnesium ion precipitation, and the calcium and magnesium removal effect is better, if the pH value is less than 12, the calcium and magnesium removal effect is relatively poor, and if the pH value is too high, the alkali amount is increased, and the production cost is increased.
In some embodiments of the present invention, the carbonate may be selected from at least one of sodium carbonate and potassium carbonate.
In some embodiments of the invention, the carbonate may be used in an amount corresponding to Ca in the decontaminating liquid 2+ 、Mg 2+ With CO 3 2- The calculated amount of 5-10% of the theoretical amount of the reaction is added, such as 6%, 7%, 8% and 9% of the calculated amount of the theoretical amount of the reaction. In some embodiments of the invention, ca in the impurity removing liquid 2+ 、Mg 2+ The content of (c) may be detected by ICP-OES (inductively coupled plasma emission spectrometer), atomic absorption spectrometer detection analysis or ICP-MS (inductively coupled plasma mass spectrometry). In some specific embodiments, ICP-MS (inductively coupled plasma mass spectrometry) detection can be adopted, and the detection accuracy is high. Therefore, on the premise of ensuring better calcium and magnesium removal effect, the carbonate consumption is reasonable, and the raw material waste and the cost increase are not caused.
In some embodiments of the invention, the temperature of the two-stage impurity removal may be 50-90 ℃, such as 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃; the two-stage impurity removal time can be more than or equal to 30min, such as 35min, 40min, 45min, 50min, 55min and 60min. The solubility of the calcium carbonate is reduced along with the temperature rise, and the two-stage impurity removal is carried out in the temperature range, so that the removal effect of the calcium and the temperature rise cost can be simultaneously considered; in the temperature time range, the full reaction of calcium and magnesium ions can be ensured, and the cost rise caused by overlong time can be avoided; under the conditions, most of calcium and magnesium ions in the lithium sulfate solution can be effectively removed, and better calcium and magnesium removal effect can be realized compared with other temperature and time ranges.
In some embodiments of the present invention, in the second stage of impurity removal, an alkaline substance is first used to adjust the pH value of the impurity removal solution, and then carbonate is used to react with calcium ions and magnesium ions in the impurity removal solution to generate a precipitate, so as to further remove calcium ions and magnesium ions in the lithium sulfate solution, where the reaction is:
Ca 2+ +CO 3 2- ＝CaCO 3 ↓
Mg 2+ +CO 3 2- ＝Mg CO 3 ↓。
in some embodiments of the invention, the second solid-liquid separation method may be vacuum filtration in a buchner funnel.
In some embodiments of the present invention, the second solid-liquid separation may further include:
and washing the obtained filter residues to obtain calcium magnesium residues. Therefore, lithium carried in filter residues can be reduced, and the washing liquid containing a small amount of lithium obtained by washing can return spodumene obtained by pulping, acidifying and roasting at the front end of a sulfuric acid method ore lithium extraction process, so that the utilization rate of lithium is improved.
In some embodiments of the invention, the method of washing may be washing with hot water, and the temperature of the washing may be 50-90 ℃, such as 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃; the number of washes may be 2 to 4, such as 3. Therefore, the effect of reducing lithium carried in filter residues is better, the washing times are proper, and the water treatment cost is reasonable.
In some embodiments of the invention, the phosphate may be selected from sodium phosphate dodecahydrate. Therefore, the effect of removing calcium and magnesium is better, the raw materials are easy to obtain, and the cost is lower.
In some embodiments of the invention, the crude lithium sulfate solution and phosphate may be in excess of phosphate during the reaction; the amount of phosphate may be in accordance with Ca in the crude lithium sulfate solution 2+ 、Mg 2+ With PO (PO) 3 3- The calculated amount of 20-100% of the theoretical amount of the reaction is added, such as 30%, 40%, 50%, 60%, 70%, 80% and 90% of the calculated amount of the theoretical amount of the reaction. Therefore, the method can ensure the basically complete precipitation of calcium and magnesium ions, improve the effect of removing calcium and magnesium, and achieve the effect that the total content of calcium and magnesium ions in the refined lithium sulfate solution is less than 5ppm.
In some embodiments of the invention, ca in the crude lithium sulfate solution 2+ 、Mg 2+ The content can be detected by ICP-OES (inductively coupled plasma emission spectrometer), atomic absorption spectrometer detection analysis or ICP-MS (inductively coupled plasma mass spectrometry).
In the invention, the deep calcium and magnesium removal is carried out by utilizing the low solubility product of calcium phosphate and magnesium phosphate, and the removal effect of the calcium and the magnesium is ensured by adding excessive phosphate, and the related main reaction equation is as follows:
3Ca 2+ +2PO 4 3- ＝Ca 3 (PO 4 ) 2 ↓
3Mg 2+ +2PO 4 3- ＝Mg 3 (PO 4 ) 2 ↓
3Li + +PO 4 3- ＝Li 3 PO 4 ↓。
in some embodiments of the invention, the crude lithium sulfate solution and phosphate may be reacted at a temperature of 50 to 90 ℃, such as 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃; the reaction time can be more than or equal to 30min, such as 60min, 70min, 80min, and 90min. Therefore, conditions more suitable for calcium and magnesium ion precipitation can be provided, the calcium and magnesium ions in the lithium sulfate solution are promoted to be precipitated, and the effect that the total content of the calcium and magnesium ions in the refined lithium sulfate solution is less than 5ppm is achieved.
In some embodiments of the invention, the third solid-liquid separation method may be vacuum filtration in a buchner funnel.
In some embodiments of the invention, the method for obtaining the lithium-containing calcium-magnesium phosphate mixed slag can further comprise the following steps:
and returning the lithium-containing calcium magnesium phosphate mixed slag to react with the impurity removing liquid, and circularly using the lithium-containing calcium magnesium phosphate mixed slag for secondary impurity removal.
In some embodiments of the invention, the lithium-containing calcium-magnesium phosphate mixed slag can be slurried with water and then reacted with the impurity removal liquid. Therefore, the lithium release in the lithium-containing calcium-magnesium phosphate mixed slag can be further promoted, and the recovery rate of lithium is improved.
In the invention, the mixed slag containing lithium and calcium and magnesium is recycled in the two-stage impurity removal process to remove calcium and magnesium, and simultaneously, lithium in the mixed slag containing lithium and calcium and magnesium is released into solution, so that the recovery rate of lithium is improved, the principle is that lithium phosphate is converted into calcium phosphate and magnesium phosphate precipitation with the solubility product at least 10 orders of magnitude lower at room temperature, and the related main reaction equation is as follows:
3Ca 2+ +2Li 3 PO 4 ＝Ca 3 (PO 4 ) 2 ↓+6Li +
3Mg 2+ +2Li 3 PO 4 - ＝Mg 3 (PO 4 ) 2 ↓+6Li + 。
in some embodiments of the invention, ca in the refined lithium sulfate solution 2+ And Mg (magnesium) 2+ May be less than 5ppm; ca in the refined lithium sulfate solution 2+ 、Mg 2+ The content can be detected by ICP-OES (inductively coupled plasma emission spectrometer), atomic absorption spectrometer detection analysis or ICP-MS (inductively coupled plasma mass spectrometry).
The embodiment of the invention provides a method for deeply removing calcium and magnesium in the process of preparing lithium salt by extracting lithium from ores, a process flow chart of the method is shown in figure 1, and the method comprises the following steps of: (a) The method comprises the steps of (1) carrying out primary impurity removal and secondary impurity removal on a lithium sulfate solution subjected to transformation roasting, acidification roasting, slurrying leaching and neutralization in the traditional sulfuric acid method ore lithium extraction process by respectively reacting alkali with carbonate in a step-by-step pH value adjusting manner; (b) Obtaining primary slag, secondary calcium magnesium slag and crude lithium sulfate solution through solid-liquid separation and washing; (c) Adding excessive phosphate into the crude lithium sulfate solution to deeply remove calcium and magnesium; (d) Solid-liquid separation is carried out to obtain refined lithium sulfate solution with deep calcium and magnesium removal and lithium-containing calcium and magnesium phosphate mixed slag; (e) And (3) pulping the lithium-containing calcium-magnesium phosphate mixed slag and returning to the step (a) to circularly use the calcium-magnesium in the second-stage impurity removal, and simultaneously releasing lithium in the lithium-containing calcium-magnesium phosphate mixed slag into a solution, thereby improving the recovery rate of the lithium.
According to the method for deeply removing calcium and magnesium in the process of preparing lithium salt by extracting lithium from the ore, disclosed by the invention, the calcium and magnesium are deeply removed through the lower solubility product of calcium phosphate and magnesium phosphate, the removal effect of the calcium and magnesium is ensured by adding excessive phosphate, and although part of lithium forms lithium phosphate precipitation due to excessive phosphate, the lithium in the lithium-containing calcium and magnesium phosphate mixed slag is pulpified and returned to the previous working procedure for removing the calcium and magnesium, and the lithium in the lithium-containing calcium and magnesium phosphate mixed slag is released and returned to the solution, so that the recovery rate of the lithium is improved. In addition, the invention adjusts the pH of the lithium sulfate solution to perform one-stage impurity removal by adopting the lithium hydroxide heat-precipitation sodium mother solution, thereby not only saving the consumption of alkali, but also solving the problems of impurities in the lithium hydroxide heat-precipitation sodium mother solution and ferrous ions in a leaching system. Compared with the traditional method for removing calcium and magnesium by resin adsorption, the method provided by the invention has the advantages of high reaction efficiency, low equipment investment, simple operation, high lithium recovery rate, low running cost, no wastewater treatment or environmental protection, no pollution and the like.
The lithium sulfate solution in the following embodiment of the invention is the lithium sulfate solution which is subjected to transformation roasting, acidification roasting, slurrying leaching and neutralization in the process of extracting lithium from ores; the mother liquor obtained by the process of producing lithium hydroxide by using a liquid alkali conversion method is obtained by freezing and separating sodium sulfate, and the mother liquor obtained by re-dissolving, evaporating, crystallizing and separating sodium sulfate is mainly composed of a mixed solution of saturated sodium sulfate and lithium sulfate, and lithium hydroxide, wherein OH - The concentration of (C) is 35-65 g/L.
Example 1
Heating 1L of lithium sulfate solution through a water bath to control the temperature of the solution to 60 ℃, then adding a thermonatrite mother solution to adjust the pH to 9, and carrying out solid-liquid separation after reacting for 30min to obtain primary slag and primary filtrate containing magnesium ions and ferrous ions;
adding a sodium thermal precipitation mother solution into the first-stage filtrate to adjust the pH value to 12, calculating according to the mass excess coefficient of 5% of calcium and magnesium in the solution, adding sodium carbonate, stirring and reacting for 60min, rapidly transferring the mixture into a Buchner funnel while the mixture is hot after the reaction is finished, and vacuum filtering, and washing filter residues with hot water for 3 times to obtain calcium and magnesium residues and a crude lithium sulfate solution;
detecting the content of calcium and magnesium in the crude lithium sulfate solution, calculating according to the content of calcium and magnesium in the solution and the mass excess coefficient of 20%, adding sodium phosphate dodecahydrate, stirring and reacting for 60min, rapidly transferring the solution into a Buchner funnel while the solution is hot after the reaction is finished, vacuum filtering, and washing filter residues with hot water for 3 times to obtain lithium-containing calcium and magnesium slag and refined lithium sulfate solution;
and (3) adding water into the lithium-containing calcium-magnesium slag to slurry, returning to a first-stage filtrate process to continuously remove calcium and magnesium, releasing lithium ions in the slag back to the solution, improving the lithium recovery rate, and analyzing and detecting the calcium and magnesium content in the refined lithium sulfate solution.
Example 2
Heating 1L of lithium sulfate solution through a water bath to control the temperature of the solution to 90 ℃, then adding a thermonatrite mother solution to adjust the pH to 10, and carrying out solid-liquid separation after reacting for 30min to obtain primary slag and primary filtrate containing magnesium ions and ferrous ions;
adding a thermonatrite mother solution into the first-stage filtrate to adjust the pH value to 13, calculating according to the mass excess coefficient of 8% of calcium and magnesium in the solution, adding sodium carbonate, stirring and reacting for 60min, rapidly transferring the mixture into a Buchner funnel while the mixture is hot after the reaction is finished, and performing vacuum filtration, and washing filter residues with hot water for 3 times to obtain calcium and magnesium residues and a crude lithium sulfate solution;
analyzing and detecting the content of calcium and magnesium in the crude lithium sulfate solution, calculating according to the content of calcium and magnesium in the solution and the mass excess coefficient of 50%, adding sodium phosphate dodecahydrate, stirring and reacting for 60min, rapidly transferring the mixture into a Buchner funnel while the mixture is hot after the reaction is finished, carrying out vacuum filtration, and washing filter residues with hot water for 3 times to obtain lithium-containing calcium-magnesium slag and refined lithium sulfate solution;
and (3) adding water into the lithium-containing calcium-magnesium slag to slurry, returning to a first-stage filtrate process to continuously remove calcium and magnesium, releasing lithium ions in the slag back to the solution, improving the lithium recovery rate, and analyzing and detecting the calcium and magnesium content of the refined lithium sulfate solution.
Example 3
Heating 1L of lithium sulfate solution through a water bath to control the temperature of the solution to 90 ℃, then adding a thermonatrite mother solution to adjust the pH to 10, and carrying out solid-liquid separation after reacting for 60min to obtain primary slag and primary filtrate containing magnesium ions and ferrous ions;
adding a thermonatrite mother solution into the first-stage filtrate to adjust the pH value to 13, calculating according to the mass excess coefficient of 10% according to the calcium and magnesium content in the solution, adding sodium carbonate, stirring and reacting for 60min, rapidly transferring the mixture into a Buchner funnel while the mixture is hot after the reaction is finished, and vacuum filtering, and washing filter residues with hot water for 3 times to obtain calcium and magnesium residues and a crude lithium sulfate solution;
analyzing and detecting the content of calcium and magnesium in the crude lithium sulfate solution, calculating according to the content of calcium and magnesium in the solution and the mass excess coefficient of 100%, adding sodium phosphate dodecahydrate, stirring and reacting for 60min, rapidly transferring the mixture into a Buchner funnel while the mixture is hot after the reaction is finished, and performing vacuum filtration, and washing filter residues with hot water for 3 times to obtain lithium-containing calcium-magnesium slag and refined lithium sulfate solution;
and (3) adding water into the lithium-containing calcium-magnesium slag to slurry, returning to a first-stage filtrate process to continuously remove calcium and magnesium, releasing lithium ions in the slag back to the solution, improving the lithium recovery rate, and analyzing and detecting the calcium and magnesium content of the refined lithium sulfate solution.
Comparative example 1
Heating 1L of lithium sulfate solution through a water bath to control the temperature of the solution to 90 ℃, then adding a thermonatrite mother solution to adjust the pH to 10, and carrying out solid-liquid separation after reacting for 60min to obtain primary slag and primary filtrate containing magnesium ions and ferrous ions;
adding a thermonatrite mother solution into the first-stage filtrate to adjust the pH value to 13, calculating according to the mass excess coefficient of 10% according to the calcium and magnesium content in the solution, adding sodium carbonate, stirring and reacting for 60min, rapidly transferring the mixture into a Buchner funnel while the mixture is hot after the reaction is finished, and vacuum filtering, and washing filter residues with hot water for 3 times to obtain calcium and magnesium residues and a crude lithium sulfate solution;
the crude lithium sulfate solution enters resin (LSC-850 phosphoramidate chelate resin provided by New materials of West An and blue and technology, inc., is macroporous chelate resin with weak acidic phosphoramidate active groups crosslinked by styrene and divinylbenzene, and the chemical structure is favorable for forming chelate with metal ions) to adsorb and remove calcium and magnesium, so as to obtain refined lithium sulfate solution;
when the resin is saturated in adsorption, the resin needs to be regenerated, and the specific method is as follows: the lithium sulfate in the resin column was replaced with water, and then with a gradient concentration H 2 SO 4 Regenerating the solution (because the calcium sulfate is slightly soluble, the resin is required to be ensured not to agglomerate in the operation process), eluting calcium and magnesium ions, and then washing the resin with water until the pH value is more than 3; and the resin was transformed each time with 2 times the volume of 5wt% NaOH solution and then simply washed with pure water.
Performance detection
The crude lithium sulfate solution and the purified lithium sulfate solution in the examples and comparative examples of the present invention were subjected to Li using ICP-OES (inductively coupled plasma emission spectrometer) + 、Ca 2+ 、Mg 2+ The content is detected, and the detection result is as follows:
it can be seen that the purified lithium sulfate solutions Ca obtained in examples 1 to 3 of the present invention 2+ 、Mg 2+ The total content is less than 5ppm, the effect of deeply removing calcium and magnesium is basically equivalent to that of resin adsorption, expensive resin treatment equipment and resin materials are not needed, and a complex resin regeneration process is not needed, so that a large amount of wastewater is not generated.
Compared with the traditional method for removing calcium and magnesium by resin adsorption, the method provided by the invention has the advantages of high reaction efficiency, low equipment investment, simple operation, high lithium recovery rate, low running cost, no wastewater treatment, environmental protection, no pollution or high economic benefit and the like; the removal effect of calcium and magnesium is ensured by adding excessive phosphate, and although part of lithium forms lithium phosphate precipitation due to the excessive phosphate, the lithium ions in the lithium phosphate are released to return to the solution by slurrying the lithium-containing calcium and magnesium phosphate mixed slag and returning to the previous procedure to remove the calcium and magnesium, so that the recovery rate of the lithium is ensured and the economic benefit is improved; the lithium hydroxide heat sodium precipitation mother liquor is used for regulating the pH value of the lithium sulfate solution step by step to remove impurities, so that not only is the consumption of alkali saved, but also the problem of open circuit of impurities of the lithium hydroxide heat sodium precipitation mother liquor and ferrous ions (primary slag) in a leaching system is solved.
While the invention has been described and illustrated with reference to specific embodiments thereof, the description and illustration is not intended to limit the invention. It will be apparent to those skilled in the art that various changes may be made in this particular situation, material, composition of matter, substance, method or process without departing from the true spirit and scope of the invention as defined by the following claims, so as to adapt the objective, spirit and scope of the present application. All such modifications are intended to be within the scope of this appended claims. Although the methods disclosed herein have been described with reference to particular operations being performed in a particular order, it should be understood that these operations may be combined, sub-divided, or reordered to form an equivalent method without departing from the teachings of the present disclosure. Thus, unless specifically indicated herein, the order and grouping of operations is not a limitation of the present application.
Claims (10)
1. A method for deep removal of calcium and magnesium comprising:
adjusting the pH value of the lithium sulfate solution to perform primary impurity removal to obtain primary impurity removal products;
carrying out first solid-liquid separation on the first-stage impurity removal product to obtain first-stage slag and impurity removal liquid;
adjusting the pH value of the impurity removing liquid and reacting with carbonate to perform secondary impurity removal to obtain a secondary impurity removing product;
performing second solid-liquid separation on the second-stage impurity removal product to obtain calcium magnesium slag and crude lithium sulfate solution;
carrying out deep calcium and magnesium removal on the crude lithium sulfate solution and phosphate reaction to obtain a reaction product;
and carrying out third solid-liquid separation on the reaction product to obtain refined lithium sulfate solution and lithium-containing calcium magnesium phosphate mixed slag.
2. The method of claim 1, wherein the lithium sulfate solution is produced during a sulfuric acid process ore lithium extraction process.
3. The method of claim 1, wherein at least one of the following conditions is satisfied:
the pH value of the lithium sulfate solution is adjusted by adopting a sodium thermal precipitation mother solution;
the pH value of the impurity removing liquid is adjusted by adopting a sodium thermal precipitation mother liquid;
the crude lithium sulfate solution and phosphate react with excess phosphate.
4. A process according to claim 3, wherein the phosphate is used in an amount corresponding to Ca in the crude lithium sulfate solution 2+ 、Mg 2+ With PO (PO) 3 3- The calculated amount of 20-100% of the theoretical amount of the reaction is added.
5. The method of claim 1, wherein at least one of the following conditions is satisfied:
the phosphate is selected from sodium phosphate dodecahydrate;
the temperature of the deep calcium and magnesium removal is 50-90 ℃;
the time for deeply removing calcium and magnesium is more than or equal to 30min.
6. The method according to claim 1, wherein the obtaining of the lithium-containing calcium-magnesium phosphate mixed slag further comprises:
and returning the lithium-containing calcium magnesium phosphate mixed slag to react with the impurity removing liquid, and circularly using the lithium-containing calcium magnesium phosphate mixed slag for the second-stage impurity removal.
7. The method of claim 1, wherein at least one of the following conditions is satisfied:
the pH value of the lithium sulfate solution is adjusted to 9-10;
the temperature of the first section of impurity removal is 50-90 ℃;
the time for removing the impurities in the first section is more than or equal to 30min.
8. The method of claim 1, wherein at least one of the following conditions is satisfied:
the pH value of the impurity removing liquid is adjusted to be 12-13;
the carbonate is at least one selected from sodium carbonate and potassium carbonate;
the dosage of the carbonate is according to Ca in the impurity removing liquid 2+ 、Mg 2+ With CO 3 2- The calculated amount of 5-10% of the theoretical amount of the reaction mass excess is added.
9. The method of claim 1, wherein at least one of the following conditions is satisfied:
the temperature of the two-stage impurity removal is 50-90 ℃;
the time of the second-stage impurity removal is more than or equal to 30min.
10. The method according to claim 1, wherein Ca in the refined lithium sulfate solution 2+ And Mg (magnesium) 2+ The total content of (2) is less than 5ppm.
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