CN114956023B - Phosphoric acid purification method - Google Patents
Phosphoric acid purification method Download PDFInfo
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- CN114956023B CN114956023B CN202110196883.8A CN202110196883A CN114956023B CN 114956023 B CN114956023 B CN 114956023B CN 202110196883 A CN202110196883 A CN 202110196883A CN 114956023 B CN114956023 B CN 114956023B
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- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 title claims abstract description 294
- 229910000147 aluminium phosphate Inorganic materials 0.000 title claims abstract description 146
- 238000000034 method Methods 0.000 title claims abstract description 84
- 238000000746 purification Methods 0.000 title claims abstract description 28
- 239000012528 membrane Substances 0.000 claims abstract description 118
- 239000002253 acid Substances 0.000 claims abstract description 111
- 238000005341 cation exchange Methods 0.000 claims abstract description 58
- 238000005406 washing Methods 0.000 claims abstract description 50
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 32
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 32
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 31
- 239000012535 impurity Substances 0.000 claims abstract description 23
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 46
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 18
- 150000007522 mineralic acids Chemical class 0.000 claims description 16
- 239000002131 composite material Substances 0.000 claims description 12
- 150000007524 organic acids Chemical class 0.000 claims description 11
- 238000005342 ion exchange Methods 0.000 claims description 10
- 239000003014 ion exchange membrane Substances 0.000 claims description 10
- 238000003756 stirring Methods 0.000 claims description 10
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 9
- UQSQSQZYBQSBJZ-UHFFFAOYSA-N fluorosulfonic acid Chemical compound OS(F)(=O)=O UQSQSQZYBQSBJZ-UHFFFAOYSA-N 0.000 claims description 7
- ABDBNWQRPYOPDF-UHFFFAOYSA-N carbonofluoridic acid Chemical compound OC(F)=O ABDBNWQRPYOPDF-UHFFFAOYSA-N 0.000 claims description 6
- 239000002346 layers by function Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 6
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 5
- 239000000463 material Substances 0.000 claims description 5
- 239000011707 mineral Substances 0.000 claims description 5
- LVEGZFXIIKKYTA-UHFFFAOYSA-N 2-iminopropanedioic acid Chemical compound OC(=O)C(=N)C(O)=O LVEGZFXIIKKYTA-UHFFFAOYSA-N 0.000 claims description 3
- 239000002033 PVDF binder Substances 0.000 claims description 3
- 239000004693 Polybenzimidazole Substances 0.000 claims description 3
- 239000004695 Polyether sulfone Substances 0.000 claims description 3
- 239000004734 Polyphenylene sulfide Substances 0.000 claims description 3
- SRSXLGNVWSONIS-UHFFFAOYSA-N benzenesulfonic acid Chemical compound OS(=O)(=O)C1=CC=CC=C1 SRSXLGNVWSONIS-UHFFFAOYSA-N 0.000 claims description 3
- 229940092714 benzenesulfonic acid Drugs 0.000 claims description 3
- 150000002576 ketones Chemical class 0.000 claims description 3
- 239000010410 layer Substances 0.000 claims description 3
- JZMJDSHXVKJFKW-UHFFFAOYSA-M methyl sulfate(1-) Chemical compound COS([O-])(=O)=O JZMJDSHXVKJFKW-UHFFFAOYSA-M 0.000 claims description 3
- 235000006408 oxalic acid Nutrition 0.000 claims description 3
- 229920006260 polyaryletherketone Polymers 0.000 claims description 3
- 229920002480 polybenzimidazole Polymers 0.000 claims description 3
- 229920000570 polyether Polymers 0.000 claims description 3
- 229920006393 polyether sulfone Polymers 0.000 claims description 3
- 229920002530 polyetherether ketone Polymers 0.000 claims description 3
- 229920000069 polyphenylene sulfide Polymers 0.000 claims description 3
- 239000011148 porous material Substances 0.000 claims description 3
- 150000003457 sulfones Chemical class 0.000 claims description 3
- 238000011010 flushing procedure Methods 0.000 claims 3
- ZUOUZKKEUPVFJK-UHFFFAOYSA-N diphenyl Chemical compound C1=CC=CC=C1C1=CC=CC=C1 ZUOUZKKEUPVFJK-UHFFFAOYSA-N 0.000 claims 2
- 238000013019 agitation Methods 0.000 claims 1
- 239000004305 biphenyl Substances 0.000 claims 1
- 235000010290 biphenyl Nutrition 0.000 claims 1
- 230000008569 process Effects 0.000 abstract description 30
- 239000002184 metal Substances 0.000 abstract description 16
- 229910052751 metal Inorganic materials 0.000 abstract description 16
- 150000001768 cations Chemical class 0.000 abstract description 14
- 239000002367 phosphate rock Substances 0.000 abstract description 11
- OJMIONKXNSYLSR-UHFFFAOYSA-N phosphorous acid Chemical compound OP(O)O OJMIONKXNSYLSR-UHFFFAOYSA-N 0.000 abstract description 8
- 239000000126 substance Substances 0.000 abstract description 8
- 239000002699 waste material Substances 0.000 abstract description 5
- 238000005374 membrane filtration Methods 0.000 abstract description 3
- 239000002893 slag Substances 0.000 abstract description 3
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- 235000011007 phosphoric acid Nutrition 0.000 description 117
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 14
- 229920000642 polymer Polymers 0.000 description 12
- 229910021645 metal ion Inorganic materials 0.000 description 10
- 239000002244 precipitate Substances 0.000 description 10
- 229920000557 Nafion® Polymers 0.000 description 8
- 229910019142 PO4 Inorganic materials 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- 150000002500 ions Chemical class 0.000 description 7
- 235000021317 phosphate Nutrition 0.000 description 7
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 6
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 6
- 239000010452 phosphate Substances 0.000 description 6
- 239000011574 phosphorus Substances 0.000 description 6
- 229910052698 phosphorus Inorganic materials 0.000 description 6
- 238000000502 dialysis Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- -1 fluoride ions Chemical class 0.000 description 5
- 125000003118 aryl group Chemical group 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
- 229920001577 copolymer Polymers 0.000 description 4
- 238000010992 reflux Methods 0.000 description 4
- 239000013049 sediment Substances 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- 239000011575 calcium Substances 0.000 description 3
- 238000009388 chemical precipitation Methods 0.000 description 3
- 238000000605 extraction Methods 0.000 description 3
- 238000001728 nano-filtration Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 150000003460 sulfonic acids Chemical class 0.000 description 3
- HRPVXLWXLXDGHG-UHFFFAOYSA-N Acrylamide Chemical compound NC(=O)C=C HRPVXLWXLXDGHG-UHFFFAOYSA-N 0.000 description 2
- 239000004254 Ammonium phosphate Substances 0.000 description 2
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 2
- 239000005977 Ethylene Substances 0.000 description 2
- 229910000148 ammonium phosphate Inorganic materials 0.000 description 2
- 235000019289 ammonium phosphates Nutrition 0.000 description 2
- 125000002843 carboxylic acid group Chemical group 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 description 2
- 238000000909 electrodialysis Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000003337 fertilizer Substances 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N phenol group Chemical group C1(=CC=CC=C1)O ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 2
- 150000003016 phosphoric acids Chemical class 0.000 description 2
- 229920000098 polyolefin Polymers 0.000 description 2
- 229920001955 polyphenylene ether Polymers 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 238000010183 spectrum analysis Methods 0.000 description 2
- 125000000542 sulfonic acid group Chemical group 0.000 description 2
- FZIPCQLKPTZZIM-UHFFFAOYSA-N 2-oxidanylpropane-1,2,3-tricarboxylic acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O.OC(=O)CC(O)(C(O)=O)CC(O)=O FZIPCQLKPTZZIM-UHFFFAOYSA-N 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-M Bisulfite Chemical compound OS([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-M 0.000 description 1
- 238000000184 acid digestion Methods 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 230000005518 electrochemistry Effects 0.000 description 1
- 230000009881 electrostatic interaction Effects 0.000 description 1
- 239000010440 gypsum Substances 0.000 description 1
- 229910052602 gypsum Inorganic materials 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- NIFHFRBCEUSGEE-UHFFFAOYSA-N oxalic acid Chemical compound OC(=O)C(O)=O.OC(=O)C(O)=O NIFHFRBCEUSGEE-UHFFFAOYSA-N 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- STCOOQWBFONSKY-UHFFFAOYSA-N tributyl phosphate Chemical compound CCCCOP(=O)(OCCCC)OCCCC STCOOQWBFONSKY-UHFFFAOYSA-N 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/18—Phosphoric acid
- C01B25/234—Purification; Stabilisation; Concentration
- C01B25/237—Selective elimination of impurities
- C01B25/238—Cationic impurities, e.g. arsenic compounds
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/18—Phosphoric acid
- C01B25/234—Purification; Stabilisation; Concentration
- C01B25/237—Selective elimination of impurities
- C01B25/2372—Anionic impurities, e.g. silica or boron compounds
- C01B25/2375—Fluoride or fluosilicate anion
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention relates to a phosphoric acid purifying method, and belongs to the technical field of chemical industry. The phosphoric acid purification method of the invention comprises the following steps: two chambers are partitioned by a cation exchange membrane, one side is filled with wet phosphoric acid solution, and the other side is filled with washing acid solution to remove impurities in the wet phosphoric acid solution. The method of the invention does not introduce other chemical substances into the wet-process phosphoric acid; the process can be operated continuously; the operation condition is normal pressure, the operation temperature can be normal temperature, and the industrial wet-process phosphoric acid can be directly treated; when the washing acid is selected from strong acid such as hydrochloric acid, nitric acid and the like, water-insoluble slag acid cannot be generated; the waste acid generated by washing can be directly coupled with other processes to separate and recycle metal cations in the waste acid, thereby being beneficial to realizing the comprehensive utilization of phosphorite associated resources; the spent acid from the washing may also be recovered from the acid by other membrane filtration processes and returned to the process.
Description
Technical Field
The invention relates to a phosphoric acid purifying method, and belongs to the technical field of chemical industry.
Background
Phosphorite is a non-renewable resource, and industrial, food and electronic grade phosphoric acid, ammonium phosphate fertilizer, fine phosphate and other products produced by taking the phosphorite as raw materials have important values for grain safety and national economy. At present, the phosphorite reserves in China account for 5% of the total world, and the second place is the second place, but the phosphorite reserves are far smaller than the global proportion of 71% of Morocco. The global yield of phosphate rock in 2018 (in standard ore) was about 2.6 hundred million tons, with a chinese phosphate rock yield of 50% greater than the 29% total of morocco, us and russia with yield ranks two to four. In view of the unoptimal phosphorus resource advantages of China and the current yield ratio of phosphorus ore, the importance of reasonably utilizing the phosphorus ore resources is remarkable.
The wet process of phosphate rock (main component Ca 5F(PO4)3, wherein F can be replaced by Cl and OH) through sulfuric acid digestion to produce phosphoric acid is an important process commonly adopted in the international and domestic phosphorus chemical industry at present. Because the phosphorite in China is often accompanied with impurities, namely the grade of the phosphorite is lower, phosphoric acid (wet phosphoric acid) produced by the wet process contains more impurities. Wet phosphoric acid is used as a raw material for producing large amount of fertilizer such as ammonium phosphate and the like, or for producing food-grade, electronic-grade phosphoric acid or fine phosphate with high added value and the like, and the raw material is required to be purified and decontaminated.
The purification of wet phosphoric acid requires the separation of phosphoric acid from the metal cations of different valence (Fe 3+,Al3+,Mg2+, etc.), fluoride ions (F -) contained therein. Currently, the purification of wet phosphoric acid in industry mainly adopts an extraction or chemical precipitation method. The extraction method uses organic extractant such as tributyl phosphate and the like to extract high-purity phosphoric acid from wet-process phosphoric acid. The chemical precipitation method adopts chemical precipitants such as ammonia gas and the like to precipitate metal cations in the wet-process phosphoric acid in the form of phosphoric acid (complex) salts. The extraction method uses a large amount of organic reagents, slag acid with poor water solubility can be generated, and the process flow is longer; chemical precipitation introduces chemical reagents into phosphoric acid, and the precipitated phosphate also causes waste of phosphorus resources and has a long process.
At present, the purification method of wet-process phosphoric acid which is not industrially applied but has a small report in the scientific paper comprises the following steps: nanofiltration technology for separating phosphoric acid and phosphate is a pressure-driven membrane filtration technology .H.Diallo,M.Rabiller-Baudry,K.Khaless,B.Chaufer,On the electrostatic interactions in the transfer mechanisms of iron during nanofiltration in high concentrated phosphoric acid,Journal of Membrane Science,427(2013)37-47. which, based on the molecular size of the substance and the charged charges, discloses the cooperation of Morocco and French scientists and reports the separation of metal cation phosphates in high-concentration phosphoric acid by means of acid-resistant nanofiltration membranes.
The electrolytic-electrodialysis coupling process separates phosphoric acid and phosphate, positive ions and negative ions in the solution are driven to migrate in opposite directions by using an external direct-current voltage, and hydrogen ions and metal positive ions in the phosphoric acid solution are separated by combining the characteristic that the ion exchange membrane selectively permeates the positive ions or the negative ions, so that the phosphoric acid is purified to a certain extent. The method is reported for the first time in 1996 that (D.Touaibia,H.Kerdjoudj,A.T.Cherif,Concentration and purification of wet industrial phosphoric acid by electro-electrodialysis,Journal of Applied Electrochemistry,26(1996)1071-1073.), has been studied in a small amount in recent years, but has not been industrially applied after decades of development.
Disclosure of Invention
The invention aims to provide a novel phosphoric acid purifying method.
In order to solve the technical problem of the invention, the method for purifying phosphoric acid comprises the following steps:
dividing two chambers by a cation exchange membrane, introducing wet phosphoric acid solution into one side, and introducing washing acid solution into the other side to remove impurities in the wet phosphoric acid solution; preferably, the above steps are repeated more than 3 times.
If the above steps are repeated for more than 3 times, as shown in fig. 4, 3 sets of the daonan dialyzers can be combined, and the impurity removal rate is further improved.
In one embodiment, the wet process phosphoric acid solution and the wash acid solution produce relative motion, preferably by stirring or rinsing; the linear velocity of movement of the stirred or rinsed solution relative to the membrane surface is preferably 1.5mm/s or more, more preferably 2mm/s or more;
The stirring or rinsing time is preferably 300 minutes or more, more preferably 500 minutes or more.
There are many ways to generate the relative motion, such as stirring, rinsing, etc. The separation of the two chambers by the cation exchange membrane is also called a southward dialyzer, and the operation modes are divided into the following modes according to the different flow modes of phosphoric acid and washing acid: 1. both phosphoric acid and washing acid were run through the southward dialyzer only once, i.e., single-pass (single-pass) operation; 2. the phosphoric acid side is a single pass and the scrubber acid circulates between the dialyzer and the external scrubber acid reservoir; 3. the phosphoric acid circulates between the dialyzer and the external phosphoric acid reservoir, the washing acid side being a single pass; 4. the phosphoric acid side and the washing acid side are each circulated.
The linear rate of relative movement of phosphoric acid and the wash acid is the linear rate of movement of the wet phosphoric acid solution relative to the membrane surface + the linear rate of movement of the wash acid solution relative to the membrane surface in the opposite direction.
The rate of the rinse rate has an effect on the rate of impurity ion transfer across the membrane when the rinse rate is low, increasing with increasing rinse rate. But after the rinse rate (fluid line flow rate) is greater than about 2mm/s, the rinse rate has no significant effect on the metal ion transfer rate across the membrane.
It should be noted that when sulfuric acid is used as the washing acid, it is recommended that the line flow rate of the washing acid be selected to be a large value, at least greater than 1.5mm/s, in order to prevent calcium sulfate deposition on the washing acid solution side.
In one embodiment, the wash acid solution is a mineral acid solution; the inorganic acid is preferably a strong inorganic acid or a mixture of a strong inorganic acid and phosphoric acid.
In a specific embodiment, the inorganic strong acid is at least one of nitric acid, hydrochloric acid and sulfuric acid; preferably, the inorganic strong acid is at least two of nitric acid, hydrochloric acid and sulfuric acid; more preferably, the strong inorganic acid is at least one of nitric acid and hydrochloric acid.
In one embodiment, an organic weak acid is also added to the wash acid solution; the organic weak acid is preferably at least one of acetic acid, oxalic acid and iminomalonic acid; the addition amount of the organic weak acid is preferably 0.5 to 30%, preferably 0.5 to 30% of the molar amount of the washing acid. The addition of organic weak acid, even a very small amount of organic weak acid, to the inorganic strong acid can obtain similar and even further improved removal efficiency of metal ions in wet-process phosphoric acid.
In one embodiment, the concentration of the sulfuric acid is 5 to 98wt%, preferably 20 to 60wt%; preferably, the concentration of the nitric acid is 3 to 68wt%, more preferably 10 to 25wt%; preferably, the concentration of the hydrochloric acid is 3 to 37wt%, more preferably 10 to 20wt%.
In one embodiment, the wash acid solution is an organic acid or a mixture of an organic acid and an inorganic acid as described above; the organic acid is preferably at least one of monomethyl sulfate, benzenesulfonic acid and acetic acid.
In one embodiment, the cation exchange membrane comprises a cation exchange membrane with a fixed group that is at least one of a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, and a phenol group;
Preferably, the polymer main chain of the membrane material of the cation exchange membrane is perfluor polyolefin, homo-polymer and copolymer thereof, aromatic polymer, partially fluorinated or perfluorinated aromatic polymer, acrylic ester homo-polymer or acrylamide homo-polymer or copolymer.
In one embodiment, the membrane structure of the cation exchange membrane is a symmetric membrane or an asymmetric membrane; the symmetrical membrane structure is preferably a homogeneous ion exchange membrane, a heterogeneous ion exchange membrane or a semi-homogeneous ion exchange membrane; the asymmetric membrane structure is preferably a composite membrane with a surface ion exchange functional layer and a porous supporting layer, a composite membrane with more than two ion exchange functional layers, or a composite membrane with ion exchange materials filled in membrane holes or pore channels of the porous supporting membrane.
In a specific embodiment, the cation exchange membrane is a perfluorosulfonic acid cation exchange membrane, a perfluorocarboxylic acid cation exchange membrane, a perfluorosulfonic acid and perfluorocarboxylic acid composite membrane, a sulfonated polyether (ether) ketone cation exchange membrane, a sulfonated (phthalene) polyaryletherketone cation exchange membrane, a sulfonated poly (ether) sulfone cation exchange membrane, a sulfonated polyether sulfone ketone cation exchange membrane, a sulfonated polyphenylene ether cation exchange membrane, a sulfonated polyphenylene sulfide cation exchange membrane, a sulfonated polyvinylidene fluoride cation exchange membrane, a sulfonated polybenzimidazole cation exchange membrane, or a sulfonated polystyrene-graft-poly (vinylidene fluoride) ethylene cation exchange membrane.
Advantageous effects
1. No other chemical substances are introduced into the wet-process phosphoric acid;
2. The process can be operated continuously;
3. The operation condition is normal pressure, the operation temperature can be normal temperature, and wet-process phosphoric acid (50-60 ℃) can also be directly treated;
4. when the washing acid is selected from strong acid such as hydrochloric acid, nitric acid and the like, water-insoluble slag acid cannot be generated;
5. the waste acid generated by washing can be directly coupled with other processes (such as ion exchange) to separate and recycle metal cations in the waste acid, thereby being beneficial to realizing the comprehensive utilization of phosphorite associated resources;
6. the spent acid from the washing may also be recovered from the acid by other membrane filtration processes and returned to the process.
Drawings
FIG. 1 is a continuous two-stage parallel flow mode;
FIG. 2 is a continuous two-stage countercurrent mode;
FIG. 3 is a discontinuous two-stage parallel flow mode;
FIG. 4 hybrid three stage reverse flow mode;
WPA-wet phosphoric acid solution; CEM-cation exchange membrane; strip-wash acid solution; purified acid-purified phosphoric acid solution; eluate-eluate.
FIG. 5 impurity removal rate of wet process phosphoric acid solution of example 1;
FIG. 6 impurity removal rate of wet process phosphoric acid solution of example 2;
FIG. 7 impurity removal rate of wet process phosphoric acid solution of example 3;
FIG. 8 impurity removal rate of wet process phosphoric acid solution of example 4;
FIG. 9 impurity removal rate of wet process phosphoric acid solution of example 5;
FIG. 10 impurity removal rate of wet process phosphoric acid solution of example 6;
FIG. 11 impurity removal rate of wet process phosphoric acid solution of example 7;
FIG. 12 impurity removal rate of wet process phosphoric acid solution of comparative example 1;
FIG. 13 is a scanning electron micrograph of the precipitate of comparative example 1;
(a) A precipitate on the surface of the phosphoric acid side membrane, (b) a precipitate on the surface of the sulfuric acid side membrane;
FIG. 14 shows the results of an energy spectrum analysis of the precipitate generated on the surface of the wet-process phosphoric acid side Nafion 112 membrane of comparative example 1;
FIG. 15 mass fraction ratio of precipitate elements on the surface of wet-process phosphoric acid side Nafion 112 membrane of comparative example 1;
FIG. 16 shows the results of an energy spectrum analysis of the precipitate generated on the surface of the sulfuric acid side Nafion 112 membrane of comparative example 1;
Fig. 17 mass fraction ratio of precipitate elements on the sulfuric acid side Nafion 112 membrane surface of comparative example 1.
Detailed Description
In order to solve the technical problem of the invention, the method for purifying phosphoric acid comprises the following steps:
dividing two chambers by a cation exchange membrane, introducing wet phosphoric acid solution into one side, and introducing washing acid solution into the other side to remove impurities in the wet phosphoric acid solution; preferably, the above steps are repeated more than 3 times.
If the above steps are repeated for more than 3 times, as shown in fig. 4, 3 sets of the daonan dialyzers can be combined, and the impurity removal rate is further improved.
The invention can be produced by single-stage or multi-stage south-channel dialyzer combination, and the multi-stage south-channel dialyzer combination can be connected in series or in parallel when being produced.
For example, in one embodiment, a continuous two-stage co-current mode as shown in FIG. 1 may be employed:
Continuous means that the flow of the wash acid solution strip is continuous, two stages means that there are two stages of the southward dialysis process n=2, and parallel flow means that the flow direction of the wash acid solution and the wet phosphoric acid is the same. Optionally between the two stages, the second stage wash acid inlet is supplemented with a further wash acid solution, strip II, which may be the same as Strip I or different. Wet phosphoric acid may optionally be refluxed at each stage.
In one embodiment, a continuous two-stage countercurrent mode as shown in FIG. 2 may be employed: countercurrent refers to the opposite flow direction of the wash acid solution and wet phosphoric acid.
In one embodiment, a discontinuous two-stage co-current mode as shown in FIG. 3 may be employed: discontinuous means that the washing acid solution Strip I of the previous stage is not introduced by the dialysis in the south of the way of each stage, while the new washing acid solution Strip II is used, so that the flow of the washing acid solution is discontinuous in the whole process. The washing acid solution Strip II may be the same as Strip I or may be different.
In one embodiment, a hybrid three stage countercurrent mode as shown in FIG. 4 may be employed:
by mixed it is meant that the flow of the wash acid solution between the different tannan dialyzers includes both continuous and discontinuous cases, as in the figure the wash acid solution between the second and third stages is continuous and the wash acid solution between the second and first stages is discontinuous. The washing acid solution Strip II may be the same as Strip I or may be different.
Wherein the reflux ratio is alpha 1、α2、α3 and is between 0 and 1.
In one embodiment, the wet process phosphoric acid solution and the wash acid solution produce relative motion, preferably by stirring or rinsing; the linear velocity of movement of the stirred or rinsed solution relative to the membrane surface is preferably 1.5mm/s or more, more preferably 2mm/s or more;
The stirring or rinsing time is preferably 300 minutes or more, more preferably 500 minutes or more.
There are many ways to generate the relative motion, such as stirring, rinsing, etc. The separation of the two chambers by the cation exchange membrane is also called a southward dialyzer, and the operation modes are divided into the following modes according to the different flow modes of phosphoric acid and washing acid: 1. both phosphoric acid and washing acid were run through the southward dialyzer only once, i.e., single-pass (single-pass) operation; 2. the phosphoric acid side is a single pass and the scrubber acid circulates between the dialyzer and the external scrubber acid reservoir; 3. the phosphoric acid circulates between the dialyzer and the external phosphoric acid reservoir, the washing acid side being a single pass; 4. the phosphoric acid side and the washing acid side are each circulated.
The linear rate of relative movement of phosphoric acid and the wash acid is the linear rate of movement of the wet phosphoric acid solution relative to the membrane surface + the linear rate of movement of the wash acid solution relative to the membrane surface.
The rate of the rinse rate has an effect on the rate of impurity ion transfer across the membrane when the rinse rate is low, increasing with increasing rinse rate. But after the rinse rate (fluid line flow rate) is greater than about 2mm/s, the rinse rate has no significant effect on the metal ion transfer rate across the membrane.
It should be noted that when sulfuric acid is used as the washing acid, it is recommended that the line flow rate of the washing acid be selected to be a large value, at least greater than 1.5mm/s, in order to prevent calcium sulfate deposition on the washing acid solution side.
In one embodiment, the wash acid solution is a mineral acid solution; the inorganic acid is preferably a strong inorganic acid or a mixture of a strong inorganic acid and phosphoric acid.
In a specific embodiment, the inorganic strong acid is at least one of nitric acid, hydrochloric acid and sulfuric acid; preferably, the inorganic strong acid is at least two of nitric acid, hydrochloric acid and sulfuric acid; more preferably, the strong inorganic acid is at least one of nitric acid and hydrochloric acid.
In one embodiment, an organic weak acid is also added to the wash acid solution; the organic weak acid is preferably at least one of acetic acid, oxalic acid and iminomalonic acid; the addition amount of the organic weak acid is preferably 0.5 to 30%, preferably 0.5 to 30% of the molar amount of the washing acid. The addition of organic weak acid, even a very small amount of organic weak acid, to the inorganic strong acid can obtain similar and even further improved removal efficiency of metal ions in wet-process phosphoric acid.
In one embodiment, the concentration of the sulfuric acid is 5 to 98wt%, preferably 20 to 60wt%; preferably, the concentration of the nitric acid is 3 to 68wt%, more preferably 10 to 25wt%; preferably, the concentration of the hydrochloric acid is 3 to 37wt%, more preferably 10 to 20wt%.
In one embodiment, the wash acid solution is an organic acid or a mixture of an organic acid and an inorganic acid as described above; the organic acid is preferably at least one of monomethyl sulfate, benzenesulfonic acid and acetic acid.
In one embodiment, the cation exchange membrane comprises a cation exchange membrane with a fixed group that is at least one of a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, and a phenol group;
Preferably, the polymer main chain of the membrane material of the cation exchange membrane is perfluor polyolefin, homo-polymer and copolymer thereof, aromatic polymer, partially fluorinated or perfluorinated aromatic polymer, acrylic ester homo-polymer or acrylamide homo-polymer or copolymer.
In one embodiment, the membrane structure of the cation exchange membrane is a symmetric membrane or an asymmetric membrane; the symmetrical membrane structure is preferably a homogeneous ion exchange membrane, a heterogeneous ion exchange membrane or a semi-homogeneous ion exchange membrane; the asymmetric membrane structure is preferably a composite membrane with a surface ion exchange functional layer and a porous supporting layer, a composite membrane with more than two ion exchange functional layers, or a composite membrane with ion exchange materials filled in membrane holes or pore channels of the porous supporting membrane.
In a specific embodiment, the cation exchange membrane is a perfluorosulfonic acid cation exchange membrane, a perfluorocarboxylic acid cation exchange membrane, a perfluorosulfonic acid and perfluorocarboxylic acid composite membrane, a sulfonated polyether (ether) ketone cation exchange membrane, a sulfonated (phthalene) polyaryletherketone cation exchange membrane, a sulfonated poly (ether) sulfone cation exchange membrane, a sulfonated polyether sulfone ketone cation exchange membrane, a sulfonated polyphenylene ether cation exchange membrane, a sulfonated polyphenylene sulfide cation exchange membrane, a sulfonated polyvinylidene fluoride cation exchange membrane, a sulfonated polybenzimidazole cation exchange membrane, or a sulfonated polystyrene-graft-poly (vinylidene fluoride) ethylene cation exchange membrane.
The following describes the invention in more detail with reference to examples, which are not intended to limit the invention thereto.
Example 1
Nitric acid with the concentration of 3mol L -1 is used as a washing acid solution, a perfluorosulfonic acid cation exchange membrane Nafion211 of DuPont company separates two solutions, single-stage Daonan dialysis is adopted, and the removal rate of three main metal cation impurities (Fe 2+/Fe3+,Al3+,Mg2+) in certain industrial-grade wet phosphoric acid with time is examined at 25 ℃. The initial concentration of Fe 2+/Fe3+ in the technical grade wet phosphoric acid used was 7.75Mg/ml, the initial concentration of Al 3+ was 8.22Mg/ml, and the initial concentration of Mg 2+ was 6.43Mg/ml. 88.2ml of technical grade wet-process phosphoric acid and 84.0ml of nitric acid are taken. Both the phosphoric acid side and nitric acid side solutions are circulated between the tannan dialysis device and an external reservoir. The linear velocity of the flow of the nitric acid side solution was 2mm/s, and the linear velocity of the flow of the phosphoric acid side solution was about 1.5mm/s. As shown in FIG. 5, the removal rates of Mg 2+,Al3+ and Fe 2+/Fe3+ in the wet phosphoric acid after 190min purification can reach 31%,11% and 6% respectively.
Example 2
Otherwise, as in example 1, two technical grade wet process phosphoric acids from a north (north) and a south (south) phosphorus chemical industry, respectively, were used. The dosage of the industrial grade wet-process phosphoric acid (north) of a certain enterprise in the north is 92.0ml, and the dosage of the nitric acid is 68.0ml; the amount of industrial grade wet process phosphoric acid (south) used was 95.0ml and the amount of nitric acid was 68.0ml for a business in the south. The Mg 2+、Al3+、Fe2+/Fe3+ content of north and south technical grade wet method phosphoric acid is shown in Table 1. The removal rates of the main three metal cation impurities (Fe 2+/Fe3+,Al3+,Mg2+) with time are shown in figure 6. As can be seen from FIG. 6, after 21 hours of purification, the removal rates of Mg 2+,Al3+ and Fe 2+/Fe3+ in the two wet-process phosphoric acids can reach about 45%,25% and 15% respectively.
TABLE 1 Metal ion content of wet phosphoric acid
Example 3
With the discontinuous parallel flow mode shown in fig. 3, n=3, i.e. the discontinuous three-stage parallel flow mode. The washing acid is 3mol/l nitric acid, the cation exchange membrane is Nafion 211 perfluorinated sulfonic acid membrane of DuPont company, and the wet phosphoric acid is industrial grade wet phosphoric acid (metal ion concentration is shown in example 2) of a certain enterprise in the south. The initial volume of wet phosphoric acid was 98ml and the initial total volumes of the first, second and third stage nitric acids were 90, 88, 90ml, respectively. And (3) removing metal cations for 5 hours in the total reflux state of the first-stage wet-process phosphoric acid, then entering the second-stage and circulating for 5 hours in the total reflux state of the wet-process phosphoric acid, and finally circulating for 10 hours in the total reflux state of the third-stage wet-process phosphoric acid. The linear flow rate of the wet phosphoric acid flow was about 1.5mm/s and the linear flow rate of the nitric acid flow was about 2.0mm/s. The removal rate of metal cations in the wet process phosphoric acid at each stage is shown in fig. 7. As can be seen from FIG. 7, after three stages of purification for 20 hours, the removal rates of Mg 2+,Al3+ and Fe 2+/Fe3+ in the wet phosphoric acid can reach about 80%,35% and 20% respectively.
Example 4
Sulfonated poly (2, 6-dimethyl-1, 4-phenyl ether) cation exchange membrane (SPPO, shandong Tianwei Yang Mo) is used as a medium, and 3mol/L nitric acid is used as washing acid to purify wet phosphoric acid of a certain south enterprise. The initial volume of wet phosphoric acid was 90ml and the initial volume of wash acid was 90ml. The linear velocity of the flow of the phosphoric acid side solution was about 1.5mm/s, and the linear velocity of the flow of the nitric acid side solution was 2mm/s. Both wet phosphoric acid and nitric acid were circulated between the tannan dialyzer and the external reservoir at an experimental temperature of 25 ℃.
TABLE 2 example 4 Metal ion content of technical grade wet process phosphoric acid
The removal rate of the metal cations is shown in figure 8. As can be seen from FIG. 8, after 9 hours of purification, the removal rates of Mg 2+,Al3+ and Fe 2+/Fe3+ in the wet phosphoric acid can reach 10%,1% and 0.2% respectively.
Example 5
Taking a perfluorinated sulfonic acid cation exchange membrane Nafion 211 as a medium, and respectively adopting (a) 5mol/L nitric acid and 0.5mol/L citric acid (CITRIC ACID); (b) 5mol/L nitric acid is used as washing acid to purify wet-process phosphoric acid (the content of main metal ion impurities is shown in example 4). The initial volume of wet phosphoric acid was 90ml and the initial volume of wash acid was 90ml. The linear velocity of the flow of the phosphoric acid side solution was about 1.5mm/s, and the linear velocity of the flow of the washing acid side solution was 2mm/s. Both wet phosphoric acid and washing acid are circulated between the tannan dialyzer and an external reservoir. The experimental temperature was 25 ℃.
The removal rate of the metal cations is shown in figure 9. As can be seen from FIG. 9, after 9h of purification, the removal rates of Mg 2+,Al3+ and Fe 2+/Fe3+ in the wet phosphoric acid can reach 36%,15% and 8% respectively.
Example 6
The method adopts a perfluor sulfonic acid cation exchange membrane Nafion 211 as a medium, and uses 5mol/L nitric acid and 0.5mol/L oxalic acid (oxalic acid) as washing acid to purify wet phosphoric acid of a certain southern enterprise. The initial volume of wet phosphoric acid was 90ml and the initial volume of wash acid was 90ml. The linear velocity of the flow of the phosphoric acid side solution was about 1.5mm/s, and the linear velocity of the flow of the washing acid side solution was 2mm/s. Both wet phosphoric acid and washing acid are circulated between the tannan dialyzer and an external reservoir. The experimental temperature was 25 ℃. The removal rate of the metal cations is shown in figure 10. As can be seen from FIG. 10, after 9h of purification, the removal rates of Mg 2+,Al3+ and Fe 2+/Fe3+ in the wet phosphoric acid can reach 45%,17% and 10% respectively.
Overall, the wet process phosphoric acid can be effectively purified by using a mixed acid of nitric acid and an organic acid as a washing liquid.
Example 7
The metal cations in wet-process phosphoric acid (the content of main metal ion impurities is shown in example 4) of a certain south enterprise are purified by using a perfluorinated sulfonic acid cation exchange membrane Nafion 211 as a medium and 5.3mol/L sulfuric acid (40 wt.% sulfuric acid) as washing acid. The initial volume of wet phosphoric acid was 90ml and the initial volume of wash acid was 90ml. The linear velocity of the flow of the solution on the phosphoric acid side was about 1.5mm/s, and the linear velocity of the flow of the solution on the sulfuric acid side was 2mm/s. Both wet phosphoric acid and sulfuric acid are circulated between the tannan dialyzer and an external reservoir. The experimental temperature was 25 ℃. The removal rate of the metal cations is shown in figure 11. As can be seen from FIG. 11, after 9h of purification, the removal rates of Mg 2+,Al3+ and Fe 2+/Fe3+ in the wet phosphoric acid can reach 50%,25% and 15% respectively.
Comparative example 1
The only difference from example 7 is that the flow rate of sulfuric acid is 0.5mm/s and the removal rate of metal cations is shown in FIG. 12. As can be seen from FIG. 12, after 9h of purification, the removal rates of Mg 2+,Al3+ and Fe 2+/Fe3+ in the wet phosphoric acid can reach 15%,5% and 3% respectively. Obvious sediment is observed on the two side surfaces of the membrane, and a scanning electron micrograph of the sediment is shown in detail in fig. 13, wherein (a) sediment on the surface of the phosphoric acid side membrane and (b) sediment on the surface of the sulfuric acid side membrane are shown in fig. 13. The results of the spectroscopic analysis of the precipitate are shown in detail in FIGS. 14-17. The precipitates on the surface of the film were analyzed by a scanning electron microscope's energy spectrometer and found to be mainly CaSO 4, gypsum. This is because the wet phosphoric acid contains a small amount of Ca 2+. The initial Ca 2+ content in the wet acid was analyzed to be at least 1.01g/L. The presence of the precipitate results in a significant decrease in the rate of metal ion transfer across the membrane and the efficiency of the phosphate purification by the southward dialysis becomes low.
Claims (18)
1. A method of phosphoric acid purification, the method comprising:
Dividing two chambers by a cation exchange membrane, introducing wet phosphoric acid solution into one side, and introducing washing acid solution into the other side to remove impurities in the wet phosphoric acid solution; the wet phosphoric acid solution and the washing acid solution generate relative motion, and the method for generating the relative motion is stirring or flushing; the linear velocity of the solution which is obtained by stirring or flushing relative to the surface of the membrane is more than 1.5 mm/s;
the washing acid solution is an inorganic acid solution; the inorganic acid is at least one of nitric acid, hydrochloric acid and sulfuric acid;
The concentration of sulfuric acid is 5-98 wt%; the concentration of the nitric acid is 3-68wt%; the concentration of the hydrochloric acid is 3-37 wt%;
The cation exchange membrane is a perfluorosulfonic acid cation exchange membrane, a perfluorocarboxylic acid cation exchange membrane, a perfluorosulfonic acid and perfluorocarboxylic acid composite membrane, a sulfonated polyether (ether) ketone cation exchange membrane, a sulfonated (phthalene biphenyl) polyaryletherketone cation exchange membrane, a sulfonated poly (ether) sulfone cation exchange membrane, a sulfonated polyether sulfone ketone cation exchange membrane, a sulfonated polyphenylene sulfide cation exchange membrane, a sulfonated polyvinylidene fluoride cation exchange membrane, a sulfonated polybenzimidazole cation exchange membrane or a sulfonated polystyrene-graft-poly (vinylidene fluoride) cation exchange membrane.
2. The method for purifying phosphoric acid according to claim 1, wherein the steps of separating two chambers by the cation exchange membrane, introducing the wet phosphoric acid solution to one side, and introducing the washing acid solution to the other side, and removing impurities in the wet phosphoric acid solution are repeated more than 3 times.
3. The method of phosphoric acid purification according to claim 1, wherein the agitation or flushing achieves a linear velocity of movement of the solution relative to the membrane surface of 2 mm/s or more.
4. The method for purifying phosphoric acid according to claim 1, wherein the stirring or washing time is 300 minutes or longer.
5. The method for purifying phosphoric acid according to claim 1, wherein the stirring or washing time is 500 minutes or longer.
6. A method of phosphoric acid purification according to claim 1 or 2, wherein the mineral acid is a strong mineral acid or a mixture of a strong mineral acid and phosphoric acid.
7. The method for purifying phosphoric acid according to claim 1, wherein the inorganic acid is at least two of nitric acid, hydrochloric acid, and sulfuric acid.
8. The method for purifying phosphoric acid according to claim 1, wherein the inorganic acid is at least one of nitric acid and hydrochloric acid.
9. The method for phosphoric acid purification according to claim 1, wherein an organic weak acid is further added to the washing acid solution.
10. The method for purifying phosphoric acid according to claim 9, wherein the weak organic acid is at least one of acetic acid, oxalic acid, and iminomalonic acid.
11. A phosphoric acid purification method according to claim 9 or 10, wherein the organic weak acid is added in an amount of 0.5 to 30% of the molar amount of the washing acid.
12. A method of phosphoric acid purification according to claim 1, wherein the concentration of sulfuric acid is 20 to 60wt%.
13. A method of phosphoric acid purification according to claim 1, wherein the concentration of nitric acid is 10 to 25 wt%.
14. A method of phosphoric acid purification according to claim 1, wherein the concentration of the hydrochloric acid is 10 to 20wt%.
15. The method of phosphoric acid purification according to claim 1 or 2, wherein the washing acid solution is an organic acid or a mixture of an organic acid and an inorganic acid; the inorganic acid is at least one of nitric acid, hydrochloric acid and sulfuric acid; the organic acid is at least one of monomethyl sulfate, benzenesulfonic acid and acetic acid.
16. A method of phosphoric acid purification according to claim 1 or 2, wherein the membrane structure of the cation exchange membrane is a symmetric membrane or an asymmetric membrane.
17. The method of phosphoric acid purification according to claim 16, wherein the symmetric membrane is a homogeneous ion exchange membrane, a heterogeneous ion exchange membrane, or a semi-homogeneous ion exchange membrane.
18. The method of phosphoric acid purification according to claim 16, wherein the asymmetric membrane is a composite membrane having a surface ion exchange functional layer and a porous support layer, a composite membrane having two or more ion exchange functional layers, a composite membrane in which an ion exchange material is filled in membrane pores or channels of the porous support membrane.
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