CN116534898A - Method for preparing chromium oxide powder by taking chromium electroplating wastewater as raw material - Google Patents
Method for preparing chromium oxide powder by taking chromium electroplating wastewater as raw material Download PDFInfo
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- CN116534898A CN116534898A CN202310543284.8A CN202310543284A CN116534898A CN 116534898 A CN116534898 A CN 116534898A CN 202310543284 A CN202310543284 A CN 202310543284A CN 116534898 A CN116534898 A CN 116534898A
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- 239000011651 chromium Substances 0.000 title claims abstract description 110
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 title claims abstract description 49
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 title claims abstract description 48
- 229910052804 chromium Inorganic materials 0.000 title claims abstract description 47
- 238000000034 method Methods 0.000 title claims abstract description 47
- 239000002351 wastewater Substances 0.000 title claims abstract description 33
- 238000009713 electroplating Methods 0.000 title claims abstract description 26
- 229910000423 chromium oxide Inorganic materials 0.000 title claims abstract description 22
- 239000000843 powder Substances 0.000 title claims abstract description 20
- 239000002994 raw material Substances 0.000 title claims abstract description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 34
- 230000020477 pH reduction Effects 0.000 claims abstract description 27
- 238000005406 washing Methods 0.000 claims abstract description 27
- POULHZVOKOAJMA-UHFFFAOYSA-N dodecanoic acid Chemical compound CCCCCCCCCCCC(O)=O POULHZVOKOAJMA-UHFFFAOYSA-N 0.000 claims abstract description 24
- 238000001354 calcination Methods 0.000 claims abstract description 23
- 238000001556 precipitation Methods 0.000 claims abstract description 20
- 239000003513 alkali Substances 0.000 claims abstract description 19
- 230000003647 oxidation Effects 0.000 claims abstract description 17
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 17
- 229910021645 metal ion Inorganic materials 0.000 claims abstract description 16
- 239000005639 Lauric acid Substances 0.000 claims abstract description 12
- 239000000725 suspension Substances 0.000 claims description 33
- 238000006722 reduction reaction Methods 0.000 claims description 32
- VQWFNAGFNGABOH-UHFFFAOYSA-K chromium(iii) hydroxide Chemical compound [OH-].[OH-].[OH-].[Cr+3] VQWFNAGFNGABOH-UHFFFAOYSA-K 0.000 claims description 31
- 239000007788 liquid Substances 0.000 claims description 28
- 238000000926 separation method Methods 0.000 claims description 26
- 238000006243 chemical reaction Methods 0.000 claims description 25
- 238000005868 electrolysis reaction Methods 0.000 claims description 19
- 238000002156 mixing Methods 0.000 claims description 13
- 239000003638 chemical reducing agent Substances 0.000 claims description 11
- 239000012295 chemical reaction liquid Substances 0.000 claims description 10
- PXLIDIMHPNPGMH-UHFFFAOYSA-N sodium chromate Chemical compound [Na+].[Na+].[O-][Cr]([O-])(=O)=O PXLIDIMHPNPGMH-UHFFFAOYSA-N 0.000 claims description 10
- 238000006386 neutralization reaction Methods 0.000 claims description 9
- 239000010802 sludge Substances 0.000 claims description 8
- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulfite Chemical compound [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 claims description 8
- 239000002253 acid Substances 0.000 claims description 7
- DWAQJAXMDSEUJJ-UHFFFAOYSA-M Sodium bisulfite Chemical compound [Na+].OS([O-])=O DWAQJAXMDSEUJJ-UHFFFAOYSA-M 0.000 claims description 4
- HRZFUMHJMZEROT-UHFFFAOYSA-L sodium disulfite Chemical compound [Na+].[Na+].[O-]S(=O)S([O-])(=O)=O HRZFUMHJMZEROT-UHFFFAOYSA-L 0.000 claims description 4
- 235000010267 sodium hydrogen sulphite Nutrition 0.000 claims description 4
- 229940001584 sodium metabisulfite Drugs 0.000 claims description 4
- 235000010262 sodium metabisulphite Nutrition 0.000 claims description 4
- 235000010265 sodium sulphite Nutrition 0.000 claims description 4
- 238000006056 electrooxidation reaction Methods 0.000 claims description 3
- 239000003054 catalyst Substances 0.000 claims 1
- 230000009467 reduction Effects 0.000 abstract description 12
- 239000012535 impurity Substances 0.000 abstract description 11
- 230000008569 process Effects 0.000 abstract description 11
- 239000002244 precipitate Substances 0.000 abstract description 8
- 230000004048 modification Effects 0.000 abstract description 7
- 238000012986 modification Methods 0.000 abstract description 7
- 239000000049 pigment Substances 0.000 abstract description 7
- 230000002776 aggregation Effects 0.000 abstract description 6
- 150000003839 salts Chemical class 0.000 abstract description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 5
- 238000005054 agglomeration Methods 0.000 abstract description 5
- 239000002245 particle Substances 0.000 abstract description 5
- 230000001376 precipitating effect Effects 0.000 abstract description 5
- 239000000084 colloidal system Substances 0.000 abstract description 3
- 239000013078 crystal Substances 0.000 abstract description 3
- 230000002209 hydrophobic effect Effects 0.000 abstract description 3
- 238000011084 recovery Methods 0.000 abstract description 3
- 239000010865 sewage Substances 0.000 abstract description 2
- 239000000243 solution Substances 0.000 description 31
- 239000002002 slurry Substances 0.000 description 9
- 229910001220 stainless steel Inorganic materials 0.000 description 9
- 239000010935 stainless steel Substances 0.000 description 9
- 238000001914 filtration Methods 0.000 description 8
- 239000011734 sodium Substances 0.000 description 7
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 6
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 6
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 5
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 238000003825 pressing Methods 0.000 description 5
- 238000003756 stirring Methods 0.000 description 5
- 229910052719 titanium Inorganic materials 0.000 description 5
- 239000010936 titanium Substances 0.000 description 5
- 239000011701 zinc Substances 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- YADSGOSSYOOKMP-UHFFFAOYSA-N dioxolead Chemical compound O=[Pb]=O YADSGOSSYOOKMP-UHFFFAOYSA-N 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 4
- 238000007747 plating Methods 0.000 description 4
- 238000011085 pressure filtration Methods 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 229910000029 sodium carbonate Inorganic materials 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 239000002585 base Substances 0.000 description 2
- 239000010406 cathode material Substances 0.000 description 2
- 150000001844 chromium Chemical class 0.000 description 2
- -1 chromium oxyhydroxide Chemical compound 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 239000000706 filtrate Substances 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- CJTCBBYSPFAVFL-UHFFFAOYSA-N iridium ruthenium Chemical compound [Ru].[Ir] CJTCBBYSPFAVFL-UHFFFAOYSA-N 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000002161 passivation Methods 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000005979 thermal decomposition reaction Methods 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 238000004065 wastewater treatment Methods 0.000 description 2
- JHWIEAWILPSRMU-UHFFFAOYSA-N 2-methyl-3-pyrimidin-4-ylpropanoic acid Chemical compound OC(=O)C(C)CC1=CC=NC=N1 JHWIEAWILPSRMU-UHFFFAOYSA-N 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 1
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 1
- 235000011130 ammonium sulphate Nutrition 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- DQIPXGFHRRCVHY-UHFFFAOYSA-N chromium zinc Chemical compound [Cr].[Zn] DQIPXGFHRRCVHY-UHFFFAOYSA-N 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 238000005189 flocculation Methods 0.000 description 1
- 230000016615 flocculation Effects 0.000 description 1
- 208000015181 infectious disease Diseases 0.000 description 1
- ULFQGKXWKFZMLH-UHFFFAOYSA-N iridium tantalum Chemical compound [Ta].[Ir] ULFQGKXWKFZMLH-UHFFFAOYSA-N 0.000 description 1
- MOUPNEIJQCETIW-UHFFFAOYSA-N lead chromate Chemical compound [Pb+2].[O-][Cr]([O-])(=O)=O MOUPNEIJQCETIW-UHFFFAOYSA-N 0.000 description 1
- 239000002932 luster Substances 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 239000013049 sediment Substances 0.000 description 1
- 239000004289 sodium hydrogen sulphite Substances 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 239000008399 tap water Substances 0.000 description 1
- 235000020679 tap water Nutrition 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G37/00—Compounds of chromium
- C01G37/02—Oxides or hydrates thereof
- C01G37/033—Chromium trioxide; Chromic acid
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/51—Particles with a specific particle size distribution
- C01P2004/52—Particles with a specific particle size distribution highly monodisperse size distribution
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/60—Optical properties, e.g. expressed in CIELAB-values
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Electroplating And Plating Baths Therefor (AREA)
Abstract
The invention provides a method for preparing chromium oxide powder by taking chromium electroplating wastewater as a raw material, which belongs to the technical field of sewage treatment, and comprises the steps of firstly carrying out first precipitation pretreatment on chromium-containing wastewater to remove impurity metal ions in the wastewater, and using an electrolytic oxidation method to precipitate Cr (OH) in the process of removing impurities 3 Oxidation to CrO 4 2‑ Thereby further improving the recovery rate of chromium; crO in wastewater is treated by 4 2‑ By acidification reduction and then adding alkali to convert into Cr (OH) with high purity 3 Precipitating; cr (OH) with high purity 3 Washing the salt entrained by the precipitate, adding water and lauric acid for modification to enable Cr (OH) 3 The outermost surface of the crystal grain adsorbs a layer of carbon chains to become hydrophobic, and Cr (OH) is modified 3 The colloid is powdery, the agglomeration degree is low, the water content is low, and the Cr is obtained after calcination 2 O 3 The powder is pigment grade, has no agglomeration phenomenon, high purity and uniform particle size, and does not need additional crushing.
Description
Technical Field
The invention relates to the technical field of sewage treatment, in particular to a method for preparing chromium oxide powder by taking chromium electroplating wastewater as a raw material.
Background
Chromium oxide (Cr) 2 O 3 ) As a chemical raw material, the chromium salt has a very important role in the chemical industry of chromium salt. Cr (Cr) 2 O 3 The product is green and crystalline, has high temperature resistance and corrosion resistance, shows better light resistance and chemical stability, has the product quality mainly divided into two classes of industrial grade and pigment grade, and has different technical requirements in different application fields. Technical grade Cr 2 O 3 Mainly used in the fields of metallurgy, refractory materials and the like with lower end, and pigment grade Cr 2 O 3 Also called as chrome oxide green, belongs to high-end products and is widely used in the fields of paint, printing ink and the like.
At present, domestic Cr 2 O 3 Mainly adopts chromic anhydride (CrO) 3 ) The thermal decomposition method is used for production, the preparation process is complex, the operation environment is bad, and the dust containing hexavalent chromium is discharged in the roasting process. The sodium dichromate and ammonium sulfate thermal decomposition method is a main process for producing chromium oxide green abroad, the product produced by the process has complete varieties, no harmful gas is produced in the production process, but the product prepared by the process has high sulfur content, and the byproduct chromium-containing sodium sulfate is difficult to recycle. The method adopts a hydrogen reduction process to eliminate impurity infection and emission of waste gas and waste residue, and simultaneously has the preparation capability of various types of chromium oxide green, but the process has higher requirements on equipment, hydrogen belongs to flammable and explosive gas, and has great industrialization difficulty. The patent CN201811555377.8 discloses a chromium oxide and a preparation method thereof, which reduces hexavalent chromium salt solution added with seed crystal by reducing gas under hydrothermal condition to obtain chromium oxyhydroxide, calcines and filters the chromium oxyhydroxide precipitate obtained by separation,the chromium oxide can be obtained, and the process has higher requirements on equipment and is not easy to process.
The chromium metal has good corrosion resistance, can keep the luster, good wear resistance, good heat resistance, high hardness and other performances for a long time, so the chromium metal has wide application in electroplating, such as hard chromium electroplating, decorative chromium electroplating, zinc chromium plating passivation and the like. In the electroplating process, due to the rinsing of the plating piece, the scrapping of the bath solution, the replacement and cleaning of the filter cloth and filter core of the plating solution filter, and the like, a certain amount of chromium-containing wastewater can be generated, and the main pollution factors in the chromium-containing wastewater are Cr 2 O 7 2- 、Cr 3+ 、Zn 2+ 、Cu 2+ 、Fe 3+ 、Ni 2+ Etc. The conventional chromium water treatment method is a reduction neutralization flocculation method, and Cr is added with a reducing agent under an acidic condition 2 O 7 2- Reduction to Cr 3+ Then adding alkali to adjust the pH value of the wastewater to convert metal ions into corresponding hydroxide precipitates for removal, wherein the chromium mud obtained by the method has complex components, low chromium content and difficult secondary utilization. Patent CN1373094a uses a solution containing lead ions to treat hexavalent chromium-containing wastewater to produce chrome yellow (PbCrO 4 ) Hexavalent chromium is recovered in the form of lead-containing wastewater, but requires further treatment.
As is clear from the above, pigment-grade chromium oxide has high requirements and great preparation difficulty, and the chromium-containing wastewater contains a large amount of chromium resources, which are not effectively utilized.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for preparing chromium oxide powder by using chromium electroplating wastewater as a raw material, wherein the preparation method provided by the present invention uses the chromium electroplating wastewater as a raw material, effectively utilizes waste chromium resources, and the obtained chromium oxide powder has the advantages of excellent color, no agglomeration phenomenon, high purity, uniform granularity, and meets the requirements of pigment-grade chromium oxide.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a method for preparing chromium oxide powder by taking chromium electroplating wastewater as a raw material, which comprises the following steps:
1) Mixing the chromium electroplating wastewater with alkali to perform a first precipitation reaction to obtain a first suspension;
2) Carrying out direct current electrolytic oxidation on the first suspension in the step 1) and then carrying out first solid-liquid separation to obtain sodium chromate solution and comprehensive sludge;
3) Mixing the sodium chromate solution in the step 2) with acid and a reducing agent, and then performing an acidification reduction reaction to obtain an acidification reduction reaction solution;
4) Mixing the acidification reduction reaction liquid in the step 3) with alkali to perform a second precipitation reaction to obtain a second suspension;
5) Sequentially carrying out second solid-liquid separation and water washing on the second suspension in the step 4) to obtain a chromium hydroxide mud cake;
6) Mixing the chromium hydroxide mud cake, water and lauric acid in the step 5), then carrying out neutralization reaction, and carrying out third solid-liquid separation on the obtained reaction liquid to obtain modified chromium hydroxide;
7) Calcining the modified chromium hydroxide in the step 6) to obtain chromium oxide powder;
the total chromium content of the chromium electroplating wastewater is 0.1-5 g/L, cr 3+ The concentration of the metal ions is 0.01-1g/L, and the content of other impurity metal ions is 0.01-1g/L.
Preferably, the pH value of the first precipitation reaction in the step 1) is 8.5-10.5.
Preferably, the electrooxidation in step 2) has a current density of 50 to 500A/m 2 The time of electrolytic oxidation is Cr 3+ Oxidation to CrO 4 2- 2-4 times of theoretical electrolysis time is needed.
Preferably, the reducing agent in the step 3) is at least one of sodium sulfite, sodium bisulfite and sodium metabisulfite.
Preferably, in the step 3), the pH value of the acidification reduction reaction is 2-3, the time of the acidification reaction is 0.45-0.55 h, the ORP value of the acidification reaction solution is controlled to be 230-270 mv, and the reaction time is controlled to be about 0.5 h.
Preferably, the pH value of the second precipitation reaction in the step 4) is 9.5-10.5.
Preferably, the washing in the step 5) is performed until the conductivity of the obtained washing liquid is lower than 200us/cm.
Preferably, in the step 6), the weight ratio of the chromium hydroxide mud cake to the lauric acid is 100:10-30; the dosage ratio of the chromium hydroxide mud cake to the water is 20-80 g:1000mL.
Preferably, the neutralization reaction in the step 6) is carried out at a temperature of 60-90 ℃ for 2-4 hours.
Preferably, the calcination temperature in the step 7) is 900-1300 ℃, and the calcination time is 2-5 h.
The beneficial technical effects are as follows: the invention provides a method for preparing chromium oxide powder by using chromium electroplating wastewater as a raw material, which comprises the steps of firstly carrying out first precipitation pretreatment on the chromium-containing wastewater to remove impurity metal ions in the wastewater, and using an electrolytic oxidation method to precipitate Cr (OH) in the process of removing impurities 3 Oxidation to CrO 4 2- Thereby further improving the recovery rate of chromium; crO in wastewater is treated by 4 2- By acidification reduction and then adding alkali to convert into Cr (OH) with high purity 3 Precipitating; cr (OH) with high purity 3 Washing the salt entrained by the precipitate, adding water and lauric acid for modification to enable Cr (OH) 3 The outermost surface of the crystal grain adsorbs a layer of carbon chains to become hydrophobic, and Cr (OH) is modified 3 The colloid is powdery, the agglomeration degree is low, the water content is low, and the Cr is obtained after calcination 2 O 3 The powder is pigment grade, has no agglomeration phenomenon, high purity and uniform particle size, and does not need additional crushing.
Detailed Description
The invention provides a method for preparing chromium oxide powder by taking chromium electroplating wastewater as a raw material, which comprises the following steps:
1) Mixing the chromium electroplating wastewater with alkali to perform a first precipitation reaction to obtain a first suspension;
2) Carrying out direct current electrolytic oxidation on the first suspension in the step 1) and then carrying out first solid-liquid separation to obtain sodium chromate solution and comprehensive sludge;
3) Mixing the sodium chromate solution in the step 2) with acid and a reducing agent, and then performing an acidification reduction reaction to obtain an acidification reduction reaction solution;
4) Mixing the acidification reduction reaction liquid in the step 3) with alkali to perform a second precipitation reaction to obtain a second suspension;
5) Sequentially carrying out second solid-liquid separation and water washing on the second suspension in the step 4) to obtain a chromium hydroxide mud cake;
6) Mixing the chromium hydroxide mud cake, water and lauric acid in the step 5), then carrying out neutralization reaction, and carrying out third solid-liquid separation on the obtained reaction liquid to obtain modified chromium hydroxide;
7) Calcining the modified chromium hydroxide in the step 6) to obtain chromium oxide powder;
the total chromium content of the chromium electroplating wastewater is 0.1-5 g/L, cr 3+ The concentration of the metal ions is 0.01-1g/L, and the content of other impurity metal ions is 0.01-1g/L.
The invention mixes the chromium electroplating wastewater with alkali to perform a first precipitation reaction to obtain a first suspension.
In the invention, the total chromium content in the chromium electroplating wastewater is preferably 0.1-5 g/L, more preferably 1-3 g/L; cr (Cr) 3+ The concentration of (2) is preferably 0.01 to 1g/L, more preferably 0.5 to 0.8g/L; the content of the other impurity metal ions is preferably 0.01 to 1g/L, more preferably 0.5 to 0.8g/L. The other impurity ions of the present invention preferably include Zn 2+ 、Cu 2+ 、Fe 3+ And Ni 2+ At least one of them.
In the present invention, the base is preferably sodium carbonate or sodium hydroxide. The invention is not particularly limited in the amount of alkali, and the pH value of the mixed solution of the chromium electroplating wastewater and the alkali can be adjusted to the pH value required by the first precipitation reaction. In the present invention, the pH of the first precipitation reaction is preferably 8.5 to 10.5, more preferably 9 to 10. The invention removes impurity metal ions in the wastewater by precipitation reaction of the chromium electroplating wastewater and alkali.
After the first suspension is obtained, the first suspension is subjected to direct current electrolytic oxidation and then subjected to first solid-liquid separation, so that sodium chromate solution and comprehensive sludge are obtained.
In the present invention,the electrooxidation current density is preferably 50-500A/m 2 More preferably 100 to 400A/m 2 Most preferably 200 to 250A/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The time of the electrolytic oxidation is preferably 2-4 times of the theoretical time of electrolysis; the theoretical time of electrolysis is based on Cr 3+ Content of Cr 3+ The electrolytically oxidized anode material is preferably titanium coated lead dioxide, titanium coated ruthenium iridium, titanium coated tantalum iridium or graphite calculated as electrochemical equivalent of 0.67 g/Ah; the cathode material of the electrolytic oxidation is preferably a stainless steel plate or a stainless steel mesh; when the cathode material is preferably a stainless steel mesh, the pore diameter of the stainless steel mesh is preferably 20 to 200 mesh, more preferably 50 to 150 mesh. The area of the cathode or anode is not particularly limited in the present invention, and is appropriately adjusted according to the volume of the solution required for electrolysis.
The invention precipitates Cr (OH) in the sediment by an electrolytic oxidation method 3 Oxidation to CrO 4 2- Thereby further improving the recovery rate of chromium without adding an oxidant.
The method of the present invention for solid-liquid separation is preferably filtration. The specific method of filtration is not particularly limited in the present invention, and methods well known to those skilled in the art may be used.
After obtaining sodium chromate solution and comprehensive sludge, the invention mixes the sodium chromate solution with acid and reducing agent to carry out acidification reduction reaction to obtain acidification reduction reaction liquid.
In the present invention, the acid is preferably hydrochloric acid or sulfuric acid; the amount of the acid used in the present invention is not particularly limited, and the pH of the solution obtained by mixing the sodium chromate solution with the acid and the reducing agent may be adjusted to the pH required for the acidification reduction reaction.
In the present invention, the reducing agent is preferably at least one of sodium sulfite, sodium bisulfite, and sodium metabisulfite; the reducing agent is preferably used in an amount of CrO 4 2- Reduction to Cr 3+ 1-2 times of theoretical amount.
In the present invention, the pH of the acidification reduction reaction is preferably 2 to 3, more preferably 2.5; the ORP value of the acidified reaction solution is controlled to be 230 to 270mV, preferably 240 to 260mV, and most preferably 250 to 255mV by adding a reducing agent. The reaction time is controlled to be about 0.5 h.
The invention uses the acidification reduction reaction to make CrO 4 2- Reduction to Cr 3+ 。
After the acidification reduction reaction liquid is obtained, the acidification reduction reaction liquid is mixed with alkali to carry out a second precipitation reaction, so as to obtain a second suspension.
In the present invention, the base is preferably sodium carbonate or sodium hydroxide; the pH of the second precipitation reaction is preferably 9.5 to 10.5, more preferably 10. The invention uses the second precipitation reaction to make Cr 3+ Conversion to Cr (OH) 3 And (5) precipitation.
After the second suspension is obtained, the second suspension is subjected to second solid-liquid separation and water washing in sequence to obtain the chromium hydroxide mud cake.
In the present invention, the second solid-liquid separation is preferably a press filtration separation. The specific method of the pressure filtration separation is not particularly limited, and a method well known to those skilled in the art can be selected.
The method of washing with water of the present invention is not particularly limited, and washing with water well known to those skilled in the art may be used. The washing with water according to the present invention is preferably water washing, and the washing is stopped when the conductivity of the obtained washing liquid is less than 200us/cm. The salt in the mud cake obtained by the second solid-liquid separation is washed away by water.
In the present invention, the filtrate obtained by the second solid-liquid separation and the washing liquid obtained by the washing are preferably fed into a wastewater treatment system.
After the chromium hydroxide mud cake is obtained, the chromium hydroxide mud cake, water and lauric acid are mixed and then modified, and the obtained reaction liquid is subjected to third solid-liquid separation to obtain the modified chromium hydroxide.
In the invention, the weight ratio of the chromium hydroxide mud cake to the lauric acid is preferably 100:10-30, more preferably 100:15-25, and most preferably 100:20; the dosage ratio of the chromium hydroxide mud cake to the water is preferably 20-80 g:1000mL, more preferably 30 to 70g:1000mL, most preferably 40 to 50g:1000mL.
In the present invention, the temperature of the modification is preferably 60 to 90 ℃, more preferably 70 to 80 ℃; the time for the modification is preferably 2 to 4 hours, more preferably 3 to 3.5 hours.
The invention preferably mixes the chromium hydroxide mud cake and water, then stirs the mixture into slurry, heats the slurry to the modification temperature, and then adds the lunar silicic acid for modification. According to the invention, the chromium hydroxide is modified by the lunar silicic acid, so that a layer of carbon chains adsorbed on the outermost surfaces of chromium hydroxide grains become hydrophobic, and the modified chromium hydroxide colloid is powdery, low in aggregation degree and low in water content.
The third solid-liquid separation method of the present invention is preferably a filter-press separation. The specific method of the pressure filtration separation is not particularly limited, and a method well known to those skilled in the art can be selected.
In the present invention, the filtrate obtained by the third solid-liquid separation is preferably fed into a wastewater treatment system.
After the modified chromium hydroxide is obtained, the modified chromium hydroxide is calcined to obtain the chromium oxide powder.
In the invention, the temperature of the modified chromium hydroxide is preferably 900-1300 ℃, more preferably 1000-1200 ℃, and most preferably 1100-1150 ℃; the calcination time is preferably 2 to 5 hours, more preferably 3 to 4 hours. The invention converts the modified chromium hydroxide into the chromium sesquioxide through calcination, and the chromium hydroxide is thermally decomposed in the calcination process to remove chemically bound water and volatile impurities (CO 2 、NO 2 、NH 3 Etc.), and finally obtaining the chromium oxide powder.
For a better understanding of the present invention, the following examples are further illustrated, but are not limited to the following examples.
Example 1
1) 5L of electroplating hard chromium rinse water (total chromium 2.4g/L, cr) 3+ 0.4g/L, the concentration of the rest metal ions is 0.1-0.5g/L, and the mixture is placed in a beaker, and 100g/L of sodium carbonate solution is added to adjust the pH of the solution to 9.5, so that the metal ions (Zn) in the solution 2+ 、Cr 3+ 、Cu 2+ 、Fe 3+ 、Ni 2+ Etc.) forming a corresponding hydroxide precipitate to obtain a first suspension;
2) Placing the first suspension obtained in the step 1) into an electrolytic tank, wherein an anode is made of titanium-based lead dioxide material, a cathode is made of stainless steel plate, and the effective area of the anode and the cathode is 300cm 2 Applying DC electrolysis with current density set at 220A/m 2 The direct current electrolysis time is set to be 2 times of the theoretical electrolysis time, namely 0.9h, and the suspension is filtered and separated after the electrolysis is finished to obtain Na 2 CrO 4 Solution and comprehensive sludge;
3) First at Na 2 CrO 4 Adding hydrochloric acid into the solution to control the pH value to be 2-2.5, adding sodium bisulphite to control the ORP value to be 230-270 mv, and carrying out acidification reduction reaction for about 0.5h, wherein the reduction is thorough when the ORP value is basically stable;
4) Adding liquid alkali after reduction, controlling pH value between 9.5-10.5, adding Cr 3+ Neutralization to Cr (OH) 3 Precipitating to obtain a second suspension;
5) Filtering the second suspension, and washing off Cr (OH) with neutral water after filtering 3 Salt entrained in the mud cake, and stopping washing when the conductivity of the washing water is lower than 200us/cm to obtain Cr (OH) 3 Mud cake;
6) Cr (OH) 3 The mud cake is mixed with a certain amount of pure water, stirred and beaten into slurry, and the solid concentration in the slurry is controlled at 40g/L. Heating to 75 ℃ the slurry temperature is adjusted according to Cr (OH) 3 Adding lauric acid 25% by weight, stirring for 2h, and performing pressure filtration again to obtain modified Cr (OH) 3 ；
7) Modified Cr (OH) 3 Feeding into a calciner for calcination treatment, controlling the calcination temperature at 1200 ℃ and setting the calcination time at 3h, and obtaining Cr after the calcination is finished 2 O 3 The powder grade is pigment grade, is dark green, has uniform particle size and has purity of 99.5 (Cr is used 2 O 3 Meter).
Example 1 calculation method of trivalent chromium oxidation theoretical electrolysis time:
trivalent chromium mass M (Cr) 3+ )＝0.4*5＝2g，Cr 3+ Is 0.67g/Ah, the current i=220×0.03=6.6a, the theoretical electrolysis time t=2/0.67/6.6=0.45 h.
Example 2
1) 10L of zinc-plating hexavalent chromium passivation scrapped groove liquid (total chromium 1.5g/L, cr) 3+ 0.7g/L, the concentration of the rest metal ions is 0.1-0.3g/L, and the solution pH is adjusted to 10.0 by adding 20% liquid alkali, so that the metal ions (Zn) in the solution 2 + 、Cr 3+ 、Cu 2+ 、Fe 3+ 、Ni 2+ Etc.) forming a corresponding hydroxide precipitate to obtain a first suspension;
2) Placing the first suspension obtained in the step 1) into an electrolytic tank, wherein an anode is made of titanium-coated ruthenium-iridium material, a cathode is made of a stainless steel mesh, the pore diameter of the stainless steel mesh is 100 meshes, and the effective area of the anode and the cathode is 500cm 2 D, applying direct current electrolysis, wherein the current density is set to be 200A/m 2 The direct current electrolysis time was set to 2.5 times the theoretical electrolysis time, i.e. 2.7h. Filtering and separating the suspension after the electrolysis is finished to obtain Na 2 CrO 4 Solution and comprehensive sludge;
3) First at Na 2 CrO 4 Adding sulfuric acid into the solution, controlling the pH value to be 2-2.5, adding sodium metabisulfite to control the ORP value to be 230-270 mv, performing acidification reduction reaction for about 0.5h, and indicating that the reduction is thorough when the ORP value is basically stable;
4) Adding liquid alkali after reduction, controlling pH value between 9.5-10.5, adding Cr 3+ Neutralization to Cr (OH) 3 Precipitating to obtain a second suspension;
5) Performing filter pressing separation on the second suspension, washing salt entrained in the obtained mud cake with water after the filter pressing is finished, and stopping washing when the conductivity of the washing water is lower than 200us/cm to obtain Cr (OH) 3 Mud cake;
6) Cr (OH) 3 Adding certain amount of pure water into the mud cake, stirring to obtain slurry, controlling solid concentration in the slurry at 60g/L, heating to 55deg.C, and pressing Cr (OH) 3 Adding lauric acid accounting for 20 percent of the weight, stirring for 4 hours, and then carrying out pressure filtration and separation again to obtain modified Cr (OH) 3 ；
7) Modified Cr (OH) 3 Feeding into calciner for calcination treatment, and controlling calcination temperature at 1300 deg.fSetting the calcination time to 4h at the temperature, and obtaining Cr after the calcination 2 O 3 The powder grade is pigment grade, is dark green, has uniform particle size and purity of 99.6 (Cr is used 2 O 3 Meter).
Example 3
1) 50L of electroplating decorative chromium rinse water (total chromium 1.7g/L, cr) 3+ 0.8g/L, and the concentration of the rest metal ions is 0.05-0.5 g/L) is placed in a reaction barrel, 30% liquid alkali is added to adjust the pH of the solution to 9.5, so that the metal ions (Zn) in the solution 2+ 、Cr 3 + 、Cu 2+ 、Fe 3+ 、Ni 2+ Etc.) forming a corresponding hydroxide precipitate to obtain a first suspension;
2) Placing the suspension obtained in the step 1) into an electrolytic tank, wherein an anode is made of graphite, a cathode is made of a stainless steel mesh, the pore diameter of the stainless steel mesh is 150 meshes, and the effective area of the anode and the cathode is 5000cm 2 Applying DC electrolysis with current density set at 180A/m 2 The direct current electrolysis time is set to be 3 times of the theoretical electrolysis time, namely 2.06h, and the suspension is filtered and separated after the electrolysis is finished to obtain Na 2 CrO 4 Solution and comprehensive sludge;
3) At Na (Na) 2 CrO 4 Adding sulfuric acid into the solution, controlling the pH value to be 2-2.5, adding sodium sulfite to control the ORP value to be 230-270 mv, performing acidification reduction reaction for about 0.5h, and indicating that the reduction is thorough when the ORP value is basically stable;
4) Adding liquid alkali after reduction, controlling pH value between 9.5-10.5, adding Cr 3+ Neutralization to Cr (OH) 3 Precipitating to obtain a second suspension;
5) After the reaction, cr (OH) 3 Filtering and separating the suspension, washing salt entrained in the obtained mud cake by tap water after the filtering is finished, and stopping washing when the conductivity of the washing water is lower than 200us/cm to obtain Cr (OH) 3 Mud cake;
6) Cr (OH) 3 Adding certain amount of pure water into the mud cake, stirring to obtain slurry, controlling solid concentration in the slurry to 45g/L, heating to 50deg.C, and pressing Cr (OH) 3 Adding lauric acid 30 wt%, stirring3.5h later, performing filter pressing separation again to obtain modified Cr (OH) 3 ；
7) Modified Cr (OH) 3 Feeding into a calciner for calcination treatment, controlling the calcination temperature at 1250 ℃ and the calcination time at 3.5h, and obtaining Cr after the calcination is finished 2 O 3 The powder grade is pigment grade, is dark green, has uniform particle size and purity of 99.3 (Cr is used 2 O 3 Meter).
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (10)
1. The method for preparing the chromium oxide powder by taking the chromium electroplating wastewater as the raw material is characterized by comprising the following steps of:
1) Mixing the chromium electroplating wastewater with alkali to perform a first precipitation reaction to obtain a first suspension;
2) Carrying out direct current electrolytic oxidation on the first suspension in the step 1) and then carrying out first solid-liquid separation to obtain sodium chromate solution and comprehensive sludge;
3) Mixing the sodium chromate solution in the step 2) with acid and a reducing agent, and then performing an acidification reduction reaction to obtain an acidification reduction reaction solution;
4) Mixing the acidification reduction reaction liquid in the step 3) with alkali to perform a second precipitation reaction to obtain a second suspension;
5) Sequentially carrying out second solid-liquid separation and water washing on the second suspension in the step 4) to obtain a chromium hydroxide mud cake;
6) Mixing the chromium hydroxide mud cake, water and lauric acid in the step 5), then carrying out neutralization reaction, and carrying out third solid-liquid separation on the obtained reaction liquid to obtain modified chromium hydroxide;
7) Calcining the modified chromium hydroxide in the step 6) to obtain chromium oxide powder;
the total chromium content of the chromium electroplating wastewater is 0.1-5 g/L, cr 3+ The concentration of the catalyst is 0.01-1g/L, other impuritiesThe content of the plasma metal ions is 0.01-1g/L.
2. The method according to claim 1, wherein the pH of the first precipitation reaction in step 1) is 8.5 to 10.5.
3. The method according to claim 1, wherein the electrooxidation in step 2) has a current density of 50 to 500A/m 2 The time of electrolytic oxidation is Cr 3+ Oxidation to CrO 4 2- 2-4 times of theoretical electrolysis time is needed.
4. The method according to claim 1, wherein the reducing agent in step 3) is at least one of sodium sulfite, sodium bisulfite, and sodium metabisulfite.
5. The method according to claim 1, wherein the pH value of the acidification reduction reaction in the step 3) is 2-3, the time of the acidification reaction is 0.45-0.55 h, and the ORP value of the acidification reaction solution is 230-270 mv.
6. The method according to claim 1, wherein the pH of the second precipitation reaction in step 4) is 9.5-10.5.
7. The method according to claim 1, wherein the washing in step 5) is performed until the conductivity of the obtained washing liquid is lower than 200us/cm.
8. The method according to claim 1, wherein the weight ratio of the chromium hydroxide mud cake to the lauric acid in the step 6) is 100:10-30; the dosage ratio of the chromium hydroxide mud cake to the water is 20-80 g:1000mL.
9. The method according to claim 1, wherein the neutralization reaction in step 6) is carried out at a temperature of 60 to 90 ℃ for a time of 2 to 4 hours.
10. The method according to claim 1, wherein the calcination in step 7) is performed at a temperature of 900 to 1300 ℃ for a time of 2 to 5 hours.
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