Step recovery method for fluorine and heavy metal in fluorine-containing heavy metal waste liquid

Abstract

The invention belongs to the technical field of environmental engineering and resource recycling, and particularly relates to a gradient recycling method for fluorine and heavy metal in fluorine-containing heavy metal waste liquid. The method comprises the following steps: pretreating the fluorine-containing heavy metal waste liquid, mixing the pretreated waste liquid with soluble calcium salt, and carrying out a precipitation defluorination reaction to obtain calcium fluoride and defluorination waste liquid; adjusting the pH value of the defluorination waste liquid to be greater than or equal to 9, and carrying out precipitation reaction to obtain heavy metal hydroxide precipitate and treated waste liquid; and the heavy metal hydroxide precipitate is subjected to acid dissolution, solvent extraction separation, reverse extraction and electrolysis or salification, and a metal copper elementary substance, a metal nickel elementary substance and a cobalt salt product are obtained. According to the method provided by the invention, cascade separation of fluorine and heavy metal elements can be realized, the separation selectivity is good, the recovery rate and purity of heavy metal and fluorine are high, and the technical problems of poor separation selectivity, low resource recovery purity and low value-added utilization degree in the existing fluorine-containing heavy metal waste liquid treatment are solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental engineering and resource recycling, and particularly relates to a method for gradient recovery of fluorine and heavy metals from fluorine-containing heavy metal waste liquid. BACKGROUND

[0002] With the rapid development of high-end manufacturing industries such as integrated circuits, photovoltaic manufacturing, and rare earth smelting, a large amount of waste liquid containing fluorine ions and heavy metal ions (such as copper, nickel, cobalt, etc.) is generated. The fluorine concentration in these waste liquids is usually 5000-30000 mg / L, and the heavy metal concentration is 1000-15000 mg / L, which is highly corrosive and toxic, posing a serious threat to the environment and human health. At the same time, fluorine and heavy metals are important industrial resources with high recovery value.

[0003] Currently, the methods for treating fluorine-containing heavy metal waste liquid mainly include chemical precipitation, ion exchange, membrane separation, etc. However, the traditional methods have the following problems: (1) fluorine ions and heavy metal ions are easy to form complexes, increasing the difficulty of separation and resulting in poor separation effect; (2) the products of traditional precipitation method are mixed, making it difficult to achieve separate recovery. SUMMARY

[0004] The present application provides a method for gradient recovery of fluorine and heavy metals from fluorine-containing heavy metal waste liquid, which can achieve gradient separation of fluorine and heavy metal elements, has good separation selectivity, high recovery rate of heavy metals and fluorine, and high purity, solving the technical problems of poor separation selectivity, low resource recovery purity, and low value-added utilization in the treatment of existing fluorine-containing heavy metal waste liquid.

[0005] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme: The present application provides a method for gradient recovery of fluorine and heavy metals from fluorine-containing heavy metal waste liquid, comprising the following steps: (1) pretreating the fluorine-containing heavy metal waste liquid to obtain pretreated waste liquid, wherein the fluorine-containing heavy metal waste liquid contains heavy metal elements and fluorine ions, the heavy metal elements include copper, cobalt and nickel, and the pretreatment comprises sequentially adjusting the pH value and sand filtering; (2) mixing the pretreated waste liquid with a soluble calcium salt to perform a precipitation defluorination reaction, and obtaining calcium fluoride and defluorination waste liquid after solid-liquid separation; (3) adjusting the pH value of the defluorination waste liquid to be greater than or equal to 9 to perform a precipitation reaction, and obtaining heavy metal hydroxide precipitate and treated waste liquid after solid-liquid separation; (4) performing acid dissolution of the heavy metal hydroxide precipitate with an acid solution to obtain a heavy metal salt solution; (5) sequentially performing solvent extraction separation and back extraction on the heavy metal salt solution to obtain a copper ion solution, a cobalt ion solution and a nickel ion solution; (6) electrolyzing the copper ion solution and the nickel ion solution respectively to obtain elemental copper and elemental nickel; and preparing a cobalt salt product from the cobalt ion solution.

[0006] Preferably, in step (1), the pH value is adjusted to 6-7; when the heavy metal complex is contained in the heavy metal-containing fluorine-containing waste liquid, an oxidizing agent is further added to the filtrate obtained by sand filtration, and the oxidizing agent includes one or more of hydrogen peroxide, sodium hypochlorite and ozone.

[0007] Preferably, in step (2), the soluble calcium salt includes calcium chloride; the molar ratio of calcium in the soluble calcium salt to fluorine ions in the heavy metal-containing fluorine-containing waste liquid is 1.05-1.2:1; the temperature of the precipitation defluorination reaction is 25-35°C, and the time is 30-60 min; the precipitation dechlorination reaction is carried out under stirring, and the stirring speed is 100-200 rpm.

[0008] Preferably, in step (2), after the precipitation dechlorination reaction is completed, the reaction liquid obtained by the precipitation dechlorination reaction is further subjected to the solid-liquid separation after being left to stand, and the standing time is 1-2 h; the solid-liquid separation includes gravity sedimentation or pressure filtration.

[0009] Preferably, in step (3), the pH value is 9-10.5; the reagent for adjusting the pH value of the defluorination waste liquid is a sodium hydroxide solution, and the mass percentage of NaOH in the sodium hydroxide solution is 20-30%; the time of the precipitation reaction is 20-40 min; and the heavy metal hydroxide precipitate includes a mixture of copper hydroxide, cobalt hydroxide and nickel hydroxide.

[0010] Preferably, in step (4), the acid solution is a sulfuric acid solution, and the mass percentage of H2SO4 in the sulfuric acid solution is 10-15%; the pH value of the acid dissolution is 1.5-2.5.

[0011] Preferably, in step (5), the solvent extraction separation includes: selectively extracting copper ions from the heavy metal salt solution by using LIX84-I extractant to obtain an organic phase loaded with copper ions and a residual aqueous phase; and selectively extracting cobalt ions from the residual aqueous phase by using Cyanex 272 extractant to obtain an organic phase loaded with cobalt ions and an aqueous phase enriched in nickel ions.

[0012] Preferably, the conditions for selectively extracting copper ions include: a pH value of 2-3, a volume ratio of the organic phase to the aqueous phase of 0.5-3:1, and an extraction stage number of 2-4 stages; the conditions for selectively extracting cobalt ions include: a pH value of 5-6, a volume ratio of the organic phase to the aqueous phase of 0.5-3:1, and an extraction stage number of 3-5 stages; The concentration of nickel ions in the nickel ion-rich aqueous phase is greater than or equal to 8500 mg / L.

[0013] Preferably, in step (6), the electrolysis conditions of the copper ion solution include: the current density is 100-300 A / m 2 , the cell voltage is 2-6 V; the purity of the elemental copper is greater than or equal to 99.7%; The electrolysis conditions of the nickel ion solution include: the current density is 100-300 A / m 2 , the cell voltage is 2-6 V; the purity of the elemental nickel is greater than or equal to 99.2%; The cobalt salt product is cobalt sulfate heptahydrate, and the purity of the cobalt sulfate heptahydrate is greater than or equal to 99%.

[0014] Preferably, the concentration of fluorine ions in the fluorine-containing heavy metal waste liquid is 5000-30000 mg / L, and the concentration of heavy metal elements is 1000-15000 mg / L.

[0015] The present application provides a method for the step-by-step recovery of fluorine and heavy metals from a fluorine-containing heavy metal waste liquid, comprising the following steps: (1) pretreating the fluorine-containing heavy metal waste liquid to obtain a pretreated waste liquid, wherein the fluorine-containing heavy metal waste liquid comprises heavy metal elements and fluorine ions, and the heavy metal elements comprise copper elements, cobalt elements and nickel elements, and the pretreatment comprises sequentially adjusting the pH value and sand filtering; (2) mixing the pretreated waste liquid with a soluble calcium salt to perform a fluorine removal precipitation reaction, and then performing solid-liquid separation to obtain calcium fluoride and a fluorine-removed waste liquid; (3) adjusting the pH value of the fluorine-removed waste liquid to be greater than or equal to 9 to perform a precipitation reaction, and then performing solid-liquid separation to obtain a heavy metal hydroxide precipitate and a treated waste liquid; (4) performing acid dissolution of the heavy metal hydroxide precipitate with an acid solution to obtain a heavy metal salt solution; (5) sequentially performing solvent extraction separation and back extraction on the heavy metal salt solution to obtain a copper ion solution, a cobalt ion solution and a nickel ion solution; (6) performing electrolysis on the copper ion solution and the nickel ion solution, respectively, to obtain elemental copper and elemental nickel; and preparing a cobalt salt product from the cobalt ion solution. The method provided by the present application adopts a step-by-step precipitation method of first precipitating fluorine ions and then precipitating heavy metal elements, which can realize the effective recovery of fluorine ions. For the heavy metal hydroxide precipitate, after acid dissolution, solvent extraction separation is adopted, which realizes the separation of copper ions, cobalt ions and nickel ions, and finally realizes the recovery of the three kinds of heavy metals through electrolysis or salting. The recovery method provided by the present application based on step-by-step precipitation-solvent extraction-electrolysis can realize the step-by-step separation and value-added utilization of fluorine and heavy metals in the fluorine-containing waste liquid, and solves the technical problems of poor separation selectivity, low resource recovery purity and low value-added utilization degree in the existing fluorine-containing heavy metal waste liquid treatment method. Compared with the prior art, the present application has the following beneficial effects: (1) The method provided by the application can realize efficient separation of different qualities: the application realizes step-by-step separation of fluorine and heavy metals, and the fluorine recovery rate is greater than or equal to 95%, and the heavy metal recovery rate is greater than or equal to 98%; (2) The product of the method provided by the application has high purity: the purity of CaF2 is greater than or equal to 98%, the recovery purity of Cu is greater than or equal to 99.5%, the recovery purity of Ni is greater than or equal to 99.2%, and the recovery purity of Co is greater than or equal to 99.0%; (3) The method provided by the application has significant value-added utilization: CaF2 can be used to prepare electronic-grade fluorides, and the value is increased by 5 to 10 times; the recovered high-purity metals can be directly used in the electronic industry, and the value is increased by 3 to 8 times; (4) The method provided by the application has strong adaptability: it is suitable for treatment of waste liquid with a fluorine concentration of 5,000 to 30,000 mg / L and a heavy metal concentration of 1,000 to 15,000 mg / L; (5) The method provided by the application has significant economic benefits: the resource utilization benefit can be 1.5 to 3 times the treatment cost; (6) The method provided by the application is environmentally friendly: no secondary pollution, and the final effluent meets the discharge standard. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A flowchart of a method for step-by-step recovery of fluorine and heavy metals from a fluorine-containing heavy metal waste liquid is provided. DETAILED DESCRIPTION

[0017] The application provides a method for step-by-step recovery of fluorine and heavy metals from a fluorine-containing heavy metal waste liquid, comprising the following steps: (1) pretreating the fluorine-containing heavy metal waste liquid to obtain pretreated waste liquid, wherein the fluorine-containing heavy metal waste liquid comprises heavy metal elements and fluorine ions, the heavy metal elements comprise copper elements, cobalt elements and nickel elements, and the pretreatment comprises sequentially adjusting the pH value and sand filtering; (2) mixing the pretreated waste liquid and a soluble calcium salt to perform a fluorine removal reaction by precipitation, and obtaining calcium fluoride and fluorine removal waste liquid after solid-liquid separation; (3) adjusting the pH value of the fluorine removal waste liquid to be greater than or equal to 9 to perform a precipitation reaction, and obtaining heavy metal hydroxide precipitate and treated waste liquid after solid-liquid separation; (4) performing acid dissolution on the heavy metal hydroxide precipitate and an acid solution to obtain a heavy metal salt solution; (5) sequentially performing solvent extraction separation and back extraction on the heavy metal salt solution to obtain a copper ion solution, a cobalt ion solution and a nickel ion solution; (6) performing electrolysis on the copper ion solution and the nickel ion solution respectively to obtain metallic copper and metallic nickel; and preparing a cobalt salt product from the cobalt ion solution.

[0018] In the present application, all the preparation raw materials / components are commercially available products well known to those skilled in the art, unless otherwise specified.

[0019] In the present application, the fluorine-containing heavy metal waste liquid is pretreated to obtain a pretreated waste liquid, the fluorine-containing heavy metal waste liquid comprises heavy metal elements and fluoride ions, the heavy metal elements comprise copper elements, cobalt elements and nickel elements, and the pretreatment comprises sequentially performing pH value adjustment and sand filtration.

[0020] In the present application, the concentration of the fluoride ions in the fluorine-containing heavy metal waste liquid is preferably 5000-30000 mg / L, and in the embodiments, it can be 12000 mg / L. The concentration of the heavy metal elements in the fluorine-containing heavy metal waste liquid is preferably 1000-15000 mg / L. In the present application, the concentration of the copper ions is preferably 1000-5000 mg / L, and in the embodiments, it can be 3500 mg / L. The concentration of the nickel ions is preferably 1000-4000 mg / L, and in the embodiments, it can be 1800 mg / L.

[0021] In the present application, the pH value is preferably adjusted to 6-7, and in the embodiments, it can be 6.5±0.2. In the present application, the sand filtration is preferably used to remove the suspended solids and organic impurities in the fluorine-containing heavy metal waste liquid.

[0022] In the present application, when the fluorine-containing heavy metal waste liquid contains heavy metal complexes (for example, nickel complexes), the present application preferably further comprises adding an oxidizing agent to the filtrate obtained by the sand filtration. The oxidizing agent preferably comprises one or more of hydrogen peroxide, sodium hypochlorite and ozone, and in the embodiments, it can be hydrogen peroxide. The molar ratio of H2O2 in the hydrogen peroxide to the heavy metal complexes in the fluorine-containing heavy metal waste liquid is preferably 2-2.5:1.

[0023] After obtaining the pretreated waste liquid, the present application mixes the pretreated waste liquid and a soluble calcium salt to perform a precipitation defluorination reaction, and after solid-liquid separation, calcium fluoride and defluorinated waste liquid are obtained.

[0024] In the present application, the soluble calcium salt preferably comprises calcium chloride. In the specific embodiments of the present application, the calcium chloride is preferably used in the form of a calcium chloride solution, and the mass percentage of calcium chloride in the calcium chloride solution is 10-25%, and in the embodiments, it can be 20%. The molar ratio of the calcium element in the soluble calcium salt to the fluoride ions in the fluorine-containing heavy metal waste liquid is preferably 1.05-1.2:1, and in the embodiments, it can be 1.1:1. The temperature of the precipitation defluorination reaction is preferably 25-35℃, and in the embodiments, it can be 30±2℃. The time of the precipitation defluorination reaction is preferably 30-60 min, and in the embodiments, it can be 45 min. The precipitation defluorination reaction is preferably performed under stirring, and the stirring speed is preferably 100-200 rpm, and in the embodiments, it can be 150 rpm.

[0025] In the present application, after the precipitation dechlorination reaction is completed, the present application preferably further comprises that the reaction liquid obtained by the precipitation dechlorination reaction is allowed to stand and then the solid-liquid separation is performed. The standing temperature is preferably 25-35℃, and in the examples, it can be 30±2℃. The standing time is preferably 1-2h. The solid-liquid separation preferably comprises gravity sedimentation or pressure filtration.

[0026] In the present application, the solid-liquid separation obtains initial calcium fluoride. The present application preferably further comprises that the initial calcium fluoride is sequentially subjected to water washing and drying to obtain pure calcium fluoride. In the present application, the water washing is preferably performed using deionized water, and the number of times of water washing is preferably 1-3 times. The drying temperature is preferably 70-80℃, and the time is preferably 24-36h. The purity of the pure calcium fluoride is preferably ≥98.5%.

[0027] In the present application, the calcium fluoride is preferably used as a fluorinated chemical raw material or for preparing electronic-grade fluorides.

[0028] After the defluorination waste liquid is obtained, the present application adjusts the pH value of the defluorination waste liquid to ≥9 for a precipitation reaction, and then performs a solid-liquid separation to obtain a heavy metal hydroxide precipitate and a treated waste liquid. In the present application, the pH value is preferably 9-10.5, and in the examples, it can be 10.0±0.2. The reagent used for adjusting the pH value of the defluorination waste liquid is preferably a sodium hydroxide solution, and the mass percentage of NaOH in the sodium hydroxide solution is preferably 20-30%, and in the examples, it can be 25%. The amount of the sodium hydroxide solution used is preferably determined according to the pH value of 9-10.5. The time of the precipitation reaction is preferably 20-40min, and in the examples, it can be 30min. The present application does not have special requirements for the specific implementation mode of the solid-liquid separation. The heavy metal hydroxide precipitate comprises a mixture of copper hydroxide, cobalt hydroxide and nickel hydroxide.

[0029] In the present application, the conditions of the treated waste water preferably comprise: the fluorine ion concentration of the effluent <10mg / L; the heavy metal concentration of the effluent: Cu 2+ <0.5mg / L, Ni 2+ <0.5mg / L.

[0030] After the heavy metal hydroxide precipitate is obtained, the present application performs acid dissolution on the heavy metal hydroxide precipitate and an acid solution to obtain a heavy metal salt solution. In the present application, the acid solution is preferably a sulfuric acid solution. The mass percentage of H2SO4 in the sulfuric acid solution is preferably 10-15%. The pH value of the acid dissolution is preferably 1.5-2.5, and in the examples, it can be 2.0±0.1. The amount of the acid solution used is preferably determined according to the pH value of 1.5-2.5 of the acid dissolution.

[0031] After obtaining the heavy metal salt solution, the heavy metal salt solution is sequentially subjected to solvent extraction separation and back extraction to obtain a copper ion solution, a cobalt ion solution and a nickel ion solution.

[0032] In the present application, the solvent extraction separation is carried out in an extraction column, which includes a sieve plate column or a pulse extraction column.

[0033] In the present application, the solvent extraction separation preferably includes: selectively extracting copper ions from the heavy metal salt solution by using LIX84-I extractant to obtain an organic phase loaded with copper ions and a remaining aqueous phase; selectively extracting cobalt ions from the remaining aqueous phase by using Cyanex272 extractant to obtain an organic phase loaded with cobalt ions and an aqueous phase enriched with nickel ions.

[0034] In the present application, the conditions for selectively extracting copper ions preferably include: the pH value is preferably 2-3. The volume (O / A) ratio of the organic phase to the aqueous phase is preferably 0.5-3:1, which can be 1:1 in the examples. The extraction stage is preferably 2-4 stages, which can be 3 stages in the examples. In the present application, the extraction rate of the copper ions is >99.8%.

[0035] In the present application, the conditions for selectively extracting cobalt ions preferably include: the pH value is preferably 5-6. The volume (O / A) ratio of the organic phase to the aqueous phase is preferably 0.5-3:1, which can be 2:1 in the examples. The extraction stage is preferably 3-5 stages, which can be 4 stages in the examples. In the present application, the extraction rate of the cobalt ions is >99.5%.

[0036] The present application preferably separately back extracts the organic phase loaded with copper ions and the organic phase loaded with cobalt ions to obtain a copper ion solution and a cobalt ion solution. The present application does not have special requirements for the specific implementation of the back extraction.

[0037] In the present application, the concentration of nickel ions in the aqueous phase enriched with nickel ions is preferably ≥8500 mg / L.

[0038] After obtaining the copper ion solution, the cobalt ion solution and the nickel ion solution, the present application separately electrolyzes the copper ion solution and the nickel ion solution to obtain metallic copper and metallic nickel; and prepares a cobalt salt product from the cobalt ion solution.

[0039] In the present application, the conditions for electrolyzing the copper ion solution preferably include: the cathode can be a titanium-based material, and the anode can be an insoluble titanium anode; the current density is preferably 100-300 A / m 2 , which can be 200 A / m 2 in the examples. The cell voltage is preferably 2-6 V, which can be 3, 4 or 5 V in the examples. In the present application, the purity of the metallic copper is ≥99.7%.

[0040] In the present application, the conditions for electrolysis of the nickel ion solution preferably include that the cathode can be a titanium-based material, and the anode can be an insoluble titanium anode; the current density is preferably 100-300 A / m 2 , and in the examples can be 200 A / m 2 . The cell voltage is preferably 2-6 V, and in the examples can be 3, 4 or 5 V. In the present application, the purity of the metallic nickel is preferably ≥ 99.3%.

[0041] In the present application, the cobalt salt product can be cobalt sulfate heptahydrate. The purity of the cobalt sulfate heptahydrate is preferably ≥ 99%.

[0042] The present application also provides a device for use in the method for gradient recovery of fluorine and heavy metals from a fluorine-containing heavy metal waste liquid according to the technical solutions described above, comprising, in sequence, a pretreatment unit, a calcium salt precipitation reactor, a solid-liquid separation device, a pH adjusting tank, an extraction separation system and an electrolytic recovery device.

[0043] In order to further illustrate the present application, the technical solutions provided by the present application are described in detail below in conjunction with examples, but they should not be understood as limiting the scope of protection of the present application.

[0044] Example 1 The present example provides a method for gradient recovery of fluorine and heavy metals from a fluorine-containing heavy metal waste liquid, which specifically comprises the following steps: The fluorine-containing heavy metal waste liquid treated in the present example is integrated circuit etching waste liquid, wherein the concentration of F - is 12000 mg / L, the concentration of Cu 2+ is 3500 mg / L, and the concentration of Ni 2+ is 1800 mg / L. The integrated circuit etching waste liquid is pretreated to obtain pretreated waste liquid. (1) The pH of the integrated circuit etching waste liquid is adjusted to 6.5±0.2; (2) The suspended solids in the integrated circuit etching waste liquid are removed by sand filtration; (3) The integrated circuit etching waste liquid is detected, and if it contains metal complexes, hydrogen peroxide is added to the integrated circuit etching waste liquid, wherein the molar ratio of H2O2 in the hydrogen peroxide to the heavy metal complexes in the integrated circuit etching waste liquid is preferably 2:1.

[0045] Calcium salt precipitation for defluorination: (1) 20wt% CaCl2 solution is added to the pretreated waste liquid; (2) The molar ratio of Ca 2+ in the CaCl2 solution to F - in the integrated circuit etching waste liquid is controlled to be 1.1:1; (3) Mechanical stirring intensity 150 rpm, reaction time 45 min; (4) Reaction temperature controlled at 30 ± 2℃.

[0046] Solid-liquid separation and fluorine recovery: (1) Solid-liquid separation (using gravity sedimentation or pressure filtration) after standing and settling for 2 h; (2) CaF2precipitate washed with deionized water for 3 times; (3) Dried at 80℃ for 24 h to obtain CaF2product with purity of 98.5%.

[0047] Heavy metal precipitation: (1) Filtrate pH adjusted to 10.0 ± 0.2; (2) 25% NaOH solution added as precipitant; (3) Solid-liquid separation (gravity sedimentation or pressure filtration) after reaction for 30 min.

[0048] Acid dissolution: (1) Heavy metal hydroxide precipitate dissolved with 10wt% H2SO4; (2) pH adjusted to 2.0 ± 0.1 to obtain metal sulfate solution.

[0049] Solvent extraction separation: (1) Copper extraction: LIX84-I extractant used to selectively extract copper ions under pH 2.0~3.0, O / A = 1:1, extraction for 3 stages, copper extraction rate > 99.8%; (2) Cobalt extraction: Cyanex 272 extractant used to selectively extract cobalt ions under pH 5.0~6.0, O / A = 2:1, extraction for 4 stages, cobalt extraction rate > 99.5%; (3) Nickel enrichment: nickel concentration in aqueous phase increased to 8500 mg / L.

[0050] Electrolytic recovery: (1) Copper electrolysis: current density 200 A / m 2 , cell voltage preferably 5 V, recovery purity 99.7%; (2) Nickel electrolysis: current density 150 A / m 2 , cell voltage preferably 5 V, recovery purity 99.3%; (3) Cobalt salt preparation: cobalt sulfate heptahydrate prepared, purity 99.1%.

[0051] The effects of the embodiment are as follows: the effluent fluoride ion concentration is <10 mg / L; the effluent heavy metal concentration is Cu <0.5 mg / L, Ni <0.5 mg / L; the CaF2 recovery amount is 34.2 kg / t of waste liquid, and the purity is 98.5%; the metal recovery is Cu 3.42 kg / t (purity 99.7%), Ni 1.76 kg / t (purity 99.3%), and CoSO4·7H2O 0.85 kg / t; and the total resource utilization benefit is 15,600 yuan / t of waste liquid.

[0052] It can be known from the above embodiment that the method provided by the application adopts a step-by-step precipitation method of precipitating fluoride ions first and then precipitating heavy metal elements, and can realize effective recovery of fluoride ions; for heavy metal hydroxide precipitation, solvent extraction separation is adopted after acid dissolution, realizing separation of copper ions, cobalt ions and nickel ions, and finally realizing recovery of the three kinds of heavy metals through electrolysis or salting. The recovery method provided by the application based on step-by-step precipitation-solvent extraction-electrolysis can realize gradient separation and value-added utilization of fluoride and heavy metals in fluoride-containing waste liquid, and solves the technical problems of poor separation selectivity, low resource recovery purity and low value-added utilization degree in the existing fluoride-containing heavy metal waste liquid treatment method.

[0053] Although the above embodiment makes a detailed description of the application, it is only a part of the embodiments of the application, not all the embodiments, and other embodiments can be obtained under the premise of no creativity according to the embodiment, and these embodiments all belong to the protection scope of the application.

Claims

1. A method for stepwise recovery of fluorine and heavy metals from a fluorine-containing heavy metal waste liquid, characterized by, The method comprises the following steps: (1) pretreating a fluorine-containing heavy metal waste liquid to obtain a pretreated waste liquid, the fluorine-containing heavy metal waste liquid comprising heavy metal elements and fluoride ions, the heavy metal elements comprising copper elements, cobalt elements and nickel elements, the pretreatment comprising sequentially adjusting a pH value and sand filtering; (2) mixing the pretreated waste liquid and a soluble calcium salt to perform a precipitation defluorination reaction, and then performing solid-liquid separation to obtain calcium fluoride and a defluorination waste liquid; (3) adjusting the defluorination waste liquid to a pH value of greater than or equal to 9 to perform a precipitation reaction, and then performing solid-liquid separation to obtain heavy metal hydroxide precipitates and a treated waste liquid; (4) performing acid dissolution on the heavy metal hydroxide precipitates and an acid solution to obtain a heavy metal salt solution; (5) sequentially performing solvent extraction separation and back extraction on the heavy metal salt solution to obtain a copper ion solution, a cobalt ion solution and a nickel ion solution; (6) performing electrolysis on the copper ion solution and the nickel ion solution respectively to obtain elemental copper and elemental nickel, and preparing a cobalt salt product from the cobalt ion solution.

2. The process for the stepwise recovery of fluorine and heavy metals from a fluorine- and heavy metal-containing waste solution according to claim 1, characterized in that, In step (1), the pH value is adjusted to 6-7; when the fluorine-containing heavy metal waste liquid contains heavy metal complexes, an oxidizing agent is further added to the filtrate obtained through the sand filtering, and the oxidizing agent comprises one or more of hydrogen peroxide, sodium hypochlorite and ozone.

3. The process for the stepwise recovery of fluorine and heavy metals from a fluorine- and heavy metal-containing waste solution according to claim 1, characterized in that, In step (2), the soluble calcium salt comprises calcium chloride; the molar ratio of calcium elements in the soluble calcium salt to fluoride ions in the fluorine-containing heavy metal waste liquid is 1.05-1.2:1; the precipitation defluorination reaction is performed at a temperature of 25-35°C for 30-60 min, and the precipitation defluorination reaction is performed under stirring at a stirring speed of 100-200 rpm.

4. The process for the stepwise recovery of fluorine and heavy metals from a fluorine- and heavy metal-containing waste solution according to claim 1 or 3, characterized in that, In step (2), after the precipitation defluorination reaction is completed, the reaction liquid obtained through the precipitation defluorination reaction is further allowed to stand before the solid-liquid separation is performed, and the standing time is 1-2 h; the solid-liquid separation comprises gravity sedimentation or pressure filtration.

5. The process for stepwise recovery of fluorine and heavy metals from fluorine- containing heavy metal waste liquid according to claim 1, characterized by, In step (3), the pH value is 9-10.5; the reagent used for adjusting the pH value of the defluorination waste liquid is a sodium hydroxide solution, the mass percentage of NaOH in the sodium hydroxide solution is 20-30%, the precipitation reaction is performed for 20-40 min, and the heavy metal hydroxide precipitates comprise a mixture of copper hydroxide, cobalt hydroxide and nickel hydroxide.

6. The process for the stepwise recovery of fluorine and heavy metals from a fluorine- and heavy metal-containing waste solution according to claim 1, characterized in that, In step (4), the acid solution is a sulfuric acid solution, the mass percentage of H2SO4 in the sulfuric acid solution is 10-15%, and the pH value of the acid dissolution is 1.5-2.

5.

7. The process for stepwise recovery of fluorine and heavy metals from fluorine- containing heavy metal waste liquid according to claim 1, characterized by, In step (5), the solvent extraction separation comprises: selectively extracting copper ions from the heavy metal salt solution by using LIX84-I extractant to obtain an organic phase loaded with copper ions and a remaining aqueous phase; and selectively extracting cobalt ions from the remaining aqueous phase by using Cyanex 272 extractant to obtain an organic phase loaded with cobalt ions and an aqueous phase enriched in nickel ions.

8. The process for the stepwise recovery of fluorine and heavy metals from a fluoro-heavy metal waste solution according to claim 7, characterized in that, The conditions for selectively extracting copper ions comprise: a pH value of 2-3, a volume ratio of the organic phase to the aqueous phase of 0.5-3:1, and an extraction stage number of 2-4. The conditions for selectively extracting cobalt ions include: pH value of 5-6, volume ratio of organic phase to aqueous phase of 0.5-3:1, and extraction stage number of 3-5 stages. The concentration of nickel ions in the aqueous phase enriched with nickel ions is greater than or equal to 8500 mg / L.

9. The process for stepwise recovery of fluorine and heavy metals from fluorine- and heavy metal-containing waste solutions according to claim 1, characterized in that, In step (6), the conditions for electrolysis of the copper ion solution include: current density of 100-300 A / m 2 , cell voltage of 2-6 V; purity of metallic copper of ≥ 99.7%; The conditions for electrolysis of the nickel ion solution include: current density is 100-300 A / m 2 , cell voltage is 2-6 V; purity of metallic nickel is ≥ 99.2%; The cobalt salt product is cobalt sulfate heptahydrate, and the purity of the cobalt sulfate heptahydrate is greater than or equal to 99%.

10. The process for the stepwise recovery of fluorine and heavy metals from a fluoro-heavy metal waste solution according to claim 1, characterized in that, The concentration of fluorine ions in the fluorine-containing heavy metal waste liquid is 5000-30000 mg / L, and the concentration of heavy metal elements is 1000-15000 mg / L.

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