METHOD AND APPARATUS FOR THE RECOVERY AND DEEP TREATMENT OF POLLUTED ACID

Abstract

A method and an apparatus for recovery and deep treatment of a polluted acid. The method comprises the following main steps: (1) selectively adsorbing rare and noble metals, such as rhenium, selenium and the like; (2) separating copper from arsenic to recover the copper; (3) carrying out efficient vulcanization to perform deep arsenic removal; (4) carrying out electrodialysis to pre-concentrate acid; (5) evaporating and concentrating the acid; (6) carrying out an air-stripping method to remove fluorine and chlorine. The polluted acid treatment apparatus mainly comprises a precision filtering tank, a special adsorbing tank, a copper-arsenic separation device, a vulcanization device, an electrodialysis device, an evaporative concentration device, and an air-stripping device. The method and the apparatus can implement efficient recovery of valuable elements in polluted acid wastewater and separate treatment harmful elements, has obvious economical, social and environmental benefits, and has wide application prospects.

Claims

1. A method for the recovery and deep treatment of polluted acid, characterized in that, comprising the steps of: (1) pretreatment and selective adsorption: polluted acid wastewater is first filtered through a precision filter to remove suspended matters, and then enters a special adsorbing tank to selectively adsorb rare and noble metals, such as rhenium and selenium; (2) copper is separated from arsenic by using arsenic sulfide or arsenic sulfide residue; (3) after the separation of copper and arsenic, the filtrate is subjected to deep arsenic removal by using a vulcanizing agent, and the obtained arsenic sulfide residue is reused in step (2); (4) after the separation of arsenic residue, the filtrate enters the electrodialysis device for the pre-concentration of the acid and the separation and enrichment of the fluorine and chlorine; (5) the concentrate from the electrodialysis device enters the evaporative concentration device to concentrate acid and the condensation water is recycled; and (6) air-stripping separation method is used to removal of fluorine and chlorine in the concentrated acid solution, and then the acid can be reused in sulfuric acid production system, and high fluorine- and chlorine mixed acid is sold or further recycled.

2. The method according to claim 1, characterized in that, the polluted acid wastewater in step (1) is the acidic wastewater generated from the scrubbing of flue gas produced in the non-ferrous metal smelting, during the acid-production and purification process, the polluted acid has a mass concentration of sulfuric acid between 2% and 8%, and contains one or more of copper, lead, zinc, cadmium, arsenic, nickel, cobalt, manganese, tin, antimony, selenium, mercury, indium, and rhenium ions, as well as fluorine, chlorine, sulfate radical and hydrogen ions.

3. The method according to claim 1, characterized in that, the pore size of the filter material used during the precision filtration in step (1) is 0.5 to 10 m.

4. The method according to claim 1, characterized in that, the special adsorbing tank of step (1) is filled with special adsorbing filler which is ion exchange material functionalized by nitrogen-containing heterocyclic compound.

5. The method according to claim 1, characterized in that, during the separation of copper and arsenic in step (2), the arsenic sulfide or arsenic sulfide residue is added to the polluted acid wastewater which is treated with adsorbing tank at an As/Cu molar ratio of 1 to 5:1.

6. The method according to claim 1, characterized in that, in step (2), the separation of copper and arsenic is reacted at 40 to 80 C., and filtered to obtain copper-enriched residue and arsenic-enriched solution.

7. The method according to claim 1, characterized in that, in step (2), the separation of copper and arsenic is reacted for 1 to 3 h.

8. The method according to claim 1, characterized in that, the vulcanizing agent used in step (3) is one or more of sodium sulfide, sodium hydrosulfide, calcium sulfide, barium sulfide, and hydrogen sulfide.

9. The method according to claim 1, characterized in that, the electrodialysis device of step (4) is of splint type or roll type, the used membrane is a homogeneous ion exchange membrane or a bipolar membrane that is resistant to contamination and corrosion, the power supply adopts reversal mode or frequent reversal mode, and the pre-concentration allows sulfuric acid to be concentrated to a mass fraction of 10% to 20%.

10. The method according to claim 1, characterized in that, the evaporative concentration device of step (5) adopts second-effect or triple-effect evaporation or membrane distillation, and the acid is concentrated from a sulfuric acid mass fraction of 10%-20% to 30%-60%, the evaporation chamber of the second-effect or triple-effect evaporation and the heat exchanger adopts one or more of graphite, PP, PVDF and PTFE, the operating temperature for the membrane distillation is 60 to 90 C., the vacuum is achieved by a water-circulating vacuum pump or a plunger vacuum pump, the degree of vacuum during operation is 0.05 to 0.09 MPa, the membrane module is operated by using submerged reduced-pressure membrane distillation or multi-effect membrane distillation; and in the membrane distillation, the filter pore size is 0.2 to 0.5 m and the flux is 3 to 5 L/m2.

11. The method according to claim 1, characterized in that, in step (6), fluorine- and chlorine-containing concentrated acid solution obtained after evaporation is subjected to fluorine and chlorine removal by air-stripping desorption method to give fluorine- and chlorine-containing mixed acid, the temperature for hot air-stripping is 110 to 120 C., and the time for air-stripping is 1 to 2 h.

12. An apparatus matched with the method for the recovery and deep treatment of polluted acid according to claim 1, wherein the apparatus is formed by a precision filter (1), a special adsorbing tank (2), a copper-arsenic separation device (3), a vulcanization device (4), an electrodialysis device (5), an evaporative concentration device (6) and an air-stripping device (7) connected in sequence.

13. A method for the recovery and deep treatment of polluted acid, characterized in that, comprising the steps of: (1) pretreatment and selective adsorption: polluted acid wastewater is first filtered through a precision filter to remove suspended matters, and then enters a special adsorbing tank to selectively adsorb rare and noble metals, including rhenium and selenium; (2) copper is separated from arsenic by using arsenic sulfide residue; and (3) after the separation of copper and arsenic, the filtrate is subjected to arsenic deep removal by using a vulcanizing agent, and the resulting arsenic sulfide residue is reused in step (2).

14. The method according to claim 13, characterized in that, in the step (2), the arsenic sulfide residue used for the first separation of copper and arsenic comes from the arsenic sulfide residue obtained by adding sulfide for arsenic removal to polluted acid wastewater or electrolytic waste liquid from smelting enterprises.

15. The method according to claim 13, characterized in that, during the separation of copper and arsenic in the step (2), the sulfide residue is added to the polluted acid wastewater which is treated with adsorbing tank at an As/Cu molar ratio of 1 to 5:1.

16. The method according to claim 13 or H, characterized in that, the polluted acid wastewater in step (1) is the acidic wastewater generated from the scrubbing of flue gas, which is produced in the non-ferrous metal smelting, during the acid-production and purification process, has a mass concentration of sulfuric acid between 2% and 8%, and contains one or more of copper, lead, zinc, cadmium, arsenic, nickel, cobalt, manganese, tin, antimony, selenium, mercury, indium, and rhenium ions, as well as fluorine, chlorine, sulfate radical and hydrogen ions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 shows a process flow chart of the present invention.

[0033] FIG. 2 shows an apparatus chart of the present invention.

[0034] 1 represents a precision filter, 2 represents a special adsorbing tank, 3 represents a copper-arsenic separation device, 4 represents a vulcanization device, 5 represents an electrodialysis device, 6 represents an evaporative concentration device, and 7 represents a air-stripping device.

[0035] In the present invention, polluted acid wastewater is filtered through a precision filter precision filter 1 to remove suspended matters, and then enters a special adsorbing tank 2 to selectively adsorb rare and noble metals including rhenium and selenium; arsenic sulfide or arsenic sulfide residue is utilized to separate copper and arsenic in the copper-arsenic separation device 3; after the separation of copper and arsenic, the filtrate is subjected to arsenic deep removal by using a vulcanizing agent in the vulcanization device 4, and the resulting arsenic sulfide residue is reused for the separation of copper and arsenic; after the separation of arsenic residue, the filtrate enters the electrodialysis device 5 to pre-concentrate the acid and separate and enrich the fluorine and chlorine; the concentrate from the electrodialysis device enters the evaporative concentration device 6 to continue acid concentration, and the condensation water is recycled; the concentrated acid is subjected to fluorine and chlorine removal with a air-stripping device 7, then reused in the process or sulfuric acid production system, and high fluorine and chlorine mixed acid is sold or further recycled.

BEST MODES FOR CARRYING OUT THE EMBODIMENTS

[0036] The following examples are intended to further illustrate the invention without limiting it.

[0037] Arsenic sulphide residue was obtained for the first time: sulfide was put into the polluted acid to precipitate the most of the copper and arsenic, resulting in a mixed residue of copper sulfide and arsenic sulfide. This residue was added to the untreated polluted acid in proportion, the copper in the polluted acid was displaced by arsenic sulfide in the mixed residue to produce copper sulphide residue, through which way a higher-grade copper residue and an arsenic-edriched solution were obtained. The sulfide was used to precipitate the arsenic-edriched solution to obtain the arsenic sulfide residue, and the arsenic sulfide residue can be used in the displacement and separation process of copper in step 2 of the process of the present invention.

[0038] Polluted acid of a smelting enterprise was subjected to water homogenization, and filtered through a precision filter (the filter material is an organic porous material PP with a pore size of 10 m, and the form of the filter is a bag filter) to remove particulate and colloidal impurities, and then allowed to enter a special adsorbing tank. The arsenic sulfide residue was added to the water discharged from the adsorbing tank at an As/Cu ratio of 2:1, and reacted at 80 C. for 1.5 h for the separation of copper and arsenic, and the copper-enriched residue (copper sulfide residue) and the arsenic-enriched solution were obtained after filtration. Hydrogen sulfide was added into arsenic-enriched solution in an amount of 1.1 times the theoretical amount, and reacted for 30 minutes in the gas-liquid enhanced vulcanization device. The product of the reaction was subjected to solid-liquid separation to obtain arsenic sulfide residue, which was reused partly for the separation of copper and arsenic. The obtained solution entered the electrodialysis device to concentrate acid and separately concentrate fluorine and chlorine at the current density of 40 mA/cm.sup.2, generating a high acidity solution containing high concentrations of fluorine, chlorine and a wastewater containing low concentrations of chlorine, fluorine and acid (diluted solution with a low concentration of heavy metals). The high fluorine, chlorine solution was further concentrated by triple-effect evaporation to an acid concentration of 50%, and the condensation water with low concentrations of fluorine and chlorine obtained at the same time can be reused. The concentrated acid was subjected to hot air-stripping to remove fluorine and chlorine at 120 C. for 2 h. After removal of fluorine and chlorine, sulfuric acid could be reused in the smelting system. The gas with high fluorine and chlorine was condensed and absorbed to get a highfluorine and chlorine mixed acid. Hydrofluoric acid and hydrochloric acid separated as by-products can be reused or for sale.

[0039] After treatment by selective adsorption, the recovery rate of rhenium in the polluted acid wastewater could reach above 95% with arsenic adsorption less than 1%, which could realize efficient separation of rhenium and arsenic. Through the reuse of the arsenic sulfide residue, the recovery of copper in the separation process of copper and arsenic was more than 99%, the grade of copper in the resulting copper sulfide residue was 58%, and the content of arsenic was 3.2%. The arsenic removal rate of the arsenic-enriched solution through vulcanization was 99.9%, the content of arsenic in the solution was 0.3 mg/L, and the grade of arsenic in the arsenic residue was 55%. After pre-concentration and separation by electrodialysis, the acid was concentrated from 3% to 12%, and meanwhile the separation rates of fluorine and chlorine were 85% and 90%, respectively; the mass concentration of acid increased from 12% to 50% by triple-effect evaporation; after the removal of fluorine and chlorine, the acidity could reach 70%, the contents of fluorine and chlorine in the acid were 150 mg/L and 120 mg/L, respectively, and the concentration of fluorine and chlorine in the resulting fluorine- and chlorine-containing mixed acid solution could reach above 30 g/L. After the removal of fluorine and chlorine, sulfuric acid could be returned to the process of electrolysis, acid production, etc. The method maximizes the use of resources and achieves the goal of recycling polluted acid wastewater.