Non-ferrous metal smelting high-arsenic contaminated acid arsenic fixing process

Abstract

The invention relates to a non-ferrous metal smelting high-arsenic contaminated acid arsenic fixing process which sequentially includes the steps: pre-neutralization, to be specific, mixing iron-containing slag or iron-containing reagents and smelting contaminated acid, controlling Fe / As molar mole ratio, throwing mixed slurry and the contaminated acid into a pre-neutralization tank, performing reaction, controlling the pH (potential of hydrogen) value of solution, thickening pre-neutralization slag slurry to obtain bottom flow, supernate and gypsum slag, and using the gypsum slag as a cementretarder for sales; oxidation, to be specific, supplementing iron sulfate serving as an iron source reagent as required, heating the pre-neutralized supernate, adding hydrogen peroxide serving as an oxidizing agent for oxidation, controlling oxidation-reduction potential, and completely oxidizing trivalent arsenic into pentavalent arsenic; crystal form iron arsenate precipitation arsenic fixing, to be specific, controlling reaction temperature, adding seed crystals, controlling reaction endpoint pH values by adding lime milk, and conveying bottom flow subjected to two-stage arsenic precipitating reaction to a landfill through filter-pressed crystal form iron arsenate solids. The arsenic fixing process has the advantages of simple process, low cost, good treatment effects, low environmentalpollution risk and the like and is applicable to non-ferrous metal metallurgy industries.

Description

technical field [0001] The invention relates to an arsenic-fixing process for nonferrous metal smelting high-arsenic polluted acid, which is suitable for application in the nonferrous metal metallurgy industry. Background technique [0002] Non-ferrous metals are important resources needed for industrial development. my country is rich in mineral deposits. Due to the high content of arsenic in non-ferrous metal ores, it is inevitable to produce A large amount of acidic wastewater, the acidic wastewater industry is called dirty acid. The polluted acid system is complex, with many components and high concentration. It mainly contains high concentrations of arsenic, sulfate ions, fluoride ions, and chloride ions, as well as copper, zinc, lead, cadmium and other metals. With the continuous development of non-ferrous smelting technology, many problems about the treatment of dirty acid and the reduction, stabilization and harmless treatment of arsenic-containing waste residues nee...

AI Technical Summary

Problems solved by technology

At present, there have been many reports on the synthesis method of scorodite: First, Outotec’s authorized patent CN102307813B discloses “a method for removing arsenic as scorodite”, which uses an oxidant to oxidize iron to trivalent and arsenic to pentavalent. valence, and precipitate iron and arsenic into amorphous ferric arsenate under normal pressure, then send the formed ferric arsenate precipitate to 150-200°C for hydrothermal conversion, and process it into crystalline scorodite. The shortcoming of this method is to first enrich ferric arsenate, and then transform it into crystalline scorodite through high temperature and high pressure. Arsenic treatment method", firstly add calcium oxide to arsenic-containing polluted acid, separate solid-liquid to obtain gypsum, then add iron salt and oxidant to the supernatant after solid-liquid separation, at a lower Fe / As molar ratio of 0.8- Under the conditions of 1.2:1 and a certain pH value of 1.8~4, the arsenic in the dirty acid is first formed into amorphous iron arsenate precipitation, and then the acid is added to dissolve and heated (80~95°C), and the solid and liquid are separated to obtain gypsum and odor. Mixed precipitation of allionite, the supernatant after solid-liquid separation is added with ferric salt and calcium oxide for deep arsenic removal to meet the discharge standard. This method has ferric arsenate and acid back-dissolution. The pH value control and the addition of crystal seeds are not disclosed. problem, and there should be problems of low conversion efficiency and incomplete conversion at a temperature of 80-95°C, plus the two arsenic precipitation processes require two solid-liquid separations, and the supernatant after solid-liquid separation is still Deep arsenic removal treatment is required, the whole process is complicated, and the problem of scorodite conversion efficiency is not mentioned; Outotec authorized announcement number is "CN100558918C" and also discloses "method for recovering valuable metals and arsenic from solution" , first use the dilute sulfuric acid produced in the process of washing the arsenic-containing gas to leach the fly ash or other calcined products formed in the pyrometallurgical treatment of non-ferrous metals to form a solution containing metallic copper and arsenic, and then after liquid-liquid extraction, through vulcanization The metal copper in the solution is recovered by precipitation, and finally the remaining solution is subjected to two-stage arsenic precipitation. In the first stage, an oxidant is used to oxidize arsenic to pentavalent, iron to trivalent, and the Fe / As molar ratio is adjusted to 1-1.1, pH The value is adjusted to 1-2, and the temperature is adjusted to 85-135°C so that scorodite FeAsO suitable for storage 4 2H 2 The form of O precipitates arsenic; the underflow of the first stage is returned, and the overflow is sent to the second stage. In the second stage, divalent or ferric iron is added to adjust the Fe / As molar ratio to be greater than 3, and lime is used to adjust the pH value to 4-7. Adjusted to 40-60°C, the remaining arsenic in the solution was formed as amorphous iron arsenate FeAsO 4 The arsenic concentration in the aqueous solution after the second stage of precipitation is 0.01-0.2mg / L. This method uses limestone or lime to adjust the pH, and adds divalent or ferric iron source to adjust the iron The ratio of arsenic to arsenic, the ferric arsenate precipitation in the second stage is all returned to the first stage to produce scorodite precipitation, which has complex processes, high cost of chemicals, large amount of arsenic-containing scorodite slag produced, and high cost of hazardous waste landfill disposal, etc. insufficient

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