Process for treating high-arsenic and high cadmium waste acid by using three-stage lime-ferric salt method

Abstract

The invention relates to the technical field of processes for treating acidic arsenic-contained wastewater discharged by non-ferrous smelting and sulfuric acid industries and particularly discloses a process for treating high-arsenic and high cadmium waste acid by using a three-stage lime-ferric salt method. The process comprises the following three stages: firstly, gypsum manufacture: adding lime to adjust the pH value to 2, and carrying out solid-liquid separation to obtain gypsum slag, wherein the gypsum slag can be used for manufacturing cement; secondly, neutralization, oxidation and arsenic sedimentation: adding lime into a supernatant liquid, adjusting the pH value to 5-6, adding ferrous sulfate according to the ferrum-to-arsenic ratio of 4:1, continuously aerating, adding anionic polyacrylamide for coagulation, and removing most of arsenic; and thirdly, neutralization and coagulation: adding lime to adjust the pH value to 9, adding ferrous sulfate according to the ferrum-to-arsenic ratio of 4:1, continuously aerating, adding anionic polyacrylamide for coagulation, and removing residual arsenic and heavy metal ions. After wastewater with the highest arsenic concentration of 14740mg / L and the highest cadmium concentration of 130mg / L is treated by using the process, the concentration of arsenic in the wastewater is reduced to 0.25g / L, no cadmium is found, and therefore, the wastewater achieves the national discharge standard.

Description

technical field [0001] The present invention relates to the technical field of treatment process for wastewater discharged from the non-ferrous smelting industry, in particular to a process for treating polluted acid containing high arsenic and high cadmium by a three-stage lime iron salt method, which is suitable for high arsenic, high cadmium and various heavy metals Treatment of ionic high-acid wastewater. Background technique [0002] A large amount of high-concentration acidic wastewater containing heavy metals such as arsenic and cadmium is produced in the process of non-ferrous metal smelting and mineral processing, which is called dirty acid in the industry. Polluted acid has the characteristics of complex composition, strong toxicity, and great difficulty in treatment. If the wastewater is not treated up to standard, it will cause serious environmental pollution and destroy the ecological environment (Mandal, B.K. and Suzuki, K.T., 2002.Arsenic round the world: a r...

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Problems solved by technology

However, the content of cadmium in the treatment object of the present invention is relatively high (130mg / L), and there is no literature reporting the simultaneous removal of high content of cadmium and arsenic

[0007] Some laboratory studies involve the use of continuous segmented iron salts to remove arsenic (Jia, Y, Zhang, D., Pan, R., Xu, L. and Demopoulos, GP., 2012. A novel two-step coprecipitation process using Fe(III) and Al(III) for the removal and immobilization of arsenate from acidic aqueous solution. Water Research 46(2), 500-508.), but the experimental design has not reached the level of industrial application, especially the use of three stages Lime-iron-salt treatment of high-concentration arsenic-containing wastewater has not been reported in the literature

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