Method for treating waste acid by gypsum sedimentation, arsenic oxidizing sedimentation and iron salt neutralization and co-precipitation

Abstract

The invention discloses a method for treating waste acid by gypsum sedimentation, arsenic oxidizing sedimentation and iron salt neutralization and co-precipitation. The method comprises the following steps of: the first section: gypsum sedimentation, namely putting lime cream into the waste acid, and removing most sulfuric acid from the waste acid through neutralization reaction to generate CaSO4sediment and gypsum; the second section: arsenic oxidizing sedimentation, namely performing solid-liquid separation after the gypsum reaction, adding polymeric iron into supernate, adding hydrogen peroxide oxidant into the supernate to oxidize Fe2+ into Fe3+ and oxidize As3+ into As6+ under the condition of low pH, and removing most arsenic from the waste acid through oxidizing sedimentation reaction so as to enrich the arsenic in the waste acid and produce arsenic slag; and the third section: iron salt neutralization and co-precipitation, namely performing solid-liquid separation after the arsenic reaction, adding polymeric iron and heavy metal ion hunting agent into the supernate, and removing residual arsenic and heavy metal ions from the waste acid to generate neutralized slag and water meeting the national discharge standard. The method has the advantages of short flow, simplicity, practicability, good pollution control effect and good gypsum byproduct, and the removal rate of arsenic is up to 99.999 percent.

Description

Technical field [0001] The invention relates to a method for treating high- or low-acid wastewater containing high arsenic or low arsenic and multiple heavy metal ions discharged from industries such as non-ferrous smelting and chemical industries, and a method for gypsum precipitation-arsenic oxidation-neutralization of iron salt co-precipitation acid method. Background technique [0002] In the production process of non-ferrous smelting and chemical industries, a large amount of waste acid will be produced. These waste acids contain harmful elements such as copper, arsenic, lead, zinc, and cadmium. They must be treated to meet national emission standards before they can be discharged. Environmental requirements. For sewage acid wastewater containing arsenic and multiple heavy metal ions, methods such as neutralization precipitation, neutralization of iron salts, and sulfidation are mainly used at home and abroad, and there are relatively successful practices. However, these m...

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Problems solved by technology

However, these methods all have deficiencies in varying degrees: (1) neutralization precipitation method needs to increase the pH value of polluted acid (generally controlled between 10-11, even greater than 12) to achieve the purpose of removing arsenic and heavy metals, and the effluent needs to add Acid reverse adjustment can be discharged, and it is only suitable for low arsenic (As1g / l) polluted acid meet the standard

(2) The neutralization iron salt method has wider adaptability to polluted acid, but there are also problems caused by the high pH value control of the neutralization precipitation method, and the amount of iron salt is large, requiring multi-stage treatment, and the standard is not stable

(3) There is a biggest problem in the above two methods, that is, the amount of slag produced is large, and most of the arsenic in the slag exists in the form of trivalent (arsenite), which has high solubility and high toxicity (the toxicity of trivalent arsenic is 60 times the toxicity of pentavalent arsenic), there is a possibility of secondary pollution, which is not conducive to the final disposal or treatment of waste residue

(4) The vulcanization method is used to treat high-arsenic (arsenic in 1-20g / l) high-acid polluted acid wastewater has its advantages, high arsenic removal rate, small slag production, arsenic slag can be recycled, but its process is long, The equipment is complicated and the processing cost is extremely high, which is unaffordable for ordinary enterprises

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