Abstract
Non-ferrous metal smelting enterprises produce hundreds of thousands of tons of arsenic sulfide sludge (ASS) each year in China. Most of the ASS are stored at the companies without enough preventive measures. During the storage and natural drying process, arsenic sulfide is easily oxidized, thereby causing secondary pollution and increasing environmental risks. In this paper, experiments of simulated storage were used to study the release characteristics of heavy metals. During the simulated storage, the release concentrations of As, Pb, and Cd increased rapidly at first and then slowly. Although the total amount of arsenic released was the largest, the release ratio was in the order of Cd > Pb > As. The effects of different atmospheres and conditions on the release of arsenic and heavy metals were explored. The more the H2SO4 in the sludge, the higher the release concentration, and the addition of an appropriate amount of Ca(OH)2 is beneficial for reducing the release of heavy metals. Finally, SEM, XRD and TG-DTG techniques were carried out to confirm that the release of heavy metals was caused by the oxidation process resulting from the residual H2SO4 in the ASS and the air.
Highlights
The toxicity and carcinogenicity of arsenic and heavy metals have caused serious environmental concerns throughout the world [1,2]
The results showed release concentrations of release during the simulated storage of
The results showed that the release concentrations of
Summary
The toxicity and carcinogenicity of arsenic and heavy metals have caused serious environmental concerns throughout the world [1,2]. It is universally believed that the extractive process of non-ferrous metal is one of the most important sources of arsenic and produces a large amount of strongly acidic wastewater with high arsenic concentration [6,7,8]. Waste electrolyte with a high concentration of arsenic is produced abundantly in copper and lead-zinc electrolyte processes [9,10]. Neutralization by Ca(OH)2 /CaO and co-precipitation with ferric salt are the most useful industrial methods for the treatment of strongly acidic wastewater bearing arsenic and heavy metals. Large amounts of hazardous wastes are generated by these methods, which may cause environmental risks
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