含砷钴镍渣中砷碱介质氧化浸出机理

Oxidative Leaching Mechanism of Arsenic from Arsenic-containing Cobalt and Nickel Slag in Alkaline Medium

研究了某厂ZnSO4溶液砷盐净化工艺产生的含砷钴镍渣中砷在惰性和氧气气氛的碱介质中的氧化浸出机理.结果表明,砷氧化浸出与温度、介质碱浓度、浸出气氛均密切相关.在惰性气氛、碱介质中,渣中CuO和Cu2O均可作为砷氧化浸出的氧化剂,在80℃及以下低温下,CuO对低价砷起主要氧化作用,还原产物为Cu2O,砷最高浸出率不超过53%;在100℃及以上较高温下,CuO和Cu2O均参与低价砷的氧化浸出过程,还原产物均为单质Cu,最高浸出率约为90%;在氧气气氛、碱介质中,砷浸出率可达98%以上,除O2作为氧化剂直接氧化浸出砷外,渣中的铜可作为O2与低价砷之间电子传递的载体,强化氧化反应.

The oxidative leaching mechanism of arsenic in alkaline medium from arsenic-containing cobalt and nickel slag from the purification unit of zinc sulfate solution was studied. The results indicated that the arsenic leaching was closely related to temperature, alkaline concentration and reaction atmosphere. When the leaching was under inert atmosphere, both CuO and Cu2O existing in the original slag could act as the oxidants for arsenic leaching. At the leaching temperature of 80 ℃ or below, CuO played the main role in the oxidative leaching of arsenic, the highest leaching rate of As was not over 53%, and the reduction product was Cu2O. While at the temperature of 100℃ or above, both CuO and Cu2O could act as the oxidants for the arsenic leaching, the highest leaching rate of As was up to 90%, and the reduction product was Cu. When the leaching was under oxygen atmosphere, the leaching rate was over 98%. Except that the oxygen itself could act as the oxidant to oxidize arsenic directly, the copper in the slag could be the electron carrier between O2 and arsenic in a low valence state, which intensified the oxidation reaction.