Electrochemical Immobilization of Arsenic

Abstract

Arsenic handling and immobilization are critical issues in the mining of sulfarsenide minerals, due to arsenic’s toxicity to the environment. Significant amount of arsenic can be present in Cu, Zn, Ni, and Co minerals. Cobaltite (CoAsS) for example, is one of those sulfides from which cobalt can be mined as the primary mineral. However, cobalt extraction from cobaltite generates equivalent mass of arsenic per extracted cobalt. To unlock the domestic cobalt production, efficient arsenic immobilization techniques are needed. Compared to traditional hydrometallurgical and pyrometallurgical processes, an electrochemical method is proposed to efficiently immobilize arsenic from cobaltite. An electrochemical cell was assembled to promote the immobilization of arsenic, in the presence of iron, via the precipitation of crystalline scorodite (FeAsO4 · 2H2O). Various electrochemical mechanisms were studied to maximize the oxidation and precipitation rates, such as galvanostatic and potentiostatic techniques. Results using both surrogate solution of arsenic, iron, and cobalt, as well as cobaltite solution show high immobilization rates of arsenic.