Arsenic Fixation in Metallurgical Plant Effluents in the Form of Crystalline Scorodite via a Non-Autoclave Oxidation-Precipitation Process

摘要

This paper presents a non-autoclave oxidation-precipitation process for the fixation of arsenic in metallurgical plant effluents in the form of scorodite, the generally accepted most stable form of arsenic for disposal. There are two major novel steps involved in the process: (i) the oxidation of As(III) to As(V) in acidic sulfate solutions by using SO_2/O_2 gas mixtures and (ii) the precipitation of arsenic as scorodite at ambient pressures. An investigation of the kinetics of the two steps demonstrated that both the arsenic oxidation and scorodite precipitation reactions take place at industrially viable rates in acidic sulfate solutions at elevated temperatures (>90degC). Various types of iron source were tested for the production of scorodite, and the results suggest the potential for using any available iron, including ferrous or ferric salts and industrial iron-containing residues.