Determination of arsenic(III) and arsenic(V) in ferric chloride-hydrochloric acid leaching media by ion chromatography

Abstract

An analytical method has been developed to determine arsenic(V) in ferric chloride-hydrochloric acid leaching media using ion chromatography with conductivity detection. Oxidation of As(III) by aqua regia allows arsenic(III) to be determined by difference. The method involves a preseparation of trace quantities of arsenic from the relatively large concentrations of ferric chloride and hydrochloric acid prior to the ion chromatography measurement. Iron(III) is separated by passing through a hydrogen-form cation exchange column, and arsenic(III) and arsenic(V) are then eluted with water. The effect of the concentration of acid in this separation is discussed. The effluent collected from the cation exchange column is evaporated to remove the hydrochloric acid. The accuracy and precision of the method were determined from the analysis of various synthetic solutions and are discussed; an accuracy of +/-4% was obtained even at arsenic(V) concentrations as low as 10 ppm. The extent of oxidation of arsenic(III) in acidic ferric chloride solution and the reduction of arsenic(V) in acidic ferrous chloride solution were measured. The results obtained by ion chromatography are compared to the values realized using colorimetry after the preseparation step. 13 references, 3 figures, 4 tables.