Determination of As, Sb and Se Speciation in Fly-Ash Leachates

Abstract

Abstract Several studies have been carried out to determine the speciation of As and Se in fly ashes in order to understand the leaching behaviour of these elements and have reported widely varying results. Many of these studies make use of pH-selective hydride generation with sodium tetrahydroborate to determine the speciation of As. We found that these methods gave unreliable results for the speciation in fly-ash leachates. In this study the valency states of As, Sb and Se are determined by speciation methods which were specifically tested for fly-ash leachates. Coprecipitation with dibenzyldithiocarbamate appeared to be a good method to determine As(III) and Sb(III) in fly-ash leachates. It was possible to obtain the total leached amount of As and Sb by a one-step hydride generation method. Precipitation of Se(IV) on activated carbon appeared to be the most adequate of the methods tested in this study for Se. Only minor amounts of the more toxic and mobile oxyanions of As(III), Sb(III) and Se(VI) were leached from the five fly ashes investigated in this study.