Leachability and analytical speciation of antimony in coal fly ash

The present study assesses the single extraction of Sb from two coal fly ashes with aqueous solutions at a range of pHs (1–12) and with citrate 1 mol L−1 at pH 5, in order to obtain preliminary information about Sb leaching from this matrix. Speciation analysis of the coal fly ash extracts by HPLC-ICP-MS and HPLC-HG-AFS was carried out in order to identify the presence of individual Sb species. Sb(V) was the main Sb species in the leachates, although minor amounts of Sb(III) were also detected in some extracts. Citrate at pH 5 gave the best extraction efficiency for both samples whereas Sb species were also fairly soluble in aqueous solutions at acidic pHs. Analysis by HPLC-ICP-MS provided the most accurate results in some extracts (aqueous solution at pH 1 and citrate at pH 5) when both coupled techniques used were compared. The presence in these leachates of higher content of interfering metal ions (Ca, Fe and Pb) than those obtained for the Sb species reduced stibine generation in the HPLC-HG-AFS analysis. The proposed methodology can be considered reliable and useful for antimony speciation in environmental studies.