Nickel speciation of fly ash by phase extraction

Chemical speciation of nickel is necessary for risk assessment of fossil fuel fly ash. We have used a standard coal fly ash in sequential extraction to show reproducibility and mass balance of nickel phase fractionation, and applied it to two field samples of oil fly ash. Nine distinct nickel phases were quantitated by voltammetry and characterized by cumulative extraction plots and dissolution kinetics. They are further correlated with SEM/EDX analysis of the fly ash. This nickel speciation method reflects the difference in the combustion process in generating the two oil fly ash and allows comparison of their nickel distribution and bioavailablity.