Phosphorus Speciation in Coal Bottom Ash

Coal, coal bottom ash (CBA), and coal fly ash contain many elements in different forms which may change during the coal combustion process. A true understanding of the dynamics of phosphorus (P) in the natural environment requires an expanded knowledge of its oxidation-reduction (redox) cycling. This study presents a sequential extraction method for the speciation of phosphorus from CBA in seven forms and their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The total P concentration in CBA was found to be 651.48 mg kg(-1). The most abundant form of P in CBA is the sulfide fraction of P (40.42%). The relative abundances of the remaining P fractions follow the order: Residual 38.63% > Reducible 15.12% > Carbonate 3.42% > Oxidizable 1.10% > Exchangeable 0.94% > Water soluble 0.37%.