XAFS Studies of Nickel And Sulfur Speciation in Residual Oil Fly-Ash Particulate Matters (ROFA PM)
XAFS spectroscopy has been employed to evaluate the effect of fuel compositions and combustion conditions on the amount, form, and distribution of sulfur and nickel in size-fractionated ROFA PM. Analysis of S K-edge XANES establish that sulfate is abundant in all PM. However, depending upon the combustion conditions, lesser amounts of thiophenic sulfur, metal sulfide, and elemental sulfur may also be observed. Least-squares fitting of Ni K-edge XANES reveals that most of the nickel in PM is present as bioavailable NiSO{sub 4}.nH{sub 2}O. The insoluble Ni mainly exists as a minor species, as nickel ferrite in PM{sub 2.5} (PM <more »