Speciation of Selected Minor and Major Elements in Oil Ash I. Operationally Defined Chemical Associations and Aqueous Speciation

This study is focused on the speciation of selected elements in oil ash. Our efforts were directed primarily to obtain information on the various forms of vanadium, chromium and nickel. One sample was characterized via its total composition and via its capacity for releasing various elements. The latter was estimated by hot water and nitric acid extractios. A rapid cold water extraction technique has been developed and utilized for sample preparation prior to aqueous speciation by high pressure ion chromatography (HPIC). Results of the HPIC measurements, in agreement with electron spin resonance (ESR) investigations performed on the solid sample, indicate that 38% of the vanadium is present as VOSO₄, 58% of the chromium is Cr₂(SO₄)₃ and 30% of the nickel is NiSO₄. The pH and the redox potential values of the cold water extract support the existence of these forms. Results of a generic study with successive fractionation extractions show the probable existence of oxides, associations with organic matter and aluminosilicate minerals.