Acid extraction of coal for the determination of major ash forming elements

Abstract

A method is described for the analysis of whole coal for the major ash forming elements. Coal is weighed into polypropylene bottles, hydrofluoric and nitric acids are added and the coal-acid mixture is heated and sonicated in an ultrasonic bath. After the addition of boric acid, used to complex the fluoride, the concentrations of the elements, Al, Ca, Fe, K, Mg, Mn, Na, P, Si and Ti, are determined using inductively coupled plasma atomic emission spectrometry. The method is applicable to coal ash, in which S can also be determined. Analyses of the standard reference coals, South African Reference Material 18 (Witbank Coal), 19 (OFS Coal) and 20 (Sasolburg Coal) and ashes, Australian Standard Certified Reference Material 010 and National Institute of Standards and Technology Standard Reference Material 1633a are reported. The results confirm the accuracy of the method, which is a rapid alternative to commonly used procedures.