Investigation of different extraction procedures for the determination of major and trace elements in coal by ICP-AES and ion chromatography

This paper presents the extraction of major and trace elements from a coal sample, in deionized water, by using three different extraction techniques. Rotary mixing and ultrasonic extraction were examined for different extraction times, while the microwave assisted extraction was performed at different temperatures. Metal concentrations (Na, K, Ca, Mg, Al, Fe, Mn, Be, Cd, Co, Cr, Hg, As, Ni, Se, Sb and Pb) in a solution were determined by employing the inductively coupled plasma atomic emission spectrometry; whereas the results obtained for Na, K, Ca and Mg were compared employing ion chromatography. Comparing the rotary and ultrasonic-assisted extraction it is shown that the former is more efficient for the determination of Fe, Na and Pb, whereas the latter one has proven more efficient for the determination of Co and Cr ions. Microwave-assisted extraction has proven the most efficient method for any elements tested in coal. In addition, sequential extraction of elements was done using microwave digestion. The results of sequential extraction experiments indicated associations of investigated elements with a mineral phase and organic matrix. Sequential extraction provided information on possible leaching of As, Cd, Co, Cr, Ni, Pb, Fe and Mn in environmental conditions.