Column leaching of coal and its combustion residues, Shizuishan, China

Column leaching experiments were performed on the samples of feed coal, fly ash, and bottom ashes from the Shizuishan coal-fired power plant, China, in order to investigate the leaching behaviour and potential environmental impact of the 11 potentially hazardous elements: As, Cd, Co, Cr, Hg, Mo, Ni, Pb, Se, Th, and U. The results show that most of the elements are more easily leachable from the feed coal in comparison with the combustion residues, and basically show a similar leaching behavior from the fly and bottom ashes. The modes of occurrence of elements, time, and pH play an important role in controlling the leaching behavior of the elements from the solid samples. There is a certain relationship between the leached concentrations of most of the elements and their contents in the fly and bottom ashes. The maximum leached concentrations of Ni, Co, As, Cd, Mo, and U from the coal or its combustion residues by leaching action of acid rain exceed their limited concentrations recommended in relevant environment quality standard.