Measurements of the leachability of potentially hazardous trace elements from solid coal gasification wastes in China

Solid wastes from commercial coal gasification plants are a significant environmental issue in China because of the large quantities produced. In recent years, with the rapid development of coal gasification technologies in China, more and more coal gasification residues are being disposed of in landfills because of the low utilization of the residues. In the present study, the column leaching procedure M1314 developed by the U.S. Environmental Protection Agency was used to evaluate the potential for environmental pollution by potentially hazardous trace elements (Be, V, Mn, Cr, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, Sb, Cs, Ba, Tl, Pb, Hg, Th, and U) in the coarse and fine gasification residues from two plants using General Electric (GE) and Gaskombinat Schwarze Pumpe (GSP) coal gasification technologies in northwest China. The potentially hazardous trace elements in the residues show different release patterns with the liquid-solid ratio increasing. The cumulative leached concentrations of the potentially hazardous trace elements from the coal gasification residues were generally low, and only Mo in the leachate of GSP fine residue was moderately soluble. V in the GSP coal gasification residues showed an increasing leachability in the leaching procedure. As, Se, Mo, Sb, and Tl in some leachates exceeded their thresholds in Level III of the Chinese Quality Standard for Groundwater and/or the Maximum Contaminant Levels of the U.S. National Primary Drinking Water Regulations. According to the risk assessment code, Se in the GE fine residue and Mo in the GE and GSP fine residues had medium risk to the ecosystem. Those data indicated that the potential for environmental pollution by those elements from coal gasification plants should be given consideration.