Effect of Flue Gas Treatment on the Solubility and Fractionation of Different Metals in Fly Ash of Powder River Basin Coal

摘要

Studies were conducted to examine the effect of flue gas carbon dioxide (CO_2) on solubility and availability of different metals in fly ash of Powder River Basin (PRB) coal, Wyoming, USA. Initial fly ash (control) was alkaline and contains large amounts of water-soluble and exchangeable metals. Reaction of flue gas CO_2 with alkaline fly ash resulted in the formation of carbonates which minimized the solubility of metals. Results for metal fractionation studies also supported this fact. The present study also suggested that most of the water-soluble and exchangeable metals present in the control (untreated) fly ash samples decreased in the flue gas-treated samples. This may be due to the transfer of the above two forms to more resistant forms like carbonate bound (CBD), oxide bound (OXD), and residual (RS). Geochemical modeling (Visual MINTEQ) of water solubility data suggested that the saturation index (SI) values of dolomite (CaMg(CO_3)_2) and calcite (CaCO_) were oversa-turated, which has potential to mineralize atmospheric CO_2 and thereby reduce leaching of toxic metals from fly ash. Results from this study also showed that the reaction of flue gas CO_2 with alkaline fly ash not only control the solubility of toxic metals but also form carbonate minerals which have the potential to fix CO_2.