Efficiency of leaching tests in the context of the influence of the fly ash on the environment

The leachability of heavy metals (Cu, Pb and Zn) from the coal fly ash samples was studied. The investigations executed using three leachability tests (USEPA, TCLP, ASTM). The effect of different parameters was determined (the diameter of ash grains, the kind of leaching solutions, pH of leaching solutions, the volume ratio of leaching solutions to the mass of ash samples, and the leaching time) on the leachability of the heavy metals from fly ash samples. Moreover, the influence of pH and changes in the redox potential of the leaching solutions as well as the presence of organic compounds that could potentially form complexes with metals and solubility changes of metals. The concentration of the metals studied (Cu, Pb and Zn) in all obtained solutions was determined by FAAS method. On the basis of the research investigations, optimal leachability conditions for Cu, Pb and Zn from fly ash in this study have been determined. We have also found that pH of the leaching solution, and the presence of organic compounds which have a potential capacity of complexion the metals are the important factors in determining the solubility of Cu, Pb and Zn.