REMOVAL OF MULTIPLE-METALS FROM CONTAMINATED CLAY MINERALS

摘要

Clay minerals spiked with multi-component metal ions (Cu~(+2), Cd~(+2), Pb~(+2)) were decontaminated using different soil washing solutions. The desorption characteristics were determined by batch acid leaching with various acids. Removal of Cu~(+2), Cd~(+2)and Pb~(+2) ions from variable charge minerals (e.g. kaolinite) required much less effort than their removal from constant-charge minerals (e.g. illite). The surface charge of a clay mineral had an important influence. When the numbers of H~+ and Na~+ ions available in the soil were increased by adding a buffer solution such as NaOAc-HOAc, heavy metals adsorbed on the clay surface transferred to the pore fluid. When more H~+ or Na~+ ions were available in the pore fluid, more Cu~(+2), Cd~(+2) and Pb~(+2) ions were released into the equilibrium solution. Decreasing the pH led to more removal of heavy metal ions from kaolinite. The presence of Na~+ ions facilitated the removal of heavy metals from contaminated illite. The selectivity for desorption was in the order Cu~(+2) > Cd~(+2) > Pb~(+2) for all washing solutions investigated.