Host: Japan Society of Material Cycles and Waste Management
In Japan, a common method of treating waste incineration fly ash prior to disposal is using chelating agents (chelate), chemical organic compounds that can immobilize the heavy metals in the fly ash and prevent their leaching into the environment. The objective of this study is to deepen the understanding of how mercury in waste incineration fly ash is immobilized by chelate-complexation. Three factors have been studied thus far, namely, chelate/mercury ratio, chelate storage time and the effect of co-existing ions. Standard mercury chloride (HgCl2) and chelate solution were mixed at an initial Hg concentration of 100 μg/L with chelate-Hg ratios ranging from 0.01 to 10. The solutions were then tested for free Hg using a mercury analyzer using tin(II) chloride as a reducer to convert any free Hg, which is not bound by the chelate, into gaseous elemental Hg. For the co-existing ionic effect study, ion-Hg ratio method was similarly adopted. Investigations have found that high chelate concentrations exceeding a ratio of 3 promoted the increase in free Hg. Moreover, co-existing ions such as Ca2+ and Mg2+ were found to have reduced chelate-mercury complexation. Chelate storage time, however, does not affect complexation efficiency.
