Inhibition of Lead Elution from Incineration Ash by Phoshate

Abstract

Incineration of solid wastes is the most effective way to reduce their volume. However, the remaining incineration waste, i. e., ash, often contains high concentration of toxic heavy lead metal. Most of the ash from solid wastes is now disposed of under the regulation of disposal standard of lead, however stricter environmental standards should be applied when the ash is effectively utilized. The lead in the ash should be embedded in the matrix in a stable manner. In the present study, the inhibition of lead elution from incineration ash by addition of phosphate is demonstrated. The effect of calcination temperature between 400-1, 000°C on the lead elution from the ash/phosphate mixture was investigated. The higher the calcination temperature, the lower the elution is. The lead ion concentration in the eluent is much lower than the value estimated from the solubility constant of Pb (OH) ₂, and mostly attained environmental standards, which is comparable to or rather smaller than that of PbHPO₄. The present result of inhibition of lead elution at high temperature calcination is explained by the conversion from PbHPO₄ to Pb₃ (PO₄) ₂. The improvement in the calcination condition will make the inhibition more effective.