Investigation of the Chemical and Physical Mechanisms of Electroplating Sludge Aging

摘要

A study has been conducted to measure the change in concentration of extractable metal ions in sludges precipitated from the wastewaters discharged from electroplating operations as the sludges undergo syneresis or aging. From earlier observations, it was considered possible that aging electroplating sludges would yield a decrease in the leachability of toxic heavy metal ions thus permitting a possible delisting of a hazardous waste to a nonhazardous waste with an attendant reduction in disposal costs. Five metal ions typically found in electroplating sludges were precipitated with hydroxide ions individually, in combination, and in simulated and actual wastewaters. This was accomplished to study the changes in concentration of metal ions that could be leached at different pH's from the gelatinous precipitates initially formed and aging after six weeks of aging under various conditions. Two leaching methods were used and the metal ion concentrations were determined by atomic absorption.