Plating Waste Sludge Metal Recovery

摘要

The U.S. Army Toxic and Hazardous Materials Agency has requested that AMAX Extractive Research & Development, Inc. conduct a five-phase program to review literature on the current state-of-the-art in metal recovery from plating wastes, to propose a typical plating sludge composition and aging treatment in lieu of actual U.S. Army plating wastes), to develop a research and design test plan for treating this typical plating sludge, to conduct the test program, and to summarize the results in a final report. The final report proposes a sulfuric acid leach of hydroxide plating sludges, containing copper, cadmium, zinc, nickel, iron, and chromium, to extract greater than 99 percent of the heavy metal values, followed by lime treatment of the resulting filter cake to render it nonhazardous to EP testing. The sulfuric acid leach extract may be treated by selective sulfide precipitation at a controlled pH regime in order to produce a mixed sulfide of copper and cadmium with most of the zinc present in the original extract separate from a leach liquor containing more than 98 percent of the chromium, which does not form a sulfide precipitate, Nickel and iron are not selectively separated under the sulfide precipitation conditions. However, a solvent extraction process using di(2-ethyl-hexyl) phosphoric acid can be used for recovering nickel, iron, and chromium from the resulting filtrate. Originator-supplied keywords: Plating sludge, Acid leach, EP toxicity, Metals, Separation, Extraction, and Recovery.