Sludge from a printed circuit board factory containing high concentrations of Cu and Pb was characterized. Aqueous ammonia solutions were used to extract metals from the sludge. The extraction reactions were completed within 6 hrs. The best extraction efficiency was found at pH of 10.0. Higher solid-liquid ratio and higher ammonia concentration resulted in better extraction efficiency. Fractionation experiments showed that Cu and Pb were mainly extracted from the Fe-Mn oxide-bound and carbonate-bound fractions. Extracted sludge could meet the TCLP regulation limit and be categorized as a non-hazardous waste. Results show that ammonia extraction is of potential in resource recovery and in detoxification of hazardous waste.
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Liu et al. (2003) studied this question.
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