| Summary: | 碩士 === 大同大學 === 化學工程研究所 === 91 === The wastewater treatment processes in metal and electronics industries have generated a lot of sludge that contains various heavy metals and has been classified as hazardous industrial waste. Although there exist many strict environmental laws to regulate the disposal of the hazardous industrial waste, effective treatment methods for heavy metal-containing sludge are not available in Taiwan. In order to remove heavy metals from the sludge to make it nonhazardous, this study uses nitric acid and citric acid to extract copper, zinc, cadmium, and chromium from the wastewater treatment sludge generated by an electroplating process. Factors influencing the heavy metal extraction rates, including the agitation speed, acid concentration, solution temperature, and sludge particle size, were studied individually. The shrinking-core model is applied to analyze the extraction kinetic data. The experimental results showed that metal ion diffusion through the ash layer was the rate rate-controlling step and the extraction rate increased with increasing acid concentration and solution temperature, but decreased with increasing particle size.
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