A Copper Removal Process for Printed Circuit Board Wastewater Sludge Applying Extraction and Cementation with Chelating Agents Recovery

Removal of copper from printed circuit board (PCBD) industry wastewater sludge by chelant extraction and subsequent cementation by powdered irons were studied. Aqueous chelant solutions of 0.1 M ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) were used to treat sludge from three PCBD factories. Copper that was extracted from these sludge sources by the chelating agents ranged in concentration from 0.72 to 0.81 mol Cu mol⁻¹ EDTA, to 0.57 to 0.80 mol Cu mol⁻¹ DTPA. Competition from other major metal cations in the sludge sources for active sites on chelating agents may contribute to observed differences in copper extraction efficiencies. After extraction with chelating agents, powdered irons were used to replace the chelated copper in the chelant extract, allowing for copper recovery. The recovery efficiencies of copper by the cementation process using powdered iron were 92–99%. After cementation, the extract containing EDTA or DTPA was reused to chelate supplementary fresh copper-containing sludge once again. Recovery ratios of copper from the supplementary sludge were 23.7–100.0%, in comparison with that obtained in previous extraction. Similar copper removal efficiencies observed in the use of both pristine and reused chelant extracts indicate that EDTA and DTPA have enduring chelating capability, and suggest the recycling of chelating agents to reduce overall process usage. This work demonstrated the feasibility of copper removal and recovery from some PCBD wastewater sludge (Sludge B) by chelant extraction and subsequent cementation.