Using Al/Fe Rich Sludge Residues from Water and Wastewater Treatment Processes to Immobilize Copper Electroplating Waste

Abstract

Hong Kong considers developing an integrated waste management facility with incineration as the core treatment technology to resolve the key issue of insufficient landfill space. Currently, the operation is starting with the incineration of sewage sludge. The elemental analysis of collected samples showed that both iron and aluminumare major elements contained in sewage sludge and aluminum is the predominant constituent in waterworks sludge. This study proposed a waste-to-resource strategy by using the waterworks and sewage sludge incineration residues (ash) as the ceramic raw materials to stabilize copper electroplating waste. When sintering the mixture of waterworks sludge ash and copper electroplating waste, the CuAl2O4 spinel phase was detected at 650 oC, and became the predominant product phase at temperature higher than 850 oC. Strong signals of the CuAl2O4 phase continued until the temperature reached 1150 oC, and further sintering initiated the generation of other copper-containing phases (CuAlO2, Cu2O and CuO). After sintering the mixture of sewage sludge ash and copper electroplating waste, hematite (-Fe2O3) became an effective component to incorporate copper into the CuFe2O4 spinel with cubic structure. The leaching performances of CuO, CuAl2O4 and CuFe2O4 were compared by a 22-d prolonged acid leaching test with leaching fluid at pH around 2.9. The leachability analysis pointed out the superiority of copper aluminate and ferrite in stabilizing copper, suggesting a promising technique for using waterworks and sewage sludge ash to immobilize copper waste.