Copper aluminate spinel in the stabilization and detoxification of simulated copper-laden sludge

摘要

This study aims to evaluate the feasibility of stabilizing copper-laden sludge by the application of alumina-based ceramic products. The processing temperature, material leaching behaviour, and the effect of detoxification were investigated in detail. CuO was used to simulate the copper-laden sludge and X-ray Diffraction was performed to monitor the incorporation of copper into the copper aluminate spinel (CuAl_2O_4) phase in ceramic products. It was found that the development of CuAl_2O_4 increased with elevating temperatures up to and including 1000℃ in the 3 h short-sintering scheme. When the sintering temperature went above 1000℃, the CuAl_2O_4 phase began to decompose due to the high temperature transformation to CuAlO_2. The leachability and leaching behaviour of CuO and CuAl_2O_4 were compared by usage of a prolonged leaching test modified from US EPA's toxicity characteristic leaching procedure. The leaching results show that CuAl_2O_4 is superior to CuO for the purpose of copper immobilization over longer leaching periods. Furthermore, the detoxification effect of CuAl_2O_4 was tested through bacterial adhesion with Escherichia coli K12, and the comparison of bacterial adhesion on CuO and CuAl_2O_4 surfaces shows the beneficial detoxification effect in connection with the formation of the CuAl_2O_4 spinel. This study demonstrates the feasibility of transforming copper-laden sludge into the spinel phase by using readily available and inexpensive ceramic materials, and achieving a successful reduction of metal mobility and toxicity.