Cu-based heterostructure photocatalysts derived from Cu sludge and municipal sewage sludge for efficient degradation of 2,4-dichlorophenol

The recycling methods of copper (Cu) from the hazardous waste of Cu sludge including high-temperature melting and extraction often encounter the problems such as the difficulty in getting high-purity Cu, secondary pollution, and the terminal waste treatment. To display the values of Cu sludge more effectively, it is first used as the Cu source to form the Cu0-based (CSS) heterostructure photocatalysts with the reduction property generated from sewage sludge in its carbonization process. In the obtained CSS photocatalysts, the Cu0 particles are in-situ grown on the surface of the sewage sludge active carbon and inorganic materials (Al2O3 or CaSO4) contained bulk substrate particles to provide long-wavelength absorption ability and fully expose the active sites for photocatalysis. The degradation rate of 2,4-dichlorophenol (DCP) upon UV-Vis-NIR irradiation reaches a high value of 95.5% for the optimum CSS sample, which also possesses Vis-NIR and NIR responsive photocatalytic activities. The enhanced photodegradation rates of DCP over the CSS samples compared with those of their individual precursors are attributed to the localized surface plasmon resonance effect of Cu0 and the efficient charge carrier separation between the heterostructures constructed by Cu0 and its surface oxide of CuO, as well as the impurities of Fe2O3, Fe3O4, and Ca2Fe2O5, resulting in the generation of more O2 center dot- radicals and holes for the dechlorination of DCP and the mineralization of the intermediates. The fabrication strategy of the Cu0-based heterostructure photocatalysts with excellent photocatalytic activities exhibits a promising resource utilization method for the high-value application of Cu sludge.