Abstract: Waste pearl shells were activated and used as carriers to prepare a nano-Cu₂O/pearl shell composite photocatalyst by in situ hydrolysis. The composites were characterized by X-ray diffraction, X-ray photoelectron spectrometer, scanning electron microscopy, and UV-Vis diffuse reflectance spectrometer. Reactive red dye B-3G solutions were used as simulate wastewater to investigate the photocatalytic performance under visible light irradiation. The loaded Cu₂O particles had an average diameter of 16.8 nm, were oval in shape and have absorption bands in the UV and visible region similar to those of pure Cu₂O particles. The nano-Cu₂O/pearl shell composites had much higher photocatalytic activities than pure Cu₂O. Over 98% of the B-3G solutes were decolorized by these composites under the conditions of pH = 6.0–12.0, reaction time = 90 min, and B-3G concentration ≤ 220 mg/L. The photocatalytic decolorization of B-3G followed pseudo-first order kinetics. The formation mechanism of the nano-Cu₂O/pearl shell composites was studied by Fourier transform infrared spectroscopy. It involved the interaction and combination of Cu₂O and CaO.

Key words: pearl shells, in situ hydrolysis, nano-Cu2O, photocatalysis, dye B-3G