Sulfite activation and tetracycline removal by rectangular copper oxide nanosheets with dominantly exposed (0 0 1) reactive facets: Performance, degradation pathway and mechanism

Abstract Copper(II) oxide with (0 0 1) facet-exposed nanosheets was prepared via a hydrothermal method. Due to exposure of the (0 0 1) facet, the CuO nanosheets exhibited remarkable catalytic activity towards sulfite activation and tetracycline (TC) degradation across a wide pH range (pH 3.00–9.00), with the degradation rate of TC at pH 4.51–9.00 reaching 87% in the first 5 min. This rapid degradation reaction followed the BMG kinetic model. The CuII OH groups on the (0 0 1) facet of CuO adsorbed negative SO32− to form a CuII SO3− complex and generate SO3 − radicals. Sulfite radicals were oxidized by dissolved oxygen to form SO5 −, and then, SO5 − transformed to SO4 − and then HO . Both SO4 − and HO were the main species involved in TC degradation. The utilization efficiency of sulfite reached almost 100%. After normalization of the degradation rate to the specific surface area, the degradation rate of TC in the current system was 4.84 times that obtained using a CuO nanosphere system. The potential degradation pathways of TC and the catalytic mechanism of the CuO catalyst are proposed.