Morphology-dependent activation of hydrogen peroxide with CuO for tetracycline hydrochloride degradation in bicarbonate aqueous solution.

The design of efficient heterogeneous catalysts in bicarbonate-activated hydrogen peroxide systems (BAP) is a hot topic in wastewater treatment. In this work, CuO nanoparticles with different morphologies including cubic shape (c-CuO), octahedron shape (o-CuO) and spherical shape (s-CuO), were applied in BAP for the first time to degrade tetracycline hydrochloride (TC). Compared with Cu ions and CuO, TC degradation was boosted in the presence of CuO in the BAP system, with the degradation rate following the order c-CuO > o-CuO > s-CuO. The morphology-dependent effects could be linearly correlated with the ratio of surface oxygen species (O), but not with the surface area or Cu(I) ratio. The c-CuO catalyst with exposure of (100) facets contained 76.6% O as the active site for HO adsorption and activation, while the value was much lower for o-CuO and s-CuO with dominant (111) facets. The presence of HCO enhanced the interactions among CuO, HO and TC, leading to facile oxidation of Cu(I) to Cu(II) by HO, and the formation of various reactive species such as hydroxyl radicals and Cu(III) contributed to TC degradation. This work provides a new method for enhancing HO activation with heterogeneous catalysts by crystal facet engineering.