Copper atoms inlaid in titanium zirconium oxide spherical shell confine free radicals for the robust Fenton-like treatment of complex biogas slurry

Abstract

A novel Fenton-like system based on single-atom catalysts was developed for the treatment of biogas slurry under 90 °C conditions. First, a binary composite was synthesized in which porous TiZrO4 hollow spheres provided sites for embedding Cu atoms and confining generated free radicals to promote the efficiency of oxidation reactions. The TiZrO4/Cu catalyst mediated the simultaneous oxidation of approximately 69 % of the chemical oxygen demand and at least 55 % of total nitrogen in biogas slurry within 1 h, and the residual organics, including simple acetic acid and propionic acid, possessed high biodegradability. Correspondingly, all of the fluorescent fulvic acids, proteins, polysaccharides, and humic acids disappeared. DFT calculations further confirmed that the electron-rich single Cu atoms generated hydroxyl radicals by capturing and reducing H2O2, thus improving the treatment efficiency. The special catalyst structure with dispersed Cu atoms maintained excellent catalytic activity and durability with negligible Cu leakage over multiple cycles.