Enhanced degradation of venlafaxine induced by Fe2O3/CeO2 2 O 3 /CeO 2 heterostructures through the thermal transformation from type I to direct Z-scheme in heterogeneous photo-Fenton

Heterostructures based on Fe2O3/CeO2 2 O 3 /CeO 2 were synthesized by coprecipitating iron and cerium salts, with 70 % and 50 % atomic percentage of iron, and heat treatment at 600 and 800 degrees C (Fe70Ce600, Fe50Ce600, Fe70Ce800, Fe50Ce800). The catalytic activity in the Fenton and photo-Fenton process was evaluated in the degradation of venlafaxine (VEN) using UV/Vis LEDs. Treatment at 800 degrees C promoted greater crystallinity, increased crystallite size, decreased specific area, and high absorption between 200 and 600 nm, and bandgap energy (Eg) g ) between 1.6 and 3.0 eV were observed. The heat treatment promoted different mechanisms in heterostructure materials with type I (straddling) schemes for Fe70Ce600 and Fe50Ce600, type II for Fe50Ce800, and direct Z for Fe70Ce800 responsible for generating a higher concentration of HO center dot radicals, high oxidation-reduction power (---Fe2+/---Fe3+) - -- Fe 2+ / - -- Fe 3+ ) and (---Ce4+/---Ce3+), - -- Ce 4+ / - -- Ce 3+ ), greater effective separation of charge carriers, providing improved catalytic activity due to the synergy between heterogeneous photocatalysis and photo-Fenton processes. LC-MS/MS analysis identified 12 transformation products (TPs), involving hydroxylation reactions, demethylation, and loss of cyclohexanol. The transformation products TP2 and TP9 were exclusive to Fe70Ce800, confirming different mechanisms among the heterostructures.