Microwave-assisted sol-gel synthesis of an Au-TiO2 photoanode for the advanced oxidation of paracetamol as model pharmaceutical pollutant

Abstract

An Au-TiO2 photoanode on carbon cloth has been synthesized by microwave-assisted sol-gel method to treat paracetamol solutions at pH 3.0 by photocatalysis (PC), electro-oxidation (EO), photoelectrocatalysis with UVA light (PEC), solar PEC (SPEC) and hybrid methods with photoelectro-Fenton under UVA (PEC+PEF) and sunlight (SPEC+SPEF) irradiation at constant anodic potential (Ean). The photoanode has been characterized by XRD, Raman spectroscopy, HRTEM and SEM-EDS. The counter electrode was a 316L stainless steel plate, which was replaced by an air-diffusion electrode for H2O2 generation in hybrid treatments. The most powerful process was SPEC+SPEF, yielding total paracetamol removal in less than 30 min and 24% mineralization after 180 min, at Ean = +0.82 V. The paracetamol decay followed a pseudo-first-order kinetics in PEC. A lower rate constant was obtained upon increase of pharmaceutical concentration, showing good linear fit using a Langmuir-Hinshelwood model.