Antibiotics abatement in synthetic and real aqueous matrices by H2O2/natural magnetite

Abstract

The removal of micropollutants in wastewater treatment plants (WTTPs) is a challenging issue which requires the development of effective but also green and low-cost strategies. In this work, we explore the capability of naturally-occurring magnetite combined with H2O2 for the degradation of the highly persistent antibiotic sulfamethoxazole (SMX). A complete operating condition study has been performed to evaluate the effect of initial pH (3–7), temperature (15–50°C), magnetite concentration (0.5–2gL−1) and H2O2 dose (12.5–100mgL−1), using an initial SMX amount of 5mgL−1. Remarkably, complete removal of the target pollutant and the aromatic intermediates was achieved operating under ambient-like conditions (25°C) and circumneutral pH (pH0=5) using the stoichiometric dose of H2O2 (25mgL−1) and a catalyst load of 1gL−1. The mineralization yield was above 50%, being the final oxidation products short-chain organic acids. The oxidation pathway of SMX was accordingly proposed. The stability of magnetite was confirmed upon three sequential runs, where a similar catalytic activity and negligible iron leaching (<0.15%wt) were observed. As a proof of concept, the performance of the catalytic system was also evaluated in different real aqueous matrices, such as WWTP effluent, surface water and hospital wastewater. Although the catalyst did not show any sign of deactivation, partial inhibition of the oxidation reaction was observed due to scavenging effects.