Enhanced degradation of sulfamethoxazole antibiotic from aqueous solution using Mn-WO3/LED photocatalytic process: Kinetic, mechanism, degradation pathway and toxicity reduction

This study was aimed to explore of the photocatalytic degradation and mineralization of sulfamethoxazole (SMX) by a Mn-WO3/LED process in an LED photoreactor. The effects of operational parameters such as catalyst dosage, pH, initial SMX concentration and reaction time on the efficiency of Mn-WO3/LED process was investigated. Toxicity assays were also performed with both raw and treated SMX solutions by Daphnia Magna. The Mn-WO3 nanoparticle was characterized by various analytical procedures including XRD, FESEM, TEM, FTIR, BET and TGA. In addition, complete degradation of SMX was achieved at solution pH of 6, photocatalyst dosage of 2.3 g L-1 and reaction time of 70 min. Decomposition mechanism indicated that the remarkable ability of HO center dot free radicals was the main factor responsible for degradation of SMX in the Mn-WO3 process under LED irradiation. The mineralization of SMX in optimal conditions reached to 63% and 85% within 90 and 180 min, respectively. The presence of main anions in water did not considerably influence on the SMX decomposition. Moreover, degradation intermediates of SMX were finally turn up to simple substances such as maleic and oxalic acids. The toxicity analysis showed that the treated SMX aqueous sample was significantly reduced compared to the raw solution. The electrical energy per order (EEO) indicated that energy consumption in the studied process was lower than that in other studies. Therefore, the Mn-WO3 process with LED photoreactor is an emerging, cost-effective and attainable process which can be successfully applied to degrade and mineralize the medical drugs such as SMX.