Photocatalytic degradation of binary and ternary mixtures of antibiotics: reactive species investigation in pilot scale

The present study investigates the photocatalytic degradation of three quinolone antibiotics (i.e., Flumequine (FLU), Oxolinic Acid (OA) and Nalidixic Acid (NA)) in mono-, binary and ternary compound systems. The closed-loop step photo-reactor and TiO2 impregnated on cellulosic paper as supported photo-catalyst in presence of UV light irradiation were used. The degradation of FLU occurred within 4 h. A 65.4% mineralization of OA was observed in a mono-compound system, due to the fast conversion of these main by-products formed. Besides, the investigation of the contribution of free radicals revealed the involvement of hole (h(+)), O-2(center dot-), but mainly "OH on the degradation of OA. The second-order kinetic rate constants calculated relative to the contribution of (OH)-O-center dot radicals on the degradation of OA was 4.03 x 10(9) M(-1)s(-1), whereas for that of NA was 4.42 x 10(9) M(-1)s(-1), thus underscoring that (OH)-O-center dot coproduct is the primary reactive species implicated in the photocatalytic degradation of these compounds on TiO2/cellulosic paper catalysts. The mono-compound system shows a higher degradation rate compared to multi-compound system (binary and ternary) which explained by the competitive adsorption of antibiotics on the available active sites of photocatalyst surface. Overall, the constant photocatalytic rates are higher following this order: mono compound system > ternary mixture >binary mixture. The catalyst was characterized by mean of FTIR, HR-TEM and XRD. The SiO2-binder role was discussed in details based on the atomic distribution of elements on the cellulose fibers as shown by the EDS atomic mapping. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.