Investigations on the degradation of an antibiotic Cephalexin using suspended and supported TiO2: Mineralization and Durability studies

Abstract

The rise in levels of antibiotics in treated wastewater poses a great threat to human health worldwide. The present study demonstrates the degradation studies of antibiotic Cephalexin using slurry and innovative fixed-bed photocatalysis under UVA (365 nm) irradiations. The decay of Cephalexin was monitored by UV-spectrophotometer/HPLC analysis. Studies showed that the variation in UV intensity, dose variation of TiO2 and H2O2, area by volume (A/V), pH affects the degradation to a great extent. The degradation rate followed the pseudo-first order kinetics with optimized conditions for the degradation of antibiotic were TiO2 1.0 g L-1, H2O2 0.15 mL with UV intensity of 25 Wm-2. Approximately 93% reduction in the concentration of compound was observed after 2 h of irradiations. The COD reduction (80%) along with the generation of nitrite, nitrate and sulphate ions as well as elimination of the parent compound peak in HPLC chromatograms confirmed the complete mineralization of the selected compound. Fixed-bed studies were also carried out with TiO2 coated on spherical cement beads which eliminates the implications of slurry mode photocatalysis. The durability of catalyst was confirmed by recycling the beads for at-least fifty cycles and characterized by SEM-EDAX. An attempt was also made to study pilot-scale fixed-bed baffled solar reactor for the degradation of Cephalexin, which confirmed 70% degradation after 10 h of photocatalytic treatment. Therefore, the technique visualized in this study by employing renewable energy and durable catalyst can provide a viable solution to the industries for treating bio-recalcitrant compounds.