Pilot-scale single-step reactor combining photocatalysis and photo-Fenton aiming at faster removal of Cephalexin

A solar pilot-scale cascade reactor system with novel Fe TiO2 composite beads possessing unusual characteristics of in-situ dual effect i.e. coupling of photocatalysis and photo-Fenton has been investigated in once-through mode. The cascade arrangement of packed-bed reactors maintained sufficient turbulence in the system besides eliminating the implications of film-diffusion resistance. The synergistic effect (10%) of in-situ dual process over individual processes has significantly reduced the treatment time of a recalcitrant antibiotic, Cephalexin (CEX). The reaction performance of the once-through cascade reactor system (comprising of six packed-bed reactors in series) incorporating in-situ dual effect at optimized conditions i.e. H2O2: 600 mgL(-1), flow rate: 50 mLmin(-1), with a space time (T) of 12 min approached to that of plug-flow reactor (PFR). The mineralization of CEX was evaluated through reduction in COD (70%) and TOC (63%) along with generation of anions and evolution of CO2. The treated solution of CEX was completely non-toxic as confirmed through Kirby-Bauer test and bio-assay analysis based on toxicity factor. In addition to this, Fe TiO2 composite beads depicted an excellent recyclability efficiency (>70 recycles) even under continuous flow conditions as confirmed through SEM/EDS, DRS, XRD, XPS and TGA analysis. The overall cost of treatment process was evaluated in detail to visualize the practical feasibility of the presented high performance reactor system. (C) 2018 Elsevier Ltd. All rights reserved.