Diclofenac removal by simulated solar assisted photocatalysis using TiO2-based zeolite catalyst; mechanisms, pathways and environmental aspects

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2016-11, Vol.304, p.289-302
• Main Authors: Salaeh, Subhan, Juretic Perisic, Daria, Biosic, Martina, Kusic, Hrvoje, Babic, Sandra, Lavrencic Stangar, Urska, Dionysiou, Dionysios D., Loncaric Bozic, Ana
• Format: Article
• Language: English
• Subjects: Biodegradability; Degradation pathway; Diclofenac; Solar photocatalysis; TiO2-FeZ catalyst; Toxicity
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2016.06.083

[Display omitted] •We studied diclofenac (DCF) degradation by immobilized TiO2-zeolite catalyst (TiO2-FeZ) under solar irradiation.•Degradation mechanism includes surface adsorption and subsequent degradation.•Solar/TiO2-FeZ/H2O2 process resulted in significant improvement in biodegradability of DCF water solution.•The presence of Cl− and SO42− influenced degradation pathway and consequently toxicity changes of DCF water solution. The study explores the potential of immobilized TiO2-based zeolite composite photocatalyst (TiO2-FeZ) made of commercial AEROXIDE TiO2 P25 and iron-exchanged zeolite of ZSM5 type (FeZ), for solar assisted treatment of diclofenac (DCF), pharmaceutical included in the “watch list” during last prioritization in water legislation by EU. In this study the efficiency of applied photocatalytic treatment, solar/TiO2-FeZ/H2O2, of DCF water solution was evaluated on basis of DCF removal and conversion kinetics, as well as the changes of common parameters for assessing water quality. Hence, the changes in the removal and mineralization of overall organic content, biodegradability, toxicity to Vibrio fischeri, dechlorination of DCF and its formed by-products, were monitored during the treatment. The obtained data were correlated with the evolution of DCF by-products, identified and monitored during the treatment by HPLC/MSMS analysis. In order to estimate the influence of water matrix, all experiments were performed in the presence of chloride or sulphate as counter ions. The obtained data revealed that degradation mechanism of DCF by applied treatment process using immobilized TiO2-FeZ includes the adsorption onto photocatalyst surface and consequent degradation. The contribution of homogeneous Fenton reaction due to leached iron ions was found to be negligible. The adsorption and degradation pathway of DCF were influenced by the type of counter ions, which was reflected in the observed changes of water quality parameters.