Solar-driven photocatalytic treatment of diclofenac using immobilized TiO2-based zeolite composites

Abstract

The study is aimed at evaluating the potential of immobilized TiO2-based zeolite composite for solar-driven photocatalytic water treatment. In that purpose, TiO2-iron-exchanged zeolite (FeZ) composite was prepared using commercial Aeroxide TiO2 P25 and iron-exchanged zeolite of ZSM5 type, FeZ. The activity of TiO2-FeZ, immobilized on glass support, was evaluated under solar irradiation for removal of diclofenac (DCF) in water. TiO2-FeZ immobilized in a form of thin film was characterized for its morphology, structure, and composition using scanning electron microscopy/energy-dispersive x-ray spectroscopy (SEM/EDX). Diffuse reflectance spectroscopy (DRS) was used to determine potential changes in band gaps of prepared TiO2-FeZ in comparison to pure TiO2. The influence of pH, concentration of hydrogen peroxide, FeZ wt% within the composite, and photocatalyst dosage on DCF removal and conversion efficiency by solar/TiO2-FeZ/H2O2 process was investigated. TiO2-FeZ demonstrated higher photocatalytic activity than pure TiO2 under solar irradiation in acidic conditions and presence of H2O2.

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

“…). Taking into account the findings of previous study [17], where high affinity of composite photocatalyst TiO 2 -FeZ for DCF adsorption at acidic conditions was established, as well as the fact that DCF removals match TOC removal extents in the same period ( Fig. 1), it can be concluded that all DCF was removed due to adsorption onto the composite surface.…”

“…The light intensity was measured to be 6 124.78 +/-0.11 mW cm -2 using pyranometer CMP21, Kipp&Zonen, Netherland. The experiments were performed at conditions found as optimal in the previous study [17] and submitted to HPLC analysis. Within the second set, the duration of experiments corresponded to sampling times from first set.…”

“…Firstly, FeZ was prepared by solid-state ion exchange using NH 4 ZSM5 zeolite (SiO 2 /Al 2 O 3 = 80) and FeSO 4 ×7H 2 O by the modified procedure of Rauscher et al [22], as referred in Juretic Perisic et al [23]. Then as prepared FeZ was mixed with commercial TiO 2 in the ratio determined as optimal in the previous study [17]; TiO 2 : FeZ wt%= 74.6 : 25.4. Such prepared powder mixture was immobilized on the glass plates (r=37.5 mm), applying the procedure refereed by Kete et al [24], using spin coating (1500 rpm) technique with KW-4A Spin Coater, Chemat Technology, USA.…”

“…H 2 O 2 would be involved in the Fenton catalytic cycle reactions since TiO 2 -FeZ composite contains iron [17].…”

“…The applied immobilized photocatalyst based on TiO 2 is improved by FeZ, iron exchanged zeolite of ZSM5 type, to facilitate higher activity under solar irradiation due to decreased band gap simultaneously enabling the occurrence of Fenton reactions at the catalyst surface [17].…”