Solar Light Responsive Poly(vinyl alcohol)-Assisted Hydrothermal Synthesis of Immobilized TiO2/Ti Film with the Addition of Peroxymonosulfate for Photocatalytic Degradation of Ciprofloxacin in Aqueous Media: A Mechanistic Approach

Abstract

This study is focused on the synthesis of a solar light driven novel poly(vinyl alcohol) (PVA)-assisted TiO2/Ti film via a facile one pot hydrothermal technique and then its photocatalytic applications by adding with peroxymonosulfate (PMS) for efficient degradation of ciprofloxacin (CIP). The key hydrothermal synthesis parameters like PVA-content, hydrothermal time (HT), and pH were optimized. The best photocatalytic performance of the synthesized material was observed when prepared with the conditions of PVA = 8 mg, HT = 3 h, and pH = 2.62. Results showed that 98.3% of CIP was degraded within 60 min by PVA-assisted TiO2/Ti film with 0.5 mM PMS added, compared to 89.38% and 88.86% degradation with 0.5 mM persulfate (PS) and 0.5 mM hydrogen peroxide (H2O2), respectively. The photocatalytic degradation of CIP by PVA-assisted TiO2/Ti film with PMS added was dependent on the [PMS]0 and increased with increase in [PMS]0. The kapp values at [PMS]0 of 0.2, 0.5, 0.8, and 1.0 mM were 0.029, 0.0582, 0.068, and 0.128 min-1, respectively. The photocatalytic degradation of CIP by PVA-assisted TiO2/Ti film with PMS added under solar light irradiation was highly dependent on the [pH]0 as well as on the presence of coexisting anions like HCO3-, CO32-, NO2-, Cl-, and SO42-. Natural organic matter (NOM) retarded the photocatalytic degradation of CIP by PVA-assisted TiO2/Ti film with PMS added under solar light irradiation due to its strong scavenging ability toward •OH and SO4•-. The photocatalytic degradation of CIP by as-prepared photocatalyst under solar light irradiation was higher in Milli-Q water (kapp = 0.0582 min-1) than tap water (kapp = 0.0342 min-1) followed by river water (kapp = 0.0259 min-1) and then synthetic wastewater (kapp = 0.0212 min-1). The degradation products of CIP were investigated by UPLC-MS/MS, and accordingly degradation pathways were proposed. Moreover, the mineralization, ecotoxicity, and cyclic photocatalytic stability of the as-prepared photocatalyst were also investigated. These findings suggest that as-prepared PVA-assisted TiO2/Ti film with PMS added is a promising alternative for the treatment of wastewater containing antibiotics.