Nano-TiO2 immobilized polyvinylidene fluoride based spongy-spheres for ciprofloxacin photocatalytic degradation: antibacterial activity removal, mechanisms, UVA LED irradiation and easy recovery

Abstract

TiO₂ is promising for the photocatalytic treatment of water contaminated with organic micropollutants. However, it is hard to recover TiO₂ slurry from water. Energy-intensive separation methods are required to recover TiO₂, which is a setback in the effective use of TiO₂ in water treatment. Herein, we present nano-TiO₂ immobilized with polyvinylidene fluoride spongy beads (TP) via simple phase inversion of the mixture of TiO₂ (1%), PVDF (13%) and PVP (0.7%) for the degradation of ciprofloxacin (CIP), a micropollutant in water, under UVA LED irradiation with easy TP recovery. The stable immobilization of TiO₂ with PVDF beads is attributed to interactions between Ti and F atoms. The pseudo first-order rate constant value (k_obs = 0.0761 min⁻¹) was determined for the degradation of CIP by TP. Radical scavenging, chronoamperometry, and ESR analysis revealed the presence of O₂⁻˙, h⁺, HO˙ and ¹O₂ reactive species. LC-HRMS analysis detected ten degradation byproducts with possible degradation pathways. Importantly, the antibacterial activity of CIP against Bacillus subtilis and Escherichia coli was totally removed after 60 min treatment. TP beads were easily recovered using a simple strainer. TP was recovered and reused 30 times, and the absence of significant TiO₂ leaching into water demonstrated its stable immobilization. TP photocatalysis under UVA LED irradiation proves an energy-efficient treatment method with an electrical energy per order of 24.20 kW h m⁻³. Overall, the study highlights a concrete way to effectively use the TiO₂ photocatalyst for water treatment via immobilization using a simple phase inversion method.