Visible-light-driven photocatalytic disinfection of raw surface waters (300–5000 CFU/mL) using reusable coated Ru/WO3/ZrO2

Abstract

We selected ruthenium (Ru) to improve the photocatalytic activity of a WO3/ZrO2 composite. The synthesized Ru/WO3/ZrO2 was then compared to a benchmark photocatalyst (S-TiO2) in terms of photocatalytic disinfection of raw surface waters collected from the Nile Delta region, Egypt. The photocatalysts were immobilized on aluminum plates with polysiloxane to test them in repetitive cycles under the irradiation of a metal-halide lamp. Bacterial concentrations in the raw waters ranged from 300 to 5000 CFU/mL (CFU: colony-forming units) and different species and genus were detected including gram-negative (e.g., shigella, salmonella, vibrio parahaemolyticus, and vibrio cholera) and gram-positive bacteria (e.g., enterococcus). Ru/WO3/ZrO2 deactivated over 90 % of the bacterial content within 120 min for most sources, whereas S-TiO2 did not perform as highly. The bacterial count after 240 min of irradiation was below the detection limit for all different water sources. Moreover, the inhabitation of photocatalytic disinfection by natural organic matter (NOM) was investigated. Ru/WO3/ZrO2 was stable for four continuous cycles (960 min in total), suggesting the viability for practical application.