Synthesis and characterization of TiO2-carbon filter materials for water decontamination by adsorption-degradation processes

Abstract

Wastewater treatment is becoming ever more challenging due to the increasing levels of molecular pollutants that are challenging for existing approaches. Innovative materials are required to help produce potable water from heavily contaminated water sources. One such material is titanium dioxide-activated carbon (TiO2/AC) heterostructures, which combine the photocatalytic properties of TiO2 with the adsorption properties of the ACs. To date, studies on TiO2/AC heterostructures for real-world water purification have yet to be performed. This study aimed to address this gap by comparing the effectiveness of titanium isopropoxide (Ti(OiPr)4) and titanium butoxide (Ti(OBu)4) for synthesizing TiO2/AC heterostructures using four different methods (sol-gel, solvothermal, and microwave-assisted hydrothermal methods [x2]). The elaborated heterostructures were compared with commercial TiO2 materials for their ability to degrade five emerging contaminants (caffeine, hydrochlorothiazide, saccharin, sulfamethoxazole, and sucralose). Hydrochlorothiazide and sulfamethoxazole were demonstrated to be rapidly degraded by UV-C irradiation within 15 min. Caffeine, saccharin, and sucralose were less susceptible to UV degradation. All the elaborated TiO2/AC heterostructures consisted of pure anatase phase, with Ti(OBu)4 syntheses generating larger average crystal sizes and lower surface areas. Sol-gel preparations produced the most effective TiO2/AC heterostructures due to their high surface area. Compared with the commercial TiO2, the heterostructures enhanced the photocatalytic activity of TiO2 by up to 10.0 times. Also, the heterostructures remained effective at environmentally relevant conditions (i.e., concentration of the contaminant and water matrices). The reuse of the materials was tested and showed no reduction in efficiency after four removal/regeneration cycles. Overall, this study presents novel TiO2/AC heterostructures with increased photocatalytic efficiency that can serve as an efficient material for removing contaminants at large scales (e.g., water treatment plants).