Photocatalytic Oxidation of Toluene in Indoor Air Using UV-A Irradiated TiO2-Coated Honeycomb Monolith

Abstract

Indoor air contamination by volatile organic compounds such as toluene poses significant health and environmental concerns due to prolonged human exposure and the formation of secondary atmospheric pollutants. The present study investigates the photocatalytic oxidation of toluene in indoor air using UV-A irradiated TiO₂-coated honeycomb monolith systems under controlled operating conditions. The research focuses on evaluating the influence of catalyst coating characteristics, ultraviolet irradiation intensity, airflow rate, inlet toluene concentration, and residence time on photocatalytic degradation efficiency and mineralization performance. Titanium dioxide-coated honeycomb monoliths were employed owing to their high surface area, low pressure drop, and enhanced mass transfer properties, which improve photocatalytic reaction kinetics. Experimental observations demonstrate that UV-A irradiation activates the TiO₂ surface, generating reactive oxidative species capable of decomposing toluene molecules into less harmful products such as carbon dioxide and water. The study further reveals that optimized operating conditions significantly enhance toluene conversion efficiency while minimizing intermediate byproduct accumulation. Increased irradiation intensity and controlled airflow conditions were found to improve photocatalytic activity and pollutant removal performance. Comparative assessment with conventional air purification methods indicates that photocatalytic oxidation provides superior advantages in terms of energy efficiency, continuous operation, and reduced secondary pollution generation. In addition, the structured honeycomb monolith configuration contributes to stable long-term catalytic performance and operational durability for indoor air treatment applications.