Photo-catalytic degradation of mixed gaseous HCHO and C6H6 in paper mills: Experimental and theoretical study on the adsorption behavior simulation and catalytic reaction mechanism

Abstract

VOCs in paper mills have severely exceeded the emission standards and their photo-catalytic degradations should focus on the experimental and theoretical studies. This work used TiO2 colloid as catalyst to study the photo-catalytic degradations of mixed HCHO and C6H6 at five mixing ratios. The adsorption behaviors of pure forms and mixtures on the TiO2 (101) surface were simulated using density functional theory (DFT), and their catalytic reaction mechanisms were also analyzed. The following results were found: (1) With increasing initial concentration, the enhanced adsorption and easy degradation interpreted the increased degradation rate for pure HCHO, while the counteractions of enhanced adsorption and inhibited catalytic reaction kept the constant degradation rate for pure C6H6. (2) For their mixtures, the HCHO degradation was inhibited at high C6H6 concentration due to the inhibited adsorption and catalytic reaction of HCHO. The C6H6 degradation was slightly weakened at high HCHO concentration and then restored to the normal degradation rate of C6H6, which could be attributed to the weakened adsorption of C6H6 and the easy degradation of HCHO in the initial stage. The combined experimental, simulation, and theoretical results provides sufficient information to understand the photo-catalytic degradation process for mixed gaseous pollutants in different realistic environments.