Kinetic Modeling of the Photocatalytic Degradation of Chlorinated Aromatic Volatile Organic Compounds: Mass Transfer Enhancement

Chlorobenzene (CB) and Chloronaphthalene (CN) emissions from cement plant operations pose significant environmental risks. This study investigates the mass transfer effects of chlorinated aromatic Volatile Organic Compounds (VOCs), specifically CB and CN, in the gas phase of a continuous-tangential-flow annular photocatalytic reactor. The experiments involved introducing CB and CN into the reactor, and the degradation kinetics were analyzed using the Langmuir-Hinshelwood (L-H) model. The L-H model was applied to assess the impact of the flow rate, concentration, and relative humidity (% RH) on the degradation rate (DR). The results indicate that both the experimental and simulated degradation rates improved with increased flow rates (1 to 9 m3 center dot h-1) and inlet concentrations (30 to 216 mg center dot m-3). This enhancement of the DR correlates with the availability of active OH* species on the TiO2 surface. The L-H model emphasizes the role of H2O molecules in VOC removal kinetics. The degradation rates increased with a rising water content (5 to 55%), but adverse effects on VOC conversion were observed beyond a 55% RH. This study reveals a mass transfer effect, with internal diffusional limitations in the TiO2 pores under operational conditions. The kinetics were predominantly controlled by chemical kinetics and catalyst pore availability. Furthermore, this study demonstrates a higher CB degradation than CN in the reactor and experimental conditions. For a concentration of 1.328 mM center dot m-3, the CB DR ranged from 0.70 to 2.84 mu M center dot m2 center dot s-1, as the flow rate varied from 1 to 9 m3 center dot h-1. The CN DR varied from 0.60 to 2.20 mu M center dot m2 center dot s-1 within the same flow rate range.