Continuous air purification by front flow photocatalytic reactor: Modelling of the influence of mass transfer step under simulated real conditions

In this work, a solution for the treatment of toxic gases based on a photocatalytic process using TiO₂ coated on a cellulosic support, has been investigated. Here, cyclohexane was chosen as the reference for testing its removal efficiency via a continuous front flow reactor as type A anti-gas filters. The photocatalytic support was firstly characterized by EDX, to confirm its elemental composition. Then, the experiments were carried out, starting with a batch reactor in order to evaluate the degradation efficiency of the photocatalytic media, as well as the monitoring of the photocatalytic process which allowed the establishing of a carbon mass balance corresponding to the stoichiometric number of our target pollutant. The transition to a continuous treatment with a front flow reactor aims to highlight the influence of the input concentration (0.29-1.78 mM m^-3) under different flow rates (12, 18 and 36 L min^-1). The relative humidity effect was also investigated (from 5 to 90% of humidity) where an optimum rate was obtained around 35-45%. In addition, the mineralization rate was monitored. The major rates obtained were for a cyclohexane input concentration of 0.29 mM m^-3 in wet condition (38%) at an air flow rate of 18 L min^-1, where the CO₂ selectivity reached 77% for an abatement of 62%. In order to understand the limiting steps of the photocatalytic process, a model considering the reactor geometry and the hydraulic flow was developed. The obtained results showed that the mass transfer must be considered in the photocatalytic process for a continuous treatment. The Langmuir-Hinshelwood bimolecular model was also developed to represent the influence of the humidity.