Design, Mass Transfer Studies, and Optimization of an Air-Sparged Tubular Photocatalytic Reactor for the Degradation of Methylene Blue

Abstract

Abstract-An alternative process for the removal of organic pollutants in aqueous systems is photocatalysis. The challenges hindering its industrial use are electron-hole recombination and mass transfer limitations. In order to address these problems, the objective of this study is to introduce air by sparging, and design an air-sparged photocatalytic reactor using titanium dioxide immobilized on borosilicate glass. The performance of the reactor on the removal of the model pollutant, methylene blue (MB), was evaluated and compared against the reactor operated without sparging. The effect of mass transfer limitations on reactor performance was also investigated by regression using a Langmuir-type model equation. Reactor performance was optimized using Response Surface Methodology to determine the set of initial MB concentration, treatment time, initial pH, and sparging rate that would result to the highest removal of methylene blue. The sparged photocatalytic reactor was able to degrade 57% MB in 2 hours, an improvement of 40% compared to no sparging. Mass transfer limitation studies showed that the reactor operates near the reaction-limited regime, and that the extent of mass transfer limitation effects was reduced. The set of parameters that maximizes methylene blue removal were 2.0 ppm MB, 120 minutes treatment time, pH 9.95 and 2.0 L/min sparging rate, with a predicted removal of 55.5%. Validation experiments resulted to 57.2% MB removal, and that the present reactor is comparable to similar reactors in literature, but with the advantage of using less expensive materials of construction and simpler immobilization technique.Index Terms-Photocatalysis, response surface methodology, tubular photocatalytic reactor, wastewater treatment.

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

“…This configuration, even if it is less developed in the laboratory, remains interesting because it allows to have a compact reactor able to work at high flow rates by promoting mass transfer whatever the contact time is sacrificed (Vuong., 2011;Debono et al, 2018;Malayeri et al, 2021;Oliveira De Brito Lira et al, 2021). It is well known that tangential flow reactors are most common in the literature, where the residence times is longer but the limitation by mass transfer is more important (Dalida and Ramoso, 2017;Sundar and Kanmani, 2020). For continuous flow reactors, it is generally assumed that they operate under ideal plug flow configuration, and for which, degradation rates are determined ignoring dispersion/diffusion phenomena (Zhong et al, 2017;Salvadores et al, 2020).…”