Modelling and Test of Microfluidic Photocatalytic Reactor

  • Ahmed Yusuf

Student thesis: Doctoral Thesis

Abstract

Heterogeneous photocatalysis, an advanced oxidation process, continue to gain interest as a viable technology in wastewater remediation for tertiary stage treatment. Conventional photocatalytic reactors are the slurry batch reactors; these reactors are stymied with photon transfer limitations, catalyst agglomeration leading to low exposed catalytic surface area, and difficulty in recovery of catalyst. Alternative solution involves immobilization of photocatalyst on glass which is practical for photocatalytic reactions. Limited exposed photocatalyst active sites is an inherent problem in immobilized systems, and it usually leads to mass transfer limitations. Microreactors can offer properties compatible with photocatalytic reactions – such as high surface to volume ratio, small molecular diffusion distance and better spatial illumination homogeneity − while providing potential solutions to some of the setbacks with conventional slurry system. Application of microreactor in heterogeneous photocatalytic reactions for wastewater treatment remains significantly scarce especially as a tertiary stage treatment in the removal of recalcitrant pollutants. This thesis aimed to test and model photodegradation of contaminants of emerging concern (CEC), such as pharmaceuticals, in a recirculating microreactor. The focus was on degradation of a probe pollutant (4-Nitrophenol) with established kinetics and a selected pharmaceutical namely − 1-(2,6-dichlorophenyl)-1,3-dihydro-2H-indol-2-one, also known as 'Diclofenac Amide' (DCFA). The degradation of these organic molecules was predicted using transport and kinetic models with the aid of a computational fluid dynamics tool, COMSOL Multiphysics©. The prediction encompasses the modelling of all operating conditions employed during the experimental runs. The results showed that mass transfer limitations were highly reduced in the microreactor system used herein. All experimental runs were found to be kinetics-controlled during the degradation of 4-nitrophenol and DCFA. The comparison between two-dimensional (2D) and three-dimensional (3D) model for the degradation of 4-nitrophenol showed that 3D model is more realistic, nonetheless, 2D can still be employed when rapid and preliminary design is required. The findings herein allowed for effective study of organic pollutant degradation in microfluidic systems, which finds application as a tertiary stage wastewater treatment.
Date of AwardMay 2020
Original languageAmerican English

Keywords

  • microreactor; photocatalysis; total recirculation; CFD modelling

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