Photocatalytic Degradation of Diazo Dye over Suspended and Immobilized TiO2 Catalyst in Swirl Flow Reactor: Kinetic Modeling

Waleed Jadaa,Ajay K Ray,Anand Prakash

doi:10.3390/pr9101741

Abstract

The degradation kinetics of Direct Blue 15 (DB15), a diazo dye, were studied over a suspended and immobilized TiO2 catalyst. For all experiments, the kinetics experiments were performed in a swirl flow photoreactor under the influence of UV light. The effect of different parameters: dye concentration, catalyst loading, and light intensity, on the DB15 kinetics was investigated. The kinetic rates were assessed using apparent (ka) approach, a single value of reaction rate (kr) and adsorption constant (K), and approach of kr as of variable. The DB15 mineralization was discussed as well. Using a dip-coating device, the P25 catalyst was deposited on a Pyrex glass. The thin film surface characterization was examined. The coated catalyst was evaluated by checking the effect of two variables: initial dye concentration and light intensity on the DB15 kinetics. In terms of the ka approach, the results demonstrated that DB15 degradation is described by the pseudo first-order kinetics model. The Langmuir-Hinshelwood (L-H) model was fitted well with the experimental data for the number of process variables. L-H constant kr was determined as a function of three parameters: initial dye concentration, catalyst loading, and light intensity. The ka values were evaluated and compared with experimental results. In terms of three variables, ka can be expressed as ka=0.15 [C]o−0.69 [W]0.73 I0.91 1+0.17 [C]o while the empirical model results in the following expression, ka=0.77 [C]o−1.65 [W]0.73 Io0.89. It was observed that 83.64% mineralization was achieved after a period of 16 hrs. In terms of immobilized catalyst, the DB15 degradation kinetics was described by a pseudo first-order model for different dye concentrations. Meanwhile, a power-law model described the impact of light intensity on dye kinetics. In addition, the coated catalyst was successfully reusable with high efficiency for up to four cycles.

Highlights

Introduction published maps and institutional affilWater pollution is continuously gaining great interest globally due to its health implications
The decolorization of dye solutions was evaluated from their maximum absorbance at 598 nm [36] by converting absorption to concentration through a calibration curve that was prepared earlier than dye degradation experiments
As the pH values decrease and become lower than pzc range values, the Direct Blue 15 (DB15) removal is increased. This behavior is explained by the presence of a strong attractive force between anionic DB15 and the positively charged Degussa surface, which results in the adsorption of large amounts of

Summary

Introduction

Water pollution is continuously gaining great interest globally due to its health implications. Within the last few decades, tremendous efforts have been invested into water and/or wastewater treatment applications to reduce environmental problems and achieve protection for humans and the environment [1,2]. The presence of organic pollutants such as colored dyes in industrial aqueous effluents is considered a major environmental issue. If the colored wastewater reaches the surface and/or ground water, it can result in contamination of the drinking water system. This is a serious problem that threatens human health [3,4]. The presence of such colored dyes in effluents can directly harm aquatic species.

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Conclusion