Dynamics of Diffusion- and Immobilization-Limited Photocatalytic Degradation of Dyes by Metal Oxide Nanoparticles in Binary or Ternary Solutions

Abstract

Photocatalytic degradation employing metal oxides, such as TiO2 nanoparticles, as catalysts is an important technique for the removal of synthetic dyes from wastewater under light irradiation. The basic principles of photocatalysis of dyes, the effects of the intrinsic photoactivity of a catalyst, and the conventional non-fundamental factors are well established. Recently reported photocatalysis studies of dyes in single, binary, and ternary solute solutions opened up a new perspective on competitive photocatalytic degradation of the dyes. There has not been a review on the photocatalytic behavior of binary or ternary solutions of dyes. In this regard, this current review article summarizes the photocatalytic behavior of methylene, rhodamine B, and methyl orange in their binary or ternary solutions. This brief overview introduces the importance of the dynamics of immobilization and reactivity of the dyes, the vital roles of molecular conformation and functional groups on their diffusion onto the catalyst surface, and photocatalytic degradation, and provides an understanding of the simultaneous photocatalytic processes of multiple dyes in aqueous systems.

Recent Advances in Advanced Oxidation Processes for Degrading Pharmaceuticals in Wastewater—A Review

“…Photocatalysis utilizes the transformation of the photonic energy into chemical energy, employing the intrinsic photoactivity of metal oxide, perovskite-type metal oxide, or metal sulfide nanoparticles activated by light irradiation [86,87]. Compared with homogeneous photocatalysis, which utilizes all the reactants and reagents in the same physical states, heterogeneous photocatalysis is preferable to degrade organic pollutants due to the easy separation of the catalysts after the photocatalytic process [88].…”

“…The degradation kinetics of the heterogeneous photocatalysis has been well described by the Langmuir-Hinshelwood (L-H) model [113,114], emphasizing that the oxidation reaction of organic pollutants is the pseudo-first- It should be noted that • O 2 − and • OH radicals, which are generated on the catalyst surfaces, have short lifetimes within ns to µs, and photocatalysis is an ultrafast process [67,68]. Therefore, the photocatalytic degradation rate of organic pollutants depends strongly on the diffusion and immobilization of the target organic pollutants onto the catalyst surfaces, where the organic pollutants are readily oxidized by the radicals [87]. Using several established diffusion models, highly effective photocatalytic degradation of the organic contaminants has been revealed to take place in early irradiation times due to their rapid external film diffusion to the catalyst surfaces.…”

Fast and Effective Removal of Congo Red by Doped ZnO Nanoparticles

“…Nanomaterials-based adsorbents are potential adsorbents because of their singular physical and chemical features, including a moderate synthesis temperature [ 16 ], high surface area, high adsorption capacity, reasonable recyclability, and chemical and thermal stability. Various nano-adsorbents, such as charred biomass [ 17 ], carbon dots [ 18 ], CNTs [ 19 ], zeolites [ 20 ], metal oxides [ 21 ], activated carbon [ 22 ], organic frameworks [ 23 ], and porous materials [ 24 ], have been reported.…”

Electron Regulation in Pt-M (M = Cu, Co, and Ni) Decorated WO3 Thin Films for Photocatalytic Degradation Performance

“…For the possibility of using them to degrade organic contaminants, semiconductorbased photocatalysts have been the subject of intense study during the last several years [1][2][3]. With an energy bandgap (E g ) of around 3.2 eV, titanium dioxide (TiO 2 ) is a well-known conventional semiconducting photocatalyst [4].…”