Kinetics of photocatalytic decolourization of cationic dye using porous TiO₂ film

Abstract

In this work, the kinetics of the photocatalytic decolourization of methylene blue (MB) is investigated using different surface morphologies of multilayer TiO 2 coating onto a glass plate under irradiation from a 55-W household florescent lamp. A simple direct dip-coating technique was used, and the coating properties of TiO 2 powder were improved by adding epoxidized natural rubber (ENR) as an organic binder in the coating formulation. The effects of the fundamental parameters that govern the kinetics of the photocatalytic decolourization of MB, such as the mass of TiO 2 coated onto the glass plate, the pH and the TiO 2 surface morphology, were also studied. The kinetics of the MB decolourization in all cases was found to be pseudo-first-order kinetics and was fitted to the Langmuir-Hinshelwood model. The degraded part of the ENR binder led to generating pores within the surface of the TiO 2 /ENR film and converting it into porous form, as confirmed by SEM analysis. Furthermore, TGA, FTIR and leachability analyses were conducted to further confirm the depletion of the ENR from the TiO 2 /ENR film. The kinetics of the MB decolourization and the efficiency of the MB colour removal indicated that the porous TiO 2 /ENR film becomes approximately twice as fast as the non-porous TiO 2 /ENR film.

Photocatalytic Activity of TiO2/AuNRs–SiO2 Nanocomposites Applied to Building Materials

“…Since the degradation processes studied in this work are surface phenomena the textural parameters are key factors for promoting the contact between the TiO2 and the involved molecules [52][53][54][55]. A high surface area promotes the degradation processes [54,[56][57][58] and the pore volume allows the molecule diffusion to activate photocatalyst sites through the pore structure [28,53,59,60]. Successively, nitrogen physisorption tests were carried out in order to evaluate the texture of these composites.…”

Immobilized TiO2-Polyethylene Glycol: Effects of Aeration and pH of Methylene Blue Dye

“…Hence, a pH value lower that 6.5 will cause a poor degradation of MB dye, and this explains the gap in photocatalytic degradation rate obtained beyond pH 6.5 seen in Figure 5b. However, the photoactivity efficiency decreased at pH 12 to become 0.062 min −1 due to the rapid adsorption of dye which covered the photocatalyst surface, thus resulting in a slower photocatalytic activity [35]. Nonetheless, the removal rate of MB by TiO 2 /PEG film was largely attributed to adsorption, since the visible blue-stained surface indicated that the film was not fully photocatalytically degraded.…”

Bioflocculation of Basic Dye onto Isolated Microbial Biopolymers

“…This model depends on sorption equilibrium capacity and can be identified as 28 t/q t = (1/k 2 q e 2 )+ t/q e (6) where k 2 is the second-order reaction rate equilibrium constant (g mg -1 min -1…”

“…Therefore, the environmental protection agencies call it as mandatory to treat dye bath effluents prior to discharging them into the surrounding aquatic systems or planning any reuse 4 . Coloured effluents contaminated with dyes are usually treated with several physicochemical de-colourization processes, such as coagulation, precipitation, ozonation, photo-catalysis 5,6 , irradiation, and filtration 7 . Among these technologies, none has appeared as a panacea owing to high costs, low efficiency, and limited versatility 8 .…”