U.G. Akpan

Parameters affecting the photocatalytic degradation of dyes using TiO2-based photocatalysts: a review.

This paper presents the review of the effects of operating parameters on the photocatalytic degradation of textile dyes using TiO2-based photocatalysts. It further examines various methods used in the preparations of the considered photocatalysts. The findings revealed that various parameters, such as the initial pH of the solution to be degraded, oxidizing agents, temperature at which the catalysts must be calcined, dopant(s) content and catalyst loading exert their individual influence on the photocatalytic degradation of any dye in wastewaters. It was also found out that sol-gel method is widely used in the production of TiO2-based photocatalysts because of the advantage derived from its ability to synthesize nanosized crystallized powder of the photocatalysts of high purity at relatively low temperature.

Decolorization of Sunzol Black DN conc. in aqueous solution by Fenton oxidation process: effect of system parameters and kinetic study

Abstract The decolorization of Sunzol Black DN conc. (SBDN) in aqueous solution by Fenton oxidation process was studied. The effects of different reaction parameters such as initial hydrogen peroxide concentration ([H2O2]o), initial Fe2+ concentration ([Fe2+]o), pH, temperature and the initial SBDN concentration ([SBDN]o) on the decolorization of the SBDN dye have been investigated. The optimal reaction conditions were experimentally determined and it was found to be [H2O2]o = 4 mM, [Fe2+]o = 0.05 mM, pH = 3.5 and [SBDN]o = 100 mg/l at temperature 30°C. Under optimal condition, 94.5% decolorization efficiency of dye in aqueous solution was achieved within 90 min of reaction. The decolorization kinetics of SBDN by Fenton oxidation process followed the second-order reaction kinetics, and the apparent activation energy, was found to be 38.582 kJ/mol.

Enhancement of the photocatalytic activity of TiO2 by doping it with calcium ions

Titanium dioxide (TiO(2)) with an enhanced photocatalytic activity was developed by doping it with calcium ions through a sol-gel method. The developed photocatalysts were characterized by Fourier transform infrared (FTIR) spectroscopy, N(2) physisorption, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction. Their surface morphologies were studied using surface scanning electron microscopy (SEM). The XPS analyses confirmed the presence of Ti, O, Ca, and C in the Ca-doped TiO(2) sample. The activities of the catalysts were evaluated by photocatalytic degradation of an azo dye, acid red 1 (AR1), using UV light irradiation. The results of the investigations revealed that the samples calcined at 300 °C for 3.6h in a cyclic (2 cycles) mode had the best performance. Lower percentage dopant, 0.3-1.0 wt.%, enhanced the photocatalytic activity of TiO(2), with the best at 0.5 wt.% Ca-TiO(2). The performance of 0.5 wt.% Ca-TiO(2) in the degradation of AR1 was far superior to that of a commercial anatase TiO(2) Sigma product CAS No. 1317-70-0. The effect of pH on the degradation of AR1 was studied, and the pH of the dye solution exerted a great influence on the degradation of the dye.

A comparative study of the photocatalytic efficiency of Degussa P25, Qualigens, and Hombikat UV-100 in the degradation kinetic of congo red dye

Abstract The photocatalytic efficiency of three TiO2 photocatalysts; 1 Degussa P25, 2 Qualigens, and Hombikat UV 100 has been investigated on the degradation kinetic of congo red dye. The crystal phases, structures, and crystallite sizes of the catalysts were analyzed by X-ray diffraction, microstructure, and morphology by transmission electron microscopy, and surface area and pore-size distributions by nitrogen physisorption. The results of the kinetic study revealed that the activities of the photocatalysts were dependent on their particle sizes, and the best activity was obtained with Hombikat UV-100, which was of the smallest particle size, was mesoporous, and had the largest surface area. The activation energy required for the degradation of the congo red dye was found to increase proportionately with the particle size of the catalysts. The effects of various operational parameters such as catalysts dosages, initial dye concentration, and temperature were systematically studied in order to achieve ma...

Photocatalytic activity of sol–gel-derived mesoporous TiO2 thin films for reactive orange 16 degradation

AbstractThis study investigates the photocatalytic activity of sol–gel-derived mesoporous TiO2 thin films for reactive orange 16(RO16) degradation. Both surfactant- and non-surfactant-assisted sols were prepared and coated on different glass slides. The prepared catalysts were characterized by X-ray diffraction, surface scanning electron microscopy, UV–vis transmittance spectra, and nitrogen adsorption/desorption isotherms for their properties, while the photocatalytic activities of the TiO2 thin films were evaluated in the degradation of RO16. The surfactant-assisted films showed surface uniformity, reduced particle size, and high photocatalytic activity compared to non-surfactant assisted films. The effects of withdrawal speed on films’ transparency and the number of coatings on UV light absorption and their photocatalytic activities are systematically explained for the surfactant-assisted films. Though there was a continuous increase in the efficiency of the mass of TiO2 per unit area and UV light abso...

Photocatalytic degradation of wastewater containing acid red 1 dye by titanium dioxide: effect of calcination temperature

Abstract The effects of calcination temperature of titanium dioxide photocatalyst have been investigated on the photocatalytic degradation of an azo dye, acid red 1. The photocatalytic activity of the developed catalyst was greatly influenced by the mode of calcination. Photocatalysts subjected to high calcination temperatures (500°C) were not as effective as those calcined at lower temperature and those heat treated in a cyclic mode outperformed those which were calcined in a straight run. The photocatalysts developed were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, surface scanning electron microscopy, and N2 physisorption. Thus, it was found that the properties of the photocatalysts were significantly responsible for their photocatalytic activities.