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Optimization of Solar Photocatalytic Degradation of Chloroxylenol Using TiO2, Er3+/TiO2, and Ni2+/TiO2 via the Taguchi Orthogonal Array Technique

Department of Chemical and Process Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, Bangi, Selangor 43600, Malaysia
Environmental Research Center, University of Technology, Baghdad 10001, Iraq
Author to whom correspondence should be addressed.
Academic Editor: Keith Hohn
Catalysts 2016, 6(10), 163;
Received: 22 August 2016 / Revised: 6 October 2016 / Accepted: 11 October 2016 / Published: 20 October 2016
In this study, the optical properties of a TiO2 photocatalyst were enhanced with various impregnations of Er3+ and Ni2+ separately, using the impregnation method as photocatalysts for the direct solar photolysis degradation of chloroxylenol. The synthesized Er3+/TiO2 and Ni2+/TiO2 catalysts were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), metal mapping, and ultraviolet visible (UV–Vis) spectroscopy. The results showed that the Er3+/TiO2 and Ni2+/TiO2 nano-particles have the same structures of TiO2 nano-particles with little difference in particle size. The Er3+ and Ni2+ ions were well-distributed on the TiO2 surface, and it was found that the maximum band gap decreased from 3.13 eV for intrinsic TiO2 to 2.63 eV at 1.8 wt % Er3+/TiO2 and to 2.47 eV at 0.6 wt % for Ni2+/TiO2. The initial concentration of chloroxylenol, catalyst loading, and pH of the solution are the most important factors affecting the solar photocatalytic degradation efficiency that were optimized using Design Expert software (version 6.0.10, Minneapolis, MN, USA, 2003). The results showed that the optimal conditions for chloroxylenol degradation include a pH of 4, TiO2 loading at 3 g/L, and a chloroxylenol concentration of 50 mg/L. These conditions resulted in a degradation efficiency of 90.40% after 60 min of direct solar irradiation, wherein the solar energy recorded during a clear sunny day is 1000 W/m2. However, some experiments were conducted on a semi-cloudy day to cover all weather stated and to study the degradation kinetics. During semi-cloudy day experiments, using Er3+/TiO2 and Ni2+/TiO2 with a solar irradiation activity of 600 W/m2 for a 60 min exposure at optimal conditions increased the degradation efficiency from 68.28% for intrinsic TiO2 to 82.38% for Er3+/TiO2 and 80.70% for Ni2+/TiO2. View Full-Text
Keywords: photocatalyst; chloroxylenol; photocatalytic degradation; kinetics photocatalyst; chloroxylenol; photocatalytic degradation; kinetics
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Mohammed, A.J.; Kadhum, A.A.H.; Ba-Abbad, M.M.; Al-Amiery, A.A. Optimization of Solar Photocatalytic Degradation of Chloroxylenol Using TiO2, Er3+/TiO2, and Ni2+/TiO2 via the Taguchi Orthogonal Array Technique. Catalysts 2016, 6, 163.

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