Photocatalytic degradation of 4-chloro-2-methylphenoxyacetic acid using W-doped TiO2

This work was aimed at studying the efficiency of W-doped TiO2 in the photocatalytic degradation of 4-chloro-2-methylphenoxyacetic acid (MCPA). Different wt.% of W-doped TiO2 was synthesized via the sol-gel method and characterized. The characterizations included powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), N-2 sorption, Raman spectroscopy, fluorescence spectrometry, and electron spin resonance spectroscopy (ESR). Result from the BJH pore size distribution shows the materials are mesoporous with BET surface area ranging from 86.08-91.71 m(2)/g. All materials showed polycrystalline anatase phase with decreasing crystal size as the percentage dopant increases. The best photocatalytic activity was obtained with 0.1 wt.% W-doped TiO2 (0.1 WT) at a natural pH of 5, which may have resulted from its relatively reduced band gap; crystal size; and lesser amount of oxygen vacancy. 0.1 WT had an optimum catalyst concentration of 600 mg/L under artificial light irradiation at a rate constant and half-life of 4.31 x 10(-3) s(-1) and 160 s, respectively. The intermediates/products as analyzed by the LC-MS were 2-hydroxybuta-1, 3-diene-1, 4-diyl-bis (oxy) dimethanol and 2-(4-hydroxy-2-methylphenoxy) acetic acid which are relatively safer than MCPA. (C) 2015 Elsevier B.V. All rights reserved.