Preparation and characterization of carbon doped TI02 using humic acid and its modified derivative as carbon precursors for enhanced photocatalytic activities

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Date
2011
Authors
Ismail, Ismariza
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Ti02, one of the semiconductor photocatalysts with environmental friendly and economical characteristics had attracted scientific interest over the last 1 0 years. However, Ti02 can onlybe activated by UV light corresponding to its large band gap of3.2 eV. One of the possible approaches in improving the photocatalytic activitiy of Ti02 was via doping of foreign atoms such as non-metallic elements likeN, C and S. In this study, carbon doped Ti02 was prepared by using humic acid (HA) and its , modified derivative, peat coagulant (PC) respectively, as the carbon precursors. The preparation process of the carbon doped Ti02 (CTHA) from HA and carbon doped Ti02 (CTPC) from PC photocatalysts involves two core stages that are doping and thermal treatment process. The optimum doping percentage was found to be 0.025 % and 0.20 % for the photocatalyst prepared from HA and PC respectively. The optimum treatment temperature for the preparation of the photocatalysts was identified at 650°C for CTHA and 620°C for CTPC photocatalyst. The prepared samples were characterized via SEM-EDX, XRD, BET, CHN, UV-vis, FTIR and photoluminescence analyses. The photocatalytic evaluation of the samples was carried out via photodegradation of an anionic dye, reactive red 4 (RR4) in aqueous suspension under illumination of 45 Watt visible light fluorescent lamp as well as under solar irradiation. First order rate constants (k) for the photodegradation of RR4 with CTHA and CTPC samples under 45 Watt visible light fluorescent lamp irradiation was ca. 0.041 and 0.043 min-1 respectively, which is about four times faster than the unmodified Ti02. On the other hand, similar experiment performed under solar irradiation yielded higher photocatalytic activity with k value ca. 0.168 and 0.191 min-1 respectively using CTHA and CTPC samples. The higher photocatalytic activity exhibited by carbon doped Ti02 samples was attributed to the electron scavenging ability of the carbon particles contained in Ti02. The effect of operational parameters such as dye concentration, catalyst loading, aeration rate as well as the pH of the solution has been examined. Results showed that the employment of efficient photocatalysts and the selection of optimal operational parameters may lead to complete mineralization of the model pollutant.
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