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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Abstract
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.