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Two forms of titanium dioxide, which were Degussa P25 powder and Degussa P25-coated filters, were used in photocatalysis for carbendazim degradation in water under sunlight irradiation. Carbendazim 50 (commercial name) in a concentration of 10 mg/L (equivalent to standard canbendazim of 5 mg/L) was synthesized. The concentration of Degussa P25 powder in a range of 0.005-10 mg/L was investigated for the best efficiency rate; and then that concentration was chosen to compare with the Degussa P25-coated filter. In the processes of coating, Degussa P25 in the concentrations of 0.05-2 g/L (wt/vol) were studied, including Degussa P25 loadings on the filter (0.05-0.3 g/piece), and numbers of filter (1-3 pieces) were investigated for carbendazim 50 degradation. Carbendazim 50 sorption and photolysis were also studied. Lastly, the effect of pH (5, 7, and 9) in water was investigated for both Degussa P25 powder and coated filters. Two conditions were explored, adjusting the pH only 1 time at the beginning and controlling the pH all over 180 min of the irrrdiation time. The results showed that photolysis could not degrade carbendazim in the water. However, for photocatalysis, 2 g/L of Degussa P25 powder yielded the highest efficiency rate as 95.6% with the kinetic constant of 0.032 min-1. In the case of coated filters, Degussa P25 concentration of 0.3 % wt/vol was suitable and the titanium dioxide loading of 0.05-0.3 g per piece of filter was insignificantly different for degradation rates. Also, 1-3 pieces of the filter provided similar efficiency rates with insignificant difference. However, when comparing between Degussa P25 powder and coated filter in the same titanium dioxide concentration, it was found that the efficiency rate from the powder was better than that of the coated filter. When taking up to 120 min, the efficiency rate form the coated filter was then closed to that from the powder. In terms of sorption, both Degussa P25 powder and coated filter showed less than 6 % on the carbendazim sorption. For the effect of pH of the water, it was found that pH 5 and 7 yielded higher degradation rates than that of pH 9 for both conditions. The best reaction rate (0.0404-0.0441 min-1) was from Degussa P25 powder, while that of 0.0206-0.0210 min-1 was from the coated filter from adjusting pH at the beginning.
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