Photocatalyst-coated carbon microtube electrodes: Preparation and characterization of their properties and photocatalytic degradation of methylene blue.

Photocatalysis is a potential technology for removing pollutants from water. As the recombination of the photogenerated electron-hole pairs can hinder the photocatalytic efficiency in the treatment of wastewater, the surface of the carrier is usually coated with a semiconductor. In this study, carbon microtube electrode prepared from corncob was coated with either titanium oxide (TiO) or bismuth phosphate (BiPO) and then used as a photocatalyst (C-TiO or C-BiPO) to investigate the photodegradation of methylene blue (MB). The two photocatalysts, C-TiO and C-BiPO, were characterized by phase determination, microstructure observation, water contact angle measurement, and base site analysis. The influences of reaction time, stability, MB concentration, initial pH, and OH radicals quenching on the degradation of MB were also evaluated. The degradation of MB by C-TiO and C-BiPO was mainly dominated by OH radical oxidation. The carbon microtube increased both the mass transfer rate and the photogenerated electron-hole pairs separation rate, thereby increasing the photocatalysis of both C-TiO and C-BiPO as revealed by an increase in the rate of MB degradation. The rate constants obtained for the degradation of MB by C-TiO and C-BiPO at 20 °C were 9.739 × 10 mM min and 1.111 × 10 mM min, respectively. The coating of TiO and BiPO on the surface of the carbon microtube electrode enhanced their photocatalytic performance, and therefore, C-TiO and C-BiPO could be developed into a novel material to be used in the photodegradation of dye pollutants.