Photocatalytic Removal Of Congo Red Dey In Water With A New Ternary Photocatalyst TiO₂-Graphite/MgO Under Solar Irradiation

Considering the low adsorption capacity and high recombination rate of electron-hole pairs of the pure Ti O2 catalyst, a method was speculated which was the composition of Ti O2 with magnesium oxide( Mg O), magnesium hydroxide( Mg(OH)2)and magnesium ferrite respectively( Mg Fe2O4).TiO2-Mg O as a new binary photocatalyst was fabricated firstly by the sol-gel method. Mg O was used for enhancing the adsorption to recalcitrant organic pollutants, which can promote the increase in photocatalytic activity of Ti O2. The adsorptive and photocatalytic experiments of Congo red dye were conducted respectively to demonstrate the adsorption capacity and photocatalytic activity of Ti O2-Mg O. The results demonstrated that the adsorption capacity of Ti O2-Mg O increases with the decrease of the ratio of Ti O2 to Mg O and that 1:0.010 was the optimal ratio. The photocatalytic activity of Ti O2-Mg O increases with the increase of the amount of Mg O when the ratio was smaller than 1:0.010. However, when the ratio was higher than 1:0.010, the photocatalytic activity of Ti O2-Mg O decreases with the increase of the amount of Mg O. The characterization of Ti O2-Mg O demonstrated that only the anatase phase Ti O2 was present in the binary Ti O2-Mg O and that Mg O was well dispersed in Ti O2-Mg O.MgFe2O4 which was prepared with the sol-gel method was a magnetic semiconducting material. Binary photocatalyst Ti O2-Mg Fe2O4 and Ti O2-Mg(OH)2 was also synthesized with sol-gel method. The removal of Congo red dye in water demonstrated that the photocatalytic activity of Ti O2-Mg Fe2O4 and Ti O2-Mg(OH)2 reflected no remarkable effect than pure Ti O2.TiO2-Graphite/Mg O as a new highly active ternary photocatalyst was fabricated successfully. Graphite was used for promoting the separation of electro-hole pairs photogenerated in Ti O2 and Mg O was used for enhancing the adsorption to recalcitrant organic pollutants to achieve a marked synergetic effect for the photocatalytic removal of Congo red dye in water. The characterization of as-prepared samples demonstrated that only the anatase phase Ti O2 was present in the ternary photocatalyst and that graphite and Mg O were well dispersed in Ti O2-Graphite/Mg O. The removal of Congo red dye in water was conducted under solar irradiation to evaluate the photocatalytic activity of Ti O2-Graphite/Mg O. The experimental results showed: the apparent removal rate constants were 0.0151, 0.0179, 0.0188 and 0.0214 min-1 in the systems containing pure Ti O2, Ti O2-Mg O, Ti O2-Graphite and Ti O2-(Mg O + Graphite), respectively. However, the rate constant reached 0.0306 min-1 when Ti O2-Graphite/Mg O was used as photocatalyst; there was a remarkable synergetic effect. The synergetic effect was attributed to the highly efficient cooperation among the three components of Ti O2-Graphite/Mg O.