Design And Preparation Of A Ternary Photocatalyst TiO₂-Ca（OH）₂-Graphite For Efficient Treatment Of Dye Wastewater Under Sunlight

Binary composites Ti O2-Ca(OH)2, Ti O2-Ca O and Ti O2-Ca Fe2O4 were first prepared by sol-gel method. Both the adsorptive and the photocatalytic performances of them were checked by the removal of alizarin red S in water, but only Ti O2-Ca(OH)2 has a good effect. Whereafter a ternary photocatalyst Ti O2-Ca(OH)2-Graphite was fabricated by grinding the mixture of Ti O2-Ca(OH)2 and graphite.The ternary photocatalyst Ti O2-Ca(OH)2-Graphite was prepared by a facile chemical(preparing binary composite Ti O2-Ca(OH)2 by sol–gel method) and physical(grinding mixture of Ti O2-Ca(OH)2 and graphite) method. In Ti O2-Ca(OH)2-Graphite, Ca(OH)2 was used for improving the adsorptive capacity of Ti O2-Ca(OH)2-Graphite and graphite was used for enhancing its separation property of charge photogenerated in Ti O2. By the collaboration among three components of Ti O2-Ca(OH)2-Graphite with a mass ratio of 1:0.02:0.006, a remarkable synergetic effect was created.The characterization of as-prepared samples by XRD, SEM, TEM, UV–vis diffuse reflection spectra and photoluminescence emission spectroscopy demonstrated that only the anatase phase Ti O2 was present in the photocatalyst. Clumps of graphite were split into numerous flakes of hundreds nm size by grinding with Ti O2-Ca(OH)2 and the flakes were well dispersed in Ti O2-Ca(OH)2-Graphite. The photocatalytic activity of Ti O2-Ca(OH)2-Graphite was evaluated by the photocatalytic oxidation of alizarin red S dye under sunlight. The experimental results showed that the residual normalized concentrations of alizarin red S dye were 0.412, 0.309, 0.259 and 0.208 in the systems containing pure Ti O2, binary composite Ti O2-Ca(OH)2 with a mass ratio of 1:0.02, binary composite Ti O2-Graphite with a mass ratio of 1:0.006 and the mixture Ti O2-Ca(OH)2 + graphite, respectively. However, the concentration decreased to 0.004 in the system containing Ti O2-Ca(OH)2-Graphite with a mass ratio of 1:0.02:0.006, there was a remarkable synergetic effect.We expected the present work could give a new idea and propose a convenient way to prepare the Ti O2-based composite photocatalysts.