Photocatalytic Degradation of Methylene Blue in Aqueous Solution with Silver-Kaolinite-Titania Nanocomposite under Visible Light Irradiation

A photocatalyst, silver-kaolinite-titanium dioxide (Ag-K-T) composite, with less toxicity and cheaper in price was synthesized and studied under visible light source for degradation of a standard textile dye, Methylene Blue (MB). The catalyst was synthesized by mixing, pounding, pressurizing, grinding and calcining of Ag(I) nitrate with kaolinite and then with TiO2 under certain specific environment and conditions. The characterization of the composite catalyst was done with XRD, FT-IR, SEM, EDX, TEM, AFM, TGA, CEC, BET, UV-DRS and PL analyses. The photocatalytic degradation of aqueous methylene blue on the prepared material was investigated with process parameter variations such as catalyst loading, input dye concentration, pH of the medium and reaction time. The prepared Ag-K-T composite material had large surface area, considerably high cation exchange capacity (CEC) and fine porous nature. The aqueous dye solution (5x10-6M) was almost 100% degradable under experimental conditions of 0.5 g L-1 catalyst loading, 70 min reaction time and 7.5 pH. The photocatalyst was easily separable from the reaction mixture, could be regenerated and recycled successfully up to three cycles with decrease of 1.68% of degradation rate. The work shows the potential for Ag-K-T photocatalyst to be used as a multifunctional material particularly with respect to decolourisation of wastewater containing dyes and pigments.