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

Silver-kaolinite-titanium dioxide (Ag-K-T) composite was synthesized and studied as a photocatalyst under visible light irradiation for degradation of the standard dye, Methylene Blue (MB). The catalyst was synthesized by mixing, pounding, pressurizing, grinding and calcining of Ag(I) nitrate with kaolinite and then combined 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 was studied with process parameter variations such as catalyst loading, input dye concentration, pH of the medium and reaction time. The Ag-K-T composite had high cation exchange capacity (CEC) with large surface area and porosity. The aqueous dye (5x10-6 M) was found to be 100% degradable with a catalyst loading of 0.5 g L-1, reaction time of 70 min and at pH 7.5. The kinetics of dye degradation was also studied to find out the effectiveness of the photocatalyst. Chemical Oxygen Demand (COD) analysis of the aqueous dye solution before and after reaction confirmed degradation of the dye which was also observed through decolourisation. The photocatalyst was easily separable from the reaction mixture, could be regenerated and recycled successfully up to three cycles with decrease of only 1.68% of degradation rate. The work shows the potential of Ag-K-T photocatalyst to be used as a multifunctional material particularly with respect to decolourisation of wastewater containing dyes and pigments.