Efficient catalytic degradation of single and binary azo dyes by a novel triple nanocomposite of Mn3O4/Ag/SiO2

The strategy of structurally integrating noble metal and metal oxides is expected to offer exceptional opportunities toward emerging functions of all. We report the creation of an efficient hetero-structured nanocatalyst consisting of Mn3O4 core, SiO2 shell impregnated with noble Ag nanoparticles. The triple nanocatalyst Mn3O4/Ag/SiO2 was synthesized by using a facile three-step approach to disperse Ag nanoparticles between the surfaces of functionalized Mn3O4 and SiO2. The physicochemical structural characterization was performed by XRD and FTIR. The surface morphologies were observed by SEM and TEM. The EDX measurements confirmed the composition of the composite. The nanocomposite has been used as a catalyst for the degradation of Direct blue 78 in the presence of sodium borohydride (NaBH4). It has a drastic catalytic effect as compared to Mn3O4/Ag and Mn3O4. The rate constant of Direct blue 78 reduction followed the order: Mn3O4/Ag/SiO2 (0.25166 min(-1)) > Mn3O4/Ag (0.07971 min(-1)) > Mn3O4 (0.00947 min(-1)). The effects of different reaction conditions of the catalytic reaction have been determined. The catalytic activity of the as- synthesized nanocomposite was examined for the binary dyes system by incorporation of an additional dye (Sunset yellow). Its influence on the degradation rate and efficiency of Direct blue 78 was investigated. The nanocatalyst exhibited excellent catalytic activity towards the complete degradation of both the Direct blue 78 and Sunset yellow. The degradation percentage for these dyes reached 99.33 and 94.68%, respectively. The recovery and reusability of the Mn3O4/Ag/SiO2 nanocomposite was studied in the reduction reaction of Direct blue 78. Five consecutive recovery reaction cycles were performed. They revealed high stability and constant efficiency of the catalyst for four cycles.