Green synthesis of Ag-Cr-AC nanocomposites by Azadirachta indica and its application for the simultaneous removal of binary mixture of dyes by ultrasonicated assisted adsorption process using Response Surface Methodology.

In the present studies the Ag-Cr-AC nanocomposites were synthesized by Azadirachta indica leaves extract. They were inoculated on the amorphous surface of activated carbon. The surface morphology and structural identification was determined by SEM, FTIR and XRD techniques. The simultaneous removal of binary dye system of Reactive Red and Crystal Violet were performed by ultrasonicated assisted adsorption process utilizing Ag-Cr-AC nanocomposites. Central Composite Design (CCD) having 5 factors of time, pH, amount of Ag-Cr-AC (adsorbent), concentrations of Reactive Red (RR) and Crystal Violet (CV) was employed. Response Surface Methodology was applied to study the Optimum Operating Parameters (OOP) for the adsorption process. The current studies showed that they can be efficiently employed to remove the coloured effluent from aqueous media as the simultaneous removal of dyes was observed to be 64.92% and 82.47% for RR and CV dyes respectively. Adsorption equilibrium was studied by Freundlich, Langmuir, Dubinin-Radushkevich, Temkin and Harkins-Jura Isotherm Models. The Langmuir isotherm was observed to be followed by the RR-Ag-Cr-AC system while CV-Ag-Cr-AC followed Harkins-Jura Isotherm model. For the binary system, the removal of CV and RR dyes by the nanocomposites obeyed Harkins-Jura model at temperature of 40°C. Thermodynamics studies affirmed the spontaneous nature of adsorption process. pHpzc was evaluated to be 6.29. The purification cost per cubic meter of the effluent was evaluated to be US$ 85.08. The proposed method might prove to be an efficient and cost effective way to eradicate color from the binary mixture of RR and CV dyes.