Synthesis and characterization of Walnut shell/diopside nanocomposite for removal of Congo red dye: Experimental design and optimization

Recently, removal of different dyes from industrial effluents has got a judgmental subject [1]. Congo red (CR) is pretty toxic agent in terms of its resistance to heat, chemical reagent, and capability of producing cancer and mutagens owing to existence of different reactive center and charge nature [2].In this research, Walnut shell/diopside nanocomposite were made and used for removal of CR from aqueous solution. The nanocomposites were characterized by FTIR, XRD, and FE-SEM. Also, the surface area, the pore volume and the pore size distribution of the Walnut shell/diopside nanocomposite were calculated by BET technique. Effects of adsorbent dose, initial pH, contact time and the initial dye concentration on CR removal were studied by central composite design (CCD) and the optimized condition obtained at adsorbent dose=0.00875, pH= 4.5, Contact time= 15 min, and initial dye concentration= 65 ppm.The maximum adsorption capacities (Qm) calculated by best fitting model (Langmuir) were 333.33 mg/g at 313 K. Also, the adsorption kinetic was well confirmed with pseudo-second-order equation.Removal of CR by Walnut shell/diopside nanocomposite is shown in Fig. 1.