Optimization study of the adsorption of malachite green removal by MgO nano-composite, nano-bentonite and fungal immobilization on active carbon using response surface methodology and kinetic study

Abstract

Malachite green a typical organic dye containing triarylmethane, is discharged in wastewater by textile and leather manufacturing plants. MG can pollute the environment, and it represents a major hazard to humans and various living organisms. We have thus worked toward developing the optimum dye-absorptive material, which should possess the following characteristics: excellent adsorption capacity, good selectivity, favorable recycling and reuse potential, and ease and quickness of adsorption. In this study, nano-bentonite, novel hybrid MgO-impregnated clay, and fungal composites were synthesized for Malachite green removal from aqueous solution. Response surface methodology (RSM) was used for the optimization of the synthesis of adsorbents to achieve simultaneous maximum malachite green removal. The composites were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). According to the obtained results, MgO-impregnated clay exhibits a exhibited a higher adsorption capacity of MG than nano-bentonite and pure bentonite. The malachite green adsorption isotherm on MgO-impregnated clay corresponded with the Freundlich isotherm. However, the Langmuir adsorption isotherm was a superior fit for nano-bentonite. The adsorption activities of nano-bentonite and MgO-impregnated clay were fitted into a pseudo-second-order kinetic model. Based on the root-mean-square error, bias, and accuracy, statistical research has shown that the Halden model has optimal accuracy. In addition, despite being recycled numerous times, the adsorbent maintained its high structural stability and removal effectiveness for nano-bentonite (94.5–86%) and MgO-impregnated clay (92–83%).