Insight on the Natural Moroccan Clay Valorization for Malachite Green Adsorption: Kinetic and Isotherm Studies

Abstract. This work investigates the potential of Natural Moroccan Clay (NMC) sourced from the Draa-Tafilalet region for removing malachite green from aqueous media through adsorption. X-ray diffraction (XRD) and scanning electron microscopy combined with energy-dispersive X-ray microanalysis (SEM/EDX) were used to characterize the clay. Malachite green (MG) was subjected to batch adsorption experiments, and a kinetic study was carried out at three concentrations (5, 50, and 100 mg/L). The results showed that adsorption is typically fast for all three concentrations and that the adsorbed amount rises with time and dye concentration. Equilibrium is reached within just 40 minutes. The kinetics adsorption at varying MG concentrations were modeled using non-linear and linear forms of pseudo-first order and pseudo-second order and with intraparticle diffusion models. The non-linear form of the pseudo-second-order model was found to be best suited to describing this adsorption process. The isotherm was studied using two models: Freundlich and Langmuir. According to the error functions analysis, the Langmuir model is well suited for equilibrium data fitting. Investigated clay attained an adsorption capacity of 214 mg/g. SEM/EDX characterization of NMC before and after adsorption confirms the malachite green adsorption on the NMC surface. These results illustrate the effectiveness of the investigated clay as a cost-effective adsorbent.