Eco-friendly natural Moroccan clay as a high-performance adsorbent for methylene blue removal: integrated...

This study aims to explore the potential of natural Moroccan clay (NMC) as a cost-effective and sustainable adsorbent for removing methylene blue from aqueous solutions, addressing the global challenge of water pollution through an innovative integration of experimental and theoretical approaches. By combining advanced characterization techniques and computational modeling, the study offers novel insights into the adsorption mechanisms of NMC. Characterization of NMC using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, X-ray fluorescence, and point-of-zero charge determination revealed a predominant montmorillonite composition with significant amounts of silica (61.33%) and alumina (13.33%). Adsorption experiments were conducted using varying parameters such as solid/liquid ratio, initial dye concentration, and contact time to identify suitable conditions for maximum adsorption capacity. The maximum adsorption capacity reached 315.05 mg/g under the tested conditions. Kinetic studies demonstrated that the adsorption follows kinetics best described by the Elovich and intra-particle diffusion models, indicating chemisorption on heterogeneous surfaces coupled with intra-particle mass transfer limitations. Isotherm analysis showed the best fit with the Langmuir model (R² = 0.9971), suggesting monolayer adsorption. Thermodynamic parameters (ΔG°, ΔH°, and ΔS°) confirmed the spontaneous and endothermic nature of the process. Density functional theory calculations provided insights into methylene blue's electronic properties and reactivity, with a HOMO-LUMO energy gap of 0.35 eV indicating a favorable interaction potential. Monte Carlo simulations revealed strong adsorption energies ranging from - 123.24 to - 133.01 kJ/mol, confirming the stability of MB-NMC interactions. This comprehensive study establishes NMC as a promising, eco-friendly solution for wastewater treatment, providing a detailed mechanistic understanding of its adsorption performance.