Bridging scales in wastewater treatment: Moroccan clays as eco-friendly adsorbents explored by experiments, response surface methodology, and Monte Carlo simulations

Abstract

This work investigates the adsorptive performance of natural clayey materials from the Nador region (Morocco) for the removal of dye pollutants from aqueous solutions. The study focused on the removal of methylene blue from aqueous solutions, combining experimental characterization, statistical optimization, and molecular modeling to provide a comprehensive understanding of the adsorption process. Detailed microstructural analyses, including XRF, XRD, FTIR, SEM, and complementary physicochemical tests, revealed the structural and compositional features that govern adsorption behavior. Adsorption performance was strongly influenced by the solid-to-liquid ratio, initial dye concentration, and contact time, with equilibrium reached within 20 min. Kinetic modeling revealed that the pseudo-second-order model provided the best description of the adsorption process. At the same time, isotherm studies confirmed the Langmuir model as the most suitable, indicating monolayer adsorption on homogeneous active sites. To optimize operational conditions, a Box–Behnken design integrated with response surface methodology was applied. At the molecular level, Monte Carlo simulations combined with simulated annealing provided valuable insights into dye-surface interactions, demonstrating spontaneous, exothermic adsorption and stronger MB affinity for bentonitic and kaolinitic clays than for illitic clay. Overall, integrating experimental, statistical, and computational approaches establishes a multiscale understanding of adsorption mechanisms. The findings highlight the high efficiency, low cost, and sustainability of Moroccan clays, confirming their potential as promising raw materials for advanced environmental applications, particularly in the development of eco-friendly microfiltration membranes for wastewater treatment.