Remediation of cationic dye from aqueous solution through adsorption utilizing natural Haloxylon salicornicum: An integrated experimental, physical statistics and molecular modeling investigation

Abstract

Wastewater emanating from declining industrial processes often presents a vexing challenge due to its intricate composition replete with hazardous chemicals. The quest for environmentally sustainable methods to remediate such wastewater has led to the exploration of biomaterials as adsorbents and co-substrates within diverse treatment systems. In this study, we harnessed the abundant and cost-effective adsorbent, Haloxylon salicornicum (HS), as a potent agent for the removal of the pernicious triphenylmethane dye, crystal violet, from aqueous mediums. The adsorbent was characterised using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM), while Brunauer-Emmett-Teller (BET) analysis yielded a specific surface area (SBET) of 85.23 m2 g−1, highlighting its advantageous mesoporous structure for adsorption. Comprehensive investigations were conducted across various operational parameters, encompassing initial dye concentration, contact time, HS adsorbent dosage, initial pH, and temperature, with a keen focus on their influence on dye removal efficiency. The results unveiled several key trends, demonstrating that elevated initial dye concentration, prolonged contact time, and higher initial pH levels substantially enhanced the efficiency of dye removal, while ionic strength and temperature exhibited comparatively modest impacts. The kinetics of dye adsorption were rigorously examined, revealing a closer adherence to the pseudo-second-order model in comparison to the PFO model, thereby offering deeper insights into the adsorption dynamics. To further unravel the intricate mechanism underpinning the adsorption of CV on HS, we employed a single-layer model linked to SLMRG. In conjunction, DFT calculations, encompassing COSMO-RS, NCI, Molecular Dynamics (MD) simulations and QTAIM calculations, were applied to probe the interactions between adsorbed CV and the adsorbent-molecules, providing compelling evidence of robust binding interactions. These theoretical insights were subsequently aligned with empirical observations, affirming a significant relation between the theoretical and experimental data. This multifaceted study not only advances our understanding of CV removal using HS but also underscores the robustness of this adsorbent within the context of wastewater treatment. Furthermore, it demonstrates the synergy of empirical investigations and theoretical modeling in unraveling the intricacies of adsorption processes.