Study of heavy metals adsorption using a silicate-based material: Experiments and theoretical insights

• MgOSiO 2 nH 2 O demonstrates potential as an eco-friendly adsorbent for heavy metal removal from wastewater. • Synthetic MgOSiO 2 nH 2 O shows good adsorption capacity for Cu 2+ , Zn 2+ , Co 2+ , and Mn 2+ ions. • Kinetic studies indicate both chemical and physical adsorption mechanisms for most metal ions. • Theoretical calculations reveal energetically favorable adsorption of metal ions on Mg 2 O 8 Si 3 surface. Heavy metal toxicity in water is a serious problem with harmful effects on human health and the ecosystem. This research studied a silicate-based material as an adsorbent for removing four heavy metals from aqueous solutions. The target metal pollutants selected include manganese (Mn 2+ ), copper (Cu 2+ ), cobalt (Co 2+ ), and zinc (Zn 2+ ). First, theoretical tools including potential energy surface analysis, Natural Population Analysis, AIM, Wiberg Bond Index, QTAIM, and topological methods offer profound insights into the nature of interactions present in the Mg 2 O 8 Si 3 M (M = Mn 2+ , Cu 2+ , Co 2+ , Zn 2+ ) clusters. Second, the synthesis and characterization of eco-friendly hydrated amorphous magnesium silicate (MgOSiO 2 nH 2 O) was developed. Last, a simple kinetic adsorption test was applied to assess the material selectivity towards heavy metals and support theoretical results. The kinetic adsorption study was analyzed through the pseudo-first and second-order kinetics, Elovich, and the intraparticle diffusion models. The theoretical analysis of the adsorption energies indicates that the adsorption of four metal ions on the Mg 2 O 8 Si 3 surface is energetically favorable in all cases. The material displayed the following adsorption sequence: Cu 2+ (59 mg g -1 ) > Zn 2+ (25 mg g -1 ) ≈ Co 2+ (23 mg g -1 ) > Mn 2+ (15 mg g -1 ). This knowledge can then be used to design and optimize low-cost silicate-based materials for effective heavy metal removal, contributing to efforts to address environmental pollution and protect public health.