Floatable clay-alginate beads for water treatment: Experimental and molecular modeling approaches to Pb(II) and...

In this study, we created a multifunctional adsorbent, F-(clay/alg@Fe-Ni), by modifying natural clay with alginate. The ionic gelation of alginate using Ca²⁺ ions was followed by the introduction of (FeNi) nanoparticles through the chemical reduction of the resulting gel. The prepared adsorbent was then characterized and utilized for the uptake of Pb²⁺ and malachite green (MG) from water. XRD revealed changes in peak intensities and interlayer spacing, indicating interactions between the clay and alginate. Additionally, FTIR analysis demonstrated the existence of various functions on the composite surface, such as -OH and -COO- groups. Furthermore, (pH_ZPC), (TGA/DTG), and (SEM) analyses validated the modifications made to the clay surface. The development of additional adsorption sites and functional groups based on F-(clay/alg@Fe-Ni) significantly improved the adsorption performance of Pb²⁺ and malachite green (MG) compared to natural clay. The best-fitting results were obtained using the pseudo-second-order and Langmuir adsorption models, with a maximum adsorption capacity of 189.08 mg/g for Pb²⁺ and 365.31 mg/g for MG. According to the calculated thermodynamic factors, the adsorption can be defined as physical and endothermic. DFT simulations were used to evaluate the electronic parameters influencing the adsorption of Pb²⁺ ions and Malachite Green (MG) dye on clay surfaces. Advanced topological analyses, including LOL, ELF, VMD, and RDG, were performed in the liquid phase using Multiwfn. Monte Carlo simulations provided insights into molecular interactions, highlighting the role of electrostatic forces and hydrogen bonding in enhancing adsorption efficiency. Theoretical studies confirmed the high reactivity of MG cations, facilitating strong adsorption. Monte Carlo searches identified optimal adsorption configurations on unmodified and modified kaolinite and clinochlore surfaces, revealing that Alg@Fe-Ni significantly improved adsorption, particularly on the (100) surface. Hirshfeld surface analysis further validated the predominant adsorption mechanisms. Overall, integrating clay, alginate, and FeNi nanoparticles resulted in an efficient and cost-effective method for heavy metals and dyes removal, overcoming solid/liquid separation challenges.