Comprehensive Investigation of Cu2+ Adsorption from Wastewater Using Olive-Waste-Derived Adsorbents: Experimental and Molecular Insights

Abstract

This study investigates the efficacy of adsorbents from locally sourced olive waste—encompassing olive skins, leaves, and pits, recovered from the initial centrifugation of olives (OWP)—and a composite with sodium alginate (OWPSA) for the removal of Cu2+ ions from synthetic wastewater. Experimental analyses conducted at room temperature, with an initial Cu2+ concentration of 50 mg/L and a solid/liquid ratio of 1 g/L, showed that the removal efficiencies were approximately 79.54% and 94.54% for OWP and OWPSA, respectively, highlighting the positive impact of alginate on adsorption capacity. Utilizing statistical physics isotherm models, particularly the single-layer model coupled to real gas (SLMRG), allowed us to robustly fit the experimental data, providing insights into the adsorption mechanisms. Thermodynamic parameters affirmed the spontaneity and endothermic nature of the processes. Adsorption kinetics were interpreted effectively using the pseudo-second-order (PSO) model. Molecular modeling investigations, including the conductor-like screening model for real solvents (COSMO-RS), density functional theory (DFT), and atom-in-molecule (AIM) analysis, unveiled intricate molecular interactions among the adsorbent components—cellulose, hemicellulose, lignin, and alginate—and the pollutant Cu2+, confirming their physically interactive nature. These findings emphasize the synergistic application of experimental and theoretical approaches, providing a comprehensive understanding of copper adsorption dynamics at the molecular level. This methodology holds promise for unraveling intricate processes across various adsorbent materials in wastewater treatment applications.

Exploring the Efficiency of Algerian Kaolinite Clay in the Adsorption of Cr(III) from Aqueous Solutions: Experimental and Computational Insights

“…The analysis not only underscores the diversity in bond strength, as indicated by the electron density and Laplacian values at bond critical points (BCPs), but also delineates the character of these interactions, such as hydrogen bonding and van der Waals forces. For example, BCP 252 in the Al-O(H) layer reveals a significant interaction between Cr(OH) 3 and kaolinite, characterized by its electron density value, indicative of a potential hydrogen bond crucial for adsorption [16]. This nuanced understanding of molecular interactions obtained from QTAIM metrics provides a robust framework for designing optimized kaolinite-based adsorbents for environmental applications, particularly for the removal of chromium pollutants from water.…”

“…The frontier orbitals, namely the HOMO and the LUMO orbitals, were critically assessed (refer to Figure 17). These orbitals are quintessential to predicting the chemical reactivity and interaction dynamics of the adsorbate-adsorbent pairs, as they define the pathways for electronic transitions essential in adsorption phenomena [16,55]. Figure 16 demonstrates that the Al-O(H) layer exhibited a band gap of 2.037 eV, suggesting a higher resistance to electron transition compared to the Si-O layer's band gap of 1.338 eV.…”

“…The effectiveness of adsorption largely depends on the choice and preparation of cost-effective and eco-friendly adsorbents [13,14]. Alternatives like chitosan, alginate-based materials, and various plant wastes have been investigated for their adsorptive properties, despite some limitations like pH dependence or limited affinity for certain dyes [15,16]. Researchers like Rouibah et al [17,18] and Thabede et al [19] have utilized plant-based adsorbents for effective heavy metal removal, demonstrating the potential of these sustainable materials in water purification processes [20].…”