Tailored alginate nanocomposite beads for efficient heavy metals sequestration from industrial wastewater
Eman Sanad, Ahmed M. Elgarahy, Khalid Z. Elwakeel, Asmaa S. Morshedy, Noha M. Mashaal, Mokhtar S. Beheary, Ahmed Abdelaal
Abstract
Heavy metal contamination in industrial effluents poses a significant environmental threat. Adsorption offers a promising, environmentally friendly approach to effluent decontamination due to its simplicity and cost-effectiveness. This study explores the synthesis, characterisation, and application of engineered alginate nanocomposite beads for the removal of heavy metal ions from industrial wastewater. Composite beads incorporating zinc sulphide (ZnS), zinc oxide (ZnO), titanium(III) oxide (Ti2O3), and gum Arabic (GA) were developed using sodium alginate as a biopolymeric base. Comprehensive characterisation using FTIR, SEM, and zeta potential analyses revealed structural features and surface properties enhancing heavy metal adsorption. Adsorption experiments targeted Cd(II), Pb(II), and Ni(II), and the results showed significant variations in adsorption capacities: Alg\ZnS\ZnO beads achieved 2.11, 1.79, and 1.94 mmol g−1 for Cd(II), Pb(II), and Ni(II), respectively; Alg\ZnS\ZnO\Ti2O3 beads exhibited capacities of 3.50, 2.36, and 2.49 mmol g−1, while Alg\ZnS\ZnO\GA beads recorded 1.47, 1.25, and 1.39 mmol g−1 for the same ions at pH 6, 25°C. Kinetic and isotherm models were employed to elucidate the adsorption mechanisms. Kinetic studies confirmed pseudo-second-order behaviour, indicating chemisorption as the primary mechanism, while isothermal studies demonstrated monolayer adsorption. Practical application tests with industrial effluents highlighted the beads’ high efficacy, removing up to 99.8% of heavy metals. Furthermore, reusability assessments showed minimal performance loss over five cycles, affirming the materials’ economic and environmental viability. A reusability study was also conducted. The regeneration study demonstrated the reusability of the prepared beads after multiple treatments with 0.5 M HNO3 solution. These findings underscore the potential of alginate-based nanocomposites as sustainable, cost-effective solutions for heavy metal remediation, with promising implications for industrial water treatment applications.