Anugrah Ricky Wijaya, Rahadian Zainul, Karna Wijaya, Niko Prasetyo, Nur Abdillah Siddiq
A novel class of bead adsorbents derived from waste Acropora coral skeletons, functionalized with various monomers including alginate, graphene oxide (GO), polyvinyl alcohol (PVA), chitosan, cellulose, natural silica, and pure silica, was synthesized, characterized, and evaluated for the adsorption of Pb(II) ions from aqueous solutions. The characterization techniques, including colorimetric analysis and FTIR spectroscopy, revealed characteristic absorption bands at 712.58, 1186, 825, 1470, 3562, 1660, and 1050 cm⁻¹, corresponding to functional groups introduced through modification of the coral skeleton using Ca²⁺ ions as a source. Among the synthesized beads, Ca-Alg-GO, Ca-Alg-PVA, Ca-Alg-Chitosan, and Ca-Alg-Pure SiO₂ exhibited a maximum adsorption capacity of 0.063 mg/g under optimized conditions namely, a contact time of 30 min and an initial Pb(II) concentration of 2 mg/L in batch systems. Kinetic analysis indicated that the adsorption data best fit the pseudo-second-order model (R²≈0.99), suggesting that chemisorption via valence forces involving sharing or exchange of electrons dominates the process. Additionally, the Freundlich isotherm provided a superior fit compared to the Langmuir model for Ca-Alg-PVA, Ca-Alg-GO, Ca-Alg-Celulose, and Ca-Alg-Chitosan beads, with R² values of 0.991, 0.998, 0.997, and 0.984, respectively. These results imply that multilayer adsorption occurs on heterogeneous surfaces. The positive ΔH values confirm that Pb(II) adsorption on these bead adsorbents is endothermic, reflecting strong interactions between Pb(II) ions and negatively charged sites on the bead surfaces. © 2025 The Author(s)
Department of Chemistry, Faculty of Sciences and Mathematics, Universitas Negeri Malang (UM) or State University of Malang, Semarang 5 Malang, 65145, Indonesia; Department of Chemistry, Faculty of Mathematics and Sciences Education, Universitas Negeri Padang, Jalan Prof. Dr. Hamka, Air Tawar Padang, Sumatera Barat, 25173, Indonesia; Department of Chemistry, Faculty of Sciences and Mathematics, Universitas Gadjah Mada, Sekip Utara BLS 21 Depok, Yogyakarta, Sleman, 55281, Indonesia; Department of Nuclear Engineering and Engineering Physics, Faculty of Engineering, Universitas Gadjah Mada, Jl. Grafika Bulaksumur, Yogyakarta, Sleman, 55281, Indonesia
