Synthesis and Characterization of Crosslinked Polyacrylamide-Soybean Copolymer for Lead (II) Ion Removal from Aqueous Solutions

Tan, Wen Xin (2026) Synthesis and Characterization of Crosslinked Polyacrylamide-Soybean Copolymer for Lead (II) Ion Removal from Aqueous Solutions. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

Crosslinking is a process that interconnects polymer chains into a stable three-dimensional network, enhancing their mechanical strength, stability, and adsorption performance. In this study, soybean waste pretreated with alkali was employed as a biomass precursor, grafted with acrylamide via free radical polymerization, and subsequently crosslinked using glutaraldehyde. The resulting glutaraldehyde-crosslinked polyacrylamide–soybean graft copolymer, was successfully synthesized at optimum reaction conditions of 30 °C, 8% (w/v) glutaraldehyde, and 4 hours reaction time. The synthesized crosslinked copolymer was characterized using Fourier-transform infrared spectroscopy (FTIR), CHNS elemental analysis, thermogravimetric analysis (TGA), and zeta potential measurement. Batch adsorption studies were conducted under optimized parameters, including adsorbent dosage, pH, contact time and initial Pb(II) concentration. Adsorption kinetics and isotherm analysis showed that Pb(II) uptake followed a pseudo-second-order model and fitted the Freundlich isotherm, suggesting chemisorption on a heterogeneous surface. The slightly positive zeta potential across the pH range confirmed chelation between Pb(II) ions and imine bonds (C=N) on the crosslinked copolymer. Reusability tests showed that the crosslinked copolymer retained over 98% Pb(II) removal efficiency for at least three adsorption–desorption cycles, with NaOH performing better than HCl as a regenerating agent. These findings demonstrate that the glutaraldehyde-crosslinked PAM–soybean copolymer is a cost-effective, reusable, and sustainable adsorbent for Pb(II) removal in water treatment.