Gamma-irradiated chitosan-HPMC/Ulva lactuca based hydrogel for heavy metal remediation from aqueous solutions

Abstract

This study focuses on the novel bio-composite hydrogel made from chitosan (CS), hydroxypropyl methylcellulose (HPMC), polyacrylamide (PAAm), and green algae Ulva lactuca (Ul), which is synthesized to effectively remove Cu(II) and Co(II) ions from simulated aqueous solutions using gamma irradiation. The hydrogels, whether or not they had Ulva lactuca, were labeled CS/HPMC/PAAm and CS/HPMC/PAAm/Ul. The process was tested by changing the acrylamide concentration, the dose of gamma irradiation, and adding Ulva. Analyzing the Ulva with BET and EDX helped prove that its addition to the hydrogel increases surface area, porosity, tolerance to heat, and roughness of the surface. In both metal systems, the hydrogel strongly favored Co(II) over Fe(II). Kinetic analysis favored the pseudo-second-order (PSO) model, indicating chemisorption as the rate-controlling step. The Jovanovic and Redlich–Peterson isotherm models provided the best fit to the experimental data. The results suggested that the adsorption process involves a combination of physical and chemical interactions. Reusability tests over five cycles confirmed the hydrogel's durability and regeneration potential. The CS/HPMC/PAAm/Ul hydrogel is an eco-friendly and efficient sorbent, making it a strong candidate for heavy metal remediation in environmental applications. © 2025 Elsevier B.V.