Calcium Alginate/Laponite Nanocomposite Hydrogels: Synthesis, Swelling, and Sorption Properties

This study presents the synthesis, characterization, and evaluation of hybrid hydrogels based on calcium alginate (Ca-Alg) and synthetic nanoclay LaponiteRD (Lap), with an emphasis on their swelling and sorption properties. The motivation behind the development of these hybrid hydrogels stems from the need for sustainable materials with enhanced mechanical strength, swelling properties, and sorption capacity for environmental remediation and controlled-release applications. Synthesis methods for the ionotropically cross-linked Ca-Alg hydrogel and Alg–Lap composite hydrogels, based on Alg and Lap in the form of granules and fibres, have been developed. The Fourier-transform infrared spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) analyses of composite hydrogels confirmed the successful incorporation of Lap into the Ca-Alg matrix, indicating strong interactions between the polymer and clay, which enhanced the structural integrity of the hydrogels. The morphology of the surface and pore structure of nanocomposites were studied using Scanning Electron Microscopy (SEM). The swelling behaviour of the nanocomposites was largely dependent on the concentrations of Lap and the cross-linking agent (CaCl2), with higher concentrations leading to more rigid, less swellable structures due to the increased cross-linking density. The sorption studies, specifically with Fe(II) ions, demonstrated that the hybrid hydrogels possess a large sorption capacity, with Lap contributing to selective sorption at lower Fe(II) ion concentrations and Alg enhancing overall capacity at higher concentrations. This suggests that the synergistic interaction between Alg and Lap not only improves mechanical stability but also tailors the sorption properties of the hydrogels. These findings position the Alg-Lap hydrogels as promising materials for a range of environmental applications, including wastewater treatment, heavy metal ion removal, and the design of advanced filtration systems. The study’s insights into the tunability of these hydrogels pave the way for further research into their use in diverse fields such as biomedicine, agriculture, and industrial water management.