Carboxyethyl chitosan/oxidized sodium alginate composite hydrogel loaded with AgNPs and Zn²⁺: dye adsorption and...

This research investigates the crosslinking of carboxyethyl chitosan (CEC) with oxidized sodium alginate (OSA), subsequently facilitating the rapid reduction of silver ions to form silver nanoparticles (AgNPs) through a silver mirror reaction, employing varying concentrations of silver ammonia solution. The resulting hydrogels were then immersed in zinc chloride solutions at different concentrations to further improve their properties. Structural analysis revealed the formation of stable imine bonds between the amino and aldehyde groups, alongside the coordination of the carboxyl group with zinc ions. Scanning electron microscopy, texture profile analysis, and rheological tests revealed that the introduction of AgNPs contributed to a denser hydrogel network and increased hardness. Moreover, the incorporation of zinc ions significantly enhanced the mechanical properties, resulting in a 7.44-fold increase in the hydrogel's hardness relative to its original form. The hydrogel's antibacterial performance was evaluated against Escherichia coli and Staphylococcus aureus, showing notable inhibitory effects. The inhibition zone diameters for both bacterial strains exhibited an approximate 2.5-fold increase, indicating enhanced antimicrobial activity. Additionally, the adsorption capacity of the CEC/OSA/Ag¹/Zn³ hydrogels for dyes was examined, with methylene blue and Congo red uptakes recorded at 157.23 mg/g and 79.15 mg/g, respectively. This study offers a promising and sustainable approach to tackle the challenges of dye wastewater treatment.