Dithiocarbamate‐Functionalized Chitosan/Polyacrylamide Hybrid Hydrogels for Heavy Metal Adsorption and Antibacterial Activity

ABSTRACT

Hydrogel‐based adsorbents have attracted considerable attention for heavy metal removal; however, improving adsorption efficiency while imparting antibacterial functionality remains challenging. To address this issue, we incorporated dithiocarbamate‐modified chitosan (DTCChi) into a polyacrylamide (PAAm) hydrogel to develop an environmentally friendly hybrid hydrogel and its silver nanocomposite counterpart. We characterized the PAAm/DTCChi hydrogel using Fourier‐transform infrared spectroscopy (FT‐IR), scanning electron microscopy (SEM), energy‐dispersive x‐ray spectroscopy (EDX), and elemental analysis. Elemental analysis showed a sulfur content of 4.44% in DTCChi, supporting successful dithiocarbamate functionalization. The hydrogel removed Pb(II) and Ag(I) ions from aqueous solutions, and we investigated the effects of pH, contact time, initial ion concentration, and temperature. The maximum adsorption capacities were 69.15 ± 2.41 mg/g for Pb(II) and 40.00 ± 2.45 mg/g for Ag(I) at pH 5.5 after 120 min. Kinetic data followed the pseudo‐second‐order model, while equilibrium data fit the Freundlich isotherm. Thermodynamic analysis indicated spontaneous and endothermic adsorption. The silver nanocomposite hydrogel exhibited strong antibacterial activity against Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ), with minimum inhibitory concentration (MIC ₅ ₀) values of 31.62 and 7.62 µg Ag/mL, respectively. These findings demonstrate a multifunctional hydrogel platform combining heavy metal removal and antibacterial activity for sustainable wastewater treatment and related environmental applications.