Cationic chitosan/silsesquioxane hybrid cryogel with antibacterial activity for efficient removal of Cr (VI)

The hazards of aqueous Cr (VI) are severe, necessitating adsorbents with high capacity, applicability, and recyclability. In this study, a novel water-soluble cationic quaternary ammonium silsesquioxane (SQ-N) was synthesized and subsequently reacted with chitosan (CS), polyethylene glycol diacrylate (PEGDA), and pentaerythritol tetrakis (3-mercaptopropionate) (PETMP) to fabricate a flexible chitosan hybrid cryogel (PPSC-x (x = 1, 2, 3)) through UV cross-linking followed by freeze-drying. The resulting cryogel was comprehensively characterized using FTIR, XRD, TGA, SEM, EDS, and XPS analyses. The PPSC-x (x = 1, 2, 3) cryogel possessed abundant active sites and superior mechanical properties, rendering them suitable for the efficient removal of Cr (VI) from wastewater. The adsorption process was spontaneous and endothermic, achieving a maximum equilibrium adsorption capacity of 274 mg g^-1 at 328 K. The adsorption of Cr (VI) followed a pseudo-second-order kinetic model and conformed to the Langmuir isotherm. PPSC-3 maintained >90% removal efficiency over five cycles and demonstrated notable antibacterial activity against Escherichia coli and Staphylococcus aureus. A prototype device further validated its practical potential for wastewater treatment.