Chitosan modified polyacrylonitrile fiber as adsorbent for removal of sulfosalicylic acid and Congo red.

In this study, one novel CS/PAO composite was synthesized by modifying amidoximated polyacrylonitrile (PAO) fibers with chitosan (CS). The composite exhibited excellent adsorption performance for sulfosalicylic acid (SSA) and Congo red (CR). The maximum adsorption capacities reached 63.5 mg·g-1 for SSA (pH 3.07, 293 K) and 91.2 mg·g-1 for CR (pH 6.38, 313 K) at an initial concentration of 200 mg·L-1. Kinetic analysis revealed that both pseudo-first-order and pseudo-second-order models fitted the data well, suggesting a mixed mechanism involving both physical and chemical adsorption. Isotherm modeling indicated distinct behaviors: SSA adsorption followed the Freundlich, Koble-Corrigan, and Temkin models, implying a multilayer adsorption process, whereas CR adsorption complied with the Langmuir, Koble-Corrigan, and Temkin models, indicating a combination of monolayer and multilayer interactions. Thermodynamic studies confirmed that both processes were spontaneous and entropy-driven; however, SSA adsorption was exothermic, while CR adsorption was endothermic. Reusability tests showed that the composite retained 71% of its capacity after three regeneration cycles. Furthermore, CS/PAO demonstrated significant antibacterial activity against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. Coexisting substance experiments revealed that cationic species enhanced CR adsorption via electrostatic attraction, whereas anionic substances like humic acid and SDS inhibited it. The material also maintained effective adsorption in natural lake water, highlighting its practical applicability. XPS analysis confirmed that hydrogen bonding and electrostatic attraction were the primary driving forces. Overall, the CS/PAO composite presents a promising candidate for efficient wastewater treatment.