Eco-friendly Chitosan-Pullulan hydrogels with polyethylene glycol diglycidyl ether for superior adsorption of congo red

The urgent necessity to create affordable adsorbents for the effective elimination of leftover contaminants from wastewater arises from the significant water pollution resulting from the excessive use of dyes. A novel chitosan (CS) /pullulan (PL) hydrogel, chemically cross-linked using polyethylene glycol diglycidyl ether (PEGDE), exhibited high swelling capacity, excellent mechanical stability, and superior adsorption performance. Adsorption tests indicated that CS/PL-2 hydrogel attained a 93.23% removal efficiency for congo red (CR) dye at the concentration of 1000 mg/L. The adsorption capacity of CS/PL-2 hydrogel was investigated in relation to various factors, such as temperature, initial concentration, pH, contact time, and the quantity of adsorbent used. Adsorption kinetics for CS/PL-2 hydrogel were examined utilizing both pseudo-first-order and pseudo-second-order models, with the findings demonstrating that physical adsorption primarily governed the process. The maximum adsorption capacity identified for CS/PL-2 hydrogel, as the Langmuir model, was observed to be 953.60 mg/g, and the thermodynamic analysis of adsorption suggested that the process occurs spontaneously. After five cycles of adsorption, the removal rate of CS/PL-2 hydrogel remained at 70%. In conclusion, this hydrogel adsorbent offers a practical solution for treating CR contaminated wastewater.