Functionalization of cellulose with hyperbranched polyethylenimine for selective dye adsorption and separation

Cationic hyperbranched polyethylenimine (hPEI) was covalently linked onto the backbone of cellulose molecules via forming Schiff base structure between the amino groups of hPEI and the aldehyde groups on the chemically oxidized cellulose surface. The functionalized hPEI-CE possessed available active sites, and its adsorption behavior to anionic dye congo red (CR) and cationic basic yellow 28 (BY28) in aqueous solution was investigated. The hPEI-CE interacted with the two dyes, exhibiting sharp response to solution pH and ionic strength. The adsorption process was well dominated by the pseudo-second-order kinetic model. And the hPEI-CE following the Langmuir isotherm model, had a maximum adsorption capacity of 2100 mg g(-1) for CR and 1860 mg g(-1) for BY28, respectively. Further, the adsorption performance of six dyes onto the hPEI-CE was studied, which showed high adsorption capacities for CR, BY28, brilliant blue 133 (BB133), and reactive red, but very low adsorption for cationic bright yellow 7GL (7GL) and eosin Y (EY). The different adsorption performances for different dyes indicated the selective adsorption of the hPEI-CE for dyes owing to their different distribution coefficient (K) defining as the partition of dyes between hPEI-CE and water. Based on the unique selective adsorption, the mixtures of dyes, such as BB133-CR, BB133-BY28, BB133-7GL, and CR-7GL, were separated successfully using hPEI-CE.