Self-assembly of binary oppositely charged polysaccharides into polyelectrolyte complex hydrogel film for facile and efficient Pb2+ removal

Abstract

Herein, a novel polyelectrolyte complex (PEC) hydrogel film has been fabricated through self-assembly of two oppositely charged polysaccharides salecan and carboxymethyl chitosan (CMCS) for Pb2+ removal. The formation of PEC network structure via electrostatic interactions was confirmed by FT-IR, XRD, XPS and TGA. The change of salecan/CMCS ratio had obvious influence on the swelling capacity, morphology and rheological properties of the hydrogel films. The adsorption capacity of Pb2+ was specifically investigated by tuning the salecan/CMCS ratio, other ions, pH, ion concentration and contact time. Furthermore, the equilibrium isotherms were better fitted with Langmuir model, indicating monolayer adsorption behaviour. The maximum adsorption capacity of Pb2+ according to Langmuir model was 418.4 mg/g, higher than that of some other adsorbents. The adsorption kinetics was well modelled by pseudo-second-order and Crank model, suggesting chemisorption and internal diffusion control mechanism. The PEC hydrogel film also exhibited excellent reusability after 5 adsorption/desorption cycles without obvious changes in the adsorption capacity. Overall, these results not only highlight a new idea for the utilization of salecan, but also provide a green method for the rational design of highly efficient adsorbent for Pb2+ removal.