Construction mechanism of gellan gum/chitosan/calcium ion multiple‐network hydrogel by self‐assembly strategy and its regulation

Recently, double‐network or multiple‐network hydrogel constructed by physical methods has been considered a green method to improve the comprehensive properties of biomass hydrogel. Herein, a novel physically cross‐linked hydrogel with multiple network of gellan gum/chitosan/calcium ion (GG–CS–Ca) was constructed by self‐assembly to accomplish the synergistic improvement of mechanical strength and uranium adsorption property compared to adsorbents GG–Ca and carboxymethyl konjac glucomannan/GG–Al originated from gellan gum previously prepared. Moreover, the driving mechanism of self‐assembly of GG–CS–Ca was deduced by ¹³C solid state nuclear magnetic resonance spectroscopy (¹³C‐SSNMR), rheological analysis, and phase transition analysis. The results indicated electrostatic interaction was dominant during the self‐assembly of GG–CS–Ca. The self‐assembly mechanism was also illustrated by investigating the x‐ray photoelectron spectrometer (XPS) combined with the analysis of the phase transition process. Comprehensively, the self‐assembly constructed GG–CS–Ca hydrogel network contained three kinds of network including the GG–CS network constructed by electrostatic action of protonated CS with negative charged GG, the GG–Ca network constructed by ionic cross‐linking of COO⁻ in GG and Ca²⁺, and the GG network formed after the phase transformation of GG hot sol by cooling. It explored a new method for constructing biomass‐based physical hydrogels with both favorable mechanical strength and uranium adsorption capacity in uranium removal.