Effects of Different Rare Earth Ions on the Gel Properties of Sodium Alginate
2022
Chunmei CHEN | Yu FU | Xiaowen ZHUANG | Jiachao XU | Xin GAO | Xiaoting FU
In this paper, the gel properties of sodium alginate with Y3+, Ce3+, La3+ and Er3+ were studied. By studying the mechanical properties, equilibrium water content, ion exchange rate and gel mechanism of seaweed rare earth gel, it was found that: The coordination form of rare earth ions and carboxyl group in sodium alginate was pseudo-bridged monodentate coordination and bridge coordination. At the same time, the special three-dimensional network structure of the rare earth gel was formed through the planar and non-planar geometry formed by intramolecular and intermolecular chelation, and the gel strength of the gel formed by La3+, Y3 +, Er3+, Ce3+ and sodium alginate M/G≈1 was between 32 and 41 N, the Young’s modulus was between 14 and 20 N, the elasticity was between 55% and 59%, the equilibrium water content was greater than 93%, the strength of the four gel was Ce3+> Er3+> Y3+> La3+, the elasticity was Ce3+<Er3+<Y3+<La3+, and the ion exchange rate was: Ce3+ 52.99%, Er3+ 50.81%, Y3+ 40.74%, La3+ 39.33%. Under different M/G ratio, the affinity between rare earth ions and sodium alginate gel was quite different: When M/G=1.99>1, the affinity of seaweed rare earth gel was in this order：Er3+>Ce3+>Y3+>La3+. When M/G=0.99≈1 and M/G=0.19<1, the affinity of seaweed rare earth gel was in this order：Ce3+> Er3+> Y3+> La3+. Among them, Ce3+, Y3+ and La3+ had a certain preference for G fragment of sodium alginate, and Er3+ had a certain preference for M fragment. This study would lay a theoretical foundation for the intensive processing and utilization of sodium alginate and the development of new functional materials of rare earth elements.
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