Preparation Of Sodium Alginate-Based Gel Materials And Study On Its Adsorption Properties

The dyes and heavy metal ions in water bodies not only endanger the ecological environment,but also pose a major threat to human health through enrichment of the biological chain.Biomass-based adsorbent materials are widely used in the field of water treatment because of their economical,environmentally friendly,and renewable design and ease operation.Sodium alginate（SA）as a common biomass material has the advantages of being widely sourced and environmentally friendly,but its application in water treatment is limited by its low adsorption capacity and poor water stability.In this paper,two kinds of alginate-based aerogels and one kind of alginate-based hydrogel were prepared by multiple-blending crosslinking and modification of active functional groups,and their adsorption properties for dyes and heavy metal ions in water were studied.The physical morphology and chemical structure of gel materials were characterized by the SEM,FT-IR,TG,and XPS.The adsorption mechanism of gel materials was explored by combining adsorption kinetics and adsorption isotherm.The main studies are as follows.（1）Three-dimensional porous sodium alginate/gellan gum aerogel（SAG aerogel）was prepared.By adjusting the addition ratio of gellan gum（GG）,the adsorption performance of this aerogel on the cationic dye methylene blue（MB）in water was studied,and the structure and properties of the aerogel were characterized by FT-IR,SEM and XPS.SAG aerogel was successfully prepared by combining GG with SA through ion chelation and hydrogen bonding.The addition of GG optimized the pore structure of SAG aerogel and improved the adsorption performance of SAG aerogel.The adsorption process accorded with the Langmuir isotherm model and Pseudo-second-order kinetic model,and the maximum adsorption capacity was 1456.45 mg/g.After five adsorption-desorption cycles,the aerogel can still maintain a good adsorption effect.（2）Three-dimensional porous PEI@SA/GG aerogels were prepared by introducing amino groups with PEI as the modified material.The adsorption performance of this aerogel on the anionic dye Congo Red（CR）in water was investigated.The physical morphology and chemical structure of aerogels were studied by FT-IR,SEM,EDS,and XPS.With the successful introduction of PEI,the stability of the aerogel was improved,the electric dipole property of the aerogel surface was changed,and the adsorption capacity of the anionic dyes was improved.The adsorption process conformed to the Langmuir isotherm model and Pseudo-second-order kinetic model,and the maximum adsorption capacity was 3017.23 mg/g.In a binary dye system,the aerogel has high selective adsorption for CR.（3）Inspired by mussel biopodin,poly（TA-DETA）-modified sodium alginate composite hydrogel beads were prepared from tannic acid（TA）and diethylenetriamine（DETA）under mild conditions.The adsorption performance of hydrogel beads on hexavalent chromium ions（Cr（VI））in water was investigated by regulating the molar ratio of TA and DETA.The structure and properties of hydrogel beads were characterized by FT-IR,SEM,EDS,and XPS.TA and DETA were successfully polymerized in the SA system,and porous hydrogel beads were successfully prepared.The hydrogel beads have good water stability and mechanical strength,and the adsorption capacity of Cr（VI）can reach 163.9 mg/g,which is about 10 times of pure SA gel beads.The adsorption process followed the Freundlich isotherm model and Pseudo-second-order kinetic model.The interference of Na⁺,Zn²⁺,Al³⁺,Cl^-,and NO₃^-in water on the adsorption of Cr（VI）by gel beads was small.In the dynamic adsorption experiment,the adsorption process follows the Thomas model.