Preparation And Adsorption Performance Of Polyvinyl Alcohol/Sodium Alginate Based Composite Hydrogels

Polyvinyl alcohol（PVA）has a regular linear structure and good formability,with a large number of side hydroxyl groups on the molecular chain which can form hydrogen bonds with graphene oxide.Sodium alginate（SA）is a kind of water-soluble anionic bio-polymer derived from natural seaweed or produced by bacteria,rich in hydroxyl and carboxyl groups,with a strong affinity for metal ions.In this paper,three PVA/SA-based composite hydrogels were prepared by freeze-thawing method and ionic cross-linking.The structures of the samples were characterized by SEM,FT-IR and XRD,the mechanical properties of the composite hydrogels were tested by tensile testing machine,and the adsorption properties of the composite hydrogels were tested by UV spectrophotometer.The results were as follows.（1）The PVA/SA composite hydrogels were prepared by freeze-thaw method using PVA and SA as raw materials.The effects of the ratio of reactants and tensile rate on the mechanical properties of the composite hydrogels were investigated;the adsorption properties of PVA/SA composite hydrogels on Fe³⁺were studied.The results showed that:after the mixing of PVA and SA,the hydrogel gelation process destroyed the original crystalline properties of PVA and SA and formed an interpenetrating network structure through cross-linking;the Young’s modulus of the composite hydrogel gradually increased with the increase of SA content.The Young’s modulus of the composite hydrogel increases gradually with increasing SA content.The composite hydrogel strain softens at small strains and strain hardens at large strains.When the mass ratio of PVA/SA solution was1/4,the amount of hydrogel in the adsorption system was 0.030 g,the initial concentration of Fe³⁺was 50 mg/L and the p H value of the solution was 5,the adsorption amount and the adsorption rate of Fe³⁺by the composite hydrogel were 83.11 mg/g and 99.74%,respectively,and the adsorption process was a quasi-secondary kinetic model with the mechanism of chemisorption.（2）PVA/SA/GO composite hydrogels were prepared by the freeze-thaw method using PVA,SA and graphene oxide（GO）as raw materials.The effects of GO content and tensile rate on the mechanical properties of the composite hydrogels were investigated;the adsorption properties of the composite hydrogels on Fe³⁺were studied.The results showed that the GO sheets were well dispersed in the PVA/SA matrix.When the GO content was1 wt%,the mechanical properties of the composite hydrogel improved significantly,with the elongation at break increased by～60%,the stress at break increased by 0.84 MPa and the Young’s modulus increased by 0.12 MPa;the composite hydrogel strain softened at small strains and strain hardened at large strains.When the GO content in the composite hydrogel was 3 wt%,the amount of hydrogel in the adsorption system was 0.030 g,the initial concentration of Fe³⁺was 50 mg/L and the p H of the solution was 5,the adsorption amount and the adsorption rate of Fe³⁺by the composite hydrogel were 83.24 mg/g and99.88%,respectively,and the adsorption process was a quasi-secondary kinetic model with a chemisorption mechanism.（3）The PVS/SA/Mxene composite hydrogel was prepared by freeze-thaw method using PVA,SA and Mxene as raw materials.The effects of Mxene content and tensile rate on the mechanical properties of the composite hydrogels were investigated.The adsorption properties of the composite hydrogels on Fe³⁺were investigated.The results showed that when the Mxene content in the composite hydrogel was 1 wt%,the mechanical properties of the composite hydrogel slightly improved,and the elongation at break increased by～57%under the condition that the tensile strength was basically unchanged,and the composite hydrogel strain softened at small strains and strain hardened at large strains.The adsorption amount and the adsorption rate of Fe³⁺by the composite hydrogel were 49.43 mg/g and98.86%,respectively,when the amount of hydrogel in the adsorption system was 0.050 g,the initial concentration of Fe³⁺was 50 mg/L and the p H of the solution was 4.The adsorption process was a quasi-secondary kinetic model and the mechanism was chemisorption.Figures[47]Tables[18]References[104]...