Preparation And Application Of Sodium Alginate-based Smart Hydrogel Materials

The unique properties of hydrogels make them widely used in biomedicine,environmental science and agriculture.In recent years,sodium alginate-based hydrogels have attracted much attention due to their excellent biocompatibility,biodegradability,renewability,flame retardancy,and ion exchange properties.In this study,several sodium alginate-based intelligent hydrogel materials were prepared by photopolymerization,free radical polymerization,and Diels-Alder click reaction,respectively.The physical properties,structural characterization of hydrogels and their applications in dye adsorption,fertilizer release,and drug release were investigated.The main work includes the following four parts:(1)In the presence of sodium alginate(SA),the sodium alginate-based semiinterpenetrating(semi-IPN)hydrogel(SA/PND)with p H/temperature sensitivity was prepared by photoinitiated polymerization using N-isopropyl acrylamide and N,Ndimethylacrylamide as monomers and N,N’-methylacrylamide as cross-linking agent.The preparation conditions of hydrogel were optimized through performance testing,and the structure and morphology of hydrogel was characterized by FTIR,SEM,XRD,etc.The results showed that the addition of SA improved the mechanical properties of hydrogels,and the physical properties of hydrogels could be improved by changing the preparation conditions.The hydrogel adsorbent showed good selective adsorption ability for MB,and the maximum adsorption capacity reached 151.79 mg/g at p H=10.The adsorption was a spontaneous exothermic process caused by electrostatic attraction and hydrogen bonding.Furthermore,the adsorbent has good reusability,and the recovery efficiency is 75.91% after five consecutive adsorption-desorption cycles.(2)Firstly,sulfonated sodium alginate(SSA)was prepared by sodium periodate oxidation and nucleophilic addition of sodium bisulfite.Then,sulfonated sodium alginatebased p H-sensitive semi-IPN hydrogel adsorbents(SSA/PAS)were prepared by "one-pot method" with acrylamide and sodium styrene sulfonate as monomers,polyethylene glycol dimethacrylate as cross-linking agent,and in the presence of sulfonated sodium alginate.The adsorption properties of the cationic dye MB under different factors were studied,and the adsorption mechanism was discussed by kinetic and thermodynamic models.The results showed that the prepared hydrogel had good water absorption,swelling circularity and p H sensitivity,and the maximum swelling degree could reach 9700%.It has a high adsorption efficiency,and the maximum adsorption capacity of MB can reach 1624 mg/g at p H=10,which is expected to be an ideal adsorbent for water treatment.(3)Using N-isopropyl acrylamide and 2-acrylamyl-2-methylpropanesulfonic acid as monomers,polyethylene glycol dimethacrylate as crosslinking agent,and potassium persulfate/ascorbic acid as REDOX initiator system,in the presence of sodium alginate(SA)and humic acid(HA),alginate-based semi-IPN hydrogels(SH/PNA)with dual p H/temperature sensitivity were prepared by free radical copolymerization.The preparation conditions of hydrogel were optimized by performance test,and its structure and morphology were characterized by FTIR,SEM,XRD,etc.Then,the urea loaded hydrogel was used to explore the controlled release behavior of urea in water and soil by pdimethylaminobenzaldehyde chromogenic method,and the release mechanism was analyzed by kinetic model.The results showed that the addition of SA/HA improved the mechanical properties of the hydrogel,and the properties of the hydrogel could be improved by changing the preparation conditions.In addition,the fertilizer synthesized with SH/PNA hydrogel could control urea release from water and soil,thus improving the fertilizer utilization efficiency and reducing the adverse impact on the environment.(4)3-Maleimide propionic acid was used to modify hydroxypropyl methylcellulose to synthesize macromolecular dienophiles,and β-cyclodextrin was modified with succinic anhydride and furfurylamine to obtain furan ring modified cyclodextrin(diene).Subsequently,the aqueous solutions of macromolecular dienophiles,dienes and sulfonated sodium alginate were prepared,and sulfonated sodium alginate-based p H/temperature double sensitive hydrogel microspheres(SSA-GPs)were prepared through Diels-Alder cycloaddition reaction using a spray drying instrument.The structure and properties of the microspheres were characterized.Finally,curcumin and aspirin were used as model drugs to prepare hydrogel microspheres(Gel/Cur/Asp)loaded with the two drugs.The controlled release behavior and release mechanism of the hydrogel microspheres were studied in the environment of simulated human intestinal juice and gastric juice.