Preparation And Properties Of Alginate-based Hybrid Hydrogels Integrated With Inorganic Nanoparticles

Encapsulating pesticides and fertilizers in hydrogels can control their release and increase their availability.Furthermore,the use of hydrogels integrated with semiconductor photocatalysts can effectively remove dyes from wastewater and purify water resources for agricultural irrigation.In order to improve the use efficiency of agrochemicals and improve the water quality of agricultural irrigation water resources,a variety of eco-friendly nanoparticles were prepared by integrating a series of inorganic nanoparticles with different characteristics in alginate-based hybrid hydrogel matrix.Their controlled release properties and the performance of dyes in wastewater were studied.Based on natural soil colloids and natural polysaccharides（sodium alginate）,we have developed a series of eco-friendly interpenetrating polymer network hydrogels.The natural soil colloid was extracted by a simple and eco-friendly method,which has a large specific surface area(48.70±0.82 m²·g^-1),a small particle size（262.00±22.86 nm）and a layered structure.FTIR spectroscopy confirmed that the soil colloids were incorporated into the polymer matrix of the hydrogel and that hydrogen bonds were formed between them.The X-ray diffraction pattern shows the spalling of the soil colloidal sheet in the hydrogel.Morphological characterization of the hybrid hydrogel showed that the sheet of soil colloid was successfully embedded in the matrix of the hydrogel.Thermogravimetric analysis indicates that the presence of soil colloid enhances the thermal stability of the hydrogel.Swelling characteristics experiments have shown that the presence of soil colloids accelerates the water absorption of water by hydrogels,which is manifested by an increase in the kinetic constant k.Since the diffusion index n of all hydrogels is less than 0.5,the swelling process of the hydrogel conforms to Fickian diffusion.Pure hydrogels without soil colloids released 58.0%of pesticides in 10.5 hours,while hybrid hydrogels integrated with natural soil colloids slowly released 34.4%of pesticides within 42 hours.The release data indicates that the presence of soil colloids hinders the diffusion of pesticides into the water in the hydrogel.The behavior of the hydrogel releasing pesticides is consistent with both primary and secondary release kinetics.Based on these results,we believe that the hydrogel synthesized in this chapter is expected to be an ideal controlled release carrier for pesticides in modern agriculture and horticulture.Furthermore,to the best of our knowledge,composites made from natural soil gums have not been found in previous literature.We used a series of eco-friendly interpenetrating polymer network hydrogels integrated with soil colloids as carriers for fertilizers to study the properties of controlled and slow release fertilizers.Among them,the pure hydrogel without soil colloid released 69.1%of the fertilizer in 9 hours,while the hybrid hydrogel integrated with natural soil colloid released 44.5%of the fertilizer at the slowest release rate in 30.5 hours.The release data indicates that the presence of soil colloids retards the diffusion of fertilizer into the water in the hydrogel.Hydrogel release fertilizer behavior combined with secondary release kinetics.Based on these results,we believe that the hydrogel synthesized in this chapter is also expected to be an ideal controlled release carrier for fertilizers in modern agriculture and horticulture.Pesticides and fertilizers,two essential agricultural chemicals in modern agriculture and horticulture,can be loaded and controlled and continuously released by this hybrid hydrogel.Based on photocatalyst（TiO₂）and natural polysaccharide（sodium alginate）,we have developed a series of eco-friendly interpenetrating polymer network hydrogels to study the performance of dye wastewater removal.Doping nano-TiO₂ can not only increase the adsorption capacity of the hydrogel to the dye,but also effectively degrade the dye molecules through the nano-TiO₂ integrated in the hydrogel matrix,thereby greatly improving the total removal ability of the hydrogel.Based on these results,we believe that the hydrogel synthesized in this chapter can be applied to the field of wastewater treatment to effectively purify water resources for agricultural irrigation.A series of eco-friendly interpenetrating polymer network hydrogel films integrated with g-C₃N₄ nanosheets were synthesized by self-initiated polymerization.The removal ability of methylene blue in aqueous solution was studied.The X-ray diffraction pattern shows that the g-C₃N₄ nanosheet is present in the hydrogel film.The mechanical properties test results show that the tensile strength of g-C₃N₄nanosheet/polyacrylamide/sodium alginate hydrogel film is 368 KPa and the elongation at break is 28.8;The tensile strength of g-C₃N₄ nanosheet/polyacrylamide hydrogel film is 54.2 KPa and the elongation at break is 18;the mechanical properties of the g-C₃N₄nanosheet/polyacrylamide/sodium alginate hydrogel film with IPN structure are much better than those of g-C₃N₄nanosheet/polyacrylamide hydrogel film.The dispersion stability experiment showed that the stability of the aqueous dispersion of g-C₃N₄nanosheet added with sodium alginate was greatly improved,and it remained stable during the synthesis of hydrogel film,and the g-C₃N₄ nanosheet was uniformly dispersed in the hydrogel film.The g-C₃N₄nanosheet/polyacrylamide/sodium alginate hydrogel film can effectively adsorb and degrade dye molecules under visible light irradiation,and achieve synergistic effect of adsorption and photodegradation.Under visible light irradiation,the ability of the g-C₃N₄nanosheet/polyacrylamide/sodium alginate hydrogel film to remove methylene blue from aqueous solution is significantly greater than that of a block hydrogel.Based on these results,we believe that the hydrogel film synthesized in this chapter can be applied to the field of wastewater treatment to effectively purify water resources for agricultural irrigation.