Physically Cross-linked Organic Double Network Polymer Hydrogels And Their Composites With Powder Materials For Water Treatment

Hydrogels have attracted wide attention due to their high moisture content and porous network structure in water treatment applications.In this study we investigated preparation of green physically crosslinked double network hydrogel consisted of macromolecules alginate which can be gelated by ion exchange and polyvinyl alcohol which can be gelated through freeze-thaw method.Moreover,powder materials were used to improve mechanical properties and functionalize hydrogels.Through the combination of natural bio-macromolecules with powder materials,various types of composite hydrogels can be obtained to meet various demands.The hydrogle has excellent mechanical properties which is benefit for regeneration and also solve the problem of solid-liquid separation of powder materials in water treatment.Therefore,mainly contents and results this research are listed as follows:?1?As the natural bio-macromolecule sodium alginate can be gelated by ion exchange,and polyvinyl alcohol can be gelated by freeze-thaw method,physical crosslinked double network hydrogel consisted of alginate and PVA was synthesized.The effects of the mass ratio of the two networks and different gelation sequences on material properties were studied.The results showed that the double network hydrogel exhibited excellent shape recovery and self-healing properties;when alginate was used as the first network,the prepared hydrogel had a better structure,lower swelling ratio and higher mechanical performance than PVA.?2?Methylene blue?MB?which is regarded as the common pollutants used to evaluate the adsorption capacity of the adsorbent was selected as targeted pollutant to study the adsorption behavior of the single/double network hydrogel.The result showed that the optimum dosage was 1 g/L when the initial MB concentration was chosen as 500 mg/L.The higher that pH was,the better that the ability of adsorption was.The hydrogel Compared with the single network hydrogel,the double network hydrogel had higher adsorption capacity and shorter time of adsorption equilibrium.The adsorption kinetics results were accorded with the quasi two order kinetic model.The adsorption process is exothermic.The excellent adsorption properties of double network hydrogels are mainly due to their more porous network structure,abundant oxygen-containing functional groups and the interaction with MB.?3?GO/double network composite hydrogels with physically cross-linked organic double network gel fixed support graphene oxide was constructed?GO?,alginate hydrogel,PVA hydrogel,single network hydrogel support GO was used for comparison,and characterized their performance.The experimental results showed that the composite hydrogel still had a uniform three-dimensional network structure.The composite hydrogel had a more dense structure than a pure polymer hydrogel,and had a lower swelling ratio;with the concentration of GO increased,it can be seen that composite hydrogel reduced the swelling performance,increased the mechanical properties,and increases the MB removal rate.?4?Hydrogel DAPFe prepared by double network and iron oxide presented a three-dimensional porous network structure which was similar to honeycomb coal.Because of the high degree of crosslinking,the water content of DAPFe was lower than SAPFe,but the water content can still reach 80%.The specific surface area of DAPFe was 89.01 m²/g,and the specific surface area of the double network hydrogel with unfixed support for nano iron oxide was greatly improved.Carboxyl and hydroxyl functional groups were rich in chelating with heavy metals.DAPFe and SAPFe as adsorbent to study their adsorption performance for Cu²⁺in aqueous solution.Results showed that with the increase of pH,the Cu²⁺adsorption capacity increased gradually.The kinetic data were fitted to pseudo-second-order kinetic model reasonably well,and the adsorption rate of SAPFe is greater than that of DAPFe.The adsorption process could be well described by the Langmuir adsorption isothermal model,indicating that the adsorption of Cu²⁺by magnetic polymer composite hydrogel is monolayer adsorption.The maximum adsorption capacity of DAPFe on copper ions was up to 207.01 mg/g,and the adsorption performance was better than SAPFe?173.01 mg/g?.?5?For the activated carbon/polymer composite hydrogel?CAP?,the specific surface area and pore volume were 112.7 m²/g and 0.187 cm³/g,the average pore size of about 6.64 nm.Compared with activated carbon,CAP contains more hydroxyl and carboxyl functional functional groups,which was beneficial to the adsorption of heavy metals.CAP has good stability and thermal stability of acid and alkali.CAP were prepared as adsorbent to study their adsorption performance for MB and Cu²⁺in aqueous solution.The influences of dosage,pH,temperature,contact time,initial concentration of MB and Cu²⁺on the adsorption process were investigated.The results indicated that with the dosage and temperature increase,the adsorption amount of MB and Cu²⁺on CAP decreased,while with the increase of p H,the adsorption amount increased.The adsorption isotherm could be fitted by the Langmuir equation and the maximum monolayer adsorption capacities of MB and Cu²⁺on CAP attained 1940.75 and190.48 mg?g^-1,respectively.The kinetic data were fitted to pseudo-second-order kinetic model reasonably well.Moreover,CAP still had excellent adsorption properties after 5 times of regeneration.