Preparation And Application Of Lignin Modified Hydrogel Complex

It has become an important research topic to develop biomass resources,reduce dependence on fossil resources and reduce environmental pollution.Lignin,as a rich natural polymer with aromatic structure in biomass resources,is gradually attracting researchers' attention because of its advantages such as biodegradability,biocompatibility,non-toxicity,regeneration and so on.However,the complexity of lignin macromolecular structure and the diversity of source derivatives give researchers a headache.In this paper,using sodium lignosulfonate and sulfate lignin as raw materials,a series of lignin-based hydrogel composites were studied through a series of simple methods,and their applications were discussed,which made efforts to find a way to make high-value utilization of lignin.Sodium lignosulfonate single network hydrogel was prepared by sodium lignosulfonate and acrylic acid.The effect of the amount of each component of hydrogel on hydrogel was discussed,and the rheological behavior of hydrogel was studied.The thixotropy of hydrogel and its internal structure and properties were analyzed.The tensile and compression tests of hydrogel were carried out by texture instrument,and its mechanical properties were analyzed.The results showed that the elasticity of hydrogel was lower,hardened and fragile,and the swelling rate decreased when the amount of crosslinking agent was increased.The results of scanning electron microscope show that the network structure can not be presented when the acrylic monomer is insufficient,but with the increase of the amount of acrylic acid,the network structure of the hydrogel becomes denser and the swelling rate decreases,and the hydrogel after swelling presents a relaxed state.As the amount of sodium lignosulfonate increased,the pore and network structure of the hydrogel will decrease and the hydrogel became more compact.Therefore,sodium lignosulfonate acted as filler in the hydrogel,and the change of sodium lignosulfonate did not affect the thermal stability of the hydrogel.the mechanical analysis showed that the increase of the amount of acrylic acid and sodium lignosulfonate could improve the compressive strength of the hydrogel in the appropriate range,but both of them were not conducive to the elongation at break.Besides,sodium lignosulfonate single network hydrogel has strong adhesion and can adhere to many materials,such as rubber,stainless steel block,wood,aluminum,glass,plastic,marble,iron tools and so on.we use it to test the adhesion strength of stainless steel sheet,plexiglass and paper,and their adhesion strength reaches 307,301 and 174 k Pa respectively,but the increase of cross-linking agent is not conducive to the adhesion strength.There is a linear relationship between the adhesion strength and the water content of the hydrogel.On the basis of sodium lignosulfonate single network hydrogel,the sodium alginate-calcium chloride system was introduced to form a double network structure hydrogel.The effects of the amount of sodium lignosulfonate,cross-linking agent and sodium alginate on the compression and cyclic compression properties of the hydrogel were investigated by mechanical properties test.As a filler substance,sodium lignosulfonate is mainly involved in the enhancement of the hydrogel structure by hydrogen bonding.When dosage of sodium lignosulfonate is maintained in a suitable range,the structural strength of the hydrogel can be enhanced,but once it overdoses,the strength of the hydrogel will decrease rapidly.The cyclic compressive test of hydrogel shows that the strength of the hydrogel was able to resist more than 90 high deformation rapid compression.In addition,we found that the compressive strength and toughness of the hydrogels soaked in calcium chloride solution increased,while the adhesion decreased.The modified lignin with high nitrogen content(nitrogen content reached 18.74%)was prepared by aminoization treatment of sulfate lignin by the modification strategy of first sulfonation and then ammoniation.The sample characterization found that the thermal stability of the modified lignin decreased,the small size particles were more,and the morphology had a lot of debris structure compared with unmodified lignin.The antibacterial properties were analyzed that the modified ammoniated lignin had high antibacterial properties,and the antibacterial rates for Escherichia coli,Pseudomonas and Staphylococcus aureus reached 97.34%,99.69% and 97.79%,respectively.With the increase of amino content,the antibacterial effect can also be enhanced.The modified lignin was loaded on the agar hydrogel,and the loaded hydrogel still shows the ability to inhibit the propagation of Escherichia coli.