Study On Preparation And Application Of Modified Sodium Lignosulfonate Hydrogel

Lignosulfonate is one of by-products in paper manufacturing, just in china, thereare millions tons of lignosulfonate are produced each year, but only a very smallamount of them are utilized. Therefore, efforts to develop the lignosulfonate productsand broaden its use are beneficial not only to environmental protection but also toeffective application of resources. Polymeric hydrogel is a type of three-dimensionalnetwork like functional material which is swollen in water but insoluble in water,polymeric hydrogels have important applications in agriculture, construction,pharmaceutical industry, biotechnology, etc. the origin of polymeric hydrogel can beclassified into synthetic polymeric hydrogel and natural polymeric hydrogel, the rawmaterial for the manufacture of synthetic polymer hydrogel mainly come from the oilindustry, is a non-renewable resource with low biodegradability. On the context of thelack of resource and strong sense of environmental protection, the researches on thedevelopment of natural polymeric hydrogel have a long-term strategic significance.Lignosulfonate have a tri-dimensional network like structure containing hydroxyl,carboxyl and sulphonyl groups in their molecules, these structural featurestherotically ensured them to be a good raw material for preparing the hydrogel. Thispaper focuses on the development and utilization of lignosulfonate. Firstly, we studiedthe preparation of lignosulfonate hydrogel, made an investigation into the removal ofreducing sugar in lignosulfonate and preparation of modified lignosulfonatehydrogel.Through this study, we found an effective method to reduce the reducingsugar in lignosulfonate and successfully prepared a type of modified lignosulfonatehydrogel with good water swollen capacity under conditions of no addition ofcross-linking agent. Furthermore, the corresponding studies on the application of thismodified lignosulfonate hydrogel in preparation of nano-material and drug deliverywere also conducted.The research results indicate that the reducing sugar in commercially availablelignosulfonate can be effectively reduced through acid-aided hydrolysis-salting outmethod. The optimal operating conditions are addition of2wt%of sodiumlignosulphate and11.78wt%of sulphonic acid chloride of total solution weight,4hof hydrolysis time at80oC and addition of20wt%of sodium of total weight duringsalting out process. The modified sodium lignosulfonate is prepared by using sodium lignosulfonate after removal of reducing sugar as starting material through oxidationand sulphuration modification procedures. The content of phenol group, carboxylgroup and sulphonyl group in modified sodium lignosulphate is promoted by29%,3.4%and9.7%, respectively. The modified sodium lignosulfonate was thermallytreated under acidic conditions followed by treatment in sodium hydroxide solution;the collected solid by filtration under reduced pressure is modified lignosulfonatehydrogel. The single factor experiment was conducted by varying the level of themajor impact fators that affecting the water swollen capacity and yield of modifiedsodium lignosulfonate, and the optimal preparation route was determined, that is:8gof purified sodium lignosulphate by hydrolysis-salting out method,200mL ofdeionized water and6mL of30%H2O2was mixed, the mixture was heated to50oC,then2.5g of sodium sulfite was added to the mixture and the solution wassulphonated for80min. The solution after sulphonation was dried at135oC for90min, and then the solid was hydrolyzed in0.3M sodium hydroxide for40min at roomtemperature, the yield is about10%based on sodium lignosulfonate. The obtainedmodified sodium lignosulfonate has a water swollen capacity of30.2g/g xerogel.A serial of experiments around the obtained wet hydrogel includes ultrasonicdispersion, scan electron microscope observation; water solubility of dried solid afterultrasonic dispersion and dynamic light scattering, the experiment resultsdemonstrated that the obtained modified sodium lignosulfonate hydrogel is formed byphysical cross-linking. Microgel comprises of particles of micrometer size, it is anexcellent template or micro-reactor for the synthesis of inorganic nano-materials. Weprepared modified sodium lignosulfonate microgel by ultrasonic dispersion, and thenprepared nano silver particles with avarage particle size of9.6nm by reduction in-situbased on the confinement effect of microgel network structure. The dryness of themicrogel-nano silver dispersion leads to nano silver/modified sodium lignosulfonatecomposite microgel. This composite material is expected to be applied in the fields ofmedicine and catalysis. Sodium lignosulfonate is non-toxic and biocompatible, andthe modified sodium lignosulfonate prepared from it has better water swollen capacity,this feature endowed it potential as drug delivery material. The experiment confirmedthat modified sodium lignosulfonate has sustained release property to piperazineferulate. Since the water swollen capacity of this hydrogel can undergo a sharpdeclining under acidic environment, it can be used as sustained release carrier ofdrugs that has stimulation on stomach. In general, modified sodium lignosulfonatehydrogel is a novel type of natural polymeric hydrogel without any addition of cross –linking agent and formed by physical cross-linking of microgel particles. It can bedispersed into microgel by ultrasonic dispersion. Because of its unique properties, thishydrogel is expected to be applied in the fields of nano-material preparation, drugdelivery, and heavy metal ion adsorption and biochemical separation.