Preparation Of Cationic Lignin-based Hydrogels And Its Application In Wastewater Treatment

Lignin,as a kind of renewable material,can be used for research and utilization.But,nowadays,the value of lignin has not fully used in the reality society,so that it is very necessary to develop and study the efficient utilization of lignin.Not only beneficial to the construction of resources saving society,but also correspond to the concept of green development.In this study,two difference preparation and synthesis thoughts of two types lignin based cationic type hydrogels were discussed,and the physical properties and chemical properties of hydrogels and adsorption behaviors also showed carefully.At first,we use lignin as the matrix,using acrylamide and acrylic acid as monomers.Under the action of initiator,adding cationic monomer and polyvinyl alcohol,the semi-interpenetrating network hydrogel?semi-IPN SAR?with positive charges was prepared.In the process of preparing cationic lignin based hydrogel,the temperature,reaction time,the concentration of initiator as the single experiment factor was discussed at first.Then,design the orthogonal experiment with different monomer dosage,to explore the best conditions of the experiment.The result showed that,the optimal conditions of two different monomers preserve uniformity,the best experimental conditions was: the temperature is 70 centigrade,the reaction time is 4 h,the initiator concentration is 30g/L.The optimal synthesis conditions were lignin: acrylamide: polyvinyl alcohol:?2-?acryloyloxy?ethyl?trimethylammonium chloride =1:12:1:2,lignin: acrylic acid: polyvinyl alcohol:?2-?acryloyloxy?ethyl?-trimethylammonium chloride =1: 12: 2: 8.The physicochemical properties of two kinds of hydrogels: Lig-g-P?AM-co-DAC?and Lig-g-P?AA-co-DAC?were characterized by the modern analytical testing method.By infrared spectroscopy?FTIR?analysis,new functional groups were found in the structure of these two kinds of cationic lignin based hydrogels,showed that grafting reaction was successful.By scanning electron microscope analysis,the surface of hydrogel have large number of pores,which provide adsorption sites for the adsorption of pollutants.Then,the swelling properties of two kinds of hydrogels was tested in different environments.Two kinds of hydrogels showed obviously different properties.Among them,the maximum swelling rate of Lig-g-P?AM-co-DAC?was 22.28 g/g,and was smaller than the maximum swelling rate of Lig-g-P?AA-co-DAC?,which was 125.5 g/g.The swelling capacity of the two hydrogels changed as the difference of external environment,eg.temperature,p H,the concentration and species of the salt solution,and showed good repeatability.Finally,we discussed two kinds of hydrogels adsorption properties of azo dye methyl orange and anion Cr₂O₇^2-,two products showed significant difference in adsorption of methyl orange.The adsorption capacity of Lig-g-P?AM-co-DAC?is stronger than Lig-g-P?AA-co-DAC?.And in accordance with the pseudo two order kinetics model and the model of isothermal adsorption of Langmuir model.Two kinds of products showed similar adsorption capacity in the adsorption of Cr₂O₇^2-,the adsorption capacity of Lig-g-P?AA-co-DAC?was slightly higher than Lig-g-P?AM-co-DAC?,both in accordance with the pseudo two order kinetics model and the model of isothermal adsorption of Langmuir model.