Preparation And Characterization Of Lignin Base Hydrogel

In recent years,ethanol pulping due to its pulping process did not require chemical reagents and the pulping process can produce a lot of by-products(lignin,furfural,polydextrose,etc.),ethanol pulp cooking liquor pollution than conventional pulping,waste liquid contained ethanol which can easy recovery and other advantages caused many concerns.Structure of ethanol pulping lignin damaged little,lignin had a higher activity,which had good to its subsequent modification or preparation of other synthetic material.Hydrogels,especially bio-based hydrogels,had attracted much attention because of their good biocompatibility and biodegradability.Lignin as a natural macromolecular compounds,can be used for the preparation of biological hydrogel,prepared hydrogels in addition to have good biological adaptability,biodegradable,but also had properties of lignin,such as adsorption,used as adsorption material using in the treatment of dye wastewater,etc.In this paper,lignin was separated from the raw materials by ethanol pulping using the poplar as the raw material,and the lignin was purified by weak acid method and liquid liquid method.The purity,molecular weight and structure of the extracted lignin and purified lignin were studied by ion chromatography,infrared spectroscopy,gel permeation chromatography and nuclear magnetic resonance.The results showed that the two purification methods could effectively reduce ash and carbohydrate impurities content,and the method of liquid liquid purification had better to eliminate the carbohydrate impurities.Lignin had chemical connection like ?-O-4,-?,and the content of(3-0-4 was increased after purification and the molecular weight was also increased.The optimum conditions for the preparation of hydrogels were as follows:cellulose concentration 2%,reaction time 4 h,reaction temperature 60 ?,dosage of crosslinking agent 10%.Under this condition,the prepared cellulose hydrogel has a certain strength to maintain its shape,and has a good pore structure.Preparation of lignin hydrogels based on the preparation of cellulose hydrogel,the effect of lignin dosage on hydrogel was investigated and hydrogels were tested comprehensively.The results showed that with the increase of the amount of lignin,the performance of hydrogel changed greatly.The main results were as follows:the color of hydrogel increased obviously,and the content of hydrogel The pore structure pore size increases,the water swelling property of the hydrogel increases,the thermal stability of the hydrogel is reduced,and the strength of the hydrogel is improved to a great extent.In addition,the addition of lignin resulted in the ability of the hydrogel to adsorb to the methylene blue.The methylene blue sustained release experiment further showed that the lignin hydrogel had a release effect on the methylene blue,and with the increase of the amount of lignin,and with the increase of lignin,the slow release capacity of methylene blue increases.The effects of temperature,pH value,methylene blue concentration and adsorption time on the adsorption experiment were studied.The optimum conditions for the adsorption of methylene blue were determined by the lignin hydrogel.Temperature 30 ?,pH 6,adsorption time 10h,methylene blue concentration of 100mg/L.The kinetic analysis of methylene blue adsorption shown that the adsorption of methylene blue on the adsorption of methylene blue was the pseudo-second order kinetic adsorption.In addition,the correlation coefficient of quasi-secondary adsorption was higher,which indicated that the adsorption of methylene blue by hydrogel was chemical adsorption,which may due to the hydrogel containing lignin,lignin in the carboxyl group and other groups interaction with methylene blue.Hydrogel made by liquid-liquid purified lignin had a certain effect on the adsorption of methylene blue dye,under the optimization condition,hydrogel had a maximum adsorption capacity of 32.6 mg/g,addition lignin made cellulose hydrogel which had not effect on methylene blue adsorption obtained this performance,but the adsorption capacity still had a certain gap with activated carbon adsorbent,may related to unmodified lignin had little anionic groups,in order to enhance its adsorption capacity the follow-up to ionized modified lignin.