Structure Elucidation Of Lignin And Its Pb(?) Adsorption And UV Resistance

As the concept of biorefinery proposed,the comprehensive utilization of lignocellulosic biomass has attracted extensive attention.Lignin is the main components of lignocellulosic biomass and the largest source of aromatic ring materials in nature.However,the complex chemical structure and low reactivity of lignin is always the greatest challenge and limitations in the utilization of lignocellulosic biomass,which are directly related to the biomass species and extraction methods.Therefore,in this study,the green solvents of alcohol were used to pretreate Eucalyptus,and the structure of obtained lignin was controlled at the source by optimizing the extraction process.Meanwhile,it would provide the theoretical guidance for the potential applications of lignin in biomass based materials and chemicals through characterizing their structure.In addition,the physical and chemical modification were performed to deal with the problem that the technical lignin was difficult to be directly utilized,and to expand the application of technical lignin.The lignin based heavy metal absorbent and nanoparticles were prepared,which provided a novel research approach for realizing the high value utilization of lignin.The lignin extracted with 2-propanol was possibly suitable for the subsequent catalytic degradation due to the in-situ hydrogenation of isopropanol.In this study,the Eucalyptus was subjected to organosolv pretreatment processes under different 2-propanol concentrations,temperature and time to extract lignin,and the structure features of the obtained lignin was systematically characterized by several technologies.The result showed that the highest delignification ratios of 81.26%was achieved.The contents of ?-O-4,?-?,and P-5 linkages were regularly decreased with the increase of extraction temperature and time.The chemical structure of lignin that extracted with 70%2-PrOH/water was less-altered and has low molecular weight as compared to that with 50%2-PrOH/water.Remarkably,the lignin with the lowest molecular weight(Mw=610 g/mol)was achieved at 200? for 120 min.In addition,the glucose yields of the pretreated substrates significantly increased from 9.2%to 54.65-88.59%.In order to reduce the extraction temperature and time,the aluminium chloride(AICl3)was used as a catalyst in the ethanol/water system to extract lignin from Eucalyptus under the mild condition.The effects of AICl3 and temperature on the structural features of lignin and the following enzymatic hydrolysis of Eucalyptus were thoroughly investigated.The comprehensive results showed that the lignin extracted with AICl3 catalyst exhibited smaller molecular weights(Mw)and higher phenolic hydroxyl contents through the breakage of ?-O-4 linkages.Meanwhile,the structural characteristics of L-130 were similar to those of L-180-0,which suggested that AICl3 significantly reduced the temperature that required for lignin extraction.In addition,the relatively mild pretreatment process(160?,60 min)remarkably enhanced the enzymatic hydrolysis of substrates to a maximum value of 95.02%.Therefore,the ethanol/water solution pretreatment with AICl3 catalyst is an environmentally benign and advantageous scheme for the production of lignin with low Mw,high chemical reactivity and less-altered structural,which will be contribute to optimize the biorefinery process.The alcoholic depolymerization and Mannich reaction were conducted to improve the chemical activity of biorefinery lignin and introduce the amino groups into lignin,respectively.Meanwhile,the chemical structural transformations of lignin were characterized to reveal the mechanisms of depolymerization and modification.The NMR results indicated that the lignin with low molecular weight and high reactivity was obtained through the cleavage of ?-O-4 linkages and demethoxylation in the depolymerization process.The depolymerization temperature and the ethanol concentration instead of the capping reagents were the main factors for the lignin depolymerization.Additionally,the Mannich reaction was very selective,primarily occurred at H3,5 and G5 positions,and the H units present a higher chemical reactivity.It is believed that the understanding of the fundamental chemistry of lignin during depolymerization and Mannich reaction process will contribute to the extension of the high value-added applications of biorefinery lignin.An effective lignin-based bio-adsorbent(SAPL-1.5)was synthesized through successively phenolation under acidic condition and chemical modification of biorefinery lignin.The results showed that the active sites of lignin was improved from 2.29 mmol/g to 7.05 mmol/g after phenolation process,and then enhanced the grafting efficiency of amine group and CS2.Meanwhile,the influences of initial Pb(?)concentration,pH,lignin-based absorbent(SAPL-1.5)dosage and contact time on the adsorption performance of lignin were systematically investigated.The result showed that the highest adsorption capacity and removal efficiency reached to 130.2 mg/g(Pb(?),140 mg/L)and 100%(Pb(?),20 mg/L),respectively.In additon,the removal efficiency of SAPL-1.5 for Pb(?)(20 mg/mL)still maintained over 85%after 5 cycles.Therefore,it is believed that the lignin-based adsorbent(SAPL-1.5)has a promising potential for the adsorption of heavy metals.In this study,the regular lignin nanoparticles with high uniformly and dispersion were prepared by a solvent shifting combined ultrasound process in the THF-water solvent.Meanwhile,the forming mechanism of lignin nanoparticles were investigated through characterizing the chemical structure and physical morphology of lignin.The biorefinery lignin was first modified through a microwave acetylation process without any catalysts and solvents,and the DS of modified lignin reached to 0.85,which was a fast,economic,and green process.The yield of lignin nanoparticles significantly enhanced and reached to 82.3%as the lignin initial concentration and the ultrasonic intensity increased.In addition,the high intensity of ultrasonic was beneficial to generate more regular and uniform nanoparticles,while it would increase the dispersibility and simplify the preparation process of lignin nanoparticles.To some extent,the sunscreen performance of chemical cream increased by 115%through the addition of lignin nanoparticles.