| In this study, poplar with little residual hemicelluloses was used as the raw material to bepretreated by sodium sulfite(Na2SO3) pretreatment. The effects of Na2SO3charge, holding timeand temperature after Na2SO3pretreatment on sulfonic acid group content, chemicalcompositions, solid yield and the subsequent substrate enzymatic digestibility(SED) wereinvestigated. And the condition of fractionlation was optimized by using orthogonal experiment.Compare average polymerization degree and crystallinity of solid after Na2SO3pretreatmentwith those of poplar with little hemicelluloses. Then the regular of lignin solubility afterNa2SO3pretreatment was researched by infrared spectrum(FI-IR) and Gel permeationchromatography(GPC). At last, performance of sodium lignosulfonate in the liquid afterNa2SO3pretreatment was measured. All the results were as follows.In the Na2SO3pretreatment process, enhancing Na2SO3charge, temperature and holdingtime could increase SED and delignification degree of solids. The SED was98%with80%Na2SO3at180°C for90min..From the orthogonal experiment, effect degree of Na2SO3dosage on SED was the most, andeffect degree of holding time on SED was the least.In XPS,2p trajectory of sulfur element spectrum confirmed the existence of sulfonic acidgroup after Na2SO3pretreatment.In FI-IR, the decline of peaks in1594cm-1and1230cm-1confimed the degradation ofsyringyl lignin.From the crystallinity and average polymerization degree of cellulose, the molecular weightand crystallinity of cellulose after Na2SO3pretreatment reduced a little.The results from GPC showed that the different conditions of Na2SO3pretreatment did notaffect the molecular weight distribution of sodium lignosulfonate.Adsorption capacity of sodium lignosulfonate on titanium dioxide(TiO2) decreased whenthe pH value of the solution increased. And when concentration of sodium lignosulfonate waslower than375mg/L, dispersion performance was good when pH value was lower thanisoelectric point of TiO2. But when concentration of sodium lignosulfonate was higher than375mg/L, the increase of pH value can improve dispersion performance.Na2SO3pretreatment could separate cellulose and lignin well. The introduction of thesulfonic group after Na2SO3pretreatment could improve enzymatic digestibility of solids andsodium lignosulfonate gotten from the liquid after Na2SO3pretreatment was pure. |
