Solid Phase Coupling Interaction Of Mechanical Activation/Metal Salt On Cellulose

In recent years,it is inevitable trend to search new renewable resources due to the increasing energy demand,rapidly growing issue of environmental pollution and the gradually exhausting fossil fuel resources,and the development of bioethanol has attracted more and more attention.The cellulosic biomass is the most promising raw material for bioethanol production because of its abundant and widely available source.However,cellulose possesses the structural characteristics of high-crystallinity,leading to the poor accessibility of cellulose and it is hard to be hydrolyzed by enzyme.In this paper,mechanical activation(MA)/metal salt(MS)with solid phase coupling interaction was adopted for the pretreatment of cellulose to decrease the polymerization degree(DP)and crystallinity index(Crl)of cellulose and improve its enzymatic hydrolysis efficiency,which can provide theory foundation for the effective conversion of lignocellulose.The main research contents and results are as follows.The effects of species and dosage of MS,MA temperature and MA time(tM)on the DP and CrI of cellulose were investigated with cotton cellulose(DP=1000)as raw material.The optimum conditions were obtained:effective metal salts were Al(NO3)3 and AICl3,dosage of metal salt was 1%,MA temperature was 50?,and tM was 60 min.Under these conditions,DP of cotton cellulose decreased from 1000 to 720 by MA pretreatment and from 1000 to 100 by MA/MS pretreatment.Scanning electron microscopy(SEM)examination indicated that the morphological structure of cellulose was destroyed by MA pretreatment and it remained in filamentary structure,but the fibrous structure of cellulose was remarkably disrupt by MA/MS pretreatment and the microfibrils turned into irregular particles.X-ray diffraction(XRD)analysis showed that the MA pretreatment did not alter the crystalline allomorph of cellulose and the CrI decreased from 85.3%to 70.7%,but the MA/MS pretreatment made the crystalline allomorph converted from cellulose I to cellulose II and CrI decreased from 85.3%to 46.4%with tM of 120 min.The cellulose materials with different DP were used to investigate the effect of MA/MS pretreatment on their structural characteristics under the optimum technological conditions and were compared with the effect of MA pretreatment.The results showed that the DP and CrI of cotton cellulose(DP=2500),sugarcane pulp and microcrystalline cellulose(MCC)were decreased by both MA and MA/Al(NO3)3 pretreatments,and continuously decreased with the increase of tM.The effect of MA/Al(NO3)3 pretreatment was more significant than MA pretreatment,indicating that the combined action of MA and Al(NO3)3 had synergistic interaction for the pretreatment effect of cellulose.Enzymatic hydrolysis experiments of untreated and different pretreated cellulose samples were performed with dextrose equivalent(DE)as the evaluation index.The results indicated that both MA and MA/MS pretreatments enhanced the enzymatic hydrolysis of cellulose,and the DE increased with the increase of tM.The effect of MA/MS pretreatment on enzymatic hydrolysis of cellulose was more remarkable compared with that of MA pretreatment.