Selective Separation Of "Three-Component" From Lignocellulose By Benzyl Deep Eutectic Solvents Medium And Their Functional Application

Energy and environmental issues have become important obstacles restricting social development.The development and use of renewable lignocellulose resources to partially replace fossil energy and control environmental pollution have attracted the attention of scientific researchers.However,due to the compact structure and complex chemical properties of lignocellulosic biomass resources,pretreatment is one of the key steps in the functional application of lignocellulose"three-component".Deep eutectic solvents(DES)show great potential in the pretreatment of lignocellulose due to their low cost,degradability and high solubility.In this work,the feasibility of pretreating wheat straw with triethylbenzyl ammonium chloride(TEBAC)as hydrogen bond acceptor and lactic acid(LA)as hydrogen bond donor was discussed to improve the enzymatic hydrolysis efficiency of cellulose.The effects of pretreatment time,reaction temperature,and molar ratio of hydrogen bond donor to hydrogen bond acceptor of benzyl DES on the conversion of polysaccharides in wheat straw were investigated.The research results show that under the optimal pretreatment conditions:the molar ratio of hydrogen bond acceptor to hydrogen bond donor was 1:9;the reaction temperature was 373 K;the pretreatment time was 10 h,the extraction rate of lignin in wheat straw(WS)was as high as73.96±1.26%,the conversion rate of cellulose enzymatic hydrolysis reached 89.06±1.05%,and the yield of glucose reached 66.32±1.58%.The total monosaccharide yield is as high as0.55 g/g _WS which is 91.27%of the theoretical yield(0.603 g/g _WS).The regenerated lignin is mainly composed of syringyl(S)and guaiacyl(G)units.DES can effectively break the ether bond in lignin.Secondly,we successfully extended the benzyl DES to the pretreatment of sugar cane bagasse(SCB).After reacting at 393 K for 4 h,the removal rate of lignin in SCB reached88.72±1.63%,the conversion rate of cellulose enzymatic hydrolysis reached 88.23±1.24%,and the yield of glucose reached 71.42±1.43%.By comparing the effects of benzyl-type DES pretreatment and ball-milling pretreatment on the yield of SCB cellulosic ethanol,it was found that the benzyl DES pretreatment method has more advantages in increasing the ethanol production(16.84 g/L),which was 1.96 times more than the ball-milling SCB ethanol production(8.57 g/L).Moreover,after 5 cycles of use of the benzyl-type DES,although the cellulose conversion rate decreased from 88.23±1.24%to 68.02±2.41%,it was still about 175%higher than that of untreated SCB.Finally,to realize the functional application of the"three-component",this paper directly applied the the unchemically modified DES-L to the methylene blue(MB)dye adsorption field.The research results show that the process of DES-L adsorption of MB has the characteristics of large adsorption capacity and fast diffusion rate.The removal rate of low-concentration MB solution(48.82 mg/L)reached 93.55%after 60 min of adsorption.The adsorption process conforms to the pseudo-second-order kinetic model and the Redlich-Peterson adsorption isotherm model,and the maximum adsorption capacity was fitted at 313 K to be 85.16 mg/g.Electrostatic attraction and hydrogen bonding interaction are the main mechanisms for DES-L to adsorb MB.This study confirmed that benzyl DES is an efficient pretreatment solvent,providing a new way for the development of"three-component"functional utilization.