Preparation Of Concrete Superplasticizer Using Enzymatic Hydrolysis Lignin By Graft Sulfonation

Cellulose and hemicellulose in Lignocellulose are converted into sugar compounds toproduce biofuels and other chemicals by enzymatic hydrolysis. It is an alternative to ease theenergy crisis. A large amount of lignin residues are produced during the enzymatic hydrolysisof lignocelluloses and they are usually burned to provide heat, which is a low value addingapproach. The high value utilization of lignin residue is important to improve economicefficiency of biofuel production. In this paper, cornstalk and corncob enzymatic hydrolysislignin were used as raw materials to prepare superplasticizer by grafted sulfonation andcondensation.The effect of purification degree of raw material on the performance of products wasstudied. The results showed that the performance of products was highly affected by thecontent of cellulose. The raw material purified by alkali-acid pretreatment have the bestperformance.The synthesis process of superplasticizer with corncobs enzymatic hydrolysislignin(CEHL) was studied. The results showed that with the increase of Na2SO3, the intrinsicviscosity of products decrease gradually and cement fluidity first increased and thendecreased. The optimized process parameters were as follow: m(CEHL):m(B):n(S):n(F)=1:1:0.0095:0.036, reaction concentration was43%, sulfonation temperature was55℃,sulfonation time was1h, condensation temperature was95℃, condensation time was3h.The products prepared at the optimized process parameters had an intrinsic viscosity of9.43mLg·-1and cement fluidity of261mm with the dosage of0.5%and the water-cementratio of0.29. Compared with raw material, WR-EHL had higher S element content, itssulfonation degree was as high as2.17mmolg·-1. The weight-average molecular weight andnumber-average molecular weight of WR-EHL was19200gm·ol-1and3800gm·ol-1respectively. WR-EHL had better performance than Ls-1at different dosage and water-cementratio. With the dosage of0.8%, initial setting time and final setting time of cement weredelayed by260min and250min compared with control respectively. With0.6%dosage,water reducing ratio of mortar reached20.6%, the flexural strength ratio and compressivestrength ratio at3d,7d,28d were135%,120%,127%and145%,135%,141%, respectively.The compressive strength of concrete with WR-EHL at7d and28d reached40.8MPa and50.2MPa, which were8.2%and6.1%higher than Ls-1. The amount of mixing water of WR-EHL was slightly lower than Ls-1and air entraining performance of WR-EHL was better than Ls-1.The process of grafting reaction between polycarboxylate superplasticizer andlingo-sulfated plasticizer was studied. The optimized process parameters were as follow:m(MBL):m(PC) was1:1, reaction temperature was80℃, reaction time was2h, APS dosagewas0.50%and dropping speed was0.35mL·min-1. Under this condition, grafting reactionproducts of WR-EHL and PC had a better performance than the mixture of WR-EHL and PCat1:1ratio.