Preparation And Study Of Cationic Flocculant By Rice Straw Lignin

Six million tons crop of straw is produced in China every year.But most of them is burned without being utilized,and severe environmental pollution and the waste of biomass resources are resulted.It is practical significance for agricultural production to study and utilize crop straw.Lignified cell wall can prevent the degradation of straw by microbes,so the isolation of lignin makes it more easy to utilize straw cellulose. Lignin was a kind of complex aryl compound with multidimensional mesh structure and a large amount of active functional group,and lignin flocculant can be produced by the modification of it.The liquid and solid ratio (m/m),mass fraction of glycol aqueous solution,reaction temperature and time,which influenced the isolation of lignin from rice straw in autoclave were mainly studied.The optimal technical conditions were resulted when the liquid and solid ratio (m/m) 12∶1,mass fraction of glycol aqueous solution 90%,reaction temperature 240℃and time 2.5h.The yield of lignin could reach 54.4%.The solvents can be reused repeatedly for many times after vacuum concentration.Lignin can be dissolved by most organic solvents,it indicated that glycol lignin contained more active hydroxyl groups.Aromatic structures of lignin were confirmed by IR and UV spectrum.X-ray powder diffraction analysis showed the amorphous structure of lignin.Cationic etherification lignin flocculant was prepared by the glycol lignin and N-(3-Chloro-2-hydroxypropyl)trimethyl ammonium chloride (CHPTAC) . The amount of Sodium hydroxide,CHPTAC,reaction temperature and time,which influenced the properties of flocculant were mainly studied.The optimal technical conditions were obtained as follows:sodium hydroxide amount 2mL,CHPTAC dosage 1.5 g,reaction temperature 60℃,reaction time 10h. The products were characterized by FT-IR,it was indicated that lignin was modified to be a quaternary ammonium salt.The flocculant product was applied to kaolin dispersions simulate effluent and tartrazine,ponceau 4R,reactive bright blue X-BR model dye effluent treatment.Under proper condition,the removal rate of turbidity by cationic etherification lignin flocculants on high turbidity kaolin dispersions simulate effluent reached 73.4%,the discoloring rates of the tartrazine,ponceau 4R,reactive bright blue X-BR model dye effluent treatment could reach 70.9%,68.8% and 94.2%,respectively.Grafting copolymerization cationic lignin flocculant was prepared by the glycol lignin , Acrylamide and Dimethyl Dially Ammonium Chloride (DMDAAC).The reaction temperature and time,initiator amount and mass ratio of lignin,Acrylamide and DMDAAC,which influenced the properties of flocculant were mainly studied.The optimal technical conditions were obtained as follows:reaction temperature 40℃, reaction time 8h , initiator amount 10mL ,lignin∶acrylamide∶DMDAAC (mass ratio) 1∶2∶1.The experimental results indicated that the grafting percentage and grafting efficiency were 227.5% and 75.8%,respectively.The products were characterized by FT-IR,it was indicated that lignin was modified to be a cationic compound.The flocculant product was applied to kaolin dispersions simulate effluent and tartrazine,ponceau 4R,reactive bright blue X-BR model dye effluent treatment.Under proper condition,the removal rate of turbidity by Grafting copolymerization cationic lignin flocculant on high turbidity kaolin dispersions simulate effluent reached 87.3%,the discoloring rates of the tartrazine,ponceau 4R,reactive bright blue X-BR model dye effluent treatment could reach 96.7%,98.2%,and96.4%,respectively.