Study On The Comprehensive Utilization Technology Of Lignocellulose From Rice Straw With High Cadmium

In this research, we chose the rice straw with different cadmium content as raw material to study the relationship between pretreatment methods and cellulose hydrolysis efficiency, and the technology of making cellulose membrane. The main results are as follow:1、The cellulose hydrolysis efficiency of rice straw without pretreatment was very low. However, the cellulose hydrolysis efficiency was improved significantly after pretreatment. After hydrolysis with cellulase of350U for72h, the cellulose hydrolysis efficiency of rice straw residues from pretreatment with acid-alkaline was about1.16times higher than that of rice straw, from pretreatment with acid-alkaline and ionic liquid was1.7times higher than that of rice straw.2、 The pretreatment with the acid-alkaline compounds or with ionic liquid compounds after acid-alkaline treatment destructed the internal structure of lignocelluloses, broked the lignocellulosic crystal structure and the chemical bonds among different components, thus increased the surface area of cellulose and the contact area with enzyme, finally improved the cellulose hydrolysis efficiency and glucose conversion rate.3、 Using rice straw without or with cadmium content of2mg·kg-1and8mg·kg-1as stock materials, the cellulose hydrolysis efficiency of rice straw contained cadmium was lower than that of rice straw without cadmium. The higher cadmium content in rice straw, the lower hydrolysis efficiency. After hydrolysis with cellulase of350U for72h, the glucose yield from rice straw with cadmium content of2mg·kg-1was38.45g·kg-1less than that from rice straw without Cd, and from rice straw with8mg·kg-1was43.71g·kg-1less than that from rice straw without Cd.4、After rice straws with different cadmium concentration were treated by integrated pretreatment methods of sodium hydroxide and peracetic acid (PAA), their cellulose hydrolysis efficiencies were all increased. The higher concentration of cadmium in the original sample, the higher the hydrolysis efficiency. After hydrolysis with cellulase of350U for72h, the glucose yield of straw residue from straw containing2mg-kg"1of cadmium was1.85times higher than that from straw without cadmium, and from straw containing8mg·kg-1of cadmium was2.14times higher than that from straw without cadmium.5、Using rice straw pretreated by sodium hydroxide and PAA as the stock material, and adding cadmium of2mg·L-1and8mg·L-1into the enzymolysis liquid respectively, a positive correlation between the content of cadmium in the enzymolysis liquid and the glucose yield of rice straw cellulose was found. For example, after enzymolysis for24h, the glucose yield of rice straw cellulose in enzymolysis liquid with cadmium of8mg·L-1was above30%higher than that without cadmium. It indicates that cadmium has activation effect to cellulase.6、 The removal effect of cadmium from rice straw was changed with different pretreatment methods. The pretreatment by sodium hydroxide did not significantly influence the cadmium content in rice straw. But the pretreatment by PAA decreased the cadmium content in the slag of rice straw by more than80%, the compounded pretreatment by sodium hydroxide and PAA decreased the cadmium content in the slag of rice straw by more than90%, which indicated that cadmium in rice straw could be removed by the PAA, and the combined technology had a more significantly effect.7、 The different ionic liquids had different effect on the dissolution of cellulose. Among them,1-ethyl acetate-3-methy1-imidazole salt was the best ionic liquid for making cellulose membrane. In the process of vacuum drying for6h,45℃was the best ideal temperature.