Study On Isolation,characterization And Application Of Chemical Components From Camellia Oleifera Nut Shell

Camellia oleifera is an important economic crop in China.A large amount of wastes will be produced at the same time as the oil is squeezed out.Among them,the quality of the Camellia oleifera nut shell(CONS)accounts for more than 60%of the total mass of Camellia oleifera fruit.Our research group has separated and extracted the polysaccharides and tea saponins from the CONS,and applied them to the research of antibacterial properties,antioxidant activity and flame retardant coatings,etc.,and achieved obvious results.Nevertheless,the CONS also contains a large number of macromolecular components such as cellulose,hemicellulose,and lignin,and there are relatively few studies on these components.In this thesis,the common CONS is taken as the research object,and the cell morphology and chemical constituents,especially the separation and structural identification of cellulose,hemicellulose and lignin,of CONS are systematically studied.And then the applications of CONS are discussed.The results have provided a theoretical basis for efficient utilization and high-quality development of CONS.The cell morphology,chemical composition,fiber properties were firstly carried out and the separation and chemical characterization of hemicellulose and lignin in CONS were also discussed.The results showed that the lumen of CONS was large and the cell wall was thin;the CONS had lower content of fiber(21.83%),higher content of lignin(31.87%),pentose(29.2%),and extractives.The separated CONS fibers were pure,and their chemical structure and crystalline morphology were similar to those of softwood fibers.The fiber length of CONS was in a range of 0.5 to 1.25 mm and the fiber width was in a range of 45 to 100μm.The main components of CONS hemicellulose were xylose and arabinose.FTIR and H~1-NMR results revealed that the CONS lignin belonged to GS-type lignin.In terms of technical research,CONS was used to prepare pulp through the preserved lignin method for producing corrugated base paper,which could partially replace the wood raw materials.The results showed that CONS was not suitable for chemical pulping,but when semi-chemical pulping was performed(that is,partially retained lignin pulping),higher yields and good pulp properties could be obtained.The optimal semi-chemical pulping technologies were as follows:1)chemical pretreatment:Na OH dosage,8-12%,AQ dosage,0.03-0.05%,solid-liquid radio,1:4-1:6,the highest cooking temperature,150-155℃,heating time,60-75 min,holding time,45-60 min;2)mechanical refining stage:first refining stage,medium consistency 8-12%,refiner gap,0.5-1.0 mm,second refining stage,low consistency 3-5%,refiner gap,0.05-0.25 mm.The semi-chemical pulp of CONS can be used for the production of corrugated base paper,and the B-grade corrugated base paper(Chinese standard)could be satisfied when the content of semi-chemical pulps of CONS was below 40%instead of recycled pulps.This process provided a new way to broaden the source of pulping raw materials.Due to the hydroxyl groups in cellulose,hemicellulose and lignin in CONS,a full-component modification method was used to prepare heavy metal adsorption materials by CONS,which provided a new idea for the conversion of husk substances into environmental adsorption materials.The results showed that the ethanol/Na OH modified CONS(MCONS)had higher Cu(Ⅱ)and Cr(Ⅵ)uptake than CONS sample due to the more carboxyl group content,higher porosity,and surface area.The adsorption capacity of Cr(Ⅵ)and Cu(Ⅱ)by MCONS was 15.55 mg/g and 25.80 mg/g,which were significantly higher than those of CONS(5.95 mg/g and 9.46 mg/g,respectively).The adsorption of Cr(Ⅵ)and Cu(Ⅱ)by MCONS is mainly chemical adsorption,and the adsorption kinetics fit well with the pseudo-second-order kinetic model.Adsorption thermodynamics results demonstrated that the adsorption process was spontaneous and exothermic.Increasing the temperature is not conducive to the adsorption of heavy metals.Analysis of the adsorption isotherm curve showed that the adsorption process of Cr(Ⅵ)and Cu(Ⅱ)by MCONS is consistent with the Langmuir isotherm adsorption.In order to improve the application level of natural cellulose in CONS,a traditional acid method was used to prepare rod-like cellulose nano-crystals(CNCs)with an average particle size of 134.6 nm,Zeta potential of-38.1 m V and charge density of 0.289 mmol/g.After CTAB(hexadecyltrimethylammonium bromide)modification,CONS-based CNCs can be used as a carrier of forest-derived active substances for loading the water-insoluble active ingredient,such as curcumin.TEM and XRD results showed that after being loaded with CTAB modified CNCs,curcumin was fully nanonized and transformed from crystalline to amorphous.The dissolution and antioxidant properties of curcumin were significantly improved.MTT evaluation,cell morphology,and flow cytometry apoptosis of Hep G2 hepatocellular carcinoma cells showed that the anticancer effect of curcumin in the water system was greatly increased after being loaded with CONS-based CNCs.The traditional water extraction method was also used to isolate tannins from the CONS and its antioxidant properties were analyzed.Studies have shown that 7.42%of tannin could be extracted from CONS with the optimal conditions of extraction time 75min,solid-liquid ratio 1:40,extraction temperature 80℃,with ultrasound-assisted.The extracted tannin had strong antioxidant activity.When the amount of tannin was 0.8mg/m L,the hydroxyl radical scavenging rate was 82.23%.When the amount of tannin was0.2 mg/m L,the DPPH radical scavenging rate was 92.64%.