| Cellulose Nanocrystals(CNCs),as a kind of biomass nanomaterials with broad application prospects,have been widely used in various fields.Due to their low density,good mechanical properties,large specific surface area,and easy surface modification,cellulose nanocrystals have unparalleled enhancement performance as other bio-polymer reinforcement phases.Introducing nanocellulose into hydrogel can obtain more excellent performance than traditional hydrogel.To this end,in this thesis bamboo powder has been used as a raw material to prepare cellulose nanocrystals(CNCs),and then CNCs were introduced them into a hydrogel constructed from acrylic acid(AA)and acrylamide(AM)to successively prepare CNC-g-P(AA/AM)hydrogel and CNC-PAA/P(AA/AM)hydrogel.The main research contents were as follows:(1)Taking bamboo powder as raw material,removing all kinds of impurities in bamboo powder through pretreatment,obtaining cellulose,and preparing cellulose nanocrystals(CNCs)by sulfuric acid hydrolysis method,and then calculating the solid content and yield of CNCs.The prepared CNCs were characterized by ζ-potential measurement,elemental analysis(EDS),infrared spectroscopy(FT-IR),transmission electron microscopy(TEM)and thermogravimetric analysis(TG).The results show that the prepared CNCs had a high surface charge(-38.7m V),so its suspension has good stability.There are sulfonic acid groups on the surface of the CNCs,and the content of sulfonic acid groups on the surface was calculated to be 0.32 mmol·g-1based on the results of elemental analysis.TEM images show that the average length of CNCs was 141.3 nm.(2)The cellulose nanocrystal-g-poly(acrylic acid-co-acrylamide)(CNC-g-P(AA/AM))hydrogel with excellent adsorption properties was prepared by graft polymerization on the surface of CNCs.Infrared spectroscopy(FT-IR),elemental analysis(EDS),scanning electron microscopy(SEM)and transmission electron microscopy(TEM)were used to characterize CNCs and CNCg-P(AA/AM),and their adsorption performance was studied using inductively coupled plasma emission spectroscopy(ICP)to examine its adsorption kinetics,adsorption isothermal behavior,adsorption mechanism and reproducibility.Finally,using hydrochloric acid as a desorption agent,the reproducibility of CNC-g-P(AA/AM)hydrogel was investigated.The results showed that the adsorption of Pb(II)on CNC-g-P(AA/AM)hydrogel was chemical adsorption and monolayer adsorption,and the theoretical maximum adsorption capacity can reach 366.3 mg·g-1.At the initial concentration of 200 mg·L-1,the removal rate of Pb(II)by the gel was over 95%,and it can still maintain good adsorption performance after 4 adsorption-desorption cycles.(3)Prepared polyacrylic acid grafted cellulose nanocrystals(CNC-PAA)through polyacrylic acid molecular chain grafted on the surface of CNCs by graft polymerization.Acrylamide(AM)and acrylic acid(AA)monomers were added to a suspension of CNC-PAA at a certain concentration,polymerized to form a gel,and treated with ferric chloride solution to prepare CNC-PAA-reinforced poly(acrylic acid-co-acrylamide)CNC-PAA/P(AA/AM)hydrogel.During the experiment,infrared spectroscopy(FT-IR),transmission electron microscopy(TEM),and scanning electron microscopy(SEM)were used to characterize the hydrogel.Finally,the mechanical properties of the hydrogel were tested using a universal testing machine.The test results showed that the hydrogel prepared by this method had excellent mechanical properties,tensile strength up to 7.32 MPa,and elongation at break up to 1400%.In addition,the hydrogel had a good shape recovery ability,and it can still recover the deformation in a shorter time after undergoing more than 95% compression deformation. |
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