Preparation And Properties Of Electrospun CNC/CS/PVA Composite Nanofibers

In this study,the cellulose was used as a raw materials,and cellulose nanocrystals(CNC)with controllable morphology were prepared by optimizing the acid hydrolysis conditions in this study.Then,the CNC reinforced chitosan/polyvinyl alcohol(CS/PVA)nanofibers were prepared by introducing the morphology controlled CNC using electrospinning techonology.The mechanism of interaction between CNC and composite nanomaterials was studied and the optimal spinning process parameters were explored.And then,the surface of this nanofibers was chemically modified.To broad the application fields of electrospun composite nanofibers,the metal ions adsorption behavior and the kinetic equation of the modified electrospun materials were evaluated.The main research contents and results are as follows:(1)In order to prepare a high crystallinity CNC with controlled microstructure,the microcrystalline cellulose(MCC)was hydrolyzed using 64 wt%sulfuric acid by two process conditions(constant temperature,constant temperature after pre-reaction).The results showed that the better diameter distribution of CNC was obtained with pre-reaction,the average diameter was 7 ± 4 nm,the average length was 106 ± 22 nm.XRD results show that different hydrolysis methods have a significant impact on the crystallinity of the obtained CNC,while the drying method has no effect on the crystallinity of the obtained CNC.(2)To prepare the CNC/CS/PVA composite nanofibers,the optimal parameters of electrospun were studied.The SEM results showed that the better fiber morphology was observed when 3wt%CS and 12wt%PVA spinning solution were blended into a 60:40 mixed spinning solutions.The nanofibers diameter non-uniformity and roughness showed a rising tendency along with the increasing concentration of CNC(3,5,10,and 20wt%under the same spinning conditions,the addition of a small amount of CNC can improve the mechanical properties of the nanofibers effectively.Thermal stability was significantly improved with the increasing of CNC addition.The stability of the composite nanofibers in aqueous solution has nothing to do with the content of CNC,but it gradually improves with the weakening of acidity.(3)To increase the adsorption active sites on nanofibers,the above electrospun CNC/CS/PVA composite nanofibers were chemically modified using thioacetic acid.FTIR results show that the electrospun CNC/CS/PVA composite nanofibers have been successfully functionalized with thiols,and the modified composite nanofibers have a certain pH-responsiveness.The electrospun nanofibers has a cross-linked porous film structure in the weak acid solution.In the higher alkali solution,the individual fibers in the electrospun material can retain its original microstructure of unmodified.(4)The electrospun CNC/CS/PVA-SH composite nanofibers were applied to the adsorption-desorption experiments of Cu(?)and Pb(?)ions.The experimental results show that the optimal adsorption capacity was obtained when the CNC content was 5wt%and pH was 6.The adsorption behavior of Cu(?)and Pb(?)ions on the composite membranes were in accordance with the second-order kinetic equation.Based on the Langmuir equation,the maximum adsorption capacity for Cu(?)and Pb(?)ions were estimated to be 162.76 and 215.19 mg/g,respectively.After four adsorption-desorption cycles,the adsorption efficiencies of Cu(?)and Pb(?)on the electrospun materials were 90.58%and 90.21%,respectively.In summary,the prepared CNC extractedfrom wood can significantly improve the microstructure,thermal properties,mechanical properties,and metal ion adsorption of electrospun composites due to its unique physical and chemical properties.This study has further broadened the application of CNC,which has important practical and guiding significance for the development of various properties of electrospun nanocomposite fibers.