| Biomass resources are the first natural resources directly applied by humans.With the progress of human civilization,the application research of biomass resources peaked before and after the Second World War,and then gradually declined with the development of petrochemicals and coal chemical industry.Since the mid-1970 s,the excessive exploitation and use of fossil resources,as well as the growing environmental problems,have once again focused on biomass resources in an effort to find alternatives to fossil resources.In this study,biomass-based green degradable membrane materials were prepared from Dendrocalamus sinicus with characteristics in southwest China,which provided a reference for the high value utilization of bamboo-based materials in food packaging and sewage treatment.Based on 1-methylimidazole/dimethyl sulfoxide(NMI/DMSO)dissolving system,the bamboo powder was dissolved and chemically modified,and the whole component of cell wall of Phyllostachys praecox was modified by acetylation in homogeneous system,which was used to prepare membrane material,The properties of the material were adjusted to enhance its mechanical properties,antibacterial and photocatalytic selfdegradation ability,and to expand the application range of the material.The raw materials and the prepared membrane materials were analyzed and investigated by means of infrared spectrum analysis,scanning electron microscope(SEM),universal ability machine,UV-vis analysis and so on.The raw material of Dendrocalamus sinicus collected by laboratory was selected as raw material,benzene alcohol was extracted and dewaxed,and the powder of Dendrocalamus sinicus after ball milling was dissolved in NMI/DMSO solvent system at room temperature for pretreatment.Then the structures of cellulose,hemicellulose and lignin were studied by dioxane separation,and the structures of the three components were compared.The results of infrared spectrum analysis showed that the waveforms and characteristic peak positions of infrared spectra of cellulose,hemicellulose and lignin were basically the same,and the structure of cellulose,hemicellulose and lignin did not change obviously.The hemicellulose and lignin with more complex structure were further characterized by two-dimensional nuclear magnetic spectroscopy,and the signal peaks on two-dimensional nuclear magnetic spectrum were also observed to be basically the same.Moreover,the starch-like polysaccharide crosslinked with hemicellulose was broken after pretreatment with dissolution system,and the purity of hemicellulose was higher.The results showed that NMI/DMSO dissolution system could gently promote the dissolution of bamboo components,and could remove the impurities crosslinked with hemicellulose components,and could not obviously destroy the chemical structure of the major components of bamboo cell wall.The rationality of selecting NMI/DMSO dissolution system was determined by eliminating the experimental interference factors,which laid a foundation for the preparation and performance research of membrane materials in the future.Adding excessive acetic anhydride to the NMI/DMSO solvent system dissolving bamboo powder,acetylation of the whole component of Dendrocalamus sinicus is carried out to prepare a membrane material,and a plasticizer polyethylene glycol is introduced to modify the performance of the membrane,The effects of modified reagents on the structure and properties of the membrane were studied.The results showed that the contents of lignin,cellulose and hemicellulose were 22.3%,63.2% and 13.6% respectively.All three main components are utilized.Scanning electron microscopy(SEM)showed that the surface of the membrane material prepared by acetylation of the whole component of Dendrocalamus sinicus was smooth,and the structure of the membrane material was more compact after adding polyethylene glycol.The results of mechanical properties measurement and analysis show that the tensile strength and elongation percentage of the membrane increase with the increase of plasticizer polyethylene glycol content.when 50% polyethylene glycol is added,the mechanical properties of the membrane are the best.The tensile strength was 2.1% at 13.7 MPa,the tensile strength was increased by 168%,and the elongation was increased by 250%.The membrane without any additives can be well isolated from ultraviolet light.after adding polyethylene glycol,the transmittance of the membrane increases with the increase of polyethylene glycol content,and the hydrophilicity becomes better.In order to expand the application of the whole component membrane material,the antibacterial properties of the membrane material before and after silver loading were studied by using silver nitrate as silver source and common bacteria in air and soil as experimental bacteria.The successful loading of silver particles was verified by X-ray diffraction pattern.Compared with the unloaded silver substrate,the tensile strength and elongation of the film were increased by 13.7% and 36.6%,respectively.UV spectrum analysis showed that the transmittance of the material decreased with the addition of silver particles.From the results of antibacterial properties,it can be seen that silver-loaded antibacterial membrane has different degrees of inhibitory effect on different kinds of bacteria.In the experiment,among several kinds of bacteria commonly found in the air and soil,the antibacterial membrane has obvious inhibitory effect on Bacillus brevis.In order to study the self-degradation ability of the material,titanium dioxide and silver were added to the material to study the photocatalytic self-degradation performance of the film,and the absorption and utilization of light by titanium dioxide doped with silver were compared.Scanning electron microscope(SEM)surface image showed that the surface of the prepared film material was smooth and molded effectively.After irradiation under ultraviolet light for two hours,the film without photocatalyst degraded only a small part of the surface layer,and after adding titanium dioxide,Obvious cracks can be seen in the film surface diagram.after doping silver particles with titanium dioxide,the photocatalytic self-degradation performance of the membrane material is the best,which has destroyed the structure of the film and showed a flaky uneven structure.The characteristic peaks of silver and titanium dioxide can be seen in the XRD diagram,indicating the successful loading of the photocatalyst in the material,while the addition of the photocatalyst can be clearly seen in the UV-vis spectrum.The absorption efficiency of UV and visible light was improved obviously.due to the improvement of silver on titanium dioxide photocatalysis,the composite film doped with silver and titanium dioxide had the best photocatalytic self-degradation performance.Through the analysis of mechanical properties,it was also found that the mechanical properties of polyethylene glycol-titanium dioxide-silver composite membrane decreased the most obviously,the tensile strength decreased by 51%,the elongation decreased by 51.2%,the photocatalytic self-degradation performance was the best,and the utilization ratio of light absorption was the highest.In addition to the improvement of photocatalytic utilization rate,the composite film with silver and titanium dioxide was added,and the maximum improvement of additional properties was obtained.the tensile strength and elongation were increased by 116% and 136%,respectively. |
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