Regulation Of Structure Of Regenerate Cellulose Materials And Application In Water Treatment

As an indispensable natural resource,water is the bedrock for human life.However,as the development of industrialization,the increase of population and the depletion of the natural resources,the water shortage is becoming a worldwide issue.How to acquire and reuse water still remains a challenge.Besides,the water contamination should also not be ignored,due to the increasing industrial wastewater,domestic sewage and other pollutant poured into rivers,lakes and seas.Cellulose as the most abundant nature polymer on earth exists widely in plants and bacteria.Its biodegradability,biocompatibility,environmental friendliness,non-toxicity and availability makes it the ideal candidate for constructing functional material,in the fields of photoelectromagnetic material,catalysis and water treatment.However,cellulose is difficult to melt or dissolve due to the massive intramolecular and intermolecular hydrogen bonds.A series aqueous solvents were developed which dissolve rapidly cellulose,and various functional materials were fabricated such as microspheres,membranes,fibers,hydrogels and so on.However,the regulation of cellulose structure via the regeneration process is still uncovered.In the present thesis,a series of electrolyte aqueous solutions were used as poor solvent to regenerate cellulose,and further to control the structure and properties of the regenerated cellulose.A series of characterization methods were performed to study regenerated cellulose structure and property,such as tensile test,scanning electron microscopy?SEM?,wide angle X-ray diffraction?XRD?,Fourier transfer infrared spectroscopy?FT-IR?,transmission electron microscopy?TEM?,X-ray photoelectron spectroscopy?XPS?,UV-vis spectra,contract angle.The relationship between cellulose structure and performance of cellulose-based functional material was demonstrated.Meanwhile,the application prospect of the regenerated cellulose materials in water treatment was also evaluated,suggested great potentials.The main innovations of this thesis are as follows:?1?a series of electrolyte aqueous solutions were used as poor solvents to regenerate cellulose,and the structure and performance of the regenerated cellulose were successfully controlled.The electrolytes had dehydration effect with different extent on the solvated cellulose chains,led to regenerated cellulose with different aggregated state structure.Then,regenerated cellulose with different mesh size were used as matrix to support gold nanoparticles to catalytically reduce the organic pollutant,and a linear relationship was found between mesh size of cellulose and catalytic performance of gold.This work provided a new method to improve the catalytic performance of the immobilized nanoparticles;?2?cellulose hydrogel with high strength was prepared as hydrophilic coatings on stainless mesh to prepare highly efficient oil/water separation material.The coating was super hydrophilic/super hydrophobic under water.The material exited high separation efficiency,high water flux and stability when separated water and oil included soybean oil,decane,petroleum ether and toluene.The materials still remained high separation efficiency with the presence of electrolyte with high concentration,indicating wide application prospect in water treatment.The main contents and conclusions of this thesis include the following part.A series of electrolyte aqueous solutions as poor solvent were used to regenerate cellulose and the structure of regenerated cellulose is controlled,following the Hofmeister series.Electrolytes can control the mesh size and tensile strength of the regenerated cellulose films.The ions dehydrated the solvated cellulose chains with different extent,which further affected the aggregated state structure of the regenerated cellulose.Furthermore,the gold nanoparticles were immobilized on the cellulose films and the mean diameter of the gold nanoparticles was about 1.6 nm and no obvious difference were observed when using cellulose matrix with different structure,indicating the matrix structure had no influence on the gold size.When catalytically reducing 4-nitrophenol,composite catalysts with different matrix structure had different catalytic performance.Specifically,the bigger the mesh size of cellulose films was,the higher the turnover frequency?TOF?was obtained,and a linear relationship between mesh size of the cellulose and TOF was observed,since larger mesh size favored the contact between the reactant and substrate.Cellulose hydrogel with high compressive strength were prepared by regenerating in LiBH₄ aqueous solution as coagulation.The compression strength can be modulated between 7.91 to 14.45 MPa via changing cellulose concentration and coagulation concentration.The cellulose hydrogel was further used as super hydrophilic coating and cellulose hydrogel coated stainless mesh as highly efficient oil/water separation material was fabricated.The resultant mesh was super hydrophilic/super hydrophobic under water.The separation efficiency reached 98.89,99.36,99.43 and 99.96%,respectively,for the mixture of water and oil including soybean oil,decane,petroleum ether and toluene.Besides,the flux reached 38064.30 L m^-22 h^-1.Furthermore,the mesh retained high separation efficiency in salty environment and remained excellent reusability,thus having broad application in practical oil/water separation.This thesis demonstrated that the electrolytes aqueous solutions can be used as poor solvent to regenerate cellulose and to control the structure and performance of the regenerated cellulose.Furthermore,the potential applications of the resultant cellulose materials in the field of water treatment is demonstrated,exhibiting great potentials.These basic researches provided scientific evidence and academic value for research and development of cellulose,which are in accordance with sustainability.Therefore,this thesis exhibits scientific significance and application prospect.