Cellulose Based Porous Materials Constructed By High Internal Phase Pickering Emulsion Template Method And Its Application

The rapid development of industry promotes social progress,but also brings great pressure to environmental protection.The treatment and discharge of industrial sewage is a very important part of it.Porous materials have great advantages in wastewater treatment due to their high specific surface area,light weight and recycling advantages.Pickering emulsion template method shows great potential in the preparation of porous materials.Compared with other preparation methods,Pickering emulsion template method has the advantages of adjustable pore size,large specific surface area and synergistic effect between internal structures.Pickering emulsions are obtained by using ultrafine solid particles as emulsifiers.The ultrafine solid particles used are required to have a certain amphiphilicity,which can replace traditional small molecule surfactants.During the preparation of Pickering emulsion,the selection of solid particles is particularly important.Cellulose nanocrystal（CNC）is a kind of nanoparticle extracted from natural biomass widely existing in nature by chemical oxidation or mechanical method to remove the amorphous region of Cellulose.As a typical amphiphile biomass nanoparticle,CNC has the advantages of large specific surface area,good biocompatibility,flexible aspect ratio adjustability and wide sources,which makes it play an important role in the preparation and application of Pickering emulsions.Manganese dioxide（MnO₂）has a good catalytic oxidation capacity,but the functionalization of its nanoparticles is limited by its easy aggregation and poor dispersity.Considering the above problems,we used cellulose nanocrystalline loaded manganese dioxide as a solid particle to stabilize the Pickering emulsion with high internal phase and then prepared porous materials.Manganese dioxide was loaded onto the surface of nanocrystals（CNC/Mn O₂）,which realized uniform dispersion and provided more binding sites for subsequent functionalization.Meanwhile,the hydrophilicity and hydrophobicity of nanocrystals were also changed,which was conducive to the formation of stable Pickering emulsion with high internal phase.Considering the recycling and reuse of porous materials,their structural stability is particularly important.We use both ionic crosslinking and free radical crosslinking to improve the structural stability of the material itself and ensure that it can play an optimal role in application.Finally,the adsorption capacity of cellulose nanocrystals is combined with the catalytic oxidation capacity of mno₂,which is applied to the post-treatment of industrial wastewater cotton pulp black liquor to give full play to the best effect of porous materials.The main research results of this paper are as follows:The first part:CNC/MnO₂ prepared in one step by potassium permanganate oxidation method was used as the main raw material,and a small amount of sodium Alginate（SA）and Poly（vinyl alcohol）were used.PVA)to stabilize n-hexane（N-hexane）to prepare Pickering emulsions with high internal phase.The effects of different experimental conditions on the stability and volume of inner phase of emulsion were investigated.After that,a continuous extrusion device was used to drop Pickering emulsion foam into calcium chloride solution,and the initial gelation was achieved by ionic crosslinking technology to maintain the shape.Further free radical crosslinking was achieved by acrylamide polymerization under alkaline conditions to enhance the structural stability.Finally,CNC/MnO₂ porous materials were obtained by solvent replacement with tert-butanol and freeze drying.The test results showed that the volume of Pickering emulsion with high internal phase could reach 78%,the droplet size ranged from 10μm to 30μm,and the emulsion structure was stable.CNC/Mn O₂ porous material is honeycomb inside,and has a high specific surface area.The second part:the function and stability of porous materials in the post-treatment of cotton pulp black liquor were investigated through various indicators of water pollution.The results show that CNC/Mn O₂ porous materials have a good ability to treat water pollution due to the high porosity and specific surface area of porous materials and the synergistic effect of electrostatic adsorption of cellulose nanocrystals and oxidative degradation of Mn O₂ in the system.In a short period of time,the decolorization rate of cotton pulp black liquor can reach 98.7%,TOC reduction rate reaches 81.1%,COD reduction rate reaches 97.3%,BOD reduction rate reaches 95.7%,and the porous material can maintain good structural stability and has good recycling property during three cycles.