Preparation Of Cellulose Nanocrystalline/Manganese Dioxide Porous Microspheres And Their Application In Water Treatment

Cellulose nanocrystals(CNC)are rod-like nanomaterials extracted from plant fibers.They have the advantages of large specific surface area,good biocompatibility,and easy surface modification.Hydrogel microspheres or microspheres based on cellulose nanocrystals(CNC)/metal oxide hybrid materials not only have the ability of simultaneous adsorption and degradation,but also have the characteristics of easy separation and recovery,so they have a broad application prospect in the treatment of dye wastewater.However,the relatively small porosity and specific surface area limit the adsorption capacity of microspheres.In this work,we use the CNC surface loaded manganese dioxide(MnO₂)(CNC/MnO₂),which prepared by potassium manganese oxide oxidation method as raw material,with sodium alginate,using the air bubble template and the principle of ion crosslinking,to prepare honeycomb CNC/MnO₂/SA porous microspheres.And systematically studied its adsorption and catalytic degradation of organic pollutants,the main research results of this paper are as follows:The first part:CNC/MnO₂ prepared in one step by potassium permanganate oxidation method is used as the main raw material,together with a small amount of sodium alginate(SA)and sodium dodecyl benzene sulfonate,SDBS)using air bubble template method and ion crosslinking technology to prepare CNC/MnO₂ porous microspheres with different foaming rates.By exploring the foaming process and further adjusting the stirring time,CNC/MnO₂/SA type emulsion foams with different foaming rates were obtained.Using the ion crosslinking technology,a continuous extrusion device was used to drop emulsion foams into the calcium chloride solution to form CNC/MnO₂/SA hydrogel microspheres.CNC/MnO₂/SA porous microspheres with different foaming rates were obtained by freeze-drying technique.The results showed that the CNC/MnO₂/SA microspheres were honeycombed with a pore size of 100-150?m,a porosity of 98%,and a high specific surface area.The second part:The decolorization effect of methylene blue(MB)in porous spheres with different foaming ratios was investigated by an ultraviolet spectrophotometer system.The results show that CNC/MnO₂/SA porous microspheres with a foaming rate of 2 have excellent dye-decolorization performance thanks to the synergistic effect of the high porosity of porous microspheres and the ability of CNC electrostatic adsorption and MnO₂ oxidation degradation.After batch decolorization experiments,using 200 mg CNC/MnO₂/SA porous microspheres decolorization 30 m L MB solution with a concentration of 800 mg/L,the dye removal rate reached 95%within10 min,and the equilibrium decolorization amount reached 114.5 mg/g.The decolorization mechanism was explored,and the ratio of adsorption and degradation in the decolorization process was characterized by desorption experiments,and the degradation rate was 88%.At the same time,it has good recycling ability.The third part:Taking the wastewater of cotton pulp plant as the research object,the ability to treat industrial wastewater with porous microspheres was systematically tested by detecting the chroma and COD value of wastewater.The results show that the untreated wastewater has chroma of 6698 pcu and a COD of 14321 mg/L.The treated wastewater has a chroma of 11.2 pcu and a COD of 165 mg/L,which meet the national standard of sewage discharge.At the same time,the porous microspheres are well tolerated and can be used over a wide pH range.