Preparation And Performance Of A New Type Of Filter Paper Based On Ultralong Hydroxyapatite Nanowires

As the problems of water scarcity and water pollution become increasingly serious,water treatment technologies have aroused wide attention.Among them,membrane separation technology has the unique advantages such as high separation efficiency,low equipment requirements,and simple operation.The ideal separation membrane materials should have excellent environmental friendliness,versatility,high selectivity and fast filtration performance.How to enhance the separation efficiency of the membrane materials while further improving the water permeability is a big challenge.In this thesis,new kinds of porous filter paper are prepared by combining environmentally friendly ultralong hydroxyapatite nanowires with cellulose fibers.Compared with traditional filter paper,the new filter paper based on ultralong hydroxyapatite nanowires can achieve the separation of various pollutants,and its unique loose porous structure can significantly improve the permeability of water molecules.The main research contents are as follows:Multifunctional microporous filter paper is obtained by compounding hydroxyapatite ultralong nanowires with high beating cellulose fiber.The addition of polyamide-polyamine epichlorhydrin resin can significantly improve the wet mechanical strength of the membrane.The ultralong hydroxyapatite nanowires can give the composite filter paper a unique porous structure and super hydrophilicity,so the pure water flux of the filter paper under cross-flow conditions can reach 287.28 L m–2 h–1 bar–1.Hydroxyapatite ultralong nanowires can adjust the pore size distribution of composite filter paper within a narrow range,which is a typical microporous filter paper.Through the size exclusion and blocking effect,microporous filter paper can efficiently remove micro-nano particles and bacteria in water,and has a high adsorption capacity for methyl blue dye and Pb2+ ions.The ultralong hydroxyapatite nanowires are combined with cellulose fibers to obtain a porous substrate with high water flux,and the cellulose nanofibers are used to obtain a double-layer nanofiltration paper.Through cellulose nanofibers and microfibers,the effect of fiber size on the porous structure of hydroxyapatite ultralong nanowires was studied.The porous network formed by cellulose microfibers and hydroxyapatite ultralong nanowires can provide a large number of channels for water transport,and its pure water flux can reach 544.4 L m–2 h–1 bar–1.Based on cellulose microfibers and hydroxyapatite ultralong nanowires,the water flux of nanofiltration paper can be increased by 20%,the rejection rate of dye molecules can be maintained above 95%,and the nanofiltration performance for salt ions is excellent.The ultralong hydroxyapatite nanowires are combined with cellulose fibers and layered double oxide nanosheets to obtain a microporous filter paper for rapid dye filtration.The positively charged layered double oxide nanosheets can adsorb on the surface of negatively charged hydroxyapatite ultralong nanowires and embed in the porous structure of filter paper,providing a more porous structure for the transport of water molecules.With the increase of the composite amount of the layered double oxide nanosheets,the average pore diameter and bulk of the filter paper have gradually increased,and its pure water flux can reach 783.6 L m–2 h–1 bar–1.The layered double oxide nanosheets with high adsorption capacity for dye molecules make the rejection rate of the composite filter paper for Congo red reach 98.3%.The particle size of layered double oxide nanosheets plays a vital role in improving the water flux and separation performance of filter paper.