Wood-based Nanocellulose Filtration Of Ultrafine Particles And Its Water Purification Performance

At present,the problem of water pollution is becoming more and more serious.More than half of the countries and regions in the world lack clean water.Lignocellulosic nanocelluloses are found mainly in the cell wall of wood and have fine size of nanometer scale.At present,water purification materials based on lignocellulose have been developed for the removal of metal particles,bacteria and viruses in water,such as ultra-fine particles with sizes ranging from a few nanometers to a few microns.However,it is easy to block and the filtration speed is slow in the filtration and separation of ultrafine particles in water.In this study,a pressure-driven hydrogel filter of wood nanofiber and commercial porous membrane was prepared,the filtration and separation ability of the nanocellulose hydrogel filter for ultrafine particles in water and its application in water purification were also investigated.The main contents of this thesis are as follows:（1）The preparation of nanocellulose hydrogel composite membrane by uniformly covering a layer of nanocellulose hydrogel membrane on the commercial porous filter membrane with a needle filter;The nanocellulose-based hydrogel filter is composed of composite membrane and needle filter.The porous structure of the composite membrane is three-dimensional network.The porosity of the hydrogel membrane can reach over 95%,and the ultrafine particles with particle size over 10 nm can be effectively filtered and separated.The filtration efficiency of ultrafine particles can reach 100%and the average velocity can reach 90.6 g cm^-2 h^-1.The results of numerical simulation show that the trace of ultrafine particles stops before the composite film is formed,and water can pass through the composite film and accelerate downward flow.（2）The nanofiber hydrogel filter can filter and separate ultrafine particles in wastewater efficiently.The filter can effectively filter and purify muddy wastewater,melted snow water and ultra-fine particles in urban river water.The UV-vis spectra showed that the absorbance of the filtered filtrate tended to 0.Nanofiber hydrogels are biodegradable and can be completely degraded by soil in 100 days.In order to obtain a large amount of clean water in a short time,an improved filtering device was developed,which can continuously filter and separate nano-cellulose hydrogel filter（filter-L）.Filter-L effective filtration area of 1163.6 cm²,a filter can obtain 1016 g of clean water.The collected clean water is colorless and pure,and many water quality indexes meet the national drinking water standard（GB 5749-2006）.（3）To adjust the ultrasonic time and the amount of nano-cellulose suspension in the preparation process,and to study the preparation of nano-fiber hydrogel filter for the concentration of 0～1.0 mg/m L;Filtration and separation performance of polystyrene nano-plastics with diameters of 30nm and 50nm.Nanofiber hydrogel filter can effectively intercept polystyrene with diameter of 30nm and 50nm,whose concentration is less than 1.0 mg/m L after two times filtration,and the filtration efficiency can reach up to 99.9%.