Fabrication Of Paper-Based Hydrophobic/Oleophilic Materials And Application In Oil Water Separation

The oil leakage and the discharge of industrial oily wastewater have alwayls threatened the ecological environment and human being health.In the field of automobile,the heavy duty diesel engine is particularly high demands on the purity of product,because the current mainstream of the high pressure common rail diesel engine,if small amount moisture is contained in diesel oil,it will transferred into emulsified water oil mixture under the shear of high pressure oil pump,emulsified particle size is usually between 0～60μm,which can corrode and block plug nozzle,effect the oil supply system,damage the engine,resulting in economic losses.Therefore,it is necessary to use technically feasible and economically applicable oil-water separation materials to separate water from diesel oil.In the past decades,scientists have introduced special wettability theories into the field of oil-water separation,such as the concepts of superhydrophobicity-superhydrophilicity,and superhydrophilicity-underwater superhydrophilicity.By using the different wettability of oil and water phase related to material surface,appropriate oil-water separation materials are selectively chosen to achieve efficient separation.The main factors affecting the surface wettability are surface roughness and surface chemical composition.For example,the oil removing type of materials,which need to introduce low surface energy chemicals,such as fluorine,silane or long chain alkyl hydrocarbons to achieve hydrophobic-oleophilic performance;For water removing type of materials hydrophilic hydro-gel or other groups need to be introduced.The roughness of the surface of the material can be constructed by introducing micro-nano particles.If necessary,adhesives should be added to fix the roughness.By improving the surface roughness,the wettability of the material surface can be amplified.This thesis mainly focused on the preparation of the base of oil-water separation materials,the construction of surface roughness,the synthesis of adhesives and the design of low surface energy materials.In order to design reasonably,economically and feasible materials with excellent performance,we have done a lot of tentative work as followed:We mainly constructed the micro/nano materials,hydrophobic adhesives and low surface energy chemicals.Firstly,superhydrophobic particles of calcium stearate were prepared by the reaction of Ca（OH）₂ with stearic acid.Then,cellulose stearyl ester with a degree of substitution of 0.67 was obtained by the reaction of dissolved pulp cellulose and stearyl chloride in homogeneous conditions,which had adhesive and hydrophobic properties at the same time.The dry strength increased 1.8 times at 2%coating amount,and the water contact angle was 97°.The hydrophobic oil-water separation membrane with water contact angle of 147°was obtained by bonding calcium stearate particles onto the surface of filtration base paper by hydrogen bonding between adhesive and filter paper.The oil-water separation efficiency was tested and the separation efficiency of kerosene,dichloromethane,trichloromethane and other oily substances was all more than 99%,and the oil-water separation membrane can maintain high hydrophobicity in a variety of destructive experiments such as water washing,acid-base immersion and high temperature environment.The superhydrophobic cellulose based micro/nanoparticles were synthesized,and starch was used as adhesive.Firstly,dissolved pulp cellulose was dissolved in DMAC/Li Cl solution,triethylamine was used as catalyst to react with stearyl chloride,the yield and degree of substitution of cellulose stearyl ester（CSE）under different reaction conditions were investigated.CSE with a degree of substitution of 2.67 can be dissolved in a variety of organic solvents,when dissolved in THF and spun on the surface of hydrophilic filter paper by electrospinning to obtain superhydrophobic filter paper substrate,which can self-clean hydrophilic starch.The dissolve performance of DS=1.18 CSE was poor,but can adsorption 21～23 g/g of methylene chloride.CSE was emulsified by starch solution and evenly dispersed in water,the filtration paper base paper was impregnated in solution,after drying,hydrophobic membrane was obtained,water contact angle 135°.Being used starch as dry strength agent,stiffness was increased 1.9 times and mullen burst increased 2.6 times.The membrane can selectively adsorb dichloromethane from the bottom of water and showed anti-fouling properties.The effect of the filter membrane on the mixture of dichloromethane and water was tested.After 10 cycles of testing,the oil-water separation performance remained more than 99%.The separation performance of emulsified oil-water mixture was tested using ISO 16332 standard,and the average oil-water separation efficiency was 99%.We mixed the commercial hardwood and PFI treated softwood together,by using the traditional papermaking process,the 100 g/m² base paper was obtained.Then polydimethylsiloxane（PDMS）was used for low surface energy chemicals,thermosetting phenolic resin worked as adhesive,after curing,high strength of hydrophobic-oleophilic filter paper was obtained.PDMS can be hydrolyzed to produce silyl alcohol bonds,which can react with cellulose hydroxyl groups and self-polymerize to form nanoparticles,further providing rough surface.By using 1%of PDMS,the WCA was roughly 134.8°,and the resulted oil water separation efficiency was all higher than 99%.It was found that the oil and water separation rate could be improved with the increase of the addition amount of PDMS and the PFI treated softwood pulp.The cured phenolic resin provided the filter paper with high strength and could support 500 m L water and the weight of a beaker after folding,which was a very promising oil-water separation filter paper.In order to explore an oil-water separation material that can achieve low surface energy propertity without chemicals addition.Firstly,the filter paper base paper was prepared by mixing unbleached kraft pulp and microglass fiber in papermaking process,and then the base paper was carbonized under the protection of N₂ at 800°C to obtain hydrophobic oil-water separation carbon paper with water contact angle of 140°.Microfiberglass was added to reduce shrinkage during carbonization,reduce pore size and improve porosity.Carbon paper with 70%microfiber content had an average pore size of4.51μm and porosity of 90.22%.In oil-water mixture,carbon paper floated at the junction of oil-water and can not be polluted by water under oil.Carbon paper can effectively separate a variety of incompatible oil slick mixtures,with a separation efficiency of more than 99%after five cycles.Mixed kerosene and water（volume ratio of 99:1）together,after being high speed shearing to form water-in-oil emulsion,emulsion particle size was about959 nm,after filtration membrane separation,there was no droplet particles observed under optical microscope,it can include that low pore size of carbon paper also can separate emulsion type oil-water mixture.