Preparation Of Superhydrophilic And Superoleophobic Coated Mesh Film And Its Performance Of Oil-water Separation

Massive emissions of sewage and industrial waste water, the occurrence of oil spills at sea frequently, which presented a huge challenge for our sewage treatment capacity. Oily waste water would cause great harm to the environment, such as oil floating in the sea, the rapid spread of the oil formation a layer of gas-impermeable film would hinder the water body reoxygenation role in influencing the growth of marine plankton, disrupting the marine ecological balance. Wastewater treatment and it is also extremely difficult, low efficiency and high cost. Membrane separation with low energy consumption, high efficiency single-stage separation, the process is simple and flexible, low environmental pollution, versatility, etc., but the use of membrane separation efficiency limited by internal factors stain resistance, thermal stability, chemical stability of the film, etc., and membrane form, operating conditions extrinsic factors. Oily wastewater treated by superhydrophilic and superoleophobic membrane separation processing method, the so-called Water-Removing method, the film is superoleophobic in air or under water, and the oil exhibits very low adhesion, the rolling contact angle of only 2~3°, effectively prevented the adhesion of droplets. When the oily wastewater contacted the surface of the film, water can penetrate down as a steady stream, but the surface always maintain the superoleophobic performance, the oil trapped in the surface so as to achieve the effect of oil and water separation, and because of the potential repellency oil performance of film, the oil always could not pollute the membrane surface, It is a real anti-pollution, low energy consumption, long life, high efficiency membrane, thus become the main direction of development of oil-water separation membrane. In this paper in this context, were committed to research and development of superhydrophilic and superoleophobic oily water separation membrane, the focus around the surface wettability film theory and application of chemical stability and separation efficiency of the film unfolds, concrete as follows:(1) Application of capillary dynamics in the separation process of superhydrophilic coated mesh and construction of its mechanical model. The current study was mostly aimed at the synthesis methods and separation efficiency of membranes materials, nevertheless, the related dynamic process of membrane separation process and quantitative calculations were rarely involved. In this paper, the related physical quantities of superhydrophilic membrane separation process were investigated based on the idea of capillary mechanics. The membrane pores of membrane material based on the special wettability was classified as capillary pores, meanwhile, a mathematical model was been built on this basis in orde to analyze the force distribution condition of superoleophilic membrane separating oil-water mixture in detail. The principle of the superhydrophilic and superoleophilic membrane in the air transforming superoleophobic underwater was calculated and analyzed from the perspective of the surface tension. The capillary flow rate, capillary permeability rate, membrane flux and critical penetration pressure of membrane separation process were calculated in detail from the perspective of capillary dynamics and validated from practical experiments. On this basis, the separation mechanism of superhydrophilic and underwater superoleophobic oil/water separation membrane was primarily discussed from the view of capillary mechanics.(2) Preparation of superhydrophilic and underwater superoleophobic coated mesh and test of its oily water separation performance. Stainless steel mesh with good mechanical properties was used as a substrate, polyvinyl alcohol and hydroxyl acrylic resin rich in hydroxyl groups, with excellent film forming, hydrophilic and water retention properties were used as the basic film material, glutaraldehyde was used as crosslinking agent, doped Si O2 hydrophilic inorganic nano-particles, micro and nano roughness were constructed, finding that would help to improve the surface roughness of the film using multiple sequential coating methods, so that the superhydrophilic properties of the surface of the membrane would stable in the natural environment, by a simple two-step dip coating method and heat curing method, a membrane with superhydrophilic and superoleophobic properties under water environment was successfully prepared. The various types of film can be effectively separated mixture of oil and water, such as vegetable oils, gasoline, diesel and crude oil-water mixtures, the separation efficiency were up to 99%, after the oil content of the sewage treatment allows less than 50mg/l. During separation process, the underwater superoleophobic and oil low adhesion characteristics of the membrane make the membrane surface hard to be adhesion and difficult to be pollution by oil, so that the recovery of oil and material recycling become easy.(3) Preparation of UV curable superhydrophilic and underwater superoleophobic coated mesh and test of its oily water separation performance. First, the stainless steel mesh were pre-treated by the UV-curable PUA/EA composite emulsion, which was good corrosion resistance and environmentally friendly, thus corrosion protection layer build on the stainless steel wire mesh surface. then the polyethylene glycol acrylate UV curable oligomers with environmentally friendly, rich in hydroxyl hydrophilic excellent performance were used as the basis for the film-forming material, and PVA was used as emulsifier, doped hydrophilic inorganic nano-Si O2 particles, using UV curing method to construct the micro and nano roughness structure; and finally the higher molecular weight hydrophilic monofunctional polyethylene glycol diacrylate UV curable oligomer were grafted to the surface of the film, so that the surface of the film has a molecular structure brush, a oil-water separation membrane which could suitable for complex chemical environment, and own self-cleaning function and superhydrophilic/superoleophobic properties under water environment was obtained. The film can be effectively separated various types of mixture of oil and water, so that the oil content of the treated effluent is less than 50mg/l. During separation process, the anti-corrosion coating film can effectively resist the waste acid corrosion of the substrate, a membrane surface with hydrophilic molecular brush structure, the adhesion of the oil to the surface of the film was very low, the underwater superoleophobic and oil low adhesion characteristics of the membrane make the membrane surface hard to be adhesion and difficult to be pollution by oil, so that the recovery of oil and material recycling become easy.(4) Preparation of the hygro-responsive superhydrophilic and superoleophobic coated mesh and test of its oily water separation separation performance. First, the stainless steel mesh were pre-treated by the UV-curable PUA/EA composite emulsion, which was good corrosion resistance and environmentally friendly, thus corrosion protection layer build on the stainless steel wire mesh surface. Secondly, the synthetic hydrophilic and oleophobic polymer doped with the chapter hydrophilic UV curable coatings were used as a base film material, PVA was used as emulsifier, doped hydrophilic inorganic nano-Si O2 particles and oleophobic modified inorganic nano-Si O2 particles constructed micro and nano roughness on the surface of the membrane, a hygro-responsive superhydrophilic and superoleophobic membrane were prepared by a simple dip coating method and UV and heat-cure method successfully. After a period of time the film is placed under the water environment, stimulating interaction in water, hydrophilic groups will self-assembled to the surface membrane, the oleophobic groups on the ground floor, which has a stable hydrophilic surface, but the bottom layer of the film was hydrophobic and oleophobic, under the action of the liquid column pressure, water can penetrate the lower hydrophobic layer and seeps, and oil need to cross the double protection of the upper hydrophilic layerand the lower hydrophobic and oleophobic layer to penetrate, therefore, when the filtration pressure was properly adjusted, allows only water to penetrate, and the oil could not penetrate, to achieve the separation of oil and water. And because of this type of film has a hydrophilic layer and a hydrophobic and oleophobic layer double-layer anti-oil pollution, so as to had better stain resistance.