Hydrophilic Regulation And Properties Of Cellulose Or Polystyrene Mesh For Oil-water Separation

Environmental pollution and energy shortage are two bottleneck problems plaguing the development of today’s society.Oil is both an energy source（feedstock）and a common water pollutant.Using low energy consumption oil-water separation technology is an effective resolution to recover oil resources while treating water oil pollution.Membrane separation technology is a kind of low energy consumption and green separation technology,which has great potential in oil production,recovery and oil pollution control.In this paper,the super‐hydrophilic membrane suitable for oil removal from water is studied.The details are as follows:1.The relevant theoretical equations of wettability,flux and separation efficiency of oil-water separation membranes were derived and establishedThe equations of cosθ-λand wettability membrane flux were established to describe the relationship between surface wettability and chemical modification,and between membrane flux and surface wettability,respectively.The related theories and equations affecting the separation efficiency of oil-water separation membrane are summarized.The constraints for complete separation are given using Taylor G.I.equation.2.Preparation and evaluation of a kind of wettability‐controlled surface and two kinds of new membranes prepared by modification of cellulose and polystyrene substratesA hydrophilic coating with controllable wettability was prepared on the glass surface by layer layer-by-layer method.The contact angle of the coating surface could be precisely controlled by controlling the concentration of sodium perfluorooctanoate in the range of 23.5^o～82.0^o（R²=0.9978）.The water contact angle of this surface was positively correlated with the degree of chemical modification,which conforms to the expectation of cosθ-λequation.Two kinds of cellulose membranes of cotton mesh and MCE membrane were modified by chlorine sulfonic acid.The modified cotton membrane had a large water flux of 4.3×10⁵ L·m^-2·h^-1,and the MCE membrane also had a large water flux of 4.3×10³ L·m^-2·h^-1（10 k Pa）,which increased by 14.49%and 25.00%,respectively,compared with the origin membrane.By controlling the surface modification ratio,the membrane flux was precisely regulated（R²=0.9161 and 1）,which conforms to the expectation of the membrane flux equation.In addition,the modified cotton mesh was more resistant to swelling caused by Na₂SO₄ solution.Compared with about 20%flux loss in CH₃COONa solution,the flux loss in Na₂SO₄ solution was less than 10%.Using concentrated sulfuric acid to sulfonate hydrophobic polystyrene into hydrophilic polystyrene,and then using non‐solvent induced phase separation method to modify it onto nylon mesh,to prepare special salt‐philic PS-SO₃H/nylon membrane.The membrane had a large water flux(up to 2.5×10⁴ L·m^-2·h^-1)and can be further lifted by salt solution.In the study,the flux was increased to a maximum of 260%and finally stabilized at about 170%.This special ion response phenomenon can be explained by the derived Young-Lippmann-Gibbs equation.3.Study on oil-water separation performance of two kinds of new membranes prepared by modification of cellulose and polystyrene substratesThe separation efficiency of both cotton mesh and PS-SO₃H/nylon membrane was close to 100%,and still did not decrease after 100 times of oil-water separation.The flux performance of cotton mesh decreased only by 2%～6%after 100 times of oil-water separation.For PS-SO₃H/nylon membrane,the flux decreases related to the direct contact time between oil and membrane,which has excellent reuse performance in the continuous separation process.The MCE membrane with smaller pore size was used to emulsified oils separation,and the TOC contents after separation were less than 60 mg·L^-1.It was close to the amount of added surfactant and can be considered complete separation.The oil-water separation performance and oil‐pollution resistance of hydrophilic membrane depend on the stability of its surface water layer.The controlled destruction of water layer on PS-SO₃H/nylon membrane by methyl tert‐butyl ether can make it lose its oil-water separation performance.