| With the increasingly severe environmental pollution and the shortage of fresh water resources,water pollution is becoming extremely prominent.Among which,the problem of oil pollution water is more stark.The oil-water separation technology with the traits of low costs,high efficiency and universality is thus required urgently.Meanwhile,Membrane filtration technology has the advantage of low costs,little secondary pollution,easy to operate and simple device,it is obviously an eco-friendly oil-bearing water purification technology.The key part,however,lies in the development of membrane materials with high oil removal rate,high flux and superior corrosion resistance.In order to overcome the defects of oil-water separation membrane,chitosan modified solution,chitosan/titanium dioxide modified solution and polyvinyl alcohol/chitosan/titanium dioxide modified solution were respectively coated on the surface of hydrophobic pure nitrocellulose membrane via negative pressure suction filtration to prepare a series of fibrin composite membranes.With the help of SEM,XPS and contact angle instrument,the properties of cellulose composite membrane with different compounding ratio and composition were prepared,and the micro structure,element distribution and composition of cellulose composite membrane were systematically compared.By experimentally research,the best mass ratio of CS:TiO2 was 2:4,PVA:CS:TiO2 was 4:4:8.Besides,the corrosion resistance and stability of NCTM(2:4)and PT(4:8)cellulose composite membranes as well as the effect of TiO2 photocatalysis in NCTM(2:4)on the membrane flux were studied.The main conclusions were as follows:(1)Results of SEM and XPS analysis indicated that titanium dioxide,chitosan and polyvinyl alcohol could be successfully coated on the surface of pure cellulose nitrate film.(2)Through the comparison between pure nitrocellulose membrane and CS:TiO2 cellulose composite membrane with different mass ratios,it was showed that the NCTM(2:4)membrane with CS:TiO2 mass ratio of 2:4 had the best performance in terms of the indicators of wettability of membrane,filtration flux,oil removal rate and cycle times.The contact angle of water of the membrane in air and underwater oil were 0 degree and 153±2.5 degrees respectively,and it’s flux,oil removal rate and the number of cycles in o/w separation of diesel oil emulsion were 4802.5 L/(m2·h),99.0%and 10 times respectively.The filtration flux of NCTM(2:4)membrane to oil-water mixture with strong acidity and high salinity did not decrease appreciably,and the oil removal rate remained at a high level of 98.2%.The photocatalysis experiment of NCTM(2:4)membrane polluted by oil was carried out under UV.Results showed that titanium dioxide in the membrane had photocatalytic oil removal effect on the membrane surface to some extent.Its flux increased with photoperiod at first,after 15 hours of illumination,however,it changed little.The maximum recovery filtration flux of the polluted membrane was 1828.2 L/(m2·h),and the oil removal rate of the membrane was kept averagely above 98%.(3)The PT(4:8)cellulose composite membrane prepared by this research had a WCA of 0 degree and an OCA of 159.3±5 degrees.The flux and oil removal rate of filtered diesel oil were 5867.3 L/(m2·h)and 99.4%respectively,and recycled times was up to 18.The comprehensive analysis showed that the PT(4:8)cellulose composite membrane of PVA:CS:TiO2 with the mass ratio of 4:4:8 had the best performance.(4)When PT(4:8)membrane was used in oil-water separation experiment under the strong acid-base and high salinity circumstances,the filtration flux did not decline obviously,and the oil removal rate could be kept over 98.9%,which proved its strong stability and corrosion resistance.Compared with NCTM(2:4)membrane,the toughness and water resistance of CS and PVA mixture were significantly improved after polyvinyl alcohol was introduced into the solution so that the stability and mechanical properties of the membrane in the solution were enhanced as well. |
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