Study Of Chitin Xanthate/ Polyacrylonitrile Composite Nanofiltration Membrane

Chitin derivatives are excellent membrane materials with broad application prospects for their good abilities of moisture retention, filming performance, biocompatibility and being nontoxic. Some chitosan membranes, such as ultrafiltration membranes, reverse osmosis membranes and pervaporation membranes et al have been reported. But there's no report on chitin soluble derivatives nanofiltration membranes. In this thesis, two novel negative charged composite membranes are prepared for the first time, whose active layer material is chitin xanthate, cross-linking agents are glutaraldehyde(GA) and hydrogen peroxide, supporting layer is polyacrylonitrile UF membrane. And also the application of the membrane in the treatment of reclaimed water is studied. The whole paper contains three parts.1. Preparation of chitin xanthate/ polyacrylonitrile composite membrane with cross-linking agent glutaraldehyde and its characterizationA composite nanofiltration membrane is fabricated by coating solution of chitin xanthate aqueous onto polyacrylonitrile UF membrane and subsequently cross-linked by glutaraldehyde. Effects of membrane making conditions and operating conditions on performance of the composite membrane are studied. The results suggest that composite membrane with excellent rejection performance should be prepared while chitin xanthate concentration is 1.0%, glutaraldehyde concentration is 1.1%, cross-linking time is 3.0h at 30℃. Characterization suggests: The salt rejections to Na₃PO₄, K₂SO₄, Na₂SO₄, MgSO₄, KCl, NaCl and MgCl₂(1000mg·L^-1) are 90.25%, 89.01%, 85.15%, 36.42%, 32.60%, 28.90% and1 15.81%, respectively, and the permeation fluxes are 18.30L·h^-1·m^-2, 19.05L·h^-1·m^-2, 19.75L·h^-1·m^-2, 23.70L·h^-1·m^-2, 27.02L·h^-1·m^-2 , 28.69L·h^-1·m^-2 and 37.33L·h^-1·m^-2 respectively. Similar to other negative charged membranes, the rejection performance of the composite membrane is dependent on the electrostatic strength between the charged membrane and ions of electrolyte.2. Preparation of chitin xanthate/ polyacrylonitrile composite membrane with cross-linking agent hydrogen peroxide and its characterizationA composite nanofiltration membrane is fabricated by coating solution of chitin xanthate aqueous onto polyacrylonitrile UF membrane and subsequently cross-linked by hydrogen peroxide. Effects of membrane making conditions and operating conditions on performance of the composite membrane are studied. The results suggest that composite membrane with excellent rejection performance should be prepared while chitin xanthate concentration is 1.0%, hydrogen peroxide concentration is 0.9%, cross-linking time is 3.0h at 30℃. Characterization suggests: The salt rejections to Na₃PO₄, K₂SO₄, Na₂SO₄, MgSO₄, KCl, NaCl and MgCl₂(1000mg·L^-1) are 91.85%, 90.65%, 85.68%, 53.39%, 40.53%, 40.29%, and 28.44% respectively, and the permeation fluxes are 11.73L·h^-1·m^-2, 13.75L·h^-1·m^-2, 13.91L·h^-1·m^-2, 14.18L·h^-1·m^-2, 14.27L·h^-1·m^-2, 14.81L·h^-1·m^-2 and 15.05L·h^-1·m^-2, respectively. Similar to other negative charged membranes, the rejection performance of the composite membrance is dependent on the electrostatic strength between the charged membrane and ions of electrolyte.3. Study on the application of chitin xanthate/polyacrylonitrile composite membrane in the treatment of reclaimed waterChitin xanthate/polyacrylonitrile composite membrane are used to dispose the reclaimed water, including removal of total soluble phosphorus, total nitrogen in NO3- and NO2-, CODCr and chroma. The results indicate: when operating pressure is 0.40MPa, feed flow is 50L·h^-1, the removal rate of total soluble phosphorus, total soluble nitrogen in NO^3- and NO^2- and CODCr are above 85%, 87% and 71% respectively, and the chroma removal rate is nearly 100%. CODCr in the permeation feed has reached surface water I water quality standard of GB3838-88; total nitrogen in NO3- and NO2- in the permeation feed has reached surface water I water quality standard of GB3838-88; total soluble phosphorus in the permeation feed has approached the sewage comprehensive discharge standard GB8978-88 of 1mg·L^-1.The composite membrane prepared supply a new method for removal of nitrogen and phosphorus in the sewage, which is hopeful to apply in purification of drinking water , advanced treatment of reclaimed water et al.