| Three novel negative charged composite nanofiltration membranes were prepared, which were Chitin-ECH, Chitin/CMC-ECH and Chitin/CMC-PTGE composite membrane, respectively. The active layer material was Chitin and CMC, crosslinking agents were epichlorohydrin(ECH) and PTGE, supporting layer was polyacrylonitrile(PAN) UF membrane. Effects of membrane making and operating conditions on performance of the composite membrane and structure of the membrane were studied. Using the Chitin/CMC-ECH composite membrane, the application experiments were studied in the treatment of reclaimed water. The whole paper contained the four parts below.1. Study of Chitin /polyacrylonitrile (PAN) composite nanofiltration membrane cross-linked by epichlorohydrin(ECH)A novel composite nanofiltration membrane was fabricated by coating alkali solution of chitin onto polyacrylonitrile(PAN) UF membrane and subsequently cross-linked by epichlorohydrin(ECH). Effects of membrane making and operating conditions on performance of the composite membrane and structure of the membrane were studied. The composite nanofiltration membrane with excellent rejection performance should be prepared while sodium chitin solution concentration was 2.0 wt %, epichlorohydrin(ECH) concentration was 0.6 wt %, cross-linking time was 18h at 50℃. The membrane had a negative electric charge, which came from PAN's hydrolyzation. The resting membrane potential was -0.05mv and the etectro-osmotic transmission coefficient (β) was -3.23mv/Mpa; molecular weight cut-off was about 670g·mol-1, the pore radii of the membrane was about 0.8nm. The salt rejections to K2SO4, Na2SO4, MgSO4, KCl, NaCl, MgCl2 and CaCl2 (1000mg·L-1) were 88.6%, 88.7%, 37.6%, 30.2%, 29.7%, 10.8% and 12.7%, and the fluxes were 17.6, 17.1, 17.9, 19.3, 18.6, 19.2 and 19.5L·m-2·h-1, respectively. The rejection capability to electrolyte was determined by physical structure of the composite membrane and static force between the membrane and the ion of the electrolyte.2. Preparation and characterization of composite nanofiltration membrane based on Chitin and CMC blend solution cross-linked by epichlorohydrin(ECH)A novel composite nanofiltration membrane was fabricated by coating alkali solution of chitin and CMC onto polyacrylonitrile(PAN) UF membrane and subsequently cross-linked by ECH. Effects of membrane making and operating conditions on performance of the composite membrane and structure of the membrane were studied. The composite nanofiltration membrane with excellent rejection performance should be prepared while the proportion of chitin/CMC was 2:1(w/w), concentration of ECH was 0.6wt% and the cross-linking time was 18h at 50℃. The membrane had negative electric charges, which came from PAN's hydrolyzation. The resting membrane potential was -0.12mv and the etectro-osmotic transmission coefficient (β) was -16.1mv/MPa; molecular weight cut-off was about 640g·mol-1, the pore radii of the membrane was about 0.7nm. The salt rejections to Na2SO4, K2SO4, MgSO4, KCl, NaCl, MgCl2, CaCl2 (1000mg·L-1) were 90.7%, 87.8%, 23.7%, 30.4%, 29.5%, 17.1% and 15.9%,and the fluxes were 15.1, 15.6, 12.2, 15.3, 14.6, 13.2 and 13.5L·m-2·h-1, respectively. The rejection capability to electrolyte was determined by physical structure of the composite membrane and static force between the membrane and the ion of the electrolyte.3. Preparation and characterization of composite nanofiltration membrane based on Chitin and CMC blend solution cross-linked by PTGEA novel composite nanofiltration membrane was fabricated by coating alkali solution of chitin and CMC onto polyacrylonitrile(PAN) UF membrane and subsequently cross-linked by PTGE. Effects of membrane making and operating conditions on performance of the composite membrane and structure of the membrane were studied. The composite nanofiltration membrane with excellent rejection performance should be prepared while the proportion of chitin/CMC was 2:1(w/w), concentration of PTGE was 0.6wt% and the cross-linking time was 20h at 50℃. The membrane had negative electric charges, which came from PAN's hydrolyzation.The resting membrane potential was -0.12mv and the etectro-osmotic transmission coefficient (β) was -13.07mv/MPa; Molecular weight cut-off was about 610g·mol-1, the pore radii of the membrane was about 0.7nm. The salt rejections to Na2SO4, K2SO4, MgSO4, KCl, NaCl, MgCl2, CaCl2 (1000mg·L-1) were 93.6%, 89.8%, 24.4%, 33.3%, 29.6%, 10.1% and 6.7%, and the fluxes were 12.5, 13.1, 9.8, 12.5, 12.2, 10.7 and 11.0L·m-2·h-1, respectively. The rejection capability to electrolyte was determined by physical structure of the composite membrane and static force between the membrane and the ion of the electrolyte.4. Study on the application of Chitin/CMC-ECH composite nanofiltration membrane in the treatment of reclaimed waterThe prepared Chitin/CMC-ECH composite membrane were used to dispose the reclaimed water, including the removal of the total soluble phosphorus,aniline and CODCr. The results indicated that the removal rates of the total soluble phosphorus, aniline and CODCr were above 70%, 25% and 85% respectively. CODCr in the permeation flux feed was below 15mg·L-1, which had reached I water quality discharge standards, according to surface water environmental quality standard of GB3838-88.The prepared composite membrane with negative charges had obtained good results in the removal of the total soluble phosphorus and CODCr, the new type membrane will have a prospective application in the treatment of industrial waste water, purification of drinking water, et al. |
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