Preparation of chitin xanthate/polyacrylonitrile NF composite membrane with cross-linking agent hydrogen peroxide and its characterization

摘要

A composite nanofiltration (NF) membrane was prepared by coating aqueous solution of chitin xanthate onto polyacrylonitrile UF membrane and subsequently cross-linked with H_2O_2 in ethanol. The effects of the membrane preparation conditions and operating conditions on performance of the composite membranes were studied. The results suggested that composite NF membrane with excellent rejection performance should be prepared with 1.0wt.% of chitin xanthate concentration, 0.9 wt.% H_2O_2 concentration, 3.0 h cross-linking at 30℃, and then 15 min heat treatment at 50 ℃. The pressure osmotic coefficient of membrane was —4.2 mV MPa~(-1). Characterization results suggested: molecular weight cut-off of the resulting membrane was 652 Da; the rejections of the resulting membrane to Na_3PO_4, K_2SO_4, Na_2SO_4, MgSO_4, KC1, NaCl and MgCl_2 solutions (1000mgL~(-1)) were 91.85%, 90.65%, 85.65%, 53.39%, 40.29%, 40.53% and 28.44%, respectively, and the permeations were 11.73Lh~(-2) m~(-2), 13.75 Lh~(-1) m~(-2), 13.91 Lh~(-1) m~(-2), 14.27 Lh~(-1) m~(-2), 14.18 Lh~(-1) m~(-2), 14.81 Lh~(-1) m~(-2) and 15.05 Lh~(-1) m~(-2), respectively, at the operating pressure of 0.40 MPa and cycling flow of 40 L h~(-1). Similar to other negative charged membranes, the rejection performance of the composite membrane depended on the electrostatic strength between the charged membrane and ions of electrolyte. With its high rejection to PO_4~(3-) and SO_4~(2-) ion, the membrane can be applied to the removal of PO_4~(3-) and SO_4~(2-) ion and the purification of water.