Novel charged chitosan composite nanofiltration membranes containing chiral mesogenic group

To improve the performance of nanofiltration (NF) membranes, a chiral mesogenic compound, a positively charged compound, and a negatively charged compound were grafted to chitosan, respectively. Series of novel composite NF membranes were prepared by over-coating the polysulfone ultrafiltration membrane with the mixture of chitosan and modified chitosan. The chiral mesogenic compound, the positively charged compound, the negatively compound and their chitosan derivatives were characterized by infrared spectrophotometer, differential scanning calorimetry, polarized optical microscope; the structure of the membrane was characterized by scanning electron microscopy. The performance of composite NF membranes was strictly related to the novel compounds grafted to chitosan and its composition. The rejection reached the maximum of 95.7% for Ca[Cl.sub.2] with [P.sub.2-7] composite NF membrane, corresponding flux was 3155 [Lm.sup.-2][h.sup.-1]. The rejection reached the maximum of 93% for [Na.sub.2]S[O.sub.4] with [P.sub.3.5] composite NF membrane, corresponding flux was 3879 [Lm.sup.-2][h.sup.-1]. Comparing with conventional NF membranes, the membranes were used in low pressure with high flux, especially for the separation of high-valence ions from solution. The membranes were typical charged NF membranes.
INTRODUCTION Nanofiltration (NF) technology has been used in diverse fields including concentration, purification, and fractionation of various products, etc [1, 2]. Due to its high separation efficiency and low energy [...]