Pervaporation of benzene/cyclohexane mixtures through mixed matrix membranes of chitosan and Ag+/carbon nanotubes

Abstract

Functionalized multiwalled carbon nanotubes (MWNTs) were incorporated into a chitosan membrane for separation of benzene/cyclohexane mixtures by pervaporation. The pristine MWNTs were treated by mixed acid (H2SO4/HNO3=3/1) and then functionalized with isonicotinic acid. Ag+ was grafted to the pyridine ring on the MWNTs by a complexation reaction. Membranes made of chitosan and Ag+/carbon nanotubes were prepared with polysulfone membranes as support. The surface structure of modified MWNTs was examined by FT-IR, TEM, EDS and XPS to assess its morphology. The swelling and pervaporation characteristics of the membranes for separation of benzene/cyclohexane mixtures were investigated. The swelling degree of the membranes in benzene was more than 2.5 times that of the pristine chitosan membrane. The swelling degree was found to increase with the content of the MWNTs–Ag+ in the membrane and the benzene content in the feed. Pervaporation results also showed that the MWNTs–Ag+/chitosan hybrid membrane separation performance is better than MWNTs/chitosan hybrid membrane and pristine chitosan membrane. The permeation flux of the membrane increased, the selectivity increased firstly and then decreased with the increase in the content of MWNTs–Ag+. The selectivity reached 7.89 and the permeate flux was 357.96g/m2h (the mass ratio of benzene was 50%, the temperature was 20°C) when the percentage by weight of the MWNTs–Ag+ to chitosan was 1.5%. The Arrhenius activation parameter of 1.5% MWNTs–Ag+/chitosan (CS) hybrid membrane is 4.28kJ/mol while 1.5% MWNTs/CS membrane is 10.6kJ/mol in 50% benzene concentration in feed.