Investigation of raw and oxidized multiwalled carbon nanotubes in fabrication of reverse osmosis polyamide membranes for improvement in desalination and antifouling properties

Multiwalled carbon nanotubes (MWCNTs) embedded polyamide reverse osmosis membranes were synthesized by incorporating two kinds of raw and oxidized MWCNTs with different concentrations in diamine aqueous solution of interfacial polymerization method. The oxidized MWCNTs were functionalized with hydrophilic groups in order to increase membrane performances. Surface contact angle, SEM images, FTIR, salt rejection, water flux and BSA/salt fouling tests of the nanocomposite membranes were investigated to reach an acceptable performance. Results exhibited that the amount of water flux and hydrophilicity were improved by increasing the concentration of the MWCNTs up to 0.005 wt%. In high concentrations of both MWCNTs, the flux was decreased. For raw MWCNTs, despite less hydrophilicity, the experiments showed a considerable growth in water flux and salt rejections due to well disperse with polyamide membrane materials. The saline solution fluxes were reached from 20.3 to 25.9 in the raw and 28.9 L/m² h in the oxidized MWCNTs embedded membranes. The evaluations of fouling behavior in 24 h test with BSA/salt solution were shown that the membranes with all concentrations of raw or oxidized MWCNTs had better antifouling performance rather than the unfilled membrane.