Sepideh Masoumi Khosroshahi - Membrane Technology Research Center, Sahand University of Technology, Tabriz, Iran.
Alireza Miroliaei - Department of Chemical Engineering, University of Mohaghegh Ardabili, Ardabil, Iran.
Younes Jafarzadeh - Faculty of Chemical Engineering, Sahand University of Technology, Tabriz, Iran.

Polyvinyl chloride (PVC) membranes containing pristine and modified multiwall carbon nanotube (MWCNT) were prepared and characterized. MWCNT was modified in order to achieve well-dispersion within the membranes. The results of FTIR analysis revealed that MWCNT was successfully carboxylated. The FESEM images indicated that the number of pores on the surface of membranes increased at the presence of pristine and modified MWCNT and the pore size distribution curves shifted towards smaller pores. The hydrophilicity, pure water flux, tensile strength and abrasion resistance of the membranes increased with increasing the content of MWCNT and COOH-MWCNT up to 0.3 wt. % and then decreased due to the agglomeration of nanotubes. Nevertheless, at the same content of nanotubes, COOH-MWCNT had more effect than MWCNT. The performance of the membranes was studied by filtration of humic acid (HA) solution and the results showed that HA rejection reached a peak of 96.88% for 0.3 wt. % PVC/MWCNT-COOH nanocomposite membrane. Finally, it was found that the antifouling properties of the membranes increased with increasing nanotube content, especially COOH-MWCNT. 

PVC, MWCNT, Membrane, Ultrafiltration, Humic acid