Effects of the carbon nanotube and polymer amounts on ultrafiltration membranes

Composite membranes with nano-sized inorganic materials have high selectivity, high hydrophilicity, and improved fouling resistance. Blending Carbon Nanotubes (CNTs) in the polymer solution improves membrane properties like hydrophilicity, water permeability, selectivity, and fouling resistance. The effect of the polymer amount, together with the CNT amount in the polymer solution on membrane properties, was investigated in this work. There was more than 10% increase in the hydrophilicity of the membranes with 1% CNT addition, but it was not altered with the polymer amount. The porosity was increased almost 30% by 1% CNT addition in membranes prepared by 10% and 12% polymer concentration (P-10:C-0 and P-12:C-0), but only 16% increase in porosity occurred in membrane prepared by 15% polymer concentration (P-15:C-0). The flux of the P-15:C-0 membrane was increased four times by 1% CNT addition. Besides, fouling resistance of the membranes decreased with increasing polymer amount but increased with increasing CNT amount. BSA rejection increased with increasing polymer amount or CNT amount in the polymer solution. Hence membranes prepared with a higher amount of polymer are more prone to membrane property improvements with CNT addition. The increase in flux and selectivity by CNT addition in all membranes prepared with different polymer concentrations will increase the membrane life-time and reduce the treatment cost.