Improvement in Polyamide Thin Film Nanofiltration Membrane Performance with Modified Titanium Oxide Nanotubes

Hypothesis:

 Nowadays, nanofiltration membranes are used extensively in desalination and water treatment, but some major drawbacks in the desalination such as low flux and rejection should be handled through application of modified nanomaterials. A number of research works have been done in this field but the importance of the subject makes more studies in this field indispensable.

Thin film nanocomposite membranes containing titanium oxide nanotubes and modified titanium oxide nanotubes were evaluated in this study which after synthesis of the nanotubes, their inner surface was modified and after synthesizing the membranes, the membranes’ water permeability and rejection of the monovalent and divalent ions were measured. Furthermore, Fourier transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) tests were used to study the neat and modified nanotubes. Field emission scanning electron microscopy (FE-SEM) analysis was used to study the morphology and structure of these thin film membranes.

The performance of polyamide thin film membranes was evaluated by pure water permeation test, contact angle test, permeation flux of the feed and rejection of sodium and copper ions. Due to the hydrophilicity of the nanotubes and formation of small pore on the membrane surface, the maximum pure water flux (26.5 L/m2h) was obtained for the membrane containing 0.05% (wt) unmodified nanotube; an increase of 73.2% compared to its neat membrane. Due to the reduced diameter of the modified nanotubes and providing sufficient energy barrier for the salts to be rejected, the maximum sodium ion rejection (93.11%) was obtained for the membrane containing 0.2% (wt) modified nanotubes.