(748f) Polyamide/CNT Thin Film Nanocomposite (TFN) RO Membranes with Improved Boron Rejection

Thin film nanocomposite (TFC) RO membranes have remarkably improved in terms of salt removal; however, removal of boron from seawater is an emerging problem. According to World Health Organization (WHO), boron concentration should not exceed 2.4 ppm for potable water and 0.5 ppm for irrigation water used for crops such as citrus fruits and nuts. Since boron is present in seawater as boric acid and its effective diameter is close to hydrogen-bonded cluster of water molecules, conventional TFC membranes fail to achieve effective boron removal. Incorporating nanomaterials into TFC membranes has potential for improving selectivity as well as water flux and anti-fouling properties. However, this requires optimizing the conditions for loading, size, type, and functional groups of the nanomaterials as well as the interfacial polymerization and post-treatment protocols. In this study, we investigate the influence of embedding carbon nanotubes functionalized with different functional groups into polyamide RO membranes on their boron rejection performance. Deposition and alignment of SWCNTs on a commercial polysulfone UF membrane was carried out by vacuum filtration. The polyamide layer was prepared by interfacial polymerization using m-phenylene diamine (MPD) and tri-mesoyl chloride (TMC) as monomers. Membranes were characterized by SEM, FTIR, XPS, polarized Raman spectroscopy, and crossflow filtration tests. Results showed that concentration of CNT significantly affects dispersion and alignment of CNTs inside the polymeric matrix as well as homogeneity, thickness and crosslinking ratio of polyamide layer. The salt and boron rejection performance of the TFN membranes depends on the functional group and CNT loading; some membranes exhibited increased performance relative to neat polyamide membranes.

(This work is supported by the Scientific and Technological Research Council of Turkey (TUBITAK) through Project No. 114Y165.)