(714e) Thin Film Nanocomposite (TFN) Membranes Containing Functionalized Zeolite Nanoparticles for Desalination with High Boron Rejection

Inadequacy of natural water resources has become a worldwide concern and production of potable water from brackish or seawater via reverse osmosis (RO) stands out as the leading technology. Mixed matrix membrane (MMM) concept, which combines desirable properties of a filler and a polymer, have been utilized extensively for gas separation applications and more recently extended to water separation applications. Several studies on nanoparticle (zeolites, carbon nanotubes, graphene, metal organic frameworks, metal oxides, etc.) incorporation into the thin film polyamide structure during interfacial polymerization process reported improved RO membrane performance, i.e. improved salt rejection, water flux and anti-fouling properties. These mixed matrix RO (also called TFN) membranes offer considerable promise for achieving desalination while concurrently reducing the boron concentration to the level recommended by the World Health Organization (< 2.4 ppm for potable water and < 0.5 ppm for irrigation water). In this work, we explore the possibility of tailoring the desalination performance to add new functionality of high boron rejection to RO membranes by incorporating functionalized zeolite 4A nanoparticles into the polyamide layer. The 3-D structure of zeolite A offer the advantages of easy embedding in membrane structure and lack of the need for orientation over 1-D and 2-D structures such as carbon nanotubes and graphene. In-house synthesized zeolite 4A nanoparticles were surface functionalized with hexadecyltrimethylammonium (HDTMA) to hinder the passage of boric acid molecules. Zeta potential measurements were used for characterization of functionalized zeolites. TFN polyamide layer was prepared on commercial ultrafiltration support membranes by interfacial polymerization using m-phenylene diamine (MPD) and tri-mesoyl chloride (TMC) as monomers and zeolites were incorporated in the TMC solution. TFN membranes were characterized by XPS, SEM, AFM, contact angle measurements and crossflow filtration tests for salt and boron removal. TFN membranes had improved boron rejection and higher pure water flux than TFC membranes without compromising salt rejection performance at neutral pH.

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