High Flux Polyamide Composite Hollow Fiber Membranes for Reverse Osmosis Applications
- PDF / 75,946 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 39 Downloads / 183 Views
0930-JJ01-07
High Flux Polyamide Composite Hollow Fiber Membranes for Reverse Osmosis Applications Ian D. Norris, Malcolm C. Morrison, and Benjamin R. Mattes Santa Fe Science and Technology, 3216 Richards Lane, Santa Fe, NM, 87507
ABSTRACT Membrane elements consisting of hollow fiber for reverse osmosis (RO) applications can typically achieve a 4 to 20X higher membrane packing density than spiral wound membrane elements. Despite this significant improvement in packing density, RO elements are predominately being manufactured in a spiral wound configuration. This is due to the order of magnitude lower water flux values of asymmetric hollow fiber RO membranes when compared with that of composite flat-sheet membranes with a polyamide salt rejecting layer (30-80 vs. 900-1100 L/m2·day at a feed pressure of 225 psi). The fabrication of composite hollow fibers is a feasible approach to increase the water flux of hollow fiber membranes for brackish water desalination. In this work, composite hollow fibers with a polyamide salt rejecting layer have been successfully prepared. The polyamide selective layer was deposited on the outer surface of a polysulfone hollow fiber support based on the interfacial polymerization reaction between mphenylenediamine and trimesoyl chloride/isophthaloyl dichloride. The RO performance of these membranes was evaluated using a 2,000 ppm NaCl feed solution at 225 psi. After an initial break-in period, the stabilized RO figures-of-merit for these hollow fiber membranes were a water flux of 280 L/m2·day and a NaCl rejection of 99.1%. With an approximately five-fold increase in membrane packing density, the production of potable water of these composite hollow fiber elements will exceed that of commercially available spiral elements by 20-30%. INTRODUCTION Reverse osmosis (RO) is a widely commercialized separation process. RO membranes consist of a dense surface layer (50-500 nm) that is highly permeable to water, but highly impermeable to dissolved salts, organic molecules, microorganisms, and colloids. There are essentially two element configurations for RO applications: hollow fiber and spiral wound elements. A detailed discussion of the design, operation and advantages of these different membrane element configurations for RO applications can be found elsewhere [1], but the most noticeable difference is that hollow fiber membranes elements typically possess a 4 to 20X higher membrane packing density than spiral wound membrane elements (4,000-20,000 m2/m3 vs. 900-1,000 m2/m3). Hollow fiber membranes for brackish water desalination have traditionally been fabricated using a phase inversion process which results in a thinly skinned (< 500 nm) salt rejecting layer at the outer surface, with the underlying mass being of graded porosity. Using this approach, polyamide hollow fiber membranes have been commercialized by DuPont (Permasep®) and Toyobo (Hollosep®) over the last decade. However, the RO performance of these hollow fibers has been superseded by composite flat-sheet membranes. The current ge
Data Loading...
