Technology
NanOasis is pioneering the use of carbon nanotubes in reverse osmosis membranes to substantially lower energy use, size and capital requirements for desalination, and other water purification and fluid separations applications.
NanOasis membranes consist of a thin, dense polymer film having carbon nanotube (CNT) pores atop a highly porous support. Due to the interior surface characteristics of carbon nanotubes, water transport is significantly enhanced relative to other nanoporous materials. This discovery of enhanced transport was reported by Dr. Jason Holt, co-founder of NanOasis, in a 2006 Science cover article, following his work at Lawrence Livermore National Laboratory. The CNT pores are sufficiently small that they exclude salt ions, while permitting water transport. The combination of fine size discrimination and significantly enhanced water flux are long sought after attributes for reverse osmosis (RO) membranes.
Conventional RO membranes are composites consisting of polyamide thin films atop a microporous support. The polyamide thin film enables salt to be excluded to a high degree (as high as 99.8% under seawater conditions). However, due to the absence of well defined pores in the thin film, water permeability is modest at best. The pressures required to drive a significant flow through these membranes are consequently very large and thousands of square feet of membrane area are required to produce significant quantities of water. As a result of the high pressure requirements, conventional RO membranes are highly energy intensive.
NanOasis is using carbon nanotubes in membranes to increase membrane permeability by several-fold without loss of rejection. This permeability increase results in a significant reduction in the required energy to produce a given flow rate, along with decreasing membrane area requirements. Depending on the feed water salinity and the design of the particular RO system where the technology is implemented, the RO energy reduction could range from 30-50%, with a total water cost reduction of up to 40%.
