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Carbon Nanotube Membrane Elements for Energy Efficient and Low Cost Reverse Osmosis

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NanOasis Technologies has received $2 million in DOE funding in the ARPA-E program to develop "Carbon nanotubes for reverse osmosis membranes that require less energy and have many times higher flux. Could dramatically reduce the cost and energy required for desalination to supply fresh water for our crops and communities." Water supplies in most of the world are threatened and finding supplies of fresh clean water is a critical worldwide need.

They are one of several companies pioneering the use of carbon nanotubes in reverse osmosis membranes. They claim their technology "substantially lowers energy use, size and capital requirements for desalination, and other water purification and fluid separations applications." The technology is based on work by Dr. Jason Holt, co-founder of NanOasis, following his work at Lawrence Livermore National Laboratory.

NanOasis membranes consist of a thin, dense polymer film having carbon nanotube pores (or holes) atop a highly porous support. The super smooth inside of the nanotubes allow liquids and gases to rapidly flow through, while the tiny pore size can block larger molecules. By filtering out larger molecules it automagically purifies water.

Membranes that have carbon nanotubes as pores could be used in desalination and demineralization. Salt removal from water, commonly performed through reverse osmosis, uses less permeable membranes, requires large amounts of pressure and is quite expensive. However, these more permeable nanotube membranes could reduce the energy costs of desalination by up to 75 percent compared to conventional membranes used in reverse osmosis.

One of the main problems with reverse osmosis desalination tech to date has been that the basic process of pumping water and forcing it through a membrane to separate out the salt is highly energy-intensive, making for a high cost. The energy (electricity primarily) is used to pump water at high pressure through membranes. That electricity accounts for perhaps 44 percent of the cost of reverse osmosis desalination. The LLNL announcement of Dr. Holt's earlier work claims "these more permeable nanotube membranes could reduce the energy costs of desalination by up to 75 percent compared to conventional membranes used in reverse osmosis."

NanOasis Technologies

Nanotube membranes offer possibility of cheaper desalination

Cheap Drinking Water from the Ocean

Beyond Salt: Desalination Startup NanOasis Eyes Wider World of Clean Water

References: 

Review: Flow: For Love of Water (2007)

An astonishingly wide-ranging film. An informed and heartfelt examination of the tug of war between public health and private interests. The story is about water supply, and it covers the global scale of this problem.

References: 

Freshwater @ UNEP

Description: 

An information portal operated by the UN Environmental Programme, concerning fresh water and water resources.

About one-third of the world's population lives in countries with moderate to high water stress. The problems are most acute in Africa and West Asia but lack of water is already a major constraint to industrial and socio-economic growth in many other areas, including China, India and Indonesia. If present consumption patterns continue, two out of every three persons on Earth will live in water-stressed conditions by the year 2025. The declining state of the world's freshwater resources, in terms of quantity and quality, may prove to be the dominant issue on the environment and development agenda of the coming century.

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