I find the carbon nanotube filtration more intriguing. The pores are literally too small for anything larger than water molecules to pass through. So it can remove salt from water, but it can also filter out microorganisms, poisons, metals, etc. Water flows through it 10,000 times more easily than through existing reverse osmosis membranes which require a lot of energy to force water through them.
That’s what I assumed the article would discuss - not a standard high school chemistry experiment.
I find it intriguing as well. It’s going to be expensive for a long time, whereas using a couple of carbon wires and 1.2Volts is already cheap.
Desalination: Energy Hog No More?
Copyright Burj Khalifa.
Porifera Inc. Innovation: Carbon Nanotubes
Desalination has long been the domain of arid, energy-rich states like those in the Persian Gulf thanks to its high-energy footprint. But as populations have boomed, as climate change makes water supplies more uncertain, and as clean water regulations are tightening on industry, more governments and businesses have been looking to desalination.
Efficiency and reallocation are much cheaper and sustainable options for obtaining new water supplies for municipalities. Water reuse in cities is also up and coming, as I will discuss in a future column. But the market to clean industrial wastewater of all kinds is booming.
For all these reasons, innovation in desalination has been continuing apace. At the Blue Tech Forum in San Francisco yesterday, Tyler Algeo, a research analyst at BlueTech Research, said that patents for desalination technologies in 2010 were double the number filed in 2005. Desalination energy inputs have been reduced more than 50 percent in the past decade.
Many entities are interested in these technology breakthroughs, said Algeo: large water technology corporations, venture capital firms, Fortune 500 companies, research groups, consulting engineering practices, and government agencies.
In addition to the Middle East, Australia, Algeria, and Spain now have major desalination programs, he said.
The Forum selected three companies with various approaches to desalination: carbon nanotubes, radial deionization, and biomimetic aquaporin membranes. Today I report highlights from the company that is innovating with carbon nanotubes. Look for the other two technologies in subsequent days.
Porifera Inc. is a two-year-old company based in Hayward, Calif. Vice president of business development, Jeffrey Mendelssohn, said it has achieved a breakthrough in forward osmosis membranes by using carbon nanotubes.
Reverse osmosis is a common filtration technology that uses a pump to push water through a filter. It can be energy intensive, which is why a lot of innovation is happening in forward osmosis.
Forward osmosis uses the thermodynamic law of entropy to separate solids from a fluid. Using a vessel separated into two compartments by a membrane filter, you put a dirty liquid on one side and clean water on the other. The water passes through the membrane until the percentage of solids on both sides is the same.
Forward osmosis works better in high fouling environments [severely contaminated water] much better than pressure-driven membrane processes [reverse osmosis] because particulate matter in high fouling environments will scrunch up against the membrane under pressure and cause membrane performance to fail, said Mendelssohn.
Poriferas membrane isnt just for desal, although Mendelssohn claims that it can perform salt rejection 10 times better than existing forward-osmosis processes. The company claims it has superior permeability, durability, and selectivity for water purification to other membranes. This innovation was reported in Science magazine in 2006 and was discovered at the Lawrence Livermore National Laboratory by a group of scientists led by Poriferas principal R&D team.
From its website:
Carbon nanotubes are seamless, atomically smooth carbon straws whose diameters range from less than a nanometer to tens of nanometers (a water molecule is ~0.3nm). Water flows through these unique pores 1,000 times faster than through any other pore of similar diameter. Moreover, gases also flow through the nanotubes pores more than 100 times faster than through any other nanometer scale pore. This reduction in flow resistance manifests itself in large enhancements of the membrane permeability and in drastic reduction of viscous losses.
Other applications include dewatering and water treatment of all kinds.
Markets include the Department of Defense, said Mendelssohn, which needs portable on-site desalination to reduce the number of water and fuel resupply convoys in Afghanistan.
The developing world is also a potent marketplace. Dubais famous Burj Khalifa skyscraper has no wastewater service, said Mendelssohn, like many newly developed areas of the city. Instead, tanker trucks remove sewage regularly. By installing an on-site water treatment and reuse facility, Porifera could reduce those truck trips by 90 percent, said Mendelssohn.
On the domestic market, the company could clean water from oil and gas hydrofracking at half the cost of current forward osmosis systems and also recycle the water for reuse onsite, said Mendelssohn.
Commercial elements will begin shipping in July, he said.