One of the ways to provide clean drinking water is to desalinate seawater. The Korea Institute of Civil Engineering and Building Technology KICT has announced the development of a stable performance electrospun nanofiber membrane to turn seawater into drinking water by membrane distillation process. Membrane wetting is the most challenging issue in membrane distillation.
If a membrane exhibits wetting during membrane distillation operation, the membrane must be replaced. Progressive membrane wetting has been especially observed for long-term operations. If a membrane gets fully wetted, the membrane leads to inefficient membrane distillation performance, as the feed flow through the membrane leading to low-quality permeate.
Yunchul Woo, has developed co-axial electrospun nanofiber membranes fabricated by an alternative nano-technology, which is electrospinning. This new desalination technology shows it has the potential to help solve the world's freshwater shortage. The developed technology can prevent wetting issues and also improve the long-term stability in membrane distillation process. A three-dimensional hierarchical structure should be formed by the nanofibers in the membranes for higher surface roughness and hence better hydrophobicity.
The co-axial electrospinning technique is one of the most favorable and simple options to fabricate membranes with three-dimensional hierarchical structures. Woo's research team used poly vinylidene fluoride-co-hexafluoropropylene as the core and silica aerogel mixed with a low concentration of the polymer as the sheath to produce a co-axial composite membrane and obtain a superhydrophobic membrane surface.
In fact, silica aerogel exhibited a much lower thermal conductivity compared with that of conventional polymers, which led to increased water vapor flux during the membrane distillation process due to a reduction of conductive heat losses. Most of the studies using electrospun nanofiber membranes in membrane distillation applications operated for less than 50 hours although they exhibited a high water vapor flux performance.
On the contrary, Dr. Woo's research team applied the membrane distillation process using the fabricated co-axial electrospun nanofiber membrane for 30 days, which is 1 month.
The co-axial electrospun nanofiber membrane performed a Based on the results, the membrane operated well without wetting and fouling issues, due to its low sliding angle and thermal conductivity properties.
Temperature polarization is one of the significant drawbacks in membrane distillation. It can decrease water vapor flux performance during membrane distillation operation due to conductive heat losses. The membrane is suitable for long-term membrane distillation applications as it possesses several important characteristics such as, low sliding angle, low thermal conductivity, avoiding temperature polarization, and reduced wetting and fouling problems whilst maintaining super-saturated high water vapor flux performance.
Woo's research team noted that it is more important to have a stable process than a high water vapor flux performance in a commercially available membrane distillation process. Water Can Heal. Contaminants Facts. Air and Health. Water Filtration or Purification — Key Differences Why do we need to remove chlorine from our whole house?
Top 5 Hard Water Problems for Homeowners. See Also. More related topics:. Where is the Saltiest Water on Earth? That's if the technology makes it out of the laboratory. One issue with desalination is what to do with the leftover salt.
Water in the Persian Gulf historically was 35, parts per million ppm salt. But according to the United Arab Emirates' Ministry of Environment and Water, some areas nearest desalination plants now measure 50,ppm.
Jessica Jones from Poseidon Water, the firm building California's Carlsbad Desalination Plant, says: "Our plant is co-located with a power plant which uses sea water for cooling. Our discharge gets blended in, so by the time it goes into the ocean, the salt has been dispersed. But US environmental groups have fought construction of new desalination plants in the courts, saying the consequences of reintroducing brine to the ocean have not been adequately studied.
Desalination may be getting cheaper but it is still prohibitively expensive for poorer countries, many of whom also suffer from water scarcity.
More than two-fifths of Africa's million people live in "water-stressed" areas, defined as providing less than 1, cubic metres of water per person, taking the needs of industry and agriculture into account as well.
And the United Nations predicts that in 10 years 1. What water-stressed regions most need is a desalination device than can supply to people - the size of a village. Capacitive desalination is one potential solution, as is solar-powered desalination, with costs reducing threefold in 15 years. So while desalination has gone big in wealthier countries, it also needs to go small to benefit those unlucky enough to be poor in both money and water.
Image source, Getty Images. Most of this freshwater needs to be purified to be safe for human consumption. With a rapidly growing population, it is no surprise that millions of people in the world do not have access to safe drinking water.
Half a billion people experience it all year round. Lack of access to safe freshwater creates or contributes to a host of problems. The most obvious one is disease. People who do not have access to safe drinking water have to get their water from unreliable sources, which often makes them sick.
The World Health Organization WHO estimates that at least 2 billion people globally drink water from sources contaminated with feces. Another problem is that people, often women and girls, must travel long distances to get to these water sources. This takes time that could have been spent studying for children or working, thus trapping communities in a cycle of poverty. Women and girls are also in danger of being attacked during these long walks.
Many communities facing water scarcity do have access to an abundant water source — the sea. Seawater is not suitable for human consumption, but a solution does exist: desalination. Desalination is the process of removing salt from seawater, making it drinkable. This is done either by boiling the water and collecting the vapor thermal or by pushing it through special filters membrane. The problem is that this process requires vast amounts of energy, making it unaffordable for impoverished communities and exacerbating climate change.
Back in the Netherlands, Vollebregt enlisted his friend and fellow engineering student Reinoud Feenstra to work on developing a desalination technology powered by renewable energy. The result was a system that relies on solar or other renewable energy to treat water, thus making desalination carbon-free. This makes it both much more affordable and sustainable.
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