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yexuqing木虫之王 (文学泰斗)
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【转帖】低成本将海水变淡水已有7人参与
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低成本将海水变淡水 将海水转化为淡水的一个重要步骤是脱盐，但这是一个高能耗的过程，或者说只有大规模生产才有效率，因此在灾难发生时或者贫穷地区，这种方式是很难发挥作用的。现在，研究人员发明了一种新设备，只需使用电池就可以将海水转化为淡水，新成果发表在3月在线出版的《自然—纳米技术》期刊上。 浓差极化是指当水透过膜并截留盐时，在膜表面会形成一个流速非常低的边界层，边界层中的盐浓度比进水本体溶液盐浓度高，这种盐浓度在膜面增加的现象叫做浓差极化。当一束离子通过一个离子选择性纳米通道时，离子会发生浓差极化现象。Jongyoon Han和同事发明了一种可以利用这种现象的纳米装置。他们将这种纳米管道安置在两个装有海水的微型管道中，当电压加在纳米管道上时，海水中的盐离子浓度在纳米管道的一端增加，而在另一边却被耗空了。结果，在纳米管道附近，海水中的盐离子被清空了。在这个分离区域中将其中一个微型管道分离出来，海水中的盐份就会被去除，没有电荷的无盐海水就能通过通电区域，进入淡水管道。 新方法可以让盐和细胞、病毒及微生物等大颗粒在低能耗情况下被去除，其效率相当于现代最新的大规模装置。 |
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xiexiong77
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2楼2010-03-30 09:22:55
gaofeng925
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3楼2010-03-30 09:36:09
welcomeboog
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4楼2010-04-07 16:54:03
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小木虫(金币+0.5):给个红包，谢谢回帖交流
小木虫(金币+0.5):给个红包，谢谢回帖交流
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我把英文的也贴一下吧，呵呵。这个感觉还是很有意思的，为了搞懂这个概念我还特意去看了看参考文献。 Potable water is often in high demand and short supply following a natural disaster like the Haiti earthquake or Hurricane Katrina. In both of those instances, the disaster zones were near the sea, but converting salty seawater to potable fresh water usually requires a large amount of dependable electrical power and large-scale desalination plants — neither of which were available in the disaster areas. A new approach to desalination being developed by researchers at MIT and in Korea could lead to small, portable units that could be powered by solar cells or batteries and could deliver enough fresh water to supply the needs of a family or small village. As an added bonus, the system would also remove many contaminants, viruses and bacteria at the same time. The new approach, called ion concentration polarization, is described in a paper by Postdoctoral Associate Sung Jae Kim and Associate Professor Jongyoon Han, both in MIT’s Department of Electrical Engineering and Computer Science, and colleagues in Korea. The paper was published on March 21 in the journal Nature Nanotechnology. One of the leading desalination methods, called reverse osmosis, uses membranes that filter out the salt, but these require strong pumps to maintain the high pressure needed to push the water through the membrane, and are subject to fouling and blockage of the pores in the membrane by salt and contaminants. The new system separates salts and microbes from the water by electrostatically repelling them away from the ion-selective membrane in the system — so the flowing water never needs to pass through a membrane. That should eliminate the need for high pressure and the problems of fouling, the researchers say. The system works at a microscopic scale, using fabrication methods developed for microfluidics devices — similar to the manufacture of microchips, but using materials such as silicone (synthetic rubber). Each individual device would only process minute amounts of water, but a large number of them — the researchers envision an array with 1,600 units fabricated on an 8-inch-diameter wafer — could produce about 15 liters of water per hour, enough to provide drinking water for several people. The whole unit could be self-contained and driven by gravity — salt water would be poured in at the top, and fresh water and concentrated brine collected from two outlets at the bottom. That small size could actually be an advantage for some applications, Kim explains. For example, in an emergency situation like Haiti’s earthquake aftermath, the delivery infrastructure to get fresh water to the people who need it was largely lacking, so small, portable units that individuals could carry would have been especially useful. So far, the researchers have successfully tested a single unit, using seawater they collected from a Massachusetts beach. The water was then deliberately contaminated with small plastic particles, protein and human blood. The unit removed more than 99 percent of the salt and other contaminants. “We clearly demonstrated that we can do it at the unit chip level,” says Kim. The work was primarily funded by a grant from the National Science Foundation, as well as a SMART Innovation Centre grant While the amount of electricity required by this method is actually slightly more than for present large-scale methods such as reverse osmosis, there is no other method that can produce small-scale desalination with anywhere near this level of efficiency, the researchers say. If properly engineered, the proposed system would only use about as much power as a conventional lightbulb. Mark A. Shannon of the Center of Advanced Materials for the Purification of Water with Systems at the University of Illinois at Urbana-Champaign, who was not involved in this work, agrees with that assessment. In a News & Views piece that accompanies the Nature Nanotechnology paper, he writes that the new system achieves “perhaps the lowest energy ever for desalinating microliters of water,” and when many of these micro-units are combined in parallel, as Kim and his co-authors propose, “it could be used to supply liters of water per hour using only a battery and gravity flow of water.” That meets a significant need, he says, since at present there are few efficient methods for small-scale desalination, both for emergencies and for use in remote areas in poor countries. Alex Iles, a research scientist at the University of Hull in Britain, says that while further testing must be done to establish long-term stability and fabrication techniques, “This is an elegant new concept for water desalination.” He says it is likely to produce a low-cost, low-maintenance system that could be “ideal for applications such as disaster relief.” When it was initially presented at a conference he attended last year, Iles says, “I thought it was probably the most significant new work at the entire conference, even though it was only a poster.” The basic principle that makes the system possible, called ion concentration polarization, is a ubiquitous phenomenon that occurs near ion-selective materials (such as Nafion, often used in fuel cells) or electrodes, and this team and other researchers have been applying the phenomenon for other applications such as biomolecule preconcentration. This application to water purification has not been attempted before, however. Since the separation occurs electrostatically, it doesn’t work for removing contaminants that have no electric charge. To take care of these remaining particles — mostly industrial pollutants — the researchers suggest the unit could be combined with a conventional charcoal filter system, thus achieving pure, safe drinking water through a single simple device. Having proved the principle in a single-unit device, Kim and Han plan to produce a 100-unit device to demonstrate the scaling-up of the process, followed by a 10,000-unit system. They expect it will take about two years before the system will be ready to develop as a product. “After that,” says Kim, “we’ll know if it’s possible” for this to work as a robust, portable system, “and what problems might need to be worked on.” |
5楼2010-04-09 08:36:08
fancy2007
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6楼2010-04-09 13:21:01
wanghc1988
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7楼2010-04-09 13:59:16
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8楼2010-04-09 16:03:44
9楼2010-04-09 18:57:17
davidhu927
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10楼2010-04-09 22:13:35