Chemistry- Purifying Water

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In our search for prosperity, growth and success, we are destroying the system that we as human are completely dependent upon. Population growth, water-intensive agriculture and economic development are using water faster than it can be replenished. Our Earth is a place where beauty exists, a place where 6.6 billion people and 15 million other species live, a place filled with 1.4 cubic kilometers of water. Although 70% of the planet’s surface is blanketed with deep oceans water, freshwater only form less than 3% of the total water and the rest are saltwater. Besides that, only 30% of the freshwater are not being lock up in ice cups and glaciers. Another 20% are in certain areas that are too remote for human to access and the remaining 80% comes from the monsoon or floods. That leaves us with less than 1% of usable water from lakes, rivers and underground sources. Nevertheless, Science has helped mankind to solve this problem and one of the current approaches being explored in many countries, including South Africa is nanotechnology. Nanotechnology has developed widely in the past few years and was able to create new materials with a great range of potential applications. One of these new materials are carbon nanotubes and researchers find that these tubes can be used to clean the polluted water. Nano tubes are molecular-scale and are wrapped with graphitic layers. http://ipn2.epfl.ch/CHBU/NTprimer.htm

http://ipn2.epfl.ch/CHBU/NTprimer.htm

They are called “Nano” because of their sizes that are roughly billion times smaller than a meter. Normally they are very thin and have hollow cylindrical structures made out of carbon atoms. However, they still exist in various shapes such as cylinders, spheres, cones, tubes and also complicated shapes. Carbon nanotubes have exceptional thermal, electrical and mechanical properties, allowing them to be widely used in numerous industries. This device works through a filtration process called size exclusion. Size exclusion is one of the chromatography methods to separate molecules. Using this method, molecules of different compound are separated according to their size or molecular weight. Normally see water will consist of inorganic ions such as magnesium bromide, potassium chloride, calcium chloride, sodium chloride, magnesium chloride and water itself. Pure water is composed of two hydrogen atoms bonded to a single atom (H20), hydronium ions and hydroxide ions. The oxygen in pure water basically came from the atmosphere and also it comes from the aquatic plants present in the water bodies. All of these compounds in water have different sizes of molecules and the unique properties of these nanotubes is that they only allow water molecules to pass through the interior of the cylinders while chemical and microbial contaminants could not. The tubes are packed near together and the water flows through them like it flows through straws. The opening of the tubes is so small, which is a few nanometers wide that even bacteria, biological material and other impurities get cleaned out of water because they could not fit the tube where water molecules can. Water molecules could pass through is because they are smaller in size and weight.

Sodium and chloride are the two main ions in saltwater where at 19,000 ppm for chloride and 10,500 ppm for sodium, they consist 54% and 30% of the total weight of ions in seawater. The next two most common ions are magnesium and sulfate and together, these four ions comprise almost 96% of the weight of ions present in seawater. When the water passes through this tubes, salt ions, cells, viruses and microorganism get pushed to side. The saltier water is then drawn off, leaving only de-salted water to pass through. Nanotubes give many implications toward our economy and environment. The main advantage of carbon nanotubes is that water flows through them at a rate 1,000 times faster compared to polymer-based that are normally being used in water...
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