Cholera, typhoid and hepatitis are among the waterborne diseases that are a continuing problem in the developing countries where people lack access to clean, safe drinking water and the disease spreads mainly through water.
Researchers of Stanford University have developed a filter for purifying water which is faster than existing filters. A cotton cloth coated with nanotubes and silver nanowires is used as a filter material. The filter has no moving parts and is used after being electrified with very low power. It is claimed that it could be used by the developing countries. Conventional filters physically trap bacteria, push water through filters with electric pumps and consume a lot of energy, but the nanofilter allows them to flow along with the water, but by the device kills them with an electrical field set up by the highly conductive nanosilver coated cotton filter. Researchers claim that the new filter could be used in water purification systems from cities to small villages and in remote areas where there is no access to chemical treatments such as chlorine. Conventional filters have very small pore spaces to physically trap bacteria which restricts water flow, but nano filter has a large pore to allow more water up to 80,000 times faster, but at the same time destroying disease causing pathogens effectively without getting clogged, which is a problem with filters that physically trap bacteria out of the water.
Construction
The principle used is that silver and electricity can destroy bacteria. In the developed filter the advantage of nanomaterials is that due their small size they stick to the cotton easily. The nanosilver wires range from 40 to 100 billionths of a meter in diameter and up to 10 millionths of a meter in length. Because the nanomaterials stick so well, the nanotubes create a smooth, continuous surface on the cotton fibers. The longer nanowires generally have one end attached with the nanotubes and the other end branching off, poking into the void space between cotton fibers. Due to the continuous structure along the length, the electrons move very efficiently and make the filter very conducting using only less voltage. Initial tests indicate that this new filtering technology is inexpensive and kills up to 98 percent of disease-causing bacteria in water in seconds without clogging. Such technology could dramatically lower the cost of a wide array of filtration technologies for water as well as food, air, and pharmaceuticals where the need to frequently replace filters is a large cost and difficult challenge.