As stated by Thalappil Pradeep - a material scientist at the Indian Institute of Technology (IIT) Madras, and senior author of a journal entitled Proceedings of the National Academy of Science (PNAS) - when describing a new filter - "we wanted to show that it is possible to deliver affordable clean water that had all of the contaminants removed,"
On average it is predicted for contaminated water (H2O) to contain bacteria, viruses, protozoa, heavy metals, pesticides, or other potential toxins. The Indian researchers knew that Silver (Ag) ions released from the metal into a nanoparticle form, worked as a disinfectant for a number of bacteria and viruses found in contaminated H2O, while other inorganic toxins, such as Lead (Pb), Iron (Fe) and Arsenic (As), can be scavenged from contaminated H2O with materials containing different chemical properties, particular to each of those elements.
However, contaminants found in the H2O tend to anchor to nano-Ag surfaces, blocking the release of Ag ions for them. To overcome such an issue, the researchers created an unique family of nano-crystalline metal oxyhydroxide-chitosan granular composite materials. This material, which forms a cage-like matrix, strongly bonds to embedded nanoparticles. The nanoparticles remain isolated inside the matrix, which only allow ions to escape at a controlled rate. Such ions then kill microbes found in H2O, without releasing nanoparticles.
The materials can all be prepared at room temperature (RT) in H2O, and they gradually settle to form a 'sand-like' material, whereby no electricity is required and all of the elements needed to build the filters are widely available/affordable. For instance, for each liter of H2O required to make the composite, 500 liters of clean water can be produced. In addition, none of the composite materials themselves are toxic, and when the material eventually stops releasing Ag ions, hot H2O can get rid of the thin layer of scalants to regain activity in the composite. It is anticipated that such purifiers would cost small families about US $2.50/year.
Pradeep's goals are to produce the filters in the remote villages where they can provide the most value. Already 2,000 small community-scale units are being installed in west Bengal, an area plagued by As contamination in its H2O. Pradeep believes the filters could be deployed to more than 2 million people over the next two years or so, though other organisations will have to take responsibility for organising such efforts. It is anticipated the same technology could eventually be employed in other developing nations as long as tests were carried out to customise the filters to each particular country's conditions. If everything goes as planned, then the new composites could even provide a potential solution for achieving the United Nations (UN) millennium development goal of doubling the number of people with sustainable access to safe drinkable water by 2015.
Pradeep concluded with stating - "people talk about nanotechnology from the context of advanced computing and high density data storage," - "those are important, but at the same time frugal science is also important, and can make a larger impact in the short-term." Original article available here
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