Researchers at India’s Institute of Technology Madras have developed a new kind of portable water purification system based on nanoparticle filtration. In their paper published in the Proceedings of the National Academy of Sciences, the team explains how their new device does its job–it employs nanoparticles to remove not just biological hazards, but toxic heavy metals as well.
The researchers note that access to clean drinking water is still a major worldwide problem–making it available to everyone, they say, would save approximately 2 million lives a year (approximately 42.6 percent of deaths are due to diarrhea alone and impact mostly children). To help reach the UN millennium development goal of doubling the number of people with sustainable access to safe drinking water by 2015, the team has been applying nanoparticle technology to the problem.
The system they have developed is a two-stage filtration process that provides 10 liters of clean water in just an hour’s time. The biggest challenge, the team says, was figuring out how to deliver silver ions into the water to be processed, without using any electricity. The process also had to use a minimal amount of silver ions to meet international safety standards. The answer, they say, was to use a new material that employs silver nanoparticles that are trapped in tiny cage-like structures made of other clay materials.
Other nanoparticles are used to create other materials that serve as filters, killing microbes and sucking heavy metals out of the water, making it safe to drink or use for cooking. The first stage of the process kills viruses, bacteria and other dangerous micro-biota. The second stage absorbs heavy metals such as lead and arsenic.
The result is an extremely inexpensive portable water purification device–the system cost is comparable to other portable filtration systems, but the processing itself comes to less than $3 per year. The filters are good for approximately one year (3,600 liters) and filtration can be run more than once per day if needed. The researchers believe their device is capable of providing all the drinking water a family of four would need.