Purer water from “super sand”

Purer water from “super sand”

MONASH UNIVERSITY

Sand has been used to clean polluted water for six millennia. Image: Kuzma/iStockphoto A low-cost coating applied to sand could provide a source of wide-scale water purification to people in developing countries, saving millions of lives every year. Sand, an abundant natural resource, has been used to clean polluted water for six millennia. Filtration using sand in its natural form is endorsed by the World Health Organization (WHO), as a water purification process. Now, a team led by Dr Mainak Majumder from the Monash Department of Mechanical and Aerospace Engineering, together with researchers from Rice University in Houston, have significantly enhanced the natural filtering properties of sand by coating it with a nanomaterial called graphite oxide (GO). The researchers changed the structure of graphite, a material found in pencils, to dramatically increase its surface area before coating coarse grains of sand. Increasing the surface area of the sand caused a corresponding increase in the material’s ability to filter contaminants. The research, published recently in ACS Applied Materials & Interfaces, indicated that untreated sand became saturated after ten minutes of filtration, while the GO-coated ‘super sand’ absorbed contaminants for more than 50 minutes. Dr Majumder said the super sand’s performance was comparable to some commercially available activated carbon materials, which are used for filtration purposes. “By increasing its surface area, we’ve improved the filtering capability of sand so that it is not only more effective in removing contaminants, but still filters relatively quickly, making it a viable option for water purification.” Dr Majumder said the other big advantage of the super sand is that it is relatively cheap to produce. “Given that the functional carbon can be synthesised using room temperature processes and also from cheap graphite sources, such as mining by-product, it is likely to be cost-efficient.” Access to clean water is a significant challenge for the global population. The WHO reports that, annually, access to safer water could prevent 1.4 million deaths from diarrhoea; 500,000 deaths from malaria and 860,000 deaths from malnutrition.  “We hope that in the future our technology will help to improve the living conditions of people facing water scarcity”, said Dr Majumder.