Filtering water using sand is a time-tested practice and endorsed by the World Health Organization (WHO). Now Australian researchers say the filtering properties of the sand are considerably enhanced when it is coated with a nanomaterial called graphite oxide (GO).
The team led by Dr Mainak Majumder from the Monash Department of Mechanical and Aerospace Engineering, together with researchers from Rice University in Houston, 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 discovery could prove a boon to millions in developing countries dogged by water pollution.
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.