`Super` sand could improve water filtration

Ordinary sand, such as that from beaches, could be used to filter dirty waterusing a nanotech-based technique developed by researchers.

Sand, which retains bugs and chemicals in water flowing through it, has been used as a cheap water filtration method for hundreds of years. Coarse sand filters water faster than finer sand, but produces water that is less clean.

Now, a team of scientists in Australia and the United States has come up with a way to coat ordinary coarse sand with a nanomaterial called graphite oxide — which can remove five times more impurities than ordinary sand.

The graphite oxide is suspended in a liquid, to which the sand is added. This mixture is heated to ensure the sand is covered, and then dried.

Compared with untreated sand, the coated sand removed up to five times as much mercury and dye from water. The authors wrote that its activity was similar to that of activated carbon, a porous form of carbon that has a large surface area to absorb impurities but is expensive to make.

The method for treating the sand is simple and uses cheap materials such as sulphuric acid, making the technique likely to be used in developing countries, said Mainak Majumder, co-author of the study and a mechanical engineer at Monash University, Australia.

Although the sand used in the experiment was a commercially available filtration sand, any sand could be used provided it is cleaned beforehand, Wei Gao, a co-author of the research from Rice University, United States, told SciDev.Net.

The researchers have no plans to themselves test the sand in developing countries, as they do not have access to large-scale production methods, said Wei.

Thalappil Pradeep, a prominent nanotechnologist at the Indian Institute of Technology Madras, said he has also conducted research into using a similar material to graphite oxide to improve the filtration properties of sand. He said the biggest issue is translating the technique into a product that ordinary people can use.

'The technologies have to be applied to real products. In our case, one product is undergoing field trials incorporating such materials.'

The research was published in Applied Materials & Interfaces in May.