Scientists develop 'super sand' to clean dirty water

Scientists develop 'super sand' to clean dirty water

The special sand which is coated with an oxide of graphite -- commonly used as lead in pencils -- could become a low-cost way to purify water in the developing world, the researchers said.

Access to clean drinking water is still limited in a number of countries in the world. And according to WHO, only 60 per cent of the population in Sub-Saharan Africa and 50 per cent in Oceania (islands in the tropical Pacific Ocean) use improved sources of drinking-water."

The graphite-coated sand grains might be a solution -- especially as people have already used sand to purify water since ancient times, the BBC New reported.

Professor Pulickel Ajayan, of Rice University, who led the study, said it was possible to modify the graphite oxide in order to make it more selective and sensitive to certain pollutants -- such as organic contaminants or specific metals in dirty water.

But ordinary sand, filtering techniques can be tricky, said the researchers who detailed their study in the American Chemical Society journal Applied Materials and Interfaces.
Study co-author Dr Wei Gao said regular coarse sand was a lot less effective than fine sand when water was contaminated with pathogens, organic contaminants and heavy metal ions. While fine sand is slightly better, water drains through it very slowly.

"Our product combines coarse sand with functional carbon material that could offer higher retention for those pollutants, and at the same time gives good throughput," she explained.

Dr Gao said that the technique the team has developed to make the sand involves dispersing graphite oxide into water and mixing it with regular sand.

"We then heat the whole mixture up to 105C for a couple of hours to evaporate the water, and use the final product -- 'coated sand' -- to purify polluted water."

Another team member, Dr Mainak Majumder from Monash University in Melbourne said it had another advantage -- it was cheap.

"This material demonstrates comparable performance to some commercially available activated carbon materials," he said.

"But given that this can be synthesized using room temperature processes and also from cheap graphite sources, it is likely to be cost-efficient."

He pointed out that in Australia many mining companies extract graphite and they produce a lot of graphite-rich waste. "This waste can be harnessed for water purification," he said.

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