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'Super sand' to help clean up dirty drinking water | 'Super sand' to help clean up dirty drinking water |
(3 days later) | |
Contaminated water can be cleaned much more effectively using a novel, cheap material, say researchers. | Contaminated water can be cleaned much more effectively using a novel, cheap material, say researchers. |
Dubbed "super sand", it could become a low-cost way to purify water in the developing world. | Dubbed "super sand", it could become a low-cost way to purify water in the developing world. |
The technology involves coating grains of sand in an oxide of a widely available material called graphite - commonly used as lead in pencils. | The technology involves coating grains of sand in an oxide of a widely available material called graphite - commonly used as lead in pencils. |
The team describes the work in the American Chemical Society journal Applied Materials and Interfaces. | The team describes the work in the American Chemical Society journal Applied Materials and Interfaces. |
In many countries around the world, access to clean drinking water and sanitation facilities is still limited. | In many countries around the world, access to clean drinking water and sanitation facilities is still limited. |
The World Health Organization states that "just 60% of the population in Sub-Saharan African and 50% of the population in Oceania [islands in the tropical Pacific Ocean] use improved sources of drinking-water." | The World Health Organization states that "just 60% of the population in Sub-Saharan African and 50% of the population 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 graphite-coated sand grains might be a solution - especially as people have already used sand to purify water since ancient times. |
Coating the sand | Coating the sand |
But with ordinary sand, filtering techniques can be tricky. | But with ordinary sand, filtering techniques can be tricky. |
Wei Gao from Rice university in Texas, US, told BBC News that 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. | 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," explained the researcher. | |
She said that the technique the team has developed to make the sand involves dispersing graphite oxide into water and mixing it with regular sand. | She 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." | "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." |
Cost-efficient | Cost-efficient |
The lead scientist of the study, Professor Pulickel Ajayan, 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. | The lead scientist of the study, Professor Pulickel Ajayan, 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. |
Another team member, Dr Mainak Majumder from Monash University in Melbourne, Australia, said it had another advantage - it was cheap. | Another team member, Dr Mainak Majumder from Monash University in Melbourne, Australia, said it had another advantage - it was cheap. |
"This material demonstrates comparable performance to some commercially available activated carbon materials," he said. | "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." | "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. | 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. | "This waste can be harnessed for water purification," he said. |