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Mopping up with food scraps

By , 14 December 2012


Waste from processing onions may be able to clean up heavy metal pollution.
Image: Willem van Aken/CSIRO

Do you have left over fruit and vegetable scraps? One day you might be able to use them to clean up the environment!

While we won’t be using lettuce leaves and potato peel to mop up oil spills any time soon, scientists in India have used waste from onion and garlic canning to remove pollutants from wastewater.

The pollutants in question are heavy metal ions, such as lead, cadmium and mercury. These ions are highly toxic to both humans and wildlife, so their presence in the environment is bad news.

Using biological material known as ‘biomass’ from the onion and garlic, scientists tested to see if heavy metal ions could be removed from industrial wastewater. The researchers changed a few variables, including pH (acidity), temperature and pollutant concentration, to determine the best conditions for removing pollutants.

For example, the scientists found that for a particular concentration of heavy metal ions at a temperature of 50°C and pH of 5, more than 70% of the lead ions could be removed from the water and recovered from the biomass using nitric acid. The biomass could then be reused to remove more heavy metal ions. This could hopefully lead to better methods of reducing heavy metal pollution.

This experiment indicates how important it is for scientists to consider all possible variables when doing their research. In order to get a clearer picture of what is going on, scientists will often repeat experiments with slight variations in conditions and compare the results.

Cleaning up pollution is hard work. Traditional methods such as physically removing polluted soil are very expensive and may not completely solve the problem. Using waste biomass is appealing because it is cheaper and in some cases may be more effective at removing the pollution.

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