National Geographic Daily News

This picture was taking at a Banana Plantation in Costa Rica.  While I was there we got to walk around the plantation and see how everything was done.  It was really neat to see how much time it took to get all of the bananas ready for shipment.
A banana plantation in Costa Rica.

Christina DiPaola

Anne Minard

for National Geographic News

Published March 11, 2011

This story is part of a National Geographic News series on global water issues.

Banana peels are no longer just for composting or comedy shows: New science shows they can pull heavy metal contamination from river water.

Metals such as lead and copper are introduced to waterways from a variety of sources, including agricultural runoff and industrial wastes. Once there, heavy metals can contaminate soils and pose health risks to humans and other species. Lead is known to affect the brain and nervous system.

Traditionally, water quality engineers have used silica, cellulose, and aluminum oxide to extract heavy metals from water, but these remediation strategies come with high price tags and potentially toxic side effects of their own. They work as extractors due to the presence of acids such as those found in the carboxylic and phenolic groups, which attract metal ions.

(Read more: “Predicting the World’s Next Water Pollution Disaster.”)

Bananas, on the other hand, appear to be a safe solution. Banana peels also outperform the competition, says Gustavo Castro, a researcher at the Biosciences Institute at Botucatu, Brazil, and a coauthor of a new study on this new use of the fruit’s peel.

For the study, Castro and his team dried and ground banana peels, then combined them in flasks of water with known concentrations of metals. They also built water filters out of peels and pushed water through them.

In both scenarios, “the metal was removed from the water and remained bonded to the banana peels,” Castro said, adding that the extraction capacity of banana peels exceeded that of other materials used to remove heavy metals.

Previous work has shown that other plant parts—including apple and sugar cane wastes, coconut fibers, and peanut shells—can remove potential toxins from water.

Don’t Try This at Home

Castro doesn’t advise the use of banana peels for home water purification. For starters, the concentration of heavy metals in tap water is usually negligible. Also, while putting banana peels in contact with water will likely remove some metals, the average person isn’t likely to be able to measure success.

Castro said his study findings are most likely to be useful in industrial settings.

The new study appears in Industrial & Engineering Chemistry Research, a journal of the American Chemical Society.

The World's Water

The world's increasing population and development of agricultural land are putting pressure on the Earth's limited freshwater supplies. Find out what's at stake and how you can help.

  • Image: Water drops

    Why Should You Care?

    Learn more about the world's water challenge with photos, stories, videos, and more.

  • Image: Cow silhouette

    How Much Water Per Pound?

    How much water does it take to put beef, pork, wheat, and more on your plate? Explore our newest interactive and find out.

  • Photo: Iguaçu Falls

    Water Is Life

    Explore the pages of National Geographic magazine's special issue devoted to water.

  • water-calculator-tease.jpg

    Water Calculator

    Figure out your footprint, then join hundreds of website visitors who together have pledged to save thousands of gallons a day.

Learn More About Freshwater »

Posts From National Geographic Freshwater Fellow Sandra Postel

Read More Blog Posts From Sandra Postel »

Stories From Experts in the Field

Read More Stories »

Shop National Geographic

SHOP NOW »

Discover Your Roots

  • 9286.jpg

    Your Genealogy

    Everyone on Earth is ultimately part of the same human family. Take what you know of your branch and discover more than you ever thought possible.

  • 9295.jpg

    Genetics

    Learn about what's passed on from generation to generation with an interactive look at DNA.