Save those apple peels! A research team from the National University of Singapore (NUS) has developed an innovative way to purify water, based on apple peels. As an inexpensive, low-energy bioremediation system the apple peel approach could be useful in remote communities where electricity and money are both in short supply. The research actually started out with tomatoes before moving on to apples, so who knows what other fruit might be waiting in the wings to do battle against water pollution.
Bioremediation By Fruit
The new study has roots in research conducted at NUS last year that focused on the tomato, specifically on the peel (that study was published in the Royal Society of Chemistry journal RSC Advances in September 2012).
As for why tomato peels, according to the NUS team tomatoes are the world’s second most-consumed vegetable. Copious amounts of skin, seeds and other fibers are available as leftover waste when tomatoes are canned or processed into other food products, which makes it a widely available and relatively cheap material to work with.
To grasp how tomato peels can be used to remove contaminants from water, it’s helpful to know the difference between an absorbent and an adsorbent.
Loosely speaking, absorbent refers to a physical process in which a relatively bulky material captures liquid in chambers throughout its interior, the classic example being a sponge.
Adsorbent describes a similar phenomenon, but on a nanoscale that focuses on chemical interactions on the surface of the material. Think activated carbon filters and you’re on the right track.
It turns out that tomato peels are a lousy absorbent (you can check that out at home for yourself), but they are a fantastic adsorbent in terms of their ability to remove metal ions and organic pollutants in water, including dissolved organic and inorganic chemicals, dyes and pesticides.
Apple Peels And Bioremediation
Moving right along to apple peels, in a study published recently in the American Chemical Society’s journal Applied Materials & Interfaces, the NUS team doped the surface of the peels with zirconium oxides, which enhanced their ability to adsorb negatively charged pollutants in water.
The new study found that the supercharged peels efficiently removed phosphate, aresenate, arsenite and chromate ions.
Why Stop There?
The NUS team will be looking at other fruits for low cost bioremediation, and don’t be surprised if banana peels make the list.
A banana bioremediation project in Brazil shows promise as an inexpensive, chemical-free way to remove metals from wastewater, as do coconut fibers and peanut shells.
Another food based bioremediation approach is illustrated by research into the effectiveness of vitamin B-12 and the milk derivative potassium lactate for removing volatile organic compounds from soil, the theory being that they rev up the natural process of bacterial bioremediation.
And then there’s plant-based bioremediation, in which fast-growing vegetation like cattails and poplar trees are used to suck pollutants out of soil and marshy areas. As an added benefit, bioremediation crops could double as biomass for biofuel refineries.
Aside from removing metals and other toxic substances from water, bioremediation is also becoming increasingly common in human wastewater treatment, in the form of managed wetlands.
All this is by way of finding low-energy, chemical-free ways to deal with industrial and human waste. When you consider the energy involved in traditional dig-and-dump remediation and wastewater treatment, that adds up to a significant savings.