Water Filtration System Was Developed Using Just Fruit and Vegetable Peels
The low-cost organic technique can filter out other heavy metals like Mercury too.
by Matthew PhelanThis sounds like we’re about to try to sell you some healing crystals, but it’s real: chemists at universities in the United States, India, and Singapore have been developing amazing, organic, and low-cost water filtration methods involving cellulosic fruit and vegetable waste. Though still in its early stages, their research could be a potential game-changer, particularly for the roughly 780 million people worldwide who lack access to an improved water system.
At the heart of this emerging strategy is a chemical process called adsorption — which is not a typo — but actually a unique, surface-layer only, material-bonding process that’s distinct from absorption. You can think of this way: When a sponge absorbs water, that water permeates the whole volume, whereas with adsorption, the material in question (solid, liquid, gas, whichever) binds or is added to the surface of the adsorbent, hence ad-sorption.
Suresh Valiyaveettil, an associate professor of chemistry at the University of Singapore, has been conducting research on the properties of these fruit and vegetable peel materials since at least his 2015 paper in the journal International Biodeterioration & Biodegradation. But last month, he published a new collaboration with Dickinson College chemistry professor Cindy Samet on how to teach these same methods to undergraduate general chemistry students as a lab exercise.
That’s how easy this is. You can teach teens do it. You can do it in your kitchen with your crunchy friend from the summer CSA. Visiting grandma and grandpa this summer? You can do this with them too.
In a matter of hours, methylene blue dye, seen in the right bottle, was removed from the bottle at left with dried and ground avocado peels. Molecules of the dye adhere to the surface of the peel material via process called adsorption.
How the Fruit Filters Actually Work
Following the procedure established by Valiyaveettil in Singapore, Samet and her students first removed water-soluble impurities from the surface of the peels, as well as from adsorbent seeds, first by boiling them, then by drying them. They were then crushed to increase their interactive surface area while in the contaminated water.
“We replicated the results from Suresh’s lab with avocado and then studied never-before-tested fruits and vegetable peels and seeds,” Samet explained in a statement. “This is exciting because it is likely that this method of purification can make its way from lab to kitchen.”
Specifically, she and her Dickinson undergraduates found that lemon seeds where capable of removing 100 percent of lead-ion contaminants, while lemon peels removed 96.4 percent. Okra peels too proved equally impressive, removing 100 percent of the lead ions in water. Okra seeds, however, only removed 50 percent.
Samet's class (like other researchers interested in environmental remediation and water quality) have been testing a variety of fruit and vegetable peels as "cellulosic low-cost biosorbents.' Some that have been found to work include rice husks, banana peels, corn stalks and corn silk, hazelnut shells, mango peels, and many others.
There’s actually a growing body of this research. Mango and orange peels, it turns out, have shown some efficacy in removing lead ions — 99 milligrams-per-gram of peel and 75 milligrams milligrams-per-gram of peel — as well as in removing significant amounts cadmium, nickel, copper, and others. A 2012 study showed that sunflower stalks could pull roughly 182 milligrams of lead ions per gram of peel.
The amount of otherwise disposable plant matter that researchers are trying this out on, with exciting results, is sort of bewildering; peat moss, apricot stones, pine, hemp fibers (hell, yeah), bamboo leaf powder, something called grape bagasse.
It’s a lot to take in, but the core idea is that these materials are ultimately cheaper and, in the right combination, as effective or better than industrially manufactured activated charcoal that’s common in water filtration today.
Samet hopes that her work with her students will lead to something that people can do at home in their kitchen to improve their water quality all over the world. But, in the meantime, there is a lot of basic experimentation to do.
“It’s great to have a repertoire of different big projects with a similar theme of food, sustainability and green chemistry,” as she put it in an interview with Dickinson at the start of her project. “This field of research gives us enough to work with, really, for years.”
