Food waste is on everyone’s minds these days, as culinary and scientific communities around the world unite to make headway on this urgent problem. Recent studies from Spain’s University of Granada and Mexico’s Electrochemical Research and Technological Development and Center of Engineering and Industrial Development suggest that a regularly discarded resource may prove useful in the water filtration process. That’s right: Citrus peels clean wastewater, perhaps even as effectively as activated charcoal. Could orange be the new gold?
About 38 million tons of citrus peels, considered to be “residue” of the food system, are thrown away every year worldwide, and while they decompose fairly easily, that’s no reason not to harness their secret water filtration powers. A surface treatment called Instant Controlled Pressure Drop modifies the peels to become porous by increasing their surface area. This new texture readily adsorbs metals and other pollutants. Adsorption, unlike absorption, causes particles to adhere to the surface of the modified citrus peels rather than “soaking into” it.
What’s the advantage of causing the peels to attract these particles rather than absorb them? The answer is both smart and lucrative — and who said solving food waste couldn’t be a moneymaker, too? Once the first part of the process is complete, a second chemical treatment effectively harvests the peels’ pollutant coating. Those toxic metals don’t break down and are in fact valuable and able to be resold.
According to Luis Alberto Romero Cano, a researcher with the University of Granada’s Carbon Materials Research Team, “The results show a great potential for the use of said materials as adsorbents capable of competing with commercial activated carbon for the adsorption and recovery of metals present in wastewater, in a way that it could be possible to carry out sustainable processes in which products with a great commercial value could be obtained from food industry residues.”