It’s estimated that the world yields 110 million tons of citrus fruits annually, with oranges accounting for more than half of that production volume. Given that not every part of the fruit is put to use, that’s a lot of waste.
But researchers at Flinders University in Adelaide, Australia, have made a breakthrough that will allow humans to use citrus waste to suck the highly poisonous metal mercury out of land and sea.
Justin Chalker, a lecturer in synthetic chemistry at Flinders, created a new polymer—described as a “dark red material”—that turns yellow when mercury is detected and removes it from the areas it has contaminated. To produce the polymer, Chalker and his team combined citrus waste with industrial sulfur waste.
Around 70 thousand tons of limonene waste is produced by the citrus industry each year. Over 70 million tons of sulfur is produced annually by the petroleum industry. It lies unused, as Chalker has pointed out, in mountainous piles around the globe. He noted that the abundance of sulfur and limonene waste will make the polymer cheap to produce on a scale large enough to handle major environmental cleanups or to coat domestic and waste water.
Researchers Max Worthington and Justin Chalker. Image via Flinders University
“So not only is this new polymer good for solving the problem of mercury pollution, but it also has the added environmental bonus of putting this waste material to good use while converting them into a form that is much easier to store so that once the material is ‘full’ it can easily be removed and replaced,” Chalker said.
Mercury plagues many parts of the globe, seeping into land and impacting food and water supplies, contaminating marine life that then find their way into humans’ food supply. It’s produced in a variety of human activities, from mining to the burning of fossil fuels. Mercury levels in the oceans have tripled since the Industrial Revolution, and the metallic element has been linked to health problems in humans and animals, affecting reproductive health and IQ.
Chalker’s research will be published in an open-access article in the journal Angewandte Chemie International Edition.