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Orange Peels + Sulphur = Mercury Remediation?

Flinders University student Max Worthington and lecturer Dr. Justin Chalker with their mercury remediation material, sulphur-limonene polysulfide. | Image Credit: Ashton Claridge/Flinders University

Researchers from Australia’s Flinders University say they have found a “dirt cheap” solution to mercury contamination. Dr. Justin Chalker and his students have developed a dark red polymer from industrial waste products — sulphur and limonene — that turns bright yellow when it absorbs mercury. The color change allows the material to be a mercury detector on top of its remediation capabilities.

The polymer is called sulphur-limonene polysulfide and preliminary studies indicate it is non-toxic and safely stores the toxic metals it absorbs. Sulphur is a common waste product of the petroleum industry and limonene is found in the oil of orange peels and other citrus fruits. Since both are waste products, the new material is cheap enough to be produced for use in large-scale projects, such as environmental clean-ups or to coat wastewater pipes.

“More than 70 million tonnes of sulphur is produced each year by the petroleum industry, so there are literally mountains of it lying, unused, around the globe, while more than 70 thousand tons of limonene is produced each year by the citrus industry,” Dr. Chalker said. “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.”

Mercury contamination can occur as the result of industrial activities such as mining and burning fossil fuels. It is a neurotoxin that contaminates water and food supplies, which can cause reproductive issues and developmental delays in utero for humans and wildlife. With the concentration of mercury in the ocean increasing, a cheaper remediation solution is needed.

Sulphur-limonene polysulfide was found to remove 50 percent of the mercury from water after a single treatment, and subsequent treatments can be applied for further remediation. The early evidence of non-toxicity is promising – it may be possible to directly apply the polymer to natural ecosystems such as rivers, lakes and oceans.

The commercialization of Dr. Chalker says the commercialization of his work “may be a year or more away,” but the research team is actively pursuing partnership opportunities to bring the product to market and apply it to large-scale remediation efforts. Their goal is to use the material to remove mercury from groundwater and soil, and are also exploring the possibility of using it in water filters.

Hannah Furlong is an Editorial Assistant for Sustainable Brands, based in Canada. She is researching the circular economy as a Master's student in Sustainability Management at the University of Waterloo and holds a Bachelor's in Environment and Business Co-op. Hannah… [Read more about Hannah Furlong]

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