Mercury-removing polymer fights global health crisis

The University of Tulsa Department of Chemistry and Biochemistry has collaborated with international researchers to create a polymer that removes mercury from water and soil. The compound, sulfur-limonene polysulfide, is made entirely from industrial by-products sulfur and limonene and has the potential to address one of the most widespread and debilitating pollution problems on earth.

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A block of the sulfur-limonene polysulfide

The new polymer’s affinity for mercury is a game-changer for global health, especially in developing nations where artisanal mining occurs.

“Mercury pollution has led to a very serious health and environmental crisis,” said Justin Chalker, the project’s lead researcher and lecturer in synthetic chemistry at Flinders University in Adelaide, Australia. Chalker began the investigation as a chemistry faculty member at TU. “We hope our material can help ameliorate these conditions.”

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Mounds of sulfur from an oil refinery

A combination of the industrial by-products sulfur and limonene, the polymer is an efficient use of waste generated by the petroleum and citrus industries. Petroleum engineering facilities produce more than 70 million tons of sulfur each year, and the world’s citrus processors produce more than 70 million tons of limonene, which is found in orange peels. Nontoxic and inexpensive to make, Chalker said the polymer could support large-scale environmental cleanup efforts.

“This is a new benchmark in synthesizing useful materials from sustainable feedstocks,” Chalker said. “Many of the materials we rely on every day, such as plastics, coatings and medicines, are largely synthesized from nonrenewable petroleum resources.”

The remediation process involves mercury forming a strong bond to the polymer, which prevents the mercury from being washed away. For soil purification, the soil is washed with water, and the soluble mercury is removed after it adheres to the polymer. Chalker’s research team intends to use the polymer as a coating for pipes or water filters to remove mercury. For large-scale operations, polymer beds could be designed for mercury extraction.

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The sulfur-limonene polysulfide turns yellow upon exposure to solutions of this toxic salt.

The project’s contributions to waste valorization and environmental remediation would not have been possible without the presence of undergraduate research students at The University of Tulsa and Flinders University. As students in TU’s Tulsa Undergraduate Research Challenge program, alumnus Michael Crockett (BS ’15) and chemistry senior Austin Evans worked closely with Chalker for two years on the polymer’s development.

“Undergraduate research is a transformational experience in education,” Chalker said. “It’s typically the first time students have the freedom, resources and license to generate entirely new ideas and technologies.”

Evans said the knowledge and skills he gained throughout the project are invaluable to his future.

“Undergraduate research is truly unrivaled at TU, and it’s been exciting to be involved in such a significant discovery,” he said. “We are taking two substances with very limited uses and utilizing them to treat a serious pollution challenge.”

The research has been published in an open-access article in Angewandte Chemie International Edition, one of the highest profile journals in chemistry research. In addition to TU’s contributions, Flinders University honors student Max Worthington, the Centre for NanoScale Science and Technology at Flinders, the Institute of Molecular Medicine at the University of Lisbon and the University of Cambridge participated in the project.

Multiple patent applications have been filed, and TU is partnering with Flinders University to commercialize the technology for fieldwork.

View the published research at https://onlinelibrary.wiley.com/doi/10.1002/anie.201508708/abstract