Scientists Create Coating for Mercury Sorption
Scientists from Flinders University in Australia recently modelled a polysulfide coating made from waste products that has shown to absorb mercury and other metal contaminants in water.
According to the university’s release, mercury pollution is a global problem in water, air and soil near goldmines, cement and other heavy industries burning fossil fuels. This removal can be too expensive or difficult in some of the world’s poorest countries.
To remedy this, Flinders researchers tested a sustainable extraction material capable of absorbing almost all mercury in polluted water in minutes. The coated material is reportedly made from low-cost waste from petroleum, citrus and agricultural production.
“It is clear from the study that this mercury-binding material, invented at Flinders University, is ultra-fast in its ability to remove mercury from water. In some cases, more than 99% of the mercury is captured in just a few minutes,” said senior author and professor Justin Chalker
Chalker Lab co-author Dr. Max Worthington added that the testing was done on a new material created by coating silica with sulfur and limonene. These together reportedly create a novel chemical combination already shown to effectively absorb waste mercury.
“This silica covered with an ultra-thin coating of poly(S-r-limonene), using sulfur left over in petroleum production and orange oil from orange peel discarded by the citrus industry, was extensively tested in various pH and salt concentrations,” Worthington said.
“Not only is this new mercury sorbent able to rapidly bind to mercury in water, but is also selective in taking up mercury but not other metal contaminants such as iron, copper, cadmium, lead, zinc and aluminium.”
The silica is a free-flowing orange powder, which will help with safety after capturing the inorganic mercury due. According to researchers, 300 grams can be produced in a single batch.
“The particles contained in just 27 grams of this free-flowing orange powder have an approximate surface area of a soccer field, and it can be quickly produced in large enough volumes to suit contamination levels,” said co-author Dr. Max Mann.
The silica coating is sourced from agricultural waste like wheat or rice production, providing sustainability. The mercury remediation technology can reportedly be a circular economy solution due to the material being created from waste.
The research team used mathematical modelling to qualitatively understand the rate of mercury uptake. The data was reportedly critical to measuring and optimizing the new sorbent in real-world remediation.
“This is an exciting new development in producing renewable and accessible solutions to major environmental issues facing the world today,” said applied mathematician Dr. Tony Miller, another co-author on the publication.
Chalker said that the project is an “excellent example of collaboration across chemical and physical sciences and mathematics to understand the rate of mercury uptake by our new and innovative sorbent.”
The study, “Modelling mercury sorption of a polysulfide coating made from sulfur and limonene,” was recently published in the journal Physical Chemistry Chemical Physics. The project was funded by the Australian Research Council.
Other Flinders Mercury Coatings
Earlier this year, researchers from Flinders University developed a smart coating for pipelines that can remove mercury from water while preventing corrosion and solvent damage. The coating can also reportedly prevent acid and water damage of concrete surfaces.
“Made easily from elemental sulfur and dicyclopentadiene (DCPD is a by-product of petroleum refining), this new coating is multi-functional which gives us wide scope to use it in a wide range of useful ways and for longer lasting industrial products and components,” said Mann, a Flinders University PhD candidate and lead author. “This exciting new area of research extends fundamental chemistry to several practical applications.”
“The method for making the coating is safer than methods previously used for related coatings. The team developed a lower temperature process that prevented runaway reactions,” added co-author University of Liverpool researcher Dr. Zhang.
According to the study, after a curing process at 140 C (284 F) and due to a reaction between the sulfur and DCPD, the material was rendered insoluble and resistant to acids and solvents. Researchers then coated silica gel with the soluble oligomer to test mercury removal from water.
100 milligrams of the coated silica were added to a solution of water and mercury, then agitated using an end-over-end mixer. This test was repeated, and the coating showed “highly effective” mercury absorption, with the uncured sample removing greater than 99% of mercury within two hours and the cured samples removing at least 92% of mercury in the same time.
To test the coating’s protection from corrosion and solvents, the team applied the coating technique to metal, concrete and polyvinyl chloride. Additionally, the use was extended to cement and tests showed protection from both acid and water penetration.
The research team reports that the coating is repairable from scratches and other damage with heat application. This process can take place due to the coating’s chemical structure, allowing sulfur-sulfur bonds to be broken and reformed.