Sweden: Researchers at Sweden’s Chalmers University of Technology have developed a method capable of reducing mercury levels in sulphuric acid by more than 90 percent, even at low concentrations.

Sulphuric acid is a vital chemical compound widely used across various industries, including paper manufacturing, pharmaceuticals, cosmetics, batteries, detergents, and fertilizers. Unfortunately, one of the most hazardous substances on Earth, mercury, often contaminates sulphuric acid. The new study gives hope to the global challenge.

“Until now, there has been no viable method for purifying finished sulphuric acid at all. With such a radical reduction in the mercury content, we come well below the current limit values. Such pure high quality sulphuric acid is in high demand in industrial applications and an important step in reducing environmental impact,” remarked research leader Mr. Björn Wickman, Associate Professor at the Department of Physics at Chalmers.

Mercury as a Global Challenge

Mercury, a highly toxic heavy metal, poses significant risks to the environment and all life forms. It can be released into the atmosphere and subsequently deposited into water bodies through rainfall. This toxic substance accumulates in the soil, water, and living organisms, leading to adverse effects throughout the food chain. It is known to impair the central nervous system and brain development in both humans and animals.

According to a report from the United Nations Environment Programme (UNEP), human activities, such as cement manufacturing, small-scale gold mining, coal burning, and metal production, contributed to a 20 percent increase in mercury emissions to the atmosphere between 2010 and 2015. In the same year, approximately 2,200 tonnes of mercury were released into the air, while an estimated 1,800 tonnes ended up in soil and water. Over the past century, atmospheric mercury concentrations may have surged by as much as 450 percent.

Mr. Björn Wickman emphasizes the importance of reducing mercury emissions, as emitted mercury persists in the environment, posing health risks for thousands of years.

Mercury reducing from sulphuric acid

Five years ago, the Chalmers research team pioneered a method for removing mercury from water using electrochemical processes. This technique involved a metal electrode that absorbed the toxic metal, forming an alloy, and allowing for safe removal and subsequent electrode regeneration. Building upon this achievement, the researchers have now demonstrated the successful removal of mercury from concentrated sulphuric acid.

Collaborating with the mining and metals refining company Boliden and the spin-off company Atium, the researchers performed experiments with sulphuric acid. They hope to advance their findings by developing a reactor system through which sulphuric acid can flow, enabling simultaneous purification. The team aims to create a pilot-scale process that aligns with real-world production volumes.

Presently, mercury removal primarily occurs during earlier stages, where it is eliminated from smelter concentrates and recycled streams before sulphuric acid production. However, this existing process leaves trace amounts of mercury in the final products.

Non-toxic products ahead

Purifying sulphuric acid not only prevents additional mercury emissions but also enables cost-effective industrial operations while producing a high-purity, non-toxic product. The researchers’ novel method has achieved mercury levels as low as 0.02 milligrams per kilogram of sulphuric acid in their pilot study, surpassing the threshold for high purity (0.08 milligrams per kilogram) and acceptable quality (0.30 milligrams per kilogram) of sulphuric acid. By significantly reducing mercury content, the value of sulphuric acid is enhanced.

The researchers hope that their innovative sulphuric acid purification method will prompt the global tightening of legislation concerning mercury limits. Existing limit values are based on current technology, but with this new approach, the researchers aim to encourage more stringent regulations, considering the widespread presence of higher mercury levels worldwide.

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