Scientists from Chalmers University of Technology, Sweden have presented new research in ways to clean water contaminated with mercury using electrochemical processes. Water polluted by heavy metals such as mercury is the cause of major health problems around the globe.
Mercury is one of the most harmful pollutants to humans, according to the World Health Organisation (WHO). The metal can impede brain development and also have an impact on the health of the nervous system.
Mercury deadly to small children
It is particularly dangerous to children and can even be transferred to unborn babies via their mothers. Mercury easily enters the food chain and can be passed onto humans via other animals.
Freshwater fish are particularly notorious as carriers of the metal. Cleaning mercury is a very challenging process.
Current methods costly and difficult
Over the last two years Björn Wickman and Cristian Tunsu, a researcher at the Department of Chemistry and Chemical Engineering at Chalmers, have studied how to apply electrochemical processes for cleaning mercury from water. Their method involves extracting the heavy metal ions from water by encouraging them to form an alloy with another metal.
“Today, removing low, yet harmful, levels of mercury from large amounts of water is a major challenge. Industries need better methods to reduce the risk of mercury being released in nature,” says Björn Wickman.
Chalmers scientists surprised by an early success
“Our results have really exceeded the expectations we had when we started with the technique,” says the research leader Björn Wickman, from Chalmers’ Department of Physics. “Our new method makes it possible to reduce the mercury content in a liquid by more than 99%.
This can bring the water well within the margins for safe human consumption.” The new method works by using a metal plate, acting as an electrode, that binds heavy metals to it.
Cost effective method won't let mercury re-enter water body
The plate is made of the noble metal platinum, it draws the toxic mercury out of the water through an electrochemical process which binds to it and forms an alloy of the two. This relatively simple cycle cleans the water of its toxic mercury.
The alloy that is formed when the metal plate and the mercury bond is very stable and the mercury is unable to re-enter the water. “An alloy of this type has been made before, but with a totally different purpose in mind.
Breakthrough research has commercial applications
This is the first time the technique with electrochemical alloying has been used for decontamination purposes,” says Cristian Tunsu. The mercury atoms not only bond with the platinum's surface they can penetrate deeper creating thick layers which means the electrode can be used for a long time before needing to be replaced.
Once it has reached its capacity it can be disposed of in a controlled manner. “Another great thing with our technique is that it is very selective. Even though there may be many different types of substance in the water, it just removes the mercury.
Therefore, the electrode doesn’t waste capacity by unnecessarily taking away harmless substances from the water,” explains Björn Wickman. The scientists are attempting to patent the method in order to commercialize the idea.
“We have already had positive interactions with a number of interested parties, who are keen to test the method. Right now, we are working on a prototype which can be tested outside the lab under real-world conditions.”
The full research can be read in the article, “Effective removal of mercury from aqueous streams via electrochemical alloy formation on platinum” in Nature Communications.