Elimination of toxic mercury from contaminated water

Water contaminated with mercury and other toxic heavy metals is a major cause of environmental damage and health problems in the world. Researchers at the Chalmers University of Technology in Sweden are now presenting a completely new way of cleaning contaminated water with an electrochemical process. The results are published in the scientific journal Nature Communications.

"Our results really exceeded the expectations we had when we started using this technique," says Björn Wickman, Chalmers Physics Research Manager. "Our new method can reduce the mercury content in a liquid by more than 99 %.This can bring water into the margins of safe human consumption."

According to the World Health Organization (WHO), mercury is one of the most harmful substances for human health. This can influence the nervous system, brain development, etc. It is particularly harmful to children and can also be passed from mother to child during pregnancy. In addition, mercury spreads very easily in nature and can enter the food chain. Freshwater fish, for example, often contain high levels of mercury.

Over the past two years, Björn Wickman and Cristian Tunsu, a researcher in the Chalmers Department of Chemistry and Chemical Engineering, have been studying an electrochemical process for cleaning mercury from water. Their method involves extracting heavy metal ions from the water by encouraging them to form an alloy with another metal.

"Today, eliminating the large quantities of mercury water contained in large quantities of water is a major challenge." Industries need better methods to reduce the risk of mercury release into the water. nature, "says Björn Wickman.

Their new method involves a metal plate – an electrode – that binds specific heavy metals to it. The electrode is made of platinum, a noble metal, and by an electrochemical process, it extracts the toxic mercury from the water to form an alloy of the two. In this way, the water is cleaned of mercury contamination. Since the alloy formed by the two metals is very stable, the mercury is unlikely to re-enter the water.

"An alloy of this type has already been manufactured, but for a totally different purpose – it is the first time that the electrochemical alloy technique is used for decontamination purposes," says Cristian Tunsu.

One of the strengths of the new cleaning technique lies in the fact that the electrode has a very large capacity. Each platinum atom can bind to four atoms of mercury. In addition, mercury atoms do not just bind to the surface, but penetrate deeper into the material, creating thick layers. This means that the electrode can be used for a long time. After use, it can be emptied in a controlled manner. Thus, the electrode can be recycled and the mercury safely eliminated. Another advantage of this process is that it is very energy efficient.

"Another great thing with our technique is that it's very selective – even though there can be many types of substances in the water, it just eliminates mercury." The electrode does not waste capacity by unnecessarily removing other substances from the water, "says Björn Wickman.

We are trying to patent the new method and, to commercialize the discovery, the new company Atium was created. The new innovation has already been rewarded with numerous awards and awards in Sweden and abroad. The research and colleagues at the company also sparked a strong reaction from the industry.

"We have already had positive interactions with a number of interested parties who want to test the method, and we are currently working on a prototype that can be tested outside the lab under real-life conditions."

Potential uses of the new method

This technique could be used to reduce the amount of waste and increase the purity of these waters and process water in the chemical and mining industries and in the production of metals. This can contribute to better environmental cleaning of places with contaminated soil and water sources.

It can even be used to clean drinking water in severely affected environments because, thanks to its low energy consumption, it can be powered entirely by solar cells. Therefore, it can be developed into a mobile water purification technology and reusable.

More about heavy metals in our environment

Heavy metals in water sources create enormous environmental problems and affect the health of millions of people around the world. Heavy metals are toxic to all living organisms in the food chain. According to the WHO, mercury is one of the most dangerous substances for human health. It influences the nervous system, brain development, etc. The substance is particularly dangerous for children and unborn babies.

Today, there is strict regulation regarding the management of toxic heavy metals in order to prevent their spread in the wild. But many places in the world are already contaminated and can be transported in the rain or in the air. This results in certain environments in which heavy metals can become abundant, for example fish in fresh water.

In industries where heavy metals are used, better methods of recycling, cleaning and decontaminating the affected water are needed.

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More information:
Cristian Tunsu et al, Efficient removal of mercury from aqueous currents by the formation of electrochemical alloys on platinum, Nature Communications (2018). DOI: 10.1038 / s41467-018-07300-z