An electrochemical process engineered at Chalmers University of Technology, Sweden, for removing mercury Mercury ions (light purple) in a liquid come are attracted to the platinum electrode’s surface and are reduced to metallic mercury. On the electrode, mercury atoms (dark purple) and platinum atoms (grey) develop into a strong alloy, and the mercury is thus removed from the water. Source: Björn Wickman and Adam Arvidsson, Chalmers University of Technologyfrom water reduces concentrations of the hazardous metal in liquid by more than 99%. Their method extracts mercury metal ions as they form an alloy with another metal.

A platinum electrode draws mercury from water, binding with it and transforming into an alloy of the two. The stable alloy poses no risk for releasing the mercury back into aquatic systems. Each platinum atom in the high-capacity, mercury-selective electrode can bond with four mercury atoms, which do not only adhere to the surface but penetrate into the material to create thick layers.

The alloying process is not affected by pH, and it is possible to remove mercury well below the limits allowed in drinking water. The system is also efficient in the presence of other cations and anions in the solution, as well as reversible. Increasing the surface area using platinum nanoparticles shortened the time required for retrieval, and a decontamination efficiency above 99.4% was achieved for a solution containing 10 mg L−1 mercury.

The technique could be applied to reduce the amount of waste and increase the purity of waste and process water in the chemical and mining industries, and in metal production. Solar cells can power the low-energy process to clean drinking water in degraded environments.

The research is published in Nature Communications.