Decontamination of Mercury from Aqueous Systems via Electrochemical PtHg4 Alloy Formation

Licentiate thesis, 2023

Mercury is worldwide a severe heavy metal pollutant and a serious threat to human health and ecosystems. Mercury can be released into the environment by various natural processes; however, mercury pollution has been significantly amplified by human activities such as mining, production of fertilizers, waste incineration and disposal. Once mercury enters aquatic ecosystems, it bioaccumulates and biomagnifies, and mercury can travel vast distances in water, resulting in widespread contamination and devastation. It is thus crucial for the well-being of humans and ecosystems to address the mercury contamination of water. It is important not only to reduce the mercury pollution at its source, but also reduce the present contamination of water. Current technologies used to mitigate the situation are far from optimal and the development of more efficient and effective removal methods are needed. A novel method based on electrochemical alloy formation between mercury ions in solution and a platinum surface has been shown to offer various advantages over previous techniques. The method can be used to decontaminate both waste and natural waters, as well as highly corrosive acids generated from mining industries.

In this thesis, the fundamental principles of electrochemical PtHg4 alloy formation for mercury removal are studied. The reaction mechanisms and energetics are examined, and its potential for future large-scale applications in industries is explored. It is shown that mercury can be efficiently removed from industrial concentrated sulfuric acid derived from zinc smelting. Comparison between laboratory-scale and a medium-scale demonstrator show excellent scalability of the removal method. Additionally, mercury is efficiently removed from diluted acids with initial mercury concentrations as low as 0.25 µg/L, making the method applicable for both environmental and industrial settings. This thesis establishes an important foundation for further research and optimization of electrochemical alloy formation as a mercury removal method. With continued development and advancements, the method has the potential to contribute significantly to the mitigation of global mercury pollution for the protection of human health and ecosystems.