Home » Archive News In Brief » News in Brief 2022 » News in Brief Issue 05_2022 » Extracting important valuable substances from mine water: New project at the THGA’s Research Center of Post-Mining
Fig. 1. What valuable substances are in mine water? Bastian Reker from the Research Center of Post-Mining is investigating the potential of new treatment technologies in the IAW33 project. Photo: THGA/Volker Wiciok

Extracting important valuable substances from mine water: New project at the THGA’s Research Center of Post-Mining

Resources are becoming scarcer, energy prices are rising. In addition, dependence on third countries has led to a global rethink when it comes to extracting raw materials. New ways must be found to extract valuable materials ecologically and economically. That these ways also follow unusual ideas is shown by a new project that has now started at the Research Center of Post-Mining (FZN) at the TH Georg Agricola University (THGA), Bochum/Germany: Over the next two years, the scientists in the “IAW33” project will investigate whether strategic raw materials can still be extracted from mine water and which methods are best suited for this. With the help of new processing technologies, critical metals in particular are to be extracted. The experts not only look at the mine water itself, but also examine its precipitation products and treatment residues. They conduct their investigations at various mines in the Ruhr, Saar and Ibbenbüren regions.

The research project is initially funded by the RAG-Stiftung, Essen/Germany, until 2024. The full project title is: Innovative processing technologies and their potential for recovering valuable materials from mine water, precipitation products and processing residues at Ruhr, Saar and Ibbenbüren with special consideration of critical metal resources, in short: IAW33.

“For us, post-mining does not only mean dealing with the challenges that the coal industry has left us. In the field of post-mining, it is also a matter of developing new possibilities and opportunities in the former coalfields,” says Bärbel Bergerhoff-Wodopia, Member of the Board of Executives of the RAG-Stiftung. “The new research project around the extraction of strategic raw materials from mine water is a highly exciting field of the future that is geared towards sustainability. It can contribute to reducing dependencies in raw material extraction. Just how important independence can be in this field is particularly evident to us these days. That is why we as the RAG-Stiftung are very happy to support this special project.”

“We see mine water as a potential stream of valuable materials,” says Prof. Christian Melchers, who heads the project at FZN. “The innovative thing about our idea is that we not only look at the mine water itself, but also examine the residues from treatment and its precipitation products. Precipitation refers to the separation of a dissolved substance from a solution.” What is sludge and silt for the layman is a real treasure trove for the experts at the FZN: “Recent investigations have shown that it contains, e. g., magnesium, which is used in engine construction. In the past, there have already been supply bottlenecks with the Chinese market leader. At best, we want to counteract these dependencies,” explains project member Bastian Reker (Figure 1). Rare earths, which can drive the expansion of renewable energies, or lithium, which is crucial for e-mobility, are also found.

The scientists are also examining the quantities of the critical element germanium in the mine water. “This is a by-product that is otherwise only produced during zinc extraction and is essential for the coating of fibre optic cables and thus for the expansion of the network,” says Reker. “Currently, all of these raw materials are being extracted worldwide under sometimes dubious environmental standards that affect people and the environment equally,” adds Prof. Melchers. “This simply no longer fits in with the spirit of the times and the growing ecological awareness in our society. We therefore want to initiate a rethink, accompany the processes scientifically and thus look for new possibilities on our own doorstep.”

The mine waters that are lifted from great depths with pumps in the former coalfields of the Ruhr, Saar and Ibbenbüren show a wide range of different mineralisations and enrichments – depending on the regional geology, hydrogeology and other influencing factors left behind by mining, explains expert Prof. Melchers: “We are now examining the extent to which it is also economically worthwhile to collect and process these valuable substances.”

To this end, the scientists will be setting up their own precipitation reactors at suitable locations in the coming months. In them, iron and other metals will be separated in a targeted manner by adding oxygen. They want to transfer the knowledge they gain from designing the plants on a laboratory scale to experimental plants on a large scale. In the IAW33 project, the scientific team is also testing completely new processing technologies. Hyperspectral sensors, e. g., could help to directly detect the critical metals in mine water and co. and assess their mineralogical composition in a matter of seconds. The most promising methods are to be further developed at the FZN. (THGA/Si.)