New ways to utilize industrial side streams in water purification materials
The research was carried out partly in the laboratory and partly at the closed Hitura nickel mine located in Nivala. A pilot area was built in the mining area where the passive water purification method was tested in cooperation with several partners. This pilot project focused on cleaning mine leachate using blast furnace slag-based water purification adsorbents. According to research, the method effectively binds heavy metals such as nickel, iron and manganese, thus cleaning mine leachate.
Industrial side streams as a part of the solution
The key innovation of the research is to utilize industrial side-stream materials, such as blast furnace slag, metakaolin, mine tailings, tailings sand and zeolite, as water purification materials. These materials are used to make alkali-activated granules, i.e. adsorbents, which binds impurities from leachate in mining areas. The research used combinations of these different materials to make geopolymers, of which the blast furnace slag-based water purification material proved to be the most promising in laboratory tests. This material was also chosen as the main material for the pilot study in Nivala.
Adsorbents work in such a way that they bind harmful substances, such as heavy metals, to their surface, cleaning the water. With this treatment the water is allowed to be released back into the environment. This significantly reduces the need for water recycling and treatment, which can lead to large savings in industrial water treatment costs.
Important effects especially on the mining sector
"The amount of leachate in mining areas and other industrial areas is huge, and their efficient treatment is critical from an environmental point of view. If passive cleaning methods can be developed further, they can play a significant role in environmental protection. This research offers concrete solutions that allow industry to reduce its environmental footprint while potentially saving costs," says Dr. Johanna Laukkanen.
According to the research team, one of the special advantages of the method is the possibility to reuse the metals recovered from the leachate, which brings added value to the process. In the future, this can enable the reuse of metals and contribute to the realization of a circular economy.
The research conducted under the leadership of Johanna Laukkanen is part of a broader effort to develop more sustainable and environmentally friendly ways to manage industrial wastewaters and side streams. According to her, such passive water purification methods can be in part revolutionizing the water treatment processes, especially for industries that handle large volumes of water, such as the mining sector, where water treatment is particularly challenging and expensive.
Close to new environmentally friendly methods?
The research of Laukkanen and his colleagues opens doors to new types of applications in the utilization of industrial side streams. In the future, the solution can also be applied in other industrial sectors, where water purification and resource efficiency are key issues.
The results of the study show that mine leachate treatment can be carried out efficiently and environmentally friendly by using readily available side stream materials. This could significantly reduce the need for traditional water purification methods, which often require large amounts of energy and the use of chemicals.
Publication:
Alkali-activated materials containing mine tailings and zeolite for seepage water treatment in a closed nickel mine. Johanna Laukkanen, Hanna Runtti, Isabella Lan-cellotti, Tero Luukkonen, Cristina Leonelli ja Ulla Lassi. International Journal of Environmental Science and Technology 2024.
Photo: Ulla Nisonen
Other material:
Uusia ratkaisuja kaivostoiminnan ympäristöllisiin kysymyksiin. Suomen Kulttuurirahasto. (video, in Finnish)