Researchers from Freiberg extract materials for the future from waste materials

ZauBer project launched - project partner G.E.O.S. plans for a demonstration plant

Cleaning rivers and ditches and thereby extracting important raw materials for modern industry and economy is the goal of the new large-scale research project "rECOmine ZauBer". In the project, which is funded with about 1 million euros by the Federal Ministry of Education and Research, G.E.O.S., together with the TU Bergakademie Freiberg and three other regional companies, is researching new ecological and residue-free recycling technologies for mine waters and sludge in Saxony with promising approaches until the end of 2024.

Up to now, mining sludge and mine waters have been regarded almost only as wastes containing pollutants. Yet they still contain raw materials such as aluminium, iron or zinc. The partners in the joint project want to extract these materials and process the residues into sustainable materials for the future.

G.E.O.S. is mainly responsible for planning the pilot plant in the project. The scientists and engineers from Halsbrücke have been working on the ditch Roter Graben for many years, whether for water quality assessment or possible remediation. G.E.O.S. can now use this knowledge for the project's idea of recycling.



Purging instead of dredging and landfilling

The Red Ditch in the World Heritage region of the Ore Mountains/Krušnohoří was chosen as the study location. There, the researchers have to deal with a lot of ferruginous water and more than 13,000 tonnes of sludge. This comes from mine waters from the Freiberg mining area at the level of the river Freiberg Mulde and also from seepage water, e.g. from the old slag heap at the former mine Davidschacht. To avoid expensive and time-consuming excavation of the sludge deposits and subsequent disposal in landfills, it is pumped into a filter press and then dewatered. To do this, the water and sludge are passed through several membranes. The solid components are filtered out and, in a further step, the heavy metals are separated.


The result is clean water that can be returned to the original waters. Another product is the residual sludge, which the researchers process for valuable metals such as zinc or iron and filter out the last remaining pollutants such as cadmium or arsenic. The solid mineral residue is converted into so-called geopolymers, which are inorganic binders with properties that equal or even surpass cement. The final result is a stable concrete-like material.


Climate-friendly concrete or cement alternatives as a residual product

Working with geopolymers is not new - but their use in combination with mining slurries certainly is. With the amount of sludge currently estimated at 13,000 m³ in the Rote Graben in Saxony alone, the new approach offers promising potential for the development of an eco-efficient process. After all, the climate-friendly binder offers a CO2 savings potential of up to 80 percent compared to conventional concrete production. It is also more heat-stable, more resistant to chemicals and hardens faster than concrete.


Demonstration plant transfers laboratory scale to real world scale

So far, the trials are running on a laboratory scale. Next year, the developed technologies are to be transferred to the real scale with a new demonstration plant planned by G.E.O.S directly at the old mining ditch Roter Graben in Halsbrücke near Freiberg.

The tested processes may also be applied for the rehabilitation of old mines and water tunnels within the Ore Mountains. For an overview, the Freiberg scientists will create a special mine sludge cadastre for the first time. And even beyond the region, the newly developed recycling technologies from Freiberg offer possible solutions for the treatment of lignite mining areas, such as in Lusatia.


Creating social acceptance and attracting young talent

The project partners want to involve the communities in the active research and raise awareness about existing concerns about mining. To this end, exhibitions and events are planned with terra mineralia, as well as on-site tours and experiments at the Rote Graben.


Project partners

The project is coordinated by the TU Bergakademie Freiberg with the Institute for Technical Chemistry, the Institute for Thermal Process Engineering, Environmental and Natural Materials Process Engineering and terra mineralia. In addition, four regional companies are involved in the joint project: G.E.O.S., INTEC Gesellschaft für Injektionstechnik mbH & Co. KG, SAXONIA Site Development and Management Company mbH and Befesa Zinc Freiberg GmbH.



The project, which will run for just under three years (01.01.2022 - 30.11.2024), is being funded within the framework of the rECOmine alliance - RESOURCE-ORIENTED ENVIRONMENTAL TECHNOLOGIES FOR THE 21ST CENTURY, from the funding programme "WIR! - Change through Innovation in the Region with approximately 1 million euros from the Federal Ministry of Education and Research (funding code: 03WIR1908A).