Recovery of valuable elements from tailings dumps accompanied by environmental remediation – the pilot plant project “ReMiningPlus”

Flotation tailings from a former lead-zinc mine near Freiberg (Germany) consist of fine-grained quartz, feldspar, mica and the sulfide minerals pyrite, galena and sphalerite, which are not recovered by flotation. Sphalerite contains significant amounts of indium (up to 0.38 % (w/w)) in addition to iron, copper and cadmium, resulting in assumed average indium content of 30 mg/kg in the tailings. The presentation shows the development of biohydrometallurgical recovery of indium from laboratory to pilot scale. In a 2 m³ bioreactor, maximum zinc and indium leaching rates of 80 % were obtained at a pulp density of 25%. For the recovery of indium from the PLS (pregnant leaching solution), a stepwise precipitation process is being developed consisting of a combined iron/indium precipitation and a subsequent treatment of the indium precipitate product. A new project has been started in which a modular plant for the utilization of valuable materials from these sulfide tailings and their environmentally friendly remediation is being set up directly at the tailings site. Combining resource technology to utilize valuable elements (indium and zinc) from tailings and environmental technology to eliminate harmful substances (arsenic and cadmium) with the use of inert components (e.g. as building material) represents a win-win situation. After its completion, the modular plant consists of three parts: the leaching, the recyclables and the environmental modules. Results and findings of the project will be processed for environmental education in schools and used for the development of a web application (app) that can be used to content for integration into existing tourism concepts. Through the implementation of the aforementioned goals, the project provides a decisive contribution to the structural change in the region, as it a concept for linking rehabilitation and secondary raw material extraction and a possible economic and touristic reuse.