Sorting the wheat from the chaff: Poster prize for research into flotation

News item from 15th December 2017

Labor für Flotation

Flotation lab. Foto: HZDR/ Frank Schinski


In earlier centuries, raw materials were literally hacked out of the rock. The process is vividly described in the miners’ anthem, the Steigerlied. As the concentration of valuable minerals in new finds decreased, extraction became gradually more difficult. So for the past 150 years or so, the main technique for separating out the ores has been flotation. But now, even this process is being pushed to its limits, because the valuable ore particles are smaller today than the width of a human hair (<50 microns). These ultrafine particles are the subject of research in the Processing Department at HIF.

For the scientists working there, the key question is how the tiniest quantities of ore can be separated out from unusable rock by flotation. Their investigations into the process are being performed at the molecular level. One factor that has been poorly understood so far is the behaviour of so-called ‘gangue’, i.e. the bulk material without any value. Doctoral student Edgar Schach and former HIF researcher Tom Leistner presented their findings in the format of a poster at the Flotation ‘17 conference held last November in South Africa. The judges were so impressed with their contribution they awarded them the Fundamentals Symposium Award.

The experiments so far suggest that the size of the gangue minerals also plays a role in the process. It is planned to take the research further.


T. Leistner et al.: How gangue particle size can affect the recovery of ultrafine and fine particles during froth flotation, Minerals Engineering, 101 (2017) 1-9.


Dr Martin Rudolph