APPLICATIONS OF THE ATOMIC FORCE MICROSCOPE IN FLOTATION RESEARCH
Bent Babel, Martin Rudolph
Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz-Institute Freiberg for Resource Technology,
Halsbrücker Straße 34, 09599 Freiberg, Germany, tel.: +49 351 260 4410, mail: b.babel@hzdr.de
ABSTRACT
This abstract gives an overview of the applications of the Atomic Force Microscope (AFM) in flotation
research. The AFM, which has a broad application in different disciplines, is a versatile tool to measure
surface properties and particle-particle interactions. In the field of mineral processing the AFM can be
utilized to gather information of mineral surfaces such as the surface roughness or particle-particle
interactions related to separation processes like magnetic separation, triboelectric separation and flotation.
In the context of flotation it is possible to measure the hydrophobic interaction between a colloidal probe
(CP-AFM) and the mineral surface. One drawback of this technique is the missing link between the
hydrophobicity and the chemical composition of the mineral surface, respectively the adsorbed layers. This
limitation can be exceeded by the combined utilization of the AFM and Raman Spectroscopy named TipEnhanced Raman Spectroscopy (TERS). This surface sensitive technique enables the chemical analysis of
thin films with nanometer resolution by the utilization of a plasmonic effect that occurs at the surfaces of
noble metal nanoparticles. The aim is the detection of adsorbed flotation reagents on mineral surfaces. The
combination of TERS and CP-AFM measurements enables the investigation of the adsorption of flotation
reagents on mineral surfaces and their effect on hydrophobicity.
As outlined the application of the AFM in mineral processing can give a deeper understanding of occurring
micro processes and thereby a better physical and chemical description of macro processes. Especially
TERS offers a better understanding of the adsorption of flotation reagents.
The paper presents fundamental investigations of CP-AFM and TERS on actual mineral specimens (quartz,
cassiterite, apatite, calcite, scheelite) which are prepared to achieve a surface roughness of less than 10 nm.
The impact of collector and depressant adsorption on the measurement, i.e. hydrophobic interactions with
CP-AFM and vibrational spectroscopy with TERS is shown.
KEYWORDS
atomic force microscope, tip-enhanced Raman spectroscopy, flotation