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Electrochemical Controlling Domains for
Platinum Group Minerals
Margreth Tadie
Stellenbosch University, South Africa
Jenni Sweet
South Africa
ABSTRACT: Froth flotation as a process has revolutionized platinum group mineral (PGM) beneficiation.
Recovery of these PGMs applies the fundamental philosophy used for sulfide mineral flotation which is
mechanistically underpinned by charge transfer processes. Electrochemical interactions occur between
conducting and semi-conducting minerals resulting in a hydrophobic mineral surface being produced. Owing
to the more metallic character of PGMs the mineral surface can enhance these electron exchanges in a catalytic
effect. In order for the flotation chemistry system surrounding the mineral to support the achievement of
hydrophobicity, energetic differences between species donating electrons (collectors) and those accepting
electrons (dissolved oxygen) need to exist in such a way that successful transfer takes place through the mineral
surface. Electrochemical potential can be used as a proxy to establish whether these oxidation (donor), and
reduction (acceptor) reactions would be favorable within an aqueous system. Domains for flotation using the
Pourbaix diagram as a tool have been reported for sulfide minerals in the literature. This study establishes
Eh-pH domains using electrochemistry, hydrophobicity and flotation ranges for telluride PGMs compared to
sulfides and arsenides. These flotation chemistry domains should be considered alongside optimal operational
parameters, and particle size is noted to be a crucial variable. These findings offer valuable guidance for optimizing
reagent chemistry in PGM production.
Keywords: Platinum group minerals, thiol collectors, donors, acceptors, Pourbaix diagrams, flotation domains
INTRODUCTION
Froth flotation chemistry has long been a key fundamen-
tal sub-process for the success of mineral flotation. The
objective is the ultimate achievement of sufficient hydro-
phobicity on the mineral surface to enable successful par-
ticle bubble attachment. Whilst natural hydrophobicity is
to some degree present in some of the minerals concen-
trated using this process (for example sulfide minerals) the
most efficient way to achieve hydrophobicity is through
the use of collector molecules. Such molecules are specifi-
cally designed to selectively attach to mineral surfaces and
create a hydrophobic cover that is attractive to air bubbles
and enables collection within the pulp zone. Traditionally
in the case of sulfide minerals these collector molecules
are anionic with the most traditional and successful class
being the thiol or xanthate group of collectors. To date
the chemistry of collectors has expanded to cover multi-
ple chemical species including amines, dithiophosphates,
Electrochemical Controlling Domains for
Platinum Group Minerals
Margreth Tadie
Stellenbosch University, South Africa
Jenni Sweet
South Africa
ABSTRACT: Froth flotation as a process has revolutionized platinum group mineral (PGM) beneficiation.
Recovery of these PGMs applies the fundamental philosophy used for sulfide mineral flotation which is
mechanistically underpinned by charge transfer processes. Electrochemical interactions occur between
conducting and semi-conducting minerals resulting in a hydrophobic mineral surface being produced. Owing
to the more metallic character of PGMs the mineral surface can enhance these electron exchanges in a catalytic
effect. In order for the flotation chemistry system surrounding the mineral to support the achievement of
hydrophobicity, energetic differences between species donating electrons (collectors) and those accepting
electrons (dissolved oxygen) need to exist in such a way that successful transfer takes place through the mineral
surface. Electrochemical potential can be used as a proxy to establish whether these oxidation (donor), and
reduction (acceptor) reactions would be favorable within an aqueous system. Domains for flotation using the
Pourbaix diagram as a tool have been reported for sulfide minerals in the literature. This study establishes
Eh-pH domains using electrochemistry, hydrophobicity and flotation ranges for telluride PGMs compared to
sulfides and arsenides. These flotation chemistry domains should be considered alongside optimal operational
parameters, and particle size is noted to be a crucial variable. These findings offer valuable guidance for optimizing
reagent chemistry in PGM production.
Keywords: Platinum group minerals, thiol collectors, donors, acceptors, Pourbaix diagrams, flotation domains
INTRODUCTION
Froth flotation chemistry has long been a key fundamen-
tal sub-process for the success of mineral flotation. The
objective is the ultimate achievement of sufficient hydro-
phobicity on the mineral surface to enable successful par-
ticle bubble attachment. Whilst natural hydrophobicity is
to some degree present in some of the minerals concen-
trated using this process (for example sulfide minerals) the
most efficient way to achieve hydrophobicity is through
the use of collector molecules. Such molecules are specifi-
cally designed to selectively attach to mineral surfaces and
create a hydrophobic cover that is attractive to air bubbles
and enables collection within the pulp zone. Traditionally
in the case of sulfide minerals these collector molecules
are anionic with the most traditional and successful class
being the thiol or xanthate group of collectors. To date
the chemistry of collectors has expanded to cover multi-
ple chemical species including amines, dithiophosphates,