2402
Fundamental and Applied Aspects of Alkoxycarbonyl Alkyl
Dithiocarbamate Interactions with Sulfides and Precious Metals
N. Bellusci, D.R. Nagaraj, R.S. Farinato, P. Patra, B. Vaziri
Department of Earth and Environmental Engineering, Columbia University, New York, NY, USA
T. Bhambhani, and E. Arinaitwe
Syensqo Technology Solutions, Stamford, CT, USA
ABSTRACT: Alkoxycarbonyl alkyl dithiocarbamates (ACADTCs) represent a class of ligands with unusual
coordination chemistry and interfacial properties. Under appropriate process conditions, they can be used for:
a) selective separations of mineral/metal values from gangue iron sulfides, b) bulk sulfide flotation when all the
sulfides possess value, and c) flotation of pyrite and other iron sulfides to produce benign tailings. Via the soft S
donor and the buttressing O donor in their structure, they can form strong complexes with soft acids (especially
Cu, Au, Ag, and platinum group elements). There is currently no published literature that describes the behavior
of these molecules in the context of acid-base interactions, while linking these to their flotation performance in
real ore systems. Such bridging of the theoretical and practical aspects is necessary to advance the understanding
and use of these ligands for addressing increasingly complex ores.
In this paper, we introduce scientific insights into the interactions of the ACADTCs with sulfides and precious
metals. Voltammetric, spectroscopic, and wettability studies were used to probe the molecular level processes of
these ligands, and the results are emphasized in the context of Lewis acid-base concepts and Pearson’s hard and
soft acid-base principle. Several examples of flotation practice with the ACADTCs in sulfide and precious metal
ore systems are also provided to highlight their unique attributes.
INTRODUCTION
Alkoxycarbonyl alkyl dithiocarbamates (ACADTCs) are
novel ligands that have found prominent use in sulfide and
precious metal flotation. They have been demonstrated to
be very effective collectors for recovering base and precious
metal values from Cu, Cu-Mo-Au, Cu-Ni, polymetal-
lic (Pb-Zn-Ag), primary Au, and platinum group mineral
(PGM) ores. These functionalized dithiocarbamates are
unique in their ability to enhance performance in highly
selective to rather non-selective (bulk sulfide flotation) sep-
arations. In addition, they have found use in the recovery
of iron sulfides rejected from primary processes to produce
environmentally benign tailings.
The interactions of the ACADTCs and ligands in
general with minerals/metals can be explained in terms of
Lewis acid-base (LAB) concepts (Jensen, 1980). A Lewis
base is a chemical entity or ligand which donates electrons
a ligand can refer to a functional group comprising donor
atoms, the donor atoms themselves, or the entire molecule
containing the functional group. A Lewis acid is an atom
or grouping of such which accepts electrons (Nagaraj,
1988). In the context of mineral separations, Lewis bases
are ligands/donor atoms which donate electrons to metals/
acceptor sites (Lewis acids) on an ore/mineral particle sur-
face (Nagaraj &Ravishankar, 2007). These donor-acceptor
interactions result in the formation of a complex the type of
Fundamental and Applied Aspects of Alkoxycarbonyl Alkyl
Dithiocarbamate Interactions with Sulfides and Precious Metals
N. Bellusci, D.R. Nagaraj, R.S. Farinato, P. Patra, B. Vaziri
Department of Earth and Environmental Engineering, Columbia University, New York, NY, USA
T. Bhambhani, and E. Arinaitwe
Syensqo Technology Solutions, Stamford, CT, USA
ABSTRACT: Alkoxycarbonyl alkyl dithiocarbamates (ACADTCs) represent a class of ligands with unusual
coordination chemistry and interfacial properties. Under appropriate process conditions, they can be used for:
a) selective separations of mineral/metal values from gangue iron sulfides, b) bulk sulfide flotation when all the
sulfides possess value, and c) flotation of pyrite and other iron sulfides to produce benign tailings. Via the soft S
donor and the buttressing O donor in their structure, they can form strong complexes with soft acids (especially
Cu, Au, Ag, and platinum group elements). There is currently no published literature that describes the behavior
of these molecules in the context of acid-base interactions, while linking these to their flotation performance in
real ore systems. Such bridging of the theoretical and practical aspects is necessary to advance the understanding
and use of these ligands for addressing increasingly complex ores.
In this paper, we introduce scientific insights into the interactions of the ACADTCs with sulfides and precious
metals. Voltammetric, spectroscopic, and wettability studies were used to probe the molecular level processes of
these ligands, and the results are emphasized in the context of Lewis acid-base concepts and Pearson’s hard and
soft acid-base principle. Several examples of flotation practice with the ACADTCs in sulfide and precious metal
ore systems are also provided to highlight their unique attributes.
INTRODUCTION
Alkoxycarbonyl alkyl dithiocarbamates (ACADTCs) are
novel ligands that have found prominent use in sulfide and
precious metal flotation. They have been demonstrated to
be very effective collectors for recovering base and precious
metal values from Cu, Cu-Mo-Au, Cu-Ni, polymetal-
lic (Pb-Zn-Ag), primary Au, and platinum group mineral
(PGM) ores. These functionalized dithiocarbamates are
unique in their ability to enhance performance in highly
selective to rather non-selective (bulk sulfide flotation) sep-
arations. In addition, they have found use in the recovery
of iron sulfides rejected from primary processes to produce
environmentally benign tailings.
The interactions of the ACADTCs and ligands in
general with minerals/metals can be explained in terms of
Lewis acid-base (LAB) concepts (Jensen, 1980). A Lewis
base is a chemical entity or ligand which donates electrons
a ligand can refer to a functional group comprising donor
atoms, the donor atoms themselves, or the entire molecule
containing the functional group. A Lewis acid is an atom
or grouping of such which accepts electrons (Nagaraj,
1988). In the context of mineral separations, Lewis bases
are ligands/donor atoms which donate electrons to metals/
acceptor sites (Lewis acids) on an ore/mineral particle sur-
face (Nagaraj &Ravishankar, 2007). These donor-acceptor
interactions result in the formation of a complex the type of