3046
Surface Chemistry of Disodium Carboxymethyl Trithiocarbonate
(Orfom® D8) for Depressing Cu in Chalcopyrite-Molybdenite
Separation
Patrick Jeff Mensah, Trenin Bayless, Courtney Young
Metallurgical &Mineral Processing Engineering, Montana Technological University
Debbie Laney, Shawn Childress, Chad Brown
Chevron-Phillips Chemical
ABSTRACT: In traditional chalcopyrite-molybdenite (Cu-Mo) separation, NaSH and NaCN are the most
commonly used depressants however, these inorganic chemicals raise environmental, safety and economic
concerns. Hence, attention has shifted to organic depressants, particularly disodium carboxymethyl
trithiocarbonate (Orfom ® D8). For the past 8 years, Montana Tech investigators collaborated with Chevron-
Phillips Chemical Company to determine how this depressant works. Through a variety of techniques and
with ethyl xanthate as collector, they determined that, because it does not desorb the xanthate, it co-adsorbs
and thereby masks the xanthate hydrophobicity. This makes the chalcopyrite hydrophilic, thus causing it to
become depressed. In this study, a variety of different analytical techniques were explored to not only confirm
this mechanism but also see if it applies to other collectors.
Keywords: disodium carboxymethyl trithiocarbonate (Orfom ® D8), depressant, xanthate, other sulfide collec-
tors, chalcopyrite-molybdenite (Cu-Mo) flotation
INTRODUCTION
Froth flotation is a reliable and widely used process for sep-
arating minerals in a slurry based on differences in hydro-
phobicity. Hydrophobic differences can be established
naturally but typically require various reagents such as
collectors, activators, depressants, modifiers, and frothers.
Collectors are used to make minerals hydrophobic by inter-
acting with their surfaces via physisorption, chemisorption,
or surface precipitation. Activators are used to enhance col-
lector interaction whereas depressants are used to prevent
it. Modifers are typically used for pH control but work as
activators for some minerals and depressants for others.
When air is injected into the slurry, air bubbles are gener-
ated and attach to hydrophobic minerals causing them to
float into a froth made stable by frothers. Removing the
froth forms a concentrate resulting in a separation. Minerals
that remain in the slurry are hydrophilic and report to the
tails. Normally, it is the valuable minerals that are made
hydrophobic and invaluable minerals that remain hydro-
philic [9,19] however, there are practices of reverse flotation
where the opposite is done.
In polymetallic sulfide flotation systems such as Cu-Mo,
inorganic depressants are often used to achieve separation
which poses environmental, economic, and safety concerns
Surface Chemistry of Disodium Carboxymethyl Trithiocarbonate
(Orfom® D8) for Depressing Cu in Chalcopyrite-Molybdenite
Separation
Patrick Jeff Mensah, Trenin Bayless, Courtney Young
Metallurgical &Mineral Processing Engineering, Montana Technological University
Debbie Laney, Shawn Childress, Chad Brown
Chevron-Phillips Chemical
ABSTRACT: In traditional chalcopyrite-molybdenite (Cu-Mo) separation, NaSH and NaCN are the most
commonly used depressants however, these inorganic chemicals raise environmental, safety and economic
concerns. Hence, attention has shifted to organic depressants, particularly disodium carboxymethyl
trithiocarbonate (Orfom ® D8). For the past 8 years, Montana Tech investigators collaborated with Chevron-
Phillips Chemical Company to determine how this depressant works. Through a variety of techniques and
with ethyl xanthate as collector, they determined that, because it does not desorb the xanthate, it co-adsorbs
and thereby masks the xanthate hydrophobicity. This makes the chalcopyrite hydrophilic, thus causing it to
become depressed. In this study, a variety of different analytical techniques were explored to not only confirm
this mechanism but also see if it applies to other collectors.
Keywords: disodium carboxymethyl trithiocarbonate (Orfom ® D8), depressant, xanthate, other sulfide collec-
tors, chalcopyrite-molybdenite (Cu-Mo) flotation
INTRODUCTION
Froth flotation is a reliable and widely used process for sep-
arating minerals in a slurry based on differences in hydro-
phobicity. Hydrophobic differences can be established
naturally but typically require various reagents such as
collectors, activators, depressants, modifiers, and frothers.
Collectors are used to make minerals hydrophobic by inter-
acting with their surfaces via physisorption, chemisorption,
or surface precipitation. Activators are used to enhance col-
lector interaction whereas depressants are used to prevent
it. Modifers are typically used for pH control but work as
activators for some minerals and depressants for others.
When air is injected into the slurry, air bubbles are gener-
ated and attach to hydrophobic minerals causing them to
float into a froth made stable by frothers. Removing the
froth forms a concentrate resulting in a separation. Minerals
that remain in the slurry are hydrophilic and report to the
tails. Normally, it is the valuable minerals that are made
hydrophobic and invaluable minerals that remain hydro-
philic [9,19] however, there are practices of reverse flotation
where the opposite is done.
In polymetallic sulfide flotation systems such as Cu-Mo,
inorganic depressants are often used to achieve separation
which poses environmental, economic, and safety concerns
