3400 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
to operate as it is a sensitive technology. Organic solvents
used in solvent extraction are volatile resulting in evapora-
tive losses. They are also flammable and toxic. Release to
the environment or misuse of the solvent may cause envi-
ronmental harm. SX inevitably suffers from a certain level
of entrainment across the separation boundary. To some
extent this can be mitigated by circuit configuration, but it
can be challenging to achieve extremely low levels of impu-
rities in the product solution.
Case Examples
A few reagents have been implemented in the application of
SX to manganese purification. The most common reagents
are the phosphinic acid reagent Cyanex 272 (bis(2,4,4 tri-
methylpentyl) phosphinic acid) and the phosphoric acid
reagent D2EHPA (di(2-ethylhexyl) phosphoric acid). The
extraction mechanism used by D2EHPA and Cyanex 272
is through a cation-exchange mechanism. The extraction
order of base metals as a function of pH50 for D2EHPA is
as follows (Cheng, 2000)
Fe3+ Zn2+ Ca2+ Mn2+ Cu2+ Co2+ Ni2+ Mg2+
Figure 3 shows the relationship between pH and the
extraction of base metals for D2EHPA.
Several studies have been done with success to quantify
the purification and recovery of Mn in solution from base
metals such as Fe, Zn, Mg, Co, Ni. It is apparent from
Figure 3 for D2EHPA that Zn and Ca (to some extent)
could be extracted separately from Mn. Similarly Mn and
Cu could be extracted separately from Co and Ni (Cheng,
2000). The extraction of the divalent base metals is depen-
dent temperature and pH. Better separation of Mn from
Co can be achieved at a higher pH 2.5–3.5, and better sep-
aration of Mn from Co and Ni can be achieved at higher
temperatures (Nadimi and Karazmoudeh, 2021).
It is important to note that the solution should not
contain ferric ions (Fe3+). Fe3+ is strongly bonded with
D2EHPA and extremely challenging to strip. Typically, it
requires high concentration hydrochloric acid (6 M), which
compels the use of costly materials of construction and risks
the introduction unwanted chlorides into the system.
The extraction order for base metals as a function of
pH50 for Cyanex 272 is as follows (Sole, 2008)
Fe3+ Zn Cu Mn Co Mg Ca Ni
The extent of extraction as a function of pH is shown in
Figure 4.
Cyanex 272 extracts Zn separately from Mn across a
larger pH range, pH 1.0–3.0, while D2EHPA extracts Zn
from Mn at a pH range 2.0–3.0 (Falco et al., 2014). Cyanex
272 showed higher selectivity Zn2+ over Mn2+. From the
cited investigation it was concluded that Cyanex 272 is bet-
ter to separate impurities such as Zn2+ and Fe3+ from Mn2+
in solution. But it provides less separation of Mn from Co
and Ni is solution.
There is no data that shows that Mn can be exclusively
extracted in solution. Therefore, SX Mn separation and
recovery processes have to be combined with other base
metal removal steps. Solvent extraction has the capability to
be used to purify and separate Mn from solutions contain-
ing base metal elements such as Zn, Co and Ni. D2EHPA
also has economic advantages over Cyanex 272 for solvent
extraction. It can be used to efficiently separate Fe and Zn
from Mn, and separate Mn and Cu from Co, Ni and Mg.
Figure 3. Extraction of base metals as function of pH by D2EHPA (Sole, K.C. and Cole,
P. M., 2001)
to operate as it is a sensitive technology. Organic solvents
used in solvent extraction are volatile resulting in evapora-
tive losses. They are also flammable and toxic. Release to
the environment or misuse of the solvent may cause envi-
ronmental harm. SX inevitably suffers from a certain level
of entrainment across the separation boundary. To some
extent this can be mitigated by circuit configuration, but it
can be challenging to achieve extremely low levels of impu-
rities in the product solution.
Case Examples
A few reagents have been implemented in the application of
SX to manganese purification. The most common reagents
are the phosphinic acid reagent Cyanex 272 (bis(2,4,4 tri-
methylpentyl) phosphinic acid) and the phosphoric acid
reagent D2EHPA (di(2-ethylhexyl) phosphoric acid). The
extraction mechanism used by D2EHPA and Cyanex 272
is through a cation-exchange mechanism. The extraction
order of base metals as a function of pH50 for D2EHPA is
as follows (Cheng, 2000)
Fe3+ Zn2+ Ca2+ Mn2+ Cu2+ Co2+ Ni2+ Mg2+
Figure 3 shows the relationship between pH and the
extraction of base metals for D2EHPA.
Several studies have been done with success to quantify
the purification and recovery of Mn in solution from base
metals such as Fe, Zn, Mg, Co, Ni. It is apparent from
Figure 3 for D2EHPA that Zn and Ca (to some extent)
could be extracted separately from Mn. Similarly Mn and
Cu could be extracted separately from Co and Ni (Cheng,
2000). The extraction of the divalent base metals is depen-
dent temperature and pH. Better separation of Mn from
Co can be achieved at a higher pH 2.5–3.5, and better sep-
aration of Mn from Co and Ni can be achieved at higher
temperatures (Nadimi and Karazmoudeh, 2021).
It is important to note that the solution should not
contain ferric ions (Fe3+). Fe3+ is strongly bonded with
D2EHPA and extremely challenging to strip. Typically, it
requires high concentration hydrochloric acid (6 M), which
compels the use of costly materials of construction and risks
the introduction unwanted chlorides into the system.
The extraction order for base metals as a function of
pH50 for Cyanex 272 is as follows (Sole, 2008)
Fe3+ Zn Cu Mn Co Mg Ca Ni
The extent of extraction as a function of pH is shown in
Figure 4.
Cyanex 272 extracts Zn separately from Mn across a
larger pH range, pH 1.0–3.0, while D2EHPA extracts Zn
from Mn at a pH range 2.0–3.0 (Falco et al., 2014). Cyanex
272 showed higher selectivity Zn2+ over Mn2+. From the
cited investigation it was concluded that Cyanex 272 is bet-
ter to separate impurities such as Zn2+ and Fe3+ from Mn2+
in solution. But it provides less separation of Mn from Co
and Ni is solution.
There is no data that shows that Mn can be exclusively
extracted in solution. Therefore, SX Mn separation and
recovery processes have to be combined with other base
metal removal steps. Solvent extraction has the capability to
be used to purify and separate Mn from solutions contain-
ing base metal elements such as Zn, Co and Ni. D2EHPA
also has economic advantages over Cyanex 272 for solvent
extraction. It can be used to efficiently separate Fe and Zn
from Mn, and separate Mn and Cu from Co, Ni and Mg.
Figure 3. Extraction of base metals as function of pH by D2EHPA (Sole, K.C. and Cole,
P. M., 2001)