XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2279
were conducted at pH levels of 9, 10 and 11, which are
often used in commercial flotation operations. The experi-
ments were performed using a volume of 200 mL, 2 grams
of REMs, and a SHA concentration of approximately 5 ×
10–4 molarity. The mass of SHA was determined utilizing
these operational parameters depicted in Equation 1:
5 10 0.2
153.14g
0.0153 M L mol g SHA 4 #=-(1)
where, the molecular weight of SHA is 153.14 g per mole.
To begin, 200 mL of deionized water was poured into a
beaker and the pH was adjusted to the required level using
sodium hydroxide (NaOH) and hydrochloric acid (HCl)
as needed. Subsequently, the quantities of REM and SHA
were measured. Following that, specified quantities of SHA
were added and left to dissolve for 20 minutes, resulting
in a uniform solution. SHA has a slightly acidic nature,
necessitating further pH modification. After the target pH
was reached, an initial absorbance measurement was taken
using a VWR UV-Vis 3100 PC. To do this, a 5 mL aliquot
of the SHA solution was extracted using a 10 mL dispos-
able syringe equipped with a 0.45-micron filter to remove
solids. The 5 mL solution was then added to a small bea-
ker containing 10 mL of a pre-prepared ferric perchlorate
solution resulting in a purple color. The intensity of the
purple color was directly proportional to the concentration
of SHA. Consequently, SHA concentrations decrease, the
intensity of the purple decreases. A small aliquot of the pur-
ple solution was subsequently transferred into a UV quartz
cuvette which is inserted into the UV-Vis spectrophotom-
eter to measure absorbance. The modified version of Beer’s
Law shown in Equation 2 was used to calculate the SHA
concentration:
.24
.1121
x
y
253
0
=
-
(2)
where, x is the concentration in moles/liter, y is the UV
absorbance, and 253.24 is the molar absorptivity of SHA.
Following the measurement of the initial concentration,
the REMs were introduced into the original 200 mL SHA
solution and the procedure for measuring concentration
was repeated at various times so that adsorption kinetics
could be followed. Typically, 8 timed samples were col-
lected over 3 hours.
Adsorption Density Studies and Surface Area
Measurements
REM surface areas were measured using Aton Paar Nova
800 BET analyzer. This equipment determines the surface
area in square meters per gram (m2/g) utilizing BET theory,
which elucidates the physical adsorption of gas molecules
on a solid surface. The BET analyzer has a constant flow
of nitrogen gas passing over the sample whose surface
area is being quantified. If the sample is at liquid nitrogen
temperature, some of the nitrogen gas will condense into
a monolayer on the surface. When the condensed gas is
warmed, it will evaporate, and the amount evaporated will
be determined. Because the cross-sectional area of a nitro-
gen molecule is known, the surface area of the sample can
then be determined in m2/g but is multiplied by 10,000
to convert to cm2/g. Resulting surface areas were then
utilized for adsorption density calculations as determined
with Equation 3 based on traditional solution depletion
calculations:
MW
V^Lh
Ct
mol
mg
g
cm 2 C =-
b e ^gh
^Ci
lA oREM
h (3)
where, V is the volume in liters, and Ci and Ct represent
the initial and timed concentrations in milligrams/liter,
respectively, A is the surface area of the REM in cm2/g, MW
denotes the molecular weight of SHA in mg/mol, REM
denotes the weight of the REM in grams, and adsorption
density (Γ) represents the moles of SHA that is adsorbed per
unit surface area which is expressed in moles/cm2. Typically,
V =0.2 liters and Ci =5×10–4 M SHA. All experiments
were conducted at room temperature near 20°C. Results
are compared, including with the literature, to help broadly
discern if adsorption is relatively strong or weak.
RESULTS AND DISCUSSIONS
A variety of equilibrium tests were conducted to examine
the adsorption mechanism of the anionic collector SHA
and a set of selected RESs: lanthanum (La), neodymium
(Nd), and dysprosium (Dy). Subsequently, these same ele-
ments were juxtaposed with the findings of equilibrium
studies conducted on their respective oxide, carbonate,
and phosphate types (Sime 2018 Trant 2018 Galt 2017).
The measurement of collector depleting from solution and
adsorbing onto the surface of REMs was conducted by con-
sidering the factors of time and pH variation (9, 10 and
11). The data was transformed into adsorption density so
that results could be compared.
RECs, REPs and REOs
Salicyl hydroxamic acid (SHA) was used as the collector
in this research. The structure of SHA is illustrated in the
insert in Figure 2, where the reactive inorganic head group
is hydroxamic acid and the inert organic tail is benzene. As
indicated, the head group’s atomic spacing is 2.42 Å. It is
were conducted at pH levels of 9, 10 and 11, which are
often used in commercial flotation operations. The experi-
ments were performed using a volume of 200 mL, 2 grams
of REMs, and a SHA concentration of approximately 5 ×
10–4 molarity. The mass of SHA was determined utilizing
these operational parameters depicted in Equation 1:
5 10 0.2
153.14g
0.0153 M L mol g SHA 4 #=-(1)
where, the molecular weight of SHA is 153.14 g per mole.
To begin, 200 mL of deionized water was poured into a
beaker and the pH was adjusted to the required level using
sodium hydroxide (NaOH) and hydrochloric acid (HCl)
as needed. Subsequently, the quantities of REM and SHA
were measured. Following that, specified quantities of SHA
were added and left to dissolve for 20 minutes, resulting
in a uniform solution. SHA has a slightly acidic nature,
necessitating further pH modification. After the target pH
was reached, an initial absorbance measurement was taken
using a VWR UV-Vis 3100 PC. To do this, a 5 mL aliquot
of the SHA solution was extracted using a 10 mL dispos-
able syringe equipped with a 0.45-micron filter to remove
solids. The 5 mL solution was then added to a small bea-
ker containing 10 mL of a pre-prepared ferric perchlorate
solution resulting in a purple color. The intensity of the
purple color was directly proportional to the concentration
of SHA. Consequently, SHA concentrations decrease, the
intensity of the purple decreases. A small aliquot of the pur-
ple solution was subsequently transferred into a UV quartz
cuvette which is inserted into the UV-Vis spectrophotom-
eter to measure absorbance. The modified version of Beer’s
Law shown in Equation 2 was used to calculate the SHA
concentration:
.24
.1121
x
y
253
0
=
-
(2)
where, x is the concentration in moles/liter, y is the UV
absorbance, and 253.24 is the molar absorptivity of SHA.
Following the measurement of the initial concentration,
the REMs were introduced into the original 200 mL SHA
solution and the procedure for measuring concentration
was repeated at various times so that adsorption kinetics
could be followed. Typically, 8 timed samples were col-
lected over 3 hours.
Adsorption Density Studies and Surface Area
Measurements
REM surface areas were measured using Aton Paar Nova
800 BET analyzer. This equipment determines the surface
area in square meters per gram (m2/g) utilizing BET theory,
which elucidates the physical adsorption of gas molecules
on a solid surface. The BET analyzer has a constant flow
of nitrogen gas passing over the sample whose surface
area is being quantified. If the sample is at liquid nitrogen
temperature, some of the nitrogen gas will condense into
a monolayer on the surface. When the condensed gas is
warmed, it will evaporate, and the amount evaporated will
be determined. Because the cross-sectional area of a nitro-
gen molecule is known, the surface area of the sample can
then be determined in m2/g but is multiplied by 10,000
to convert to cm2/g. Resulting surface areas were then
utilized for adsorption density calculations as determined
with Equation 3 based on traditional solution depletion
calculations:
MW
V^Lh
Ct
mol
mg
g
cm 2 C =-
b e ^gh
^Ci
lA oREM
h (3)
where, V is the volume in liters, and Ci and Ct represent
the initial and timed concentrations in milligrams/liter,
respectively, A is the surface area of the REM in cm2/g, MW
denotes the molecular weight of SHA in mg/mol, REM
denotes the weight of the REM in grams, and adsorption
density (Γ) represents the moles of SHA that is adsorbed per
unit surface area which is expressed in moles/cm2. Typically,
V =0.2 liters and Ci =5×10–4 M SHA. All experiments
were conducted at room temperature near 20°C. Results
are compared, including with the literature, to help broadly
discern if adsorption is relatively strong or weak.
RESULTS AND DISCUSSIONS
A variety of equilibrium tests were conducted to examine
the adsorption mechanism of the anionic collector SHA
and a set of selected RESs: lanthanum (La), neodymium
(Nd), and dysprosium (Dy). Subsequently, these same ele-
ments were juxtaposed with the findings of equilibrium
studies conducted on their respective oxide, carbonate,
and phosphate types (Sime 2018 Trant 2018 Galt 2017).
The measurement of collector depleting from solution and
adsorbing onto the surface of REMs was conducted by con-
sidering the factors of time and pH variation (9, 10 and
11). The data was transformed into adsorption density so
that results could be compared.
RECs, REPs and REOs
Salicyl hydroxamic acid (SHA) was used as the collector
in this research. The structure of SHA is illustrated in the
insert in Figure 2, where the reactive inorganic head group
is hydroxamic acid and the inert organic tail is benzene. As
indicated, the head group’s atomic spacing is 2.42 Å. It is