– 24 –
Flotation of REO Minerals
24.1
ORE AND MINERALS CONTAINING RARE EARTH OXIDE
ELEMENTS (REOE)
There are about 250 minerals that contain REOEs, but only a few of these minerals are of
any economic value. Most of them contain uranium, titanium, tantalum and niobium. Based
on the composition of the REOE minerals, they are classified into two main groups
[1]. These are:
1.
2.
The cerium group of REOEs, in which loparit, bastnaesite, parisit, monazite, eshipit
and ortit are included.
The yttrium group of REOEs, this group includes ytroparisite, fergusonite,
samarskite, priorit, kenotime, gadolinite, amongst others.
Table 24.1 lists the major REO minerals of economic value. REO minerals are also divided
into two sub-groups, complex and selective complex minerals, all containing lantanoids (from
cerium to lutecium). The selective group contains elements from onto or the other group.
Most of the products that come from REOEs are monacite, bastnaesite and euxenite.
Monazite belongs to the phosphate group of REOEs, with low magnetic properties and
bright yellow colour. Usually it is found in pegmatites and granites and also entrained in
zircon, magneite and ilmenite. During decomposition of hard rock ores, monazite, due to its
chemical stability, is contained in sand deposits together with ilmenite, zircon, magneite and
other minerals. The minimum content of monazite found in a sand deposit is about 1%.
Bastnaesite belongs to the carbonatite group of minerals that contain REOEs. Beside the
cerium group of elements, bastnaesite also contains yttrium and europium. Typically, it
contains 65–75% REOE. Bastnaesite is usually found in pegmatites, carbonatite and
hydrothermal ore bodies in alkaline gangue minerals. Because it is poor chemically and
stable, it is not found in mineral sand deposits.
Euxenite is a titanotantalum/niobium-containing mineral and has a complex formula
(Table 24.1) with variable chemical composition. It is usually found in sand deposits
together with monazite, xenotime, zircon, beryl, columbite and other minerals.
The major minerals that contain REOE include apatite, phosphates, sfen, perovskite,
eudialite, pyrochlore and ortit, some of which contain significant quantities of REOE.
151
152
Table 24.1
REO minerals of economic value
Formula
Relative REOE content
Monazite
(Ce,La…)PO4
50–68% (Ca,La…)2O3, 22–31% P2O5, 4–12% ThO2, �7% ZrO2, �6% SiO2 4.9
5.5
Bastnaesite
(Ce,La,Pr)[CO3]F
36–40% Ce2O3, 36% (La…Pr)2O3, 19–20% CO3, 6–8% F
4.5
4.5
Xenotime
YPO4
52–62% Y2O3, Ce, Er as impurities, Th, �5% U, 3% ZrO2 �, 9% SiO2
4.6
4.5
Parasite
Ca(Ce,La…)2[CO3]3F2
11% CaO, 26–31% Ce2O3, 27–30% (La,Nd)2O3, 24% CO2, 6% F
4.3
4.5
Yttrocerite
(Ca,Y,Ce,Er)F2-3H2O
19–32% Ca, 8–11% Ce, 14–37% Y, 37–42% F
3.8
4.5
Gadolinite
(Y,Ce2)Fe,BeSi2O10
10–13% FeO, 30–46% YO3, 25% SiO2, 5% (Ce,La…)2O2, 9–10% BeO
4–4.5
6.5–7
Ortit
(Ca,Ce)2(Al,Fe)3SiO2[O,OH]
6% Ce2O3, 7%(La…)O3, 4% BeO, 8% Y2O3
Loparit
(Na,Ca,Ce,Sr)2(Ti,Ta,Nb)2O6
39–40% TiO2, 34% (Ce,La…)2O3, 8–11% (Ta,Nb)2O5, 5% CaO, Cr,Th as
impurities
4.8
6
Esxenit
(Y,Ce,Ca,U,Th)(Ti,Nb,Ta)2O6
18–28% (Y,Er)2O3, 0.2–3% (CeLa…)2O3, 16–30% TiO2, 4–47% Nb2O5,
1.3–33% Ta2O5, 0.4–12% U3O8
4.9
5.5
Fergusonite
(Y,Sr,Ce,U)(Nb,Ta,Ti)O4
46–57% (Nb,Ta)2O5, 31–42% Y2O3, 14% Er2O3, 1–4% ThO2, 1–6% UO2
5.6-6.2
5.5–6.5
Samarskit
(Y,Er,U,Ce,Th)4(Nb,Ta)6O21
6–14% Y2O3, 2–13% Er2O3, 3% Ce2O3, 0.7–4% (Pr,Nd)2O3, 27–46%
Nb2O5, 1.8–27% Ta2O5, Sn, U, Fe as impurities
5.6–5.8
5–6
Priorit
(Y,Er,Ca,Th)(Ti,Nb)2O6
21–28% (Y,Er)2O3, 3–4% Ce2O3, 21–34% TiO2, 15–36% Nb2O5, 0.6–7%
ThO2, 0–5% UO2
7.8–5
5.6
Eschynite
(Ce,Ca,Th)(Ti,Nb)2O6
15–19% Ce2O3, 0.9–4.5% (Y,Er)2O3, 21–24% TiO2, 23–32% Nb2O5, 0–7%
Ta2O5, 11–17% ThO2
24.
Mineral
Flotation of REO Minerals
24.2
Flotation Properties of Cerium Group of Reoe Minerals
153
Loparite (Nb-mineral) contains, for example, three times more REOE than niobium. It
represents titanotantalo-niobium REOE ore. Loparite is found in pegmatites and nephelinecontaining ores.
Monazite, bastnaesite and loparite contain exclusively cerium group of REOEs.
Other minerals containing REOE, such as fergusonite, priorite and samerskite are usually
accessory minerals that contain tantalum, niobium, uranium and thorium.
24.2
24.2.1
FLOTATION PROPERTIES OF CERIUM GROUP OF REOE MINERALS
Flotation properties of monazite and bastnaesite
From disseminated ores contained in mineral lenses, the recovery of bastnaesite and
monazite is accomplished using flotation. The flotation properties of bastnaesite and
monazite are similar to the gangue minerals contained in the bastnaesite and monazite,
such as calcite, barite, apatite, tourmaline, pyrochlore and others, which represent difficul­
ties in selective flotation. However, in recent years, significant progress has been made in
the flotation of both monazite and bastnaesite [2,3].
Monazite is readily floatable using cationic collectors such as oleic acid and sodium
oleate in the pH region of 7–11. Monazite does not float readily using, for example, laurel
amine or anionic collectors. Adsorption of the sodium oleate on the monazite increases
with an increase in pH, indicating that monazite does not float in acid pH, while pyrochlore
is readily floatable and is depressed at a pH greater than 10. Figure 24.1 shows the effect of
pH on flotation of monazite, pyrochlore and zircon.
100
Monazite
Recovery (%)
80
60
40
Zircon
20
Pyrochlore
0
4
Figure 24.1
6
8
Flotation pH
10
12
Effect of pH on flotation of monazite, zircon and pyrochlore.
154
24.
Flotation of REO Minerals
100
Monazite
Recovery (%)
80
60
40
Pyrochlore
Zircon
20
0
0.0
Figure 24.2
0.5
1.0
1.5
2.0
2.5
Na2S addition (g/t)
3.0
3.5
4.0
Effect of Na2S on the recovery of monazite, zircon and pyrochlore.
It was found that Na2S�9H2O is a selective regulating agent during monazite flotation at
additions of 2–3 kg/t Na2S, both zircon and pyrochlore are depressed while monazite
floatability remains unchanged or, in the case of some ores, improves. Figure 24.2 [4]
shows the effect of Na2S on the flotation of zircon, pyrochlore and monazite.
Flotation properties of bastnaesite depend largely on the gangue composition of the ore
and the impurities present in the mineral itself. Bastnaesite found in a carbonatite ore is
recovered using fatty acid collector after heat pretreatment of the flotation feed. The effect
of heat temperature on bastnaesite grade–recovery is illustrated in Figure 24.3.
Floatability of bastnaesite found in barite–fluorite ores is extremely poor using either fatty
acid flotation or sodium oleate. Research work conducted on an ore from Central Asia
showed that the floatability of bastnaesite improved significantly after barite preflotation [5].
The flotation of bastnaesite from a carbonatite ore improved with the use of oleic acid
modified with phosphate ester. The flotation of bastnaesite from deposits of pegmatitic origin
can be successfully accomplished with several types of collectors, including tall oil modified
with secondary amine, and tall oil modified with petroleum sulphonate-encompassing group.
O
R S R
O
The effect of the tall oil modification on bastnaesite metallurgical results is presented in
Table 24.2. Data shown in this table indicates that the use of a modified tall oil resulted in
significant improvement in the metallurgical results of bastnaesite.
24.2
Flotation Properties of Cerium Group of Reoe Minerals
155
100
Heated,
ambient 85°C
REO recovery (%)
80
60
40
20
Heated
to 40°C
Unheated
to 18°C
0
10
Figure 24.3
20
30
40
50
Concentrate grade (% REO)
60
70
Effect of heat temperature on bastnaesite grade–recovery relationship.
Table 24.2
Effect of tall oil modifications on bastnaesite flotation from pegmatitic ores
Collector
Product
Tall oil fatty acid
Weight (%) Total % REO assays % REO recovery
REO concentrate
10.77
REO combined tail 89.23
Feed
100.00
Tall oil modified with REO concentrate
10.59
Secondary amine
REO combined tail 89.41
(amine acetate)
Feed
100.00
Tall oil modified with REO concentrate
10.45
Petroleum sulphonate REO combined tail 89.55
Feed
100.00
24.2.2
48.5
2.07
7.08
60.1
0.74
7.02
62.2
0.61
7.05
73.8
26.2
100.0
90.5
9.5
100.0
92.3
7.7
100.0
Flotation properties of REO-containing yttrium
There is very little literature relevant to flotation of REO-containing yttrium. Yttrocerite,
gadolinite, fergusonite and priorit are often found in relatively complex ores containing
quartz, chlorite and sericite. Two or all of the above minerals are found together in some
deposits. Some of the complex deposits of hydrothermal origin contain zircon together with
REO from yttrium groups. Usually the ores that contain yttrium group minerals belong to
156
24.
Flotation of REO Minerals
disseminated ores where liberation occurs at <74 µm size, so the only method available for
beneficiation of these ores is flotation.
Limited research studies [6] show that the minerals from the yttrium groups can
be recovered using alkyl hydroxamate collectors which form complex reactions with
REO.
It has been found that yttrocerite and gadolinite readily float with hydrohamic acid at a
pH of 9–10. The proposed treatment flowsheet for beneficiation of REO-containing yttrium
is presented in Figure 24.4.
Using the flowsheet shown above, a concentrate grade of 65% REO+Y2O3 at a 72–75%
Y2O3 recovery can be achieved on some ores. Research work has shown that the efficiency
Feed
Grinding
Desliming 1
Slimes
Desliming 2
Slimes
Sand
Conditioning 1
Conditioning 2
Y2O3/REO
rougher
Y2O3/REO
scavenger
Conditioning
Y2O3/REO
1st cleaner
Y2O3/REO
cleaner scavenger
Y2O3/REO
2nd cleaner
Conditioning
Y2O3/REO
3rd cleaner
Y2O3/REO
scalper
Y2O3/REO
4th cleaner
Y2O3/REO concentrate
Figure 24.4
Total
tailings
Generalized flowsheet for beneficiation of yttrium group of minerals using flotation.
24.2
Flotation Properties of Cerium Group of Reoe Minerals
157
of alkyl hydroxamate for flotation of yttrium group REO can be improved by changing the
alkyl group to iso-alcohol of fraction C12–C16, for example, isododecil alcohol:
CH (CH2)3 CH CH2 CH CH2OH
C2H2
C2H5
This hydroxamate is selective towards calcite, fluorite and sericite. The yttrium group
minerals that contain zircon also have highly complex mineral compositions. These ores
contain fergusonite, euxenite and priorit besides other minerals that contain REO. Such
deposits are found in Northern Canada (Thor Lake).
Limited research work has been conducted on these ores, but have indicated that REO
cannot be recovered using either fatty acid or sodium oleate. It was, however, found that a
mixture of sulphosuccinamate and phosphate ester modified with alkylsulphate can recover
REO and zircon efficiently. Figure 24.5 shows the effect of above collector mixture
(KBX3) on REO recovery from complex REO–ZrO2 ores. Oxalic acid and fatty acid
(FA3) were not so effective compared to collector KBX3.
As can be seen from the data shown in Figure 24.5, poor results were achieved using
either fatty acid or sodium oleate collector.
In the case of REO-containing zircon, there is a strong relationship between zircon
recovery and the recovery of REO from the yttrium group of REOs. This relationship is
illustrated in Figure 24.6.
100
Collector KBX3
80
REO recovery (%)
FA3 fatty acid
60
Sodium oleate
40
20
0
0
Figure 24.5
100
200
300
400
Collector addition (g/t)
500
600
Effect of different collectors on REO recovery from complex REO–ZrO2 ores.
158
24.
Flotation of REO Minerals
100
REO recovery (%)
80
60
40
20
0
0
20
40
60
Zircon recovery (%)
80
100
Figure 24.6 Relationship between zircon and REO recovery in the bulk zircon REO concentrate.
This is due to the fact that zircon present in these ores contains a portion of REO as
inclusions in the mineral itself.
In a number of cases, the REO from the yttrium group contains significant amounts of
pyrochlore and/or tantalum columbite. Both minerals usually float with the zircon and REO
minerals.
24.3
24.3.1
FLOTATION PRACTICES AND RESEARCH WORK ON
BENEFICIATION OF REO MINERALS
Introduction
A large portion of the REOs are produced from monazite- and bastnaesite-containing ores.
In the majority of cases, bastnaesite and monazite ores are relatively complex and contain
gangue minerals (calcite, barite, fluorite and apatite) with similar flotation properties as the
monazite and bastnaesite.
Monazite is also found in heavy mineral sands, which are usually recovered
using physical concentration methods, such as gravity, magnetic and electrostatic
separation.
Some deposits in addition to REO contain zircon and titanium minerals. From these ores,
REO and zircon can be recovered in bulk concentrate suitable for hydrometallurgical
treatment.
24.3
Flotation Practices and Research Work on Beneficiation of Reo Minerals
24.3.2
159
Flotation practice in the beneficiation of bastnaesite-containing ores
The Mountain Pass (USA) operation treats a relatively complex ore. The major REO
mineral is bastaenesite with minor amounts of synchisite, parasite and monazite. The
major gangue minerals are calcite, barite, silicates, and dolomite. The amount of the
individual gangue minerals in this ore are variable and change on a yearly basis. There
are two major ore types treated at the Mountain Pass concentrator: (a) high calcite ore
(35–45% CaO) and (b) a high barite–dolomite ore (so-called brown ore). Barite also
contains significant quantities of strontium.
Liberation of the Mountain Pass ore has been extensively studied on the mill feed ore
and on the plant product. Grinding the ore to a K80 of about 56 µm is required to achieve
liberation. Locking between the bastnaesite and calcite above 50 µm is common. Usually
calcite/bastnaesite middlings reports to the final concentrate.
Over the past 20 years, extensive studies were conducted in which different reagent
schemes were evaluated. The following is a brief summary of the findings:
•
•
•
•
Hydroxamic acid used as a collector has shown to give better selectivity than fatty
acid. However, it has yet to be tested in an operating plant.
Extensive work has been carried out to evaluate different fatty acids. There are
contradictory conclusions among different researchers regarding the performance of
different fatty acids. Studies performed by the US Bureau of Mines (Reno, NV, USA)
confirmed that distilled acid gave results superior to those of linoleic acid or fatty acid
containing rosin acid. Studies conducted at the University of New Mexico and at the
Molycorp laboratory showed that distilled tall oil containing rosin acid gave results
better than those of pure oleic acid. These differences are likely due to different
flotation responses related to a variation in the mineralogy.
With respect to different depressant studies, only a limited amount of work has been
performed with Quebracho, tanic acid and different lignin sulphonates. Lignon
sulphonates with a medium molecular weight were superior.
Flotation temperature was the subject of numerous studies. It was concluded that
heating the pulp with collector is the only way to selectively float bastnaesite. Heating
the pulp with collector is believed to result in selective aggregation of bastnaesite in
the form of repellent droplets, which may result in improved selectivity and in a
reduction in slime interference.
The flowsheet used in the Mountain Pass, with reagent additions, is shown in
Figure 24.7. The plant reagent scheme that is currently being used is presented in
Table 24.3.
Weslig is a lignon sulphonate with a molecular weight of about 20,000 and also contains
ethylene oxide. Ethylene oxide serves the purpose of reducing the frothing properties of the
Weslig and improves the Weslig depression efficiency, in particular, for barite.
A typical example of metallurgical results obtained in the plant is shown below
(Table 24.4).
It should be noted that the plant results are variable and depend on the type of ore being
treated. Typical distributions of REO in the Mountain Pass concentrate are shown in
Table 24.5.
160
24.
Flotation of REO Minerals
Feed ore
Na2CO3
Na2SiF6
Thermal
conditioning
Weslig
Thermal
conditioning
Collector
Thermal
conditioning
Collector
Rougher
Scavenger
Weslig
Na2SiF6
Conditioning
Collector
1st cleaner
1st cleaner
scavenger
Weslig
2nd cleaner
Weslig
3rd cleaner
Concentrate
Figure 24.7
Tailings
Mountain Pass (USA) plant flowsheet.
24.3
Flotation Practices and Research Work on Beneficiation of Reo Minerals
161
Table 24.3
Reagent scheme used at the Mountain Pass concentrator
Reagent
Additions (g/t)
Soda ash (Na2CO3)
Sodium fluorosilicate (Na2SiF6)
Lignin sulphonate (Weslig)
Tall oil fatty acid (P25A)
3000–4500
300–600
2400–3500
200–400
Table 24.4
Molycorp plant metallurgical results
Product
Weight (%) Assays (%)
REO
Final bastnaesite concentrate
9.38
Final bastnaesite tailing
90.62
Feed
100.00
%
Distribution
Ce2O3 La2O3 BaSO4 CaO REO
64.1 31.4
2.28 1.06
8.09 3.9
22.2
0.74
2.76
2.7
26.3
26.3
Ce2O3
3.1 75.6 75.5
16.9 24.4 24.5
15.6 100.0 100.0
Table 24.5
Distribution of the REO in the Mountain Pass concentrate
Element
% of Total REO content
Element
% of Total REO content
Lanthanum
Cerium
Praseodymium
Neodymium
Samarium
Europium
Gadolinium
Terbium
33.2
49.1
4.34
12.0
0.790
0.118
0.166
0.0159
Dysprosium
Holmium
Erbium
Thulium
Ytterbium
Lutetium
Yttrium
0.0312
0.0051
0.0035
0.0009
0.0006
0.0001
0.0913
Beneficiation of barite, fluorite and bastnaesite from the Dong Pao deposit in Vietnam
This ore is heavily weathered ore, with more than 30% of the bastnaesite contained in the
–7 µm fraction. The major host minerals present in this ore are barite and fluorite.
Table 24.6 shows the chemical analyses of the ore used in various research studies.
The ore deposit is located in the Lai Chan Province of Vietnam, and was developed by
Sumitomo Metal Mining Company (Japan).
162
24.
Flotation of REO Minerals
Table 24.6
Chemical analyses of the Dong Pao ore
Element
Assays (%)
Total REO
Cerium (Ce2O3)
Lanthanum (La2O3)
Barite (BaSO4)
Fluorite (CaF2)
Silica (SiO2)
Alumina (Al2O3)
Iron (Fe2O3)
Calcium (CaO)
Sodium (Na2O)
Potassium (K2O)
Titanium (TiO2)
Phosphorus (P2O5)
Manganese (MnO)
Chromium (Cr2O3)
Vanadium (V2O5)
LOI
8.72
3.76
3.18
62.5
5.54
8.85
0.97
2.69
0.15
0.54
0.11
0.09
0.13
0.64
0.22
0.03
10.6
Because this ore was high in barite and fluorite, direct flotation of bastnaesite from the
ore was not possible. It should be pointed out that fluorite has similar flotation properties as
bastnaesite and depression of fluorite during bastnaesite flotation is difficult.
Extensive research work [7] has been conducted on this ore, aimed at developing a
commercial treatment process that would produce a high-grade REO concentrate. As a
result, a unique flowsheet and reagent scheme were developed.
The flowsheet that was developed for beneficiation of the Dong Pao ore involves
sequential barite–fluorite–bastnaesite flotation. The flowsheet is presented in
Figure 24.8.
The ore was washed and deslimed before grinding. The fines from the washing con­
tained over 30% of the total bastnaesite present in the ore.
The ground ore was first subjected to barite flotation followed by fluorite flotation. By
floating the barite and fluorite ahead of the bastnaesite, about 70% of the total weight was
removed from bastnaesite flotation feed. The bastnaesite flotation feed was upgraded from
8.5% REO to about 30% REO.
The reagent scheme developed during extensive laboratory testing is presented in
Table 24.7. This reagent scheme is unique in such a way that the collector and number
of depressants involved are composed of a number of chemicals that provide improved
selectivity during sequential flotation of barite and fluorite from bastnaesite.
For flotation of barite, sodium silicate was used as a depressant and barium chlorite as a
barite activator. Barite collector SR82 was composed of petroleum sulphonate, sodium
alkyl sulphate and succinamate mixture. The collector was selective towards both fluorite
and bastnaesite. Over 96% of the barite was recovered in a relatively high-grade
concentrate.
24.3
Flotation Practices and Research Work on Beneficiation of Reo Minerals
163
Feed
Grinding
Conditioning
Conditioning
CaF2 rougher
BaSO4 rougher
CaF2 scavenger
BaSO4 scavenger
CaF2 1st cleaner
BaSO4
1st cleaner
BaSO4 1st cleaner
scavenger
CaF2 2nd cleaner
BaSO4
2nd cleaner
BaSO4
3rd cleaner
CaF2 3rd cleaner
CaF2 concentrate
Thermal conditioning
BaSO4
4th cleaner
Thermal conditioning
Thermal conditioning (75°C)
REO rougher
REO scavenger
BaSO4 concentrate
REO 1st cleaner
REO
tailings
REO 2nd cleaner
REO 3rd cleaner
REO concentrate
Figure 24.8
Flowsheet developed for beneficiation of the Dong Pao ore.
During fluorite flotation, Quebracho and lignin sulphonate mixture (MESB) was used
with collector composed of a mixture of oleic acid and phosphoric ester. Collectors used
for bastnaesite flotation included tall oil fatty acid modified with three ethylene tetra
164
24.
Flotation of REO Minerals
Table 24.7
Reagent scheme developed for beneficiation of the Dong Pao ore
Reagent
Additions (g/t)
Depressants and modifiers
Na2SiO3
BaCl2
NaF
Al2(SO4)3
MESB
Na2CO3
Citric acid
MM4
Collectors
SR82
AKF2
KV3
Fuel oil
BaSO4 circuit
CaF2 circuit
Ro
Cl
Ro
Cl
Ro
Cl
2500
500
–
–
–
–
–
–
1200
400
–
–
–
–
–
–
1500
–
300
600
20
–
–
–
1100
–
400
400
200
–
–
–
–
–
–
–
–
4000
1000
1000
–
–
–
–
–
1400
3500
1300
850
–
–
–
–
–
–
–
–
300
–
–
–
–
–
–
–
–
900
200
–
–
200
–
REO circuit
amine. Depressant MM4 was a mixture of lignin sulphonate with a molecular weight
ranging from 9000 to 20,000.
The results obtained from the continuous locked-cycle tests are summarized in Table 24.8.
The major contaminant of the bastnaesite concentrate was fluorite. Complete fluorite flotation
was not possible without heavy losses of bastnaesite in the fluorite concentrate.
Table 24.8
Continuous locked-cycle test results
Product
BaSO4 Cl concentrate
CaF2 Cl concentrate
REO Cl concentrate
REO combined tail
Head (calc)
BaSO4 Cl concentrate
CaF2 Cl concentrate
REO Cl concentrate
REO combined tail
Head (calc)
Weight (%)
62.83
7.36
13.72
16.09
100.00
62.83
7.36
12.97
16.84
100.00
Assays (%)
% Distribution
BaSO4
CaF2
REO
BaSO4
CaF2
REO
95.8
3.11
8.55
3.47
62.2
95.8
3.11
6.55
4.00
62.0
0.67
44.4
14.8
0.50
5.80
0.67
44.4
16.6
0.61
5.94
0.61
7.57
45.9
6.79
8.33
0.61
7.57
48.4
6.13
8.25
96.8
0.4
1.9
0.9
100.0
97.2
1.4
1.4
1.1
100.0
7.3
56.3
35.0
1.4
100.0
7.1
54.9
36.2
1.7
100.0
4.6
6.7
75.6
13.1
100.0
4.7
6.7
76.1
12.5
100.0
24.3
Flotation Practices and Research Work on Beneficiation of Reo Minerals
24.3.3
165
Flotation practices in beneficiation of monazite
A large portion of monazite production comes from mineral sand deposits. In the
beneficiation of monazite from mineral sand deposits that contain garnet, ilmenite,
shell and silicates, the physical concentration and combination of physical preconcentra­
tion–flotation is used. Several reagent schemes using flotation were developed
throughout various studies [8–10] and some have been confirmed in continuous pilot
plants.
Flotation of the Indian beach sand (monazite)
India has very large deposits of monazite on the coastal shores of Kerala and Chennai. A
typical mineral composition of this type of deposit is 60% ilmenite, 1.2% rutile, 5% zircon,
6.4% garnet, 4% silinanite, 16% quartz, 2.5–5% monazite and 1–7% shell. Research work
involved different anionic collectors and pH during monazite flotation, along with the level
of sodium silicate used as depressant.
Experimental work conducted at different levels of sodium silicate (Table 24.9) indicates
that sodium silicate is an excellent depressant for titanium, zircon and other gangue
minerals while the monazite flotation is not affected.
The collector used in this experiment was sodium oleate at additions of 300 g/t. In
addition to sodium oleate, other fatty acid collectors were examined. The results are given
in Table 24.10. From these data, the saturated fatty acid soap was a poor collector for
monazite, as well as sodium laurate.
The acintols (mixture of oleic and linoleic acids) were found to give better results
compared to sodium oleate. This can be attributed to the presence of linoleic acid, which
has two double bonds. Furthermore, the rate of monazite flotation increased with the acintol
than with the sodium oleate.
The monazite concentrate in these experiments contained some garnet and sillinmanite.
In conclusion, it can be noted that the effect of pH on flotation of beach sand minerals is
critical in selective flotation of monazite from other minerals.
Table 24.9
Effect of sodium silicate on monazite flotation from Kerala and Chennai beach sand (India)
Reagent
additions (kg/t)
Flotation
pH
Na2SiO3 NaOH
1
3
5
7
9
11
2.2
3.0
5.5
6.5
9.0
8.5
9.2
9.4
9.6
9.7
9.8
9.8
Monazite concentrate
Monazite tailings
Weight
(%)
% Grade % Recovery Weight
(%)
% Grade % Recovery
3.2
10.4
8.3
6.6
5.6
4.8
23.9
33.3
66.2
76.2
84.4
94.3
2.54
0.95
0.28
0.24
0.24
0.40
13.3
37.5
88.4
92.3
85.7
83.6
96.8
89.6
91.7
93.4
94.4
95.2
33.7
62.5
11.6
8.3
5.6
4.8
166
24.
Flotation of REO Minerals
Table 24.10
Effect of different collectors on monazite flotation from the Chennai beach sand
Collector type Addition Monazite concentrate
Monazite tailings
(kg/t)
Weight
% Grade % Recovery Weight (%) % Grade % Recovery
(%)
Sodium laurate
Sodium oleate
Neofat 140
Acintol FA1
Acintol FA2
Acintol FAX
11.4
5.5
5.5
5.0
5.0
5.0
5.0
8.3
9.0
6.1
5.6
5.8
21.4
66.2
57.0
75.5
81.6
71.0
20.0
88.4
89.0
86.4
89.2
77.0
95.0
91.7
91.0
93.9
94.4
94.2
4.6
0.28
0.12
0.23
0.16
0.16
80.0
11.6
11.0
13.6
10.8
23.0
The monazite can be selectively floated from other minerals when using Na2O:SiO2
(1:1) at relatively high doses (i.e. 5 kg/t).
Processing of the black sand monazite at Rosetta
The mineralogy of the Rosetta Nile black sand monazite is relatively complex and contains
a variety of different minerals. Table 24.11 shows the chemical analysis of the run-of-mine ore.
The size distributions of the black sand ranged from 80 to 100 µm. Development testwork on the black sand included an examination of anionic and cationic collectors. Cationic
collectors, such as Amine 22, Armac and Armac T, gave poor results. Selectivity was poor,
even when using modified starches as gangue depressants.
Testwork using monazite depression with lactic acid and flotation of the residual miner­
als with 3-lauril amine hydrochloride achieved a concentrate grading 75.5% monazite at a
recovery of about 70%.
Table 24.11
Analyses of the run-of-mine black sand
Element
Assays (%)
Silica (SiO2)
Titanium (TiO2)
Calcium (CaO)
Magnesium (MgO)
Zircon (ZrO2)
Manganese (MnO)
Iron (Fe2O3)
Alumina (Al2O3)
Sodium (Na2O)
Potassium (K2O)
Phosphorus (P2O5)
Monazite (REO)
13.35
25.8
2.71
1.75
3.72
2.82
39.84
9.24
0.21
0.02
0.10
2.20
24.3
Flotation Practices and Research Work on Beneficiation of Reo Minerals
167
Carboxylic collectors from the carboxylate group
These collectors were examined at a pH of 10 (Cyanamid 700 series) and diluted pulp to
about 15% solids. A monazite recovery of over 95% was obtained when using Cyanamid
collector 710.
Monazite activation using oxalate
Experimental work was carried out on black sand in which the effect of sodium oxalate on
monazite activation was examined. It should be noted that monazite is essentially a
phosphate of cerium and lanthanum, where the possibility exists that sodium oxalate has
an activating effect on monazite [11]. The use of sodium oleate as activator was studied
with different sulphonate collectors (Table 24.12).
It was shown that with the use of sulphonate collectors, sodium oxalate had a positive
effect on monazite grade and recovery. Conditioning time with oxalate had a pronounced
effect on monazite recovery. Figure 24.9 shows the effect of conditioning time with oxalic
acid on monazite recovery.
The data from the figure show that 2–4 min of conditioning time was sufficient to
achieve maximum recovery of monazite using different monazite collectors.
Flotation of Brazilian monazite ore
The Brazilian monazite ore is found as beach sand along rivers in the Sao Goncalodo
Sapucai region. As mentioned earlier, the flotation characteristics of monazite, zircon
and rutile are similar, and separation of these minerals is difficult. The objective of this
research work was to find a reagent scheme that would selectively float the monazite
from the associated minerals (zircon) and rutile. Sao Goncalo ore assayed approxi­
mately 2.9% total ROE, 36.6% TiO2, 7.68% ZrO2, 15.6% SiO2 and 24.6% FeT.
Experimental testing was performed with hydroxamate and sodium oleate as collectors.
The only depressant used was sodium meta-silicate. Comparison of results with the
different collectors is shown in Table 24.13. Hydroxamate was more selective compared
to the results obtained using sodium oxalate. Sodium oxalate, however, gave better
recoveries.
Table 24.12
Effect of different collectors on flotation of monazite using sodium oleate as the activator
Collector
Additions (g/t)
% Monazite concentration
% Monazite recovery
Sulphonate 231
Aeropromoter 710
R260
R376
R276R
R376
900
4000
600
650
700
900
91.0
92.1
85.1
90.5
85.5
90.2
90.9
98.5
96.5
85.0
90.5
93.3
168
24.
Flotation of REO Minerals
100
Monazite recovery (%)
80
Collector
60
R260H
R276F
40
R231
20
0
0
Figure 24.9
collectors.
1
2
3
4
5
Conditioning time (min)
6
7
Effect of conditioning time with sodium oxalate on monazite recovery using different
Table 24.13
Effect of different collectors on monazite flotation using Brazilian beach sand
Reagents
Hydroxamate = 140 g/t
Na2SiO3 = 1200 g/t
Sodium oleate = 525 g/t
Na2SiO3 = 1398 g/t
Product
Feed
Rougher Conc
Rougher Tail
Feed
Rougher Conc
Rougher Tail
Weight (%)
100.00
4.90
95.10
100.00
5.66
94.34
Assays (%)
% Distribution
RE2O3
RE2O3
3.15
57.69
0.34
2.92
49.07
0.16
100.0
89.77
10.23
100.0
94.98
5.02
Monazite flotation from complex ores
There are several large deposits of complex monazite ores, some of which are located in
South Africa and Western Australia. Major research and development testwork has been
performed on the Mount Weld ore from Western Australia.
The Mount Weld ore is highly complex with about 50% of the monazite being contained
in the –25 µm fines. Haematite, Fe-hydroxides, phosphates and alumosilicates are the
principal gangue minerals present in this ore.
24.3
Flotation Practices and Research Work on Beneficiation of Reo Minerals
169
Table 24.14
Head analyses of the Mount Weld ore
Element
Assays (%)
Total REO
Cerium (Ce2O3)
Lanthanum (La2O3)
Samarium (Sm2O3)
Yttrium (Y2O3)
Iron (Fe2O3)
Alumina (Al2O3)
Magnesia (MgO)
Calcium (CaO)
Phosphorus (P2O5)
15.50
9.54
4.21
0.39
0.30
60.5
15.5
4.60
10.8
2.66
The head analyses of the ore are shown in Table 24.14.
Research studies – Ore preparation
The major task involved during ore preparation is to remove the maximum amount of
primary slimes with minimum loss of REO minerals to the slime fraction. The REO losses
in the slime fraction are dependent on the desliming size. Minimum loss of REO to the
slime fraction occurs when desliming is done at a K80 of about 4 µm. Figure 24.10 shows
the effect of desliming size on REO loss in the size fraction.
Monazite recovery in slimes (%)
50
40
30
20
10
0
2
4
6
8
10
Desliming size K80 (µm)
12
14
Figure 24.10 Effect of desliming size on monazite losses in the slime fraction using dispersant DQ4.
170
24.
Flotation of REO Minerals
Table 24.15
Effect of different dispersants from the DQ series on monazite loss in the slime fraction
Desliming size
(µm)
Dispersant
4
4.2
4.1
4.0
4.3
4.0
Slime fraction
Type
Additions
(g/t)
Weight
(%)
% Monazite
assay
% Monazite
recovery
None
DQ2
DQ3
DQ4
DQ6
DQ8
–
800
800
800
800
800
25.0
23.3
23.1
21.5
22.2
23.4
17.8
15.6
13.3
9.4
12.0
11.8
28.7
23.4
19.8
13.0
17.1
17.8
The use of DQ4 in the desliming stage has a significant impact on monazite loss to the
slime fraction. Table 24.15 shows the effect of different dispersants on monazite loss in the
slime fraction, using dispersants from the DQ series. These dispersants are a mixture of
low-molecular-weight acrylic acids modified with surfactant.
The lower monazite losses in the slime fraction were achieved using dispersant DQ4.
Mineralogical examination of the slime fraction, in which dispersants were used,
revealed that about 80% of the slime was composed of Fe-hydroxides and ultrafine
2–3 µm clay.
100
4 kg/t
80
Monazite recovery (%)
2 kg/t
60
0 kg/t
40
20
0
0
Figure 24.11
10
20
30
40
50
Monazite concentrate grade (% REO)
60
Effect of Na2S on the monazite rade–recovery relationship.
24.3
Flotation Practices and Research Work on Beneficiation of Reo Minerals
171
Flotation studies
Flotation studies were carried out on ground, deslimed ore. The optimum grinding fineness
was about K80 = 65 µm. A variety of collectors and depressant systems were examined.
Modified fatty acid collectors performed the best on the Mount Weld ore. The use of
Na2S�9H2O in the conditioning had a significant effect on monazite grade and recovery.
Figure 24.11 shows the relationship between monazite grade and recovery at different
levels of Na2S additions.
The final flowsheet and reagent scheme developed for beneficiation of the Mount Weld
ore is shown in Figure 24.12 for grinding and desliming, and in Figure 24.13 for flotation.
The desliming was performed in three stages at 15% pulp density to the desliming feed
cyclone. During flotation, the pulp was conditioned with reagents at about 60% solids.
Collector CB110 is composed of a mixture of fatty acids modified with hydrocarbon
oil and then oxidized. The final results obtained in continuous operation are presented
below (Table 24.16).
Feed
Scrubbing
Coarse
Washing
Fines
Grinding
Fines
DQ4
300 g/t
Conditioning
Final slimes
to tailings
Cyclones
to flotation
Figure 24.12 Final grinding and desliming flowsheet.
172
24.
Flotation of REO Minerals
Ground deslimed ore
1000 g/t Na2SiO3
600 g/t Na2CO3
Conditioning 1
500 g/t dextrose/quebracho
600 g/t collector CB110
Conditioning 2
2000 g/t Na2S
Conditioning 3
200 g/t collector
CB110
REO rougher
REO scavenger
200 g/t dextrose/quebracho
100 g/t DA663
1000 g/t Na2S
Conditioning
REO
1st
200 g/t collector
CB110
cleaner
REO 1st cleaner
scavenger
200 g/t dextrose/quebracho
2000 g/t Na2S
Conditioning
REO 2nd cleaner
200 g/t dextrose/quebracho
100 g/t Na2S
Conditioning
REO 3rd cleaner
REO cleaner
concentrate
REO
combined
tailings
Figure 24.13 Final flotation flowsheet with points and levels of reagent additions.
References
173
Table 24.16
Overall metallurgical results obtained on the Mount Weld ore
Product
Weight (%)
% Monazite assay
% Monazite recovery
Cleaner concentrate
Combined tail
Slimes
Feed
20.89
54.51
24.6
100.00
58.5
2.55
8.8
15.8
77.5
8.8
13.7
100.0
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Research Institute of Mineral Raw Materials, Moscow, 1959.
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pp. 336–370, 1987.
3. Bulatovic, S, US Patent 4,772,238, Froth flotation of bastnaesite, September 20, 1988.
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Investigation, 1990.
5. Bulatovic, S., Process Development for Beneficiation of Barite, Fluorite, Bastnaesite Ore from
the Dong Pao Deposit, Vietnam, Report of Investigation, 1995.
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Gosudarstvenie Naucno-tehnicheskie Lzdatelstro Nanche Literature Moskra, pp. 330–380, 1963.
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Investigation, April 2002.
8. Viswanathan, K.V., Madhavan, T.R., and Majumdar, K.K., Selective Flotation of Beach Sand
Monazite, Mining Magazine, Vol. 13, No. 1, 1965.
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Sulphonate Collector, Egypt Journal of Chemistry, Vol. 1, p. 2363, 1958.
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