Flotation of REO Minerals

– 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. The cerium group of REOEs, in which loparit, bastnaesite, parisit, monazite, eshipit and ortit are included.

2. 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

REO

Table 24.1

minerals of economic

value

Mineral Formula Relative REOE content

Monazite

Bastnaesite

Xenotime

Parasite

Yttrocerite

Gadolinite

Ortit

Loparit

Esxenit

Fergusonite

Samarskit

Priorit

Eschynite

(Ce,La…)PO4

(Ce,La,Pr)[CO3]F

YPO4

Ca(Ce,La…)2[CO3]3F2

(Ca,Y,Ce,Er)F2-3H2O

(Y,Ce2)Fe,BeSi2O10

(Ca,Ce)2(Al,Fe)3SiO2[O,OH]

(Na,Ca,Ce,Sr)2(Ti,Ta,Nb)2O6

(Y,Ce,Ca,U,Th)(Ti,Nb,Ta)2O6

(Y,Sr,Ce,U)(Nb,Ta,Ti)O4

(Y,Er,U,Ce,Th)4(Nb,Ta)6O21

(Y,Er,Ca,Th)(Ti,Nb)2O6

(Ce,Ca,Th)(Ti,Nb)2O6

50–68% (Ca,La…)2O3, 22–31% P2O5, 4–12% ThO2, �7% ZrO2, �6% SiO2

36–40% Ce2O3, 36% (La…Pr)2O3, 19–20% CO3, 6–8% F

52–62% Y2O3, Ce, Er as impurities, Th, �5% U, 3% ZrO2 �, 9% SiO2

11% CaO, 26–31% Ce2O3, 27–30% (La,Nd)2O3, 24% CO2, 6% F

19–32% Ca, 8–11% Ce, 14–37% Y, 37–42% F

10–13% FeO, 30–46% YO3, 25% SiO2, 5% (Ce,La…)2O2, 9–10% BeO

6% Ce2O3, 7%(La…)O3, 4% BeO, 8% Y2O3

39–40% TiO2, 34% (Ce,La…)2O3, 8–11% (Ta,Nb)2O5,

5% CaO, Cr,Th as

impurities

18–28% (Y,Er)2O3, 0.2–3% (CeLa…)2O3, 16–30%

TiO2, 4–47% Nb2O5,

1.3–33% Ta2O5, 0.4–12% U3O8

46–57% (Nb,Ta)2O5, 31–42% Y2O3, 14% Er2O3, 1–4% ThO2, 1–6% UO2

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

21–28% (Y,Er)2O3, 3–4% Ce2O3, 21–34% TiO2, 15–36% Nb2O5, 0.6–7%

ThO2, 0–5% UO2

15–19% Ce2O3, 0.9–4.5% (Y,Er)2O3, 21–24% TiO2, 23–32% Nb2O5, 0–7%

Ta2O5, 11–17% ThO2

4.9

4.5

4.6

4.3

3.8

4–4.5

4.8

4.9

5.6-6.2

5.6–5.8

7.8–5

5.5

4.5

4.5

4.5

4.5

6.5–7

6

5.5

5.5–6.5

5–6

5.6

152 24.

Flotation of R

EO

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 nepheline-containing 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 FLOTATION PROPERTIES OF CERIUM GROUP OF REOE MINERALS

24.2.1 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 difficulties 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

80

60

40

Zircon 20

Pyrochlore 0

Rec

over

y (%

)

4 6 8 10 12Flotation pH

Figure 24.1 Effect of pH on flotation of monazite, zircon and pyrochlore.

O

R S R

O

154 24. Flotation of REO Minerals

Rec

over

y (%

)

100

80

60

40

20

0

ZirconPyrochlore

Monazite

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Na2S addition (g/t)

Figure 24.2 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.

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.


10 20 30 40 50 60 70 Concentrate grade (% REO)

0

20

40

60

80

100

RE

O r

ecov

ery

(%)

Heated to 40°C

Heated, ambient 85°C

Unheated to 18°C

Figure 24.3 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 Weight (%) Total % REO assays % REO recovery

Tall oil fatty acid REO concentrate 10.77 48.5 73.8 REO combined tail 89.23 2.07 26.2 Feed 100.00 7.08 100.0

Tall oil modified with REO concentrate 10.59 60.1 90.5 Secondary amine REO combined tail 89.41 0.74 9.5 (amine acetate) Feed 100.00 7.02 100.0 Tall oil modified with REO concentrate 10.45 62.2 92.3 Petroleum sulphonate REO combined tail 89.55 0.61 7.7

Feed 100.00 7.05 100.0

24.2.2 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


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

Slimes Slimes

Sand

Total

Desliming 1

Conditioning 1

Grinding Desliming 2

Conditioning 2

Y2O3/REO rougher

Y2O3/REO scavenger

Conditioning

Y2O3/REO 1st cleaner

Conditioning

Y2O3/REO 3rd cleaner

Y2O3/REO 4th cleaner

Y2O3/REO 2nd cleaner

Y2O3/REO cleaner scavenger

Y2O3/REO scalper

Y2O3/REO concentrate tailings

Figure 24.4 Generalized flowsheet for beneficiation of yttrium group of minerals using flotation.

CH (CH2)3 CH CH2 CH CH2OH

C2H2 C2H5

100

Collector KBX3

80

FA3 fatty acid

60

Sodium oleate 40

20

0

RE

O r

ecov

ery

(%)

0 100 200 300 400 500 600

Collector addition (g/t)


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:

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.

Figure 24.5 Effect of different collectors on REO recovery from complex REO–ZrO2 ores.


RE

O r

ecov

ery

(%)

100

80

60

40

20

0 0 20 40 60 80 100

Zircon recovery (%)

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 FLOTATION PRACTICES AND RESEARCH WORK ON BENEFICIATION OF REO MINERALS

24.3.1 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 159

24.3.2 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.


Feed ore

Thermal conditioning

Rougher Scavenger

1st cleaner

2nd cleaner


Na2SiF6

Collector

Na2CO3

Weslig

1st cleaner scavenger

3rd cleaner

Collector


Weslig

Na2SiF6

Conditioning

Collector

Weslig

Weslig

Concentrate Tailings

Figure 24.7 Mountain Pass (USA) plant flowsheet.


Table 24.3

Reagent scheme used at the Mountain Pass concentrator

Reagent Additions (g/t)

Soda ash (Na2CO3) 3000–4500 Sodium fluorosilicate (Na2SiF6) 300–600 Lignin sulphonate (Weslig) 2400–3500 Tall oil fatty acid (P25A) 200–400

Table 24.4

Molycorp plant metallurgical results

Product Weight (%) Assays (%) % Distribution

REO Ce2O3 La2O3 BaSO4 CaO REO Ce2O3

Final bastnaesite concentrate Final bastnaesite tailing Feed

9.38 90.62 100.00

64.1 2.28 8.09

31.4 1.06 3.9

22.2 0.74 2.76

2.7 26.3 26.3

3.1 16.9 15.6

75.6 24.4 100.0

75.5 24.5 100.0

Table 24.5

Distribution of the REO in the Mountain Pass concentrate

Element % of Total REO content Element % of Total REO content

Lanthanum 33.2 Dysprosium 0.0312 Cerium 49.1 Holmium 0.0051 Praseodymium 4.34 Erbium 0.0035 Neodymium 12.0 Thulium 0.0009 Samarium 0.790 Ytterbium 0.0006 Europium 0.118 Lutetium 0.0001 Gadolinium 0.166 Yttrium 0.0913 Terbium 0.0159

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).


Table 24.6

Chemical analyses of the Dong Pao ore

Element Assays (%)

Total REO 8.72 Cerium (Ce2O3) 3.76 Lanthanum (La2O3) 3.18 Barite (BaSO4) 62.5 Fluorite (CaF2) 5.54 Silica (SiO2) 8.85 Alumina (Al2O3) 0.97 Iron (Fe2O3) 2.69 Calcium (CaO) 0.15 Sodium (Na2O) 0.54 Potassium (K2O) 0.11 Titanium (TiO2) 0.09 Phosphorus (P2O5) 0.13 Manganese (MnO) 0.64 Chromium (Cr2O3) 0.22 Vanadium (V2O5) 0.03 LOI 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 contained 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.


Feed

CaF2 concentrate

BaSO4 concentrate

REO tailings

Conditioning

Grinding Conditioning

BaSO4 rougher BaSO4 scavenger

BaSO4 1st cleaner

BaSO4 1st cleaner

scavenger

BaSO4 2nd cleaner

BaSO4 3rd cleaner

BaSO4 4th cleaner

CaF2 rougher CaF2 scavenger

CaF2 1st cleaner

CaF2 2nd cleaner

CaF2 3rd cleaner

REO rougher REO scavenger

REO 1st cleaner

REO 2nd cleaner

REO 3rd cleaner



Thermal conditioning (75°C)

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


Table 24.7

Reagent scheme developed for beneficiation of the Dong Pao ore

Reagent Additions (g/t)

BaSO4 circuit CaF2 circuit REO circuit

Ro Cl Ro Cl Ro Cl

Depressants and modifiers Na2SiO3 2500 1200 1500 1100 – – BaCl2 500 400 – – – – NaF – – 300 400 – – Al2(SO4)3 – – 600 400 – – MESB – – 20 200 – – Na2CO3 – – – – 4000 1400 Citric acid – – – – 1000 3500 MM4 – – – – 1000 1300 Collectors SR82 850 – – – – – AKF2 – – 300 – – – KV3 – – – – 900 200 Fuel oil – – – – 200 –

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 Weight (%) Assays (%) % Distribution

BaSO4 CaF2 REO BaSO4 CaF2 REO

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)

62.83 7.36

13.72 16.09 100.00 62.83 7.36

12.97 16.84 100.00

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


24.3.3 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 preconcentration–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 Flotation Monazite concentrate Monazite tailings additions (kg/t) pH

Na2SiO3 NaOH Weight % Grade % Recovery Weight % Grade % Recovery (%) (%)

1 2.2 9.2 3.2 23.9 13.3 96.8 2.54 33.7 3 3.0 9.4 10.4 33.3 37.5 89.6 0.95 62.5 5 5.5 9.6 8.3 66.2 88.4 91.7 0.28 11.6 7 6.5 9.7 6.6 76.2 92.3 93.4 0.24 8.3 9 9.0 9.8 5.6 84.4 85.7 94.4 0.24 5.6 11 8.5 9.8 4.8 94.3 83.6 95.2 0.40 4.8


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 11.4 5.0 21.4 20.0 95.0 4.6 80.0 Sodium oleate 5.5 8.3 66.2 88.4 91.7 0.28 11.6 Neofat 140 5.5 9.0 57.0 89.0 91.0 0.12 11.0 Acintol FA1 5.0 6.1 75.5 86.4 93.9 0.23 13.6 Acintol FA2 5.0 5.6 81.6 89.2 94.4 0.16 10.8 Acintol FAX 5.0 5.8 71.0 77.0 94.2 0.16 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 test-work 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 minerals 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) 13.35 Titanium (TiO2) 25.8 Calcium (CaO) 2.71 Magnesium (MgO) 1.75 Zircon (ZrO2) 3.72 Manganese (MnO) 2.82 Iron (Fe2O3) 39.84 Alumina (Al2O3) 9.24 Sodium (Na2O) 0.21 Potassium (K2O) 0.02 Phosphorus (P2O5) 0.10 Monazite (REO) 2.20


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 approximately 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 231 900 91.0 90.9 Aeropromoter 710 4000 92.1 98.5 R260 600 85.1 96.5 R376 650 90.5 85.0 R276R 700 85.5 90.5 R376 900 90.2 93.3


Mon

azite

rec

over

y (%

)

100

80

60

40

20

0

R260H

R276F

R231

Collector

0 1 2 3 4 5 6 7 Conditioning time (min)

Figure 24.9 Effect of conditioning time with sodium oxalate on monazite recovery using different collectors.

Table 24.13

Effect of different collectors on monazite flotation using Brazilian beach sand

Reagents Product Weight (%) Assays (%) % Distribution

RE2O3 RE2O3

Hydroxamate = 140 g/t Na2SiO3 = 1200 g/t

Sodium oleate = 525 g/t Na2SiO3 = 1398 g/t

Feed Rougher Rougher Feed Rougher Rougher

Conc Tail

Conc Tail

100.00 4.90 95.10

100.00 5.66 94.34

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.


Table 24.14

Head analyses of the Mount Weld ore

Element Assays (%)

Total REO 15.50 Cerium (Ce2O3) 9.54 Lanthanum (La2O3) 4.21 Samarium (Sm2O3) 0.39 Yttrium (Y2O3) 0.30 Iron (Fe2O3) 60.5 Alumina (Al2O3) 15.5 Magnesia (MgO) 4.60 Calcium (CaO) 10.8 Phosphorus (P2O5) 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.

50

40

30

20

10

0

Mon

azite

rec

over

y in

slim

es (

%)

2 4 6 8 10 12 14Desliming size K80 (µm)

Figure 24.10 Effect of desliming size on monazite losses in the slime fraction using dispersant DQ4.

100

4 kg/t

80 2 kg/t

60 0 kg/t

40

20

0

Mon

azite

rec

over

y (%

)

0 10 20 30 40 50 60 Monazite concentrate grade (% REO)


Table 24.15

Effect of different dispersants from the DQ series on monazite loss in the slime fraction

Desliming size Dispersant Slime fraction (µm)

Type Additions Weight % Monazite % Monazite (g/t) (%) assay recovery

4 None – 25.0 17.8 28.7 4.2 DQ2 800 23.3 15.6 23.4 4.1 DQ3 800 23.1 13.3 19.8 4.0 DQ4 800 21.5 9.4 13.0 4.3 DQ6 800 22.2 12.0 17.1 4.0 DQ8 800 23.4 11.8 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.

Figure 24.11 Effect of Na2S on the monazite rade–recovery relationship.

Feed

Coarse

Fines Fines

DQ4 300 g/t

to flotation

Washing

Scrubbing

Grinding

Conditioning

Final slito tailing

Cyclones


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).

mes s

Figure 24.12 Final grinding and desliming flowsheet.


Ground deslimed ore

REO

100 g/t DA663

Conditioning 1

REO 1st cleaner

REO 2nd cleaner

Conditioning

Conditioning

1000 g/t Na2SiO3

600 g/t Na2CO3

Conditioning 2

500 g/t dextrose/quebracho 600 g/t collector CB110

2000 g/t Na2S

Conditioning 3

REO rougher REO scavenger

200 g/t collector CB110

200 g/t dextrose/quebracho

1000 g/t Na2S

200 g/t collector CB110

REO 1st cleaner scavenger

200 g/t dextrose/quebracho 2000 g/t Na2S

200 g/t dextrose/quebracho 100 g/t Na2S

REO 3rd cleaner

Conditioning

REO cleaner combined concentrate 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

REFERENCES

1. Ginsburg, I.E., Zuravleva, L.N., and Ivanov, E.B., Rare Earth Elements and their Origin, USSR Research Institute of Mineral Raw Materials, Moscow, 1959.

2. Polkin, C.I., Beneficiation of Precious Metals and Rare Mineral Ores, Publisher Nedra, Moscow, pp. 336–370, 1987.

3. Bulatovic, S, US Patent 4,772,238, Froth flotation of bastnaesite, September 20, 1988. 4. Bulatovic, S., Process Development for Beneficiation of Mount Weld REO Ore, Report of

Investigation, 1990. 5. Bulatovic, S., Process Development for Beneficiation of Barite, Fluorite, Bastnaesite Ore from

the Dong Pao Deposit, Vietnam, Report of Investigation, 1995. 6. Fishman, M.A., Sobolev, D.C., Practices in Beneficiation of Sulphide and Rare Metals, vol. V,

Gosudarstvenie Naucno-tehnicheskie Lzdatelstro Nanche Literature Moskra, pp. 330–380, 1963. 7. Bulatovic, S., Process Development for Beneficiation of the Dong Pao Ore (Vietnam), Report of

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. 9. Farah, M.Y., and Fayed, L.A., Oxalate Activation in the Flotation of Monazite by Heavy

Sulphonate Collector, Egypt Journal of Chemistry, Vol. 1, p. 2363, 1958. 10. Pavez, O., and Perez, A.E.C., Bench Scale Flotation of Brazilian Monazite, Mineral Engineering,

Vol. 7, No. 12, pp. 1561–1564, 1994. 11. Plaksin, I.N., Study of Superficial Layers of Flotation Reagents on Minerals and the Influence of

the Structure of Minerals on their Interactions with Minerals, International Mineral Processing Congress, paper #13, London, 1960.

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Flotation of REO Minerals