WO1991016986A1

WO1991016986A1 - A monazite beneficiation process

Info

Publication number: WO1991016986A1
Application number: PCT/AU1991/000011
Authority: WO
Inventors: Srdjan Bulatovic; Graham C. Willett
Original assignee: CARR BOYD MINERALS Ltd
Current assignee: CARR BOYD MINERALS Ltd
Priority date: 1990-05-10
Filing date: 1991-01-11
Publication date: 1991-11-14
Anticipated expiration: 1992-11-10

Abstract

A collector agent for the froth flotation of rare earth minerals is disclosed. The collector agent is an emulsion which comprises a fatty acid, an emulsifier and a phosphonic acid derivative or salt thereof. An oil and/or an amine may be included in the emulsion. To prepare the collector agent, the components are formed into an emulsion and subsequently oxidized until homogeneous. The oxidation may be performed by heating the emulsion in air at a temprature of at least 60 °C. A process for the froth flotation of rare earth minerals using this collector agent is also disclosed.

Description

A MONAZITE BENEFICIATION PROCESS FIELD OF THE INVENTION This invention relates to the separation of oxidic minerals by froth flotation, more specifically to a flotation separation process for the recovery of rare earth minerals, particularly monazite from complex and refractory ores and concentrates.

BACKGROUND ART Monazite is a rare earth containing mineral comprising phosphates of the cerium group of rare earth metals (lanthanides) in a complex oxidized ore. Monazite may also contain yttrium group compounds.

Monazite is found in several continents, such as Australia, Africa, and in North and South America, usually in complex disseminated ores, accompanied by other valuable minerals containing yttrium, niobium, titanium, zirconium and thorium. A typical monazite would have the following composition with respect to its rare earth metal oxide content: Weight percent

Lanthanum oxide La2^3 14-37

Cerium oxide Cβ2θ3 37-46

Praseodymium oxide ^203 4-6

Neody ium oxide Nd2U3 10-25 Samarium oxide Sπi2θ3 3-11

Europium oxide EU2O3 0-0.2

Gadolinium oxide Gd203 0-0.1

Terbium oxide ^2^3 0-0.1

Dysprosium oxide ^>Y2 - 3 0.1-0.5 Yttrium oxide Y2O3 5-6

These oxides are sometimes referred to as members of the lanchanide group named after the first member of the grcup. For the sake of clarity, it should be stated that yttrium (Periodic Table No. 39) is not a member of the iinthanide group (Periodic table No. 58-71), but it is sometimes loosely referred to as one of the rare earth metals.

Other rare earth minerals falling within the scope of this invention include, xenoti e, churchite, rhabdophane, cheralite, cerianite, florencite, and bastnaesite.

In addition, secondary non-rare earth minerals such as apatite, crandallite and goethite carrying minor amounts of rare earth minerals fall within the scope of the present invention. Although the present invention relates to the recovery of all the aforementioned rare earth minerals, for the purposes of describing the invention, reference will be made primarily to monazite only.

The variations in the composition of monazite will influence the degree of beneficiation that may be attained by the mineral separation process.

Beneficiation of an ore usually includes several different process steps with the ultimate aim of obtaining a concentrate of the valuable component of the ore, or if there are more than one such component, to obtain the appropriate number of concentrates. Froth flotation is a process step often used to separate the wanted components from the unwanted components of the ore. Froth flotation is usually preceded by an ore conditioning step, in which various conditioning agents are added to the ore slurry. Conditioning agents include pH modifiers, activators, regulators, depressants, collectors, frothers and the like, and are generally used for the purpose of conditioning the surface of the ore particles. The slurry of the conditioned ore is then subjected to aeration, resulting in air bubbles attaching themselves to the surface of certain ore particles which then rise to the top of the slurry, while other ore particles sink to the bottom. The role of the collector agent is to render the surface of the valuable component containing particles hydrophobic, thereby allowing air bubbles to adhere to these particles. These particles are subsequently separated in the froth. In contrast, a depressant agent renders the surface of the unwanted ore particles wettable (hydrophillic) . The object of the froth flotation step is to obtain a froth substantially enriched by the value minerals of the ore, and at the same time depressing the unwanted mineral components into the tailing. It should be noted that the depressed ore fraction may contain other value minerals which may be recovered by subsequent flotation steps utilizing other flotation agents.

Anionic and cationic surface activators are often used as collectors in the flotation of non-sulphidic ores. Such collectors are intended to be selectively adsorbed on the surface of the value minerals in order to obtain higher selectivity in the flotation stage.

Monazite may be present in beach sand deposits found in India and Australia and vein-type ores found in South Africa and Brazil. The concentration of monazite found in beach sand and vein-type ores, is achieved by using conventional techniques such as gravity separation, magnetic and electrostatic separation, or froth flotation. A typical process described for the beneficiation of monazite found in vein-type deposits, is described in US patent 2,610,738.

There are known processes for the selective froth flotation of monazite in ores which contain rare earth metal oxides and associated minerals such as rutile, garnet, silimanite, calcite, quartz, etc. In conventional froth flotation of monazite, fatty acid type collectors which are predominantly composed of oleic acid, are used.

Monazite contained in complex ores, for example pegmatites, magmatites and carbonates, are likely to yield low grade concentrates when treated with conventional reagents utilized in the mineral separation of monazite contained in ores having simple gangue composition. More selective reagents are required in the separation of rare earth metal oxides contained in complex ores. For instance, a process for the separation of bastnaesite, which is a rare earth metal compound with a fluorcarbonate structure, is described in U.S. patent 4,772,382. The process of U.S. patent 4,772,382 utilizes a collector emulsion based on sulphonated fatty acids, petroleum sulphonate and a primary amine. Iron oxides such as goethite, hematite, and siderite are especially detrimental to froth flotation separation when they are present in ores containing monazite. Such iron oxide bearing compounds would normally float together with the rare earth minerals, when using conventional froth flotation agents.

DISCLOSURE OF THE INVENTION A new collector agent has been found for the satisfactory froth flotation separation of rare earth minerals particularly when they are finely disseminated in an ore having complex gangue compositions.

Accordingly in a first aspect, the present invention consists in a collector agent for the froth flotation separation of rare earth minerals in an ore. comprising a composition formed by preparing an emulsion of: a fatty acid; an emulsifier; a phosphonic acid derivative or sa ϊ: thereof; optionally an oil and/or an amine; and subsequently oxidizing the e ulsi r. until it becomes homogenized.

In a second aspect, the present invention further consists in a process for the beneficiation. of rare earth minerals contained in an ore or concentrate comprising the steps of: (a) forming the ore or concentrate into an aqueous slurry; (b) adding to said slurry a collector agent formed by preparing an emulsion of

(i) a fatty acid, (ii) an emulsifier, (iϋ) a phosphonic acid derivative or a salt thereof, and, optionally an oil and/or an amine, then oxidizing the emulsion until said emulsion becomes homogenized,

(c) subjecting said emulsion containing slurry to froth flotation; and

(d) separating a froth containing rare earth minerals and a tailing comprising unwanted minerals. Desirably, an oil, preferably a non polar lower carbon chain oil will be included in the emulsion. This oil serves to stabilize the froth and increase cleaning efficiency without necessarily increasing rougher recoveries.

The collector agent is added to the slurry of the ground ore, which has been conditioned with conventional conditioning agents. The conditioned slurry containing the collector agent is then subjected to a froth flotation process step yielding ?. froth in which the rare earth mineral is concentrated.

If yttrium minerals are also present in the rare earth minerals together with other rare earth metal compounds, these will also report to the froth.

The preferred embodiment of this invention will now be described in detail, as part of an ore beneficiation process and illustrated by way of examples. Figure 1 show?; a schematic flowsheet for a monazite ore beneficiation process utilising the present invention. The complex ore, containing monazite accompanied by gangue comprising carbonates, iron oxides, silicates, alumino-silicates, manganese or similar compounds, is ground to a suitable liberation size. The monazite in such ores may contain cerium group rare earth metal oxides, but also members of the yttrium metals such as yttrium, niobium, titanium, zirconium and in some cases, thorium compounds. In the case of finely disseminated ores, the fineness of grind required may be of a particle size range which is at least 80% smaller than 37 urn. Some complex ores also contain clay and similar slimes, and in such instances it is preferable that these be removed by desliming before grinding. A second desliming step is often applied after grinding. Grinding may either be wet or dry grinding. The deslimed ground ore is mixed with water and made into an aqueous slurry. The ore slurry is subsequently conditioned with the addition of various conditioning agents, including pH modifiers, depressants and the like. A satisfactory depressant and pH modifier to be used in the present process is sodium sulphide (Na₂S.9H₂0).

An effective depressant in the preferred embodiment of this invention, to be used in conjunction with sodium sulphide, is a mixture of dextrin and carboxymethyl cellulose, used together with mercapto-acetic acid as a stabilizer. In the treatment of some monazite bearing ores an anionic acrylic acid homopolymer may be added at a subsequent stage of conditioning. Dextrin is a known polysaccharide having the general formula of (C6Hκ)θ5)_n. For best results a depressant mixture of dextrin, carboxymethylcelluloεe and mercapto-acetic acid is made up, combining them in the following ratio: dextrin:carboxymethyl cellulose:mercapto-acetic acid = 60:40:10. In instances when the ore to be beneficiated is high in limonite and carbonate-containing minerals, an anionic acrylic acid homopolymer is added as an additional depressant. Each of the above reagents is add d in a separate conditioning stage with approximately 10 minutes agitation after each addition.

It is to be pointed out that the use of sodium sulphide as a pH modifier and depressant, and mixtures of dextrin, carboxylmethyl cellulose and mercapto-acetic acid, with or without acrylic acid homopolymer, are merely the preferred conditioning agents, but they are by no means essential for the practice of the present invention. Other suitable pH modifiers, activators and depressants may be substituted in the conditioning of the monazite-containing ore. Furthermore, the choice of depressants and modifiers depends on the gangue composition of the ore to be treated.

The novel collector agent of this invention has a fatty acid base. A convenient source of fatty acids is tall oil, the fatty acids of which have the general formula C17H31.35 COOH, and are composed of long chain saturated or unsaturated mono-carboxylic acids. One fatty acid that has been found to be effective in this invention is oleic acid.

Preferably, fatty acid is present in the collector in a concentration of 48-62 weight percent.

The fatty acid in the collector is emulsified by the presence of a suitable emulsifier and a phosphonic acid derivative or salt thereof. Suitable emulsifiers have been found to be sodium oleate and a secondary amine modified sulfonated fatty acid, having branched or straight aliphatic chains containing 15-19 carbon atoms. An example of this latter compound is sold under the trade name Lilaflot 0S100 by KenoGard AB of Sweden.

Typically, the concentration of the emulsifier will be 14-22 weight percent.

A variety of phosphonic acid derivative or salts thereof may be used. The present inventors have found that Na-2-ethylhexylimino-bis-methylenephosphonate is useful as are styrenephosphonic acid and benzylphosphonic acid. The former compound is available from Albright & Wilson Ltd under the trademark BRIQUEST 281-25S.

Typically, the concentration of phosphonic acid derivative or salt thereof will be 14-22 weight percent. Although not an essential part of the collector composition of the invention, an oil can be included to stabilize the froth and promote cleaning efficiency. The oil will typically be included in the collector in a concentration of 8-12 weight percent.

Preferably, the oil will be a non polar lower carbon chain oil, examples being fuel oil and pine oil. in order to improve the dispersion and reaction between the fatty acid and phosphonic acid derivative or salt thereof, a primary amine may be included in the emulsion prior to oxidation. Typically the amine would be added at a concentration of 10% w/w with respect to the emulsion. An example of a suitable amine is Amine D which is a rosin amine available from Hercules Inc, USA. The principle component of Amine D is dehydroabietylamine.

The emulsion of the above composition is subsequently oxidized. This oxidation may be conducted by passing an oxygen-containing gas, such as air or pure oxygen through the emulsion, until the solution is clarified. The oxidized emulsion is added in the preferred embodiment, to the conditioned ore slurry. The rate of the collector addition depends on the amount of slimes and complex iron bearing compounds present in the ore, and for best results, it is added in amounts varying from 600 g/t to 2000 g/t of ore.

Conditioning with the oxidized collector is followed by conventional rougher and cleaner flotation stages, which are usually part of a conventional flotation process. It is customary to subject the collector conditioned slurry to froth flotation process for about 7-15 minutes, without further reagent additions. A relatively low grade rougher concentrate is conventionally upgraded by cleaning process steps with further additions of depressants. The depressant mixtures used in the preferred embodiment are known to be effective in depressing iron oxides, aluminium silicates, manganese and iron carbonates. These depressants, used together with the oxidized collector emulsion of the present invention, have been found to enhance the selectivity of the collector emulsion and also to improve the grade of the monazite concentrate.

MODES FOR CARRYING OUT THE INVENTION The improvements achieved in the separation of monazite contained in complex oxidic ores will be greater understood by those skilled in the art by having regard to the following examples, which illustrate the method of the present invention in a quantitative manner. The examples show the application of the method described to the beneficiation of monazite contained in complex ores.

EXAMPLE 1

Laboratory froth flotation separation steps were carried out on a high grade monazite containing ore utilizing conventional reagents. The ore was of a complex nature containing iron oxides, clay, apatite and manganese as main gangue minerals. The ore also contained small quantities of the yttrium group minerals.

The ore was scrubbed by conventional methods and deslimed to remove the bulk of the clay and limonite containing minerals, followed by grinding to 325 Tyler mesh nominal size. The ground ore was deslimed a second time to remove secondary slimes. The slurry of the ore was conditioned in the presence of sodium carbonate as a pH modifier, and sodium-silicate and starch were used as depressants. High purity oleic acid acted as a collector agent. The above reagents were added at the following rate:

Sodium carbonate, Na2Cθ3: 2000 g/t Sodium silicate (N-Brand) : 900 g/t

Causticized starch: 1300 g/t

High purity oleic acid: 2000 g/t The results of the froth flotation separation tests are shown in Table 1 below:

T A B L E

Product Weight Assays X 7. Distribution %

^Y2°3 La₂0₃ Sm₂0₃ ^Y2°3 La₂0₃ Sm₂0₃

Cleaner Concentrate 19.59

Cleaner Tailing 7.95

Rougher Tailing 47.31

Primary Slime 15.54

Secondary Slime 9.60

FEED 100.00 0.14 7.48 0.82 100.0 100.0 100.0

It can be seen that unsatisfactory separation of the monazite occurred using conventional reagents in the above froth flotation separation process.

EXAMPLE 2 In another laboratory froth flotation separation test for the same ore as in Example 1, a combination of conventional collectors, oleic acid and a sulphonate, were used.

The depressants in conditioning the ground ore were similar to those in Example 1. The reagents were added in the following quantities:

Sodium carbonate, Na2C03: 2000 g/t

Sodium silicate (N-Brand): 900 g/t

Cauεticized starch: 1300 g/t Sulphonate (R-840 Cyanamid Brand): 1000 g/t High purity oleic acid: 2000 g/t

The results of the froth flotation separation test utilizing the above conditioners and collectors are shown in Table 2.

T A B L E

Produc t Weight Assays % % Distribution %

La₂0₃ Sm₂0₃ La₂0₃ Sm₂0₃

^Y2°3 ^Y2°3

Cleaner Concentrate Cleaner Tailing Rougher Tailing Primary Slime H > Secondary Slime

FEED 100.00 0.13 7.34 0.78 100.0 100.0 100.0

It can be seen that using a relatively high concentration of combined collector agents did not improve notably the separation of monazite from the unwanted ore components. EXAMPLE 3

Laboratory froth flotation separation tests were conducted on the same ore as that used in Example 1 and Example 2, utilizing other commercially available conditioning agents and the emulsion of the present invention. The emulsion of the present invention is denoted as Collector CB110.

The composition of CB110 was: oleic acid 60% w/w

Lilaflot 0S100 15% w/w Briquest 281-25S 15% w/w pine oil 10% w/w

This composition was prepared by mixing the components and then oxidizing in air at 75°C for 1 hour. The ground and deslimed ore pulp was made into an aqueous slurry and conditioned with sodium sulphide pH modifier, and the depressant mixture composed of dextrin/carboxymethyl cellulose/mercapto acetic acid, in the proportions described hereinabove. The conditioned ore was then subjected to froth flotation separation in the presence of CB110 collector.

The following quantities were used in the froth flotation test:

Sodium sulphide, (Na2S.9H₂0): 5000 g/t

Dextrin/carboxymethyl cellulose/ mercapto-acetic acid: 2000 g/t

Arcylic polymer (commercially available as DA663): 500 g/t

Collector CB110: 2000 g/t

The froth flotation results showing the concentration and distribution of major constituents of the monazite present in the ore, are shown in Table 3. T A B L E

Product Weight Assays X X Distribution X

^Y2°3 a₂0₃ Sm₂0₃ Fe Total ^Y2°3 La₂0₃ Sm₂0₃ Fe Total

Cleaner Concentrate Rougher Concentrate Rougher Tailing Primary Slime Secondary Slime

HEAD 100.00 0.11 6.40 0.52 22.3 100.0 100.0 100.0 100.0

A very significant improvement in the flotation separation can be seen by the utilization of the emulsion of the present invention. As can be seen, the distribution percentage of the major constituents of the monazite is between 40.8-48.2%, which translates to over 50% of the rare earth metal oxides being retained in the cleaner concentrate. About 96% of the iron was rejected and the flotation tailing was low in monazite. EXAMPLE 4 Continuous laboratory froth flotation separation tests were carried out on the ore of Examples 1, 2 and 3, making additions of CB110 collector of the present invention to the conditioned ore. The continuous laboratory flotation tests were designed to simulate a commercial continuous circuit. The flowsheet of the continuous separation process is shown in Figure 1.

The reagents used in the continuous laboratory tests were as follows:

Sodium sulphide, (Na2S.9H2θ): 5000 g/t Dextrin/carboxymethyl cellulose/ mercapto-acetic acid: 2000 g/t

Arcylic polymer (DA663): 300-600 g/t

Collector CB110: 2000 g/t

The results of the test are shown in Table 4. REO in the first column denotes yttrium and rare earth metal oxides.

The rate of the acrylic polymer addition was varied, in order to optimize conditions for the iron oxide rejection. T A B L E

Product Weight Assays X X Distribution X

^Y2°3 ^La2°3 Sm₂0₃ Fe Sm₂0₃ Fe Total ^Y2°3 ^La2°3 Total

REO Cleaner Cone 30.04 0.21 14.3 1.20

REO Combined Tail 46.09 0.035 2.09 0.15

Primary Slimes (1) 18.17 0.06 3.70 0.29

Secondary Slimes (2) 5.70 0.09 5.54 0.41

HEAD (Calc) 100.00 0.10 6.25 0.51 22.25 100.0 100.0 100.0 100.0

REO Cleaner Cone 29.50 0.21 14.58 1.28

REO Combined Tail 42.39 0.039 2.19 0.14

Primary Slimes (1) 16.38 0.05 3.31 0.28

Secondary Slimes (2) 11.73 0.09 5.41 0.41

HEAD (Calc) 100.00 0.10 6.41 0.53 22.20 100.0 100.0 100.0 100.0

REO Cleaner Cone 30.90 0.21 14.3 1.29

REO Combined Tail 43.16 0.048 2.83 0.19

Primary Slimes (1) 14.27 0.046 3.49 0.29

Secondary Slimes (2) 11.67 0.079 5.65 0.44

HEAD (Calc) 100.00 0.10 6.80 0.57 22.30 100.0 100.0 100.0 100.0

It can be seen that the distribution of yttrium and major rare earth metal oxide constituents of the monazite contained in the ore is well in excess of 50% in the monazite cleaner concentrate.

Typical compositions of the monazite concentrate, with respect to the rare earth metal oxides present in two separate concentrate samples obtained in the above continuous laboratory tests, are shown in Table 5. T A B L E 5

Element Concentrate 1 Concentrate 2

Cerium (Ce₂θ3) Samarium (Sm₂θ3) Lanthanum ( a₂θ3) Praseodymium Pr θ3) Neodymium (Nd₂θ3) Europium (E 2O3) Gadolinium (Gd2θ3) Terbium ( b₂θ3)

Dysprosium (Dy₂θ3) Holmium (H02O3) Erbium (Er₂θ3) Thulium ( m₂θ3) Ytterbium (Yb₂θ3) Lutetium (Lu₂θ3)

It is clearly demonstrated that the process described hereinabove gives very good separation of monazite from complex ores, and that such separation is not attainable by using conventional flotation reagents. EXAMPLE 5

Laboratory froth flotation separation tests were performed on an ore containing higher concentrations of the yttrium group metals. The conditions and conditioning agents added were similar to those described in Examples 3 and 4. The ore of Example 5 had relatively high yttrium content and was relatively low in monazite.

The rate of reagent additions were as follows: Sodium sulphide, (Na₂S.9H₂0): 5000 g/t Dextrin/carboxymethyl cellulose/ mercapto-acetic acid: 2000 g/t

Arcylic polymer (DA663): 400 g/t

Collector CB110: 2000 g/t

The results of the froth flotation separation are shown in Table 6.

Product Weight Assays X X Distribution X

^Y2°3 ^La2°3 ^Sm2°3 Fe Total ^Y2°3 ^La2°3 Sm₂0₃ Fe Total

3rd Cleaner Cone Rougher Cone Rougher Tail Secondary Slime Primary Slime

HEAD (Calc) 100.00 1.80 3.62 0.52 19.9 100.0 100.0 100.0 100.0

4th Cleaner Cone Rougher Cone Rougher Tail Secondary Slime Primary Slime

HEAD (Calc) 100.00 1.77 3.74 0.69 20.0 100.0 100.0 100.0 100.0

The results of the above tests clearly show that the present process is capable of recovering yttrium minerals in particular in the form of churchite and xenotime.

It has been found that a collector of the invention that includes benzylphosphonic acid in place of Briquest 281-25S is advantageous for use in high content yttrium, high content iron and low content monazite ores.

The examples that follow illustrate the use of these collectors. Note that each of the collectors was prepared by mixing the components, adding 10% of Amine D and then oxidizing in air at 75°C for 2 hours.

EXAMPLE 6

Laboratory froth flotation separation tests were performed on an ore of the type used in Example 5. Six tests were performed using various collector compositions as set out below.

Comj>os i_t J. on _i_X __ /__"

Test No. Collector Olei c Aci d Sod i.um_01ea_t e £ll2S£hon i. c_Ac i_^d Fuel Oil

Derivative

15 15 Briquest 281-25S 10 15 15 Styrene phosphonic acid 10 15 15 Briquest 301-50A* 10 15 15 Benzyl phosphonic acid 10 10 20 Benzyl phosphonic acid 10

10 30 Benzyl phosphonic acid 10

* ni trilotris(methylenephosphonic) acid

Reagent additions were the same for all tests as follows:

Reagent Additions g/t Rougher Depressants & Modifiers Collector

Sodium sulfide 5000 2000

Acrylic polymer (DA663) 200 * WW82/770 2000

For the cleaners, reagent additions for tests F-17, F-18, F-22 and F-23 are set out below with additions for F-16 and F-13 bracketed. Cleaners

Sodium sulfide 525 (600) 200 (300)

Acrylic polymer (DA663) 300 (375) * WW82/770 525 (600)

*50/50 mixture of wheat dextrin (WW82 supplied by Ogilvie Inc), and

Ambergum 770 (a medium range molecular weight carboxymethylcellulose supplied by Hercules Inc) The pH of the collectors were as follows:

F-13 F-16 F-17 F-18 F-22 F-23

The results of these tests are shown in Table 7 T A B L E

Test No Product Weight Assays % X Distribution X

^Y2°3 ^La2°3 Fe Total ^Y2°3 La₂0₃ Fe Total

F-13

HEAD (Calc) 100.00 0.86 1.55 24.8 100.0 100.0 100.0

F-16

HEAD (Calc) 100.00 0.86 1.54 20.8 100.0 100.0 100.0

TABLE 7 Cont

T A B L E Z iConjtinuedi

Test No Product Weight Assays X X Distribution X

^Y2°3 ^La2°3 Fe Total ^Y2°3 La₂0₃ Fe Total

F-17

HEAD (Calc) 100.00 0.86 1.57 24.7 100.0 100.0 100.0

F-18

HEAD (Calc) 100.00 0.87 1.57 21.4 100.0 100.0 100.0

T A B L E Z_iCon^j.nued

Test No Produc t Weight Assays X X Distribution X

^Y2°3 ^La2°3 Fe Total ^Y2°3 ^La2°3 Fe Total

F-22

HEAD (Calc) 100.00 0.86 1.54 20.2 100.0 100.0 100.0

F-23

HEAD (Calc) 100.00 0.85 1.54 20.8 100.0 100.0 100.0

The results of these tests clearly show good cleaner concentrate recoveries with an improved rejection of iron over the Example 5 results.

Other collectors that have been tested satisfactorily include: -

Com osition % w/w

All of the collectors had 10% Amine D added and were oxidized in air for 2 hours at 75°C.

EXAMPLE 7

The present inventors have also found that substitution of tannic acid or quebracho for carboxymethyl cellulose in the depressant WW82 reagent gives improved iron rejection.

To illustrate the utility of the reagents, laboratory froth flotation tests, numbers F-38 and F-39 were performed on an ore of the type used in Example 5. In both tests, the collector used was CB110-B3. The reagent additions were as follows:-

Rea ent Addition t

Rougher Test No.

F-38

F-39

Cleaners Test No. Depressants and Modifiers Collector

F-38 Sodium sulfide 600 200

DA663 150

WW82/Tannic Acid 300

F-39 Sodium sulfide 600 200

DA663 150

WW82/quebracho 300

The pH of these collectors were as follows:

Roughers Cleaners

F-38 11.1 10.6 F-39 11.1 10.7

The results of these tests are shown in Table 8.

T A B L E 8

Test No. Product Weight Assays X X Distribution

^Y2°3 ^a2°3 Fe Total ^Y2°3 La₂0₃ Fe Total

F-38

HEAD (Calc) 100.00 0.88 1.52 24.5 100.0 100.0 100.0

F-39

HEAD (Calc) 100.00 0.86 1.51 24.6 100.0 100.0 100.0

For these results, it is evident that about 95% of iron was rejected.

Other depressants and modifiers that have been tested satisfactorily include: -

Rea ent Additives t

Reagent Additives g/t

Cleaners

Test No. Depressants and Modifiers pH

F-37 DA663 300 10.7 WW82/770 525

F-40 DA663/Ammonium thioglycollate 150 10.7

WW82/CMC 300

F-41 DA663/Acrysol A3 150 10.7

WW82/CMC 300 F-42 DA663/Sodium carbonate 150 10.7

WW82/CMC 300

F-43 DA663/E-5 150 10.7

WW82/CMC 300

F-44 DA663 150 10.7 WW82/CMC/sodium dichro ate 300 F-45 DA663 150 10.6

WW82/CMC/potassium permanganate 300 F-46 DA663 150 10.6

WW82/CMC/A-3 300 F-47 DA663 150 10.7

WW82/sodium sulfite 300

Each of the roughers included 5000 g/t of sodium sulfide whilst in the cleaners, the concentration was 600 g/t. The pH of all of the roughers was 11.1. The collector CB110-B3 was used at 2000 g/t for the roughers and at 400 g/t for cleaners F-37, F-40 and F-41, 300 g/t for F-44 and F-47 and at 200 g/t for the remainder.

EXAMPLE 8

To further demonstrate the utility of the invention, a series of continuous pilot plant tests were conducted using the collector CB110-B3. The results for these tests designated PP-10, PP-12 and PP-13 are shown in Table 9.

From these results it will be noted that the iron rejection from the cleaner concentrate was 95-97%. This compares favourably with laboratory tests.

T A B L E

Test Product Weight Assays X X Distribution No. X

Fe Total ^a2°3 Ce₂0₃ Sm„0„ Fe La₉0~ Ce„0- Sm₂0₃ ^J Total ^{l 5 ~ ~}

PP-10 Cleaner Concentrate Combined Tailing Primary Slimes Secondary Slimes

HEAD (Calc) 100.0 31.1 4.09 8.57 0.30 100.0 100.0 100.0 100.0

PP-12 Cleaner Concentrate Combined Tailing Primary Slimes Secondary Slimes

HEAD (Calc) 100.0 31.2 3.90 8.03 0.27 100.0 100.0 100.0 100.0

PP-13 Cleaner Concentrate Combined Tailing Primary Slimes Secondary Slimes

HEAD (Calc) 100.0 31.5 3.88 8.06 0.28 100.0 100.0 100.0 100.0

It has been found that the addition of the oxidized collector emulsion described above, to a slurry of monazite ore containing iron oxides and manganese compounds, can attain a separation of monazite that has not been hitherto achieved.

It has also been shown that this oxidized collector emulsion is suitable for recovering yttrium group minerals, such as churchite, xenotime and gadolinite.

The selectivity of the collector agent has been found to be increased in the presence of sodium sulphide as conditioning reagent in assisting the depression of clay minerals and iron oxides.

Another advantage of this flotation separation method is that the recovery of yttrium group minerals is additionally increased. These compounds report in the froth.

Although the present invention has been described with reference to the preferred embodiment, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand.

Claims

CLAIMS: -

1. A collector agent for the froth flotation separation of rare earth minerals in an ore or concentrate, comprising a composition formed by preparing an emulsion of: a fatty acid; an emulsifier; a phosphonic acid derivative or salt thereof; optionally an oil and/or an amine; and subsequently oxidizing the emulsion until it becomes homogenized.

2. A collector as in claim 1 wherein the concentration of fatty acid is in the range of from 48-62 wt%.

3. A collector agent as in claim 1 or claim 2 wherein the fatty acid is selected from the group consisting of tall oil and oleic acid.

4. A collector as in any one of claims 1 to 3 wherein the emulsifier is in a concentration of from 14-22%.

5. A collector as in any one of claims 1 to 4 wherein the emulsifier is selected from the group consisting of sodium oleate and a secondary amine modified sulfonated fatty acid having branched or straight aliphatic chains containing 15-19 carbon atoms.

6. A collector as in any one of claims 1 to 5 wherein the phosphonic acid derivative or salt thereof is selected from the group consisting of Na-2-ethylhexylimino-bis- methylenephosphonate, benzylphosphonic acid, styrenephosphonic acid and nitrilotrio(methylenephosphonic) acid.

7. A collector as in any one of claims 1 to 6 wherein the phosphonic acid derivative or salt thereof is in a concentration of 14-30 wt%, preferably 14-22 wt%.

8. A collector as in any one of claims 1 to 7 wherein the oil is included in a concentration of from 8 to 12% and is a non-polar lower carbon chain oil.

9. A collector as in claim 8 wherein the oil is selected from the group consisting of fuel oil and pine oil.

10. A collector as in any one of claims 1 to 9 wherein the amine is added at a concentration of 10% w/w with respect to the emulsion.

11. A collector as in claim 10 wherein the amine is dehydroabietyla ine.

12. A collector as in any one of claims 1 to 11 wherein the collector is oxidized by heating in air at a temperature of at least 60°C.

13. A process for the beneficiation of rare earth minerals contained in an ore or concentrate comprising the steps of:

(a) forming the ore or concentrate into an aqueous slurry;

(b) adding to said slurry a collector agent formed by preparing an emulsion of:

(i) a fatty acid,

(ii) an emulsifier,

(iii) a phosphonic acid derivative or a salt thereof, optionally an oil and/or an amine, and then oxidizing the emulsion until said emulsion becomes homogenized;

(c) subjecting said emulsion containing slurry to froth flotation; and

(d) separating a froth containing rare earth minreals and a tailing comprising unwanted materials.

14. A process as in claim 13 wherein said aqueous slurry is conditioned with pH modifier and depressant prior to the addition of said collector.

15. A process as in claim 13 or claim 14 wherein said ore or concentrate is ground prior to being formed into an aqueous slurry.

16. A process as in any one of claims 13 to 15 wherein the collector comprises: a fatty acid selected from the group consisting of tall oil and oleic acid, an emulsifier selected from the group consisting of sodium oleate and a secondary amine modified sulfonated fatty acid having branched or straight aliphatic chains containing 15-19 carbon atoms, and a phosphonic acid derivative or salt thereof selected from the group consisting of Na-2-ethylhexylimino-bis- methylenephosphonate, benzylphosphonic acid, styrenephosphonic acid and nitrilotris(methylenephosphonic) acid.

17. A process as in any one of claims 13 to 16 wherein the fatty acid is in a concentration of from 48-62 wt%, the emulsifier is in a concentration of from 14-22 wt%, and the phosphonic acid derivative or salt thereof is in a concentration of from 14-30 wt%, preferably 14-22 wt%.

18. A process as in any one of claims 13 to 17 wherein the oil is included in a concentration of from 8-12 wt% and is a non-polar lower carbon chain oil.

19. A process as in claim 18 wherein the oil is selected from the group consisting of fuel oil and pine oil.

20. A process as in any one of claims 13 to 19 wherein the amine is added at a concentration of 10% w/w with respect to the emulsion.

21. A process as in claim 20 wherein the amine is dehydroabietylamine.

22. A process as in any one of claims 13 to 21 wherein the collector is oxidized by heating in air at a temperature of at least 60°C.

23. A process as in any one of claims 14 to 22 wherein the depressant and pH modifier comprises sodium sulfide and a mixture of dextrin, carboxymethylcellulose, mercapto- acetic acid and optionally an acrylic acid homopolymer.

24. A process as in any one of claims 14 to 22 wherein the depressant and pH modifier comprises sodium sulfide and a mixture of dextrin, mercapto-acetic acid and either tannic acid or quebracho and optionally an acrylic acid homopolymer.

25. A process as in any one of claims 13 to 24 wherein the froth flotation step includes a rougher flotation stage and at least one cleaner flotation stage.

26. A process as in any one of claims 13 to 25 wherein the ore is monazite contained in a complex ore.