5,106,489 Zircon-rutile-ilmenite froth flotation process

Patent Number/Link:

111111111111111111111111111111111111111111111111111111111111111111111111111

United States Patent [19]

Schmidt et aI.

[11]

[45]

USOO5106489A

Patent Number:

Date of Patent:

5,106,489

Apr. 21, 1992

14 Claims, 1 Drawing Sheet

3,482.688 12/1969 Bushell et a!. 2091166

4.214.710 7/1980 Wilson 241124

4,261.846 4/1981 Wilson 252/61

4.339.331 7/1982 Lim 209/167

4.362.615 12/1982 Llewellyn et aI 209/167

4,437,983 311984 Petrovich 2091166

FOREIGN PATENT DOCUMENTS

14780 10/1933 Australia 209/166

542775 6/1957 Canada 209/166

406018 211934 United Kingdom 209/166

406043 2/1934 United Kingdom 209/166

Primary Examiner-Stanley S. Silverman

Assistant Examiner-Thomas M. Lithgow

Attorney, Agent. or Firm-Darby & Darby

This invention relates to a method for recovering a bulk

concentrate of zircon and a bulk concentrate of rutileilmenite

from dry plant tailings. A process has been

discovered for froth flotation by manipulating the surface

charges of dry plant tailings. Conditioning reagents,

sulfuric acid to lower the pH; com starch to coat

the minerals to be depressed; sodium fluoride to activate

the minerals to be floated; and amine to float the activated

minerals, are used in the flotation process.

[57] ABSTRACT

2,387.856 10/1945 Pickens 209/166

2.557,455 6/1951 Moyer 209/166

2.610.738 9/1952 Cuthbenson 209/167

2.665.004 1/1954 Zukosky 209/166

2.792.940 5/1957 Baarson 209/166

2.904,177 9/1959 Michal 209/166

3.097,162 7/1963 Baarson 209/166

3.117.924 1/1964 Baarson 209/166

3.480.143 1111969 Mitzmager 209/166

[54] ZIRCO!'li·RUTILE·ILME1'IITE FROTH

FLOTATIO!'li PROCESS

[75] Inventors: Roland Schmidt, Lakewood; Dale L.

Denham, Jr., Louisville, both of

Colo.

[73] Assignee: Sierra Rutile Limited, Santa Rosa,

Calif.

[21] Appl. No.: 742,604

[22] Filed: Aug. 8, 1991

[51] Int. Cl.5 B03D 1/016; B03D 1/018;

B03D 1/02; B03D 1/08

[52] U.S. Cl 209/166; 209/167;

209/17; 209/10

[58] Field of Search 209/13, 17, 18, 164,

209/166, 167, 10; 423/73, 80, 81; 252161

[56] References Cited

U.S. PATENT DOCUMENTS

VERSIZE

IMES

SULFURIC ACID

AMINE

RUTILE AND ILMENITE

51 NK PROOOCT

ZROOO

PRODUCT

NoOH

FEED

. OVERSIZE

IMES

SULFURIC ACID

STARCH

NaF FI G. 1

AMINE

•TJ).

•

~=......

(D=......

>"Cl

"""" ~

"'I"C""

'IC

RUTILE AND ILMENITE

SINK PRODUCT

ZIROON

PRODUCT

...t..i.l o

..0. \

SUMMARY OF THE INVENTION

DETAILED DES:RIPTION OF THE

INVENTION

BRIEF DESCRIPTION OF THE DRAWING

This invention is directed to a method for recovering

a bulk concentrate of zircon and a bulk concentrate of

rutile/-ilmenite from dry plant tailings. More specifically,

the invention is directed to a froth flotation process

which manipulates the surface charges of dry plant

tailings with conditioning reagents: acid to lower the

pH; starch to coat the minerals to be depressed; fluoride

ions to activate the mineral to be floated; and a cationic

amine collector to float the activated mineral.

zircon and the rutile/ilmenite can be recovered. Thus,

in the present invention both the zircon bulk concentrate

and rutilelilmenite bulk concentrate are recovered

as final products and are further cleaned as required by

5 dry processing to marketable grade products.

It is an advantage of the present invention that high

concentrations of two desired bulk products can be

recovered from dry plant tailings. Other advantages of

the present invention are that the flotation process provides

a means for recovering fine titanium and zircon

values that are not efficiently recovered by conventional

dry processing. Further, since these plant tailings

are rejects from the conventional dry processing. it is

likely that treating them again by the same dry methods

would be inefficient, and hence a new process is required

to allow the tailing to be recovered. It has been

determined that it is advantageous to separate two bulk

products in a froth flotation process by manipulating the

surface charges on the minerals of the dry plant tailings.

FIG. 1 is a flow diagram of the process according to

35 the present invention.

5,106,489

ZIRCOS-RL'TILE-ILMEl'IITE FROTH

FLOTATIOS PROCESS

BACKGROUND OF THE INVENTION

This invention relates, in general, to the separation of

dry plant tailings into two bulk concentrates. More

specifically, it relates to a froth flotation method for the

separation of a bulk concentrate which comprises zircon

from another bulk concentrate which comprises 10

rutile and ilmenite.

Conventional flotation processes have been used to

separate minerals such as copper, molybdenum, zinc,

iron, tungsten, and kyanite from waste and other minerals.

The minerals are separated by generating air bub- 15

bles which selectively attach to the mineral or minerals

to be floated. The proper conditions must be present in

the flotation process to permit attachment of the mineral

to the bubbles. The air bubbles, together with the

attached group, rise to the surface to form a froth which 20

is removed. However, if the weight of the particles is

too high or the forces of attachment are too weak, the

minerals will drop from the bubbles and the minerals

will not become part of the froth. Therefore, the weight

of the particles must be low enough and the forces of 25

attachment strong enough to permit the bubbles to rise

while carrying the mineral with it.

It is known in froth flotation technology to use anionic-

type promoters to provide proper conditions for the

attachment of minerals to air bubbles. For example, an 30

anionic-type promoter has been used to condition phosphorus-

bearing minerals for attachment to air bubbles.

See, for instance, U.S. Pat. Nos. 2,557,455 and

3,482.688. It is also known to use depressants in froth

flotation processes for depressing the minerals which

form the sink product. For example, U.S. Pat. No.

2,497,863 is directed to subjecting pulp to a processed

starch product to depress the minerals in the pulp.

In the conventional froth flotation systems, silicates It has now been discovered that a product of zircon

are separated from the titanium values. Titanium values 40 or zircon and aluminum minerals can be separated from

are present in. ilmenite and rutile. Ilmenite is a com- a sink product of rutile and ilmenite by flotation. In the

pound of ferrous oxide and titanium dioxide and rutile is process, the s~rface of the float product is made electroa

compound of titanium dioxide. After the separation of negative at low pH and, hence, ready to accept a catithe

titanium values, the titanium values are retained as onic (positive) amine collector. It is known that at very

the desired product and the silicates are discarded. 45 low pH values minerals such as zircon, garnet, silliman-

In U.S. Pat. No. 2,904,177 a flotation method is used ite, kyanite and corundum will have surfaces that have

for the removal of silicates from an ihnenite ore. The a net positive charge. Therefore, if a cationic collector

silicates present in the ilmenite ore are garnet, feldspar, having a positive charge is added to the minerals there

hornblende and augite. The silicates are removed by will be no electrostatic attraction between the two posigrinding

the ore to -60 mesh size; preparing an aque- 50 tive charges. However, it has been proposed that the

ous pulp with the ground ore; acidifying the pulp with addition of a fluoride ion or a fluorosilicate complex to

hydrofluoric acid; adding starch to the pulp to depress the mineral to be floated at low pH will render the

the titanium values present in the ilmenite ore; adding to surface of the mineral negative and it will then be capathe

pulp a cationic amine flotation agent; and SUbjecting hIe of accepting a cationic amine collector. The precise

the treated pulp to a froth flotation. According to this 55 mechanism for activation of these silicates is uncertain.

patent, the titanium values form the desired product and FIG. 1 illustrates the basic concept of the froth flotathe

silicates are discarded. In this patent, the pH is low- tion flow pr()Ce5S of this invention. A scrubber 10 reered

before subjecting the treated pulp to froth flotation ceives the flotation feed prior to flotation. NaOH is

to remove the feldspars and other silicates. Although added to the scrubber 10 for removing coatings on the

this method has been used to recover titanium values, 60 minerals of the feed, such as slimes. The feed from the

this conventional process has not been used to recover scrubber 10 is transferred to the screens 25 for removing

a zircon float product from a rutile/ilmenite sink prod- minerals too coarse for the flotation process. The screen

uct. undersize product can be made denser in a hydrocy-

It has now been found that zircon, a valuable mineral, clone 27 prior to conditioning. The hydrocyclone can

can be effectively recovered from tailings by means of 65 also remove the slimes released from the minerals in the

froth flotation. In the present invention, dry plant tail- scrubber 10. The screen oversize product can be further

ings are used which comprise zircon, aluminum miner- upgraded and the slimes from the hydrocyclones 1.7 can

als, quartz, ilmenite and rutile from which tailtngs the be discarded. The feed from the hydrocyclones 27 is

5,106,489

oxides. The zircon and other silicates are the desired

float products.

The quantity of sulfuric acid used depends on the

desired pH and the presence of acid-consuming miner-

S als; generally, about 1-10 Ibs of sulfuric acid per ton of

feed to the flotation cells are used. Sulfuric acid has the

advantages of low cost and less corrosivity to equipment

than other acids. Also, concentrated sulfuric acid

can be used to lower the pH value without substantially

10 increasing the volume of the feed. Examples of other

acids which can be used as pH modifiers are hydrochloric,

hydrofluoric and nitric acid. However, hydrofluoric

acid at a pH of less than 2.5 may undesirably activate

the titanium oxides.

15 Fluoride is used in various forms, such as NaF, Na2-

SiF6 and HF, to provide fluoride ions for changing the

surface charge of the minerals to be floated. Thus, fluoride

activates the minerals to be floated such that the

surface of the minerals acquires a net negative charge.

The fluoride ions, F-, or fluorosilicate complex,

SiF62-, is attracted to the positively charged surface to

be floated such that a negative surface is produced.

During conditioning at low pH some of the NaF and

Na2SiF6 may be converted to HF. If HF is formed, the

25 HF has an active role in scrubbing the minerals. The

scrubbing of the minerals produces clean surfaces

which help the attachment of activators, depressants

and amine collectors to the mineral surfaces. The addition

of high levels of NaF at low pH can generate

slimes, which can be due to the attacking (or scrubbing)

of the ilmenite and other minerals. Preferably, NaF is

used at about 2.0 Ibs per ton of rougher flotation feed.

The amount of sodium fluoride added can be extended

from about 2.0 Ibs per ton flotation feed to about 5.0 Ibs

per ton of flotation feed depending upon the amounts of

silicate minerals present in the feed and tne concentration

of other chemicals in the flotation water. As the

amount of sodium fluoride is decreased, the froth becomes

darker, indicating that more ilmenite and rutile

are being floated instead of forming the desired sink

product. Since the fluoride ion is negative, if added in

excess, it can neutralize positive collector ions and,

. hence, interfere with flotation. The amount of NaF

required will increase or decrease with the amount and

size of the silicates that are present.

Starch is added to the pulp to depress the minerals

which form the sink product. Starch has been used in

conventional systems for the depression of iron oxides.

However, the possibility exists that starch, as an anionic

SO (-) molecule, could react with the cationic (+) collectors

and neutralize the collector without allowing the

collector to attach to the surface of the mineral. It has

been determined that starch can be used with sodium

fluoride without conflicting with the activation of the

products to be floated or the attachment of the cationic

collector to the activated mineral surfaces. It has been

determined that the starch and the cationic collector do

not conflict with each other to the extent that flotation

is noticeably affected because the titanium oxides remain

positively charged at a pH range of about 2.0-6.0.

It is known that titanium oxides are positively charged

because of having a high point of zero charge (PZC).

For example, the PZC ofrutile is about 6.7 and the PZC

of ilmenite is about 6.5. The positively charged titanium

oxides selectively absorb the negatively charged starch

to prevent absorption of the collector on the titanium

oxides and, hence, cause depression of the oxides. It has

also been determined that starch and sodium fluoride do

transferred to the conditioners 20. Sulfuric acid. starch,

NaF. and amine are added in the conditioners 20. After

the conditioners 20, the conditioned flotation feed is

transferred to rougher flotation cells 30 for separating

the flotation feed into the zircon float product and the

rutile and ilmenite sink product. Amine is added during

flotation in the rougher flotation cells 30. The zircon

float product is transferred to cleaner cells 40. Amine is

added in the cleaner cells 40 as required. The cleaner

cells 40 separate the zircon float product from the

cleaner rutile and ilmenite sink product. The rutile and

ilmenite sink product from the cleaner cells 40 is combined

with the rutile and ilmenite sink product from the

flotation cells 30 or it is returned to join the feed to the

rougher cells.

It is desirable in the flotation process that zircon be

removed as the float product from an ilmenite/rutile

sink product. It is also desirable that the aluminum minerals

in the tailings are removed from the ilmenite/rutile

sink product. Examples of such aluminum minerals are 20

garnet, Fe3Ah(Si04h, Ca3AI2(Si04l3, kyanite (Ah03.SiOl)

and corundum (AI203). The aluminum minerals

are floated from the sink product, in a similar manner to

floating the zircon, by manipulating the charges on the

mineral surfaces.

In carrying out the process of the present invention,

the feed is either size classified to remove the coarse

fraction of the feed or is ground to a particle size which

is small enough to· allow the desired mineral to be

floated by air bubbles. Preferably, the feed is ground or 30

size classified to a particle size of about - 80 mesh.

Exemplary of the minerals which can be present in such

tailings are rutile, ilmenite, quartz, garnet, iron oxides.

zircon, corundum, sillimanite and kyanite. While the

preferred feed materials in the process of the invention 35

are dry plant tailings, the process also applies to materials

of the same minerals, such as an ore, or to minerals

other than those from a dry plant.

It may be necessary to process the dry plant tailings

ahead of flotation in order to make the material more 40

suitable for flotation. For example, the dry plant tailings

can be first upgraded by a spiral gravity circuit to remove

some of the low gravity quartz prior to flotation.

In some cases, there may not be enough quartz present

in the feed to warrant a separate gravity circuit ahead of 45

the flotation. Other treatments as are known in the art

can also be used to remove specific minerals ahead of

the flotation, if economically favorable.

Conditioning and subsequent flotation can be carried

out in any conventional cell suitable for froth flotation

at ambient temperature, e.g., a range of about 5° C. to

about 40° c., and at atmospheric pressure. Conditioning

agents comprise a scrubbing agent, a pH modifier, a

depressant, an activator and a collector.

The tailings can be scrubbed prior to flotation with 55

sulfuric acid, hydrochloric acid or sodium hydroxide.

The scrubbing removes coatings on the minerals which

would inhibit separation of the minerals during the

flotation process. It has been determined that sodium

hydroxide is advantageous for removing coatings and is 60

economically preferable.

Sulfuric acid is the preferred pH modifier to lower

the pH as required. Preferably, the pH is lowered to a

value between about 2.0 and 6.0 for flotation of zircon.

Most preferably, the pH is lowered to a pH value of 65

between 2.0 and 3.0 for flotation ofthe aluminum minerals

(i.e., gamet, kyanite sillimanite and corundum) and

zircon, present in the tailings, away from the titanium

5,106,489

derivatives of the coco amine can also be used. The

primary coco amines are produced from a coconut fatty

add by a reaction with ammonia. The coco amines are

weak bases, and are soluble in common organic sol-

S vents, but are insoluble in water. The salts are prepared

by reacting the amines with acetic acid and are water

dispersible. The primary amines are in a liquid form at

25" C. Coco primary amines are readily available in the

marketplace. For example, coco primary amines are

sold by Sherex Chemical and Akzo Chemicals. Arosurf

MG-I60, manufactured by Sherex Chemical, and

Armac C, manufactured by Akzo Chemicals, are examples

of coco amine derivatives which can be used as an

amine collector. Armac C is a corrosive paste with a

slightly acetic acid odor. Armac C has a melting point

of about 50" C. and it decomposes on extended heating.

The decomposition rate of Armac C increases with

increasing temperature.

Primary amines can be prepared or mixed in several

ways prior to adding these amines to the flotation conditioners

and flotation cells. There are advantages and

disadvantages to each method of preparation and the

method selected depends on many factors which are

peculiar to the flotation circuit. However, each method

of preparation will result in flotation. For example, the

primary coco amine can be added as a free base, the

amine can be neutralized about 50% with acetic acid

and made up to about a 4.0% solution in water, and the

amine can be mixed with water, neutralized and a

frother added. Other methods for preparing the primary

amines are also known in the art.

Preferably, the pH modifier is added first, followed

by the starch, the fluoride, and the cationic amine collector.

The starch, sodium fluoride and pH modifier can

be added and conditioned in any order before the addition

of the cationic amine collector, but if the preferred

order is not used the results may not be optimal. The pH

modifier, starch, fluoride and cationic amine collector

are all added and conditioned before the flotation begins

in the flotation cells. These flotation cells can be described

as a rougher flotation, which flotation produces

a zircon froth product and an ilmenite/rutile sink product.

It is preferred, but not required, that the amine be

conditioned separately in its own conditioner. The initial

addition of amine can be added to the feed in the

first flotation cell, or added just ahead of the first flotation

cell, rather than being added to the feed in a special

conditioner cell. After the flotation begins, an additional

amount of the starch depressant can be added

based on the color of the froth observed during the

flotation process. For example, if the froth becomes

black in color then ilmenite and rutile are being pulled

into the froth and an additional amount of starch can be

added to depress the ilmenite and rutile, Also, after the

flotation begins, cationic amine collector can be added

as necessary in several stages depending on an analysis

of the froth observed during the flotation process. If the

froth is not mineralized, then more amine is needed.

When the reagents are in balance, the froth has a brown

color (from the zircon) or a pink color (if considerable

garnet is present). The cationic amine collector addition

rate can also be automatically controlled to increase

recovery of the zircon.

The zircon froth product can be subjected to a second

flotation, described as a cleaner flotation, for upgrading

the zircon froth product. In the cleaner flotation,

the zircon froth product from the rougher flotation

is moved to another set of cells called cleaner cells, the

not compete for the same mineral surfaces, that is. the

starch interacts with the titanium minerals and slimes

and not with the silicates. The NaF interacts with the

silicates and does not interact to any noticeable degree

with the titanium minerals.

Preferably, corn starch, consisting of polymers of

dextrose, is used as the depressant for rutile, ilmenite

and quartz. Many industrial corn starch products can be

used as a depressant for titanium minerals and to control

slimes, as are known in the art. As an example of the 10

starch, it is possible to use a starch sold under the tradename

Corn Products Starch 3005 by the Corn Products

International Company. The carboxylate group of the

starch provides the negative charges on the starch molecule.

The starch is a dry, fine grained powder and is 15

slightly acidic when dispersed in water. A 2.5% solution

becomes slightly viscous and opalescent upon heating.

Concentrated solutions of the starch become very

viscous and difficult to work with.

To develop the adhesive properties of the starch, the 20

starch is dispersed in water to form a slurry. The slurry

is heated, preferably to a boiling temperature, to disrupt

bonding of the starch molecules. The amount of starch

used in the process is dependent on the quantity of

titanium oxides in the feed, the quantity of amine collec- 25

tor used, the amount of slimes present and the pH value.

It is desired that the quantity of starch is balanced with

the feed composition, size of particles in the feed and

amount of reagents so that the titanium oxides are sufficiently

depressed. It is also desired that the starch be 30

added in a sufficient amount but not be added in excess.

The addition of excess starch can depress zircon and

other minerals which are to be floated. The addition of

starch controls slimes, which can be present in the flotation

cell, by flocculating the slimes. At low pH slimes 35

have a positive charge and the negative starch adheres

to the slimes so that flocculation will occur. Flocculation

of the slimes gathers the slimes together so that the

slimes are not attracted to the mineral surfaces. Excess

starch could neutralize the amine collector and require 40

the use of more amine than is normally necessary. For

example, it has been determined that if starch is added in

excess, the flotation of zircon and other minerals to be

floated can be diminished completely due to the neutralization

of the cationic collector with the anionic starch, 45

since neutralization of the collector can result in con!>

umption of the cationic collector. It is, therefore, preferable

to balance the amount of starch used with the

feed composition and the amount of reagents used. For

example, the quantity of starch used can range from SO

about 0.5 to about 10.0 lbs/ton of flotation feed.

If quartz is present in the feed, the quartz can be

depressed by the addition of starch. The starch preferentially

coats the rutile and the ilmenite and the excess

starch coats the quartz. If it is desired that the quartz be 5S

depressed, starch in excess of the amount to depress the

rutile/ilmenite and control slimes can be added. Alternatively,

if it is desired that the quartz be floated, then

less starch is used in the flotation.

A collector is used to float the desired minerals. Spe- 60

cifically, a collector is adsorbed on the surface of the

mineral to be floated to make the particles hydrophobic

(water repellent) which promotes adherence to the air

bubbles present in the flotation cells.

The amine collector which is used is a fatty amine. 6S

Preferably, the amine collector is a coco amine having

the formula RNH2, where R is C6-e18 with 55% C12

having a molecular weight of about 203, The salts and

5,106,489

A composition of 20.4% Zr02, (about 30% zircon)

and 38.3% Ti02 (about 21% ilmenite and 27% rutile),

with the remainder of the composition consisting of

quartz (about 10%), garnet (about 9%), minor constituents

of kyanite, sillimanite, corundum and iron oxide SS

(about 3%) was scrubbed with 1.0 Ibs/ton NaOH at

82% solids in a rubber-lined, four compartment (I cubic

ft. each), Denver attrition scrubber. Retention time was

9-11 minutes and throughput was 1400 Ibs/hr. The

scrubbed sample was wet screened at 80 and 325 mesh 60

on Derrick and Sweco screens, respectively. This composition

forms the conditioned feed shown in FIG. 1.

H2S04 was added at 3.0 Ibs/ton feed to obtain a pH

value of 2.7. The 80X 325 mesh product was conditioned

with 1.0 Ibs/ton feed ofa 2.5% solution of boiled 6S

com starch. A 3.0% solution of NaF was added at 2.0

Ibs/ton feed at 50% solids. Arosurf 160 was added as a

cationic amine collector at 0.1 Ibs/ton feed.

pH is held in the same range as used in the rougher

flotation, and the amine, if used, is added at about 0.05

to 0.30 Ibs per ton of feed to the rougher cells. The

cleaner stage can be used to drop out unwanted ilmenite

and rutile from the froth product into the sink product. 5

where it can be discarded or sent back to the rougher

cell feed. If the cleaner feed is fully reagentized it may

not be necessary to add more amine, starch or sodium

fluoride to the cleaner cells.

Ifsufficient quartz is in the rougher sink product, that 10

product can be taken to another flotation cell where a

cationic silica flotation is carried out at about pH 10.

Sodium hydroxide is added in sufficient quantity to raise

the pH and amine is added in sufficient amount to float

the quartz. Normally, no additional starch is required to 15

keep the ilmenite and rutile depressed. The quartz float

product is discarded and the sink product is a rough

concentrate of rutile and ilmenite.

Lime maybe added prior to the tailings disposal to

neutralize excess sulfuric acid and flocculate slimes 20

produced in the flotation system.

In an embodiment of the present invention, NaOH is

used to increase the pH after flotation so that the quartz

that was depressed by the starch can be floated away

from the titanium oxides. The product produced after 25

removal of the quartz is a high grade titanium oxide

product. The sodium hydroxide also cleans the mineral

surfaces to free the surfaces of slimes by providing

OH- to the slimes which become electronegative and,

hence, are dispersed. For example, the quantity of 30

NaOH used is about 1.0 Ib/ton of feed.

Bentonite clay is used to remove the amine from the

float product, to render the zircon suitable for subsequent

processing. Bentonite has a very high negative

charge. Therefore, bentonite has a high affinity for a 35

positively charged amine. If bentonite is added to the

flotation concentrate and conditioned, the bonds between

the positive amine and the zircon are broken and

new bonds are formed between the positive amine and

the bentonite. Thereafter, the bentonite, with the at- 40

tached amine, can be removed from the float product by

desliming in a unit operation such as cycloning. Bentonite

is composed of the clay mineral montmorillonite

«Na,Ca)(J.33(AI,MghSi40Io(OHh·nH20). Bentonite

can be added at about 2.0 to about 5.0 Ibs/ton of zircon 45

flotation product.

In order to illustrate the process of the present invention,

the following examples are presented:

EXAMPLE 2

The zircon froth product was put back into the same

flotation cell and refloated (cleaner flotation) at pH 2.5

with no collector addition. The froth was conditioned

for one minute (no air) to break loose any entrapped

ilmenite and rutile particles. The sink product from the

cleaner flotation was joined with a new quantity offeed.

The zircon concentrate (final froth product) was removed.

2.5

0.1

0.05

1,500

Flotation

4-6

0.20-0.35

2.5

3.5

2.0

3.0

0.1

1,500

Rougher Flotation Conditions

Conditioning

TABLE I

Parameter

1st, Ibslton

Subsequent, Ibs/ton

Cell rpm

Sulfuric Acid. pH

Swch. Ibs/ton

Sodium Fluoride, Ibs/ton

Percent Solids

Time, minutes

Armac C, Ibs/ton

Stages of amine (Armac C)

collector addition

A three stage locked cycle flotation scheme was used

having a zircon rougher flotation at low pH, a zircon

cleaner flotation at low pH and a quartz flotation from

the rougher sink product at high pH. About 500 grams

of a composition having zircon 31.7%, other silicates

11.1%, rutile 33.9%, ilmenite 21.1 %, and miscellaneous

unidentified minerals 2.2%, was used. The rougher

zircon flotation was carried out at a 2.5 pH value. The

conditions of the rougher flotation are summarized in

Table 1.

The starch. H2S04, NaF and amine were added to the

scrubbed sample by transferring the sample to a first set

of four plexiglass conditioning cells and adding the

reagents to the cells. Retention time was two minutes

per cell.

The conditioned feed was diluted to 35% to 40%

solids and floated in rougher cells. The feed rate was

220 Ibs/hour to this set of cells to give a retention time

in the cells of about six minutes. Amine was added to

the second and third of four rougher cells at 0.06

Ibs/ton of rougher feed. The rougher concentrate was

diluted to about 20% solids in a launder.

The float product from the rougher cells was transferred

to cleaner cells. In the cleaner cells, the float

product was cleaned. Additional amine was added to a

first, second and third cleaner cell of four cleaner cells

at a rate ofO.03Ibs/ton feed. There was a retention time

of about 12 minutes in the cleaner flotation.

The cleaned zircon flotation product shown in FIG.

1 assayed 47.7% Zr02 and 2.13% Ti02 which is 89.3%

of the Zr02 and 2.0% of the Ti02 in the feed. If the

rougher and first cleaner tailings are combined, recovery

is 98.0% of the Ti02 in the feed and the product

assayed 59.2% TiO,. The major contaminants are

quartz and garnet. The garnet is readily activated and

most is pulled into the final froth product with zircon

since it is activated in a similar manner. The quartz

tends to distribute itself such that most of the coarse

quartz sinks into the ilmenite/rutile product and some

of the finer quartz floats with the zircon. The combined

product also contains 3.2% Zr02 which is 10.7% of the

Zr02 in the feed.

EXAMPLE I so

subjecting the mixture contaInIng the added acid

solution, the fluoride ions, the starch and the cationic

collector, to froth flotation; and

withdrawing a float product comprising the zicron

and a sink product comprising the ilmenite and

rutile.

2. The method according to claim 1, wherein the

mixture of minerals further comprises aluminum silicate

minerals wherein the adding of fluoride ions activates

10 the aluminum silicate minerals and the amine cationic

collector floats the activated aluminum silicate minerals,

the float product further comprises the aluminum

silicate minerals.

3. The method according to claim 2 wherein the

15 mixture is acidified to a pH of between about 2.0 and

3.0.

4. The method according to claim 1 wherein the acid

solution comprises H2S04.

5. The method according to claim 1 wherein the

20 fluoride ions are obtained from at least one member

selected from the group consisting of NaF, HF and

Na2SiF6.

6. The method according to claim 5 wherein the

source of fluoride is NaF.

7. The method according to claim 1 wherein the

amine collector is coco amine having the formula

RNH2 wherein R is C6-C18 with 55% C12.

8. The method of claim 1 further comprising the step

of adding bentonite clay to remove the amine collector

30 from the zircon.

9. The method of claim 1 wherein the starch is com

starch.

10. The method of claim 9 wherein the starch is prepared

by mixing the starch in water to form a slurry and

heating the slurry to a temperature for disrupting bonding

of the molecules of the starch.

11. The method according to claim 1 further comprising

before the step of adding an acid solution, the step of

adding water to the mixture and the step of processing

the particles of the mixture such that the particle sizes of

the minerals are suitable for flotation.

12. The method of claim 1 wherein the mixture of

minerals further comprises quartz and the adding of the

starch depresses the quartz so that the sink product

further comprises the quartz.

13. The method of claim 12 further comprising adding

NaOH for increasing the pH after the step of subjecting

the mixture to flotation and subjecting the sink

product to a second froth flotation and withdrawing a

second float product comprising quartz and a second

sink product comprising the ilmenite and rutile.

14. The method of claim 1 further comprising adding

a second cationic amine collector to the float product

and subjecting the added second cationic amine collector

and the float product to a cleaner froth flotation, and

withdrawing a cleaned float product.

• • • • •

5,106,489

1.500

Flotation

2.5

None

2.0-2.5

1.200

Flotation

10.0

4.0-4.5 minutes

0.1

0.05

1,500

10.0

30 second,

0.20-0.25

2.5

None

).0

1.500

TABLE 3

TABLE 2

Qua", Flotation Condition,

Condllioning

Cleaner Flotation Condlllon,

Parameter Conditioning

Sulfuric ACId. pH

c;( Solid~

Reagent Addition

Time. minute,

Cell rpm

The weight splits from the locked cycle flotation 35

scheme are shown in FIG. 1.

Microscopic minerals point count analyses were carried

out on the flotation products and the following

approximate analyses were obtained, The quartz float

product contained about 95% quartz. The zircon float 40

product contained about 72% zircon and the rutile/ilmenite

sink product contained about 97% of rutile and

ilmenite.

We claim:

1. A method for separating a mixture of minerals 45

comprising at least zircon, ilmenite and rutile which

comprises:

adding an acid solution to the mixture to acidify to a

pH of between about 2.0 and 6.0; 50

adding starch to the mixture to depress the ilmenite

and the rutile;

adding a source of fluoride ions to the mixture to

provide a negative surface charge on the zircon

surface to activate the zircon; S5

adding an amine cationic collector to the mixture to

float the activated zircon;

Parameter

1st two. Ib./ton

Subsequent. Ibs/ton

Cell rpm

SodIum Hydroxide. pH

Percent Solid,

TIme

Armac C. Ib./ton

Stage. of amine (Armac C)

collector addition

The sink product from the rougher flotation was then

put in a 500 gram cell and the pH was raised to 10.0

using sodium hydroxide for quartz flotation. The material

in the cell was conditioned for 30 seconds after each

addition of Armac C and the quartz was floated. The

conditions which were used for the quartz flotation are

summarized in Table 3.

The conditions of the cleaner flotation are summarized

in Table 2.