4,690,752 Selective flocculation process for the recovery of phosphate

Patent Number/Link:

United States Patent [19]

Shaw

[11] Patent Number:

[45] Date of Patent:

4,690,752

Sep. 1, 1987

[75] Inventor:

[73] Assignee:

[54] SELECflVE FLOCCULATION PROCESS

FOR THE RECOVERY OF PHOSPHATE

Douglas R. Shaw, Arvada, Colo.

Resource Technology Associates,

Boulder, Colo.

[21] Appl. No.: 719,343

[22] Filed: Apr. 3, 1985

Related U.S. Application Data

[63] Continuation ofSer. No. 524,889, Aug. 19, 1983, abandoned.

4,265,770 5/1981 Thomas 2101715

4,298,169 11/1981 Iwasaki 209/166

4,555,329 11/1985 Sykes et al. 209/5

OTHER PUBLICATIONS

"Dispersion-Flocculation Characteristics of Florida

Phosphate Slimes", A. F. Colombo, Bureau of Mines,

Minnesota, U.S.A.

Friend et aI., "The Separation of Minerals from Mixtures

by Selective Flocculation", Filtration & Separation,

Jan.-Feb., 1972, pp. 25-28.

Primary Examiner-Peter Hruskoci

Attorney. Agent. or Firm-Sheridan, Ross & McIntosh

6 Claims, No Drawings

A process for separating and recovering non-metallic

minerals, particularly phosphate, from an ore containing

non-uniform sized particles, including colloidal particles.

The ore is slurried in an alkaline, aqueous solution

with a dispersing agent. A flotation collector is added,

and the mixture is contacted with a hydrophobic, high

molecular weight, nonionic polymer to flocculate the

fine particles and make them amenable to subsequent

flotation. A second embodiment provides a process for

the recovery of an upgraded non-metallic ore from ore

slimes, such as phosphate slimes, utilizing a high molecular

weight, polyacrylamide, anionic flocculating agent.

[51] Int. Cl.4 B03D 3/06

[52] U.S. Cl•.......................................... 209/5; 209/49;

209/167; 210/705; 210/907

[58] Field of Search 209/5, 49, 166, 167;

210/704, 705, 725, 727, 732, 734, 907

[56] References Cited

U.S. PATENT DOCUMENTS

2,660,303 11/1953 Haseman 209/5

3,020,231 2/1962 Colwell et aI 2101732

3,302,785 2/1967 Greene 209/5

3,314,537 4/1967 Greene 209/5

3,670,883 6/1972 Weir 209/5

3,837,482 9/1974 Sheridan, III 209/5

4,194,969 3/1980 Chung et aI. 209/166

4,235,709 11/1980 Baudet et aI 209/5

[57] ABSTRACT

4,690,752

This is a continuation of application Ser. No. 524,889, 5

filed Aug. 19, 1983, now abandoned.

FIELD OF THE INVENTION

of the references teach the use of a hydrophobic selective

flocculating agent.

It is therefore, the object of the present invention to

improve non-metallic mineral recoveries over those

obtainable by known conventional methods.

A further object of this invention is to provide an

improved and simplified method for phosphate recovery

from phosphate ores by utilizing both coarser sands

and previously waste slimes and subjecting the starting

phosphate feed material to a selective flocculation process

utilizing a hydrophobic flocculating agent.

A still further object of this invention is to provide an

improved and simplified process for phosphate recovery

from phosphate waste slime tailings.

The process of the present invention provides an

excellent overall phosphate recovery of an upgraded

product from a non-uniform size ore containing fine and

colloidal size particles, previously unattainable in, for

example, the Florida phosphate processing industries.

Utilizing the minus 150 mesh to colloidal size particles

of the ore according to the methods of the present invention

increases phosphate yield and reduces tailing

disposal problems now encountered in the Florida

phosphate industries. Moreover, ore slimes, the minus

150 mesh to colloidal size particles, now contained in

tailings ponds can be added to the larger sized particles

to reclaim the approximately 10 to 40% phosphorus

contained in the slimes.

SUMMARY OF THE INVENTION

The present invention involves a process forseparating

and recovering non-metallic minerals, particularly

phosphate, from an ore which has been sized to a nonuniform

size range, from about minus 20 mesh to colloidal

particles. The sized ore is slurried with an alkaline,

aqueous solution with a dispersing agent present. The

non-metallic minera is separated and recovered from

the ore when the slurry is treated by a selective hydrophobic

flocculating agent, followed by conventional

flotation methods, preferably in multiple stages.

In another embodiment of this invention, slimes previously

separated from the larger ore particles are

treated with selected dispersants and flocculating agents

to recover an upgraded phosphate product.

DETAILED DESCRIPTION OF THE

PREFERRED EMBODIMENT

This invention relates a process for the recovery of

non-metallic minerals, particularly phosphate, from an

ore containing said minerals, in which the particle size

of the ore is from about minus 20 mesh down to colloidal

sizes. The fine particles of the ore, the minus 150

mesh to colloidal size, are particularly beneficiated by

the process of this invention for recovering of the desired

non-metallic mineral.

As a broad concept, the process steps involve sizing

the ore to obtain a size range from about minus 20 mesh

to minus 150 mesh. The ore is then preferably washed

with deionized water and a slurry is formed with the

addition of the water. The ratio of solids to liquids is'

selected to allow effective dispersal of the ore particles

and yet provide frequent enough collisions of the particles

after treatment with the flocculating agent to form

recoverable agglomerates. Preferably the ratio of solids

to liquids is at most about 40%, and more preferably

between about 20% and about 30%. A dispersing agent,

such as sodium silicate or sodium hydroxide, is added to

the aqueous solution. If a non-alkaline dispersing agent

BACKGROUND OF THE INVENTION

SELECfIVE FLOCCULATION PROCESS FOR THE

RECOVERY OF PHOSPHATE

This invention is a minerals beneficiation process

involving selective flocculation for the recovery of 10

non-metalic minerals from slimes and feed materials of

non-uniform particle sizes including slimes, and in particular,

is a process for the recovery of phosphate from

phosphate ores which have not been subjected to desliming.

This invention provides an improved and simplified

process for the treatment of non-metallic minerals, particularly

phosphate, contained in an ore in which the 20

starting particle size of the ore for processing ranges

from about minus 20 mesh to colloidal size. Flocculation

and flotation are known methods for treating ores,

but non of the prior methods have been successful in

providing an economical and simplified method for 25

treating ore containing a significant fraction comprising

a fine particle size, e.g. less than about 10 microns.

In particular, phosphate ores contain substantial

quantities of very fine particles which renders treatment

and recovery of the desired phosphate difficult. In 30

known treatment methods for phosphate ore, the ore is

first sized and then separated into a sand fraction and a

waste slime portion. The particle size of the sand fraction

typically ranges from about minus 20 mesh to about

plus 150 mesh. The fine particles, minus 150 mesh down 35

to colloidal size, are the rejected waste slime portion.

This waste slime portion, containing approximately 10

to 40% of the phosphate contained in the starting ore

material, is discharged into environmentally undesirable

tailings ponds. Known methods of treating the slimes 40

have typically involved processing them after separation

from the larger sands. U.S. Pat. No. 4,235,709 discloses

a treatment by selective flocculation for the fine

fraction of phosphate ores. This patent teaches conditioning

the ore with sodium silicate prior to the addition 45

of water and a subsequent flocculation agent consisting

of a cellulose derivative. U.S. Pat. No. 2,660,303 teaches

a process of adding a sodium hydroxide dispersant to

the slime, followed by starch to selectively flocculate

the phosphate and recover it for separation. U.S. Pat. 50

No. 3,302,785 discloses a process for treating Tennessee

phosphate slimes by negative ion froth flotation followed

by desliming the tailings and combining the tailings

with the froth concentrate to provide an electric

furnace feed. The process is not applicable to Florida 55

phosphate slimes due to the lack of plus 325 mesh phosphate

agglomerates in the Florida slimes. A. F. Colombo

in "Dispersion-Flocculation Characteristics of

Florida Phosphate Slimes," a U.S. Bureau of Mines

report, discloses treating an alkaline, aqueous slurry 60

comprising phosphate waste slimes at pH 8.5 to 10 with

a dispersant and subsequently with a high anionic functionality

cornstarch as a flocculating agent to recover

60-70 percent of the phosphate product, upgraded 2 to

5 percent. None of the above references teaches the 65

advantage of utilizing an ore having a non-uniform

particle size as a feed material for selective flocculation

utilizing a nonionic flocculation agent. In addition, none

4,690,752

is used, then the pH of the solution is adjusted to a pH

of about 9 to 11, preferably around 10. After mixing the

slurry with the dispersant, a flotation collector such as

sodium oleate, vapor oil, or other collector known to

the art, is added to render the coarser ore particles 5

hydrophobic. Next, a selective hydrophobic flocculating

agent, preferably polyethylene oxide (PED), is

added to the slurry. The polyethylene oxide will selectively

agglomerate the finer ore particles and render

them hydrophobic. The non-metallic mineral concen- 10

trate is recovered in a froth concentrate after bubbling

air into the slurry following conventional froth flotation

procedures.

More specifically, the ore, suitable for obtaining the

desired non-metallic mineral, is conventionally pre- 15

pared by crushing and/or grinding typically to less than

minus 20 mesh. Preferably, the ore is ground to less than

minus 48 mesh. The particle size distribution of the

crushed ore will typically be about 78% minus 20 to

plus 150 mesh; and 22% minus 150 mesh. Alternatively, 20

the desired ore particle sizes may be generated by the

ore mining methods, or be due to the inherent physical

characteristics of the ore. For example, in conventional

Florida phosphate processing the phosphate is not typically

ground. Instead, the phosphate ore is sized by use 25

of a 20 mesh screen and a cyclone, and the ore size

typically utilized for processing is sand ranging in size

from minus 20 to plus 150 mesh, with the minus 150

mesh size slimes constituting reject tailings. In the

method of a preferred embodiment of this invention, 30

both the sands and the slimes constitute the starting ore

feed material.

The sized ore is then slurried with water or an aqueous

solution, the percentage of solids being preferably

between about 20 and 30%. The water used is prefera- 35

bly obtained from the slimes portion of the feed. Dispersants

are next added to the slurry, such as sodium silicate

and sodium hydroxide. As will be known and un-

. .. derstood by those skilled in the art, other dispersing

agents serving the same purpose may be used. This 40

dispersing agent is added in an amount sufficient to

promote uniform and maximum separation of the particles,

including the extremely fine particles, preferably in

a ratio of dispersant to solids from about 2 to about 5

Ibs/ton of ore and most preferably from about 2 to 45

about 3 lbs/ton of ore. The pH of the slurry should be

alkaline, preferably in the range of about 9 to 11, most

preferably at least about 10. The slurry is mixed for a

short period of time, preferably from about I to about 3

minutes, for a time sufficient to adequately mix all of the 50

reagents within the slurry.

A flotation collector is then added to the dispersed

mixture in an amount sufficient to render the coarser

ore particles hydrophobic for later flotation. Flotation

collectors known to the art, such as sodium oleate, 55

vapor oil, tall oil and the like are suitable, and are pref·

erably added at a ratio of collector to solids of between

about 0.5 and about 4lbs/ton of ore, and most preferably

between about 1 and about 2 lbs/ton of ore. Agitation

of the mixture is then conducted, preferably at high 60

speed, to ensure the coating of all ore particles capable

of being coated with the hydrophobic collector.

The conventional flotation collector does not completely

coat the fine particles of the slimes contained in

the slurry, however, and therefore a hydrophobic floc- 65

culating agent is selected for addition to the slurry at

this point. The hydrophobic flocculating agent is preferably

a high molecular weight nonionic polymer, most

preferably polyethylene oxide, which is added in an

amount sufficient to selectively flocculate or agglomerate

all the non-metallic mineral fines present. Flocculation

produces larger agglomerated fines of a particle

size range and chemical environment permitting recoveries

by froth flotation. Preferably the polyethylene

oxide is added at a ratio of flocculating agent to solids

from about 0.1 to about 2 Ibs/ton of ore, and most preferably

from about 0.3 to about 0.4 Ib/ton of dry ore.

This slurry is mixed gently so as not to break up the

formed floccules for a short period of time after the

addition of the polyethylene oxide.

Air is then bubbled through the mixture, preferably

for about 12 minutes at a rate of about 5 liters/minute to

selectively attach to the hydrophobic particles, and

form a froth concentrate containing the desired mineral

values. Phosphate recoveries in the rougher concentrate

of at least about 93% are achievable by the process

of this invention.

The dispersion, flocculation, and flotation steps are

performed preferably at ambient temperature and pressure.

In a preferred embodiment, the flocculation and flotation

steps are conducted in a continuous multiple stage

process.

Preferably the rougher flotation concentrate is

cleaned in at least two stages to produce a phosphate

concentrate having at least 66-67% BPL, with an overall

phosphate recovery of at least about 70%. Tailings

formed in the first cleaning stage can be recirculated to

rougher flotation or to final tailings.

Alternatively, in the methods according to this invention,

waste slime tailings can be added to the starting

feed material. Phosphate ore generally comprises approximately

80% sand to 20% slime. This invention

provides a process such that the slime percentage in the

starting phosphate ore feed material can be increased,

with the addition of tailings pond slime, for recovery of

the previously unrecoverable phosphate content.

In another embodiment of this invention, slurries

comprising only extremely fine ore particles, such as

Florida phosphate slimes unmixed with coarser ore

fractions, are treated by selective flocculation to recover

an upgraded phosphate product.

In the treatment of such slimes, the solid content is

adjusted, if necessary to between about 10 and about

30%, and most preferably between about 15 and about

25% solids.

A dispersing agent is then added, in an amount sufficient

to achieve separation of the fine particles, preferably

at a ratio of dispersant to solids of between about 5

and about 10 lbs/ton, and most preferably between

about 6 to about 8 lbs/ton. The dispersant should be a

low molecular weight polyacrylate such as Cyquest

3223, to avoid the effects of sodium dispersants in attracting

clay particles. The pH is adjusted to at least

about 10 with a pH adjusting agent such as potassium

hydroxide, and the mixture is agitated to disperse the

particles.

Next a flocculating agent is added comprising a high

molecular weight anionic polymer such as Separan MG

500, a polyacrylamide product ofDow Chemical Company.

The flocculating agent is added in an amount

sufficient to agglomerate a major portion of the fine ore

particles, preferably at a ratio of flocculating agent to

solids of between about 0.1 and about 1.0 lbs/ton of

slimes, more preferably between about 0.3 and about 0.5

Ibs/ton of slimes. The mixture is gently agitated for a

As used with these Examples, slimes are feed material

described as minus 150 mesh (Tyler screen sieve). The

sands are feed material described as minus 20 to plus 150 40

mesh.

Typical particle sizing for phosphate slimes is 95%

minus 20 microns, 85% passing 10 microns, and 60-70%

finer than 1 micron. Phosphate distributions are of like

percentages since the concentration of P205 tends to be 45

uniform across the particle size range. The slimes may

be considered as essentially colloidal.

EXAMPLE 2

EXAMPLE 3

A series of tests were conducted to evaluate the effect

of varying the slimes concentration in the starting feed

ore on phosphate recovery. The percentage of slimes in

the starting feed ore was varied utilizing 90/10, 80120,

70/30, and 60/40 sands/slimes ratios.

For a baseline control, each varying starting feed ore

was tested both by the flocculation and flotation process

as described in Example 1, and by conventional

flotation processing. Table 1 illustrates the results attained

from this test.

Testing was done to evaluate the effect on phosphate

recovery when the starting feed ore constituted 80% by

weight sands (minus 20 to plus 150 mesh) and 20% by

weight slimes (minus 150 mesh). 700 grams of the material

were slurried to a pulp density of 25% solids and

sodium silicate was added as a dispersant in the amount

of 3 Ibs/ton of ore. A flotation collector consisting of

sodium oleate was then added in the amount of 1 to 2

Ibs/ton of ore, and the slurry was vigorously agitated.

PEO was then added in the amount of 0.3 to OAlbs/ton

of ore, and after gentle mixing, air was bubbled into the

mixture and the rough froth concentrate collected.

In the first rough phosphate concentrate of the flotation

process, before cleaning, the phosphate recovery

was 79%. After cleaning of the concentrates by the

methods described above, the final product assayed

65% BPL (bone phosphate of lime) with a recovery of

20 68% phosphate.

Additional testing was done using the same test procedures

and starting ratios of feed material with the

variation of grinding of the plus 48 mesh fraction of the

ore sand feed to provide better liberation of the locked

25 quartz/fluorapatite particles. This testing produced

phosphate recoveries of as much as 93% in the rougher

phosphate concentrates. The cleaned product assayed

67% BPL, with a phosphate recovery of 70%.

Assay/size analysis showed in a very high recovery

of phosphate from all particle sizes, particularly in the

minus 400 mesh slime range where the recovery of

phosphate was over 92%. Study of the kinetics of phosphate

flotation showed that the flocculated phosphate

slimes were consistently recovered preferably ahead of

the individual phosphate grains.

4,690,752

Wt% Composition

20-25 CaJQ(p04.C03l6P2_3

30-35 Si02

20-25 (Fe.AI,Mgh(AI.Sil4

OJQ(OHh(Ca.Nal 30

5-10 (Mg.Al.Fe)s(AI.Sil60 20

(OHh8H20

4-6 AI3(OH13(P04125H20

2-3 KAlSi30g + NaAISi30g

0-3

Mineral

short period of time, preferably about 3 minutes, to

allow the agglomerates to form, but not subsequently

break up.

The slurry is then allowed to settle for a short period

oftime, typically from a few minutes to about one-half 5

hour, while the phases disengage, and movement within

the slurry is stopped.

At this point the disengaged slimes may optionally be

siphoned off the top of the mixture. Typically about

two-thirds of the water and up to 60% alumina is re- 10

moved with the slimes. The flocculated phase, typically

containing about 20-30% solids, remains in the lower

portion of the mixture.

An upgraded phosphate product is then recovered by

flotation methods from the flocculated phase.

Alternatively, the flocculated mixture is not deslimed,

but is treated by conventional froth flotation

methods to recover a high phosphate froth concentrate.

The following examples are by way of illustration,

not by way of limitation.

EXAMPLE 1

The feed material used in Examples 1 through 6 was

analyzed, with results shown in Table 1.

TABLE 1

Attapulgite

Carbonate-fluorapatite

Quartz

Montmorillonite

Wavellite

Feldspar

Others (zircon. garnet.

rutile. kaolinite.

iron oxide. organics)

TABLE 1

Sandi Cleaner Concentrate Rougher Concentrate Tailings

Slime Test BPL BPL BPL

Weight Conditions Wt% % BPL Recovery % Wt% % BPL Recovery % % BPL Distribution. %

100 Conventional 16.6 66.1 48.6 27.4 44.9 54.3 4.91 30.00

100 Conventional 14.0 44.9 25.8 35.0 32.6 46.7 20.1 53.3

90/10 Conventional 7.5 47.6 21.5 13.0 39.0 30.6 t3.3 69.4

90/10 Flocculation 18.0 67.1 68.2 25.2 55.7 79.1 4.96 20.9

80120 Conventional 10.2 39.7 22.3 23.9 30.9 40.5 14.3 59.5

80120 Flocculation 18.9 64.9 68.8 36.3 77.3 78.6 6.77 21.4

80120 Flocculation 17.5 66.5 70.1 42.2 36.7 92.6 2.42 7.4

80120 Flocculation 52.7 31.1 95.7 1.60 4.3

70/30 Conventional 10.3 39.7 22.3 23.9 30.9 40.5 14.3 59.5

70/30 Flocculation 49.6 24.1 65.6 70.1 21.5 82.7 10.6 17.3

60/40 Conventional 12.9 35.4 23.8 28.2 30.1 44.2 15.0 55.8

60/40 Flocculation 52.8 22.7 64.6 68.6 22.2 82.0 10.7 18.0

Typical particle sizing for the sands is minus 20 mesh

by 150 mesh.

65 EXAMPLE 4

The starting feed was 200 grams of phosphate slimes

of minus 150 mesh. The feed was mixed with deionized

water to a pulp density of 15% solids, and 61bs/top of

4,690,752

ore of Cyquest 3223 as a dispersing reagent was added

to the mixture. The pH was adjusted to about 10. The

slurry was mixed for 3 minutes with moderate shear

force. Next, 0.4 lbs/ton of Separan MG 500 was added

as a flocculating agent. The flocculant was mixed in 5

with the slurry for a short period of time sufficient to

allow complete mixing, and then the solution was allowed

to settle and the two phases to separate. The two

phases were a top layer slime phase, comprising fine

clay particles, and a lower concentrate phase, compris- 10

ing the phosphate floccules. The slime phase was removed

as waste and not further processed.

Five consecutive selective flocculation and desliming

stages were conducted. The flocculated concentrate

assayed 30% BPL with a recovery of phosphate of over 15

81%. The combined five slime products (waste) represented

44 weight percent and assayed 8.7% BPL (equivalent

to 4% P205). This indicated a large increase in the

rejection of clay slimes (over 25% rejection previously

obtained with only one flocculating and desliming 20

stage) and a corresponding increase in phosphate upgrading

in the flocculated phase. The selectivity of

flocculation of phosphate fines from clays was, therefore,

increased by prolonged and repeated contact of

the flocculant with slimes. 25

The test products were analyzed for various elements

to determine the distribution of the major minerals in

selective flocculation. The results, presented in Table 2,

show that approximately 60% of the alumina (clays)

and silica (quartz, feldspars) gangue constituents were 30

rejected to the waste slime by selective flocculation.

Between 78 and 83% of calcium and fluorine constituents

of the phosphate mineral, fluropatite, reported to

the flocculated concentrate. This is consistent with the

81% BPL recovery in this product.

TABLE 2

feed. Phosphate recoveries in the conventional and

column tests, respectively, were 55% and 44% from the

original slimes feed which assayed 20% BPL.

A further test was conducted with flocculation but

without desliming of the clays prior to flotation to determine

the effect of clay slimes removal on phosphate

flotation. This gave only marginal phosphate upgrading

and very poor recoveries.

What is claimed is:

1. A process for separating an upgraded phosphorus

ore from an aqueous slurry containing said phosphorus

ore comprising particles from about minus 20 to about

minus 150 mesh, comprising:

(a) contacting the slurry at a pH of at least about 10

with a dispersing agent selected from the group

consisting of sodium silicate, sodium hydroxide and

polyacrylate in an amount sufficient to achieve

dispersion in the slurry of substantially all the ore

particles;

(b) contacting the dispersed mixture of step (a) with a

flotation collector in an amount sufficient to coat

and render hydrophobic substantially all the ore

particles capable of being coated therewith;

achieve said coating;

(d) contacting the mixture of step (c) with a hydrophobic

nonionic polyethylene oxide in an amount

sufficient to cause the agglomeration of substantial

portions of the fine particles of about minus 150

mesh;

(e) gently mixing the mixture of step (b) to provide

dispersion of the polyethylene oxide of step (d) and

form said agglomerates without significantly

breaking up said agglomerates;

(t) subjecting the mixture of step (e) to froth flotation

Weight Distribution, %

Product % BPL Ca H2C03 CO2 F Mg AI203 Si02

Flocculated conc 56.23 81.4 83.3 79.3 91.3 78.5 65.7 41.3 43.8

5th Slime 7.62 3.9 3.7 4.4 2.4 4.5 6.6 9.8 9.6

4th Slime 9.76 4.0 3.5 4.5 2.2 4.7 7.8 13.0 12.9

3rd Slime ILl5 3.8 3.5 4.5 1.6 4.5 8.9 15.2 14.5

2nd Slime 9.48 3.3 2.9 4.2 Ll 4.0 7.2 13.3 12.2

1st Slime 5.76 3.6 3.1 3.1 1.4 3.8 3.8 7.4 7.0

Head (calc) 100.00 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

Combined slimes 43.77 18.6 16.7 20.7 8.7 21.5 34.3 58.7 56.2

EXAMPLE 6

EXAMPLE 5

The multiple stage selective flocculation process of

Example 4 was reproduced on another similar sample of 50

phosphate slimes from a Florida operation. After four

stages of selective flocculation and desliming, the flocculated

concentrate assayed 32% BPL with a phosphate

recovery of over 82%. The total slimes rejected

assayed 14% BPL at a weight rejection of 32%, The 55

higher BPL assay of the slime reject reflected the 26%

BPL head assay of this sample in contrast to about 20%

BPL for the previous sample.

Two flotation tests of the highly agglomerated phosphate

fines of Example 5 were conducted using a conventional

mechanical flotation machine and a column

aspirated with finely divided air bubbles. The tests used

a conventional fatty acid and vapor oil collector 65

scheme, but the mechanical test also used PEO prior to

flotation. The froth products, which assayed 35% BPL,

were only slightly higher than the 30% BPL flotation

by the addition of gas bubbles thereto;

(g) separating the phosphorus-rich froth concentrate

from the mixture of step (t).

2. The process according to claim 1 in which the

particle size of said ore ranges from about 500 to about

10 microns.

3. The process according to claim 1 jn which the

solids to solution ratio in said aqueous slurry is between

about 10% and about 30%.

4. A process for recovering a phosphorus ore upgraded

by at least about 5% phosphate content from a

phosphate slime containing clays and said phosphorus

ore comprising particles of about minus 150 mesh in an

aqueous slurry of a ratio of solids to liquids of between

about 10% and about 30%, comprising:

(a) adjusting the pH of said aqueous slurry to a pH of .

at least about 10;

(b) contacting said slurry with a dispersing agent

selected from the group consisting of sodium silicate,

sodium hydroxide and polyacrylate in an

hydrophobic substantially all of the ore particles

capable of being coated therewith;

(0 subjecting said concentrate phase to froth flotation

by the addition of gas bubbles thereto; and

(g) separating the phosphorus-rich froth concentrate

from said concentrate phase.

5. The process of claim 4 in which the dispersing

agent is a low molecular weight polyacrylate.

6. The process of claim 4 in which phosphate is re10

covered from particles of from about 10 microns to

about 500 microns in size.

* * * * *

4,690,752

amount sufficient to disperse the fine particles in

the slurry;

in an amount sufficient to agglomerate a

substantial portion of the fine ore particles to the 5

exclusion of the clay particles;

(d) allowing the mixture of step (c) to separate into an

upper slime phase and a lower flocculate concentrate

phase;

(e) contacting the concentrate phase with a flotation

collector in an amount sufficient to coat and render