WO2000061824A2

WO2000061824A2 - Process for recovering particles suspended in an aqueous slime

Info

Publication number: WO2000061824A2
Application number: PCT/CA1999/000330
Authority: WO
Inventors: Roberto Berardi; David Krofchak; Peter A. C. A. Howe; David M. Howe
Original assignee: Ateba Mines Inc
Current assignee: Ateba Mines Inc
Priority date: 1999-04-09
Filing date: 1999-04-09
Publication date: 2000-10-19
Anticipated expiration: 2001-10-09
Also published as: AU3402899A; WO2000061824A3; CA2368876A1

Abstract

A process for recovering mineral particles, metal particles or small precious stones from an aqueous slime associated with an ore body or mineral deposit or processing thereof, said aqueous slime containing mineral particles, metal particles or small precious stones in suspension with slime particles. The process includes adding a sufficient amount of deflocculating agent to the aqueous slime to cause deflocculation of the slime particles and produce a deflocculated suspension containing the mineral particles, metal particles or small precious stones. The deflocculated suspension is allowed to settle, and the settled material containing the mineral particles, metal particles or small precious stones is recovered.

Description

PROCESS FOR RECOVERING MINERAL PARTICLES.

METAL PARTICLES OR SMALL PRECIOUS STONES

FROM AN AQUEOUS SLIME ASSOCIATED WITH AN ORE

BODY OR MINERAL DEPOSIT OR PROCESSING THEREOF

FIELD OF THE INVENTION

This invention relates to the recovery of mineral particles,

metal particles or small precious stones from aqueous slimes

containing such particles in suspension with slime particles. The

metal particles may for example be precious metal particles, and the

small precious stones may for example be diamonds, sapphires or

rubies.

In particular, this invention is concerned with the

treatment of any ore body or mineral deposit without regard to

mode of origin, of any mineral or metal or small precious stones, in

which slime particles are present or formed during the processing of

the ore body or mineral deposit.

The term "slime" as used in this application includes any

detrital mineral particles of any composition having a diameter less

than about 4 microns. This is approximately the upper size limit of

particles which can show colloidal properties. Examples of such

particles are any earthy extremely fine-grained sediment or soft rock

composed primarily of clay-size or colloidal particles and having

high plasticity and a considerable content of clay minerals, any wet adhesive earth material, such as mud, any clay minerals composed of

essentially hydrous aluminum silicates or hydrous magnesium

silicates with extremely small particle size which imparts ability to

absorb water and ion on the particle surfaces, or any particles of any

shape or size which can cause flocculation in an aqueous suspension

or solution.

BACKGROUND OF THE INVENTION

In many cases, the production of a concentrate from an

ore involves complex steps which include crushing and grinding the

ore in a wet mill and separating the concentrate from the tailings

through various mechanical, physical or chemical steps (such as

screening, gravity separation or flotation, etc.). A large amount of

water is used in all these steps. Although the procedure works fairly

well, it has been found that, when the ore is crushed and ground in

the mill, very fine particles (slime) are produced and liberated. Such

slime particles have distinctive physical-chemical properties which

interfere with the recovery process because they encapsulate,

sometimes in clay balls, appreciable quantities of minerals, metals or

small precious stones which are lost in reject tailings.

So far as is known, this problem has not yet been solved

in a cost-effective manner. Attempts have been made to solve the

problem by massive dilution with water or separate processing of clay balls. However, both of these procedures are expensive and

time consuming.

It is therefore an object of this invention to provide a

process for the recovery of mineral particles, metal particles or small

precious stones from aqueous slimes containing such particles in

suspension with slime particles which substantially eliminates the

problem described above.

SUMMARY OF THE INVENTION

The present invention is based on the discovery that slime

particles can be separated from the metal or mineral particles or

small precious stones by means of a deflocculating agent.

According to the invention, a sufficient amount of

deflocculating agent is added to cause deflocculation of the slime

particles. The defiocculated suspension is allowed to settle, and the

settled material containing the mineral or metal particles or small

precious stones is recovered.

The aqueous slime may contain from about 0.5 to about

90% slime particles by weight. The slime particles may comprise

detrital mineral particles having a diameter of less than about 4

microns. The slime particles may comprise earthy extremely fine¬

grained sediment or soft rock composed primarily of clay-size or

colloidal particles having high plasticity and a considerable content of clay minerals. The slime particles may comprise wet adhesive

earth material such as mud or clay minerals composed essentially of

hydrous aluminum silicates or hydrous magnesium silicates with

extremely small particle size which imparts ability to adsorb water

and ions on the particle surfaces. The slime particles may comprise

particles of a shape or size which can cause flocculation in an

aqueous suspension or solution.

The deflocculating agent may comprise an alkali

compound of a phosphorous oxide, the weight of deflocculating

agent added may be from about 0.01 to about 10% by weight of the

dry weight of the slime.

The ore body or the mineral deposit may comprise a

sedimentary, igneous, metamorphic or hydrothermal deposit. The

small precious stones may comprise diamonds, sapphires, rubies,

emeralds or aquamarines. The metal particles comprise precious

metal particles of gold, silver or any of the platinum group.

The aqueous clay suspension may contain from 1 to about

40% clay by weight, and the deflocculating agent may comprise

sodium tripolyphosphate.

The weight of sodium tripolyphosphate added may be

from about 0.03 to about 1% of the dry weight of clay in the

suspension. The precious metal particles may comprise gold particles.

The gold particles may be of a size in the range from

about 0.1 to about 5 millimetres.

The precious stones may comprise diamonds.

The diamonds may have a diameter in the range of from

about 0.5 to about 10 millimetres. The precious stones may

comprise sapphires.

The sapphires may have a diameter in the range from

about 0.5 to about 30 millimetres. The precious stones may

comprise rubies. The rubies may have a diameter in the range of

from about 0.5 to about 30 millimetres.

DESCRIPTION OF PREFERRED EMBODIMENTS

The manner in which the deflocculating agent can be

added to the slime will be readily apparent to a person skilled in the

art, and specific examples of the invention will now be described.

EXAMPLE 1

A composite sample of a serpentinite ore body from

Ontario, Canada was obtained, and was found to contain lizardite,

chrysotile and magnetite as main components. For commercial

reasons, it is useful to separate the lizardite (used in automobile

brake pads etc.) and the magnetite (used in various industries such as

copy machines etc.) fraction from the chrysotile fraction (considered a health risk due to its fibrous and silky characteristics) which

creates floes with the magnetite and the lizardite. Under a

stereomicroscope, it was observed that the lizardite and the

magnetite were attached to the fibrous particles of the chrysotile.

To date, no commercially useful method to separate these three

components has been found.

lOOOg of the sample were put in water, and a thick

flocculated clay-like slime was produced. A 5% solution of sodium

tripolyphosphate was added to the slime which liquified, i.e.

defiocculated, after mixing. The defiocculated suspension was then

allowed to settle for 5 minutes. The chrysotile remained in

suspension, while the lizardite and magnetite settled. The chrysotile

(73.3% of the original sample) was poured into a receptacle, and was

thereby separated from the lizardite (22.9%) and the magnetite

(3.8%). The lizardite and the magnetite were separated from each

other by a magnetic method.

The water and the sodium tripolyphosphate solution were

recovered and reused for other tests, with similar results, namely

72.6% chrysotile, 23.7% lizardite and 3.7% magnetite in one further

test, and 72.9% chrysotile, 22.9% lizardite and 4.2% magnetite in yet

another test. EXAMPLE 2

A composite sample of bentonitic black shale with up to

30% Iron-sulphide species was obtained from Alberta, Canada. The

rock was very fine and nearly equigranular. This factor may have

caused serious problems in concentration by flotation because, after

flotation, all the concentrates had the same composition (major and

minor elements as well as metals etc.) as the feed material, with

there therefore being no actual concentrate.

lOOOg of the sample were put in water, and it was observed

that the bentonitic fraction did not allow settling and thus

separation of the sulfide fraction. A 5% solution of sodium

tripolyphosphate was added, and the flocculated suspension liquified

after mixing. Virtually all the bentonitic fraction remained in

suspension, while the sulfide fraction settled. The bentonitic

fraction (54.3% of the original sample) was then poured into a

receptacle, and the sulfide fraction (45.7%) was then recovered.

EXAMPLE 3

A composite sample of clay balls (composed mainly of

clay, sand and phosphate) was obtained from the discharged outlet

of a phosphate plant in Florida, U.S.A. Various attempts in

accordance with prior art techniques were made to separate the clay

fraction, but none was successful. lOOOg of the sample were put in water, and a 5% solution

of sodium tripolyphosphate was added. Immediately after mixing,

the clay balls broke down, leaving in suspension the clay fraction

(38.7%) was poured into receptacle, and the phosphate and sand

fraction (61.3%) which had settled was recovered.

EXAMPLE 4

A sedimentary material from Rancheria, California, U.S.A.

contained gold and various silicate compounds and clays, some of

which had undergone a metamorphism. After this material had

been mined, crushed and wet screened, the recovery of gold in a

conventional manner was between 45 and 80%. Oversize (reject)

material was collected from the trommel whose aperture size was

0.25 inches. 78 lbs. of this reject material, consisting of 63 lbs. of

clay balls and 15 lbs. of cemented gravel of fine gold-bearing placer

material was placed in a small concrete mixer. A 5% aqueous

solution of sodium tripolyphosphate was added in accordance with

the invention in an amount such that the weight of sodium

tripolyphosphate was 0.4% of the dry weight of the contained clays.

The mixture was agitated in the concrete mixer for two hours at a

very slow rotation speed. After such agitation, the liquid was

decanted off, and the remaining solid material (settled sediment) was

dried and weighed. The dry weight of the sediment was 38 lbs., indicating that

40 lbs. of water and light sediment material had been removed from

the original 78 lb. sample. All of the clay balls and about 90% of

the cemented gravel has disintegrated. The sediment was then

processed in a conventional manner for gold recovery, and about

150 specks of fine gold with a size of about 0.1 to 0.5 mm were

observed on the wilfley table. The gold specks were recovered and

were found to be 92% of the gold reject material.

EXAMPLE 5

At the same site as in Example 1, five 50 gallon drums of

clay ball material were collected from the trommel. A 5% aqueous

solution of sodium tripolyphosphate was added in an amount such

that the weight of sodium tripolyphosphate was 0.4 % of the dry

weight of the clay. The drums were covered, and their contents

allowed to stand for one week.

The drum contents were then processed for gold recovery

using standard mechanical techniques, but using the sodium

tripolyphosphate solution as a medium. The clay balls has

disintegrated and specks of gold with a size of about 0.1 mm were

observed on the wilfley table. The gold was recovered and found to

represent 80% of the gold in the clay ball material collected from

the trommel. EXAMPLE 6

Ore processed in a Costa Rica gold mine contained up to

30% clay by weight. The ore was pulped in water and then

processed through cyanidation vats. Considerable problems were

encountered with clay causing gold particles with a size of about 0.1

mm to be held in suspension with the clay. This problem could

have been overcome by substantially diluting the clay with water,

but such a procedure would hydraulically overload the plant and

reduce its throughput. Sodium tripolyphosphate with a weight of

0.5% of the dry weight of the clay was added in a 5% aqueous

solution in accordance with the invention, and it was found that the

clay substantially ran at the viscosity of water, allowing the gold

particles to settle out and the liquid clay to separate.

EXAMPLE 7

Three similar laboratory tests were carried out using three

types of precious stones, namely diamonds, sapphires and rubies.

In the first test, 160 grams of clay from a Costa Rica mine

were placed in a beaker, the viscosity of the clay being about 40

centipoises. Ten diamonds, each about 1 mm in diameter, were

added and the contents stirred to produce a clay suspension. The

contents were then poured into another beaker. Remaining

contents in the first beaker were diluted with water and examined. No diamonds had remained behind, i.e. all the diamonds had

become entrained in the clay suspension. 5 ml of a 10% aqueous

solution of sodium tripolyphosphate was then added to the contents

of the second beaker, the weight of sodium tripolyphosphate being

0.1% of the dry weight of the clay in accordance with the invention.

The mixture was agitated and then left standing for 30 seconds. The

clay had become very liquid with a viscosity of about 5 centipoises

and was decanted off, leaving the solid material in the bottom of the

beaker. All ten diamonds were recovered in the settled out material.

The test was repeated with ten sapphires of about 2 mm

diameter, and these were easily removed in the same way as the

diamonds. The test was again repeated with ten rubies of about 2

mm diameter, again with similar results.

Other examples and embodiments of the invention will be

readily apparent to a person skilled in the art, the scope of the

invention defined in the appended claims.

04091000.9pa

Claims

1. A process for recovering mineral particles, metal particles

or small precious stones from an aqueous slime associated with an

ore body or mineral deposit or processing thereof, said aqueous

slime containing mineral particles, metal particles or small precious

stones in suspension with slime particles, the process including:

adding a sufficient amount of deflocculating agent to the

aqueous slime to cause deflocculation of the slime particles and

produce a deflocculated suspension containing the mineral particles,

metal particles or small precious stones,

allowing the deflocculated suspension to settle, and

removing settled material containing the mineral particles,

metal particles or small precious stones.

2. A process according to claim 1 wherein the aqueous slime

contains from about 0.5 to about 90% slime particles by weight.

3. A process according to claim 2 wherein the slime particles

comprise detrital mineral particles having a diameter of less than

about 4 microns.

4. A process according to claim 1 wherein the slime particles

comprise earthy extremely fine-grained sediment or soft rock

composed primarily of clay-size or colloidal particles having high

plasticity and a considerable content of clay minerals.

5. A process according to claim 1 wherein the slime particles

comprise wet adhesive earth material such as mud or clay minerals

composed essentially of hydrous aluminum silicates or hydrous

magnesium silicates with extremely small particle size which imparts

ability to adsorb water and ions on the particle surfaces.

6. A process according to claim 1 wherein the slime particles

comprise particles of a shape or size which can cause flocculation in

an aqueous suspension or solution.

7. A process according to claim 1 wherein the deflocculating

agent comprises an alkali compound of a phosphorous oxide.

8. A process according to claim 7 wherein the weight of

deflocculating agent added is from about 0.01 to about 10% by

weight of the dry weight of the slime.

9. A process according to claim 1 wherein the ore body or

the mineral deposit comprises a sedimentary, igneous, metamorphic

or hydrothermal deposit.

10. A process according to claim 1 wherein the small precious

stones comprise diamonds, sapphires, rubies, emeralds or

aquamarines.

11. A process according to claim 1 wherein the metal particles

comprise precious metal particles of gold, silver or any of the

platinum group.

12. A process according to claim 1 wherein the aqueous clay

suspension contains from about 1 to about 40% clay by weight.

13. A process according to claim 12 wherein the deflocculating

agent comprises sodium tripolyphosphate.

14. A process according to claim 13 wherein the weight of

sodium tripolyphosphate added is from about 0.03 to about 1% of

the dry weight of clay in the suspension.

15. A process according to claim 1 wherein the precious metal

particles comprise gold particles.

16. A process according to claim 15 wherein the gold particles

are of a size in the range of from about 0.1 to about 5 millimetres.

17. A process according to claim 1 wherein the precious stones

comprise diamonds.

18. A process according to claim 17 wherein the diamonds

have a diameter in the range of from about 0.5 to about 10

millimetres.

19. A process according to claim 1 wherein the precious stones

comprise sapphires.

20. A process according to claim 19 wherein the sapphires

have a diameter in the range from about 0.5 to about 30 millimetres.

21. A process according to claim 1 wherein the precious stones

comprise rubies.

22. A process according to claim 21 wherein the rubies have a

diameter in the range of from about 0.5 to about 30 millimetres.