Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR RECOVERING MINERAL PARTICLES,
METAL PARTICLES OR SMALL PRECIOUS STONES
FROM AN AC~UEOUS 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
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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
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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 deflocculated 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
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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.
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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
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a health risk due to its fibrous and silky characteristics) which
creates flocs 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.
1000g 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.
deflocculated, after mixing. The deflocculated 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.
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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.
1000g 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.
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10008 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.
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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.
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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.
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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
