SULFIDE FLOTATION AID
Cross-Reference to Related Applications
This application is a PCT application that claims priority to U.S. Application
Serial No. 12/706,091, filed February 16, 2010.
Statement Regarding Federally Sponsored Research or Development
Not Applicable.
Background of the Invention
This invention relates to methods compositions, and apparatuses for improving the
effectiveness of froth flotation separation processes. Froth flotation separation is a
technique commonly used in the mining industry for separating various mineral
constituents from ores. Examples of this method are described in US Patent 6,827,220, in
textbook chapters: of Mineral Processing Technology , 6th Edition, by Barry A. Wills,
(Published by Butterworth Heinemann), (2003) and 9 of The Chemistry of Gold
Extraction, 2nd Edition, by John Marsden and C. Iain House, (Published by SME),
(2006), and in the scientific papers: Industrial experiences in the evaluation of various
flotation reagent schemesfor the recovery of gold, by R. R. Klimpel, Minerals &
Metallurgical Processing, Vol. 16 No. 1 (1999) and The Flotation of Gold Bearing Ores-
A Review, by C. T. Connor and R. C. Dunne, Minerals Engineering, Vol. 7 No. 7 (1994).
In preparation for flotation, the ore is comminuted (ground up by such techniques
as dry-grinding, wet-grinding, and the like) and then dispersed in water to form a
suspension known as pulp. Additives such as collectors are normally added to the ore
bearing suspension, frequently in conjunction with frothers and optionally other auxiliary
reagents such as regulators, depressors (deactivators) and/or activators, in order to
enhance the selectivity of the flotation step and facilitate the separation of the valuable
mineral constituents) from the unwanted gangue constituents. The pulp is conditioned by
these reagents for a period of time before a gas, typically air, is sparged into the
suspension to produce bubbles of the gas. Minerals that adhere to the bubbles as they rise
to the surface are thereby concentrated in the froth that accumulates at the surface of the
aerated pulp. The mineral-bearing froth is skimmed or otherwise removed from the
surface and processed further to obtain the desired minerals.
The beneficiation of ores by froth flotation utilizes differences in hydrophobicity of
various components of a suspension, and these differences in hydrobphobicity may be increased
or decreased by judicious choice of chemical additives. In one form, the collector is a
hydrophobic agent, which is selectively engaged to the surface of a particular ore constituent and
increases the hydrophobicity of the mineral. Gas bubbles admitted during the aeration step will
preferentially adhere to the hydrophobicized mineral constituent. Because the mineral
components have been treated or modified with the collector, they exhibit sufficiently increased
hydrophobicity to be more readily removed from the aerated pulp by the bubbles than are other
constituents which are less hydrophobic or hydrophilic. As a result, the collector efficiently pulls
the particular ore constituent out of the aqueous solution while the remaining constituents of the
ore, which are not modified by the collector, remain suspended in the aqueous phase. This
process can also or instead utilize chemicals, which increase the hydrophilic properties of
materials selected to remain suspended within the aqueous phase.
In direct flotation processes, the desired mineral which is concentrated and enriched in the
froth at the surface of the flotation cell is referred to as the concentrate. The portion of the
suspension that does not float is comprised predominantly of gangue minerals of the ore and is
referred to as the tails. These tails are often discarded as mine tailings. In reverse flotation
processes, the gangue constituent is floated into the concentrate and the desired constituent
remains suspended in the slurry. In either type of flotation process, the object of the flotation is
to separate and recover as much of the valuable mineral constituent(s) of the ore as possible in as
high a concentration as possible which is then made available for further downstream processing
steps such as thickening, filtration, and roasting.
A number of materials are known to be useful in facilitating froth flotation separation
processes. Collectors based on fatty acids have long been used in collecting one or more of the
oxide minerals such as fluorspar, iron, chromite, scheelite, CaC0 3,Mg C0 3, apatite, or ilmenite.
Neutralized fatty acids are soaps that have been shown to operate as non-selective flotation
collectors. Petroleum-based oily compounds such as diesel fuels, decant oils, and light cycle oils,
are often used to float molybdenite.
Of particular interest to the mining industry are collectors especially effective at
selectively floating sulfide mineral ore constituents which comprise complexes with valuable
metals including gold, silver, copper, lead, zinc, molybdenum, nickel, platinum, palladium, and
other metals. US Patent 7,553,984 teaches that organic molecules containing sulfur are useful
compounds for the froth flotation of sulfide minerals.
Organic compounds containing sulfur, such as xanthates, xanthogen formates,
thionocarbamates, dithiophosphates, and mercaptans, will selectively collect one or more sulfide
minerals such as chalcocite, chalcopyrite, galena, or sphalerite. Such sulfur-based collectors are
usually grouped into two categories: water-soluble and oily (i.e., hydrophobic) collectors. Watersoluble
collectors such as xanthates, sodium salts of dithiophosphates, and
mercaptobenzofhiazole have good solubility in water (at least 50 gram per liter) and very little
solubility in alkanes. Oily collectors, such as zinc salts of dithiophosphates, thionocarbamates,
mercaptans, xanthogen formates, and ethyl octylsulfide, have negligible solubility in water and
generally good solubility in alkanes.
Currently used collectors for most sulfide minerals are sulfur-based chemicals such as
xanthates, xanthogen formates, thionocarbamates, dithiophosphates, or mercaptans. All of these
prior art methods however do not provide optimal recovery rates of the desired minerals and thus
there remains a need for improved methods, compositions, and apparatuses for the selective
flotation collection of sulfide minerals.
Brief Summary of the Invention
At least one embodiment of the invention is directed towards a method of improving the
removal of a particular material from a comminuted sulfide mineral ore by a flotation separation
process. The method comprises the steps of: providing an aqueous suspension of the
comminuted ore, adding an effective amount of an organophosphorus compound to the
suspension, affording the organophosphorus compound sufficient residence time in the
suspension, selectively floating the particular material by sparging the suspension to form a
concentrate and a slurry, and recovering the particular material as either concentrate or slurry.
The organophosphorus compound is comprised of a substance selected from the group consisting
of a PAPEMP, in acid or salt form; a trialkanolamine triphosphate ester), in acid or salt form; an
amino tri(methylene phosphomc acid), in acid or salt form; a polyethylene amine polyphosphonic
acid, in acid or salt form; and combinations thereof.
The flotation process can be a normal flotation process in which the desired material
forms a concentrate at the top of the suspension. The method can further comprising the step of
adding a frother, a collector, lead nitrate, copper sulfate, and any combination thereof to the
suspension. The particular material can be a precious metal or a base metal selected from the list
consisting of: gold, silver, copper, lead, zinc, molybdenum, nickel, platinum, palladium, and any
combination thereof. The method can occur within a metal refining operation in which the
addition of the organophosphorus compound during the flotation separation process increases the
yield of the refined metal by a range of between 1-70% when all other steps in the refining
process are controlled for.
Detailed Description of the Invention
For purposes of this application the definition of these terms is as follows:
"Base metal" means a valuable metal selected from the list consisting of copper, lead,
zinc, molybdenum, nickel, and any combination thereof.
"Collector" means a composition of matter that selectively adheres to a particular ore
constituent and facilitates the adhesion of the particular ore constituent to the micro-bubbles that
result from the sparging of an ore bearing aqueous suspension.
"Comminuted" means powdered, pulverized, ground, or otherwise rendered into fine
particles.
"Concentrate" means the portion of a comminuted ore which is separated by flotation and
collected within the froth.
"Frother" means a composition of matter that enhances the formation of the microbubbles
and/or preserves the formed micro-bubbles bearing the fine hydrophobic mineral fraction
that results from the sparging of an ore bearing aqueous suspension.
"PAX" means potassium amyl xanthate.
RAREMR" means a polyamino methylene phosphonate that is:
a) of the formula:
where n is an integer or fractional integer which is, or on average is, from about 2 to about 12,
inclusive; M is hydrogen or a suitable cation; and each R may be the same or different and is
independently selected from hydrogen and methyl, a preferred subclass of compositions of the
above formula is that wherein M is hydrogen, R is methyl, and n is from about 2 to about 3, most
preferably an average of about 2.6, and/or
b) one or more of the molecules structurally related to the above polyamino
methylene phosphonate that are described in US Patent 5,368,830 as useful in scale control.
"Precious metal" means a valuable metal selected from the list consisting of gold, silver,
platinum, palladium, and any combination thereof.
"Supplemental Flotation" means at least one additional froth flotation separation process
performed on an ore containing more than one desired material, which is performed after at least
some of the gangue constituent has been substantially removed from the ore material by a
previous froth flotation separation process, and is performed to separate at least one of the desired
ore materials from another.
"Slurry" means the portion of a medium that contained comminuted ore that has
undergone gas sparging that is below the concentrate.
"Sparging" means the introduction of gas into a liquid for the purpose of creating a
plurality of bubbles that migrate up the liquid.
"Sulfide mineral ore" means an ore comprising at least one metal which forms a complex
comprising a covalently bonded crystal structure between the metal and sulfur ions, it includes
but is not limited to pyrite, arsenopyrite, pyrrhotite, stilbnite, chalcopyrite, bornite, chalcocite,
covellite, galena, sphalerite, molybdenite, the metal includes but is not limited to base metals and
precious metals.
In the event that the above definitions or a description stated elsewhere in this application
is inconsistent with a meaning (explicit or implicit) which is commonly used, in a dictionary, or
stated in a source incorporated by reference into this application, the application and the claim
terms in particular are understood to be construed according to the definition or description in
this application, and not according to the common definition, dictionary definition, or the
definition that was incorporated by reference. In light of the above, in the event that a term can
only be understood if it is construed by a dictionary, if the term is defined by the Kirk-Othmer
Encyclopedia of Chemical Technology, 5th Edition, (2005), (Published by Wiley, John & Sons,
Inc.) this definition shall control how the term is to be defined in the claims.
At least one embodiment of the invention is a method of separating a desired material
from a comminuted sulfide mineral ore. The method comprising the steps of: providing an
aqueous suspension of the comminuted ore, adding an effective amount of an organophosphorus
compound to the suspension, affording the organophosphorus compound sufficient residence
time in the suspension, selectively floating materials by sparging the suspension to form a
concentrate and a slurry, and recovering the desired material from the appropriate suspension
layer. The organophosphorus compound is comprised of a substance selected from the group
consisting of a PAPEMP, in acid or salt form; a trialkanolamine tri(phosphate ester), in acid or
salt form; an amino tri(methylene phosphonic acid), in acid or salt form; a polyethylene amine
polyphosphonic acid, in acid or salt form; and combinations thereof
In at least one embodiment the flotation process is a direct flotation process and the
desired material forms a concentrate at the top of the suspension. In at least one embodiment, the
process further involves adding a frother to the suspension. In at least one of the embodiments,
the other contains alcohol. In at least one embodiment a collector is also added to the
suspension. In at least one embodiment the collector is PAX. In at least one embodiment, the
flotation process further comprises adding lead nitrate, copper sulfate, and any combination
thereof to the suspension.
In at least one embodiment, the ore contains a valuable metal, which can be but is not
limited to a precious metal and/or a base metal. In at least one embodiment the valuable metal is
selected from the list consisting of: gold, silver, copper, lead, zinc, molybdenum, nickel,
platinum, palladium, and any combination thereof.
While the use of some forms of PAPEMP in ore processing is not new, its clear
effectiveness as a sulfide mineral flotation aid is an unexpected result. US Patents 5,368,830 and
5,454,954 describes the use of PAPEMP in gold cyanide leaching solutions. Specifically they
discuss the use of PAPEMP in preventing the formation of calcium bearing scale on equipment
used during gold cyanide leaching processes. Cyanide leaching or cyanidation, is a process in
which gold bearing ore is dissolved in cyanide to separate it from other constituents of the ore.
The use of PAPEMP as a flotation aid is quite different than these prior uses because
when used, PAPEMP has previously only been used for mineral processing stages that occur at
different times and under different conditions from flotation separation. Most metals that
undergo ftoth flotation have not been subjected to a prior cyanidation step. In the context of gold
or silver bearing ore, in an overwhelming number of situations if there is a cyanidation step it is
conducted only after steps subsequent to flotation separation where the sulfides have been
removed or reduced by further processing such as roasting or autoclaving. This is because the
sulfides interfere with cyanidation and their removal improves the subsequent cyanidation step.
Rarely does a cyanidation step occur before a flotation step. The cyanidation step however is
never simultaneous to the flotation separation because the physical requirements of a cyanidation
step are contradictory to those involved in flotation separation.
I addition, the purpose and use of PAPEMP in this invention is completely different than
its use in the Prior Art. In the Prior Art, PAPEMP is used to prevent the deposition of calcium
bearing scale onto process equipment surfaces, which if left untreated, could result in equipment
blockage and fouling. In contrast this invention uses PAPEMP not to protect equipment, but to
enhance flotation selectivity as well as overall desired metal yield. In at least one embodiment
the PAPEMP is added to a flotation separation process, which is not prone to calcium bearing
scale deposition.
In at least one embodiment instead of or in addition to PAPEMP, one of the
polycarboxylate polymers and/or copolymers described in US Published Patent Application
2009/0294372 is used.
Without being limited by theory to the construal of the claims, it is believed that the
PAPEMP enhances the flotation separation process by preventing the adhesion of ore
constituents and process additives such as calcium bearing materials and magnesium bearing
materials and in particular calcium sulfate, calcium carbonate, clays, silicates, and any
combination thereof, to the metal sulfide and thereby allows a greater amount of collector to bind
to the metal sulfide. More bindings between the metal sulfide and the collector results in the
micro-bubbles pulling a greater amount of metal sulfide out of the slurry.
In at least one embodiment, the PAPEMP is added to an ore bearing suspension before the
collector is added. In at least one embodiment, the PAPEMP is afforded sufficient residence time
to clear off other ore constituents and process additives from metal sulfide particles before the
collector is added to the suspension. In at least one embodiment, the PAPEMP reduces the
amount of clay that is removed by the flotation process. In at least one embodiment, the
PAPEMP increases the purity of the removed metal sulfide.
In at least one embodiment the PAPEMP is introduced in a composition comprising 1-
40% water, 1-40% PAPEMP, and 1-40% of a polymer and/or copolymer of acrylic acid. In at
least one embodiment the PAPEMP is added to a supplemental flotation step. In at least one
embodiment the PAPEMP is added to a supplemental flotation step described in US Patents
5,068,028, 4,549,959, 2,492,936, and the references cited therein. In at least one embodiment the
supplemental flotation step separates molybdenite from copper bearing ores. In at least one
embodiment a depressant is used on at least one desired material to retain it in the slurry. In at
least one embodiment calcium is also added to the supplemental flotation step.
In addition to PAPEMP, other organophosporus compounds, in acid or salt form, may be
used in the invention in place of or n combination with PAPEMP. Trialkanolamine
triphosphate ester) (CAS No. 68171-29-9), amino tri(methylene phosphonic acid) (CAS No.
6419-19-8), and polyethylene amine polyphosphonic acids (e.g., ethylenediamine tetra(methylene
phosphonic acid), CAS No. 1429-50-1; diethylenetriamine penta(methylene phosphonic acid),
CAS No. 15827-60-8; etc.) have each demonstrated effectiveness as a selective flotation aid.
EXAMPLES
The foregoing may be better understood by reference to the following example,
which is presented for purposes of illustration and is not intended to limit the scope of the
invention.
A flotation circuit to process high carbonate pyritic gold-bearing ore was prepared.
The ore was finely ground so that 70% of the ore mass could be passed through a 325
mesh standard sieve. The ground ore mass was suspended in a slurry to afford
approximately 25% solids by weight. Sulfuric acid was added to reduce the pH to
approximately 5.5. PAPEMP (in amounts ranging from 3-7 ppm) as well as an alcohol
frother and PAX collector were added to the suspension. The suspension was sparged and
the concentrate was removed for further processing.
Analysis indicated that the concentrate comprised 85-87% recovery of the total
gold mass. Similar experiments conducted on the same facility with the same ore but
which were lacking the added PAPEMP only recovered 55-60% of the gold mass. The
increased yield and purity resulted in downstream ore processing steps to increase
productivity by as much as 50% without any other changes in the ore refining steps.
Furthermore, the addition of PAPEMP reduced the energy required in the
downstream roasting step. Roasting is a process in which carbonaceous material is
removed from the desired metal material by heating it. In roasting, the oxidation of
sulfides into sulfates adds energy to the heating process. The higher sulfide content of the
more pure floated metal sulfides provided more energy to the roasting process.
A sample of copper ore was ground to produce a flotation feed particle size P80 of
150 microns. The pH of the flotation was regulated by lime addition to achieve a target
value of pH=l 0. The collector reagent sodium isobutyl xanthate was applied at a dose of
221 grams per ton of ore, and a commercial frother reagent called W22 was applied at a
dose of 15 grams per ton of ore. Floated materials were removed from the cell surface at
time = 2, 4, 7, and 10 minutes.
The addition of a material comprised of 10.92% by weight trialkanolamine
tri(phosphate ester), added at concentrations of 20 ppm and 100 ppm as product (2.2%
and 10.9% respectfully as active trialkanolamine triphosphate ester), sodium salt) to the
flotation of the subject copper ore suspension. The initial rate of copper recovery and the
final concentrate recovery of copper relative to the same flotation conducted without the
material are shown in Table I below.
While this invention may be embodied in many different forms, there are shown in the
drawings and described in detail herein specific preferred embodiments of the invention. The
present disclosure is an exemplification of the principles of the invention and is not intended to
limit the invention to the particular embodiments illustrated. All patents, patent applications,
scientific papers, and any other referenced materials mentioned herein are incorporated by
reference in their entirety. Furthermore, the invention encompasses any possible combination of
some or all of the various embodiments described herein and incorporated herein.
The above disclosure is intended to be illustrative and not exhaustive. This description
will suggest many variations and alternatives to one of ordinary skill in this art. All these
alternatives and variations are intended to be included within the scope of the claims where the
term "comprising" means "including, but not limited to". Those familiar with the art may
recognize other equivalents to the specific embodiments described herein which equivalents are
also intended to be encompassed by the claims.
All ranges and parameters disclosed herein are understood to encompass any and all
subranges subsumed therein, and every number between the endpoints. For example, a stated
range of " 1 to 0" should be considered to include any and all subranges between (and inclusive
of) the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a
minimum value of 1 or more, (e.g. 1 to 6.1), and ending with amaximum value of 10 or less,
(e.g. 2.3 to 9.4, 3 to 8, 4 to 7), and finally to each number 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 contained
within the range.
This completes the description of the preferred and alternate embodiments of the
invention. Those skilled in the art may recognize other equivalents to the specific embodiment
described herein which equivalents are intended to be encompassed by the claims attached hereto.
Claims
1. A method of improving the removal of a particular material from a comminuted
sulfide mineral ore by a flotation separation process, the method comprising the steps of:
providing an aqueous suspension of the comminuted ore,
adding an effective amount of an organophosphorus compound to the suspension,
affording the organophosphorus compound sufficient residence time in the
suspension,
selectively floating the particular material by sparging the suspension to form a
concentrate and a slurry, and
recovering the particular material from the appropriate concentrate or slurry;
wherein the organophosphorus compound is comprised of a substance selected from
the group consisting of a PAPEMP, in acid or salt form; a trialkanolamine tri(phosphate
ester), in acid or salt form; an amino tri(methylene phosphonic acid), in acid or salt form; a
polyethylene amine polyphosphonic acid, in acid or salt form; and combinations thereof.
2. The method of claim 1 in which the flotation process is a portion of an overall ore
refining process, and if the ore refining process comprises a cyanidation process, the flotation
process occurs prior to the cyanidation process.
3. The method of claim 1 in which the flotation process is a portion of an overall ore
refining process that does not include a cyanidation process.
4. The method of claim 1 further comprising the step of adding a frother to the
suspension.
5. The method of claim 1 further comprising the step of adding a collector to the
suspension.
6. The method of claim 1 further comprising the step of adding lead nitrate, copper
sulfate, and any combination thereof to the suspension.
7. The method of claim 1 in which the particular material is a precious or base metal
selected from the list consisting of: gold, silver, copper, lead, zinc, molybdenum, nickel,
platinum, palladium, and any combination thereof.
8. The method of claim 1 in which the organophosphorus compound is added to a
flotation separation process not prone to calcium sulfate deposition.
9. The method of claim 1 in which the organophosphorus compound is added to an ore
bearing suspension before a collector is added and the organophosphorus compound is
afforded sufficient residence time to facilitate clearing off other ore constituents from metal
sulfide particles before the collector is added to the suspension.
10. The method of claim 1 which occurs within a metal refining operation in which the
addition of the organophosphorus compound during the flotation separation process increases
the recovery of the total metal in the ore by a range of between 1-80% when all other steps in
the refining process are controlled.
11. The method of claim 1 in which the added organophosphorus compound is in a
dosage within a range of about 0.1 ppm and 100 ppm.
12. The method of claim 1 in which the added organophosphorus compound is added
while in a composition comprising 1-40% water, 1-40% organophosphorus compound, and 1-
40% of a polymer and/or copolymer of acrylic acid.
13. The method of claim 1 in which the added organophosphorus compound reduces the
energy needed to roast the particular material when compared to a similar method of removal
lacking the added organophosphorus compound.
14. The method of claim 1 in which the added organophosphorus compound increases the
selectivity of which specific ore constituents are floated by the flotation separation process.
15. The method of claim 1 in which the flotation process is a direct flotation process and
the desired material forms a concentrate at the top of the suspension.