WO2025068822A1

WO2025068822A1 - Beneficiation of an ore bearing one or more sulphide minerals

Info

Publication number: WO2025068822A1
Application number: PCT/IB2024/059053
Authority: WO
Inventors: Diderik Johannes NEL; Elze GROBLER
Original assignee: BETACHEM Pty Ltd
Current assignee: BETACHEM Pty Ltd
Priority date: 2023-09-26
Filing date: 2024-09-18
Publication date: 2025-04-03
Anticipated expiration: 2026-03-26
Also published as: EP4642575A1; WO2025068822A4; WO2025068822A9

Abstract

A process for beneficiating a sulphide ore comprising one or more sulphide minerals into at least one value mineral-rich froth concentrate is provided. The process includes subjecting an aqueous slurry or pulp of particles of the sulphide ore, in the presence of a depressant selected from the group consisting of cyanuric acid trisodium salt (C₃H₄N₃NaO₃), sodium cyanate (NaOCN), cyanuric acid (C₃H₃N₃O₃), and mixtures of two or more of these, to froth flotation by aerating the slurry or pulp thereby to produce at least one value mineral-rich froth concentrate and an aerated slurry or pulp that includes gangue. Said at least one value mineral-rich froth concentrate is then separated from the aerated slurry or pulp.

Description

BENEFICIATION OF AN ORE BEARING ONE OR MORE SULPHIDE MINERALS

THIS INVENTION relates to flotation of sulphide ores. In particular, the invention relates to a process for beneficiating a sulphide ore comprising one or more sulphide minerals into at least one value mineral-rich froth concentrate, to the use of certain substances as flotation depressants, and to a froth flotation depressant composition.

Froth flotation is a process used for separating a value mineral, e.g., chalcopyrite (a copper and iron sulphide mineral), pentlandite (a nickel and iron sulphide mineral), galena (a lead sulphide mineral), sphalerite (a zinc and iron sulphide mineral), gold and platinum group metals (PGM's) from gangue in an ore, with the aim to produce a product or intermediary process stream in which the concentration of the value mineral is high enough to allow economical beneficiation of the product or intermediary process stream further in a downstream process. Froth flotation selectively separates hydrophobic materials from hydrophilic materials. Flotation processes, such as froth flotation, for beneficiating sulphide ores typically suffer from unsatisfactory separation of the value minerals into product streams, where a combination of sulphides minerals occurs in the same ore. This is a particularly vexing problem where the gangue includes an unwanted sulphide mineral such as pyrite (an iron disulphide mineral) or pyrrhotite (an iron sulphide mineral), or where two or more value minerals (e.g., lead and zinc) are present as sulphides. Where for example pyrite and pyrrhotite are floated with a value mineral, they undesirably dilute the flotation concentrate with respect to the desired value mineral.

Cyanide (typically NaCN) is a common depressant used in froth flotation processes to depress the flotation of one or more sulphide minerals, e.g., iron and zinc sulphides. When cyanide is used as depressant, the pH of the slurry needs to be kept above a level where it is safe to use the cyanide. The preferred pH for cyanide as suppressant is commonly above 8.5, e.g., about 9.5. Cyanide is however a classic poison and has been listed by the USA EPA as a priority pollutant. Froth flotation processes employing a depressant, particularly those processes that must separate a value mineral such as nickel or copper or lead or zinc from unwanted or gangue sulphide minerals such as pyrite and pyrrhotite by depressing the flotation of the unwanted or gangue sulphide minerals, using a depressant with fewer or less severe drawbacks than NaCN, would be desirable. Thus, it would be advantageous if a flotation process and flotation reagents can be provided which reduce the recovery of sulphide gangue minerals like pyrite and pyrrhotite and sphalerite into value mineral product streams.

It would also be advantageous if a flotation process and flotation reagents can be provided which allow forthe separation of individual sulphide minerals into two or more product streams where the content of a value mineral in each product stream is high enough to allow for economic beneficiation in a downstream process. As will be appreciated, a particular sulphide mineral, e.g., sphalerite, in one flotation process may be a value mineral, whereas in another flotation process, the same sulphide mineral may be gangue, flotation of which is desired to be depressed.

According to one aspect of the invention, there is provided a process for beneficiating a sulphide ore comprising one or more sulphide minerals into at least one value mineral-rich froth concentrate, the process including subjecting an aqueous slurry or pulp of particles of the sulphide ore, in the presence of a depressant selected from the group consisting of cyanuric acid trisodium salt (CsF NsNaCh), sodium cyanate (NaOCN), cyanuric acid (C3H3N3O3), and mixtures of two or more of these, to froth flotation by aerating the slurry or pulp thereby to produce at least one value mineral-rich froth concentrate and an aerated slurry or pulp that includes gangue; and separating said at least one value mineral-rich froth concentrate from the aerated slurry or pulp.

The gangue typically includes at least the sulphide mineral, or at least one of the sulphide minerals if more than one sulphide mineral is present in the sulphide ore. In other words, the process of the invention is effective in depressing some sulphide minerals to the exclusion of other sulphide minerals where there is more than one sulphide mineral present in the sulphide ore.

The depressant may include at least cyanuric acid trisodium salt (Ca^NaNaOa).

In one embodiment of the invention, the depressant includes cyanuric acid trisodium salt (Ca^NaNaOa) but no cyanuric acid (C3H3N3O3) and no sodium cyanate (NaOCN).

In one embodiment of the invention, the depressant includes sodium cyanate (NaOCN) but no cyanuric acid (C3H3N3O3) and no cyanuric acid trisodium salt (Cs^NsNaOs).

In another embodiment of the invention, the depressant includes cyanuric acid (C3H3N3O3) but no cyanuric acid trisodium salt (Cs^NsNaOs) and no sodium cyanate (NaOCN).

In still a further embodiment of the invention, the depressant includes two of sodium cyanate (NaOCN), cyanuric acid (C3H3N3O3), and cyanuric acid trisodium salt (C3H4N3NaO3). Thus, it is also provided that the depressant may include one or both of cyanuric acid (C3H3N3O3) and sodium cyanate (NaOCN), e.g. cyanuric acid (C3H3N3O3) and sodium cyanate (NaOCN) but no cyanuric acid trisodium salt (Cs^NsNaOs).

In yet a further embodiment of the invention, the depressant includes all three of sodium cyanate (NaOCN), cyanuric acid (C3H3N3O3), and cyanuric acid trisodium salt (C3H₄N₃NaO3).

The aqueous slurry or pulp of particles of the sulphide ore may be subjected to froth flotation in the presence of a pH adjustment agent, e.g., sodium carbonate or sodium hydroxide. The process may include conditioning the aqueous slurry or pulp to provide a conditioned slurry or pulp, prior to subjecting the conditioned slurry or pulp to froth flotation by aerating the conditioned slurry or pulp.

Conditioning the aqueous slurry or pulp may include admixing a collector with the slurry or pulp.

Conditioning the aqueous slurry or pulp may include admixing a frother with the slurry or pulp.

Conditioning the aqueous slurry or pulp may include increasing the pH of the aqueous slurry or pulp.

Instead, conditioning the aqueous slurry or pulp may include acidifying the aqueous slurry or pulp.

The pH of the aqueous slurry or pulp may be increased, by addition of a base, to a pH of between about 7 and about 11, preferably between about 9 and about 10.5, more preferably between about 9.5 and about 10, e.g., about 9.5.

Advantageously however, in one embodiment of the invention, the pH of the aqueous slurry is less than about 8.5, preferably less than about 8, e.g., in the range of pH 7 to pH 8. As will be appreciated, at these pH values, sodium cyanide is simply not an option.

Instead, the aqueous slurry may be acidified to a pH of between 1 and 7.

Conditioning the aqueous slurry or pulp may include admixing the depressant with the aqueous slurry or pulp.

The depressant may be admixed with the aqueous slurry or pulp at a ratio of between about 25 g/tonne of slurry or pulp and about 500 g/tonne of slurry or pulp, preferably between about 50g/tonne of slurry or pulp and about 300 g/tonne of slurry or pulp, more preferably between about 100 g/tonne of slurry or pulp and about 200 g/tonne of slurry or pulp, e.g., about 150 g/tonne of slurry or pulp.

The depressant may be in the form of a depressant composition, e.g., a depressant composition comprising the depressant selected from the group consisting of sodium cyanate (NaOCN), cyanuric acid (C3H3N3O3), cyanuric acid trisodium salt (Cs^NsNaCh), and mixtures of two or more of these, and a pH adjustment agent, e.g., sodium hydroxide or sodium carbonate. Admixing the depressant with the aqueous slurry or pulp may thus include admixing the depressant composition with the aqueous slurry or pulp.

Conditioning the aqueous slurry or pulp may include agitating the aqueous slurry or pulp, thereby to admix the depressant with the aqueous slurry or pulp. The aqueous slurry or pulp may be agitated mechanically.

The value mineral may be a copper, nickel, zinc, lead, gold, or PGM mineral.

In one embodiment of the invention, the value mineral is one or more sulphide minerals. The invention therefore provides that the sulphide ore may comprise one or more sulphide minerals that are value minerals.

The gangue may include one or more unwanted sulphide minerals. Such unwanted sulphide minerals would be different from the value mineral. Thus, as noted earlier, the depressant may depress certain sulphide minerals to the exclusion of other sulphide minerals.

The invention therefore provides that the ore may include at least one, or at least two value minerals that are sulphide minerals, and that the gangue may include one or more unwanted sulphide minerals. The sulphide ore may be, or may include, one or more of chalcopyrite, pentlandite, galena, sphalerite, pyrite, and pyrrhotite.

The depressant may depress the flotation of whichever of chalcopyrite, sphalerite, pyrite, and pyrrhotite is comprised by the sulphide ore, such that the chalcopyrite, sphalerite, pyrite, and/or pyrrhotite reports to the gangue. This does not exclude from the scope of the invention that the chalcopyrite, for example, may be a value mineral.

In one embodiment of the invention, the gangue includes sphalerite, and the value mineral is galena, or chalcopyrite, or both galena and chalcopyrite. In other words, the depressant may be effective in depressing sphalerite to the exclusion of galena and/or chalcopyrite.

Instead, the process of the invention may be employed to separate chalcopyrite and galena, by depressing flotation of the chalcopyrite using the depressant of the invention, so that the chalcopyrite remains in the aerated slurry, while floating galena so that the galena reports to the value mineral-rich froth concentrate.

In one embodiment of the invention, the gangue includes pyrite, or pyrrhotite, or both pyrite and pyrrhotite.

In another embodiment of the invention, the gangue includes sphalerite.

The process may include comminuting a sulphide ore to provide particles of the sulphide ore comprising one or more particulate sulphide minerals with a desired size distribution, and/or to liberate the one or more sulphide minerals from gangue.

The aqueous slurry or pulp may have a solids concentration of between about 10% by mass and about 40% by mass, preferably between about 15% by mass and about 35% by mass, more preferably between about 15% by mass and about 30% by mass, e.g., about 20% by mass. Subjecting the slurry or pulp, or conditioned slurry or pulp, to froth flotation may include feeding the slurry or pulp to one or more flotation cells, which produce at least one value mineral-rich froth concentrate thus being removed from the one or more flotation cells, and with the one or more flotation cells producing tails or tailings (i.e., aerated slurry or pulp), which includes the gangue, which is removed from the one or more flotation cells. The tails or tailings may be subjected to further processing, e.g., to flotation in one or more further flotation stages, to recover more of the value mineral.

The process may employ one or more rougher flotation cells.

At least some, for example two or three or four, of the rougher flotation cells may be configured to be operated in series, i.e., in a cascading arrangement.

The process may employ one or more rougher flotation cells upstream of one or more cleaner flotation cells. In this specification, a cleaner flotation cell is intended to be a flotation cell receiving value mineral-rich froth concentrate from an upstream flotation cell.

At least some, for example two, of the cleaner flotation cells may be configured to be operated in series. The process may also employ one or more additional cleaner flotation stages or cells functioning as a recleaner or re-recleaner stages if additional value mineral enrichment is required.

If desired or necessary, the process may include further comminuting or regrinding slurry or pulp being fed to a rougher flotation cell and/or the value mineral-rich froth concentrate from a rougher flotation cell before passing the value mineral-rich froth concentrate to said one or more cleaner flotation cells.

The process may include adding the depressant to a primary mill used to comminute the sulphide ore. In one embodiment, the depressant is added to the primary mill without pH adjustment, so that the pH in the primary mill is typically below 8.5, or even below 8.0.

In another embodiment, the depressant is added to the primary mill with pH adjustment, so that the pH in the primary mill is typically higher than 8.5.

Instead, or in addition, the depressant may be added to one or more rougher flotation cells, or to one or more scavenger flotation cells, or to one or more cleaner scavenger flotation cells, or to a regrind stage used to regrind slurry or pulp being fed to a rougher flotation cell, or used to regrind the value mineral-rich froth concentrate from a rougher flotation cell before passing the value mineral-rich froth concentrate to one or more cleaner flotation cells. The depressant may be added to these locations with or without any pH adjustment.

The process may include dewatering the value mineral-rich froth concentrate. Typically, the value mineral-rich froth concentrate being subjected to dewatering is, or is predominantly, a so-called cleaner concentrate or recleaner concentrate or re-recleaner concentrate or final concentrate produced by said one or more cleaner flotation cells.

Dewatering the value mineral-rich froth concentrate may include subjecting the value mineral-rich froth concentrate to one or more dewatering stages, comprising for example one or more cyclones, thickeners and/or filters, such as rotating drum filters, continuous belt filters or plate and frame filters.

The process may include treating tails from a flotation cell, e.g., from one or more rougher flotation cells, or even from a cleaner flotation cell, e.g., before discharging the tails to a tails storage facility such as a tails dump or tails dam.

Treating the tails from a flotation cell may include neutralizing the tails. The invention extends to the use of sodium cyanate (NaOCN) or cyanuric acid (C3H3N3O3) or cyanuric acid trisodium salt (CsI^NsNaOs), or mixtures of two or more of these, as a depressant in a froth flotation process.

According to another aspect of the invention, there is provided a froth flotation depressant composition that includes two or more of sodium cyanate (NaOCN), cyanuric acid (C3H3N3O3) and cyanuric acid trisodium salt (Cs^NsNaOs).

According to a further aspect of the invention, there is provided a froth flotation depressant composition that includes a depressant selected from the group consisting of cyanuric acid trisodium salt (C3H4N3NaO3), sodium cyanate (NaOCN), cyanuric acid (C3H3N3O3), and mixtures of two or more of these; and a pH adjustment agent.

The pH adjustment agent may be a base.

The pH adjustment agent may be sodium hydroxide, or sodium carbonate, or mixtures of these two compounds.

In one embodiment of the invention, the froth flotation depressant composition includes at least cyanuric acid trisodium salt as depressant and sodium carbonate as pH adjustment agent. This may be to the exclusion of sodium cyanate (NaOCN) and cyanuric acid (C3H3N3O3).

In another embodiment of the invention, the froth flotation depressant composition includes cyanuric acid as depressant and sodium hydroxide as pH adjustment agent.

In one embodiment of the invention, the froth flotation depressant composition is in the form of a dry powder or particulate material of two or more of sodium cyanate (NaOCN) powder or particles, cyanuric acid (C3H3N3O3) powder or particles and cyanuric acid trisodium salt (C3H4N3NaO3) powder or particles.

In another embodiment of the invention, the froth flotation depressant composition is in the form of an aqueous composition of two or more of dissolved sodium cyanate (NaOCN), dissolved cyanuric acid (C3H3N3O3) and dissolved cyanuric acid trisodium salt (C3H₄N₃NaO3).

In a further embodiment of the invention, the froth flotation depressant composition is in the form of an admixture of a dry powder or particulate material of the depressant selected from the group consisting of sodium cyanate (NaOCN) powder or particles, cyanuric acid (C3H3N3O3) powder or particles, cyanuric acid trisodium salt (Cs^NsNaC ) powder or particles, and mixtures of two or more of these, and the pH adjustment agent in a powder or particulate form.

In yet a further embodiment of the invention, the froth flotation depressant composition is in the form of a dry powder or particulate material admixture of cyanuric acid trisodium salt (Cs^NsNaCh) powder or particles and sodium carbonate powder or particles as the pH adjustment agent.

In still another embodiment of the invention, the froth flotation depressant composition is in the form of a dry powder or particulate material admixture of cyanuric acid powder or particles and sodium hydroxide powder or particles as the pH adjustment agent.

The froth flotation depressant composition may include the depressant in a concentration of between about 30% and about 60% by mass, preferably between about 30% and about 50% by mass, e.g., about 33% by mass, on a dry basis.

The froth flotation depressant composition may include the pH adjustment agent in a concentration of between about 40% and about 70% by mass, preferably between about 50% and about 70% by mass, e.g., about 67% by mass, on a dry basis. The invention will now be described by way of the following examples and the accompanying drawings.

In the drawings,

Figure 1 shows a process for the beneficiation of a nickel sulphide ore or a copper sulphide ore, referred to in Examples 1 to 3; and

Figure 2 shows a process for the beneficiation of a lead sulphide and zinc sulphide ore, referred to in Example 4.

Referring to Figure 1 of the drawings, reference numeral 10 generally indicates a typical froth flotation process for the beneficiation of a nickel sulphide ore or a copper sulphide ore.

The process 10 includes a mill 12, a rougher flotation cell 14, a first cleaner flotation cell 16, a second cleaner flotation cell 18, and a third cleaner flotation cell 20. The flotation cells 14, 16, 18 and 20 are froth flotation cells.

An ore feed line 22 leads to the mill 12, with a pulp or slurry line 24 leading from the mill 12 to the rougher flotation cell 14. A rougher tails line 26 and a rougher concentrate line 28 lead from the rougher flotation cell 14.

The rougher concentrate line 28 leads to the first cleaner flotation cell 16, which is provided with a first cleaner tails line 30 and a first cleaner concentrate line 40. The first cleaner concentrate line 40 leads to the second cleaner flotation cell 18, which is provided with a second cleaner tails line 42 which returns to the first cleaner flotation cell 16, and a second cleaner concentrate line 44 which leads to the third cleaner flotation cell 20.

The third cleaner flotation cell 20 is provided with a final value mineral concentrate line 48 (e.g., a final copper concentrate line or a final nickel concentrate line), and a third cleaner tails line 46 which returns to the second cleaner flotation cell 18. The concentrate lines 28, 40, 44 and 48 all transport froth concentrate from their respective froth flotation cells 14, 16, 18 and 20.

Referring to Figure 2 of the drawings, reference numeral 100 generally indicates a typical froth flotation process for the beneficiation of a sulphide ore bearing lead and zinc.

The process 100 includes a mill 112, a lead rougher flotation cell 114, a zinc rougher flotation cell 116, a first lead cleaner flotation cell 118, a second lead cleaner flotation cell 120 and a third lead cleaner flotation cell 122.

The process 100 further includes a regrind mill 124, a zinc first cleaner flotation cell 126, a zinc second cleaner flotation cell 128 and a zinc third cleaner flotation cell 130.

The flotation cells 114, 116, 118, 120, 122, 126, 128 and 130 are froth flotation cells.

An ore feed line 132 leads to the mill 112, with a slurry or pulp line 134 leading from the mill 112 to the lead rougher flotation cell 114. A lead rougher concentrate line 136 leads from the lead rougher flotation cell 114 to the lead first cleaner flotation cell 118. A lead first cleaner concentrate line 137 leads from the lead first cleaner flotation cell 118 to the lead second cleaner flotation cell 120, and a lead second cleaner tails line 138 leads from the lead second cleaner flotation cell 120 back to the lead first cleaner flotation cell 118.

A lead rougher tails line 139 leads from the lead rougher flotation cell 114 to the zinc rougher flotation cell 116. A lead first cleaner tails line 141 leads from the lead first cleaner flotation cell 118 to join the lead rougher tails line 139.

A lead second cleaner concentrate line 140 leads from the lead second cleaner flotation cell 120 to the lead third cleaner flotation cell 122. A lead third cleaner tails line 142 leads from the lead third cleaner flotation cell 122 back to the lead second cleaner flotation cell 120, and the lead third cleaner flotation cell 122 is also provided with a final lead concentrate line 146.

The zinc rougher flotation cell 116 is provided with a zinc rougher tails line 148 and a zinc rougher concentrate line 150. The zinc rougher concentrate line 150 leads to the regrind mill 124, which is provided with a discharge line 152 which leads to the zinc first cleaner flotation cell 126.

The zinc first cleaner flotation cell 126 is provided with a zinc first cleaner tails line 156 and a zinc first cleaner concentrate line 154, which leads to the zinc second cleaner flotation cell 128. A zinc second cleaner tails line 158 returns from the zinc second cleaner flotation cell 128 to the zinc first cleaner flotation cell 126.

A zinc second cleaner concentrate line 160 leads from the zinc second cleaner flotation cell 128 to the zinc third cleaner flotation cell 130. In turn, the zinc third cleaner flotation cell 130 is provided with a zinc third cleaner tails line 162 which returns to the zinc second cleaner flotation cell 128, and a final zinc concentrate line 164.

The concentrate lines 136, 137, 140, 146, 150, 154, 160 and 164 all transport froth concentrate from their respective froth flotation cells 114, 118, 120, 122, 116, 126, 128 and 130.

EXAMPLES

In all of the following examples, a trial depressant (hereinafter referred to as Betamin 1032), in accordance with the invention, was used. The trial depressant was a dry powder consisting of 33% by mass dry cyanuric acid trisodium salt powder and the balance being dry sodium carbonate powder. Example 1

Sulphide ore containing Ni sulphides, pyrite and pyrrhotite

The ore contains the following nickel sulphide value minerals: vaesite, violarite, millerite, polydymite and pentlandite. The ore contains the following major gangue minerals: pyrite, pyrrhotite, talc, quartz, feldspar, mica, and dolomite.

The ore is milled to approximately 90% passing 75 microns, in accordance with the process 10. A carboxymethylcellulose (CMC) depressant, xanthate and frother are added to float a rougher concentrate in the rougher flotation cell 14. Rougher concentrate 28 is cleaned in the three froth flotation cleaner cells 16, 18 and 20 to a final value mineral concentrate withdrawn by means of the final value mineral concentrate line 48. In this case, this is a final Ni concentrate. CMC depressant is added in the cleaner flotation cells 16, 18 and 20. The pH in the cleaner flotation cells 16, 18 and 20 is adjusted to pH 10 with lime.

A sample of the third cleaner feed was taken from the second cleaner concentrate line 44 and floated with a laboratory scale flotation machine.

Baseline condition: Floated for 5 minutes without adding any additional reagents.

Test condition: Betamin 1032 added at 976 g/t and conditioned for 1 min, then floated for 5 minutes.

Table 1: Summary of flotation test results. Ni Sulphide ore.

As will be noted, the Ni content of the froth concentrate was higher, and the iron recovery to the froth concentrate was lower, compared to floating without the depressant of the invention. The depressant in accordance with the invention thus successfully depressed flotation of at least the pyrite and pyrrhotite.

Example 2

Sulphide ore containing Cu sulphides, pyrite and pyrrhotite

The ore contains the following copper sulphide value minerals: chalcopyrite and chalcocite. The ore contains the following major gangue minerals: pyrite, pyrrhotite, quartz, feldspar, mica calcite and dolomite.

The ore is milled to approximately 90% passing 75 microns, in accordance with the process 10. A carboxymethylcellulose (CMC) depressant, xanthate and frother are added to float a rougher concentrate in the rougher flotation cell 14. Rougher concentrate 28 is cleaned in the three froth flotation cleaner cells 16, 18 and 20 to a final value mineral concentrate withdrawn by means of the final value mineral concentrate line 48. In this case, this is a final Cu concentrate. CMC depressant is added in the cleaner flotation cells 16, 18 and 20. The pH in the cleaner flotation cells 16, 18 and 20 is adjusted to pH 10 with lime.

Test condition: Add Betamin 1032, condition for 2 minutes. Float for 5 minutes.

Table 2: Summary of flotation test results. Cu Sulphide ore.

As will be noted, the Cu recovery when using the depressant composition was comparable to floating without the depressant composition of the invention, however iron recovery was significantly reduced. The depressant/depressant composition in accordance with the invention thus successfully depressed flotation of at least the pyrite and pyrrhotite.

Example 3

Sulphide ore containing Cu sulphides, pyrite and pyrrhotite

The ore contains the following copper sulphide value minerals: chalcopyrite, digenite. The ore contains the following major gangue minerals: pyrite, pyrrhotite, quartz, feldspar, mica, dolomite and calcite.

The ore is milled to approximately 90% passing 150 microns, in accordance with the process 10. A sulphide collector and frother is added to float a rougher concentrate in the rougher flotation cell 14. Rougher concentrate 28 is cleaned in the three froth flotation cleaner cells 16, 18 and 20 to a final value mineral concentrate withdrawn by means of the final value mineral concentrate line 48. In this case, this is a final Cu concentrate. CMC depressant is added in the cleaner flotation cells 16, 18 and 20. The pH in the cleaner flotation cells 16, 18 and 20 is adjusted to pH 10 with lime.

A sample of the third cleaner feed was taken from the second cleaner concentrate line 44 and floated with a laboratory scale flotation machine. Baseline condition: Adjust pH to 8 with lime. Add 72 g/t CMC depressant. Condition 2 minutes. Float concentrate for 5 minutes. Condition for 1 minute. Float concentrate for 5 minutes.

Test condition: Adjust pH to 8 with lime. Add 72 g/t CMC depressant. Add Betamin 1032. Condition 2 minutes. Float concentrate for 5 minutes. Add 14 g/t isopropyl ethyl thionocarbamate as collector. Condition for 1 minute. Float concentrate for 5 minutes.

Table 3: Summary of flotation test results. Cu Sulphide ore.

As will be noted, depending on dosing rate of the depressant of the invention, both copper recovery and copper concentrate grade were improved, compared to floating without the depressant of the invention. The depressant in accordance with the invention thus successfully depressed flotation of at least some of the sulphide gangue minerals.

Example 4

Sulphide ore containing Zn and Pb sulphides, pyrite and pyrrhotite The ore contains the following lead sulphide value minerals: galena. The ore contains the following zinc sulphide value minerals: sphalerite. The ore contains the following major gangue minerals: chalcopyrite, galena (with respect to zinc as value mineral), pyrite, pyrrhotite, quartz, feldspar, mica, calcite and dolomite.

The ore is milled to approximately 90% passing 75 microns, in accordance with the process 100. The pH is adjusted to 10 with lime. 100 g/t of sodium cyanide is added. Xanthate and frother are added to float a rougher concentrate in the lead rougher flotation cell 114. Lead rougher concentrate 136 is cleaned in the three froth flotation cleaner cells 118, 120 and 122 to a lead concentrate withdrawn by means of the final lead concentrate line 146.

Lead rougher tails is withdrawn from the lead rougher flotation cell 114 and conditioned with 800 g/t CuSC . Xanthate and frother are added to float a zinc rougher concentrate in the zinc rougher flotation cell 116. Zinc rougher concentrate is transferred by means of the zinc rougher concentrate line 150 to the regrind mill 124, where it is re-milled and thereafter cleaned in three froth flotation cleaner cells 126, 128 and 130 to a final zinc concentrate withdrawn by means of the final zinc concentrate line 164.

A sample of the slurry or pulp from the slurry or pulp line 134 was used for the test.

Baseline condition: Adjust pH to 9.5 with lime. Add CuSC 50 g/t. Add sodium cyanide 90 g/t. Add xanthate at 20 g/t. Float Pb rougher concentrate for 5 minutes. Add CuSC 1000 g/t. Add xanthate 40 g/t. Float Zn rougher concentrate.

Test condition. Adjust pH to 9.5 with lime. Add CuSC 50 g/t. Add Betamin 1032. Add xanthate at 20 g/t. Float Pb rougher concentrate for 5 minutes. Add CuSC 1000 g/t. Add xanthate 40 g/t. Float Zn rougher concentrate. able 4: Summary of test conditions. Zn Sulphide ore.

able 5: Summary of flotation results. Zn Sulphide ore.

This example illustrates, inter alia, that the depressant/depressant composition of the invention advantageously also depresses sphalerite whilst floating galena and/or chalcopyrite. It is also believed that the depressant/depressant composition of the invention can depress chalcopyrite whilst floating galena.

Example 5

Sulphide ore containing Cu sulphides, pyrite and pyrrhotite.

The ore contains the following copper sulphide value minerals: chalcopyrite, chalcocite and bornite. The ore contains the following major gangue minerals: pyrite, pyrrhotite, quartz, feldspar, mica and dolomite.

This work was done on exploration samples. This ore was not commercially processed at time of testing.

Baseline condition: Mill. Adjust pH to 10.5. Add 200 g/t xanthate. Float rougher concentrate. Mill rougher concentrate. Adjust pH to 10.5. Add 200 g/t sodium cyanide. Add 10 g/t xanthate. Float cleaner concentrate. Float recleaner concentrate.

Test condition. Mill. Adjust pH to 10.5. Condition for 5 minutes. Add 10 g/t isopropyl ethyl thionocarbamate as collector. Float rougher concentrate. Mill rougher concentrate. Adjust pH to 10.5. Add 200 g/t Betamin 1032. Add 10 g/t isopropyl ethyl thionocarbamate as collector.

Float cleaner concentrate. Float recleaner concentrate. Table 6: Summary of flotation test results. Cu Sulphide ore.

Cleaner

Re cleaner

Example 6

Sulphide ore containing Cu sulphides and Zn sulphides

The ore contains the following copper sulphide value mineral: chalcopyrite. The ore contains the following zinc sulphide value mineral: sphalerite. The ore contains the following major gangue minerals: pyrite, pyrrhotite, quartz, feldspar, mica and dolomite.

Baseline condition: Mill. Adjust pH to 9.5. Add 300 g/t sodium cyanide. Add 5 g/t isopropyl ethyl thionocarbamate as collector. Add 10 g/t sodium di isobutyl di thiophosphate. Float first rougher concentrate for 3 minutes. Float second rougher concentrate for 7 minutes. Add 10 g/t isopropyl ethyl thionocarbamate.

Test condition. Mill. Adjust pH to 9.5. Add 300 g/t Betamin 1032. Add 5 g/t isopropyl ethyl thionocarbamate as collector. Add 10 g/t sodium di isobutyl di thiophosphate. Float first rougher concentrate for 3 minutes. Float second rougher concentrate for 7 minutes. Add 10 g/t isopropyl ethyl thionocarbamate.

Table 7: Summary of flotation test results. Cu and Zn Sulphide ore.

Example 6

Sulphide ore containing Cu sulphides and Zn sulphides

Baseline condition: Mill. Adjust pH to 9.5 in the mill. Add 500 g/t sodium cyanide. Add 1650 g/t ZnSC . Add 5 g/t isopropyl ethyl thionocarbamate as collector. Add 10 g/t sodium di isobutyl di thiophosphate. Float first rougher concentrate for 3 minutes. Float second rougher concentrate for 7 minutes. Add 10 g/t isopropyl ethyl thionocarbamate.

Test condition. Add 500 g/t Betamin 1032 in the mill. pH in mill is unadjusted to 7.5. Mill. Adjust pH to 9.5. Add 1650 g/t ZnSC . Add 5 g/t isopropyl ethyl thionocarbamate as collector. Add 10 g/t sodium di isobutyl di thiophosphate. Float first rougher concentrate for 3 minutes. Float second rougher concentrate for 7 minutes. Add 10 g/t isopropyl ethyl thionocarbamate

Table 8: Summary of flotation test results. Cu and Zn Sulphide ore.

The invention, as illustrated, advantageously provides a process for beneficiating a particulate sulphide ore comprising one or more sulphide minerals into at least one value mineral-rich froth concentrate, and a depressant composition for use in such a process, in which the use of cyanide, in particular sodium cyanide, is avoided. In one embodiment, the invention also provides a depressant composition which is advantageously in a dry powdered form, facilitating handling and storage, and which in a preferred embodiment, includes a pH adjustment agent. The depressant of the invention can advantageously safely be added to a froth flotation process unit operation or stream, at a pH less than 8.5, or even less than 8. In other words, there is no need first to increase the pH above 8.5, before adding the depressant, as the pH can safely be increased concomitantly with the addition of the depressant, or thereafter. The depressant of the invention, as illustrated, surprisingly can depress pyrite, pyrrhotite, chalcopyrite and sphalerite.

Claims

1. A process for beneficiating a sulphide ore comprising one or more sulphide minerals into at least one value mineral-rich froth concentrate, the process including subjecting an aqueous slurry or pulp of particles of the sulphide ore, in the presence of a depressant selected from the group consisting of cyanuric acid trisodium salt (Ca^NaNaOa), sodium cyanate (NaOCN), cyanuric acid (C3H3N3O3), and mixtures of two or more of these, to froth flotation by aerating the slurry or pulp thereby to produce at least one value mineral-rich froth concentrate and an aerated slurry or pulp that includes gangue; and separating said at least one value mineral-rich froth concentrate from the aerated slurry or pulp.

2. The process according to claim 1, wherein the depressant includes at least cyanuric acid trisodium salt (Cs^NsNaOs).

3. The process according to claim 2, wherein the depressant includes no cyanuric acid (C3H3N3O3) and no sodium cyanate (NaOCN).

4. The process according to claim 2, wherein the depressant further includes one or both of cyanuric acid (C3H3N3O3) and sodium cyanate (NaOCN).

5. The process according to claim 1, wherein the depressant includes sodium cyanate (NaOCN) but no cyanuric acid (C3H3N3O3) and no cyanuric acid trisodium salt (C3H4N3NaO3); or cyanuric acid (C3H3N3O3) but no cyanuric acid trisodium salt (Cs^NsNaOs) and no sodium cyanate (NaOCN); or sodium cyanate (NaOCN) and cyanuric acid (C3H3N3O3) but no cyanuric acid trisodium salt (C3H₄N₃NaO3).

6. The process according to any one of claims 1 to 5, which includes conditioning the aqueous slurry or pulp by increasing the pH of the aqueous slurry or pulp by addition of a base, to a pH of between about 7 and about 11, preferably between about 9 and about 10.5, more preferably between about 9.5 and about 10, e.g., about 9.5, to provide a conditioned slurry or pulp, and then subjecting the conditioned slurry or pulp to froth flotation by aerating the conditioned slurry or pulp

7. The process according to any one of claims 1 to 6, wherein the pH of the aqueous slurry or pulp, or of the conditioned slurry or pulp, is less than about 8.5, preferably less than about 8, e.g., in the range of pH 7 to pH 8.

8. The process according to any one of claims 1 to 5, which includes conditioning the aqueous slurry or pulp by acidifying the aqueous slurry or pulp to a pH of between 1 and 7.

9. The process according to any one of claims 1 to 8, which includes admixing the depressant with the aqueous slurry or pulp at a ratio of between about 25 g/tonne of slurry or pulp and about 500 g/tonne of slurry or pulp, preferably between about 50g/tonne of slurry or pulp and about 300 g/tonne of slurry or pulp, more preferably between about 100 g/tonne of slurry or pulp and about 200 g/tonne of slurry or pulp, e.g., about 150 g/tonne of slurry or pulp.

10. The process according to any one of claims 1 to 9, wherein the depressant is in the form of a depressant composition, comprising the depressant selected from the group consisting of cyanuric acid trisodium salt (Ca^NaNaCh), sodium cyanate (NaOCN), cyanuric acid (C3H3N3O3), and mixtures of two or more of these, and a pH adjustment agent, e.g., sodium hydroxide or sodium carbonate.

11. The process according to any one of claims 1 to 10, wherein the value mineral is one or more of a copper, nickel, zinc, lead, gold, or a PGM mineral.

12. The process according to any one of claims 1 to 11, wherein the value mineral is one or more sulphide minerals.

13. The process according to any one of claims 1 to 12, wherein the gangue includes one or more unwanted sulphide minerals, different from the value mineral.

14. The process according to any one of claims 1 to 13, wherein the sulphide ore is or includes one or more of chalcopyrite, pentlandite, galena, sphalerite, pyrite, and pyrrhotite.

15. The process according to claim 14, wherein the depressant depresses the flotation of one or more of chalcopyrite, sphalerite, pyrite, and pyrrhotite such that the chalcopyrite, sphalerite, pyrite, and/or pyrrhotite reports to the gangue.

16. The process according to any one of claims 1 to 15, wherein the aqueous slurry or pulp has a solids concentration of between about 10% by mass and about 40% by mass, preferably between about 15% by mass and about 35% by mass, more preferably between about 15% by mass and about 30% by mass, e.g., about 20% by mass.

17. A froth flotation depressant composition that includes a depressant selected from the group consisting of cyanuric acid trisodium salt (Cal^NaNaCh), sodium cyanate (NaOCN), cyanuric acid (C3H3N3O3), and mixtures of two or more of these; and a pH adjustment agent.

18. The composition according to claim 17, which includes at least cyanuric acid trisodium salt (Cs^NsNaCh).

19. The composition according to claim 17 or claim 18, wherein the pH adjustment agent is a base selected from sodium hydroxide, sodium carbonate, and mixtures of these two compounds.

20. The composition according to any one of claims 17 to 19, which includes the depressant in a concentration of between about 30% and about 60% by mass, preferably between about 30% and about 50% by mass, e.g., about 33% by mass, on a dry basis; and the pH adjustment agent in a concentration of between about 40% and about 70% by mass, preferably between about 50% and about 70% by mass, e.g., about 67% by mass, on a dry basis.