Separation of copper minerals from pyrite using air-metabisulfite treatment

Abstract

The present invention relates to flotation of sulfidic copper-molybdenum- and gold-containing minerals. More specifically, the invention relates to sulfoxy reagent-assisted floatation for separating of sulfides of copper, molybdenum and gold from pyrite, marcasite, pyrrhotite, arsenopyrite, and other gangue minerals following aerating by an oxidizing gas and contacting by a sulfoxy reagent. To promote collection and flotation the feed mineral materials are preferably not contacted with an externally generated non-oxidizing gas to lower the dissolved molecular oxygen content prior to flotation.

Claims

1. A process for recovering one or more metals, comprising: providing an oxygenated, slurried valuable metal-containing feed material comprising a valuable metal sulfide mineral, wherein the oxygenated, slurried valuable metal-containing feed material comprises one or more of brackish water having a salinity of about 0.1 parts per thousand (0.01%) or more, saltwater having a salinity of about 0.1 parts per thousand (0.01%) or more, fresh water having a salinity of about 0.1 parts per thousand (0.01%) or more, and buffered water having a salinity of about 0.1 parts per thousand (0.01%) or more, and a gangue sulfide mineral comprising iron pyrite; and contacting the oxygenated, slurried valuable metal-containing feed material, while maintaining the dissolved oxygen content of the oxygenated, slurried valuable metal-containing feed material at a level of at least about 3 ppm, with a sulfoxy reagent to form a treated slurried feed material; and floating the treated slurried feed material to form a concentrate comprising the valuable metal sulfide mineral and tailings comprising the iron pyrite.

2. The process of claim 1, wherein the oxygenated, slurried valuable metal-containing feed material is free of pH adjustment before and during the floating step.

3. The process of claim 1, wherein the oxygenated, slurried valuable metal-containing feed material has a pH of less than pH 8.5.

4. The process of claim 1, wherein, prior to the floating step, the oxygenated, slurried valuable metal-containing feed material is not contacted with an externally generated non-oxidizing gas to lower a dissolved molecular oxygen content of the oxygenated, slurried valuable metal-containing feed material.

5. The process of claim 1, wherein at least about 50 g/t of the sulfoxy reagent is added to the oxygenated, slurried valuable metal-containing feed material.

6. The process of claim 1, wherein the floating step is a cleaner flotation, wherein the oxygenated, slurried valuable metal-containing feed material is a rougher concentrate of a rougher flotation, and wherein the oxygenated, slurried valuable metal-containing feed material is free of contact with a sulfoxy reagent prior to the rougher flotation.

7. The process of claim 1, wherein the sulfoxy reagent is one or more of an ammonium, hydrogen, alkali, or alkaline earth metal sulfite, bisulfite, and metabisulfite.

8. The process of claim 1, wherein the tailings further comprises at least one of marcasite, arsenopyrite, and pyrrhotite.

9. The process of claim 1, wherein the valuable metal sulfide mineral comprises at least one of a copper sulfide and molybdenum sulfide, wherein the floating step is a cleaner flotation, wherein the sulfoxy reagent is added to a solution derived from a regrind circuit, wherein the oxygenated, slurried valuable metal-containing feed material is a rougher concentrate of a rougher flotation, wherein the oxygenated, slurried valuable metal-containing feed material is free of contact with a sulfoxy reagent prior to the rougher flotation, and wherein more than 200 g/t of sulfoxy reagent is added to the oxygenated, slurried valuable metal-containing feed material.

10. The process of claim 1, wherein, prior to the floating step, the oxygenated, slurried valuable metal-containing feed material is not contacted with an externally generated non-oxidizing gas to lower a dissolved molecular oxygen content of the oxygenated, slurried valuable metal-containing feed material, and wherein the oxygenated, slurried feed material has a pH of less than about pH 8.5.

11. The process of claim 1, wherein the floating step is a cleaner flotation, wherein the sulfoxy reagent is added to an aqueous slurry derived from the valuable metal sulfide mineral in a mill, wherein the mill is in a regrind circuit, wherein the oxygenated, slurried valuable metal-containing feed material is a rougher concentrate of a rougher flotation, and wherein the oxygenated, slurried valuable metal-containing feed material is free of contact with a sulfoxy reagent prior to rougher flotation.

12. The process of claim 1, wherein the contacting step comprises contacting the sulfoxy reagent with a freshly exposed and unoxidized surface of the valuable metal sulfide mineral.

13. The process of claim 1, wherein the contacting of sulfoxy reagent with the oxygenated, slurried valuable metal-containing feed material occurs during one or both of a primary and secondary comminution.

14. The process of claim 1, wherein the valuable metal sulfide mineral contains one or both of gold and silver.

15. A process for recovering one or more metals, comprising: providing an oxygen-sparged, slurried valuable metal-containing feed material comprising a valuable metal sulfide mineral and a gangue sulfide mineral, wherein the oxygen-sparged, slurried valuable metal-containing feed material comprises one or more of brackish water having one or more of a salinity of about 0.01% or more and a total dissolved solids content of at least about 10,000 mg/L, salt water having one or more of a salinity of about 0.01% or more and a total dissolved solids content of at least about 10,000 mg/L, fresh water having one or more of a salinity of about 0.01% or more and a total dissolved solids content of at least about 10,000 mg/L, and buffered water having one or more of a salinity of about 0.01% or more and a total dissolved solids content of at least about 10,000 mg/L; contacting the oxygen-sparged, slurried valuable metal-containing feed material, while maintaining the dissolved oxygen content of the oxygen-sparged, slurried valuable metal-containing feed material at an amount of least about 3 ppm, with a sulfoxy reagent to form a treated slurried feed material; and floating the treated slurried feed material to form a concentrate comprising the valuable metal sulfide mineral and tailings comprising the gangue sulfide mineral, wherein the valuable metal sulfide mineral comprises at least one of a copper sulfide mineral and molybdenum sulfide mineral and wherein the gangue sulfide mineral comprises iron pyrite.

16. The process of claim 15, wherein the contacting of the oxygen-sparged, slurried valuable metal-containing feed material with the sulfoxy reagent to form the treated slurried feed material comprises a first portion of the sulfoxy reagent, the process further comprising one or more of: i) contacting a second portion of the sulfoxy reagent during comminution; ii) contacting a second portion of the sulfoxy reagent during cleaning; iii) contacting a second portion of the sulfoxy reagent during re-cleaning; and i) contacting a second portion of the sulfoxy reagent during scavenging.

17. The process of claim 15, further comprising: conditioning the treated slurried feed material prior to the floating of the treated slurried feed material, wherein the conditioning step comprises contacting the treated slurried feed material with one or more of: (a) a collector; (b) a frother; (c) an activator; (d) a depressant; (e) a clay dispersant; (f) a modifier; (g) lime; and (h) a reagent to control electropotential (Eh), pH or both Eh and pH.

18. The process of claim 15, wherein the providing and floating steps are conducted at a pH from pH 3 to about pH 8 and an Eh of one or more of: greater than about 5 mV and less than about 155 mV or from about 10 to about 120 mV.

19. The process of claim 15, wherein the gangue sulfide mineral further comprises one or more of marcasite, pyrrhotite, and arsenopyrite, and wherein the process further comprises: conditioning, after the providing step, the oxygen-sparged, slurried valuable metal-containing feed material with one or more of a collector and frother to form a conditioned feed material, wherein the conditioning step is conducted in the absence of any added sulfoxy reagent.

20. The process of claim 15, wherein, prior to the floating step, the oxygen-sparged slurried valuable metal-containing feed material is not contacted with an externally generated non-oxidizing gas to lower a dissolved molecular oxygen content of the oxygen-sparged slurried valuable metal-containing feed material.

21. The process of claim 15, wherein at least about 50 g/t of the sulfoxy reagent is added to the oxygen-sparged, slurried valuable metal-containing feed material, and wherein the sulfoxy reagent is one or more of an ammonium, hydrogen, alkali, or alkaline earth metal sulfite, bisulfite, and metabisulfite.

22. A process for recovering one or more metals, comprising: providing a slurried valuable metal- and oxygen-containing feed material having a dissolved oxygen content of at least about 3 ppm and at least one of a copper sulfide and molybdenum sulfide mineral as a valuable metal sulfide mineral, wherein the slurried valuable metal- and oxygen-containing feed material comprises one or more of brackish water having one or more of a salinity of about 0.01% or more and a dissolved solids content of at least about 10,000 mg/L, salt water having one or more of a salinity of about 0.01% or more and a dissolved solids content of at least about 10,000 mg/L, fresh water having one or more of a salinity of about 0.01% or more and a dissolved solids content of at least about 10,000 mg/L, and buffered water having one or more of a salinity of about 0.01% or more and a dissolved solids content of at least about 10,000 mg/L, and gangue sulfide mineral comprising iron pyrite; contacting the slurried valuable metal- and oxygen-containing feed material, while maintaining the dissolved oxygen content of the slurried valuable metal- and oxygen-containing feed material at about at least 3 ppm, with a sulfoxy reagent to form a treated slurried feed material; and floating the treated slurried feed material to form a concentrate.

23. The process of claim 22, wherein, prior to the floating step, the slurried valuable metal- and oxygen-containing feed material is not contacted with an externally generated non-oxidizing gas to lower a dissolved molecular oxygen content of the slurried valuable metal- and oxygen-containing feed material.

24. The process of claim 22, wherein the at least one of a copper sulfide and molybdenum sulfide is a copper sulfide, wherein the floating step is cleaner flotation, wherein the sulfoxy reagent is added to a solution derived from a regrind circuit, wherein the slurried valuable metal- and oxygen-containing feed material is a rougher concentrate of a rougher flotation, wherein the slurried valuable metal- and oxygen-containing feed material is free of contact with a sulfoxy reagent prior to the rougher flotation, and wherein more than 200 g/t of sulfoxy reagent is added to the slurried valuable metal- and oxygen-containing feed material.

25. The process of claim 22, wherein at least about 50 g/t of the sulfoxy reagent is added to the slurried valuable metal- and oxygen-containing feed material.

26. The process of claim 22, wherein the floating step is a cleaner flotation, wherein the slurried valuable metal- and oxygen-containing feed material is a rougher concentrate of a rougher flotation, and wherein the slurried valuable metal- and oxygen-containing feed material is free of contact with a sulfoxy reagent prior to the rougher flotation.

27. The process of claim 22, wherein the sulfoxy reagent is one or more of an ammonium, hydrogen, alkali, or alkaline earth metal sulfite, bisulfite, and metabisulfite.

28. The process of claim 22, wherein the gangue sulfide mineral further comprises at least one of marcasite, arsenopyrite, and pyrrhotite.

29. A with process for recovering one or more metals, comprising: providing a slurried valuable metal-containing feed material comprising a valuable metal sulfide mineral and a second sulfide mineral comprising pyrite to be separated from the valuable metal sulfide mineral, wherein the valuable metal sulfide mineral is at least one of a copper sulfide and molybdenum sulfide, and wherein the slurried valuable metal-containing feed material comprises water having at least one of: a buffered water having one or more of a salinity of about 0.01% or more and a total dissolved solids of at least about 10,000 mg/L, a brackish water having one or more of a salinity of about 0.01% or more and a total dissolved solids of at least about 10,000 mg/L, a fresh water having a salinity of about 0.01% or more, a salt water having one or more of a salinity of about 25 parts per thousand (2.5%) or more, and a mixture thereof; aerating, with a molecular oxygen-containing gas, the slurried valuable metal-containing feed material to form an aerated slurried feed material; contacting at least a portion of the aerated slurried feed material with a sulfoxy reagent, in the presence of dissolved molecular oxygen, to form a sulfoxylated slurry; and floating the sulfoxylated slurry to form a concentrate.

30. A process for recovering one or more metals, comprising: providing an oxygenated, slurried valuable metal-containing feed material comprising a valuable metal sulfide mineral, wherein the oxygenated, slurried valuable metal-containing feed material comprises a water having a salinity of about 0.1 parts per thousand (0.01%) or more, and a gangue sulfide mineral comprising iron pyrite; and contacting the oxygenated, slurried valuable metal-containing feed material, while maintaining the dissolved oxygen content of the oxygenated, slurried valuable metal-containing feed material at a level of at least about 3 ppm, with a sulfoxy reagent to form a treated slurried feed material; and floating the treated slurried feed material to form a concentrate comprising the valuable metal sulfide mineral and tailings comprising the iron pyrite.

31. The process of claim 30, wherein the oxygenated, slurried valuable metal-containing feed material is free of pH adjustment before and during the floating step.

32. The process of claim 30, wherein the oxygenated, slurried valuable metal-containing feed material has a pH of less than pH 8.5.

33. The process of claim 30, wherein, prior to the floating step, the oxygenated, slurried valuable metal-containing feed material is not contacted with an externally generated non-oxidizing gas to lower a dissolved molecular oxygen content of the oxygenated, slurried valuable metal-containing feed material.

34. The process of claim 30, wherein at least about 50 g/t of the sulfoxy reagent is added to the oxygenated, slurried valuable metal-containing feed material.

35. The process of claim 30, wherein the floating step is a cleaner flotation, wherein the oxygenated, slurried valuable metal-containing feed material is a rougher concentrate of a rougher flotation, and wherein the oxygenated, slurried valuable metal-containing feed material is free of contact with a sulfoxy reagent prior to the rougher flotation.

36. The process of claim 30, wherein the sulfoxy reagent is one or more of an ammonium, hydrogen, alkali, or alkaline earth metal sulfite, bisulfite, and metabisulfite.

37. The process of claim 30, wherein the gangue sulfide mineral further comprises at least one of marcasite, arsenopyrite, and pyrrhotite.

38. The process of claim 30, wherein the valuable metal sulfide mineral comprises at least one of a copper sulfide and molybdenum sulfide, wherein the floating step is cleaner flotation, wherein the sulfoxy reagent is added to a solution derived from a regrind circuit, wherein the oxygenated, slurried valuable metal-containing feed material is a rougher concentrate of a rougher flotation, wherein the oxygenated, slurried valuable metal-containing feed material is free of contact with a sulfoxy reagent prior to the rougher flotation, and wherein more than 200 g/t of sulfoxy reagent is added to the oxygenated, slurried valuable metal-containing feed material.

39. The process of claim 30, wherein, prior to the floating step, the oxygenated, slurried valuable metal-containing feed material is not contacted with an externally generated non-oxidizing gas to lower a dissolved molecular oxygen content of the oxygenated, slurried valuable metal-containing feed material, and wherein the oxygenated, slurried valuable metal-containing feed material has a pH of less than about pH 8.5.

40. The process of claim 30, wherein the floating step is a cleaner flotation, wherein the sulfoxy reagent is added to an aqueous slurry derived from the valuable metal sulfide mineral in a mill, wherein the mill is in a regrind circuit, wherein the oxygenated, slurried valuable metal-containing feed material is a rougher concentrate of a rougher flotation, and wherein the oxygenated, slurried valuable metal-containing feed material is free of contact with a sulfoxy reagent prior to rougher flotation.

41. The process of claim 30, wherein the contacting step comprises contacting the sulfoxy reagent with a freshly exposed and unoxidized surface of the valuable metal sulfide mineral.

42. The process of claim 30, wherein the contacting of the sulfoxy reagent with the oxygenated, slurried valuable metal-containing feed material occurs during one or both of a primary and secondary comminution.

43. The process of claim 30, wherein the valuable metal sulfide mineral contains one or both of gold and silver.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings are incorporated into and form a part of the specification to illustrate several examples of the present invention(s). These drawings, together with the description, explain the principles of the invention(s). The drawings simply illustrate preferred and alternative examples of how the invention(s) can be made and used and are not to be construed as limiting the invention(s) to only the illustrated and described examples. Further features and advantages will become apparent from the following, more detailed, description of the various embodiments of the invention(s), as illustrated by the drawings referenced below.

(2) FIG. 1 is a flowchart of a process according to an embodiment;

(3) FIGS. 2A-B are a flowchart of a process according to an embodiment;

(4) FIG. 3 is a flowchart of a process according to an embodiment;

(5) FIG. 4 is a flowchart of a process according to an embodiment;

(6) FIG. 5 is a copper recovery curve for various flotation reagent schemes in tap water and plots copper grade (%) against copper recovery (%);

(7) FIG. 6 is a copper recovery curve for various flotation reagent schemes in salt water and plots copper grade (%) against copper recovery (%);

(8) FIG. 7 is a copper recovery curve for various flotation reagent schemes in tap water and plots copper grade (%) against copper recovery (%);

(9) FIG. 8 is a copper recovery curve for various flotation reagent schemes in salt water and plots copper grade (%) against copper recovery (%);

(10) FIG. 9 is a copper recovery curve in salt water and tap water with MBS addition, with and without aeration, and plots copper grade (%) against copper recovery (%); and

(11) FIG. 10 is a copper recovery curve in brackish site water and tap water with MBS addition, with and without aeration, and plots copper grade (%) against copper recovery.

DETAILED DESCRIPTION

(12) The process described herein employs the addition of a sulfoxy reagent, preferably a metabisulfite, to one or more points in a flotation circuit. In one process configuration, the addition of the sulfoxy reagent is preceded by a period of, typically intense, aeration, in which an oxidizing atmosphere and dissolved molecular oxygen is actively promoted, rather than prevented or inhibited. The combination of aeration with sulfoxy reagent addition, without adjustment of the pH of the resulting pulp with a base, such as lime, caustic soda, or soda ash, or an acid, such as sulfuric acid, and in the absence of sulfide depressants, such as cyanide or hydrosulfide, can show a marked improvement over the addition of a sulfoxy reagent without, or in the absence of, the aeration step and can be more cost effective in terms of recovery and reagent consumption than conventional processes that employ base and/or sulfide depressant addition. In addition, the process can have superior performance when used in water containing negligible to a significant amount of salinity. This process can be particularly useful for concentrator operations whose only available source of water is sea water or brackish ground water. In other embodiments, the sulfoxy reagent is introduced not only after aeration but additionally in a grinding circuit, particularly the secondary grinding circuit.

(13) Referring to FIG. 1, a valuable metal-containing feed material 100 can be any suitable copper- and/or molybdenum containing material, particularly mined ore, tailings, concentrate, or other residue of a metal recovery process. The feed material 100 includes not only one or more copper and/or molybdenum sulfide minerals but also one or more other sulfide minerals (particularly sulfidic gangue minerals) to be separated from the valuable metal sulfide mineral(s)). Typically, the feed material 100 is polymetallic, with some or all of the metals being present as a sulfide. A common feed material 100 includes copper in the form of one or more of chalcopyrite, chalcocite, bornite, covellite, tennantite, enargite, and tetrahedrite and/or molybdenum in the form of molybdenite as the valuable metal sulfide mineral and an iron sulfide mineral that is one or more of pyrite, marcasite, arsenopyrite, and pyrrhotite, as a sulfidic gangue mineral. Gold or silver is typically present. In many applications, iron sulfide is the primary (e.g., more than 50% of the) sulfidic gangue mineral in the feed material 100.

(14) In step 104, the material 100 is slurried and comminuted in an open or closed milling circuit. The comminuted feed material 108 is forwarded to an aeration step 112 prior to the sulfoxy reagent addition step 114.

(15) The water used in forming the slurry of the material 100 can be fresh water, brackish groundwater, saltwater, or any mixture thereof. The process is surprisingly effective in floating valuable metal sulfide minerals whether or not the water is saline and contains dissolved solids or is fresh water. In one process configuration, for example, the water has a salinity of about 0.1 parts per thousand (0.01%) or more.

(16) The optimum liberation size of the material 100 depends on ore type, an understanding of the ore liberation and solution chemistry of the ore, and power and media costs.

(17) The comminuted feed material 108 is in the form of a slurry, preferably having a feed pulp density ranging from about 20 to about 45 wt. %.

(18) The comminuted feed material 108 is subjected to aeration in step 112 in a suitable vessel to form an aerated feed material 132. Aeration is typically performed by sparging, under agitation, an oxidizing gas, preferably a molecular oxygen-containing gas (such as air, substantially pure molecular oxygen, and molecular oxygen-enriched air) through the feed material 108. The oxidizing gas preferably includes at least about 20 vol. % molecular oxygen. Aeration is performed for a time sufficient to allow a thin layer of surface oxidation to form on the surface of the copper and/or molybdenum sulfide minerals 108. The residence time required to produce the desired oxidized film ranges preferably from about 15 to about 120 minutes and more preferably from about 30 to about 60 minutes. In most applications, the pH is not adjusted during aeration or any steps subsequent to aeration.

(19) While not wishing to be bound by any theory, the thin layer of surface oxidation on the copper and/or molybdenum sulfide minerals allows better collector adsorption by the mineral. This is surprising to one of ordinary skill in the art, who would believe that aeration leads to oxidation of the copper and molybdenum sulfide minerals causing reduced floatability and reduced stability of the sulfoxy compound.

(20) In step 114, the sulfoxy reagent 118 is added to the aerated feed material 132 to form a treated feed material 122. Sulfoxy reagent 118 can be added in any suitable manner. Unlike conventional processes, the sulfoxy reagent 118 is added while the aerated feed material 132 is oxygenated. In other words, dissolved molecular oxygen is not removed from the comminuted feed material prior to sulfoxy reagent 118 addition. The dissolved molecular oxygen level in the aerated feed material 132 during conditioning is preferably at least about 3 ppm, more preferably at least about 5 ppm, and even more preferably at least about 10 ppm.

(21) The sulfoxy reagent 118 can be any sulfoxy compound, such as an ammonium, hydrogen, alkali metal, or alkaline earth metal sulfite, bisulfite, metabisulfite, sulfide, polysulfide, thiosulfate, polythionate, or bisulfide, sulfur dioxide, and mixtures and derivatives thereof. The preferred sulfoxy reagent 118 is one or more of an ammonium, hydrogen, alkali metal, or alkaline earth metal sulfite, bisulfite, or metabisulfite, and/or sulfur dioxide, with an ammonium, hydrogen, alkali metal, or alkaline earth metal metabisulfite being even more preferred. While not wishing to be bound by any theory, the sulfoxy reagent 118 is believed to act as a depressant of other sulfide minerals (e.g., iron sulfide gangue minerals, particularly pyrite). As will be appreciated by one of ordinary skill in the art, sulfite ion can be added or formed in situ by a suitable chemical reaction between sulfite ion precursors.

(22) There are a number of different process configurations for sulfoxy reagent 118 addition. In one process configuration, a portion of the sulfoxy reagent 118 is added in one stage, optionally during grinding, with additional amounts being added after aeration and before each of the cleaning, recleaning or scavenging flotation stages. In another process configuration, the majority of the sulfoxy reagent 118 is added in one or more stages after aeration, with additional smaller amounts being optionally added before each of the cleaning, recleaning or scavenging flotation stages. In another process configuration, no sulfoxy reagent 118 is added during any grinding stage but only after aeration. The typical cumulative sulfoxy reagent 118 addition rate, for all addition points, is at least about 50 g/t, more typically at least about 100 g/t, more typically more than 200 g/t, and even more typically from more than 200 g/t to about 1,000 g/t.

(23) While not wishing to be bound by any theory, it is believed that the sulfoxy reagent and oxidizing gas act synergistically to enhance substantially separation selectively and effectiveness, particularly in highly buffering and/or saline waters. While aeration is believed to oxidize sulfide mineral surfaces, which increases floatability of the valuable metal sulfide mineral, the addition of sulfoxy reagent after aeration is believed to control optimally the depression of the other sulfide mineral to be removed as tailings. The increase in floatability, for example, of copper sulfide minerals with aeration while depressing pyrite with the sulfoxy reagent can allow a much improved flotation selectivity than is possible in the absence of aeration. This synergistic effect is best realized when aeration and sulfoxy reagent addition occur sequentially, with aeration preceding sulfoxy reagent addition.

(24) In step 116, the treated feed material 122 is conditioned to form an aerated and conditioned feed material 134. Conditioning is performed in a suitable vessel, or pulp conditioning tank, prior to flotation. In flotation, the amount of agitation and consequent dispersion during conditioning are closely associated with the time required for physical and chemical reactions to take place.

(25) A number of reagents can be added during conditioning, including a collector 120, a frother 124, and other reagents 128. Any suitable collector 120 and frother 124 may be employed. Other reagents 128 include activators, depressants (such as a carbon depressant to depress the flotation of carbonaceous and/or graphitic material), clay dispersants, modifiers, lime (in limited situations as a low cost dispersant or viscosity modifier as examples), and reagents to control electro potential (Eh) and/or pH. Depending on the type of agitation during conditioning, the level of oxygenation may increase. For a downflow agitator, additional molecular oxygen will likely be entrained in the slurry. Conditioning typically occurs for a period between about 0.5 to about 60 minutes and even more typically between about 2 to about 30 minutes.

(26) The aerated and conditioned feed material 134 is floated in step 136, preferably in the presence of sparged air, to form a concentrate fraction 144 commonly containing about 25% or more, more commonly about 40% or more, and even more commonly more than about 50% of the valuable metal sulfide minerals and a tailings fraction 140 commonly containing about 25% or more, more commonly about 40% or more, and even more commonly more than about 50% of the sulfide mineral(s) to be removed as tailings. In the flotation circuit, the aerated and conditioned feed material 134 is floated in a bank, or series, of flotation machines. The flotation machines can be aerated flotation cells.

(27) Flotation may include one or more stages, depending on the application. The number and configuration of roughing, scavenging, and cleaning stages are determined based on criteria known to those skilled in the art.

(28) The selection of the collector 120, frother 124, and other reagents 128 for a specific feed material as well as the pulp density, addition rates of the reagents, order of reagent addition, rate of air addition during flotation, Eh, and other flotation conditions and parameters are also well known to those of ordinary skill in the art.

(29) In one process configuration, the comminution step 104, aeration step 112, conditioning step 116, and flotation step 136 are performed in the substantial or complete absence of pH adjustment by an acid or base (e.g., in the absence of acid or base (e.g., lime, soda ash, and/or caustic soda) addition). In other words, the steps are performed at natural pH, which, for many ores and makeup water, is an alkaline pH of no more than about pH 11, more typically a pH of less than pH 8.5, more typically a pH of no more than about pH 8, and even more typically a pH ranging from about pH 3 to about pH 8. The Eh will typically be greater than about 5 mV and less than about 155 mV and more typically range from about 10 to about 120 mV.

(30) In one process configuration, the comminution step 104, aeration step 112, conditioning step 116, and flotation step 136 are performed in the substantial or complete absence of dissolved molecular oxygen reduction by sparging the slurried feed material with a non-oxidizing gas. The non-oxidizing gas has little, if any, oxidant content and is primarily, if not entirely, an inert gas (e.g., nitrogen and argon), a reducing gas (e.g., a reducing gas other than sulfur dioxide such as carbon dioxide, carbon monoxide, methane, ethane, and/or propane), or a mixture thereof. In one process configuration, the added sulfoxy reagent 118 is substantially free of sulfur dioxide gas. By eliminating sparging by the non-oxidizing gas, a relatively high level of dissolved molecular oxygen can be maintained in the slurry before and after aeration.

(31) Another process configuration will now be discussed with reference to FIGS. 2A-B. In this example, the valuable metal sulfide mineral is a copper sulfide and the other sulfide mineral (or sulfidic gangue mineral) is one or more of pyrite, marcasite, pyrrhotite, and arsenopyrite.

(32) The valuable metal-containing feed material 100 is comminuted in step 104 to form a comminuted feed material 108.

(33) The comminuted feed material 108 is conditioned in step 116 to form a conditioned feed material 132. The reagents added during conditioning are the collector 120, frother 124, and other reagents 128. No sulfoxy reagent 118 is added.

(34) The conditioned feed material 132 is subjected to rougher flotation in step 200 to form rougher tailings 204 and rougher concentrate 208. While most of the valuable metal sulfide minerals remain in the rougher concentrate 208, the rougher tailings 204 contain a significant portion of the sulfide gangue minerals. As can be seen from FIG. 2A, no sulfoxy reagent 118 has been added prior to rougher flotation.

(35) In step 228, the rougher and scavenger concentrate 208 and 220, respectively, are combined, pulp density adjusted, and recomminuted, in a closed or open comminution circuit, to form a recomminuted concentrate 232. As will be appreciated, the floated iron sulfide minerals in the concentrate fraction 208 are more difficult to separate and require further comminution for effective liberation to be realized.

(36) Sulfoxy reagent 118 may optionally be added during secondary comminution and after aeration. Addition of the sulfoxy reagent in the mill can allow immediate adsorption of the sulfoxy radical on fresh and unoxidized sulfide mineral surfaces. In one configuration, more sulfoxy reagent 118 is added before cleaner flotation than at any other point during the process.

(37) In step 212, the rougher tailings 204 are further conditioned by the addition of collector 120, and, in step 216, the conditioned rougher tailings are subjected to scavenger flotation 216 to produce a scavenger concentrate 220 and scavenger tailings 224. Slower floating copper sulfide minerals are floated during scavenger flotation. The scavenger concentrate 220 is combined with the rougher concentrate 208 and subjected to secondary comminution.

(38) Following secondary comminution step 228, the recomminuted concentrate 232 is subjected, in step 112, to aeration to form an aerated concentrate 236.

(39) In optional step 114, sulfoxy reagent 118 is added to form a treated rougher concentrate 238.

(40) In step 116, the aerated or treated rougher concentrate 236 (as appropriate) is conditioned to form a conditioned concentrate 240. Reagents added during conditioning are the collector 120, frother 124, and other reagents 128. Typically, aeration, sulfoxy reagent addition, and conditioning occur in different vessels, and the dissolved molecular oxygen after aeration is not, prior to sulfoxy reagent addition, reduced by introduction of a non-oxidizing gas.

(41) In step 248, the conditioned concentrate 240 is subjected to cleaner flotation to form cleaner tailings 252 and cleaner concentrate 250. While most of the valuable metal sulfide minerals in the conditioned concentrate 240 remain in the cleaner concentrate 250, the cleaner tailings 252 contain a portion of the valuable sulfide minerals in the conditioned concentrate 240. The cleaner tailings contain a significant amount of the gangue sulfide minerals.

(42) In optional step 114, sulfoxy reagent 118 is added to the cleaner tailings to form a treated cleaner tailings 262.

(43) In step 256, the cleaner tailings 252 or treated cleaner tailings 262 (as the case may be) are conditioned by addition of collector 120 to form conditioned cleaner tailings 260. The conditioned cleaner tailings 260 are subjected to cleaner scavenger flotation in step 264 to form cleaner scavenger tailings 268 and concentrate 272. While most of the valuable metal sulfide minerals in the cleaner tailings 252 remain in the cleaner scavenger concentrate 272, the cleaner scavenger tailings 268 contain a significant portion of the sulfide gangue minerals in the cleaner tailings 252. The cleaner scavenger concentrate 272 is returned to the secondary comminution step 228.

(44) Returning to the cleaner concentrate 250, sulfoxy reagent 118 is, in step 114, optionally added to the cleaner concentrate to form a treated cleaner concentrate 252.

(45) The cleaner concentrate 250 or treated cleaner concentrate 252 (as appropriate) is conditioned in step 274 to form a conditioned cleaner concentrate 276. During conditioning, collector 120 is added.

(46) The conditioned cleaner concentrate 276, in step 278, is subjected to first recleaner flotation to form first recleaner tailings 282 and first recleaner concentrate 280. The first recleaner tailings 282 are returned to the secondary comminution step 228.

(47) In optional step 114, sulfoxy reagent 118 is added to the first recleaner concentrate 280 to form a treated recleaner concentrate 281.

(48) The first recleaner concentrate 280 or treated recleaner concentrate 281 (as the case may be) is conditioned, in step 284, to form a conditioned first recleaner concentrate 286. During conditioning, the first recleaner concentrate 280 collector 120 is added.

(49) In step 288, the conditioned first recleaner concentrate 286 is subjected to second recleaner flotation 288 to form second recleaner tailings 290, which includes preferably at least most and more preferably about 70% or more of the sulfidic gangue minerals in the valuable metal-containing feed material 100, and second recleaner concentrate 292, which includes preferably at least most and more preferably about 70% or more of the valuable metal sulfide minerals in the valuable metal-containing feed material 100.

(50) In the above process, cleaner flotation, cleaner scavenger, and first and second recleaner flotation steps 244, 264, 278, and 288, respectively, are performed at natural pH and ambient temperature.

(51) In the above process, it may be desirable to perform an additional aeration step preceding one or more of the sulfoxy reagent addition steps performed downstream of rougher flotation. Whether or not an additional aeration step is performed depends on the oxidation potential of the slurry before further sulfoxy reagent and collector addition. Prior conditioning, aerating, and floating steps will introduce additional dissolved molecular oxygen into the various slurry streams.

(52) As will be appreciated, other process configurations may be employed depending on the feed material type and mineralogy.

EXPERIMENTAL

(53) The following examples are provided to illustrate certain embodiments of the invention and are not to be construed as limitations on the invention, as set forth in the appended claims. All parts and percentages are by weight unless otherwise specified.

Example 1Conventional Flotation Methods

(54) This example demonstrates the effect that the composition of water employed in the flotation pulp has on the recovery of copper, when various reagents are used to depress pyrite and concentrate copper. As shown in Table 1, the salt water employed has considerably higher total dissolved solids content and conductivity than the tap water.

(55) TABLE-US-00001 TABLE 1 Composition of Tap and Highly Buffered Site Water Parameter Units Tap Water Salt Water pH pH 7.81 8.48 Conductivity S/cm 0.96 5360 TDS mg/L 405 40225 Sodium mg/L 191 12060 Potassium mg/L 9.3 414 Calcium mg/L 332 426 Magnesium mg/L 10.4 1297 Iron mg/L 0.17 <0.10 Chloride mg/L 199 20738 Bicarbonate mg/L 120 70 Sulfate mg/L NIL 2890

(56) FIG. 3 is a simplified flow diagram of the kinetics tests conducted in this example. The flow diagram includes comminuted feed material conditioning 300 to form a conditioned feed material 304, rougher flotation 308 of the conditioned feed material 304 (using five flotation machines) to form rougher tailings 312 and rougher concentrate 316, secondary comminution 320 of the rougher concentrate 316 to form recomminuted rougher tailings 324, first cleaner flotation 328 of the recomminuted rougher tailings 324 to form a first cleaner concentrate 332 and first cleaner tailings 336, second cleaner flotation 344 of the first cleaner concentrate 332 to form second cleaner concentrates 1,2 348 and second cleaner tailings 352, and cleaner scavenger flotation 340 of the first cleaner tailings 336 to form a cleaner scavenger concentrate 356 and cleaner scavenger tailings 360.

(57) The five rougher stages for the kinetics tests described below were performed in a similar manner using two water sources: tap water, and water with a high degree of Total Dissolve Solids (TDS) (Salt Water). All tests were carried out on ore ground to P.sub.80 212 microns for the rougher stages and reground to P.sub.80 20-25 microns for the cleaner scavenger. Other than reagent addition, the tests were carried out using the same conditions.

(58) The effect of different reagent additions on sulfide depression and the associated copper grade/recovery was investigated. The reagents employed were none, lime, lime and sodium cyanide, and lime cyanide and Potassium Amyl Xanthate (PAX).

(59) The composition of the feed (ore) material employed in all the tests is shown in Table 2. The initial feed pulp density was 34%. The experimental conditions are shown below in Table 3.

(60) TABLE-US-00002 TABLE 2 Feed ore employed in flotation tests with tap and salt water Parameter Unit Assay Copper % 0.478 Iron % 3.66 Gold g/t 0.28 Total Sulfur % 4.34 Sulfide Sulfur % 1.84

(61) TABLE-US-00003 TABLE 3 Reagent addition and operating conditions for flotation tests performed with tap and salt water Reagent Addition Float pH Eh mV A3894 MX950 PAX NACN MIBC Lime time Test Description rougher cleaner rougher cleaner (g/t) (g/t) (g/t) (g/t) drops (g/t) (min) Tap Water Baseline 7.3 7.2 98 121 9 37 0 16 0 30.5 Baseline with lime 7.35 10.2 119 4 9 37 0 7 295 30.5 Baseline with lime and cyanide 7.4 10.2 127 27 9 37 20 11 205 30.5 Baseline with lime, cyanide and PAX 7.5 10.2 105 27 21 46 20 10 220 30.5 Salt Water Baseline 7.1 7 154 125 9 37 0 16 0 30.5 Baseline with lime 7.2 10.2 126 7 9 37 0 16 2480 30.5 Baseline with lime and cyanide 7.4 10.2 96 21 9 37 20 11 1500 30.5 Baseline with lime, cyanide and PAX 7.4 10.0* 108 16 21 46 20 12 1820 30.5

(62) FIGS. 5 and 6 above show the grade recovery curves for the four reagent schemes for tap water and salt water, respectively. For all of the reagent schemes tested, the grade recovery curves for low TDS tap water were better than than those achieved with salt water. Tap water with Lime Cyanide and PAX has the best grade recovery curve. Compared to tap water, conventional techniques employed for pyrite depression do not perform as well in salt water.

Example 2Aeration/Sulfoxy Reagent Methods

(63) Additional tests were conducted using a similar flotation circuit as employed in example 1 with the exception of the addition of 300 g/t before the first stage of cleaner flotation and an additional 300 g/t metabisulfite (MBS) (the sulfoxy reagent) during the secondary grind. In other words and as shown in Table 4 below, a total of 600 g/t MBS has been added in the flotation circuit.

(64) The flotation circuit is shown in the flow chart of FIG. 4. The flow chart includes conditioning 400 of the comminuted feed material 108 to form conditioned feed material 404, rougher flotation 408 (using five flotation machines or stages) to form rougher concentrate and tailings fractions 412 and 416, respectively, secondary comminution 420 of the rougher concentrate 412, in the presence of sulfoxy reagent 118, to form a recomminuted rougher concentrate 412, aeration 112 of the recomminuted rougher concentrate 412 (for 0 (which means no aeration was performed) or 30 minutes) to form aerated recomminuted rougher concentrate 428, sulfoxy reagent 118 addition prior to cleaner flotation 432, and cleaner flotation 432 of the aerated recomminuted rougher concentrate 428 to form cleaner concentrate 1-6 and cleaner tailings 436 and 440, respectively.

(65) Again, the same two types of water where employed: tap water and salt water with a high degree of TDS (Salt Water). All tests were carried out on feed (ore) material ground to P.sub.80 212 microns for the five rougher stages and reground to P.sub.80 20-25 microns for the cleaner scavenger. Other than reagent addition, the tests were carried out using the same conditions. The initial feed pulp density was about 34%, and the feed (ore) material was the same as that employed in example 1. The experimental conditions are shown below in Table 4. The tests were carried out with and without a 30-minute aeration step after the secondary comminution step, or secondary grind, and prior to the cleaning flotation circuit. The effect of the aeration before MBS addition on sulfide depression and copper grade/recovery was investigated. For reference, the grade recovery curve with lime cyanide and PAX is shown.

(66) TABLE-US-00004 TABLE 4 Reagent addition and operating conditions for flotation tests performed with tap and salt water Reagent Addition Float pH Eh mV A3894 MX950 MBS MIBC Lime time Test Description rougher cleaner rougher cleaner (g/t) (g/t) (g/t) drops (g/t) (min) Site Water MBS with aeration 7.4 5.6 115 85 9 37 600 13 0 30.5 MBS with no aeration 7.4 4.8 91 95 9 37 600 12 0 30.5 Salt Water MBS with aeration 7.5 5.2 101 94 9 37 600 12 0 30.5 MBS with no aeration 7.5 4.9 103 90 9 37 600 14 0 31.5

(67) As can be observed from the grade recovery curves of FIGS. 7-8, the use of MBS improves the copper grade recovery curves in both water types. The effect is most pronounced in salt water. However, it is not until aeration is employed that the grade recovery achieved in salt water begins to approximate that observed in the tap water. A graph more clearly comparing the copper grade recovery, with and without aeration, is shown in FIG. 9. In salt water, MBS addition improves the copper recovery from 50% to 75% at the same copper grade of 32%.

Example 3Aeration/Sulfoxy Reagent Methods

(68) Additional tests were conducted using the same flotation circuit of FIG. 4 as employed in example 2, with the exception that brackish site water was employed. Analysis of the site water is shown in Table 5. The tests were carried out, with and without, a 30-minute aeration step after the secondary grind and prior to the cleaning flotation circuit. The effect of the aeration, after MBS addition, on sulfide depression and copper grade/recovery was investigated. For reference the grade recovery curve with tap water is shown in FIG. 10.

(69) TABLE-US-00005 TABLE 5 Composition of Tap and Highly Buffered Site Water Parameter Units Site Water pH pH 7.02 Conductivity S/cm 10.38 TDS mg/L 7515 Sodium mg/L 1940 Potassium mg/L 11.2 Calcium mg/L 620 Magnesium mg/L 84.5 Iron mg/L <0.10 Chloride mg/L 2535 Bicarbonate mg/L 30 Sulfate mg/L 1198

Example 4Locked Cycle Testing

(70) Locked cycle tests were performed using differing ore types and a saline and buffered site water to compare flotation performed using sulfoxy reagent addition with that performed using cyanide as a depressant in the absence of aeration and sulfoxy reagent addition. The various ores were copper sulfide ores containing substantial levels of iron sulfides. Actual locked cycle tests using site water are generally deemed to provide more valuable information than open cleaner tests. A summary of the locked cycle tests is presented in Tables 6-7:

(71) TABLE-US-00006 TABLE 6 Locked cycle test results for the drop weight samples using the cyanide as a depressant and site water Head Conc % of ore grade Grade Mass Recovery Comp No deposit Cu, % Cu, % Pull Cu, % 1 5.0 0.59 28.3 1.9 91.7 2 2.0 0.42 28.2 1.08 72.2 3 5.0 0.61 32.9 1.51 80.9 4 3.0 0.51 31.3 1.41 86.1 5 3.0 0.69 30.5 1.88 83.6 6 4.0 0.43 33.3 1.14 88.5 7 6.0 0.36 25.4 1.1 78 8 5.0 0.67 29.8 2.01 89.5 9 7.0 0.60 34 1.59 89.9 10 9.0 0.61 32.2 1.7 90.1 11 4.0 0.56 29.8 1.66 87.5 12 11.0 0.51 32.9 1.37 88.8 13 5.0 0.56 26.7 1.64 81 14 1.0 0.64 31 1.73 84.5 15 8.0 0.52 28.7 1.42 78.5 16 4.0 0.53 30.7 1.49 87.1 Weighted 0.55 30.59 1.53 85.7 average

(72) TABLE-US-00007 TABLE 7 Locked cycle test results for the drop weight samples using the Aeration/Metabisulfite Process and site water % of Conc Comp ore Head Grade Mass Recovery No deposit grade Cu, % Cu, % Pull Cu, % 1 5.0 0.6 33.7 1.66 93.6 2 2.0 0.44 33.6 1.2 92.1 3 5.0 0.63 36.6 1.66 92.2 4 3.0 0.51 34.4 1.38 93.3 5 3.0 0.7 34 1.98 93.8 6 4.0 0.44 34.7 1.09 91.3 7 6.0 0.41 29 1.32 92.6 8 5.0 0.75 37.6 1.09 87.6 9 7.0 0.60 37.4 1.49 91 10 9.0 0.57 33.3 1.65 90.4 11 4.0 0.6 34.7 1.58 91.7 12 11.0 0.48 33.2 1.44 92.4 13 5.0 0.56 24.8 2.11 90.6 14 1.0 0.6 33.7 1.78 93.5 15 8.0 0.51 32 1.43 90.3 16 4.0 0.53 36.8 1.3 90.1 Weighted 0.55 33.55 1.50 91.42 average

(73) Both Tables 6-7 show that flotation with aeration followed by ammonium metabisulfite addition yielded significantly better results than flotation using cyanide as an iron sulfide depressant. On average, copper recovery was about 6% higher with about a 3% higher copper concentrate grade for flotation performed with aeration followed by ammonium metabisulfite addition.

(74) A number of variations and modifications of the invention can be used. It would be possible to provide for some features of the invention without providing others.

(75) For example, the sulfoxy reagent has different modes of operation depending on the mineralogies and slurry conditions (e.g., Eh and pH) involved. Sulfoxy reagent, for example, can act as a depressant and/or activator for the same sulfide mineral under differing slurry conditions or as a depressant for one sulfide mineral and/or activator for a different sulfide mineral under a common set of conditions. For example, under one set of conditions, the sulfoxy reagent activates flotation of copper, lead, and zinc sulfides and under a different set of conditions activates flotation only of copper sulfides and not lead and zinc sulfides. In another example, the sulfoxy reagent depresses flotation of zinc sulfide but not lead sulfide.

(76) In other examples, the concentrate and tailings can each include different valuable metal sulfide minerals. The valuable metal in the tailings can later be isolated from any gangue sulfide minerals by subsequent flotation stages. Examples of base metal mixed sulfide ores amenable to the process discussed herein include copper-gold (e.g., as calaverite (AuTe2) or sylvanite (Au,Ag)Te2)), copper-gold-silver (e.g., as acanthite (Ag2S), sylvanite (Au,Ag)Te2), pyrargyrite (Ag3SbS3), and proustite (Ag3AsS3)), lead (e.g., as galena (PbS), altaite (PbTe), bournonite (PbCuSb S3), jamesonite (Pb4FeSb6S14), and cylindrite (Pb3Sn4FeSb2S14))-zinc (e.g., as sphalerite (ZnS))-copper, copper-zinc, and copper-molybdenum. Massive sulfide ores, for instance, usually contain sulfides of three or more valuable metals as well as gangue sulfide minerals, such as pyrite.

(77) The present invention, in various embodiments, configurations, or aspects, includes components, methods, processes, systems and/or apparatus substantially as depicted and described herein, including various embodiments, configurations, aspects, subcombinations, and subsets thereof. Those of skill in the art will understand how to make and use the present invention after understanding the present disclosure. The present invention, in various embodiments, configurations, and aspects, includes providing devices and processes in the absence of items not depicted and/or described herein or in various embodiments, configurations, or aspects hereof, including in the absence of such items as may have been used in previous devices or processes, e.g., for improving performance, achieving ease and\or reducing cost of implementation.

(78) The foregoing discussion of the invention has been presented for purposes of illustration and description. The foregoing is not intended to limit the invention to the form or forms disclosed herein. In the foregoing Detailed Description for example, various features of the invention are grouped together in one or more embodiments, configurations, or aspects for the purpose of streamlining the disclosure. The features of the embodiments, configurations, or aspects of the invention may be combined in alternate embodiments, configurations, or aspects other than those discussed above. This method of disclosure is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment, configuration, or aspect. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate preferred embodiment of the invention.

(79) Moreover, though the description of the invention has included description of one or more embodiments, configurations, or aspects and certain variations and modifications, other variations, combinations, and modifications are within the scope of the invention, e.g., as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative embodiments, configurations, or aspects to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter.