OA12943A

OA12943A - Process for the beneficiation of sulfide minerals.

Info

Publication number: OA12943A
Application number: OA1200500111A
Authority: OA
Inventors: Alan S Rothenberg; Lino G Magliocco
Original assignee: Cytec Tech Corp
Priority date: 2002-10-15
Filing date: 2003-10-01
Publication date: 2006-10-13
Also published as: PL202110B1; AU2003279843B2; EP1556170B1; AP1920A; BR0315150B1; CA2501079C; MXPA05003708A; ATE356670T1; EP1556170A1; BR0315150A; AR041586A1; PL375072A1; PE20040429A1; RU2005114538A; CA2501079A1; AP2005003271A0; PT1556170E; AU2003279843A1; DE60312541D1; RU2318607C2

Abstract

Froth flotation processes, useful for beneficiating base metal m ineral values from metal sulfide ore, utilize a collector comprising an N-butoxycarbonyl-O-alkylthionocarbamate selected from the group consisting of N-butoxycarbonyl-O-methylthionocarbamate, N-butoxycarbonyl-O-etkylthionocarbamate, N-butoxycarbonyl-O-propylthiononocarbamate, N-butoxycarbonyl-O-buylthionocarbamate, N-butoxycarbonyl-O-pentylthionocarbamate, and N-butoxycarbonyl-O-hexylthionocarbamate.

Description

1 012943

PROCESS FOR THE BENEFICIATION OF SULFIDE MINERALS

Background of the Invention

Field of the Invention [0001] This invention relates to froth flotation processes for the recovery of meta] 05 values trôna base métal sulfide ores. More particularly, it relates to processes tirât employsulfide minerai collectors comprising certain N-butoxycarbonyl-O-alkylthionocarbamatecompounds which exhibit excellent metallurgical performance over a broad range of pHvalues.

Description of the Related Art 10 [0002] Froth flotation is a widely used process for benefîciating ores containing valuable minerais. A typical froth flotation process involves inteimixing an aqueous slurrycontaining finely ground ore particles with a trothing or foaming agent to produce a froth.Ore particles that contain the desired minerai are preferentially attracted to the froth becauseof an affinity between the froth and the exposed minerai on the surfaces of the ore particles. 15 The resulting beneficiated minerais are then collected by separating them from the froth.Chemical reagents known as “collectors” are commonly added to the slurry to increase thesèlectivity and efficiency of the séparation process, see U.S. Patent No. 4,584,097, which ishereby incorporated herein by reference.

[0003] Froth flotation is especially useful for separating finely ground valuable 20 minerais from their associated gangue or for separating valuable minerais from one another.Because of the large scale on which mining operations are typically conducted and the largedifférence in value between the desired minerai and the associated gangue, even relativelysmall increases in séparation efficiency provide substantiel gains in productivity.

Summary of the Invention 25 [0004] Unexpectedly, it has now been found that N-butoxycarbonyl-O- alkylthionocarbamates selected from the group consisting of N-bütoxycarbonyl-O-methylthionocarbamate, N-butoxycarbonyl-O-ethylthionocarbamate, N-butoxycarbonyl-O- 2 012943 propylthiononocarbamate, N-butoxycarbonyl-O-butylthionocafbamate, N-butoxycafbonyl-O-pentylthionocarbamate, and N-butoxycarbonyl-O-hexylthionocarbamate are particularlyeffective in froth fiotation processes. A preferred embodiment provides a froth dotationprocess for benefïciating an ore, comprising: forming a slurry comprising water and particlesof an ore, the ore containing snlfîde minerais; intermixing the sluiry with effective amountsof a frothing agent and a collector to fonn a froth containing beneficiated sulfïde minerais;and collecting the beneficiated sulfide minerais; the collector comprising an N-butoxycarhonyl-O-alkylthionocarbamate selected from the group consisting of N-butoxycarbonyl-O-methylthionocarbamate, N-butoxycarbonyl-O-ethylthionocarbamate, N-butoxycarbonyl-O-propylthiononocarbamate, N-butoxycarbonyl-O-butylthionocarbamate, N-butoxycarbonyl-O-pentylthionocarbamate, andN-butoxycarbonyl-O-hexylthionocarbamate.

[0005] These and other embodiments are described in greater detail beîow.

Detailed Description of the Preferred Embodiments[0006] In preferred embodiments, sulfide métal and minerai values are recovered by froth fiotation methods in the presence of a collector, the collector comprising at least oneN-butoxycarbonyl-O-alkyîthionocarbamate selected from the group. consisting of N-butoxycarbonyl-O-methylthionocarbamate, N-butoxycarbonyl-O-ethylthionocarbamate, N-butoxycarbonyl-O-propylihiononocarb amate, N-butoxycarbonyl-O-butylthionocarbamate, N-butoxycarbonyl-O-pentyîthionocarbamate, and N-butoxycarbonyî-O-hexylthionocarbamate.The tenu “N-butoxycarbonyl-O-alkylthionocarbamate” is used herein to refer to thecompounds in the aforementioned group, including isomers thereof. For example, N-iso-butoxycarbonyl-O-isobutyîthionocarbamate is an example of a preferred N-butoxycarbonyl-O-butylthionocarbamate. Other examples of preferred N-butoxycarbonyl-O-alkyl-thionocarbamates include N-isobutoxycarbonyl-O-ethylthionocarbamate, N-isobutoxy-carbonyl-O-hexylthionocarbamate, and N-butoxycarbonyl-O-isobutylthionocarbamate.Preferably, N-butoxycarbonyl-O-alkylthionocarbamates are employed as sulfide collectors ina froth fiotation process that provides enhanced beneficiation of sulfide minerai values frombase métal sulfide ores over a wide range of pH values, and more preferably under, neutral,slightly alkaline and highly alkaline conditions. 3 012943 [0007] N-butoxycarbonyl-O-alkylthionocarbamates may be produced in varionsways. For example, butyl chloroformate may be reacted with a thiocyanate sali, e.g., sodiumthiocyanate, to form a butoxycarbonyl isothiocyanate intexmediate. Thiocyanate salts andbutyl chloroformate may be obtained from commercial sources; butyl chloroformate may alsobe synthesized by reacting phosgene with butanol. The butoxycarbonyl isothiocyanateintermediate may be reacted with an alcohol ROH to form.the desired N-butoxycarbonyl-O-alkylthionocarbamate. The R group in ROH represents an alkyl group having from one to sixcarbon atoms. Examples of ROH include methanol, éthanol, propanol, isopropanol, n- : butanol, isobutanol, n-pentanol, isopentanoï, n-hexanol and isohexanol.

[0008] Those skilled in the art understand that the tenus “beneficiate”, - “beneficiation”, and “beneficiated” refer to an ore enrichment process in which theconcentration of the desired minerai and/or meta] in the ore increases as the process proceeds.For example, a preferred froth flotation process comprises fonning a slurry comprising waterand partiel es of an ore, intermixing the slurry with a frothing agent and a collecter to form a froth containing benefreiated minerais, and collecting the beneficiated minerais.

[0009] The ore particîes in the slurry are preferably made by size-reducing the oreto provide ore particîes of flotation size, in a manner generally known to those skilled in theart. The particle size to which a particular ore is size-reduced in order to liberate minerai.values from associated gangue or non-values, Le., libération size, typically varies from ore toore and may dépend on a number of factors, e.g., the geometry of the minerai deposits withinthe ore, e.g., striations, agglomération, comatrices, etc. A détermination that particîes hâves : been size-reduced to libération size may be made by microscopie examination using methods.. -known to those skilled in the art. Generally, and without limitation, suitabïe partie] e.sizes .yvaiy from about .50 mesh to about 400 mesh. 'Preferably, the ore is size-reduced to provideflotation sized particîes in the range of about +65 mesh to about -200 mesh. Especiallypreferably for use in the présent method are hase métal sulflde ores which hâve been size-reduced to provide from about 14% to about 30% by weight of particîes of + 100 mesh and... from about 45% to about 75% by weight of particîes of -200 mesh sizes. Size réduction of . -the ore may be performed in accordance with any method known to those skilled in this art. 4 012943

For example, the ore can be crushed to -10 mesh size followed by wet grinding in a Steel bail mill to the desired mesh size, or pebble milling may be used.

[0010] The sluny (also known as a pulp or pulp slurry) may be formed in varions ways known to those skilled in the art, e.g., by intermixing liberation-sized ore parti clés with 05 water, by grinding the ore in the presence of water, etc. The pH of the sluny may be adjustedat any stage, e.g., by adding a pH modifier (acid or base) to the sluny or to the grind duringsize réduction, to provide the sluny with any desired pH. Preferred pH modifiers includesulfuric acid and lime. Thus, for example, good bénéficiât!on may be obtained at pulp slurrypH vaines in the range of about 7 to about 12, and particulariy in the pH range of from about 10 9 to about 11.5. The pH of the sluny may be adjusted at any point in the process of preparing the ore for froth flotation or in the froth flotation process itself. The aqueous slurry of oreparti clés preferably contains from about 10% to about 60% pulp solids, more preferablyabout 25% to about 50% pulp solids, most preferably from about 30% to about 40% pulpsolids, by weight based on total slurry weight 15 [0011] In accordance with a preferred embodiment, the flotation of copper, zinc and lead snlfides is perfoxmed at a pH .in the range of about 6 to about 12, more preferablyabout 9 to about 11.5. Jt has been discovered that the N-butoxycarbonyl-O-alkylthionocarbamate collectors provide exceptionally good collector strength, together withexcellent collector selectivity, even at reduced collector dosages, when froth flotation is 20 . conducted in the aforementioned pH range. .. [0012] - The sluny is preferably conditioned by intermixing it with effective amounts of a frothing agent and a collector comprising at least one N-bntoxycarhonyl-O-alkylthionocarbamate to form a froth containing beneficiated sulfide minerais. The frothingagent, collector and slurry may be intermixed in any order. For example, the collector may be 25 added to the sluny and/or to the grind in accordance with conventional methods. By"effective amonnt" is meant any.amount of the respective components which provides adesired level ofbeneficiation of the desired métal values.

[0013] An)' frothing agent known to those skilled in the art may be employed inthe froth flotation process. Non-limiting examples of snitable frothing agents include: 30 straight or branched chain low molecular weight hydrocarbon alcohols, such as Cs to Cg 5 012943 aîkanols, 2-ethyl hexanol and 4-methyl-2-pentanol (also known as methyî isobutyl carbiuol orMIBC), as well as pine oils, cresylic acid, glycols, and polyglycols. Mixtures of frothingagents may be used. Effective amounts of rrothmg agents for a particular froth flotationprocess may be determined by routine expérimentation. Typical amounts of frothing agentare often in the range of from about 0.01 to about 0.2 pound of frotlung agent per ton of oretreated, although higher or lower amounts of frothing agent may be effective in particularsituations.

[0014] The N-butoxycarbonyl-O-alkylthionocarbamate collector may be usedalone, in combination with one another, and/or in combination with other sulfide minera]collectors such as xanthates, xanthogen formates, thiophosphates, thioureas, and/ortbionocarbamates, e.g., dialkylthionocarbamates. A collector comprising an N-butoxycarbonyl-O-alkylthionocarbamate is preferably intermixed with the frothing agent andpulp slurry in amounts ranging from about 0.005 to about 5 pounds of collector per ton of orein the slurry, more preferably about 0.1 3b. to about 2 Ibs./ton, same basis. ïn froth flotationprocesses in which it is désirable to selectively collect copper sulfide minerais and selectivelyreject iron sulfide minerais such as pyrite and pyrrhotite, as well as other gangue sulfides, thecollector is preferably used in amounts of from about 0.01 îb./ton to about 5 Ibs./ton of ore inthe slurry. In bulk sulfide froth flotation processes, higher levels of collector are oftenpreferred. Effective amounts of collector for a particular froth flotation process may be . determined hy routine expérimentation. , [0015] The intermixing of the slurry with an effective amounî of a frothing agentand an effective amount of a N-butoxycarbonyl-O-alkylthionocarbamate is preferablyçonducted in a manner that produces a froth containing. beneficiated sulfide minerais.Formation of the froth .may b e. facilitated by utilizing suitably vigorous mixing conditions.and/or injecting air into the slurry. Routine expérimentation in accordance with conventionalfroth flotation methods may be utilized to détermine suitable conditions to float the desiredsulfide minerai values in the froth concentrate and, preferably, selectively reject or depresspyrite and other gangue sulfides.

[0016] . The N-butoxycarbonyl-O-alkylthionocarbamates, although virtually water- insoluble, hâve the distinct advantage of being easily dispersibîe. For example, when added 6 012943 to a flotation cell, these collectors provide higher copper recoveiy in the fîrst dotation stage together with improved copper recovexy overall, indicating improved kinetics of flotation, as shown in the examples provided below.

[0017] The N-butoxycarbonyl-O-alkylthionocaibamate collectors may be used toselectively concentrate or collect certain métal value suif des, particularly those of copper,lead and zinc from other gangue sulfides, e;g., pyrite and pyrrhotite, and other ganguematerials, e.g., silicates, carbonates, etc. These collectors may also be used in situations inwinch it is désirable to collect ail ofthe sulfides in an ore, including sphalerite (ZnS) and theiron sulfides, i.e., pyrite and pyrrhotite, in addition to the copper sulfide minerais.

[0018] , It will be appreciated by those skilled in the art that various omissions, 1 additions and modifications may be made to the processes described above without departingfrom the scope of the invention, and ail such modifications and changes are intended to fallwithin the scope of the invention, as defined by the appended daims. EXAMPLES 1-6 .. [0019] A copper ore from South America is used in the following flotation tests.This ore contains about 1.2 % copper, 4% iron and 278 ppm molybdenum. This ore alsocontains the usual silicate or siliceous type gangue.

[0020] . The ore is grourid to 75%passing a 100 Tyler mesh (150 pm) screen usinga mild Steel rod mill containing 7.5 kg of mild steel rods. The grind solids are 66% in water.Lime is added to the rod mill in a sufficient amount so as to provide a flotation pH of 11,•sinlilar to that used in the concentrator. Diesel fuel (10 grams per ton of ore in the pulp) isalso added to the mill to promote Mo flotation. The ore pulp is then discharged into aflotation cell and the pulp volume adjusted to 30-34% solids for flotation.

[0021] A Denver D-l 2 flotation machine set at 1000 rpm is used for the flotationtests. - The pulp is àgitated to ensure homogeneity. A collecter as shown in Table 1 andfrother are then added to the pulp and allowed to condition for 2 minutes. The frother used isa blended product containing AEROFROTB® 76A Frother, available commercially fromCytec'Industries, Inc., West Paterson, New Jersey. The dosage of the frother is 15 grams perton of ore in the pulp (g/t) for ail of the tests. 7 012943 [0022] Fîotation concentrâtes are collected at 1·, 3 and 6 minute intervals. Theconcentrâtes and tails are filtered, dried and assayed for Cu, Fe and Mo. The results shov/n inTable 1 clearly show the superiority of the N-butoxycarbonyl-O-alkylthionocarhamatecollectors over prior collectors, which either yield low recovery or poor selectivity against 05 iron (high Fe recovery). Because of the large scale on which mining operations are typicallyconducted and thè large différence in value between the desired minera] ' and the associatedgangue, these increases in séparation efSciency provide substantial gains in productivité7. TABLE 1

No. Collector Dose. g/t % Cu Rec. % CuGrade % FeRec. % MoRec. 1 C N-Ethoxycarbonyl-O- isobutylthionocarbamate 10 88.6 8.7 26.7 75.8 2 N -Ïsobutoxycarbonyî-O- isobutylthionocarbamate 10 89.2 8.0 .28.2 - ' 3 N-Isobutoxycarbonyl-O- ethylthionocarbamate 10 88.8 9.6 27.3 - 4 N-Isobutoxycarbonyl-O- hexylthionocarbamate 10 90.1 , . 9.9 24.5 76.6 EXAMPLES 5-10 [0023] A copper/molÿbdenum ore from South America is used in the followingfîotation tests. This ore contains about 1.4 % copper, 5.S ;% iron and 113 ppm molybdenum.This ore also contains the usual silicate or siliceous type gangue.

[0024] The ore is gronnd to 80% passing a 65 Tyler mesh (212 μηα) screen using amild Steel rod mill eontaining 7.5 kg of mild Steel rods. The grind solids are 66% in water.Lime is added to the rod mill in a sufficient amount so as to provide a fîotation pH of 10 -10.5, similar to that used in the concentrator. A collector at the dosage shown in Table 2 anda ffother (9 g/t) are added to the mill along with diesel fuel (6 g/t to promote Mo fîotation).The frother used is AEROFROTH® 70 Frother, a methyl isobutyl carbinol product available 8 012943 commercial]/ from Cytec Industries, Inc., West Paterson, New Jersey. The erre pulp is then discharged into a flotation cell and the pulp volume adjusted to 30-34% solids forflotation.

[0025] A Denver D-12 flotation machine set at 1000 ipm is used for theseHotation tests. The pulp is agitated to ensurc homogeneity. Additional frother (S g/t) is thenadded to the pulp and allowed to condition for 2 minutes. Flotation concentrâtes arecollected at 1, 3 and 6 minute intervaîs. The concentrâtes .and tails are filtered, dried andassayed for Cu, Fe and Mo. The results shown in Table 2 clearly show the superiority of theN-butoxycarbonyl-O-alkylthionocarbamate collectors, which produce hîgher recoveries ofcopper and molybdenum minerais as compared to prior collectors. Because of the large scaleon which mining operations are typically conducted and the large différence In value betweenthe desired minerai and the associated gangue, these increases in séparation efficiencyprovide substantial gains in productivity. TABLE 2

No. Collector Dose. g/t % CuRec. % CuGrade % FeRec. % MoRec. 5C N-Ethoxycarbonyl-O- isobutylthionocarbamate 10 68.5 12.0 16.4 40.0 6C N-Methoxycarbonyî-O- isobutylthionocarbamate 10 68.2 12.5 16.9 39.4 7 N-Butoxycarbonyl-O- isobutylthionocarbamate 10 72.6 14.3 18.9 48.1 8 N-Isobutoxycafbonyl-O- ethyl thionocarbamate 10 72.4 13.7 19.6 50.4 9 N-Isobutoxÿcarbonyl-O- isobutylthionocarbamate 10 73.1 12.1 20.1 50.2 .10 N-Isôbutoxycafbonyl-O- hexylthi onocarbamate 10 74.1 13.9 18.4 62.3 EXAMPLE 11 9 012943 [0026] Synthesis of isobutoxycarbonyl isothiocyanate: 136.58 grams (1 mole) of99% isobutyl chloroformate are added to a 50% thiocyanate solution containing 81 grams (1mole) of NaSCN, 81 grains of wate- 4.36 grams of quinoline (catalyst) and 1.8 grams ofNa2CO3 (base) while maintaining a reaction température of 25-30°C with agitation. The 05 reaction is monitored for the consnmption of the chloroformate during the formation of anupper layer of isobutoxycarbonyl isothiocyanate (approximately 4 honrs). The contents of thereaction vessel are filtered to remove solid sodium chloride and the isobutoxycarbonylisothiocyanate is isolated in the foim of a layer that séparâtes ifom the aqueous layer. EXAMPLE 12

10 [0027] Synthesis of N-isobutoxycarbonyl-O-isobutylthionocarbamate: A procedure begun as described in Example 11 is continued by retuming the isolated.isobutoxycarbonyl isothiocyanate layer to the reaction vessel and adding 1.3 moles ofisobutyl alcohol. The reaction température is maintained at about 20-25°C for about 4 hours.The resulting thionocarbamate/isobutyl alcohol mixture is vacuum stripped at 23-25 inches 15 Hg and 50°C to remove water and some of the excess alcohol, followed by filtration toremove precipitated sait. About 215 grams ofthe final product is obtained in the form of amixture of about 190 grams of N-isobutoxycarbonyl-O-isobutylthionocafbamate and about25 grams isobutyl alcohol. EXAMPLE 13

20 [0028] Synthesis of N-isobutoxycarbonyl-O-hexylthionocarbamate: ' A procedure begun as described in Exampîe 11 is continued by retuming the isolatedisobutoxycarbonyl isothiocyanate layer to the réaction vesseland adding 1.3 moles of hexylâlcohoh The réaction température is maintained at about 20-25°C for about 4 hours. Theresulting thionocafbamàte/hexÿî alcohol mixture is vacuum stripped at 23-25 inches Hg and 25 50°C to remove water and some of the excess alcohol, followed by filtration to remove precipitated sait. About 215 grams of the final product is obtained in the form of a mixture ofabout 190'grams of N-isobutoxycarbonyl-O-hexylthionocarbamate and about 25 grams hexylalcohol.

Claims

10 012943 WHAT IS CLADvIED-IS:

1. A froth flotation process for beneficiating an ore, comprising: forming a sluny comprising water and particles of an ore, the ore containing sulfide minerais; 05 inteimixing said slurry with effective amounts of a frothing agent and a collecter to form a froth containing beneficiated sulfide minerais; and . collecting said beneficiated sulfide minerais; the collecter comprising an N-butoxycafbonyl-O-alkylthionocarbamateseîected from the group consisting of N-butoxycarbonyl-O-methylthionocarbamate, 10 N-butoxycafbonyl-O-ethylthionoçarbamate, N-butoxycarbonyl-O-propylthionono- carbamate, N-butoxycarbonyl-O-butylthionocarbamate. N-bntoxycarbonyl-O-pentylthionocarbamate, and N-butoxycafbonyl-O-hexylthionocafbamate.

2. The process of Claim 1 in which said collecter is intermixed with said slunyin an amount in the range of about 0.005 to about 5 îbs per ton of ore in said slurry.

3. The process of Claim 1 in which said collecter is intermixed with said slurry in an amount in the range of about 0.1 to about 2 lbs per ton of ore in said sluny.

4. The process of Claim 1 in which said slurry has a pH in the range of about 6 to about 12. . ...

5. The process of Claim 1 in which said sluny has a pH in the range of about 9 to 20 about 11.5.

6. The process of Claim 1 in which said N-butoxycarhonyl-O- alkylthionocarbamate is N-butoxycarbonyhO-ethylthionocarbamate. 7. ; The .process, of Claim 1. in which said N-butoxycarbonyl-O- alkylthionocarbamate is N-butoxycarhonyl-O-butylthionocarbamate.

8. The process of Claim 7 in which said ' N-butoxycarbonyl-O- butylthionocarbamate is , seîected ,from the group consisting of N-isobutoxycarbonyl-O-isohutylthionocarhamate and.N-hutoxycarbonyl-O-isobutylthionocarbamate.

9. The process of Claim 1 in which said N-butoxycarbonyl-O-alkylthionocarbamate is N-butoxycarbonyl-O-hexylthionocarbamate. 012943 11

10. The procsss of Claim 1 in which said ore comprises a métal selected irom thegroup consisting of coppsr, lead and zinc.

11. The process of Claim 10 in which said N-butoxycarbonyl-O-alkylthionocafbamate is selected irom the group consisting of N-isohutoxycarbonyl-O- 05 ethylthionocarbamate, N-butoxycarbonyl-O-isobutylthionocarbamate, N-isobutoxycarbonyl-O-isobutylthionocarbamate, and N-isobutoxycarbonyl-O-hexylthionocarbamate.