CA1039417B - Talc-molybdenite separation - Google Patents

Abstract

A B S T R A C T

A method of enriching the molybdenite fraction of ores and concentrates having hydrophobic silicates containing magnesium and/or aluminum, such as talc. An aqueous slurry of the ore or concentrate is conditioned with a water soluble metallic salt of a weak base and strong acid and a water soluble salt of a weak acid and subject to agitation. The condi-tioned pulp is then subject to a conventional froth flotation wherein the molybdenite fraction is floated off as a molybdenite enriched concentrate and the talc fraction and other acid-insoluble contaminates are depressed into the tailings.

Description

~q~394~L7 ~ his invention is directed to a process for separting the hydro-phobic silicates containing magnesium fraction from molybdenite bearing ores and concentrates. In particular this invention is directed to a flotation process for mol~bdenite ores and concentrates where the talc fraction is depressed and the molybdenite fraction is selectively floated awa~ there-from~
The present process consists of conditioning pulps of molybdenite bearing concentrates having hydrophobic silicates containing magnesium by agitation in the presence of a water soluble metallic salt of a weak base and a strong acid and a water soluble salt of a weak acid.
The subject process is useful in that there is sufficient depres-sion of hydrophobic silicates containing magnesium so that either a market-able grade of molybdenite concentrate is produced directly or the molybdenite concentrate is enriched so that sub~equent processing is facilitated.
The present process is practiced by preparing aqueous slurry or pulp of ground molybdenite concentrate or a molybdenite bearing ore. Gener-! . ' .
ally the concentrated ore is ground to minus 10 mesh, preferably minus 48mesh (85% minus 325 mesh). The pulp denisty varies between about 1 and about 45% solids; however~ our tests of the process indica~e that a more satisfact-ory separation is obtained as pulp density decreases.
The pulp is then conditioned with a water-soluble metallic salt of a weak base and a strong acid and a water-soluble salt of a weak acid.
Between about 1 and about 30 pounds of the metallic salt of the weak base and strong acid are used per each ton of solids. Between about 1 and about 45 pounds of the salt of the weak acid are used per ton of solids. Optimum salt concentrations are dependent upon pulp conditions and salt combinations.
Best results are usually obtained if the metallic salt of a weak base and a strong acid is added first to the pulp, agitated and then followed by the salt of a weak acid; however, satisfactory results can be obtained when the salt of a weak acid is added first, followed by the metallic salt of weak base and a strong acid, both salts are added simultaneously, or both salts are premixed and then added to the pulp.

~394~
The preferred metallic salts of a weak base and strong acids are the water-soluble sulfate, nitrate, fluoride and chloride salts of aluminum~
manganese~ zinc, chromium, iron and cadmium. It appears that the cation of these particular salts is active in the present process.
Typical salts of weak acids that can be employed in the present process include the water-soluble alkali metal (especially sodium and potas-sium), ammonium, and alkaline earth metal (especially calcium and magnesium), salts of silicic acids; carbonic acid; acids of phosphorus, including phosphoric acid, hypophosphorous acid, phosphorous acid, hypophosphoric acid and the like; the acids o-f boronj including ortho-boric acid, meta boric acid, tetraboric acid and the like, and nitrous acid and the like.
The pulp and salts are agitated for a period of from about 1 minute ; to about 60 minutes, preferably about 30 minutes. Then the pulp is subject to a conventional froth flotation for about 1 to about 30 minutes. The molyb-denite f~action~ is floated off as an enriched molybdenite concentrate. The molybdenite recovery is very high, from about 80 to about 96% and the concen~
trate is enriched by a factor of about 2 to about 3 times. The hydrophobic silicates fraction and the other acid insoluble contaminants are depressed into the tailings (from about 50 to about 85% of the acid insoluble contamin-ants, principally talc and other hydropholic silicates, are depressed into the ~ailings).
The following examples are intended to further illustrate the present invention and not intended as limitations thereof. Naturally the process conditions such as process times, temperature, pH and reagent concentration can be varied through routine experimentation to optimize the end results for a particular ore, mesh size~ pulp density, and partic~lar reagents employed.
Example 1 (no treating agent) A composite sample of low grade molybdenite concentrate produced at the Pima Mine containing approximately 18% molybdenite, 4% chalcopyrite, 5% pyrite and 69% acid insoluble minerals was made into a dilute pulp of five percent solids in water at ambient temperature in a laboratory flotation cell.

- 2 _ ~03~7 The pulp was immediately subjected to froth flotation and the froth removed for five minutes, during which a concentrate was separated. This example is given to exemplify the response of the composite sample without the treatment of subject process. The results of the example are presented in the following table.

eight Percent ~istribution %
Product Percent Mo Insol. MoInsol.
Head 100.00 10.98 68.8 100.0 100.0 Concentrate93.75 11.35 68.9 96.9 93.9 Tailing 6.25 5.47 66.7 3.1 6.1 10Example 2 A sample of the composite described in Example 1 was subjected to the pulping procedure described in Example 1. The pulp was then agitated with a quantity of zinc sulfate corresponding to four pounds per ton of solids for thirty minutes. A quantity of sodium silicate corresponding to 7.5 pounds per ton of solids was then added. The pulp was then subjected to flotation as described in Example 1. The results are presented in the following table.

~eight Percent istribution %
Product Percent Mo Insol. MoInsol.
._ _ __ _ HeadlOOnOO10.98 ~7.7 100.0 100.0 Concentrate44.69 22.53 49.7 89.0 32.8 20Tailing~r55.31 2.24 82.2 lloO 67.2 Example 3 A sample of the composite described in Example 1 was subjected to the pulping procedure described in Example 1. A quantity of sodium silicate corresponding to 7.5 pounds per ton of solids was added to the pulp. A
quantity of zinc sulfate corresponding to 16 pounds per ton of solids was then added to the pulp. The pulp was agitated for thirty minutes and then subjected to flotation as described in Example 1. The results are presented in the following table.

s ~ ; - 3 -1~339gl~7 Weight Percent istribution %
Product Percent Mo Insol. Mo Insol.
Head 100.00 10.99 67.5 100 D O 100 ~ O
Concentrate54.08 19.03 55.1 93.6 44.1 Tailing 45.92 1.53 82.2 6.4 55D9 Example 4 A sample of the composite described in Example 1 was subjected to the pulping procedure described in Example 1. A quanti,ty of 10% sodium silicate solution was placed in a beaker. To this was added a quantity of 10% zinc sulfate solutionO The contents in the beaker were then washed into the pulp. The quantity of sodium silicate corresponded to 7.5 pounds per ton of solids, the quantity of zinc sulfate corresponded to 16 pounds per ton of solids. The pulp was agitated for thirty minutes and then subjected to flotation as described in Example 1. The results are presented in the follow-ing table~

Weight Percent Distr tion %
Product Percent Mo Insol. Mo Insol.
Head 100.00 11.10 68.2 100.0 100.0 Con,centrate56.61 18.12 58.0 92.4 48~1 Tailing 43.39 1.95 81.6 7~6 51.9 Example 5 A sample of the composite described in Example 1 was subjected to the pulping procedure~ described in Example 1. The pulp was then agitated with a quantity of zinc sulfate corresponding to 16 pounds per ton of solids for thirty minutes. An addition of disodium hydrogen phosphate corresponding to 7.5 pounds per ton of solids was then added. The pulp was then subjected to flotation as described in Example 1. The results are presented in the following table.

Weight Percent Dist butio_ %
Product Percent Mo Insol. Mo Insol.
- Head 100.00 10.97 68.1 100.0 100.0 Concentrate35056 28.58 40~1 92.6 20.9 Tailing 64.4~ 1.26 83.6 7.4 79.1 103~4~7 Example 6 A sample of the composite described in Example 1 was subjected to the pulping procedure described in Example 1~ The pulp was then agitated with a quantity of zinc sulfate corresponding to 16 pounds per ton of solids for thirty minutes. An addition of sodium acid carbonate corresponding to 7,5 pounds per ton of solids was then added. The pulp was then subjected to flotation as described in Example 1. The results are presented in the follow-ing table~

Weight Percent Distribution %
Product Percent Mo Insol. Mo Insol.
Head 100.00 11.66 67.6 100.0 100.0 Concentrate33.94 32.56 35.2 9~.8 17.7 Tailing 66.06 0.92 84.2 5.2 82.3 xample 7 A sample of the composite described in Example 1 was subjected to the pulping procedure described in Example 1. A quantity of 10% sodium silicate solution was placed in a beaker. To this was added a quantity of 10% aluminum sulfate solution~ The contents in the beaker were then washed into the pulp. The quantity of sodium silicate corresponded to 7.5 pounds per ton of solids, the quantity of aluminum sulfate corresponded to six pounds per ton of solids. The pulp was then agitated for thirty minutes and then subjected to flotation as described in Example 1. The results are presented in the following tableO

Weight Percent Distribution %
Product Percent Mo Insol. M Insol.
Head 100.00 10.52 68~3 100.0 100.0 Concentrate52.50 17.59 58.0 87.8 44.6 Tailing 47.50 2.71 79.7 12.2 55.4 Example 8 A sample of the composite described in Example 1 was subjected to the pulping procedure described in Example 1. The pulp was then agitated with a quantity of aluminum sulfate corresponding to two pounds per ton of solids for five minutes. A quantity of disodium hydrogen phosphate corres-" - 5 _ ., ~

~3~7 ponding to 7~5 pounds per ton of solids was then added. The pulp was then subjected to flotation as described in Example 1. The results are presented in the following table.

Weight Percent Distribution %
Product Percent Mo Insol. Mo Insol.
Head 100.00 10.91 68.8 100.0 100.0 Concentrate 42.45 21.29 51.6 82.8 31.8 Tailing 57.55 3.26 81.5 17.2 68.2 Example 9 A sample of~,the composite described in Example 1 was subjected to the pulping procedure described in Example 1~ The pulp was then agitated with a quantity of alun~num sulfate corresponding to one pound per ton of solids for two minutes. A quantity of sodium acid carbonate corresponding to 7O5 pounds per ton of solids was then addedO The pulp was then subjected to flotation as described in Example 1. The resul~s are presented in the following table.

Weight PerGent Distribution %
Pro uct Percent Mo Insol. _ Insol.
Head 100.00 10.99 68.6 100.0 100.0 Concentrate52.51 18.82 55.6 89.9 42.6 Tailing 47.49 2.34 82.9 10.1 57.4 Example 10 A sample of the composite described in Example 1 was subjected to the pulping procedure described in Example 1. The pulp was then agitated with a quantity of chromic sulfate corresponding to four pounds per ton of solids for fi~e minutes. A quantity of sodium silicate corresponding to 705 pounds per ton of solids was then added to the pulp. The pulp was then subjected to flotation as described in Example 1. The results are presented in the following table~

Weight Percent Distribution %
Product Percent M Insol. M

Head 100.00 11.17 69~1 100.0 100~0 Concentrate34.09 29.66 41.7 90.~ 20.6 Tailing 65.91 1.62 83.3 9.6 79.4 ~,i,~3 ~039~7 Example 11 A sample of the composite described in Example 1 was subjected to the pulping procedure described in Example 1. The pulp was then agitated with a quantity of chromic sulfate corresponding to four pounds per ton of solids for five minutes. A quantity of disodium hydrogen phosphate corres-pondi~ng to 7.5 pounds per ton of solids was then added to ithe pulp. The pulp was then subjected to flotation as described in Example 1. The results are presented in the following table.

Weight Percent Distribution %
Product Percent Mo Insol. Mo Insol.
Head 100.00 11.34 69.4 100.0 100~0 Concentrate56.21 18.36 30~4 91.0 48~9 Tailing 43.79 2.32 81.0 9.0 51.1 Example 12 A sample of the composite described in Example 1 was subjected to the pulping procedure described in Example 1. The pulp was then agitated with a quantity of chromic sulfate corresponding to four pounds per ton of solids for five miuutes. A quantity of sodium acid carbonate corresponding to 7.5 pounds per ton of solids was then added to the pulp. The pulp was then subjected to flotation as described in ~xample 1. The results are pre-sented in the following table.

~ Percent Distribution %
Product Percent Mo Insol. Mo Insol.
Head 100.00 11.39 69.2 100.0 100.0 ConcentrateSl.38 20.28 56.4 91.5 41.9 Tailing ~8.62 1.99 82.8 8.5 58.1 Exa_~_e 13 The procedure of Example 2 is repeated employing a pulp density ofabout 5% solids, MnC12 (16 pounds per ton of solids) in place of ZnS04 and sodium silicate (7.5 pounds per ton of solids) with substantially the same results.

Example 14 The procedure of Example 9 is repeated with a pulp density of about .~

1~39~7 1% solids and the water-soluble calcium salts of boron (3 pounds per ton of solids) with similar resultsO
~ , .
The procedure of Example 6 is repeated with a pulp density of about 45% solids, CdF2 (30 pounds per ton of solids) and ammonium bicarbonate (45 pounds per ton of solids).
Example 16 Method of Determining Acid Insoluble Percentage in Molybdenite Containing Ore or Concentrate.
Procedure:
1. Weight 0.5 gram of molybdenum concentrate sample and transfer to a 400 ml. beaker. Add 25 ml. of concentrated nitric acid, place on hot plate and warm slightly. Add approximately 1/3 teaspoon potas-sium chlorate, place watch glasses on beakers and take to near dryness.
2. Add 10 ml~ of concentrated hydrochloric acid and again place on the hot plate and take to near dryness.

3. Add 10 ml. of concentrated hydrochloric acid again and approximately 50 ml~ of distilled water. Place on the hot plate, bring to a boil and boil for 5 - 10 minutes~

4. Remove from hot plate and filter through 15 cm. Whatman No. 40 (ashless) filter paper. Wash several times with hot distilled water.

5. Place residue in a clay annealing cup and ash in a muffle furnace.

6. Cool and weigh .
Calculation:
Wto _nsol in grams x 100 = % Acid Insol Wt.sample in grams Trade Mark .,i ~ 1~39~7 SUPPLEME~TARY mscLosu -As previously stated, the pulp density varies between about 1% and about 45% solids; however our tests of the process indicate that a more satis-factory separation is obtained as pulp density decreases, with a preferred range of about 5% to 15% solids.
The preferred metallic salts of a weak base and strong acid are the water-soluble sulfates, nitrate, fluoride and chloride salts of the cations:
aluminumg manganese, calcium, magnesium, zinc, copper, cobalt, rlickel7 chromium, iron and cadmium; these strong acids afford the anions chloride~
fluoride, nitrate and sulfate.
The weak acid hydroferrocyanic acid is useful only in the form of-\ its water-soluble metallic salt when the metal ion is zinc.
The molybdenite concentrate can be enriched, with respect to molyb-denite as compared to the head, by a factor of about 2 to about 5 times.
E~ample 17 Another sample of low grade molybdenite concentrate that contained a substantial portion of hydrophobic talc was made into a dilute pulp of approximately 5% solids in water at ambient temperature in a laboratory flota-tion cell. This pulp had a pH of 8.3~ The sample so prepared was then agitated with a quantity of zinc sulfate corresponding to six pounds per ton of solids for about 30 minutes. The pH of this admixture was measured and found to be 6.8. Thereafter, one pound per ton of solids of NaOH was mixed with the pulp so treated resulting in a pH of 7.1. Thereafter, eight pounds per ton of potassium ferrocyanide was mixed with the aforementioned pulp con-taining zinc sulfate and NaOH. The resulting admixture had a pH of 8.2. The said admixture was immediately subjected to froth flotation and the froth removed for five minutes during which a concentrate was separated with results as follows:
Percent Weight Percent Mo In Percent Mo Recovered in Concentrate Head Tail Concentrate in Concentrate 19.9 4.13 0.23 19.88 95.5 The benefits from the above processing will be appreciated by _ g _ "~o ~6~3~4:17 comparing said results with the following wherein the said pulp made up to 5%
solids was floated without the addition of our new treating reagents, i~e~, such as zinc sulfate and potassium ferrocyanide.

Percent Weight Percent Mo In Percent ~o Recovered in Concentrate Head Tail Concentrate in Concentrate 98.1 4.66 1.34 ~.73 99.4 As a result of repeating the above experiment substituting various metals for zinc, it was observed that no effective separation of talc from a molybdenite bearing concentrate was obtained.
Preferred ~ual-Agent Combinations A. (a). Water so]uble metallic salt of a weak base of which the cation is selected from the class consisting of aluminum, cadmium, chromium, cobalt, copper, iron, calcium, magnesium, manganese~ nickel and zinc, and a strong acid selected from the class consisting of hydrochloric acid, nitric acid and sulfuric acid affording the anions chloride, nitrate and sulfate, and (b). Sodium silicate or potassium silicate.
B. ~; (a). Water soluble metallic salt of a weak base of which the cation is selected from the class consisting of aluminum, chromium, copper, manganese, and æinc, and a strong acid selected from the class consisting of hydrochloric acid, nitric acid and sulfuric acid affording the anions chloride, nitrate and sulfate~ and (b)o Sodium bicarbonate, potassium bicarbonate, or ammonium bicar-bonate.
C. (a). Water soluble metallic salt of a weak base of which the cation is selected from the class consisting of aluminum, chro~ium, manganese, and zinc, and a strong acid selected from the class consisting of hydrochloric acid, nitric acid and sulfuric acid affording the anions chloride, nitrate, and sulfate, and (b). Water soluble sodium monohydrogen orthophosphate, potassium monohydrogen orthophosphate, or ammonium monohydrogen orthophosphate.

D. (a). Water soluble metallic salt of a weak base of which the ", _ 10 ~

~39~a~7 cation is selected from the class consisting of aluminum, cobalt, copper, manganese~ and zinc, and a strong acid selected from the class consisting o-f hydrochloric acid, nitric acid and sulfuric acid affording the anions chloride, nitrate and sulfate, and (b). Water soluble sodium borate, potassium borate or ammonium borate.
E. (a). Water soluble metallic salt of a weak base of which the cation is selected from the class consisting of aluminum, copper, and zinc, and a strong acid selected from the class consisting of hydrochloric acid, nitric acid and sulfuric acid affording the anion chloride~ nitrate and sulfate, and (b)D Water soluble sodium orthophosphate, potassium orthophosphate or ammonium Qrthophosphate.
F. (a). Water soluble zinc chloride~ 7inc nitrate~ or zinc sulfate~
and (b)~ Sodium carbonate, potassium carbonate, ammonium carbonate~
sodium ferrocyanide, potassium ferrocyanide or ammonium ferrocyanide.
Go (a). Water soluble zinc chloride~ ~inc nitrate~ or zinc sulfate, and (b~. Sodium silicate or potassium silicateO

~ 11 --~ . .f

Claims (25)

1. A method of preparing molybdenite bearing concentrates containing an acid insoluble fraction consisting principally of hydrophobic silicates containing magnesium which is conventionally floated or depressed with the molybdenite fraction during flotation, said method including the steps of conditioning an aqueous pulp of the molybdenite bearing ore or concentrate with a water-soluble metallic salt of a weak base and strong acid and a water-soluble salt of a weak acid; agitating said conditioned aqueous pulp, and subjecting said agitated conditioned pulp to froth flotation.

2. The method according to claim 1 including the additional steps of particulating the molybdenite bearing concentrate and adjusting the density of the aqueous pulp from about 1 to about 45% solids.

3. The method according to claim 1 wherein the aqueous pulp is first conditioned with the water-soluble metallic salt of the weak base and strong acid.

4. The method according to claim 1 wherein the aqueous pulp is condi-tioned with from about 1 to about 30 pounds per ton of pulp solids of the water-soluble metallic salt of the weak base and strong acid.

5. The method according to claim 1 wherein the water-soluble metallic salt of a weak base and strong acid is selected from the water-soluble alumi-num, manganese, zinc, chromium, iron and cadmium salts of hydrofluoric acid, hydrochloric acid, nitric acid, and sulfuric acid.

6. The method according to claim 1 wherein the water-soluble salt of a weak acid is selected from the water-soluble alkali metal, alkaline earth metal and ammonium salts of silicic acids, carbonic acid, acids of phosphorous and acids of boron.

7. The method according to claim 1 wherein the water-soluble metallic salt and a weak base and a strong acid is selected from the group consisting of zinc sulfate, aluminum sulfate and chromium sulfate.

8. The method according to claim 1 wherein the water-soluble salt of the weak acid is selected from the group consisting of sodium silicate, sodium monohydrogen orthophosphate and sodium bicarbonate.

9. The method according to claim 1 wherein the water-soluble metallic salt of the weak base and strong acid is zinc sulfate and the water-soluble salt of the weak acid is sodium silicate.

10. A method of separating ore or concentrate having molybdenite and a substantial amount of hydrophobic silicate containing magnesium by froth flotation to obtain a molybdenite enriched concentrate and hydrophobic sili-cate enriched tailings, which method includes the steps of:
(1) forming a dual agent conditioned aqueous pulp of said ore or concentrate, said dual agent consisting essentially of (I) (a) water soluble metallic salt of a weak base and a strong acid, and (b) water soluble salt of a weak acid, except when said weak acid is hydroferrocyanic acid, or (II) (a) water soluble zinc salt of a strong acid, and (b) water soluble salt of hydroferrocyanic acid;
(2) agitating said conditioned aqueous pulp; and (3) subjecting said agitated conditioned aqueous pulp to froth flotation separation whereby a molybdenite enriched concentrate is flotated and hydro-phobic silicate is selectively depressed into the tailings from said froth flotation separation.

11. The method according to claim 10 where said hydrophobic silicate is talc.

12. The method according to claim 10 where said dual agent consists essentially of:

13 (I) (a) water soluble metallic salt of a weak base of which the cation is selected from the class consisting of aluminum, cadmium, chromium, cobalt, copper, calcium, magnesium, iron, manganese, nickel and zinc, and a strong acid selected from the class consisting of hydrochloric acid, hydrofluoric acid, nitric acid, and sulfuric acid affording the anions chloride, fluoride, nitrate and sulfate, and (b) water soluble alkali metal, water soluble alkaline earth metal, or water soluble ammonium salt of weak acid selected from the class consisting of boron acids, carbonic acid, acids of phosphorus, and silicic acid; or (II) (a) water soluble zinc chloride, zinc fluoride, zinc nitrate, or zinc sulfate, and (b) water soluble alkali metal, water soluble alkaline earth metal, or water soluble ammonium salt of hydroferrocyanic acid.

13. The method according to claim 12 where said conditioning is carried out by adding said metallic salt of (I)(a) and (II)(a) to said aqueous pulp to condition said pulp prior to the addition of said salt of (I)(b) and (II)(b), as the case may be.

14. The method according to claim 12 where said aqueous pulp is treated with between about 1 and 30 pounds per ton of pulp solids of said metallic salt of (I)(a) and between about 1 and 45 pounds per ton of pulp solids of said salt of (I)(b) and (II)(b) as the case may be.

15. The method according to claim 10 where said dual agent consists essentially of (a) water soluble metallic salt of a weak base of which the cation is selected from the class consisting of aluminum, cadmium, chromium, cobalt copper, calcium, magnesium, iron, magnanese, nickel and zinc, and a strong acid selected from the class consisting of hydrochloric acid, nitric acid and sulfuric acid affording the anions chloride, nitrate and sulfate, and (b) sodium silicate or potassium silicate.

16. The method according to claim 10 where said dual agent consists essentially of (a) water soluble metallic salt of a weak base of which the cation is selected from the class consisting of aluminum, chromium, copper, manganese, and zinc, and a strong acid selected from the class consisting of hydrochloric acid, nitric acid and sulfuric acid affording the anions chloride, nitrate and sulfate, and (b) sodium bicarbonate, potassium bicarbonate, or ammonium, bicarbonate.

17. The method according to claim 10 where said dual agent consists essentially of (a) water soluble metallic salt of a weak base of which the cation is selected from the class consisting of aluminum, chromium, manganese, and zinc, and a strong acid selected from the class consisting of hydrochloric acid, nitric acid and sulfuric acid affording the anions chloride, nitrate and sulfate, and (b) water soluble sodium monohydrogen orthophosphate, or ammonium monohydrogen orthophosphate.

18. The method according to claim 10 where said dual agent consists essentially of (a) water soluble metallic salt of a weak base of which the cation is selected from the class consisting of aluminum, cobalt, copper, manganese, and zinc, and a strong acid selected from the class consisting of hydrochloric acid, nitric acid and sulfuric acid affording the anions chloride, nitrate and sulfate, and (b) water soluble sodium borate, potassium borate or ammonium borate.

19. The method according to claim 10 where said dual agent consists essentially of (a) water soluble metallic salt of a weak base of which the cation is selected from the class consisting of aluminum, copper, and zinc, and a strong acid selected from the class consisting of hydrochloric acid, nitric acid and sulfuric acid affording the anions chloride, nitrate and sulfate, and (b) water soluble sodium orthophosphate, potassium orthophosphate, or ammonium orthophosphate.

20. The method according to claim 10 where said dual agent consists essentially of (a) water soluble zinc chloride, zinc nitrate or zinc sulfate, and (b) sodium carbonate, potassium carbonate, ammonium carbonate, sodium ferrocyanide, potassium ferro-cyanide or ammonium ferrocyanide.

21. The method according to claim 10 where said dual agent consists essentially of (a) water soluble zinc chloride, zinc nitrate, or zinc sulfate, and (b) sodium silicate or potassium silicate.

22. A method of separating molybdenite concentrate containing molyb-denite as the major metal value, talc and other acid insoluble minerals, which method consists essentially of:
(1) forming an aqueous pulp of said concentrate;
(2) conditioning said aqueous pulp with zinc sulfate;
(3) adding to said conditioned pulp potassium ferrocyanide;
(4) agitating said conditioned aqueous pulp; and (5) subjecting said agitated conditioned pulp to froth flotation separation whereby a molybdenite enriched concentrate is floated and talc is selectively depressed into the tailings from said froth flotation separation.

23. The method according to claim 22 wherein said zinc sulfate is added in an amount of about 6 pounds per ton of solids and said ferrocyanide is added in an amount of about 8 pounds per ton of solids.

24. A method of separating ore or concentrate having molybdenite and a substantial amount of hydrophobic silicate containing magnesium by froth flotation to obtain a molybdenite enriched concentrate and hydrophobic silicate enriched tailings, which method consists essentially of:
(1) forming a dual agent treated aqueous pulp of said ore or concentrate, said dual agent consisting essentially of (I) (a) water soluble metallic salt of a weak base and a strong acid, and (b) water soluble salt of a weak acid selected from the group consisting of boron acids, carbonic acids, acids of phosphorous and silicic acids; or (II) (a) water soluble zinc salts of a strong acid, and (b) water soluble salt of hydroferrocyanic acid, and (2) subjecting said dual agent treated aqueous pulp to froth flotation separation whereby a molybdenite enriched concentrate is floated and hydro-phobic silicate is selectively depressed into the tailings from said froth flotation separation.

25. A method of separating ore or concentrate having molybdenite and a substantial amount of a hydrophobic silicate talc containing magnesium by froth flotation to obtain a molybdenite enriched concentrate and hydrophobic silicate talc enriched tailings, which method consists essentially of:
(1) forming a dual agent treated aqueous pulp of said ore or concentrate, where the treating agent consists essentially of aluminum sulfate and sodium silicate, and (2) subjecting said dual treated aqueous pulp to froth flotation separation whereby a molybdenite enriched concentrate is floated and hydro-phobic silicate talc is selectively depressed into the tailings from said froth flotation separation.