US2383467A - Flotation of iron ores - Google Patents

Description

iron enriched product.

Patented Aug. 28, 1945 FLOTATION OF IRON ORES Julius Bruce Clemmer Tuscaloosa, of America, the Interior and Ballard H. Clemmons, Ala., assignors to the United States as represented by the Secretary of No Drawing. Applicatlon January 22, 1943, Serial No. 473,162

19 Claims.

(Granted under the act of amended April 30, 1928;

This invention described herein may be manufactured and used by or for the Government 1 for governmental purposes, without the payment to us of any royalty thereon.

This invention relates to an improved process for the concentration of iron ores whereby froth flotation of the siliceous gangue constituents yields an iron enriched product; more particularly it relates to a froth flotation process for siliceous gangue constituents in iron ores, employing anionic reagents.

An object of the invention is the development of an improved flotation process for the concentration of natural oxides of iron from pulps con taining them in the presence of siliceous gangue. A'further object is to provide a flotation process for separating silica from iron oxides employing anionic reagents. A still further object is to provide a flotation process for concentrating iron ores or products containing both calcareous and siliceous materials. Still other objects include the development of a flotation process which will have greater selectivity in separating siliceous materials from iron ores and thereby effect greater economies. Other objects, purposes, and advantages of the invention will hereinafter more fully appear or will be understood from the detailed description of its practice.

We are aware that various methods have been proposed for the concentration of iron ores by flotation methods for the purpose of rejecting siliceous gangue constituents and recovering an The most common method known to the art for concentrating iron ores has been to float the iron oxides from the siliceous gangue constituentsemploying an anionic col lector, such as oleic acid or sodium oleate, in conjunction with auxiliary reagents, as soda ash or sodium silicate, to retard flotation of the silica. Those skilled in the art recognize that the method has limitations. The method yields good results on some iron ores, but is not applicable to others. Desliming of the, ore pulps is generally necessary before good flotation of the granular oxides can be effected, and the pulps must be relatively free of'soluble salts. The salts, such as lime or magnesia, derived from the ore or present in the water employed, activate the siliceous mineral to flotation with the soap collectors and results in poor selectivity. Soft water relatively free of lime.

v ham district, Alabama.

iron oxides which would be lost March 3, 1883, as 37-0 0. G. 757) and. magnesia is generally required for satisfactory iron oxide flotation.

'An alternative method for concentrating iron ores by flotation has been to reverse'the separation and float the siliceous gangue minerals from the iron oxides by employing cationic collectors. The application of such reagents to iron ores has been described by Kirby and Gillson in United States Patents Nos. 2,217,684 and 2,221,485. This method is attractive in that iron ores in general contain less siliceous material than iron oxides, and flotation of the silica is in keeping with the preference of floating that constituent which occurs in least amount. Cationic reagents are not without their limitations, being, in general, more expensive than those of the anionic type. The cationic collectors, moreover, are not particularly selective, nor are they effective silica collectors in the presence of slime iron. Desliming of the iron ore pulps is usually necessary before acceptable flotation of silica can be achieved with cationic collectors. On many iron ores desliming results in a serious loss of iron. The iron oxides are relatively soft and friable as compared to siliceous gangue constituents, and grinding the silica to flotation size unavoidably slimes much of the if desliming were practiced.

The lack of a suitable flotation method for concentrating iron ores has long been apparent to those engaged in the art. The customary flotation methods, previously discussed, have many limitations and are not applicabie to all iron ores. These methods give poorest results on those ore or products most in need of concentration, that is, fines resulting from treatment of iron ores by other methods of concentration. A satisfactor; flotation method for recovery of the fine iron oxides and rejection of the silica would be of ma terial aid for the concentration of those iron ores which slime readily on grinding or require fine grinding for liberation.

The need of a feasible flotation method for iron ores was particularlyapparent in the concentration of the'red iron ores' of the Birming- These ores consist essentially of hematite associated with quartz and calcite, with minor amounts of other siliceous and calcareous materials including ferruginous clay. The red ores require relatively fine grinding for and calcareous materials.

the liberation of the hematite, and the hematite is soft and slimes readily. Wet concentration methods, such as hydraulic classification and tabling of the red iron ores, enables recovery of the coarse hematite in a product of acceptacle silica content. The fines resulting from such treatment are contaminated with too much silica and require processing by other methods such as flotation, to reject the silica and recover an acccptable iron product.

A satisfactory flotation method for the recovery of hematite and rejection of the silicain the red iron ores or concentrator lines was sought. Flotation of the iron oxides from the silica with anionic collectors, and flotation of the silica from the iron oxides with cationic collectors failed to give the desired results. Much of the silica floated with the hematite when using anionic collectors and gave low grade iron concentrates. The silica, predominantly quartz, was apparently activated to anionic flotation due to the presence of lime salts in the ore. Attempts to deactivate the silica and prevent its flotation with the hematite were not successful. Reversing the separation and floating the silica from the iron oxides with cationic collectors was not encouraging. The contaminated silica was reluctant to float with cationic collectors and much remained in the iron product. Neither of the methods customarily employed on iron ores was satisfactory, and other means of perfecting the separation was sought.

By extended research and experimentation, we discovered that we could make use of the acticated condition of the silica and effect its flotation from the hematite and calcite with anionic collectors while retarding flotation of the hematite with a metaphosphate in a strongly alkaline pulp. A moderate amount of meta-, hexameta-, or polyphosphate is effective in retarding flotation of iron oxides and calcareous materials when used in pulps made strongly alkaline with sodium or potassium hydroxides, or their equivalents.

or'es of the Birmingham district containing calcareous as well as siliceous gangue materials. A variety of ores and mill products from the district have responded readily to the method.

The calcareous materials, largely calcite, may be floated with the silica or retarded with the hematite by choice of the amount of metaphosphate employed.

A prime requisite in our method of flotation of silica from iron ore is that the pulp be dispersed. The metaphosphates in the strongly alkaline pulps are effective slime dispersants as well as selective depressants for the iron oxides Supplementary reagents such as sodium silicate, dextrin, starch, various tannins, or ortho or pyrophosphates may be used as dispersants in conjunction with reduced amounts of metaphosphate. The pyrophosphates, when flotation of the calcareous materials is-sought, are particularly advantageous.

in conjunction with metaphosphate. These rehave been used on various tite and must be used in conjunction with a metaor polyphosphate.

The discussion heretofore relates to the flotation of silica from iron ores in which the silica was naturally activated to anionic flotation due to the presence of soluble salts. The highly siliceous and weathered iron ores of the Birmingham district are relatively free of soluble salts and the silica is non-activated. On such ores the silica requires prior activation before acceptable flotation can be achieved by our method Extended research on a variety of siliceous iron ores from both the Alabama and Lake Superior districts has demonstrated that our method lends itself well to the use of silica activating agents. Conditioning the ore pulps with a moderate amount of a metal salt selected from the group which form soluble basic or complex salts in strongly caustic pulps in the presence of metaphosphate, activates flotation by the fatty acid or soap collectors without adversely effecting subsequent retardation of the iron oxide. Such metal salts as calcium chloride. strontium nitrate, barium chloride, zinc sulfate, aluminum sulfate, or lead nitrate iron ores for activation of the siliceous gangue and found satisfactory. Of these lead nitrate was most effective and was preferred. Calcium chloride and slaked lime were used on many ores and'gave good results. From the standpoint of cost, slaked lime was particularly attractive. When using lime as the activator, best results w'eresecured by adding the lime to the grinding operation in an amount sumcient to give a resulting grind water with a pH of about 11. 'The ground pulp wasflocculated and settled readily. The grind water containing excess free lime was discarded and the solids repulped with fresh tap water and floated to reject the silica. Free lime is detrimental in the separation and must be avoided. Washing the pulp free of lime reduces the subsequent phosphate requirements in flotation. A moderate amount of free lime in the flotation pulp can be overcome by conditioning the pulp with soda ash to precipitate the lime as insoluble carbonate. The caustic alkalinity developed reduces the subsequent caustic requirements.

The invention will be further illustrated but is not intended to be limited by the following examples:

Example I A sample of iron ore was obtained from a mine in the Graces Gap area, near Birmingham, Alabama. The ore was typical of the district and contained hematite associated with a gangue composed predominantly of quartz andcalcite with minor amounts of accessory calcareous and siliceous materials including ferruginous clay. A head analysis gave 33.? percent Fe, 11.8 percent CaO, and 28.1 percent insoluble. The ore was stage crushed to pass 20 mesh and used as the feed for subsequent flotation procedures.

A 250-gram portion of the ore was wet ground in a one-gallon pebble mill to pass mesh using 4500 grams or flint pebbles as the grinding media and one liter of tap water. The ground charge was alkaline (pH8.6) and qualitative tests on the grind water showed presence of lime salts. The ground charge, including slime, was transferred to a small mechanical agitation flotation cell of standard design using grind water as the the silica suflicient for its "8,883,467 media. The resulting pulp for flotation contained 20 percent of solids.

Flotation of the silica from the hematite and calcite was effected by the following reagents expressed in conventional terms of pounds per 4 ton of ore: g

The pulp was conditioned with the sodium hydroxide and sodium hexametaphosphate for. 2.5 minutes prior to the addition of the talloel which served as the silica collector. The talloel was emulsified into the'pulp by conditioning an additional 1.5 minutes. .Air was then allowed 'to enter the cell and resulted in an' immediate formation of a compact, heavily mineralized froth of the siliceous material which was largely quartz. The froth was collected for a period of 5 minutes when flotation was completed. The rougher froth was twice cleaned by refloating in the same cell using tap water of moderate hardness and additional sodium hydroxide and sodium hexametaphosphate as indicated. final silicareject, conventionally referred to as concentrates but designated here as "rejects since they are the waste product,.the combined middlings', and the iron concentrates, conventionally referred to as tailings in ore dressing terminology but designated here as concentrates since they represent the economic iron product, were dried, weighed, and analyzed.

The silica reject accounting for 19.8 percent of the weight of the charge, assayed 6.3 percent Fe, 4.7 percent CaO, and 82.1 percent insoluble, and represented a rejection of 57.9 percent of the totalv insoluble in the ore. Combining the flotation middlings and iron concentrates gave a composite iron product accounting for 80.2 percent of the weight of the charge, assayed 40.5 percent Fe, 13.6 percent CaO, and 14.8 percent insoluble, and represented a recovery of 96.3 percent of the total iron in the ore.

The above mentioned test was about average" of a large number made on theore'. Grinding the ore to 65 mesh or 200 mesh in either a pebble mill or iron ball mill gave results entirely similar to those already recorded. In every case good flotation of the silica was achieved when the. pH of the pulp was maintained between and 12 by the addition of sodium hydroxide, caustic soda, lye, or similar alkalies. Ammonium hydroxide was also used in other tests but is less used as the collector for the activated quartz in the recorded test. Similar results were obtained when using oleic acid or sodium oleate. A combination of talloel and oleic acid is particularly effective.

Example 11 g A 250-gram charge 01 the Graces Gap area iron ore was ground to pass 100 mesh as in Example I. The ground charge was deslimed by sedimentation methods and the granular portion floated to reject silica. Sodium hydroxide'and sodium hexametaphosphate were used to alkalize the pulp and retard flotation of the hematite and calcite. The amounts employed were 1.0 and 0.6 pound per ton of ore, respectively, in the roughing ton in the olelc acid operation, and 1.0 and 0.12 pound per cleaning operation. Talloel and crude were used as the collectors in the 'roughing operation in amounts equivalent t 0.8

and'0.4 pound per ton respectively. An additional 0.4 pound per ton of talloel and 0.2 pound '80 The per ton oi lead nitrate were used to float a scavenger product which was subsequentlycombined with the rougher frothand double cleaned to yield the final reject. The test products were dried, weighed, and analyzed. The slime fraction accounted for 23.5 percent of the weight and contained 282 percent of the total iron in the ore. portion yielded a silica reject product assaying 6.4 percent Fe, 8.2 percent CaO, and 75.9 percent insoluble, and represented a rejection of 64.1 percent of the total insoluble in the ore. The iron concentrates assayed 47.6 percent Fe, 10L8 percent CaO, and 9.8 percent insoluble, and accounted for 47.6 percent of the total iron in the ore. Combining the flotation middlings, iron concentrates, and slime gave a composite iron product representing a-recovery of 95.5 percent of the total iron in'a product assaying 42.9 percent Fe, 12.2 percent 030, and 13.3 percent of insoluble. I

Although desliming is not necessary in our method for successful flotation of silica from iron ores, it is helpful and should be practiced whenever possible.

attractive from the cost standpoint and difliculty involved inhandling.

Sodium hexametaphosphate was used as the hematite and calcite retardants in the test. The

mono-sodium metaphosphate, or its polymeric forms may also be used. The alkali metal salts of the tetraphosphates are also effective for retardation of iron oxides in quartz flotation when used in strongly alkaline pulps. The orthoand pyro-phosphates are ineffective iron oxide depressants, but have been used as supplementary dispersants in conjunction with the meta com pounds. Talloel, an impure mixture of rosin and fatt acids obtained from paper mill black liquor,--was Example In Conditioner Rougher Caustic soda Sodium metaphosphate. Tetra sodium pyrophosphato. Crude sodium oleate. Crude oleic acid Pine oil Depression of the hematite was effected by sodium metaphosphate and tetra sodium pyrophosphate in a pulp made all saline (pH'-10.9l

Flotation of the granular and ironconcentrate gave iron, 0.5 percent CaO,

with caustic soda. Sodium oleateand oleic acid were used as the. collectors for the silica and calcite. The rougher froth was double cleaned for the final reject. Test products were dried, weighed, and assayed.

The reject product represented 50.0 percent of the weight and assayed 14.7 percent Fe, 30.5

percent CaO, and 10.7 percent insoluble. The lime and insoluble reiection were 86.1 and 53.9 percent respectively. The iron concentrates assayed 57.3 percent Fe, 2.0 percent C80, and 9.7 percent insoluble. and accounted for. an iron recovery of 4'7 .1 ercent. Combining the flotation middlings and iron concentrates gave a commits iron product representing a recovery of 78.4 per.

- cent of the total iron in a product assaying 53.4

percent Fe, 4.9 percent CaQ and 9.1 percent of insoluble. I

Example I V A siliceous red iron ore was obtained item the Graces Gap area in the Birmingham district, Alabama. A head analysis gave 42.3 percent Fe, 0.5 percent CM), and 31.3 percent insoluble. The sample differed from those previously considered in that the silica, largely as .quartz. was non.- activated.

A 250-gram representative portionof the ore was ground in a one-sallonironball mill to pass Cleaver ;Conditioner B01 8 i 1 v 2 Sodium hydrk l)xide .t .1.1 7 1.0 0.2 0.2

di exame a 0.8.- 80 um p 0.0 0.08 1.,0. g 11.2 10.6 10.6 .6

Y The silica activated by slaked lime floated heavily hiineralized froth.

rapidly in a compact,

double cleaned using tap The rough froth was water and additional reagents tor a final reject.

The floated material assayed 5.0 percent Fe, and 91.2 percent insoluble, and represented a'rejection of 51.3 percent of the total insoluble in the ore. The iron concentrates assayed 53.4 percent Fe and 13.5 percent insoluble, and accounted for a recovery of 80.7 percent of the total iron in the ore. Combining the flotation middling a composite iron product representing a recovery of 97.9 percent of the total iron in a product assaying 50.3 percent and 18.5 percent insoluble.

Similar tests in-which lead nitrate, barium chloride, calcium chloride, or copper ammonium sulfate were used as the silica activator gave equally good results. From. 0.5 to 4.0 pounds of the metal salt per ton of ore was required for complete activation of the silica. The preferred procedure when using the metal salts as activators is to condition the ore pulp. amount or alkali and. metaphesphate to. reload with the desired cent insoluble was tested by flotation.

amid the hematite and give a dispersed pulp with a pH of 10 to 12. The metal. salt was. added to the pulp and conditioned. 2-.5 to minutes :01- lowed by the addition or the collector tor flotation of the silica. Reversing the order or addition of activator and collector is permissible and may even give improved results on certain ores. A mixture of alkali, phosphate, metal salt, and collector prepared by admixing outside the cell has been used to float the silica from deslimed iron ore pulps with good results. The soluble metal soap complex served both as collector and activator for the silica.

Example V A sample of Mesabi range iron ore washer tailmas c ma-mine. 3&5 percent Fe. and 52.0 per- The silica. lar ly present as quartz, was essentially finer than 0 mesh.

A. ZMFBXam p rtio or the sample was blunged .5 minutes in a flotatio c ll with 5.00 co. or. tap water and slaked l me equivalent to 12 pounds per ton of ore. The pH of the slurry was. 11.0. Tbsslurry was withdrawn from the. cell and washed. twic with fresh tap water by decantation to reject. the excess lime salts, taking care to avoid loss of slime in the operation. The limetrcatfid slurry was repulped with fresh tap water and floated to reject the silica using the generalized procedure, described in Example I.

The reagent charge employed wa as follows:

Cleaner Conditioner Rougher Sodiumhydroside l. 2 0. 5 0. 4 Sodluml oxametaphosphate l. 0 0. 2 0. 1 0. 1 'Ialloel 1. 4 0.2 Lead nitrate 0.2 pH, of. pulp l1. 0 l0. 3 l0. 6 10.8

Good flotation or the silica was achieved. The rejects assayed: 10.3. percent Fe and 83.8 percent insoluble, and represented 90.8 percent of the insoluble in the ore. The iron concentrates assayed 61.0. percent Fe and 8 .1 percent insoluble and represent a recovery of 50.2 percent of the total iron in the ore. Flotation or the silica. increased the iron content 29.5 percent and deereasedthe insoluble content 43.9 percent. Comhim. the middlings with the iron concentrate have a composite iron product representing a recovery oil 8126. percent of the total iron in a product; assaying 58.81 percent Fe, and 10.95 percent of insoluble.

Example VI A sample of slime filter cake from a gravity concentrator in the Birmingham district; Alahams". as test d by our method to reject silica and recover an iron enriched. product. The

sample assayed 41.6. Percent. Fe, 8.8 percent CaO,

to the flotation cell and floated using the procedure described in Example I.

Flotation of the quartz was. achieved with the following reagents expressed in conventional terms of pounds per ton of solids.

d1 Cleaner on Rouglier Sodium carbonate 1.0' Sodium hydroxide 0.6 0.2 0.2 0.2 Sodium hexametaphosphetc 0.4 0.04 0.04 0.08

Sodium oieate" 2.0 Oleic acid 0.96 pH oip'ulp 11.1 10.6 10.5 10.7 10.8

The pulp was conditioned 2.5 minutes with sodium carbonate to precipitate remaining lime salts prior to floating'the activated quartz with sodium oleate and oleic acid from the strongly akaline dispersed pulp. The rougher froth was triple cleaned for the final silica reject product. The silica reject, accounting for 10.3 percent of the weight of the dry sample, assayed 6.2 percent Fe, 6.2 percent C80, and 76.4 percent insoluble, and represented a rejection of 40.6 percent of the total insoluble in the sample. The low rejection of insoluble may beuattributed to the relatively large amount of ferruginous .clay in the sample which does not float with the quartz.

The iron' concentrates assayed 47.1 percent Fe,

8.3 percent CaO, and 12.7 percent insoluble, and

accounted for 86.5 percent of the total iron pr'es-' ent in the sample. Combining the flotation middlings and iron concentrates gave a composite iron product representing a recoveryof 98.5 percent of the iron and assayed 45.7 percentFe, 9.1 percent CaO, and 12.8 percent insoluble,

Laboratory batch flotation tests on the concen-. trator filter cake were supplemented by continuous flotation tests on a pilot plant scale at the plant. The product treated was a deslimed portion of fines bled continuously from the plant circuit. The tests were successful and demon strated that our method could be used under continuous operating conditions to reject free silica from concentrator fines with only moderate loss of iron or lime. the continuous runs than in the batch flotation tests. Rapid and complete flotation of the activated silica was effected with talloel, oleic acid, or sodium oleate when used in conjunction with a moderate amount of a metaphosphate in a strongly alkaline circuit.

It will be clear from the description of our method and results obtained in practice as illustrated by the foregoing examples, that this invention is useful for preparing concentrates of is not necessary to perfect a separation. Fourthly. it provides a method for rapid and complete flotation of siliceous or calcerous materials from iron oxide in a froth which is easily controlled. Fifthly, itprovides a method for flotation or'reJec-- tion of calcareous materials in iron ores. Sixthly, it provides a method for concentration or a wide variety of iron ores and plant products. Conversely, the process may be used to recover quartz orsiliceous products of high purity, when the principal contaminants are iron oxides or calcareous materials.

With the exception of calcareous iron ores such asthose of the Birmingham district, an activator is necessary to insure flotation 01' the silica.

-We have found that the quartz in certain calcareous ores is naturally activateddue to its long contactwith lime salts present in the ore. We have also found that -while the addition of an activating substance is not necessary with such ores, a small amount of an activating substance Less reagents were required in i acceptable iron content from ores containing too little iron to be normally of technical value. The method is applicable to ores and waste products containing calcareous as well as siliceous gangue materials and is sufliciently flexible to permit rejection or recovery of the calcareous materials with the iron oxides as desired.

.'sorption of metal such as lead nitrate, barium chloride, calcium chloride or the like will often improve the results obtained. Weathered, highly siliceous ores from the Birmingham-district, some ores from the Lake Superior region and other highly siliceous ores are found which seldom contain sufllcient linsa or other soluble salts to activate the silica an activator be employed in order to float the silica in accordance with the procedure which we have described above.

Those skilled in the art will understand that there may be several explanations for the results which-we obtain, and while we do not wish to bind ourselves to any particular explanation, we postulate the ability of metal salts to activate quartz to anion flotation as being due to the adions by the quartz, and, in turn, the reaction of such metal ions with a soap or like collector to form a relatively insoluble soap coating on the quartz surface which is water repellent and air avid. This explanation would as-' sume that the purer the quartz surface the more readily the metal ions are adsorbed, and the resuits which we obtained seemed to show that this is the case. Impure or contaminated quartz surfaces are much less active in adsorbing metal ions apparently due to the fact that the surfaces are already satiated. Absolutely pure quartz surfaces are, of course, seldom, if ever, found. New surfaces can be produced bygrinding but such new surfaces become contaminated as soon as formed by the release of soluble salts. Older methods attempted for the concentration of iron ores by flotation sought to inhibit the contamination of newly formed quartz surfaces but in the case of our process this is not essential as contaminated quartz surfaces will assist rather than inhibit the operation of our process.

The anionic flotation reagent is of a class consisting of fatty acids and soaps and those which we have found most effective are oleic acid, redoil (crude oleic acid), purified and crude sodium resinate, impure rosin acids (derived from talloei from paper mill black liquors), sulfate soap (saponifled talloel) and various talloels. We prefer to use talloel as the collector in conjunction with a small amount of oleic acid to control the froth.

We wish to caution those skilled in the art that an excess of the anionic flotation reagent seems to inhibit the flotation of-the activated silica; and it is apparently desirable that only just enough @Qi 50011111 1 oleate or the like be employed on such ores it is highly. essential that an ore to. secure satisfactory flotation. We postulate this effect to be due to double coatings on the silica surfaces which are water wetted. It appears that the first coating has the polar group joined to the anchored 'metal ion in the quartz surface and the non-polar or lipophilic end of the collector molecule orientated outward. The second coating is then reversed, the two hydrocarbon or lipophilic ends being joined together and th polar end orientated to the water interface. This explanation seems logical and epparentlyflts the facts although we do not wish to be bound thereto. We wish to point out that an excess amount of soap may possibly exert a detergent action on ore formed soap coatings to thereby remove them but this explanation appears less likely than that of the reversed or double coatings.

While we have disclosed the preferred embodiments of .our invention, .it will be readily apparent to those skilled in the art that manyvariations and modifications may be made therein without departing from the spirit vof the invention.

What we claim as new and desire to protect by United States Letters Patent is:

1. A process for the beneficiation of iron ores which comprises blunging an aqueous comminuted iron ore pulp in the presence of an alkali-soluble compound of an inorganic anion combined with a polyvalent metal selected from the group consisting of alkaline earth metals and heavy metals, establishing a strongly alkaline pH of at least 10 in said ore pulp and then subjecting said alkaline, activated ore pulp to agitation with aeration in the presence of an anion-active collecting agent selected from the group consisting of fatty acids, resin acids and soaps derived from such acids, and a phosphate compound selected from the group consisting of metaphosphates and polyphosphates, whereby siliceous gangue is floated and beneficiated iron ore is depressed and recovered.

2. A process for the beneficiation of iron ores which comprises blunging an aqueous comminuted iron ore pulp in the presence of an alkali-soluble compound of an inorganic anion combined with an alkaline earth metal, establishing a strongly alkaline pH of at least 10 in said ore pulp and then subjecting said alkaline pulp to agitation with aeration in the presence of an anion-active collecting agent selected from the group consisting of fatty acids, resin acids and soaps derived from such acids, and a phosphate compound selected from the group of metaphosphates and polyphosphates, whereby siliceous gangue is floated and beneficiated iron ore is depressed and recovered.

3. A process for the beneficiation of iron ores which comprises blunging an aqueous comminuted-iron oxide ore pulp in the presence of an alkali-soluble compound of an inorganic anion combined with calcium, then removing excess soluble calcium compounds from the activated pulp and incorporatin .therein sufficient caustic alkali to establish a strongly'alkaline pH of 10 to 12, thereafter subjecting the activated, alkaline ore pulp to agitation with aeration in the presence of an anionactive collecting agent selected from the group consisting of fatty acids, resin acids and soaps derived from such acids, and an alkali-soluble phosphate compound selected from the group consisting of metaphospirates and polyphosphates, whereby siliceous gangue is floated and beneficiated, iron ore is depressed and recovered.

4. A process for the 'beneflciation of iron ores which comprises blung ngan aqueous comminuted iron oxide ore pulp in the presence of ore pulp to agitation with aeration in the presence of an anion-active collecting agent selected from the group consisting of fatty acids, resin acids and soaps derived from such acids, and an alkali-soluble phosphate compound selected from the group consisting of metaphosphates, and polyphosphates, whereby siliceous gangue is floated and beneflciated iron ore is depressed and recovered.

5. A process for the beneficiation .of iron ores which comprises blunging an aqueous comminuted iron oxide ore pulp in the presence of lead nitrate, then incorporating therein sufilcient caustic alkali to establish a strongly alkaline pH of 10 to 12, thereafter subjecting s'aid activated alkaline ore pu1p,.to agitation with aeration in the presence of an anion-active collecting agent selected from the group consisting of fatty acids,

- polyvalent metal selected from the group consisting of alkaline earth metals and heavy metals, establishing a strongly alkalin pH of at least 10 in said ore pulp, then subjecting said alkaline activated ore pulp' to agitation with aeration in the presence of an alkali metaphosphate and an anion active collecting agent selected from the group consisting of fatty acids, rosin acids, and scans derived from such acids, whereby siliceous gangue is floated and beneficiated iron ore is depressed and recovered.

'7. A process for the beneficiation of iron ores which comprises blunging an aqueous comminuted iron ore pulp in the presence of an alkali-soluble compound of an inorganic anion combined with an alkaline earth metal, establishing a strongly alkaline pH of at least 10 in said ore pulp and then subjecting said alkaline activated ore pulp to agitation with aeration in the presence of an alkali metaphosphate and an anion-active collecting agent selected from the group consisting of fatty acids, rosin acids and soaps derived from such acids, whereby siliceous gangue is floated and beneficiated iron ore is depressed and recovered.

8. A process for the beneficiation of iron ores which comprises blunging an aqueous comminuted tation with aeration in the presence of an alkali.

metaphosphate and an anion-active collecting agent selected from the group consisting of fatty acids, rosin acids and soaps derived from such acids, whereby siliceous gangue is floated and beneficiated iron ore is depressed and recovered.

' 9. A process for the beneficiation of iron ores which comprises blunging an aqueous comminuted .p llp to agitation iron oxide ore pulp in the presence of an alkalisoluble compound of an inorganic anion combined with calcium, then removing excess soluble calcium compounds from the activated pulp and incorporating therein suflicient caustic alkali to establish a strongly after subjecting the activated alkaline ore pulp to agitation with aeration in the presence of an alkali metaphosphate and an anion-active col-, lecting agent selected from the group consisting of fatty acids, rosin acids, and soaps derived from such acids, whereby siliceous gangue is floated and beneficiated iron ore is depressed and recov-' ered.

10. A process i.'or the beneficiation of iron ores iron oxide ore pulp in the presence of lime, then removing excess soluble calcium compounds from the activated pulp by washing with water and in-- corporating therein sufl'lcient caustic alkali to establish a strongly alkaline pH of to 12, thereafter subjecting t e activated alkaline ore pulp to agitation with aeration in the presence of an alkali mctapliosphate and an anion-active co1lect-' ing agent selected from the group consisting of fatty acids, rosin acids, and soaps derived from such acids, whereby and beneflciated iron ered.

11. A process for the beneficiation of iron ores which comprises blunging an aqueous comminuted iron oxide ore pulp in the presence of lead nitrate, incorporating therein suflicient caustic alkali to establish astrongly alkaline pH of 10' to 12, then subjecting the activated alkaline ore with aeration in the presence of an alkali metaphosphate and an anion-active ore is depressed and recovcollecting agent selected from the group consisting of fatty acids, rosin acids and soaps derived from such acids, whereby siliceous gangue is floated and beneflciated iron ore is depressed and recovered.

12. A process for the beneficiation of iron ores which iron oxide ore pulp in the presence of lime, then removing excess soluble calcium compounds from the a t v pulp by washing with water and incorporating therein sufllcient caustic soda to establish a strongly alkaline pH of 10 to 12, thereafter subjecting the activated alkaline ore pulp to agitation with aeration in, the presence of talloel and sodium hexametaphosphate whereby siliceous gangue is floated and beneficiated iron ore is depressed and recovered.

13, A process for the beneflciation oi iron ores alkaline pH of 10 to 12, there-- siliceous gangue is floated,

comprises blunging an aqueous comminuted which comprises blunging an aqueous commiluuted'- which comprises comminuting, to mesh in the presence of asoluble lime salt, such an orc containing also quartz and calcite, adjusting the solids content of the resulting pulp to 20 per cent, incorporating in the pulp per ton of ore about 2 pounds of sodium hydroxide, about 0.8 pound of sodium hexametaphosphate and about 0.8 pound of. talloel; agitating the resulting mixture for about four minutes to condition the pulp, agitating and aerating the conditioned pulp for about five minutes, removing a froth product con taining quartz, recovering an initial residue from the treated pulp containing iron ore of reduced quartzcontent, again agitating and aerating the quartz-containing froth product with additional quantities of the same reagents and water to further separate quartz in the froth and depress a middling residue of iron ore in the pulp, and combining said initial residue and-middling residue to yield a beneflciated iron ore of reduced silica content. p

. 14. A process for the beneficiation of an oxidized iron ore which comprises comminuting such an ore in the presence of water and lime, adjusting the alkalinity of the resulting pulp to a pH at whereby siliceous gangue is floated and removed,

and beneficiated iron ore is "depressed and recovered.

15.' A process in accordance with claim 14 wherein tolloel is employed as the anionic collecting agent.

1d. A process inaccordance with claim 14 wherein oleic acid is employed as the anionic collecting agent.

.17. A process in accordance-with claim 14 wherein a fatty acid ,soap is employed as the anionic collecting agent.

18. A process in accordance with claim 14 wherein a soluble pyrophosphate is also incorporated in the pulp, whereby calcareous gangue is floated and removed with the siliceous gangue.

19. A process in accordance with claim 14 wherein soda ash is incorporated in the prepared ore pulp to secure the desired alkalinity and precipitate excess lime salts.

JULIUS BRUCE CLEMMER. BAI-LARD H. CLEMMONS.