US2106887A - Method of treating ores - Google Patents

Description

Patented Feb. 1, 1938 mz'rnon or raria'rnm onus Theodore Earle, Pacific Palisades, Calif.

No. Drawing.s

Application June 30, 1936, erial N0. 88,147

This invention is a continuation in part and a development of my invention as disclosed in my application for Letters Patent of the United States, Serial Number 685,743, and has to do with the field of froth flotation separation and selective concentration of ores, minerals and other inorganic compounds, and more particularly with the preliminary preparation of materials to be later flotatively separated, and has as an object to provide a novel and improved technique giving effect to hitherto unknown discoveries wheretlirough separations and concentrations heretofore considered impossible through flotation methods may be efllciently accomplished, and wherethrough finer separations, cleaner concentrates and higher recoveries may be more efficiently and more economically had in the generally known fleld of froth flotation separation.

Standard froth flotation methods at present commercially employed are highly successful when applied to materials characterized by strong adsorptive power in respect to the applied flotation reagents, in which class may be included most of the metals and metallic sulphides. However, such methods are at best but moderately eflicient when applied to the flotation of the metallic oxides and quite ineficient when utilized in attempts to float the silicates and non-metallic oxides.

The hereinafter described improved method will efliciently float the silicates and non-metallic oxides, improve the recoveries now possible through flotation of the metallic oxides and even enhance the recoveries now had through flotation of the metals and sulphides. In the last cited case, both oxidized and unoxidized particles of the material soughtto be floated do not always respond to conventional methods and are lost to the recovery, when, through application of the improved method, such particles can be made to float easily and readily.

In the field of the true metallic oxides such minerals as azurite (2CuCOa.Cl1(OH)a), malachite (CuCO3C11(OH)2) and wulfenite (PbMnOr) are rather easily treated by standard flotation methods with rather low grade recoveries and concentrates, but when treated by the improved method herebelow described all of these minerals were efllciently floated with high recoveries. Among other oxide minerals successfully and inexpensively floated with the improved technique may be listed Cuprite (CuaO) v Chrysocolla (CuSlOa.2H:O)

Zincite (ZnO) Smithsonite (ZnCOa) Franklinite ((F'e, Mn, Zn) 0(EeMn) 0;) Anglesite (PbSOQ Leadmolybdates Lead vanadates Hematite (FezOa) Magnetite (FeaOr) Limonite (2FezOa,3HaO) Scheelite (CaWOr) Placer gold where the gold is found in grains of specular hematite. Ferberite The manganese oxide ores Cassiterire (SnOz) Bauxite (aluminum oxide) Chromite (FeQCrzOz) Carnotite (Va and U oxide) Brass from bronze filings Brass from iron filings Witherite from bauxite, Ochre A few of the above metallic oxides are at present being treated by flotation with but indifierent success. For instance, a manganese oxide ore is being floated in Cuba through a very delicate process and with but a fair recovery. On the other hand, the improved method applied to a closely similar ore produced a 95% recovery and a concentrate showing 56% manganese.

Considering the true silicates and the metallic oxides it is found that many such can not be commercially separated or floated at all with conventional methods, and the others only in efficiently through the use of expensive reagents to activate the particle surfaces, while the improved method has been applied to the successful, eflicient and inexpensive flotation of the following: I

Silica sand and quartz of minus 16 mesh The feldspar-s in coarse and fine sizes (K, Ca or Na aluminum silicates) Beryl (Be3A12(SiOa) e) The mlcas (K and Mg aluminum silicates) Garnet (Ca, Mg, Fe or Mn aluminum silicates) Cryolite (NaaAlFc) Lepidolite (lithia aluminum silicate) Crystalline limestone from amorphous limestone Monazite (Ce, La, Di)P04) Emery (FezOa and A1203) Kaolin (hydrous silicate of aluminum) Clay (hydrous silicate of aluminum).

vermiculite either crude or" roasted mica).

Since the technique -wherethrough the improved method is made effective is concerned (ace with adsorptive (:haracteristics. of the materialv tobefioatedand withnicetiesofwaterregulation, for both of which an adequately specific terminology is not available, certain terms and phrases to be employed in the elaboration of the improved method herebelow are herein specifically defined for limitation to that particular meaning readable therein throughout this exposition and the included claims.

Aflinttg as used herein means surface attraction and adhesion between a mineral particle and water, only; in other words, the adsorptive effect of the mineral as evidenced in respect to water, and not in respect to any other chemical reagent.

'Afllnttioe capacity designates the amount of water or thickness of water film held to a mineral particle against removal therefrom by a particle of relatively lower ailinitive power.

Amnity value is the measure of the afilnitive capacity of a mineral particle.

Afllnitivc power is the measure of the effective ailinity or aillnltive force of a mineral particle.

Adsorptioaasusedhereinislimitedtothesurface attraction and adhesion between-a mineral particle and a chemical reagent other than and from water.

Adsorptive'pow is used to designate the force with which chemical reagents are attracted to and held on the surfaceof a mineral particle; this force varies with the nature of the mineral particle and will vary for a given particle in respect to difierent reagents.

Adsorptice capacity refers to the amount of reagent or thickness of reagent film held to aminerai particle against removal therefrom by a particle of relativdylower adsorptive power.

Adsorptioe eflect denotes the practical result obtained in respect to concentration of reagent on and about a mineral particle through exercise of the adsorptive power of such particle.

Adsorptine. difle'rential designates the difference between adsorptive capacities of mineral particles in respect to the same reagent.

I'lotatioely modify is used to describe the action resulting in change in surface characteristics of a mineral particle through afiinity or adsorption talii'ecting the behavior of such particle in a flotaon cell.

Flotctinelg increase dacribes such modifying action as rsults in or enhances the relative flotability of the particle so modified.

i'lototively prevent describes such modifying action as destroys or decreases the relative fiotability of the particle so modified.

Free water refers to the moisture or water' content of the ore or mineral other than the water of chemical combination of such ore or mineral and includes both adsorbed and absorbed water and interstitial water. Free water includes all water that can be drained, filtered or evaporated at temperatures below 212 degrees F. from an ore or mineral.

Variable-film water is herein limited to a designatlon of the amount of water adsorbed to the exterior surfaces of the ore and mineral particles and held to these surfaces by the afiinity of the particles. 1

Dry for purposes of this exposition defines a condition of ore or mineral wherein all variablefilm water has becneliminated. This condition can beobtained only through evaporation of the water at temperatures considerably above atmospheric and can be maintained only through I amass? from Just above the dry condition as a lower limit to an upper limit determined by that amount of water which will satisfy the aflinitive needs of all the material particles, The total amount of water to satisfy these afiinitive needs will vary with the degree of comminution and specific gravity of the material; the finer grinding requiring the larger amounts of water because of the larger surface areas to be covered. For material ground to pass 16 mesh and with few-fines the upper limit of variable film water may be as low as y. of 1% or it may approach 3%; if the material is ground to pass a 100 mesh screen the upper limit of variable film water will approach 8% by weight of the material. In no case will the afiinitive needs of the material treated by this method be larger than 8% by weight. Material in a moist condition will not contain interstitial water but it may have water; absorbed within-the interiors' of the various particles in addition to Moisture, as herein used, has the same limi- I tations of meanng as are above employed in respect to moist.

Wet refers to a condition of ore or mineral where there is suillcient free water to give an excess over that needed to satisfy the aflinitive needs of the ore particles. An ore which has been allowed to drain naturally (without evaporation) over long periods of time is still in the wet condition. 4

Excessively wet defines that condition where the amount of free water in an ore or mineral is such as to substantially suspend the ore particles in the water when agitated. Except in the case of very fine comminution of the material, any

mix containing over 25% by weight of water would be termed ekcessivelyiwet.

Film as used herein refers to that quantity of liquid, either water or reagent, adsorptively'held tothe surfaces of ore or mineral particles. The film adsorbable to a given mineral particle will vary in thickness in aocordyith'the adsorptive capacity of such mineral in respect to the specific liquid concerned and in any given instance will be the resultant of two variables,,

namely, the adsorptive or ailinitive capacity of the mineral and the character of the liquid, assuming an adequate supply of the liquid.

Active reagent designates herein a reagent capable of fiotativemodification of a mineral surface. As examples under this heading may be grouped the fatty acids and their derivatives, soaps, xanthates, aerofiot, sodium sulphide, copper sulphate, water, cyanide, etc., etc.

Inactive reagent is employed herein to designate a reagent incapable of fiotatively modifying mineral surfaces and employed to satisfy physical qualitia of the mineral, such as absorption,

and to serve as solvents for the active reagents. Kerosene, crude oil and castor oil are examples of inactive reagents.

' Insulate is herein used to denote the action of variable-film water adherent to a mineral particle oughly wet or excessively wet mixture wherein the presence of interstitial water insures that the 'afllnitive capacity of each particle has been satisfied to permit thorough coating of each particle with its maximum thickness of water film. That is, in standard flotation only those minerals of high adsorptive power are able to adsorb sufficient of the flotation reagents to fiotatively modify their surfaces through, displacement of water film by reagent film. If the affinity of the particle for water is greater than its adsorptive power in respect to the reagents employed, it follows as a matter of course, that no concentration of reagents will serve to modify the particle for selective separation by flotation if the afflnitive capacity of such particle has once been satisfied.

Water regulation, as hereinafter described, has several functions when employed with the, other steps of the improved method. Since a reduction in the'amount of variable-film water results in advantages of economy and separation, it might appear that entire elimination of the free water and treatment of the material in a dry condition would be ideal. This is not the case. Due to variations in composition of. the materials, fineness of grinding, thoroughness of agitation, and the like, it is found practically inexpedient to determine the exact minute quantity of flotation reagents to be applied to a given dry material to float just the mineral desired, excess reagent bringing up undesired mineral and insufficient reagent failing to bring up the desired percentage of mineral sought.

In addition, it is expensive to thoroughly dry the material in the first instance and very difiicult as well as expensive to maintain the dry condition of the material and prevent adsorption of water thereto from the atmosphere during conditioning and treatment. Consequently, the improved method does not contemplate entire elimination of the-variable-film water and utilizes as a lower limit on the amount of variablefilm water that amount which could be adsorbed to the material from the atmosphere, which lower limit may be but infrequently approached in actual practice.

The variable film water thus ever present in the material to be treated is utilized for its inhibiting efiect on the material particles of greatest aflinity therefor to the end of insulating said particles from adsorption of reagents and permitting the use of suflicient quantity of reagents to flotatively modify all of the desired particles without danger of dirty concentrates.

In other words, the variable-film water acts to further lower'the adsorptive power eifect of the relatively lower adsorptive-powered particles and thus more definitely establishes .the line of flotative separation between particles of the mix.

A further reason for leaving a certain amount of variable-film water in the material may be found in the fact that certain of the flotative reagents require a vehicle of solution and a fluid medium to facilitate spreading thereof throughout the material, both of which requirements can be met to a considerable degree and to ad-' vantage by the variable-film water inherent in the material.

In addition, instances occur when the variable! film water serves both of the foregoing functions I and acts as an adsorptive inhibitor while simultaneously aiding as a solution vehicle and as a spreading agent.

The reasons for a moist condition of the material as utilized in the improved method may then be listed as follows:

1. Because it is impractical to determine the exact amount of reagents required for a given separation.

2.' Because of the expense of drying material and maintaining the material in a dry condition.

3. Because moisture acts as an insulator to inhibit adsorption of reagents to material particles, thus permitting use of enough reagent to float all of the desired particles.

4. Because moisture permits of more definitely establishing of the line of fiotative separation of a mix.

5. Because moisture acts as a vehicle of reagent solution and as a fluid medium to facilitate spreading of reagents throughout the material being treated.

6. Because moisture acts simultaneously as an adsorptive inhibitor, a solution vehicle and a spreading agent.

7. Because moist condition of the material permits use of less quantities of reagents due to enhanced action and effect of such reagents when in'concentrated condition.

It has long been recognized that a tremendous difference exists in respect to affinity and adsorptive power for water and flotation reagents between the metals and sulphide minerals on the one hand and the silicates and the oxides on the other hand, but it has not previously been shown that sufficient differences in adsorptive powers of the silicates and oxides existed to permit of their selective separation within their own classifications as well as one from the other.

Through application of the improved technique taught herein, and especially through regulation and control of the variable-film water in a moist mixture, it can be practically demonstrated that each and every mineral has a distinct and definite afinity for water and a distinct and definite adsorptive power in respect to each of the various flotation reagents, which characteristics may be employed to effect froth flotation separation of the minerals, including even those of exceedingly lower adsorptive powers.

' For a better understanding of the effects and results obtainable through regulation of variable-film water in an ore mix, it might be well to consider the aflinitive capacity of a given mineral particle as representing the number of water layers of uniform thickness adherent to the surfaces of such particles from an excess supply of water and which will adhere to such particle when the excess water has been drained away. Thus, a mineral particle with an amnitive capacity of 1 would, in the presence of adequate water, surround itself with a water film of one layer thickness, while a mineral particle-with an amnitive capacity of 10 would, in the presence of adequate water, surround itself with a water film of ten layers thickness, or ten times as thick as the film carried by the particle of one-tenth amnitive capacity.

The thickness of water film represented by the afilnitive capacity of the particle will be retained by such particle after draining away of excess water, and it is with variation in the thickness of such film that regulation of the variable-film water is concerned.

When any interstitial water is present in an ore mix the afiinitive capacities of all of the mineral particles have been satisfied and all such of like thickness on the particles of like capac-- ity, eventhough much less in thickness, due to insuificient water, than the maximum film possible for the particular particle capacity, and such higher powered particles will continue to take up and uniformly holdthe available waterto the exclusion of the lower powered particles until the .unsatisfied aiiinitive capacities of the higher powered-particles are brought to approximately that of the lower powered particles.

It would appear from results experimentally obtained that the higher afiinitive powered particles may in many instances abstract water film from lower afiinitive powered particles until the afiinitlve capacities of such higher powered particles are completely satisfied, so that only such excess as may exist above the aflinitive capacities of the higher powered particles is available for water-filming of the particles of lowerafiinitive capacities. I

The regulation of variable-film water herein taught is concerned with regulation of the amount of variable-film water in the ore mix to that which will provide water film of the desired thickness for the purposes of a given separation on and about some or all of the particles of the mix, such regulation, naturally, being proportioned to the afiinitive capacities of the particles in relation to the adsorptive capacities of such particles in respect to the reagents to be employed. a

It should be obvious that no specific limits, in the form of weight percentages or otherwise, can be established for control of the variable-film water apartjrom the upper and lower limits previously stated, since marry factors enter into the determination of the exact amount of variablefilm water required for-successful fiotative separa tion of a particular ore mix, not the least of which factors is the degree of comminution'to which the mix has been brought, it being apparent that it would require a much greater amount of water to film each particle ofja'200 mesh grind than it would to film each le of a a mesh grind of the same weight, filmthickness being equal.

- Specific gravity of the various particles is also a factor.

Application of the improved technique to fiotative separation of a given mineral involves conslderation of two determinants, namely the water afllnity of the materials to be separated and the relative adsorptive powers of such minerals in respect to the reagents to be employed. Where the mineral to be floated has great adsorptive power in respect to the reagents and is combined with a gangue of low adsorptive power, as is Even in' the situation cited, however, nicety of separation and economy of reagents can be en hanced through control of the variable-film water to that amount readily filmable about the loweradsorptive-powered particles only, thus supplying such particles with the desired inhibitor and freeing the higher-powered particles for efi'ective fiotative combination -with a relatively min amount of the reagents.

Where it is desired to fiotativeiy separate one mineral of high adsorptive power from of like character, the relative'water amnity ofthe minerals is of great importance, since it is in many such cases impossible to' gauge the reagents required in a wet mixture to that amount which will fiotatively adsorb to those particles only off'the slightly higher powered mineral. -In such a case,

regulation of the higher variable-film water to an amount less than will satisfy the water ailinity of'all of the particles results in maximum concentration of water on and about the particles of greater aifinity with maximum insulation of such particles against adsorption of reagents thereto,

while the particles of lesser afilnity, possibly having lost water film to those of higher. affinity, are enabled to exert a relatively much higher adsorp-. tive power and effect a fiotative concentration of reagents on their surfaces to the exclusion of the water-finned particles from such concentration, when a small amount of reagents is employed.

The more closely the variable-film water is regulated to that amount conibinable with only the particles of greater afiinity, thus substantially freeing the particles of lesser afiinity from water film, the more complete and perfect can be the fiotative separation and the smaller can be the quantity of reagents requiredtherefor.

' When the separation desired is'to be had between minerals of low adsorptive powers or high amnities, regulation of the variable-film water is of primary importance, since the presence of a thick water film on all of the particles will, in

most such instances, inhibit flotation of'any of a the particles.

In treating such lower-adsorptive-powered minerals for fiotative separation, it may be necessary to regulate the variable-film water to an amount less than will satisfy the affinity of the mineral having the relatively greater water afiinity, thus freeing the particles of lesser afiinity from water film so that no inhibiting effect is present as between reagents and such latter particles and the low adsorptive power of such particles may then act to effect flotative concentration of reagents on and about such particles while those particles of greater aflinity are completely insulated by water film and can adsorb none of the reagents whatever.

With some minerals of low adsorptive powers, notably silicates, a dry condition of the mix treated with a quantity of reagents suiflcient to satisfy the adsorptive capacities of the minerals present permits adsorption of reagents to all of the particles and a consequent non-selective fiotation.

Hence it follows that both water film and reagent film are essential for the desired selective flotation separation, the first to act as an inhibitor in respect to flotation of certain particles and the second to be adsorbed to and effectflotation of the desired particles, and that regulation of the variable-film water coupled with a suitable proportioning of reagents is the prerequisite to flotative separation of minerals other than those of notably great adsorptive powers.

As indicative of the importance of regulation of the variable-film water in flotation separations, a mix of beryl and feldspar may be considered. Simply to better illustrate the point, the water affinity of the beryl is given a value of 20 and feldspar may be given an arbitrary aflinity value of 25, the adsorptive power of the beryl for oleic acid a value of 10, and the adsorptive power of the feldspar for oleic acid a value of 5. With the variable-film water of the mix regulated to one tenth of one percent, the water afilnity'of the minerals is only partially satisfied but not sumciently so as to destroy their adsorptive power values. Assuming that the water supplied by the small amounts of added variable-film water now has only a value of 3, it is seen that there still remains some available adsorptive power in each mineral and also an unsatisfied aflinitive capacity; the available adsorptive power of the beryl having a value of '7 and that of the feldspar a value of .2. Now if oleic acid be added to the mix in an amount not, quite sumcient to satisfy the adsorptive capacity of the beryl, such reagent will be adsorbed to the beryl and abstracted from the feldspar particles until the adsorptive differential of the beryl is satisfied to the extent per mitted by the reagent supplied, and the beryl particles can be floated from the feldspar in a froth flotation cell. However,, since both the beryl and the feldspar have greater amnity than adsorptive power, continued agitation of the'particles in a body of water will result in replacement ofv reagent film by a water film and less of any flotative characteristic, with consequent sinking of all particles, though the adsorbed reagent will adhere to the beryl long enoughto effect a froth separation of the beryl from the feldspar. Any

' excess of reagent in the above example beyond that required to satisfy the adsorptive dlfl'erential of the beryl would lie-adsorbed to the feldspar, providing the latter did 'not have too thick a film of variable-film water, andresult in dirty concentrates and poor separation. Treated dry with suflicient-olelc acid to satisfy their respective adsorptive needs,'the particles of both min-- erals of the above mix could be floated together. Going to the other extreme, there is the case of a mix of galena and'feldspar. Thegalena might have an aflinity :of '1 and an adsorptive power of 100 and consequentlycouldnever have its film of reagent replaced-by water film so long as any reagent was present, though excess reagent applied to such a mix when dry would result in flotation of some feldspar. The ideal treatment for such a mix would include regulation of the vari-.

able-film water to an amount suflicient to satisfy the aflinity of the feldspar and prevent any adsorption of reagent thereto, in which even either large or small amounts of reagent would 'serve to efliciently float the galena alone.

Because of the varying adsorptive powers a' given mineral may exhibit in respect to various reagents and because of the almost infinite mineral combinations wherein separations are desired, it is impossible to establish any one general rule as to regulation of the variable-film water as employed in the improved method. However, the minerals to be dealt with may be divided into two general classes according to the relation each shows between its water affinity and its adsorptive power in respect to flotation reagents in use at the time, such a grouping resulting in one class, Class I, containing the minerals having a water afilnity generally greater than their respective adsorptive powers and which includes nearly all silicates, many of the oxides, some of the carbonates, hydrates and sulphides, and some other less common types of minerals, and a second class, Class II, containing the minerals having adsorptive powers generally greater than their respective water amnities and which includes the metallics, most sulphides, many organic minerals, some carbonates, some non-metallics, a few oxides and practically no silicates.

In respect to these classes it may be generally stated that flotation separations can not be made commercially with minerals of Class I when standard methods are employed and the variable-film water is of suflicient amount to permit any interstitial water in the mix, since in such case not only is the water aflinity of the mineral satisfied, but an excess is represented by the interstitialwater; and that flotation separations can be made wlthminerals of Class II when the variable-film water is of such quantity as to provide interstitial or more water. However, some minerals may be in Class I with respect to certain flotation reagents and in Class II with respect to other such reagents and the allocation of a specific mineral to either class may change during treatment due to surface modification by reagents, hence the character and requirements of a given combination to be separated will need to be studied to determine the specific treatment in respect to water regulation best suited to the situation. Again, speaking'generally, the follow- 7 ing guidm may be established for regulation of variable-film water in making separations of minerals classified as above set forth:

B. For separation in one concentrate of one Class II mineral and one class I .mineral from 7 other Class I minerals-Regulation of variable-film water required and no interstitial water permitted, in order to float the Class I mineral.

C. For separation of one Class I mineral from another Class I mineral-Regulation of variable-film water required and no interstitial water permitted.

D. For separation of one Class II mineral from another Class II mineral-Possible with excessive water, interstitial water or with variable-film water only, in various specific instances. Generally, better and more delicate separations possible with regulation of variable-film water as in "0.

As indicative of the difliculty: attendant upon any attempt to establish a rigid classification based on the flotative characteristics of minerals, sphalerite (ZnS) may be specifically considered. This mineral can not be floated by standard methods, nor even with the ore in a moist condition, when potassium ethyl xanthate' is employed as the flotation reagent. hence is in Class I with respect to xanthate. However, when copper sulphate is added to the ore pulp prior to the anthate, the sphalerite evidences a greater adsorptive power for the copper sulphate than amnity for water and consequently suffers an adsorptive surface modification by the copper sulphate resulting in a surface coating of the sphalerite particles with copper sulphide, which coating has such great adsorptive capacity for xanthate as to permit flotatlve concentration of such reagent on and about the coated sphalerite particles in the presence of excessive water, the coated particles. now being in Class II insofar as xanthate is con-v cerned. However, the uncoated sphalerite in a moist ore condition and after proper regulation of the variable-film water can be floated with oleic acid as a reagent, since, with the water film about thesphalerite particles reduced to proper thickness by variable-film water regulation, the relatively small adsorptive power of the mineral relative to oleic acid is notentirely negatived by water film andmay act to flotative concentration of such reagent on and about the mineral particles.

As a concrete exampleof the flotation possibili ties inherent in regulation of variable-film water, comparative tests were run on a coarsegralned (20 mesh plus mesh) silica glass sand. This material contained pure silica grains, impure and discolored silica grains and grains of foreign matter here designated as mineral grains, and was chosen for test purposes because all authorities agree that coarse silica can not be floated, let alone separated from the impure I grains. The material was thoroughly washed and scrubbedand200gramsampleswereused ineach I of the following four tests:

Test I. Variable-film water present only that taken up by the-material'from the atmosphere. approximately 5th of one percent by wei ht of material. 3 drops of oleic acid (0.75 lb. lier ton) added to the sample and thoroughly mixed therewith. After one minute agitation in a froth flotation cell 13'! grams (68.5%) of pure silica and mineral grains floated. The concentrate was of much better color than the tails.

Test 11'. Conditions thesame as in Test I save that 5 drops of oleic acid (1.25 lbs. per ton) were employed. Flotation concentrate 187 grams (93.5%) and improvement in color more marked than in Test I.

TestIII. ConditionsthesameasinTmt IIsave that 1 c. c. of water (55 of 1%) was addedto and mixed with the sand before the admixture of the oleic acid. Concentrate 6 grams composed entirely of the mineral grains having relatively high adsorptive powers. No silica floated due to the inhibiting effect of the variable-film water.

These tests conclusively show the advantages to be gained through regulation of the variablefllm water and consequent variation in the thickness of water film adherent to ore and mineral particles, and thoroughly demonstrate the novelty of the improved method.

Treated dry with the proper amountof oleic acid, the entire sample could be floated and no separation had, hence the water limit range wherein the variable-film water regulation taught herein may be most effectively employed is from just above the dry condition to an amount Just below that which would provide interstitial water in the material. Within such range, proper regulation of the variable-film water permits of selective flotation as between materials not-previously considered flotable and between materials of closely similar adsorptive powers and capacities.

In addition to the possibilities of water regulation above discussed, it has been determined that small amounts of certain chemicals commonly employed as flotation reagents will spread to form extremely thin films over moist granular minerals, and this principle is applied in the improved method of treating ores and minerals to facilitate, modify and control the separation of the desired ores and minerals from the gangue or other material with which they may be associated. This treatment is applicable to a wide range of substances and it is believed that the reagent or reagents used on thismore or less moist material has the effect, in some cases, of reacting chemically with certain constituents of the particles to form compounds that modify the behavior of the particles when subjected to froth flotation. In other cases, however, it is believed that the treatment modifies the adsorptive powers of the particles or of certain constituents thereof, and also has the eiiect of producing marked changes in the behavior of theparticles in the froth flotation cell.

In a word, therefore, the invention relates broadly to variable-film water regulation of ores, minerals and inorganic compounds and subsequent treatment of the water regulated material with a reagent or reagents for modification and control of the material behavior when subjected-to froth flotation, and more specifically to treatment of such water regulated material with relatively concentrated reagents in comparatively minute quantities prior to froth flotation.

novel featum of operation and the new and original arrangements and combinations of steps intheprocesshereinafterdescrihedandmore od, the ore, mineral or inorganic compound to be The invention further consists in the new and ,treatedisground orotherwisereducedtotheiineness required by the particular type of material tobetreated. Ifthematerlalcontainsametal suchasiromcopperorsinccompoundsinafine' state of subdivision the oreormatrix,

then the material is ground to a fineness which may be determined by any well-known method to expose, if possible, all or part of the desired mineral on the surfaces of the respective particles. The degree of grinding can be determined by metallographical examination as well as by empirical or practical tests. In the case of nonmetallic ores where it is desired to separate the different minerals or different purities of the same mineral, the ground particles may be appreciably coarser and still float and separate. No fixed range of fineness is required except that the material must be in condition readily to pass through the standard froth flotation cell and the exact amount or degree of fine grinding is usually ascertained by observation or simple test.

The ground material is first regulated as to variable-film water content to control the thick ness of water film on and about the particles, or certain particles, of the mix in accord with the principles hereabove set forth and to best suit the character of the materials and the nature of the separation desired, whereafter it is mixed with a reagent or reagents in comparatively concentrated form. If the reagent employed is normally a solid, it must be put into solution or enough water must be present in the ore to effect the desired solution and aid in the spreading of the reagent. The reagents employed encompass a wide range, depending on the physical condition of the material to be treated and its metallographical and molecular structure. In certain cases, it may sometimes be desirable to add a small quantity of sulphuric or other acid prior to or simultaneously with the addition of the other reagent or reagents in order to remove any oxidized film from the surfaces of the desired particles, or otherwise to help in the later flotation thereof. Also, appropriate neutral diluents may be used to determine the viscosity and spreading ability of the reagents. While an addition of sulphuric acid has at times been found desirable to clean particle surfaces and permit better adherence of other reagents thereto, it may be found preferable in certain cases to employ an alkali to enhance the action of the reagents used for flotation. The addition of alkalies or acids follows the same well-known facts as are now applied to standard flotation practice for hydrogenion concentration or, as it is better known, pH control.

Some ores, such as the Florida phosphates, certain manganese oxides, carnotite, and other more or less sponge-like minerals, require not only the water regulation as herein described, but the addition of inactive reagents to fill up their pores before the addition and admixing of the collecting reagents. Such inactive reagents have no effect except that of lessening the cost and amount of the higher cost active reagents necessary for the final separation. When such ore is thus treated, the total amount of reagent used, both active and inactive, is much less than when the material is treated by present standard methods.

The well-known flotation reagents, including collectors, frothers, sulphidizers, and activators and depressants, and others such, for illustration, as the fatty acids and their derivatives, the xanthates, sodium sulphide, pine oil, and the like, have been found useful in treating a wide variety of minerals.

The greatest difference in flotative effect between the standard wet method and the improved process is most often noticed where the reagents used are those that are insoluble or only slightly soluble in water. The latter method is better because actual contact is obtained between mineral particle and reagent where they are mixed in the moist condition, for this assures the filming of the particle surface and its consequent flotation. Where the more water soluble reagents are used the advantage in using the improved method lies in the fact that they are in a more highly concentrated condition and, therefore, less reagent is needed and the action on the particle surface is much faster and more positive. 19

The reagents are used in very small quantities, such quantities being in the order of one onehundredth of a pound per ton of treated material to 40 pounds per ton of such material, according to the nature of the material and the degree of fineness to which it is ground.

The material and the reagents should be thoroughly mixed although no elaborate apparatus is required for this purpose. The reagents seem to spread by contact and in a comparatively short time will permeate and cover a large mass of material. It has been found in certain cases that mixing may be accomplished to a satisfactory extent by adding the reagents in small amounts to the material as the latter is. fed to one of various types of well-known mixing apparatus, it being necessary in many cases only to bring the particles for a brief period of time into contact with the reagent itself or with other particles to which the reagent has adhered.

Repeated tests have definitely proved that minute amounts of certain reagents can be made to spread, by agitation, and cover the surfaces of a large number of slightly moist ore particles of varying sizes from very fine to rather coarse.

Different materials have different adsorptive powers for different reagents and, of any two minerals, one has a greater adsorptive power than the other for a certain reagent. The fact that different minerals have these different powers is most forcibly demonstrated when the ore is only slightly moist and contains less than onefourth of one percent of variable-film water, by weight. While it is in this condition any reagent added and mixed with the particles is in an extremely concentrated condition as compared with standard froth flotation practice. These concentrated reagents are then able to cover the particles of moist ore with a film and are immeasurably better able to attach themselves directly to the surfaces of the particles by from the surface of one mineral to the surface of another. Contact of the particles is all that is needed to make this transfer of reagent film.

When the adsorptive, or other, needs of the strongest minerals have been satisfied, any extra reagent is taken up on the surfaces of the next strongest mineralparticles and, when enough reagent is present-to satisfy the adsorptive needs of all of the particles, all non-inhibited particles will float.

First-200 grams of 30 plus 100 mesh silica sand regulated to th of 1% variable-film water was mixed for 5 minutes in a glass bottle with 4 drops of oleic acid and 1 drop of terpineol (35 drops equal 1 c. c.)

Second-25 gi'ams of the above was put in a flotation cell. 24.5 grams floated.

Third-To the 175 gram balance of the sand was added 200 grams of pink potash feldspar, 30 plus 100 mesh. The sand and feldspar were mixed for five minutes in the bottle. From this mix 25 grams was put in the flotation cell. 12 grams floated and this was feldspar.

Fourth.To the 350 gram balance of sand and feldspar was added grams of light blue beryl. This had been crushed to -20 mesh. All were mixed in the bottle for 10 minutes. 25 grams were put in the flotation cell and 4.5 grams floated which was nearly pure beryl.

Flfth.To 425 grams balance of sand, feldspar and beryl was added 100 grams of 30 mesh crystalline limestone. All were mixed for 10 minutes in the bottle and then the entire 1 525 gram sample put in the flotation cell. The concentrate was 94.5 grams of lime of 98% purity.

These tests show how the sand, which had the original film of reagents on the particles and would therefore float, then had this fllm abstracted from it and adsorbed by the feldspar; themix of sand and feldspar lost to the beryl and this last lost to the limestone. No other reagents were added during the test and the fllm of reagents formed by the 4 drops of oleic acid had to be transferred from the surfaces of one mineral tov the surfaces of the stronger as the latter was added and mixed with the others.

The length of time that the mixture stands prior to its introduction into the flotation cell' has, in some cases, a very decided effect in the subsequent froth flotation. In the case of some very slightly moist silica sands containing pure and impure grains, if the mixture is allowed to stand for approximately flve minutes and then introduced into the flotation cell, none of the grains will float. But if the mixture is allowed to stand for a period of two hours after passing through the mixing apparatus, the pure silica grains are immediately floated to the top of the cell and the impure grains do not float. Apparently, when the ,afllnitive capacity of the grains is nearly satisfied, it takes a longer time of contact for the reagents to act on or replace the variable-film water to flotatively modify the grains sumciently to float them.

The froth flotation cell may be of any standard and well-known makeadapted to supply the requisite amounts of water and of air or other gas now required under ordinary operating conditions. No special form of cell appears to be necessary in order to practice the invention with improved results compared to present day methods. Other froth flotation reagents may be added chromium oxide with silica terpineol.

added to the cell or different reagents may be employed, if desired. The exact method of adding the flotation reagents which were not originally mixed with the moist ore is not essential to the operation of the process and forms no part of the instant invention. Because of the fact that the particles of the ore to be floated have already been covered with a fllm of the reagent needed to modify the surfaces and either prevent their being wet by water or otherwise change the surface characteristics, these particles are much more quickly floated than if treated by standard flotation methods. This ease of separation and quickness of flotation will greatly reduce the number of froth flotation. cells needed in the mill and thereby reduce not only the installation costs but the costs of operation in the flotation unit as well.

The following examples of the practical application of the improved method to certain minsodium oleate; 0.6 lb. of 15% aeroflot; 2.0 lbs. so-

dium sulphide. The mixture was put in a'fiotation cell and the following quantity of reagents per ton of ore added to the cell; 0.25 lb. potassium xanthate and 0.1 lb. terpineol. The concentrate was 3.6%

weight of the whole and assayed 0.23% copper. The recovery was equal to 78.7% of the copper.

by weight of the whole and assayed. 23.03% copper. The taillngs were 96.4% by When this same ore was treated by standard wet flotation methods, only 6% of the copper was recovered.

Example 2.-The ore treated was low grade gangue. The ore was crushed to pass a 30 mesh screen and waterregulated to 3% by weight of variable-film water and then mixed with 0.2 lb. oleic acid and 0.3 lb. terpineol per ton of ore. to the flotation cell. The flotative concentrate was equal to 6.8% 01' the weight of the ore and assayed 47.31% C1'203. The tailings were equal to 93.2% of the weight of the ore and assayed 2.25% CrzOs, giving a recovery equal to 59.1%. Treating the same ore with the same kinds and amounts of reagents by standard wet flotation methods produced only an 18% recovery of the was crushed to pass a 20 mesh screen and waterregulated to 3% of variable-film water. The ore was then mixed for five minutes with the following reagents in quantities per ton of ore as shown; 0.6 lb. of potassium xanthate, 2.4 lbs.,of sodium sulphide, 0.4 lb. of 15% aeroflot. The mixture was put in a flotation cell with water alone and a concentrate consisting of bornite, copper oxides and a little chalcopyrite was removed. After the first concentrate was removed, the following reagents per ton of ore were added to the flotation cell; 0.2 lb. of potassium xanthate and 0.1 lb. of The second concentrate was nearly all chalcopyrite with a little bornite. A total saving of 94.6% of the copper was made in the two concentrates which were nearly pure mineral. The first concentrate equalled 12.6% by No reagents were added weight of the total concentrate. The second concentrate equalled 87.4% of the total concentrate. Treatment of the same mix by standard wet flotation methods using the same reagents recovered only 74% of the total copper, the oxidized sulphide particles and'the true oxides not floating with the standard methods.

This example shows how certain of the oxidized and oxide grains of copper-ore could be easily sulphidized when a concentrated solution of NazS j was used and this material then floted by the xanthate.- The second concentrate would have come up with the first if the full amount of xanthate hadbeen added at once. i

Example 4. -B eryl ore (Be3A1z(SiOa)6) assaying approximately beryl and with a'gangue or matrix of feldspar and quartz was ground to agents nothing floated.

Example 5.Impure silica sand was passed through a 20 mesh screen, water-regulated to about 5th of 1% variable-film water and mixed with 1.0 lb. o1 oleic acid and 0.2 lb. of terpineol per ton of sand. This mix was allowed to stand for two hours and was then put through a standard flotation cell with water "alone. The pure sand floated in the froth from the cell equalled,

98.8% by weight of the total sand and the impure rejected sand not floated comprised 1.2% of the total weight of the sand, the. floated sand being.

practically all pure-silica. Coarse silica sand can not be floated by standard wet flotation methods.

This last example shows how normally nonflotable silica can be floated if the variable-film water is kept low and also how two minerals, both having a higher aflinity for water than adsorptive power for oleic acid must carry only a very thin film of variable-film water in order to effect a separation therebetween in the flotation cell.

As shown in the foregoing examples, theimproved method may be successfully employed to treat a large number of desirable minerals readily floatable thereby, which minerals are floated with difliculty, or not at all, when standard wet flotation methods are employed.

As illustrated by the examples set forth, less reagent is required in practicing the improved method than is exacted in the present standard methods, which standard methods will not even float many of the materials flotable by the improved method. Furthermore, the improved method is deflniteand positive in its reactions, since the reagent is therein brought into direct and intimate contact with the particles ina concentrated form instead of being disseminatedthrough a relatively large body of water where the contact of each individual particle with reagent is more or less a matter of chance.

A much wider range of reagents is permissible by use of the improved method, since the reagent is applied directly to the surface ofthe ore or mineral in a relatively'concentrated form. Reagents of a difierent character which will not properly adhere to the ore or mineral in the presence of excess water or have any chemical efiect in a dilute condition may be employed successfully when the ore is treated directly and by relatively concentrated reagents.

In general, no special drying operation is re quired in carrying out the improved method, although if such drying is required for any reason it will not interfere with exercise of the method unless the drying temperature employed on the mix of ore and reagent is carried above the vaporizing or boiling points of the reagents. Where water-regulation to very low amounts of variable-film water is required, it might be found best to dry the ore by application of heat to that percentage of retained variable-film water desired, or it might, in specific instances, prove better to entirely dry the ore and then add the desired percentage of water, Commercial expediency should of course control the degree of water-regulation within the limits of practical recovery desired, since, in certain instances, the cost of drying an ore forremoval of a slight excess of water might easily be greater than the added recovery resulting from such refinement of water regulation. The ore can be ground while moist and thereafter the reagent can be mixed therewith, or, as will be obvious, the reagent can be mixed in the grinder with certain classes of ore, during the grinding operation.

It is to be understood that the terms ores and minerals, as used herein, are not restricted to these materials in their natural state or condition, but comprise the products of metallurgical operations and concentrates from previous flotation processes and likewise many non-metallic minerals.-

In view of the many changes, additions, omis sions and modifications possible, and indeed necessary, in the application of the improved method to specific separations by those skilled in the art, wherein no departure from the spirit and essence of the invention is involved, it is to be understood that the invention is limited solely by the scope of the appended claims, rather than by any details of the foregoing exposition.

I claim as my inventionl. The method of preparing sands, comminuted ores and similar materials for separation by froth flotation which includes regulation of the moisture content of the material between an upper limit less in amount than will satisfy the ailinitive capacities of all of the separated particles and a lower limit determined by the amount of moisture adsorbable to the material from the atmosphere, and subsequent thorough admixture with the moisture-regulated material of relatively minute quantities of selective reagents.

2. The method of preparing sands, comminuted ores and similar materials for separation by froth flotation which includes regulation of the moisture content of the material to a variable-film quantity less than will satisfy the ailinitive capacities of all of the separated particles, and subsequent thorough admixture with the moistureregulated material of relatively minute quantities of selective reagents.

3. The method of preparing sands, comminuted ores .and similar materials for separation by froth flotationwhich includes regulation of the thickness of water film adherent to the material particles so that the maximum moisture content is less than will satisfy the afllnitive capacities of all of the separated particles, and subsequent thorough admixture with such moisture-regulated material of relatively minute quantities of selective reagents.

and a lower limit determined by the amount of moisture adsorbable to the material from the atmosphere, and subsequent thorough admixture with the moisture-regulated material of relatively minute quantities of selective reagents.

5. The method of preparing sands, comminuted ores and similar materials for separation by froth flotation which includes effectively selective modification of the adsorptive capacities of the material particles through regulation of the moisture content of the material to a variable-film quantity less than will satisfy the afiinitive capacities of all of the separated particles, and subsequent thorough admixture with the moistureregulated material of relatively minute quantities of selective reagents.

6. The method of preparing sands, comminuted ores and similar materials for separation by froth flotation which includes efl'ectively selective modification o! the .adsorptive capacities of the material particles through regulation of the thickness of water film adherent to the mate'- rial particles within a total maximum amount of water film less than will satisfy the aflinitive capacities of all of the separated particles of the material, and subsequent thorough admixture with the moisture-regulated material of relatively minute quantities of selective reagents.

7. The method of preparing sands, comminuted ores and similar materials for separation by froth flotation which includes effectively selective modification of the adsorptive capacities of the material particles through regulation of the thickness'of water film adherent to the material particles within a total maximum amount of water film less than will satisfy the aihnitive capacities of all of the separated particles of the material, and subsequent. thorough admixture with the moisture-regulated material of relatively minute quantities of selective reagents,

and continued agitation of such admixture to effective concentration of the reagents on and about those particles ofgreater adsorptive capacities.

8. The method of preparing sands, comminuted ores and similar materials for separation by froth flotation which includes effectively selective modification of the adsorptive capacities of the material particles through regulation of the thickness of water film adherent to the material particles within a total maximum amount of water film less than will satisfy the afilnitive capacities of all of the separated particles of the material, and subsequent thorough admixture withthe moisture-regulated material of relatively minute quantities of selective reagents, and time-conditioning of such admixture while in the moist condition to effective concentration of the reagents on and aboutthose particles of greater adsorptive capacities.

9. The method of selectively separating sands, comminuted ores and similar materials which comprises modification of the adsorptive capacities of the material particles through regulation of the moisture content of the material below a maximum less in amount than will satisfy the ailinitivc capacities of all of the separated particles, thorough admixture with the moistureregulated material of relatively minute quantities of selective reagents, and agitation of the resultant admixture in a froth flotation cell for separation of the desired particles.

10. The method of selectively separating sands, comminuted ores and similar materials which comprises selective modification of the adsorp-- tive capacities of the material particles through regulation of the moisture content of the material to a variable-film quantity less than will satisfy the affinitive capacities of all of the separated particles of the material, thorough admixture with the moisture-regulated material of relatively minute quantities of selective reagents, and

agitation of the resulant admixture in a froth fiotation cell for separation of the desired particles.

11. The method of selectively separating sands, comminuted ores and similar materials which comprises selective modification of the adsorptive capacities of the material particles through regulation of the thickness of water film adherent .to the material particles within a maximum total amount of water fllm less than will satisfy the afllnitive capacities of all of the separated particles of the material, thorough admixture wit-I1 material of relatively minute quantities of selective reagentaand agita-v the moisture-regulated tion of the resultant admixture in'a frothflota+ tion cell for separation of the various particles.

12. The method of selectively separating sands,

comminuted ores and similar materials which comprises'selective modification ofthe adsorp- I tive capacities of the material particles through regulation of the thickness of water film adherent to the material particles within 'a maximum total amount of water fllm less than will satisfy.

the afiinitive capacities of all of the separated particles of the material, thorough admixture with the moisture-regulated material of relatively minute quantities of selective reagents, continued agitation of such admixture while in g the moist condition to effective concentration of the reagents on and about those particles of greater adsorptive capacities, and subsequent agitation of the resultant admixture in a froth flotation cell for separation of the various particles.

13. The method of selectively separating sands, comminuted ores and similar materials which comprises selective modification of the adsorptive capacities of the material particles through regulation of the thickness of water film adherent to the material particles within a maximum total amount of water film less than will satisfy the affinitive'capacities of all of the separated particles of the material, thorough admixture with the moisture-regulated material of relatively minute quantities of selective reagents, time-conditioning of such admixture while in the moist condition to effective concentration of the reagents on -and about those particles of greater adsorptive capacities, and subsequent agitation of the resultant admixture in a froth flotation cell for separation of the various particles.

14. The method of preparing sands, comminuted ores and similar materials for separation by froth flotation which includes the regulation of the variable-film water to that amount which prevents the adsorption of the selective reagents by certain only of the mineral particles but permits such adsorption by the other mineral particles, thorough admixture of the moist ore with the desired reagents, and subsequent separation of the particles in a froth flotation cell.

15. The method of preparing sands, commiamass? nuted ores and similar materials for separation by froth flotation which includes the regulation of the variable-film water to that amount which prevents the adsorption of the selective reagents by certain only of the mineral particles but permits such adsorption by the other mineral particles, thorough admixture of the moist ore with the desired reagents, continuation of contact between the moist ore and reagents while still in the moist condition a predetermined length of time, and subsequent separation of the particles in a froth flotation cell.

film water of the mixture to an amount less than will satisfy the aflinitive capacities of all of the material particles, and subsequent separationof the particles in a froth flotation cell.

17. The method of preparing sands, comminuted ores and similar materials for separation by froth flotation which includes the regulation of the variable-film water to an amount less than will satisfy the aflinitive capacity of the material, thorough admixture of the moist material with neutral reagents to satisfy absorptive needs of the material, thorough admixture of the conditioned material with collecting reagents, and subsequent separation of the material particles in a froth flotation cell.

THEODORE EARL-E.