US2395866A - Flotation process - Google Patents

Description

Patented Mar. 5, 1946 FLOTATION PROCESS Gregoire Gutzeit, westport, Conn.

No Drawing. Application September 8, 1943,

Serial No. 501,564

6 Claims. (01. 209-166) The present invention relates to flotation, and mor particularly to the recovery of desired minerals from ores containing the same by application of froth flotation methods.

Froth-flotation is roughly based on the fact that the surface of a given mineral to be recovered can be rendered, by the action of socalled collectors, more or less water repellent, i. e. aerophil, and a mineral-air complex, the specific gravity of which is lower than that of the pulp, is thus formed with the air bubbles introduced into the pulp.

Although the usual gangue minerals (with a few exceptions like talc, graphite, etc.) when pure, are naturally more hydrophilic than the valuable metal bearing ones, they are easily floated after activation with metalliccations. Thus, quartz and most other silicates may be activated by very small amounts of iron, copper, zinc, lead, nickel, tin, titanium, barium and some other cations, and calcite by barium, copper, iron, and lead salts when floated with fatty acid or fatty alcohol collectors at pH values varying with each activating ion. Since in almost every pulp there are soluble metallic salts present such as dissolved iron from the ball-mill, or copper,

zinc, or iron sulfates from the oxidation of sul-- flde-minerals, the gangue is always more or less objectives in view and. for the accomplishment of the same, it proposes to add to the flotation pulp relatively small amounts of certain organic compounds, which will be described presently, that react with the extraneous metal cations present so as to prevent the activation and flotation of unwanted gangue minerals by the agency of such cations.

Broadly, the invention embraces the addition to a flotation pulp of an organic reagent able to form very stable, water soluble, or insoluble but hydrophilic, inner complexes (chelate com- Pounds) with the extraneous metallic'cations in solution or adsorbed on the mineral particles,

whereby such ions are prevented or inhibited from exerting an activating effect on the gangue particles.

These specific organic reagents must possess in their molecule certain groups capable of unit-- ing with metals through the replacement of the acidic hydrogen, the metal in the resultant compounds being' held in position by a primary or electro-valence, and, on theother hand, other roups being capable of combining with metals through the coordination bond, that is, without the replacement of hydrogen. If these two functional groups are both attached to one single organic radical in the proper relative position such as to satisfy the Baeyer strain theory, a cyclic structure will be formed which is known as an inner complex or chelate compound. The metal atom in these four-,' fiveor six-membered rings is most frequently attached to a nitrogen, oxygen or a'sulfur atom by electrovalence (salt formation), and it completes the cycle through coordinate valence linking it to another functional group containing nitrogen, oxygen or sulfur.

But, in order to fulfill the aim of disactivating or depressing the gangue by removal of the free or adsorbed metallic ions acting as actual or potential activators according to the present invention, the formed iner complexes or chelate compounds with said cations have to be water soluble or hydrophilic.

Thus, the present inven'tion'discloses the use of organic compounds capable of forming definite s0luble,0r hydrophilic inner complexes with metallic ions insolution or adsorbed on the mineral particles, and thereby preventing such ions from exerting an .activating influence on the gangue.

These chelating compounds may be classified by the nature and the relative position of the two functional groups, of. which one is supplying the primary valence and the other the secondary valence in the formation of the chelate ring, i. e., by the reactive groupings. (Ref. H. M. Haendler and B. P. Geyer, J. Am. Chem- Soc. 60, 2813-1938.)

The object of this invention is a class of chelating compounds having an enolic or phenolic hy droxyl group supplying the primary valence by replacement of its hydrogen, and a (ketonic or ,quinonic) carbonyl group supplying the secondary valence in the formation of the chelate ring:

2 aceaacc Structural characteristics Example Salt forming 1 m Chelste forming organic Corresponding cyclic inner group 22%;? Ram group 3 compound complex Phenolic Carbonyl 1.2dlhydroxy enthraqulnone Iron complex hydroxyl (quinonic) CCC= o 0 -OH A (SH H OH Enolio Carbonyl Enolized dicetoncs Enollzed form of ocotylace- Aluminum complex hydroxyl tone --OH C= H H H -C=(gC- HrC-C=Z-CCH; GHr-C--C-CH:

()H g H A1a In addition to these general conditions required to form a cyclic chelate compound, the latter must be water soluble or hydrophilic in order to fulfill the desired purpose. The structural features promoting water solubility or hydrophilic character for an organic compound are not yet completely understood (Refer, in H. Gilman, Organic Chemistry," John Wiley and Sons, Inc., New York, N. Y., 1938, the chapter: "Constitution and physical properties oi. organic compounds by Wallace R. Brode and John A. Leermakers).

In the following examples of soluble or hydrophilic inner-complexes, the features imparting water afiinity are pointed out in addition to the chelate-forming structure:

dicetones and aromatic m hydroiw-quinones or cetones) are especially valuable as selective flotation modifiers tor ores carrying iron or related metals. The reactive groupings of these compounds have the general formulas:

Example of- Structural features Organic compound yielding Corresponding cyclic solu- Belt Complex R solubleorh dro hiliccheble or I: c o hilc inn r r i frmi Hydmphm gmup lates y p complex y r p l a $13 2mg gmupmg or 68mm Allzarin (1.2 dihydroxyan- I; Y

thraqulnone) 0H C=0 -C -C= 0H (3) and C=0 0 (a) H I! .Acetylacetone v lit i -on c= -c=c-c Bhortcerbonchain HaCC=G-?CH: HiC-C=C-C-CHI $11 H it Kojic acid Fe'----O -on c=o =c-c- Alcoimlichydroxyl 0 II A ll I H "f HO-C 52H H!\ /!l-CH;OH

HG C-CHzOH 0 Among the reactive groupings yielding inner complexes (by combining in the proper relative position the salt-forming and complex-forming functions), the soluble or hydrophilic alpha. and

.r l additional solubility promoting hydroxyl-, carbonylor amino-group.

The following compounds are illustrative examples ,of the class of reagents which are the beta hydroxy-carbonyl compounds (enolized 1.3 subject oi this invention:

Examples of- Structural features Organic a or B hydroxycarsalt- Complex bonyl compound yleidlng Corresponding cyclic inner Reactive Hydrophiiic group soluble or hydrophiiic checomplex gi 123 grouping or feature lates E 9 E D Aoetyiaoetonflenol) J: 2 carbon chains OH -O=0 C= C- attached toiunc- H H H tionai groups. :C- I z t H C ('3 OH HO O C OH H Ai'--- Isatiue O OH C=0 =CC -N= c=0 EX on L0H L4,. 1', ll

Kojicacid OH O=O =CG-- OH (alcohol) on g E i @1301: OH E H 4 aaeasee Examples oi- Structural features Organic or ii dro cari bon lzcmpcunfi i l di Corresponding cyclic inner gg gaggi g Reactive Hydrophilic group while or hydrcp lo checomplex group group grouping or feature lilarin I A OH C= -C-(LC OH,-C=O

0 0 g II n C I no I i O H 0 0H 3 A l It is evident that expensive laboratory prod- Example I ucts like rhodizonic acid (synthesis ref. G. Gutzeit Helv. Chem. Acta XII, 4 p. 725-727, 1929), which are selling for $10 per 1.0 gram, are economically unfit as flotation reagents. From a practical point of view (and unless cheaper procedures of manufacture are developed in the future) the polyhydroxyanthraquinones and polyhydroxynaphtoquinones' with one phenol group in a (or 1) position to the quinonic oxygen atom, produced on a large scale as dyestuif intermediates or as dyes, are most suitable. They are generally marketed under trade names which do not disclose their chemical character:

Ghemical name (anthmquincne formula) 5 E 4 Examples of some trade names of 1-polyhydroxyquincnes .2. .sltfitrahydroxyanthraquincne These quinones yield colored chelate compound which are hydrophilic in alkaline medium and soluble in acid medium.

The proper procedure for flotation of oxide ores following this invention is to add at flrst the organic gangue depressant, in amounts of 0.02-0.05 kg. per metric ton of ore; either as a, slurry in water, or better in a saturated alkaline solution (sodium carbonate or caustic soda), and to condition (agitate) for several minutes. The pulp is then made alkaline, or if possible acid (generally with H2504), to a pH which varies with the nature of the ore, but should be below 4 if the gangue is mainly quartz. Hydrofluosllicic acid or sodium hydrofluosilicate is added as a dispersant (peptizer). For the flotation proper higher aliphatic alcohol sulfate or fatty acid sulfonates, with or without addition of a fatty acid, are used as collectors. A frother and/or mineral oil may be required to control the foam.

The following examples will further illustrate how the said invention may be carried out in practice, but the invention is not restricted to these examples.

A Norwegian iron ore (Dunderland) consisting mainly of crystalline hematite and magnetite with silica and biotite gangue was treated in a magnetic separator at 35 mesh to remove the magnetite, after which operation the product run 19% Fe. It was then ground to mesh and conditioned by addition of the following reagents:

Allzarin paste 20% 0.03 kg. per ton Condit. 10 min. Sulfuric acid 3.0 kg. 60 B./ton Condit. 5 min. Sodium silicofiuoride. 0.3 kgJt Do.

Emulsion (10% duodecylsulfate, 20% sulfonated castor oil, 10% oleic acid, 60% water) 2.0 kgJt.

Concentrates assafying 61.2% Fe were. obtained with an iron recovery 0 79.4%.

Example I! Table tailings from Stillwater chromite ore (Anaconda concentrator), representing 69.1% of the crude, with a gangue of heavy basic silicates.(enstatite, bronzite, diops'ide, olivine, etc.) assaying 6.38% CrzOa, were retabled after grinding to -35 mesh, yielding a secondary concentrate with 37.56% CrzOa (13.56% recov.) and middlings with 19.01% ClzOa (37.12% recov.).

3rd concentrate. Tail 1st concentratm 2nd concentrate Cale. heads The tailings were scavenged under the same conditions, yielding a secondary concentrate with 14.92% CrzOa (38.23% rec.), a middling with 8.42% CraOa (rec. 23.63%) and final tails with 3.72% (rec. 38.13%). I

Example III 'A black sand" from Egypt, containing zircon (about 35%), ilmenite i and magnetite (about 30%), monazi'te (10%) quartz and garnet (25%) was floated as follows:

Example IV A Swedish magnetite ore with 23% Fe was floated, using acetylacetone as the organic depressing agent for the silica gangue. The pH was 3.8, and hydrofiuosilicic acid was used as the dispersant. The only collector was Texapon, a high aliphatic alcohol sulfate. Concentrates with 67.3% Fe were produced, at a recovery of 88.7%.

These examples show that the use, according 2 to the present invention, of organic reagents accomplishing the purpose of gangue depression,

through complexing detrimental cations into a water soluble or hydrophilic chelate compound constitutes a marked advance in the art of froth flotation, ing the selectivity of the collectors, thus improving the grade of concentrates and the recovery.

What is claimed is:

1. In the concentration by froth flotation of oxides of the heavy metals containing iron oxide as a significant constituent of the mineral to be concentrated and a siliceous gangue, said materials being substantially free fromcarbonaceous matter, using as a collector an aliphatic compound selected from the class of fatty acids, fatty alcohols, sulfated fatty acids, and sulfated alco hols, containing at least 9 carbon atoms in their molecules, and carrying out the flotation at a pH below 6, the step of adding first to the pulp a small amount of a non-collecting organic compound having one of the following schematic wherein OH stands for a group consisting of phenolic and enolic hydroxyl groups, C= rep-- resents ketonic and quinonic carbonyl groups and R represents alkyl, alicyclic and aromatic radicals; said radicals, if aliphatic, having from one to four carbon atoms and said radicals, if aromatic, containing a solubilizing group included in the group consisting of hydroxyl, carbonyl and amino; this organic compound being adapted to react with the gangue activating caand is highly advantageous in im-provtions of the pulp to yield a water soluble or hydrophilic chelate compound having the schematic where Me stands for a metal atom (monovalent) replacing the hydrogen of the hydroxyl group by electron exchange and linked to the carbonyl oxygen by the coordinative bond.

2. In the concentration by froth flotation of oxides of the heavy metals containing iron oxide as a significant constituent of the mineral to be concentrated and a siliceous gangue, said materials being substantially freefrom carbonaceous matter, using as a collector an aliphatic com pound selected from the class of fatty acids, fatty alcohols, sulfated fatty acids, and sulfated alcohols, containing at least 9 carbon atoms in their 0 molecules, and carrying out the flotation at a pH below 6, the step of adding first to the pulp a small amount of a non-collecting organic compound having one of the following schematic formulas where OH stands for a phenolic hydroxyl group, C= O stands for a quinonic carbonyl group and R stands for an aromatic radical containing a solubilizing group included in the group consisthydroxy benzoquinone.

where alpha where the depressing organic compound is a basic polyhydroxy-anthraquinone, with one of the hydroxy! Groups in alpha position.

GREGOIRE GUTZEIT.

alpha.