US2593431A - Reagent conditioning for electrostatic separation of minerals - Google Patents

Description

Patented Apr. 22, 1952 REAGENT CONDITIONING FOR. ELECTED- STATIC SEPARATION OF MINERALS Foster Fraas, Riverdale, Md;, assignor' to the" United States of America as represented by the Secretary of the Department or the Interior No Drawing. Application January 16, 1942i, Serial No. 2,800

(Granted under the act of March 3, 1883', as amended April30, 1928; 370 O; G. 757) 2 Claims.

The invention described herein maybe manufactured-and used by or for the Government of the United States for governmental purposes withoutthe payment to me of any royalty thereon in accordance with the provisions of the act of April 30, 1928 (Ch. 460, 45 Stat. L. 467-).

This invention relates to the electrostatic separation of minerals. It particularly relates to the conditioning of mineral surfaces torender the" various minerals more amenable to electrostatic separation. Still more particularly the invention relates to' conditioning mineral composites with anionic reagents and then subjecti'ng'the treated composite to electrostatic separation.

Refractory type minerals (i. e., those not easily susceptible to chemical attack) when in combination, such as kyanite zircon', yield but slightly to electrostatic separation. Such separations are improved if the crushed mineral composite is deslimed or cleaned by dedusting or by moderate agitation with water. Theintroduction of acids such as hydrofluoric and sulfuric acids to the water during the desliming improves electrostatic separation somewhat; however, the degree of improvement frequently is not suflicient to War-' rant independent commercial application of the acids alone.

Accordingly, it is an object of this invention to provide a method whereby the surfaces of reiractory mineral-composites are conditioned with anionic reagents and the composite thereby rendered more amenable to electrostatic separation. Other objects and advantageswill. be apparent and in part hereinafter appear. 7

These objects and advantages are accomplished in accordance-with the invention by heating and drying, a ground and deslimed mineral composite, thereafter treating said hot dry composite with a selective surface conditioning reagent, and then subjecting the conditioned composite to electrostatic separation whereby the selectively con-'- ditioned constituent is rendered more or less susceptible to the influence of an electrical poten-- tial differential than the unconditioned constituent; and thereby rendering. said composite more 2 been found to be greatly improved by surface conditioning treatment in accordance with this invention.

In the present process the heating and drying of the mineral composite can be suitably accomplished by any heating and drying meansg'e'ns. erallyadapted to such operations.

Suitable surface conditioning reagents for urposes of this invention include organic compounds which exhibit anionic and cationic characteristics. The presently preferred anionic conditloning agents are those having the following general structural formula:

R(-CO0H)n wherein R is a normal, branched or cyclic h'y' drocarbon appendage, and n' is any wholenum ber consistent'with the nature of R. Such sub-' stances include normal aliphatic acids such as heptylic acid, propionic acid, acetic acid; mixed coconut fatty acids, crotonic acid, oleic acid'arid' the like; dibasic acids such as fumaric acid 'an'd' the like; aryl acids such as? benzoic' acid, the naphthenic acids, salicyclic acid, phthalic acid, cresylic acid, and the like; and other organic compounds having acid properties and a hydrocarbon appendage of sufficient'length. Although cresylic acid has a hydroxyl group insteadof a carboxyl, the hydro'xyl group attached to an aryl appendage exhibits acid properties.

In operation the mineral composite is first crushed to a degree whichwill substantially liberate the various mineral constituents from one another. This can be accomplished by any siiitable materials disintegrating means. The ground material is thereafter mixed with water or other suitable suspending medium to form a pulp containing? about 50 to "per cent solids and then deslimed. The desliming' can be accomplished by treating the pulp with about 0105 to 50' pounds of at least'one mineral acid per ton of composite in the pulp. Mineral acids suchas hydrochloric, hydrofluoric, nitric, phosphoric, sulfuric, sulfurous and the like have been found to be satisfactory: for this purpose. Mixtures of hydrofluoric acidor' fluoride salts with other acids, such. as sulfuricghavealso been found to be-efiective in this connection. When such mixtures are em ployed a-"few' tenths of a pound of the'hydrofluoric aoid'or fluoride and lto 50 pounds of sulfuric acid is" generally sufficient.

The time for this initial desiinfingand; surface cleaning treatment is not critical and will vary greatly with the nature of the mineral, the degree of fineness of the crushed composite, the rate of agitation and other such factors. About one-half an hour has generally been found to be sufiicient for agitation. The liquid phase is thereafter removed from the treated solids by suitable solid-liquid separating means such as sedimentation and decantation, filtration, centrifuging, and the like. Thereafter the deslimed composite is preferably washed with sufiicient water to remove any liquids which may be entrapped. in the mass. The dewatered composite is then dried. Any suitable method can be employed to dry the mineral composite. Merely *heating or passing hot dry air through the mass has been found to dry the material satisfactorily.

Thereafter to each ton of the hot dry material about 0.05 to pounds of an anionic reagent is added and intimately mixed therewith. The temperature of this conditioning treatment will vary somewhat with the reagent employed and the mineral being treated. In general temperatures between about 50 to 300 degrees centigrade, or temperatures sufilcient to volatilize the reagent have been found satisfactory. The reagent can be added as a solid, liquid or gas. Some anionic reagents such as benzoic acid are sufilciently volatile so that they can be added in pure state without any danger of adding an excessive amount or of failing to get a uniform distribution of the reagent throughout the composite. Other less volatile reagents, such as the coconut fatty acids, can be added as solutions in suitable volatile solvents such as carbon tetrachloride, gasoline, kerosene, and the like, in order to achieve a greater control of the amount of reagent added and a greater uniformity of dispersion. The conditioning treatment can be accomplished by any of the many well known processes for intimately and uniformly blending small amounts of materials with larger amounts of crushed solid materials. For example, the hot dry material can be tumbled with the reagent for a sumcient time to insure a substantially uniform dispersion or contacting of the reagent and the material being treated. Thereafter the thus treated composite is immediately passed through an electrostatic separation.

The following examples will show more specifically how the invention may be carried out but it is not limited thereto.

' EXAMPLE I A ground kyanite-zircon composite was moderately agitated with four pounds of hydrofluoric acid'per ton, in a 60 to '70 per cent solids pulp. The desliming liquid was removed by sedimentation'and decantation. This was followed by washing the deslimed material several times with water and then dewatering by sedimentation and decantation. The material was dried by heating and agitating the mass; the hot dry material was then at the stage for the anionic reagent treatment. To separate batches of the hot dry deslimed composite anionic reagents were added and intimate- 1y.blended by rolling and stirring the mixture. The reagents were added in a concentration equivalent to three pounds of reagent per ton of composite. The thus treated material was immediately passed through a single stage roll-type separator having a non-ionizing negative electrode adjacent to the roll. A partial summary of the results is given in Table I below. The defiectant is the fraction attracted toward the electrode, while the residue remains close to the roll.

TABLE I Efiect of various reagents on the kyamte-ztrcon separattcm Zircon, per cent Test Weight No Treatment Product Percent Fraction Assay of Total defiectant. 27 56 32 1.-.. None residue... 73 43 68 composite. 47 100 deflectant- 28 66 63 2--.. Benzoicacid residue... 72 15 37 composite. 100 29 100 deflectant. 23 75 74 3..-. Salicylicacid residue... 77 8 26 composite. 100 20 100 4.--. Phthalic deflectant. 26 48 65 Anhydride residue-... 74 9 35 composite. 100 19 100 defleetant. 14 75 24 6---. Oxalicacid residue... 86 40 76 composite. 100 45 100 defiectant. 34 77 93 6.... Hoptylicacid.- residue... 66 3 7 composite. 100 28 100 dcfiectant. 30 74 (i9 7---. Cresylic acid {residue.-.. 70 14 31 composite. 100 32 100 From these results it can be seen that an improvement can be obtained by treatment with anionic reagents in general. The data also shows that oxalic acid, unlike the other reagents in having no hydrocarbon appendage, does not ive any appreciable improvement in separation.

This process of conditioning with anionic reagents was extended to other combinations of minerals. The same conditioning process was used but the electrostatic separation was more elaborate, the separator had six stages instead of one as in Example I. The first three stages had negative electrodes with the non-deflectant passed through successive stages to yield a tailing. The defiectant from each of the three stages was combined as heads for the second three stages. The second three stages had positive electrodes with the non-defiectant passed through successive stages to yield the concentrate. The deflectant from each of the three stages yields a middling fraction which may in some cases contain a third mineral component which is electrically conduc tive.

EXAMPLE II A sillimanite-quartz composite was deslimed as in Example I. Some portions of the deslimedcomposite were not treated with any anionic reagent; and used as controls. Other portions were anionically conditioned as in Example I. The materials were then subjected to electrostatic separation. The collected portions were assayed by a sink and float procedure in acetyline tetra- This shows an improvement in both grade and recovery by the use of benzoic acid as the conditioning reagent. Other anionic reagents had a similar effect.

5 EXAMPLE III TABLE III E 7 2015 beneoic acid on a icyomite-quartz separation Tailing Size Analysis Per cent Kyanite Tail- Weight Per cent ing Composition Treatment 10+14 14+20 10|14 l4+20 mesh mesh mesh mcsh Noncnh; 27 9.3 4.1 13.2 Benzoic acid 3. 7 0, 5 3. 7 10. 2

In addition to improving the recovery of the kyanite, the benzoic acid enables the processing of coarser-sized material. It also counteracts sensitivity to high humidityweather conditions.

From the above description and examples, it is apparent that a definite improvement in the electrostatic separation of refractory mineral composites is obtained by the conditioning of the mineral surfaces with anionic reagents.

While the invention is particularly described in connection with a conditioning treatment with anionic reagents such as benzoic acid, phthalic acid, heptylic acid and the like, it is not limited thereto, certain basic reagents such as the amines also function in a similar manner.

Since many widely diifering embodiments of the invention will occur to one skilled in the art, the invention is not limited to the specific details illustrated and described, and various changes may bemade therein without departing from the spirit and scope thereof.

What is claimed is:

1. In a process'for the electrostatic separation of the liberated and deslimed constituents of a mineral composite of a type resistant to chemical attack and of the class consisting of lryanitezircon, sillimanite-quartz, and kyanite-quartz, which involves electrostatic separation of the composite constituents, the steps prior to said separation which comprise heating and drying said composite and then treating said hot dry composite with about 0.05 to 5 pounds of an organic anionic conditioning agent per ton of composite, said conditioning agent being a carboxylic acid having a hydrocarbon appendage, whereby at least one of said composite constituents is selectively filmed with said conditioning agent and said composite constituents are thereby rendered more amenable to electrostatic separation.

2. The process of claim 1 wherein the anionic conditioning agent is of the group of compounds having the formula R(COOH)n wherein: R is a normal, branched, or cyclic hydrocarbon appendage and n is any whole number consistent with the chemical nature of R. FOSTER FRAAS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Fraas and Ralston, Electrostatic Separations of Solid, Industrial and Engineering Chemistry, vol. 32, No. 5, pages 600 to 644.

Claims (1)

1. IN A PROCESS FOR THE ELECTROSTATIC SEPARATION OF THE LIBERATED AND DESLIMED CONSTITUENTS OF A MINERAL COMPOSITE OF A TYPE RESISTANT TO CHEMICAL ATTACK AND OF THE CLASS CONSISTING OF KYANITEZIRCON, SILLIMANITE-QUARTZ, AND KYANITE-QUARTZ, WHICH INVOLVES ELECTROSTATIC SEPARATION OF THE COMPOSITE CONSTITUENTS, THE STEPS PRIOR TO SAID SEPARATION WHICH COMPRISE HEATING AND DRYING SAID COMPOSITE AND THEN TREATING SAID HOT DRY COMPOSITE WITH ABOUT 0.05 TO 5 POUNDS OF AN ORGANIC ANIONIC CONDITIONING AGENT PER TON OF COMPOSITE, SAID CONDITIONING AGENT BEING A CARBOXYLIC ACID HAVING A HYDROCARBON APPENDAGE, WHEREBY AT LEAST ONE OF SAID COMPOSITE CONSITITUENTS IS SELECTIVELY FILMED WITH SAID CONDITIONING AGENT AND SAID COMPOSITE CONSTITUTENTS ARE THEREBY RENDERED MORE AMENABLE TO ELECTROSTATIC SEPARATION.