US2293470A - Froth flotation of siliceous material - Google Patents

Description

Patented Aug. 18, 1942 FROTH FLOTATION F SILICEOUS MATERIAL Barry L. Mead and Ernest J. Maust, Brewster,

Fla., assignors to American Cyanamid Company, New York, N. TL, a corporation of Maine No Drawing. Application March 7, 1940, Serial No. 322,771

11 Claims. (Cl. 209-166) The present invention relates to froth flotation processes for the removal of acidic siliceous gangue from ores containing it.

Attempts have been made in the past to beneficiate ores, particularly non-metallic ores, containing siliceous gangue by froth flotation of the siliceous portion using promoters especially prepared for this purpose. These promoters are in general compounds having a positively charged surface active portion and are usually referred to as cationic reagents. Typical reagents of this type are quaternary ammonium compounds such as those described in the Lenher U. S. Patent No. 2,132,902, for example Cetyl trimethylammonium bromide or chloride Lauryl trimethyl ammonium chloride or iodide Cetyl pyridinium bromide Dimethylbenzyl phenyl ammonium chloride sulfonatedin benzyl ring Beta diethyl amino ethyl oleyl amide acetate Beta diethyl amino ethyl oleyl amide hydrochloride Trimethyl ammonium methyl sulfate or amino oleyl ethylene diamine Quaternary ammonium compounds containing at least one aliphatic chain with at least eight and 'not more than twenty carbon atoms in the molecule Water-soluble or acid solution soluble compounds of amino cellulose such as chitosan acetate Trimethyl octadecyl ammonium bromide Trimethyl eicosyl ammonium iodide Octadecyl pyridinium bromide Trimethyl octadecyl ammonium chloride Trimethyl dodecyl ammonium bromide Trimethyl dodecyl ammonium iodide Octadecyl beta hydroxyethyl morpholinium bromide Cetyl beta hydroxyethyl morpholinium bromide Triethyl Octadecyl ammonium bromide Triethyl cetyl ammonium bromide Beta stearamidophenyl trimethylammonium methyl sulfate Octadecyl pyridinium chloride Octadecyl pyridinium iodide Octadecyl alpha picolinium bromide Octadecyl quinolinium bromide Dodecyl pyridinium bromide Heptadecylamino hydrochloride Hexadecylamine hydrochloride Dodecylamine hydrochloride and the primary and secondary aliphatic amines having long hydrocarbon chains attached to the Patent No. 2,168,840 such as monoand di-hexyl, octyl and decyl amines and their water-soluble salts and mixed amines butyl dodecyl amine, butyl octadecyl amine and the like.

- The procedure proposed hitherto using cationic promoters for the flotation of silica give good results with ores which are slime-free and which do not produce slime readily. However, when slime is present, or when the ore readily produces slime, the effect upon flotation of silica is markedly deleterious even upon the use of excessive and prohibitive amounts of the cationic reagent with the result that the flotation of the silica is very incomplete resulting in obtaining a non-floatable product that is unmarketable and noneconomical due to the silica it contains.

The most important field of silica flotation at the present time is presented by the Florida pebble phosphate deposits in which finely divided siliceous gangue is intimately associated with the finely divided phosphatic particles, both contained in a matrix wherein the bonding material is made up of phosphatic and aluminous clay. However, up to the present time the use of cationic reagents to effect a silica flotation has not been commercially feasible with phosphatic ores due to the fact that excessive reagent costs resulted or else if the amount of reagent were reduced within commercial limits, the silica removal is not sufliciently complete to produce a high grade phosphate product. The copending applications Serial No. 320,121, filed February 21, 1940, and Serial No. 325,011, filed March 20, 1940, have described a process of silica flotation in which the ore, such as for example, a pebble phosphate ore, is subjected to an extraordinarily complete desliming procedure removing the last trace of existing slime. These procedures have greatly improved the silica removal but encountered difliculties when applied to materials such as certain phosphate rocks which have relatively soft surfaces and which under the conditioning treatment normally preceding froth flotation, tend to disintegrate on the surface to form a small amount of colloidal and semi-colloidal slime. This slime, which is of the material which is not to be floated, appears to be still more deleterious in its effect on silica flotation than the native or original slime which is largely of an aluminous silicate nature, and a very small proportion of this phosphatic slime will exert a greater effect than a corresponding proportion of ordinary argillaceous slime.

According to the present invention we have nitrogen such as those described in Amour U. S. found that if a thoroughly deslimed ore is admitted directly to the flotation cell from its deslimlng operation in a thoroughly deslimed condition that silica can be floated from this ore economically if the reagents are added directly In the above table we show that increasing amounts of silica are left behind in the nonfloatable portion as the time of asitation is increased and that alter 30 seconds of agitation to the flotation cell and both the silica froth and 5 a non-economical phosphate product is obtained the non-floatable portion are removed from the from the particular ore treated due to the large cell immediately before the non-floatable portion amount of silica leit with it.

is allowed to produce a slime. In ordinary flota- 1 The present invention is' not intended to be tion the ore is generally conditioned in the preslimited to any particular theory of action. We ence of the reagent bef the flotation operation believe that the rapidity with which the cation is performed. In the use of the cationic reagents active promoter floats silica apparently is due for the flotation of silica this normal ndi i nat least in part to the fact that the action of the ing process proves to be detrimental to the flotapromoter takes place immediately and leaves no tion operation in that he slime Produced f unchanged promoter in the pulp because if an the non-floatable portion so effects the cationic excess of promoter is used, and t excess reagent that the silica is inadequately floated, covered from the water associated with the pulp, resulting in an inferior non-floated product @011- this excess does not have the same activity. talninl; an excessive amount of silica. After the An example of a flotation test wherein we silica has been removed from the no added a great excess of cationic reagent and and s im producing material the silica then may attempted to float the silica in a second charge, be removed to a cleaning Operation t0 using the residue solution from the first charge, quent handling or flotation steps without in- 1 shown in Table 2,.

'iurious effect as the principal source of slime pro- T M duction has been removed. Such a silica froth e 2 is then found to be quil'g1 stable shofivingma de- Sm Tamng cide tendenc for flocc a on of t e s ceous particles in the? absence of slime. Feed 2:1 :85 Cationic The flotation of silica with the cationic reagent is so rapid anidaghe elicit; of slime1 1217283685 gmmzgs mg)" l 80 3X 1 t from the non-floa le pc on so e e ous norms amoun that we prefer to remove the silica completely 501 80mm above only i g fiig figzzggg g k 3: g fi ggg fg ig g The results set out in the above table are easily explained on the above theory that the cationic in fact cationic reagents generally, are rapid in te 1 h 1 their promoter action, and in accordance with promo re Its w 0 6 p051 Y charge idly to the silica. and then retains no further 1 the present invention we have found that 1mth t b d proved metallurgical results are obtained with charge so that e l amino recovere them if the time during which the ore is and reused. It is practically 1mposs1ble to dejected to froth notation is less than 20 seconds termme what goes on at the instant of flotation The normal agitation and attrition produced 40 but the above theory explams the factors set in the ordinary type of mechanical or pneumatic out above easflv and we o o k ow or a y fl tation cell produces a n amount of slime other theory of action which would explain the from the non-floatable portion of the ore so that results- Nevertheless t is P s e t other the more rapidly the non-floatable portion is factor m y be present nd for his r son the removed from the zone of agitation and attrition theory of action is advanced only as a probable the more economically the silica can be floated e p n i n Wi t l mi ing the invention therewith smaller amounts of reagent. to.

The rapidity with which the sflica floats is a Broadly the present invention is not limited to further feature of the present invention and the use of any p rti ar cationic p m r 88 permits the use of a single cell or a relatively we have found that the interference of slime with small number 01 cells in place of a large string, silica flotation appears to be a general characthereby reducing equipment and power costs. To teristic of cationic reagents. In addition to the show the rapidity with which slime is formed by effect of slime which is the primary feature of agitation within a flotation cell and its eflect the present invention, the prevention of conupon the flotation of silica we show the followtinued contact of the cationic reagent with the ing table wherein a phosphatic ore of the Florida flotation material both before and in the course pebble phosphate type is violently agitated with of flotation has a secondary advantage with a cationic active flotation reagent, dioctyl aminecertain cationic reagents of the aliphatic amine Table 1 Feed Non-float- 'Iafl- 23; 1 Reagents, B R L BeIBleL' Q1515. BI P F L' Rate Recov Eh-Md 52 235;

27.68 76.56 4.30 1.89 290 on .18 None 21.13 76.87 4.30 1.35 ass 90.9 .18 5

21.12 76.54 5.35 1.55 2.81 one .13

Th term none in the above table means that ype, which reagents are very sensitive to chemiair was admitted simultaneously with the start cal changes induced by the presence of air and of agitation, i. e., there was no conditioning f water which are probably oxidizing and carbonthe flotation feed before aeration. 7 ating phenomena although the exact nature has notbeendetern iined. Inthecaseofcationic reagents which are sensitive to air and water,

the present invention has the further advantage that no deterioration due to this cause can-take place as theperiod of contact between reagent. air, water and ore is almost instantaneous. The deleterious eifect of agitation and aeration of the ore with water and a cationic active flotation reagent, dioctyl amine is shown below in Table 3. 10

The data in the above table shows that di Table 3 Silica Seconds Non-float- Tail- Feed bk in oonosn- Rmo My Reagents. agitated n. P. L l mu lbs./t. feed and B. P. L- 1w]. B. P L at 28. 21 77. 41 4. 05 2. 12 2. 99 95. 18 None 27. 96 76.16 B. so 1. 57 2.79 96. 3 .18 5 28. 31 74.99 6.8) 1.89 2.77 95.6 .18 B. 12 74. 64 7. 0o 1. 46 2. 74 96. 9 18 15 28. 40 71.78 11. 10 1. 67 Out Out 18 Z) 27. 66 63. 04 2). 86 1. 14 Out Out 18 The term none in the above table means that air was admitted simultaneously with the start of agitation and the silica float. and phosphate tailing separated immediately, the froth being removed as quickly as it is physically possible.

octyl amine is stable unless in contact with air or slime.

25 The data in the following table show the effect of slime on the flotation of silica from phosphate rock using dioctyl amine as the flotation agent.

This is an added advantage of the present invention when sensitive cationic reagents are employed and is a feature which is included in a more restricted aspect of the invention.

A comparison of results in Tables 1 and 3 shows that the ore pulp and reagent can be agitated violently for 20 seconds before any deleterious results show up, whereas even 5 seconds of aeration start to show loss of reagent strength.

To show the effect of time alone on the stability of dioctyl amine, an emulsion of the amine It will be noted that even with one pound per ton of slime, or .044%, that the flotation is substantially killed. Even by adding a prohibitive amount of reagent it is impossible to float silica in the presence of slime. These examples show concretely the necessity of floating the silica at once before the flotation cell has time to make slime.

The data in the following table show the eflect of increasing the amounts of amine reagent on the flotation of silica.

Table 6 Concentrate Reagent Frother 3.9% ffi i Ratio Reoov. 1bs./t. lbs/t.

B. P. L. Insol.

30. 96 33. 49 67. 05 5. 18 No stable froth 04 .05 31.05 54. 49 31. 50 3. 34 N o stable froth .09 12 31. 49 69. 52 12. 2. 71 No stable froth l3 17 31. 33 75. 43 5. 55 1.92 No stable froth l8 24 31. 66 77. 57 3. 2. 38 2. 57 95. 4 22 29 31. 63 78.11 2. 50 2. 16 2. 58 95. 7 .27 .36 32. 24 77. 79 2. 65 3. 04 2. 56 94. 3 .31 41 31. 93 79.30 2. 40 3. 56 2. 67 93. 0 36 48 31. 71 78. 75 2.05 4. 21 2. 71 91. 6 40 53 31. 43 79. 08 2.15 4. 87 2. 79 90. 2 45 N representing a 40:1 mixture of dioctyl, amine solvent and water was prepared. A portion of the fresh emulsion representing .18 lbs/ton of ore was used immediately, to produce a silica float from a phosphate ore by adding directly to the ore pulp during the flotation. A second portion of the emulsified amine was left standing in a closed container for 18 hours and an .18 lb./ton emulsion used in the same manner to produce a silica float.

The data is found in the following table.

65 The above tests were made with a typical cation 7 that it is not necessary to the present invention to use ionizable compounds as similar results are obtained with amines and with their ionized salts, provided satisfactory dispersion and distribution is effected. The present invention is 75 therefore not intended to be limited in any way to the use of a cation active promoter which is actually an ionizable compound. The interaction between the surface of the silica and the basic portion of the promoter does not appear to be tied up exclusively withthe presence of actual ions. The theory advanced in the Lenher patent referred to above does not appear to be correct as applied to silica flotation, or at least it'does not appear to be a necessary factor in the present invention. For while Lenher is quite correct that all of the materials which he describes in his patent and which are ionized are usable as silica promoters, and show improved results when used in accordance with the procedure which forms the subject of the present invention, the improved results obtainable are not limited to these materials but the amines themselves which are in many cases not water-soluble and are not accordingly ionized, behave in precisely the same way. We do not wish to advance any definite theory of action in silica flotation and the present invention is not intended to be limited to any particular theory of the Lenher patent.

From the foregoing examples it will be apparent to those skilled in the art that the flotation of silica can be accomplished almost instantly by the improved process of the present invention, that fewer flotation cells can be employed to produce -a higher grade phosphate product and at the same time use a smaller quantity of flotation reagent.

What we claim is: 1 A process for separating by froth flotation a siliceous gangue from an ore containing a portion which is not readily floatable by promoters for silica flotation and which ore produces additional slime under the ordinary agitation and aeration of a froth flotation cell which comprises desliming the feed, introducing the feed into afroth flotation cell, adding a cationic silica flotation promoter directly to the deslimed ore pulp in the froth flotation cell without preliminary conditioning, effecting froth flotation in said cell, removing therefrom a concentrate relatively rich in siliceous gangue, the time during which the ore pulp is subjected to froth flotation being less than twenty seconds.

2. A process for separating by froth flotation a siliceous gangue from an ore containing aportion which is not readily floatable by promoters for silica flotation and which ore produces additional slime under the ordinary agitation and aeration of a froth flotation cell which comprises desliming the feed, introducing the feed into a froth'flotation cell, adding a cationic silica flotation promoter which is subject to deterioration in contact with air and water directly to the deslimed ore pulp in the froth flotation cell without preliminary conditioning, effecting froth flotation in said cell, removing therefrom a concentrate relatively rich in siliceous gangue, the time during which the ore pulp is subjected to froth flotation being less than twenty seconds.

3. A process for separating by froth flotation a siliceous gangue from phosphate ore which ore produces additional slime under the ordinary agitation and aeration of a froth flotation cell which comprises desliming the feed, introducing the feed into a froth flotation cell, adding a. cationic silica flotation promoter directly to the deslimed ore pulp in the froth flotation cell without preliminary conditioning, effecting froth flotation in said cell, removing therefrom a concentrate relatively rich in siliceous gangue, the time during which the ore pulp is subjected to froth flotation being less than twenty seconds.

4. A process for separating by froth flotation a siliceous gangue from phosphate ore which ore produces additional slime under the ordinary agitation and aeration of a froth flotation cell which comprises desliming the feed, introducing the feed into a froth flotation cell, adding a cationic silica flotation promoter which is subject to deterioration in contact with air and water directly to the deslimed ore pulp in the froth flotation cell without preliminary conditioning, effecting froth flotation in said cell, removing therefrom a concentrate relatively rich in siliceous gangue, the time during which the ore pulp is subjected to froth flotation being less than twenty seconds.

5. A process for separating by froth flotation a siliceous gangue from an ore containing a portion which is not readily floatable by promoters for silica flotation and which ore produces additional slime under the ordinary agitation and aeration of afroth flotation cell which comprises desliming the feed, introducing the feed into a froth flotation cell, adding a cationic amine silica flotation promoter directly to the deslimed ore pulp in the froth flotation cell without preliminary conditioning, effecting froth flotation in said cell,

removing therefrom a concentrate relatively rich in siliceous gangue, the time during which the ore pulp is subjected to froth flotation being less than twenty seconds.

6. A process for separating by froth flotation a siliceous gangue from an ore containing a portion which is not readily floatable by promoters for silica flotation and which ore produces additional slime under the ordinary agitation and aeration of a froth flotation cell which comprises desliming the feed, introducing the feed into a froth flotation cell, adding a silica flotation promoter,

dioctyl amine, directly to the deslimed froth flotation in said cell, removing therefrom a concentrate relatively rich in siliceous gangue, the time during which the ore pulp is subjected to froth flotation being less than twenty seconds.

7. A process for separating by froth flotation a siliceous gangue from an ore containing a portion which is not readily floatable by'promoters for silica flotation and which ore produces additional slime under the ordinary agitation and aeration of a froth flotation cell which comprises desliming the feed, introducing the feed into a froth flotation cell, adding a silica flotation promoter, lauryl amine, directly to the deslimed ore pulp in the froth flotation cell without preliminary conditioning, effecting froth flotation in said cell, removing therefrom a concentrate relatively rich in siliceous gangue, the time during which the ore pulp is subjected to froth flotation being less than twenty seconds.

8. A method according to claim 3 in which the phosphatic ore is Florida pebble phosphate.

9. A method according to claim 4 in which the phosphatic ore is Florida pebble phosphate.

10. A method according to claim 1 in which the flotation is effected in a single rougher cell followed by cleaning of the silica concentrate produced.

11. A method according to claim 3 in which the flotation is effected in a single rougher cell followed by cleaning of the silica concentrate produced.

HARRY L'. MEAD. ERNEST J. MAUST