' Patented Febi22,1944 2,342,277 '

UNITED STATES PATENT 0FFlCE_ ‘ 234.2211

SEPARATION OF PYRITE, ARSENOPYRITE, AND PYRRHOTITE BY FLOTATION - - ,

Earl G. Herkenho?, Stamford, Conn., assignor to American Cyanamid- Company, New York N. Y” a corporation of Maine ,

No Drawing. Application February 2, 1943, Serial No. 474,491

(‘01. 209-167) 4 Claims.

This invention relates to a process of separat ing pyrite from arsenopyrite and/or from pyr-i

' rhotite by froth ?otation. Many sul?de ores contain mixtures of pyrite "

and arsenopyrite and in some cases mixtures of . pyrite, arsenopyrite and pyrrhotite. It is desir able to obtain concentrates of the minerals sep arately because of the different uses to which the minerals may be put. Thus, for example, if ~pyrite is to be burned to sulfadioxide for the production of sulfuric acid by the contact process the pres ence of arsenic is undesirable and pyrite contain ing considerable amounts of arsenopyrite is not suitable for this purpose. The mixed ores may in \some cases contain precious metal values, par ticularly gold or silver, and it is common in such cases for the precious metals to be primarily as sociated with the arsenopyrite. Inasmuch as the precious metal content of such ores frequently represents a considerable portion of the values

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it is important to obtain a concentrate which con tains a large portion of the arsenopyrite.

It has been proposed in the past to depress one or other of the minerals by the addition of agents such as lime )r sodium cyanide. These proce dures do result in some separation but the sep aration is not sharp and leaves much to be de sired. '

According to'the present invention froth ?ota-I " tion is effected after conditioning with a small amount of a permanganate such as sodium or potassium permanganate.v The permanganate depresses the arsenopyrite and pyrrhotite, where as pyrite is but little affected and can thereafter be recovered as a concentrate by froth ?otation. In the case of ores containing onlypyrite and ‘arsenopyrite this procedure results in a. satisfac tory practical procem. _

It has further been found that the depressing

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action of the permanganate is not the same for‘ arsenopyrite and pyrrhotite, the pyrrhotite be ing more readily depressed than the arsenopyrite'. It is, therefore, possible to effect a separation of the three minerals by ?rst conditioning with a smaller amount of permanganate which is suf ?cient to- substantially depress pyrrhotite with out depressing any considerable portions of ar senopyrite. Froth ?otation will then result in

producing a concentrate containing pyrite and arsenopyrite which can then be conditioned with larger amounts of permanganate and again ?oat ed to produce a pyrite concentrate. The amount of. permanganate used will, of

course, vary with the nature of the ore and with the relative contents of arsenopyrite and pyrrho tite. In general a satisfactory depression of ar s'enopyrite is obtainable with, amounts of per manganate of the order of a quarter of a pound per ton or less. Selective depression of pyrrho tite without depressing arsenopyrite will ordi narily require amounts of permanganate less than 0.05 pound per ton. "

It is an advantage of the present invention that the ?otation operation on the conditioned pulp is not-critical and the normal sul?de ?otation re agents may be used such as xanthates, dithio phosphates, mercapto-benzothiazoles, and the like. While ordinary sul?de reagents may be used, they differ somewhat in e?fectiveness, and I have found that the best results are obtained with dithiophosphoric acids, dithiophosphates, or mixtures of dithiophosphates with mercaptc benzothiazole and reagents of this type are pre ferred. The invention will be described in greater de

tail in conjunction with the following speci?c ex amples. The parts are by weight.

EXAMPLE 1

An ore containing pyrite, arsenopyrite and pyr rhotite, associated with a gangue which also con tained iron and sulfur, was treated for high arsenopyrite recovery. The arsenic content rep resented the major value or the ore under present economic conditions. The ore was ?rst subjected to a bulk sul?de ?otation with stage oiling using dicresyldithiophosphoric acid and sodium iso-’

V propyl xanthate as promoters. The concentrate

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was then conditioned with 0.02 lb. ofpotassium permanganate and ?oated in two stages using a small. additional amount of the dicresyldithio phosphoric acid. The purpose of the ?otation was to produce a nvrite-arsenopyrite concentrate with a maximum rejection of the pyrrhotite. The sequence. of conditioning and amounts of ‘ re.

2 agents, together with metallurgical results, ap pear in the following two tables:

Conditions and reagents

2,842,277 benzothlazole '- dlsecondarybutyldithiophoshate reagent. ' , ,

Conditions Reagents, pounds per ton

Point at addition Time, minutes NBICOI AF 15 343

Condition ______________ ..

D

00nd. eoneentrate._..:: Cl. ?otation ..... -'_ ____ __

I .The promoters are referred to by tradedesig Metallurgical results nation. "AF 15” is dicresyldithiophosphoric acid diluted withcresols. "343” is sodium'isopropyl 20 Per Assays xantha'te- _ Product cent (git.

Metallurgical results Weight is

Assays‘ good).--" ’ 1034511: 8.5; Product Weight - 26 ii'col’éfii::::::'"""'::::::::::::::::::::::::: 1:13 18:10

As Fe S 01. Tall. - 3.59 0. 37 Rgh.Tail ................................ __ 94.71 0 015 Comb. Cone _______________________________ _.i-. 1.70 12.77

Per cent Percent Percent Rgh. Cone ....................................... ._ 5.29 4.36 1 . 0.24 15.95 3.28 ‘

g '15'653 353 3523 so‘ It illb t th t h‘ h d ' r . - - -- ~ w eapparen- a a 1g egree 0 con

Rgh'Ta? """""""""" " 9M7 M06 “'22 1'62 centration of arsenopyrite was obtained, 84 to 1,

It will be apparent that a very effective depres sion of pyrrhotite took place and a major por tion of ‘the. arsenic was recovered in a relatively high grade arsenopyrlte-pyrite concentrate. 'When the same procedure was carried out but the potassium permanganate conditioning omit ted the cleaner concentrate contained only 4.56% of arsenic and but little rejection of pyrrhotite took place.

' - EXAMPLE 2 \

An ore similar in nature to that of Example 1 was subjected to the same type of treatment as described in Example 1, but the cleaner concen trate was then further conditioned with addi tional potassium permanganate and subjected to a third ?otation. The additional permanganate which acted as‘ a depressant required further addition of collectors and frothers, the additional collector being a mixture of the sodium salts of mercaptobenzothiazole and disecondarybutyldi thiophosphoric acid. The ?otation procedure an; arsenic assays- appear in the following ta les:

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0

and the pyrite concentration was even higher, amounting to 196 to 1. A blank test which followed the same sequence

but omitted the potassium permanganate con ditioning gave an arsenopyrite concentrate hav ing only 1.17% of arsenic, more than 92% of the arsenopyrite remaining in the pyrite concentrate.

Flotation operations in the examples were car ried out under standard conditions using Fager gren ?otation machines and operating conditions such as air and the like were the same for both. blank tests and those using permanganate condi tioning. b '

In the examples potassium permanganate has been described because of its ready availability. sodium permanganate gives the same result and in‘large scale use presents some economies. '

I claim: ' - .

1. A method of separating pyrite from arseno pyrite which comprises subjecting a mixture con taining both to conditioning with a su?iclent alkali metal permanganate to depress the ar'seno pyrite and subjecting the conditioned material to froth ?otation in the presence of a promoter for

Conditions and reagents

Conditions n Reagents, pounds per ton

Point of additions > . ' v ' > > .

m'fg?lfés Pgucggt pH cuso. mic 0. AF 15 34s KMn04 P. o 404

3 0- 50 4.0 g. v - 0.111 p 0. 05

i ........ .. _. 0. 015 .................. ..

'2 0. 039 10 ~ \ 0. 06

00nd. 01. 00110. 1 - 0. 054 0.03 Py. ?otation ...................... .. 3

‘10.02 added at 5 minutes.

The promoters are referred to by trade desig nation. “AF 15” is a dicresyldithiophosphoric acid diluted withcresols. “343" is sodium iso propyl xanthate. “P. 0.” stands for pine oil and

pyrite, whereby a concentrate is obtained rich in pyrite and a tailing rich in ars'enopyrite.

2. A method of separating pyrite,‘ arsenopyrite and pyrrhotite which comprises subjecting a mix;

“404" for an undiluted mixed sodium mercapto- 75 ture containing the three minerals to condition

ing with a small vamount of an alkali metal per manganate sumcient to depress the pyrrhotite - but insu?icient to substantially depress the arsen opyrite, subjecting the conditioned material to froth ?otation in the presence of a sul?de pro- . moter whereby a concentrate is produced rich in pyrite and arsenopyrite and the tailing containing most of the pyrrhotite, conditioning the concen trate with an additional amount of alkali metal permanganate su?icient to depress the arseno pyrite and subjecting the conditioned material to ,froth ?otation in the presence oi’ a sul?de col

10 acid radical. '

l I 2,342,217 , \ 3

iector whereby a concentrate is produced rich in 1 Pyrite and a‘ tailing containing the‘arsenopyrlte.

3. A method according .to claim 1 m which the froth ?otation takes place in the presence of a collector" containing the dithiophosphoric acid

' 4. A method according to claim 2 in which both ?otation operations are re?ected in the presence oi’ a collector containing the dithiophosphoric

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