A Study of Several Chelate-Forming Compounds as Collectors for Various Copper Minerals

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A STUDY OF SEVERAL CHELATE-FORMING COMPOUNDS AS COLLECTORS FOR VARIOUS COPPER MINERALS

by DOUGLAS W. FUERSTENAU

22 0 0 3

A Thesis Submitted-to the Department- of MineraD 'Dressing in Partial Fulfillment of the Requirements for the Degree of Master of Science in Mineral Dressing Engineering

MONTANA SCHOOL OF MINES Butte, Montana June 1, 1950 [BBRARY- MONTANA u. u i l . ^BUII^MONIANA

UMI Number: EP33270

All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent on the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion.

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TABLE OF CONTENTS INTRODUCTION Introduction

1

Collectors Used for Flotation of Copper Minerals

2

The Chelate Compounds

5

The Mechanism of Attachment of Chelate-type Collectors • .

9

HISTORICAL p

Previous Studies with Chelate Compounds as Collectors

. . 13

EXPERIMENTAL WORK Reasrent Preparation

14

The Contact Angle Apparatus

15

The Selection and Preparation of Mineral Specimens . . . .

17

Experimental Procedure in Determination of Contact Angles. 18 Bubble Stabilization Tests

19

Tests with Rhodanlne

20

Tests with Dlphenylthiocarbazone (Dithizone)

21

Tests with Salicylaldoxime

23

Tests with 8-Hydroxyquinoline (Oxine)

24

Tests with Cupferron

25

Tests with Neo-cupferron

26

Tests with Phenyl thiourea (Phenylthiocarbamide)

27

Tests with Dinitrosoresorcinol

28

Tests with Dlmethylglyoxime

29

Tests with Acetoacetanllid

30

Tests with Sodium Diethyldlthiocarbamate

31

Tests with Phenylthiohydantoic Acid

32

g^j^lgggj^^iAgsdig-ail

y

Tests with Phenylthiohydantolc Acid

32

Tests-with Phenyl thiosemicarbazide

33

Tests with Diethylenetriamlne

34

Tests with Acetylacetone (Pentanedione-2,4)

35

Tests with Dithiooxamide

36

Flotation Tests with Dlphenylthiocarbazone

36

Flotation Tests with Phenylthiosemicarbazide

38

Flotation of Cuprite Ore Using Phenylthiosemicarbazide . . 39 Flotation of Cuprite from Columbia Gardens Ore

39

Summary of Experimental Data

40

CONCLUSIONS

43

RECOMMENDATIONS

44

BIBLIOGRAPHY

45

FIGURES 1.

Contact Angle vs pH Using Rhodanine

20A

2.

Contact Angle vs pH Using Diphenylthiocarbazone

22A

3.

Contact Angle vs pH Using Phenyl thiourea

27A

4.

Contact Angle vs pH Using Sodium Diethyldithiocarhamate . 31A

t.

Contact Angle vs pH Using Phenyl thlohydantoic Acid. . . . 32A

6.

Contact Angle vs pH Using Phenylthiosemicarbazide . . . . 33A

7.

Contact Angle vs pH Using Diethylenetriamine

34A

TABLES.

1.

Bubble S t a b i l i z a t i o n Tests

20

2.

C o n t a c t Angle S t u d i e s of S e v e r a l C h e l a t e - f o r m i n g Reagents w i t h Copper Minerals a t Room Temperature

21A 21B

3.

Reagent Additiona in the Flotation Test with Dithizone. . 37

4.

Flotation Results with Dithizone

37

5.

Flotation Results with Phenylthiosemicarbazide

38

6.

F l o t a t i o n R e s u l t s w i t h Columbia Gardens Ore

40

ILLUSTRATIONS 1.

The C o n t a c t Angle Apparatus

16

A STUDY OF SEVERAL CHELATE-FORMING COMPOUNDS AS COLLECTORS FOR VARIOUS COPPER MINERALS INTRODUCTION Chelate-forming organic compounds offer an interesting and relatively unexplored source for possible flotation reagents.

The need for reagents having specific collective

properties for certain mineral species is especially apparent in many separations in which the flotation process is applicable . Outstanding among the difficult separation problems is the recovery of the so-called oxidized copper ores. Consequently, this Investigation is essentially a study of chelate-forming compounds as possible flotation collectors for copper minerals. While the chelate compounds have been considered, little definitive experimental evidence has been gathered to evaluate thoroughly the possibilies of these organic compounds.

The'experimental approach employed in this

Investigation is quite different from the methods considered heretofore, 1. e., the reagents were first tested by use of a contact angle measuring apparatus for the initial evaluation of their surface active characteristics; and then on the basis of the evidence obtained, systematic-' flotation tests were made. It is believed that s 26.

N e o - c u p f e r r o n was t e s t e d by Doherty

over t h e pH range

from 5.4 t o 8 . 6 and was t e s t e d i n t h i s i n v e s t i g a t i o n a t a. pH of 4 . 1 .

C h r y s o c o l l a showed no c o n t a c t angle w i t h n e o - c u p f e r r o n .

C o v e l l i t e , m e l a c o n i t e , and n a t i v e copper e x h i b i t e d s m a l l c o n t a c t s of 1 8 , 2 0 , and 2 1 d e g r e e s r e s p e c t i v e l y . d e g r e e s was o b t a i n e d w i t h c u p r i t e .

A f a i r c o n t a c t of 3 6 . 5

A z u r i t e and m a l a c h i t e gave

c o n t a c t s of 4 5 . 5 and 43 d e g r e e s r e s p e c t i v e l y .

With n e o - c u p f e r r o n

c h a l c o p y r i t e showed t h e g r e a t e s t a n g l e of c o n t a c t , a n angle of A

54 d e g r e e s .

E t h y l a l c o h o l was used as t h e s o l v e n t f o r

the

reagent. T h i s r e a g e n t m e r i t s i n v e s t i g a t i o n o n l y as a c o l l e c t o r

for

c h a l c o p y r i t e and p o s s i b l y f o r t h e c a r b o n a t e m i n e r a l s . T e s t s w i t h Phenyl t h i o u r e a ( P h e n y l t h l o c a r b a m l d e ) . t h i o u r e a r e a c t s w i t h mercury, s i l v e r ,

Phenyl-

copper, g o l d , p l a t i n u m ,

and p a l l a d i u m t o g i v e i n n e r complexes: i n the f o l l o w i n g manner: /V

H

S ||

HI

/ V - N — C—NH

++

+ £Cu——*-

U

.

H

I T ^

3 ||

°

I l ^ £Cu-1•NH

The r e a g e n t was d i s s o l v e d i n e t h y l a l c o h o l a t aa c o n c e n t r a t i o n of 6 . 2 5 mg p e r c c . thiourea per

The c o l l e c t o r s o l u t i o n c o n t a i n e d 25 mg p h e n y l -

liter.

No c o n t a c t s were o b t a i n e d w i t h c h r y s o c o l l a .

M a l a c h i t e gave

no c o n t a c t s w i t h p h e n y l t h i o u r e a w i t h t h e e x c e p t i o n of a s l i g h t c o n t a c t a t a pH of 8 . 0 .

From a pH of 5 . 0 t o 8 . 0 a z u r i t e gave

e x t r e m e l y s m a l l c o n t a c t s w i t h t h e maximum being 22 d e g r e e s a t a pH of 7 . 0 .

(See Table 2)

I n t h i s s o l u t i o n c u p r i t e showed

r a t h e r l a r g e c o n t a c t a n g l e s over t h e e n t i r e pH r a n g e t e s t e d , 27.

-

I.e.

^

3 /

^w

1k

A

2

6

/"

3

7 /

^

1 6

• S

1 2 5 MG

REAGENT PER

LITER SOLUTION

>

TEMPERATURE 22 — 25-C 0

I

2

3

4

5

6

7

8

9

10

II

PH

FIGURE 3-

CONTACT ANGLE VS PH FOR THE FOLLOWING MINERALS WITH PHENYLTHIOUREA .

I AZURITE

4

CUPRITE

2 CHALCOPYRITE

5

MALACHITE

3 COVELLITE 7 NATIVE

6 MELACONITE COPPER

from pH 5.0 to 10.9. A maximum contact of 62.5 degrees was observed at a pH of 7.0. Melaconite exhibited contact angles over the pH range of 5.0 to 9.0 with the maximum contact being 48 degrees at a pH of 9.0.

Native copper gave contacts over

the entire pH range with its maximum contact being 50.5 degrees at a pH of 10.9. The sulfide minerals showed good contacts with phenylthiourea.

Covellite gave contacts over the entire pH

range tested with the maximum contact being 55.5 degrees at a pH of 5.0.

Chalcopyrite showed contacts from pH 5.0 to 9.0

with the maximum contact being 57.5 degrees at a pH of 9.0. The results of these tests indicate that phenylthiourea might be a good collector for

chalcopyrite, covellite, cuprite,

melaconite, and native copper at a pH between 8 and 9. The reagent is ineffective as a collector for the carbonate minerals and for chrysocolla.

Phenylthiourea might prove to be a good

collector for the copper precipitates in the leach-precipitation process for oxidized copper ores. Tests with Dinitrosoresorcinol.

Nitrosonaphthol and other

aromatic o-nitrosophenols react in their tautomeric isonitrosooxime forms with cobalt, ferric, copper, uranyl, and palladium ions to give insoluble colored compounts}3 The mechanism of the reaction for the formation of the copper complex with nitrosonaphthol Is the following: NO

0=|H

CO'

0H_ ^ V > 0

0=N—|Cu

*CU-

l^VM

The reaction with dinitrosoresorcinol should be similar with the possibility being increased because of two groups on the benzene ring. 28.

The reagent was tested at a pH of 7.0 with all the minerals, but no contacts were obtained with any of the minerals. Tests with Dimethylglyoxime.

Dimethylglyoxime has been

A

used in analytical chemistry for the determination of many different ions because of its ability to form inner-complex salts with such metals as nickel, palladium, platinum, cobalt, ferrous, and copper salts.

The formation of the inner complexes of metals

with dimethylglyoxime takes place readily because of the alphadioxlme group, which readily forms the chelate ring.

The inner-

complex compound is formed in the following manner: H3C—C-HS

H,C2 H,C—C—N.

T

+ icuH )H

3

'

u L .^>° C—C=^ "OH

For the tests the reagent was dissolved in ethyl alcohol. The concentration of reagent in the collector solution was 25 mg per liter. 7.1.

The reagent was tested over the pH range of 4.0 to

No contacts were obtained with chrysocolla, covellite, and

native copper with dimethylglyoxime (See Table 2 ) . A single contact of 37 degrees was observed at a pH of 5.3 with cuprite, and a single contact of 27 degreeB was observed at a pH of 4.0 with melaconite.

Azurite showed contacts over the pH range of

7.1 to 4.0 with the maximum contact being 44.5 dgrees at a pH of 4.0.

Malachite exhibited a sinsrle contact of 46.5 degrees at a

29.

pH of 4.0. Chalcopyrite' gave contacts at a pH of 5.3 and 4.0 with the maximum being 57 degrees at the pH of 4,0, The few contacts which dimethylglyoxime gave with the copper minerals indicated that its use as a collector for the copper minerals is limited. Tests with Acetoacetanilld. This compound has a structural formula which may be altered by tautomerism to allow it to form chelate complexes with metal ionsi8 The formation of the enol form of the compound and its chelation may be showed in the following manner: / \-N-j-c-C-CH* J ^ N—f H u uH " "

H 0 ( S-N-C-C-C-CH_ \—f ^—' JHJ uH ? 3

0

0

>- < VH-C=»C—C-CH-. f 5 H \> f HH w

The reagent was dissolved in ethyl alcohol. The concentration of reagent in the collector solution was 25 mg per liter. The pH range tested was 5,6 to 9.0. None of the minerals gave contacts at the pH of 7,0, Chrysocolla, malachite, and melaconite showed no contacts at any of the pH values tested. Azurite showed a contact of 45.5 degrees at a pH of 9.0. Cuprite exhibited a contact of 42 degrees at a pH of 9.0 and a contact of 50 degrees at a pH of 5.6. Contact angles of 41 and 50 degrees were noted for chalcopyrite at a pH of 5.6 and 9.0 respectively. Contact angles of 41 and 46 degrees were observed for covellite at a pH of 5.6 and 9.0 respectively. Native copper showed a contact of 36,5 degrees at a pH of 5,6 and a contact of 46 degrees at a pH of 9.0. The contact angles obtained with acetoacetanilld are interesting in that no contact was obtained at the neutral pH but 30.

contacts were obtained in both the acid and alkaline pH ranges. Tests with Sodium Diethyldlthiocarbamate.

Sodium diethy1-

dithiocarbamate reacts with bismuth, cadmium, copper, ferric, ferrous, lead, manganese, stannous, and zinc ions to give complex 9 precipitates, which are soluble In carbon tetrachloride. The formation of the complex takes place in the following manner: ^C—3-Na ^

H5C2—N

^

^ 0 + £Cu

>-

S

H_C^—N»-4Cu

K%

V5 The reagent was dissolved In water.

The concentration of

the reagent in the collector solution was 25 mg per liter. The pH range which was tested varied from 4.4 to 10.3. A fine yellowish-brown colored stain formed on the surface of malachite at a pH of 10.3. Chrysocolla showed no contacts over the entire pH range tested.

Native copper gave contact angles over the pH range of

5.6 to 10.3 with the maximum contact being 58 degrees at a pH of 7.7 (See Table 2 ) . The carbonate, sulfide, and oxide minerals exhibited contact angles over the entire pH range. A maximum contact of 51*5 degrees was noted at a pH of 7.1 for azurite, and a maximum contact of 52 degrees was noted for malachite at the pH of 7.1.

The two oxide minerals, cuprite and melaconite,

showed maximum contact angles of 56.6 and 47 degrees at a pH of 7.1 and 4.4 respectively.

The maximum contact for chalcopyrite

was 61 degreeB at a pH of 4.4, and the maximum contact for covellite was 57 degrees at a pH of 8.8. The results which were obtained using sodium die thy1-

•

•

-

2V

^4

4

5

6

C^

^7

X .1 ^v

^x 5 2 '

^

\e

• -

2 5 MG LITER

REAGENT

PER

SOLUTION

TEMPERATURE 22—26«C O

I

6

9

10

II

PH

FIGURE 4 —CONTACT ANGLE VS PH FOR THE FOLLOWING MINERALS WITH SODIUM DIETHYLDITHIOCARBAMATE 1 AZURITE 2 CHALCOPYRITE 3 COVELLITE 7 NATIVE

4 CUPRITE 5 MALACHITE 6 MELACONITE COPPER "*T A

dlthiocarbamate as the c o l l e c t o r with the contact angle apparatus i n d i c a t e d t h a t t h i s compound may be e f f e c t i v e as a c o l l e c t o r i n the bulk f l o t a t i o n of the copper minerals with the exception of chrysocolla.

I t was i n t e r e s t i n g to note t h a t t h i s reagent gave

good c o n t a c t angles over the e n t i r e pH range tested i n t h i s i n v e s t i g a t i o n , i . e . from a pH of 4.4 to 10.3Teats with Phenyl thlohydantoic Acid.

The formation of the

inner complex s a l t between copper ions and phenylthiohydantoic acid t a k e s place i n the following manner: C^-OH

-N—C—N—CHp H I H s

Y\

+£Cu*

*-

£CU-O—-cr

I J—N—C—CH 2 ^^ H I s

Because of the insolubility of this reagent in ethyl alcohol and water, it was dissolved in monoethanolamlne. The reagent was tested with the copper minerals from a pH of 4.9 to 11.1. Chrysocolla showed no contacts over the entire pH range tested. 4.9.

Native copper gave a contact of 36 degrees at a pH of

The two carbonate minerals exhibited contact angles from a

pH of 4.9 to 9.1.

The maximum contact with azurite was 45 degrees

at a pH of 7.0, and the maximum contact with malachite was 48.5 degrees at a pH of 4.5.

Cuprite gave a fair contact of 41.5

degrees at a pH of 4.9 with small contacts of 26 and 22 degrees at a pH of 7.0 and 9.1 (See Table 2 ) . Melaconite gave contacts over the entire pH range with the maximum contact being 43.5 degrees at a pH of 11.1. A maximum contact of 49 degrees was obtained at a pH of 4.9 with chalcopyrite.

32.

The contact angle had

r"

3> «

s"

A

V

V

/

2 , ^

/

\

-3 6

Si 65 I'

/

•

70

\ ' -

-

•

^1

'

•4

•

-

-

^2

25 "

"

— '• '

MG REIAGEN1r PEFI LITER SOLUTION TEMPERATURE 2 2— 26* C

0

I

6

7

8

9

10

II

PH

FIGURE 5-

CONTACT ANGLE VS PH FOR MINERALS 1 2 3

WITH

THE FOLLOWING

PH ENYLTHIOHYDANTOIC

AZURITE CHALCOPYRITE COVELLITE 7 NATIVE COPPER -— _ _»_ ^^ ^2A .

4 5 6

CUPRITE MALACHITE MELACONITE

ACID

decreased to 16 degrees by a pH of 9 . 1 .

C o v e l l i t e gave good

c o n t a c t s from a pH of 4.9 to 11.1 with the maximum contact being 62.5 degrees a t a pH of 4 . 9 . The small values of the contact angles f o r the d i f f e r e n t copper m i n e r a l s , with the exception of c o v e l l i t e , indicated t h a t the use of phenylthlohydantoic acid would be l i m i t e d . Tests with Phenylthiosemicarbazide.

This reagent can form

an i n n e r complex with m e t a l l i c ions i n the following manner:

a

S

H

H

I

H

N

N

C

NH

^ +^Cu

>v »-

H

H

[J dJ f

1—N

N

C=

-NH

The reagent was dissolved in hot ethyl alcohol to give a

stock solution containing 6.25 mg phenylthiosemicarbazide per cc. The reagent was tested with the different copper minerals from a pH of 5.0 to 11.2. Contact Angles were obtained with chrysocolla from a pH of 5.0 to 10.3 with the maximum contact being 48 degrees at a pH of 7.0. .The average contact with chrysocolla was somewhat over 30 degreea. Native copper showed good contact angles over the entire pH range tested with a maximum contact of 61 degrees being noted at a pH of 7.0 and 8.0 (See Table 2 ) . The carbonate minerals exhibited contact angles at some of the pH values. Azurite gave a maximum contact of 68.5 degrees at a pH of 10.3* Malachite showed a maximum contact of 53.5 degrees at a pH of 11.2 and a contact of 53 degrees at a pH of 8.0. The two oxide copper minerals showed contact angleB from a pH of 5*0 to 11.2. A maximum contact of 64 degrees was noted at a pH of 10.3 with cuprite.

The maximum contact which was obtained for

melaconite was 58 degrees at a pH of 11.1 with a nearly equiva33.

*

\ ^1 5

/8 /7 4 2

V 6 V^ >

v

' J

,-

'

1

*»4

7 8 '

6