Table Of ContentTHE INFLUENCE OF TEMPERATURE ON THE ADSORPTION OF
POTASSIUM ETHYL XAITTHATE AT SULFIDE
LIIIIERAL SURFACES
by
Wilbur J. Guay
A Thesis .
Submitted to the Department of Mineral Dressing
in Partial Fulfillment of the
Requirements for,the Degree of
Master of Science iu^Mmsral, Dressing Engineering
' '-' 22 7 24 * "•' •
MONT-iN-a SCHOOL OF IiIiJES
Butte, Montana
June 8, 1951 •
'jteB«RY» MONTANA .
i^fiujj^ MONTANM
\
a
UMI Number: EP33284
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TABLE OF CCiTTElTTS
INTRODUCTION 1
HISTORY 1
PiiHT I - THE DECOL-u.-;ITIOK OF POTASSIUM ETHYL XAITTPUTE 3
Introduction 4
History 4
Experimental Procedure and Results 9
The w;uantitativ:e Determination of Xanthate 9
Experimental Results 10
Discussion of Results 12
Conclusions 14
Recommendations for Future Investigations 14
PART II - THE INFLUENCE OF TEIiPE-^TURE ON THE FLOTATION OF
GALENA USING PCT^SSILl: ETLYL XANTH..TE AS COLLECTOR . 16
Introduction .17
History • 18
Experimental Procedure and Results 23
Preparing the Galena 23
Flotation Procedure 24
Experimental Data 27
Summary of Experimental Results 29
Conclusions 31
Recommendations 32
PART III - THE INFLUENCE OF TEMPERATURE ON THE ADSORPTION OF
POTASSIUM ETHYL XAITTKATE ON S.'h .LERITE 37
Introduction 38
History 38
Principles of Activation 38
The Effect of Alkalis Upon the Adsorption by
Activated Sphalerite.. .*. 39
The Effect of Zinc Sulfate Upon Adsorption by
Sphalerite. ". 39
t/
The Effect of Cyanide Upon Adsorption by Sphalerite 40
The Joint Effect of Cyanide ano ~Zinc Su.lfe.te Upon
Adsorption by Sphalerite 41
The Joint Effect of Cyanide, Alkalis, and Copper
Sulfate at Sphalerite Surfaces.,. ...... 42
Description of the Equipment 45
Conclusions 48
Recommendations 48
BIBLIOGRAPHY 52
LIST OF ILLI3TR«TI0i.S
PLATES
Page
Plate 1. Viev: of Laooratory and Equipment 46
Plate 2. Layout of laooratory - Plan Viev? 47
FIGURES
Ficmre 1. Recoverv Graph of Galena 33
Figure 2. Recovery Graph of Galena 34
Figure 3. Recovery Graph of Galena 35
Figure 4. Recovery Graph of Galena 36
Figure 5. Contact Curves for activated Sphalerite,
Showing the Influence of Cyanide 42
TABLES
Table 1. Decomposition of x'otassiun. Ethyl Xanthate 11
THE INFLUENCE OF TEM-SH^T'URE ON THE ADSORPTION OF
POTASSIUM ETHYL XANTH^TE AT SULFIDE MINERAL SURFACES
INTRODUCTION
A study of the available literature will ouickiy reveal the
fact that the amount of fund mental knowledge of the effect of
temperature upon adsorption o.t the liruid-solid interface is very
sca,rce. In order to increase this knowledge a program of research
has been underway in the Mineral Dressing Laboratories for some
three years. The investigations described herein axe a continua
tion of these studies.
HISTORY
The rather limited recbgnization of the role of temperature
in flotation has been discussed and studied by Ba.rson ** and
Apian •"• in their work in the Mineral Dressing Laboratories at
the Montana School of Mines. Also, the theories of adsorption,
and the applicability of the contact angle method to the deter
mination of adsorption has been very well presented by these in
dividuals. The progress up to this point has been the determina
tion of the adsorption of potassium ethyl xanthate by galena at
temperatures of 18 , 32 , 40 , and 50 C. In the course of these
studies, it was deemed advisable to investigate the effect of
temperature upon the stability of potassium etnyl xa.ntnate, and
. •, • * « . ..
to attempt a correlation between the contact angle deta obtained
. .' . . . . . .. •* •• • •* >'.
and actual flotation'practicei^Abdbfdi'ugly, separate investiga
tions of these two'phases of the problem were undertaken by the
writer. These investigations comprise Part I and Part II, respec
tively, of this work.
- 1 -
During the course of the contact an ie VJOTK, the need for
&
continuous pH and temperature indicating instrumentation became
increasingly apparent . Previously, the procedure used involved
taking a pH reading with a Beckman -oH meter at the beginning and
at the end of a run. The mean of these readings WHS taken as the
pH at which the test was conductec. It was determined that r>H
values could vary as much as three or four-tenths of a pH unit
during this time; especially at pH values above 8.0. Since the
variation in pH values is greater at higher temperatures, the
difficulty of assigning pH values to these observations can read-
ily be seen. Tne method of determining pH was too time consuming
in addition. A drop in temperature occured while measuring the pH.
This also affected the assigned value. The desirability of instru
mentation which would give instantaneous readings of pH and tem
perature while photographing the bubble is readily apparent.
Due to the philanthropy of the Research Corporation, a grant
was made available to the Department of Mineral Dressing of the
Montana School of Mines, making the installation of this equipment
possible. The design of a complete new laboratory to be used in
the pursuit of this investigation was undertaken as a result of
this grant. A study of the effect of temperature upon the adsorp
tion of potassium ethyl xanthate on sphalerite is contemplated as
the next step in this series of investigations. This study, toge
ther with a brief description of the new laboratory and instrumen
tation will comprise Part III of this tnesis.
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:PART I
THE DECOMPOSITION OF POTASSIUM ETHYL X.aiTHATE
- 3 -
INTRODUCTION
In any given situation the amount of adsorption of surface
active reagent which takes place will be governed directly by the
amount of surface active ion which is present in the liquid phase.
The possibility that the use of higher temperatures would result
in the decomposition of potassium ethyl xanthate, and hence in
fluence the contact angle data, has to be taken into consideration.
Accordingly, a series of tests were made at various pH values and
at different temperatures to determine what this effect would be
under conditions contemplated in the pursuit of these studies.
HISTORY
A thorough search of the literature revealed the fact that the
mechanism of the decomposition of alkali xanthates is not very well
understood, or at least not very well agreed upon. Several reac
tions have teen proposed for the decomposition of xanthic acid and
its alkaline salts. One of the most popular of these is that poin-
12
ted out by Von Halban and Kirsch and others who say that alkali
xanthates do decompose when acidified to give carbon disulfide and
alcohol, but it has been found that the pH must be less than 5 and
the temperature above # C for this to happen. The reaction,
C H 0CSS" +- H+ »-CS2 + O2H5OH (1)
2 5
The products carbon disulfide and ethyl alcohol have definitely
been identified. It is also known that the decomposition is cata-
40
lyzed by hydrogen ions. Wark and Cox say that acids rapidly
destroy bubble contact in xanthate solutions, provided that the
32
pH value is approaching unity. Taylor ancLJKnoll say, "In an al-
32
kaline solution according to Ragg , there is an extensive decom-
- 4 -
position of xanthate ion when judged by the composition of the
insoluble cuprous salts which precipitate from the decomposed
solutions, and which are probably in the main, thiocarbonates.
This alkalinity* is beyond that reached in any of the present
experiments (maximum of 9.8 ), and again beyond that in usual
flotation practice.w
Taylor and Knoll 3* list the following reactions as being
most likely tnose by which xanthates may decompose:
0 H 0CSS~ -H H+-^-CS2 +- C3H5OH (l)
2 5
(C H 0CSS) Na + NaOH >-(OCSS) Na -*-C H 0H (2)
2 5 2 2 5
(C H50CSS) Na-h2NaOH ^(OCSO) Na2 + NaSH +• C H 0H (3)
2 2 5
(C H 0CSS) Na+NaSH ^-(SCSS) Na2+-C2H50H (4)
2 5
(C H 0CSS) Na+HOH *- CS -H C H 0H -V Na+ -+- OH" (5)
2 5 2 2 5
4(C H 0CSS) Na-h2H 0-)-0 —^2(C HRO-C -S- S • S • C • SOC2H5)+40H" (6)
2 5 2 2 2
XDixanthogen)
It was their experience in the laboratory that the only commonly
met decompositions are those taking place around the neutral point;
namely, those recorded in'equations (5} and (6). The determinations
made to prove this statement were as follows:
1. Iodometric titration will detect changes in equations (l)
and (5), since only the xanthate consumes iodine.
2. The determination of pH colorimetrically would indicate
any reaction giving hydroxyl ion, either directly as in equations
(l) and (6), or indirectly.
3. The color of the precipitate, on adding lead ion is wnite
for lead xanthate; for thiocarbonates, brown; and for sulfide,
black. The tests with Pb+ showed a white precipitate in every
case, thus eliminating Ecuations 2, 3 and 4. They conclude that
•IN NaOH - pH of 14 - 5 -
the principal reaction is probably the one of oxidation to di-
r.anthogen'- Equation 6.
In studying the ripening mechanism of viscose, W. Klauditz 18
believed that in aqueous solution the following reaction took
place slowly;
6C H50C3SK+3H 0 "-^2K CS -t-K C0 +6C H 0H + 3CS2 (7 J
2 2 2 3 2 3 2 5
while in strong alkaline solutions a reaction of another type
took place:
C H 0CSSK-+5K0H —>-2K2S +K C03+C H 0H+2H 0 (8)
2 5 2 2 5 2
Klauditz identified the products K S and K CS3. On the basis of
2 2
these findings, he was lead to believe that the older concepts
of xanthate decomposition were incorrect.
Ragg ° has indicated that xanthates hydrolyze to carbonates
on boiling with water, especially in the presence of hydroxyl ion.
Equations (7) and (8) might be used to explain this, or it may be
due to the hydrolysis of carbon disulfide:
CS -t-40ir—^C0 ~-f- 2H3"+H 0 (9)
2 3 2
A presentation of a possible mechanism for the formation of the
caroonate is given in. a previous report . In addition to the pre
viously listed reactions, another source **5 presents the following
reaction:
2(C H 0CSS) Na + 2H 0 —^(SCSS) Na -HROH4-H2S +-CO2 (10)
2 5 2 2
Dewey ^ makes the statement that in addition to the compounds
indicated by enuations (l) to (6) and (lOJ, it can be shown by
shifting equilibria, some seven mono-, seven di-, and three tri-
thiocarbonates, comprising all the alkyl, alkali, and alkyl-alkali
tniocarbonates, can be prepared from a given xanthate. Mercaptan
can also be prepared. Lae.ksa 1S reports that during decomposition
- 6 -
