Contributions to the Metallurgy of Germanium

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PU R D U E UNIVERSITY

THIS IS TO CERTIFY THAT THE THESIS PREPARED UNDER MY SUPERVISION

Stuart T. Ross

BY

e n t it le d

CONTRIBUTIONS TO THE METALLURGY OF GERMANIUM.

COMPLIES WITH THE UNIVERSITY REGULATIONS ON GRADUATION THESES

AND IS APPROVED BY ME AS FULFILLING THIS PART OF THE REQUIREMENTS

FOR THE DEGREE OF

Doctor of Philosophy

‘R O F E S S O H I N C H A R G E O F T H E S I S

H ead of S chool o r D epartm ent

d m

* 2. 2 -

„ S TO

TO THE LIBRARIAN:-----

^ US" THIS THESIS IS NOT TO BE REGARDED AS CONFIDENTIAL.

BHGISTRAB POBM 10—7-4 7— 1M

CONTRIBUTIONS TO THE METALLURGY OF GERMANIUM

A Thesis

Submitted to the Faculty

of

Purdue University

by

Stuart T* Ross

In Partial Fulfillment of the Requirements for the Degree

of

Doctor of Philosophy

June, 1950

ProQuest Number: 27714163

All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is d e p e n d e n t upon the quality of the copy subm itted. In the unlikely e v e n t that the a u thor did not send a c o m p le te m anuscript and there are missing pages, these will be noted. Also, if m aterial had to be rem oved, a n o te will ind ica te the deletion.

uest ProQuest 27714163 Published by ProQuest LLC (2019). C opyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C o d e M icroform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106 - 1346

ACKNOWLEDGMENT

Deep appreciation Is expressed to the Purdue Research Foundation for the aid received in the completion of these investigations.

A profound

personal gratitude is expressed to Dr. J. L. Bray, of the School of Metallurgical Engineering.

His

inspiration and interest have proven of the utmost value during the course of the work described herein.

TABLE OF CONTENTS Page ABSTRACT ...............................................

i

INTRODUCTION...........................................

1

PREPARATION OF ZINC

J4.

ANALYTICAL METHODS

SULFATE LEACH S O L U T I O N S ........... ...............................

8

REPORT OF INVESTIGATION OF METHODS FOR THE REMOVAL OF GERMANIUM FROM LEACH S O L U T I O N S ................... I.

Chelation

.................................

ll|.

II.

Tannic A c i d ...................................

17

III•

Organic Reagents Similar to T a n n i n ..........

2i|.

IV.

Ion Exchange ..................................

26

THE RELATIONSHIP BETWEEN GERMANIUM AND CADMIUM AS ........... IMPURITIES IN ELECTROLYTIC ZINC CELLS

36

C O N C L U S I O N S ......... ... ...............................

55

REFERENCES .............................................

6l

LISTS OF FIGURES AND TABLES List of Figures Figure

Page

le

Pachuca T a n k ..................................

6

2*

tfWorking Curve" ...............................

11

3#

Neutralization Curve .........................

19

4.

Effect of p H ..................................

21

5»

The

Effect of Ge* Concentration .............

29

6*

The

Effect of Agitation Time

33

7#

The

Effect of Zinc Concentration .............

8.

Model Zinc Electrolytic Cell ................

39

9.

Current Efficiency vs. Ge. Concentration «•••

4^

..............

34

List of Tables Table

Page

1*

Ions Present in Washed Complex

.............

22

2#

Ions Present in Dissolved C o m p l e x ...........

22

3*

Results of Resin Ion Exchange

2?

4*

Current Efficiencies ..........

lj.1

5.

Results of Plating Runs

43

6.

Coded D a t a ....................................

ij_5

7e

Sources of V a r i a t i o n .........................

I4.8

8.

Variances and F Values

.......

1|_8

9*

Current Efficiencies

............

51

..............

...................

i

ABSTRACT

The extraction metallurgy of germanium from zinc sul­ fate leach solutions is studied.

Extractions by precipita­

tion with tannin and ion exchange with sodium aluminosilicate are reported.

The germanium-tannin complex is studied with

regard to process limitations *

The commercial adaptability

of ion exchange extraction is investigated.

Spectrograph!c

methods of the determination of germanium are described. Significant interaction is reported between germanium and cadmium in zinc electrolysis cells.

Evidence is presented

of a reversion of cadmium to a soluble form during the zincdusting operation, in the presence of germanium.

Signifi­

cance of difference and analysis of variance techniques are employed to ascertain the importance of the interaction of cadmium and germanium*

1

CONTRIBUTIONS TO THE METALLURGY OF GERMANIUM

INTRODUCTION

With the depletion of high-grade zinc ores adapted to pyro-metallurgical reduction processes, industrial attention has been turned to more abundant low-grade zinc ores of complex natures.

These ores cannot be reduced in the con­

ventional zinc retort.

Their complexity makes hydrometal-

lurgical extraction, followed by electrodeposition, the most feasible process for zinc recovery# Trace amounts of germanium have been found extremely harmful to processes designed for the recovery of zinc from complex ores.

Reduced electrolytic cell efficiencies and

copious evolution of hydrogen during electrodeposition have been ascribed to concentrations of as little as 0*001 gram of germanium per liter of electrolyte.

This thesis is pri­

marily concerned with the extraction metallurgy of germanium from such electrolytes* On a theoretical basis, reduced cell efficiencies are explained as being due to a loss of "overvoltage".

"Over­

voltage" is defined by Koehler (15) as the difference be­ tween the electrode potential in a cell required for the passage of current and its equilibrium value.

If the

equilibrium value Is high enough, metals above hydrogen in the electromotive series will plate on the cell cathode, as

2

is the case of the zinc sulfate electrowinning cell.

This

difference between theoretical cell decomposition voltage and the actual plating voltage is due to a form of polariza­ tion of the cathode, whereby molecular hydrogen is not al­ lowed to evolve at a finite rate. Two theories are advanced concerning this polarization. One proposes that either a layer of metal hydrides or a film of nascent hydrogen cover the cathode upon excitation of the cell.

The other proposes that hydronium ions (H^0+ ) blanket

the cathode during electrolysis.

The reaction rates of

these cathodie layers are said to be infinitely slow, unless disruption of the layers takes place so that the reaction product, molecular hydrogen, can form and be evolved.

Thus

the plating of the metal goes on preferentially to the evo­ lution of hydrogen, unless the "overvoltage" is lowered by disturbing the polarizing cathode layers.

Lowering of the

"overvoltage," of course, causes lowered current efficiency of the metal plating cell, and the final result is evolu­ tion of hydrogen with no metal plate being obtained. The low-acid, double-leach process for the dissolution of zinc from complex ores comprises the hydrometallurgy considered herein.

It is a representative process, and

that which may be applied to it can be applied to most al­ ternative methods without extensive modification.

Precipi­

tates containing small amounts of cadmium, arsenic, anti­ mony and a portion of the germanium dissolved from the ore

3

are obtained during the process*

The bulk of the precipi­

tates are flocoulent aluminum and iron hydroxides®

Separa­

tion of a compound of germanium from these precipitates is not feasible commercially because of their bulk and poor filtering characteristics® The recovery of a relatively pure germanium compound from sulfate leach solution extraction products was a secondary motivation for the research described herein. Germanium metal, per se* has become of some commercial im­ portance*

Its semi-conducting properties have enabled thin

wafers of germanium to replace rectifying tubes in electronic installations where space is at a premium.

Since the demand

for pure and cheap germanium compounds for reduction to the metal has far outstripped the production, by-product prepara­ tion of germanium compounds seemed worthy of investigation® The theories concerned with the mechanism by which germanium is able to reduce the efficiency of zinc electro­ lytic cells are not entirely tenable with certain observed facts.

These facts point toward a definite relationship

between the effecta of germanium and cadmium in the zinc cell.

The investigation of this relationship is reported® In conclusion, certain theorizing is done in an attempt

to correlate seemingly extraneous, and sometimes contra­ dictory, information.

Proof of the validity of this theo­

rizing can be obtained only by further research.

k

PREPARATION OF ZINC SULFATE LEACH SOLUTIONS

The conditions of the commercial low-acid double-leach process for the recovery of zinc from complex sulfide and oxide ores were simulated in the preparation of zinc sul­ fate leach solutions.

Koehler (15) and B ray(5) report that

100 to 130 grams per liter of acid are present, correspond­ ing to an acid leach concentration of approximately 10 per­ cent sulfuric acid.

Essentially, the double leach process

consists of an acid leach cycle of the pulverized and roasted ore, followed by a neutral leach cycle during which the acid leach filtrate is used to leach a fresh batch of ore.

During the neutral leach, the excess of ore buffers

the pH of the leach at 5»0 to 6*5*

This increase in pH

causes precipitation of such impurities as iron, aluminum, silica and some of the arsenic and antimony dissolved dur­ ing the acid leach.

The time of each cyle is about 2^ hours.

The solutions are filtered after each 24-hour leaching op­ eration.

Following the neutral leach, zinc metal dust is

added to the solution to remove copper and cadmium as pre­ cipitates.

A small part of the dissolved germanium is in­

cluded in the neutral leach residue* Both acid leach and neutral leach solutions were pre­ pared from ore which had been received in the roasted con­ dition from the Eagle-Pit cher Company.

The ore was ground

to a mean particle size of 60 mesh and leached in a

5

laboratory scale pachuca tank for 2I4. hours on both the acid and neutral cycles.

The composition of the roasted ore was

approximately 30 percent zinc, 8 percent iron and 3 percent sulfur, as sulfate.

Arsenic and antimony were present on

the order of 0#01 to 0*02 percent.

The balance of the

roasted ore consisted of silicates, aluminates and trace amounts of gold, cadmium, germanium, copper, manganese, and nickel.

Lead, although a major constituent, was not deter­

mined because it is virtually non-reactive as far as the leaching reactions are concerned*

The pachuca tank (Figure

1) was a prototype of the machines used commercially*

The

air-lift principle served to recirculate the ore in the leaching medium, and the operation was of the batch type* Each leaching operation concerned 50 grams of ore and 500 mililiters of leaching solution*

The acid leach used 10

percent sulfuric acid solutions, and the neutral leach solutions were acid leach filtrates.

Filtration was car­

ried out with laboratory filters which employed the air aspiration principle to provide a negative pressure for filtration* It was found by spectrograph!c analysis that neither the acid leach nor the neutral leach solutions possessed enough germanium for experimental purposes.

The concentra­

tion of germanium in these solutions was determined to be less than one part per million.

Consequently, germanium

was added to these solutions so that separatory experiments

6 P f ? C H U C f l

T A N K

o lu i~ /o n / e v e /

' a tr / i f f tube, ^in .d ia .

—

i—

P e r f o r a t e d d/SC

L.

7

could be conducted on a scale which permitted satisfactory analytical processes to be employed.

The germanium con­

centrations of these solutions were raised to approximately 0.1 gram per liter by the addition of an acidified solution of sodium germanate#

8

ANALYTICAL METHODS

The choice of a sensitive and selective method for the determination of germanium must be made from three gen­ eral fields of quantitative analysis:

Gravimetric analysis,

emission spectrographic analysis and absorption spectro­ graph! c analysis• The literature discloses several gravimetric methods for the determination of germanium*

All are based on the

separation of germanium as an insoluble precipitate, fol­ lowed by weighing after a stable form is achieved* gravimetric methods possess a common shortcoming*

The They

lack sensitivity in the concentration range from zero to 50 parts per million.

The solubility product constant ex­

erts too strong an influence in this range for reliability and reproducibility of results. There are two absorption spectrograph!c methods for the determination of germanium described in the literature. The molybdigermanic acid method is described by Kitson and Mellon (l4) •

The color producer is a soluble yellow

heteropoly acid of germanium with sexivalent molybdenum* Alimarin and Iwanoff-Emin (1) report the sensitivity of the color producing reaction to be high enough to permit the determination of as little as one part per million of ger­ manium dioxide.

It has been stated that Beer1s law applies

to concentrations as high as I4D parts per million.

However,

9

Kitson and Mellon report that the selectivity of the pro­ cess is very low, when such ions as are present in zinc sulfate leach solutions are considered. Boltz and Mellon (2) describe the determination of germanium by the heteropoly blue method.

It differs from

the previously described method in that the molybdigermanic acid is reduced with ferrous ammonium sulfate to produce a more stable blue color.

Boltz and Mellon state that the

advantage of this method over the molybdigermanic acid method is that it possesses somewhat greater sensitivity. However, the ions present in zinc sulfate leach solutions effect the selectivity of this process equally as adversely as they effect the first process. Determination of germanium by emission spectrograph!c methods has been reported by Strock (25)* Oftedahl, et al. Although these researchers have worked with powdered samples, the writer has achieved reproducible results with liquid samples•

Eknission work possesses two advantages over

the other methods available for determination of germanium-rapidity and selectivity.

A disadvantage, when compared to

absorption spectroscopy, is relative lack of sensitivity in the lower concentration ranges* The rapidity of the method is apparent when its selectivity is considered.

Brode (lj_) and the M.I.T. Wave­

length Tables (19) record no interfering lines for either germanium, or the chosen internal standard, beryllium, for

10

the wavelengths chosen for analytical purposes• lengths used are Be-3130A and Ge-3039A»

The wave­

None of the ions

present in either type of zinc sulfate leach solution pro­ duces characteristic lines on a spectrographic plate which are close enough to interfere with measurements of their intensity*

These two lines are close enough together so

that they can be used in the second order of a grating in­ strument with correspondingly increased resolution, and with greater intensity due to the peaking of the sensiti­ vity of the instrument in the range Ô000 A - 8000 A* Thus, practically all that needs to be done to prepare a liquid sample for measurement of its germanium content is to add the internal standard, drop a portion of the sample into the head of an electrode, arc it and record its spec­ trum on a photographic plate*

No chemistry is necessary to

isolate the germanium from the rest of the solution before its concentration may be measured* Unfortunately, the sensitivity of the process is some­ what blunted in the lower concentration ranges (1-10 parts per million)#

Readings varying 5 percent from the mean have

been reported, when the densitometrie type of photographic interpretation is used* A calibration, or "working" curve for the determination of germanium in liquid solutions is presented in Figure 2. The curve covers the concentration range of 1*0000 to 0*0010 grams per liter of germanium*

The curve was obtained by

6 7 6 9 1

2

3

2

3

4

5

Concetftta.fiai*

4 5 6 7 8 9 1

2

Ge., j . / i

6 7 8 9 1

3

4

5

6 7 8 9 1

2

3

4 5 6 7 8 9 1

11

analyzing a set of* samples prepared with varying germanium concentrations and constant beryllium concentrations (0*001 grams per liter). for analysis*

A Baird Grating Spectrograph was used

The slit width of the instrument was 200

michrons, and the spectra were recorded in the second order* Excitation conditions were 220 volts and 9 amperes, direct current•

The duration of each arc was 90 seconds, with use

of a sector wheel which allowed l/30 of the arc light to pass through it to the slit,

Kodak Number 103-0 spectro­

graph! c plates were used to record the spectra, and they were developed in Kodak D-19 developer,

A Pfund, or iron,

arc was used in conjunction with a step sector wheel to ob­ tain a characteristic curve for the 103-0 plate*

With the

aid of the plate characteristic curve, the galvanometer readings of the lines Be-3130A and Ge-3039A as recorded by a selenium photocell densitometer were converted to rela­ tive exposure times, or relative intensities.

Logarithms

of the ratios of the relative intensities of these two lines as obtained for different germanium concentrations, were plotted versus the logarithms of the germanium concentra­ tions to obtain the "working curve*"

Thus, any solution

possessing an unknown concentration could then be analyzed for germanium by adding the standard amount of beryllium ion and producing a spectrum in the same manner as those pro­ duced for the "working curve."

When the ratio of the rela­

tive intensities of the two characteristic lines produced

13

on the spectro graphic plate by beryllium and germanium was determined,

it was compared with the "working curve" to

determine the unknown concentration* Initial attempts to produce a satisfactory "working curve" were failures•

Faulty electrode design was to blame.

The shape of the lower carbon electrode was found to be ex­ tremely important in achieving reproducible results.

A

gently saucer-shaped depression in the lower electrode yielded the best and most uniform vaporization of the solu­ tions into the arc streams*

It was determined by experi­

ment that 6n over-all error of 5 percent was obtained through use of this process in the range below 0*010 grams per liter of germanium concentration*

i4

REPORT OF INVESTIGATION OF METHODS FOR THE REMOVAL OF GERMANIUM FROM LEACH SOLUTIONS

I.

Chelation

Chelation, or the formation of "inner compounds" by certain organic molecules with various metals has been re­ ported extensively in the literature*

Glliman (11) des­

cribes the process as one involving secondary, or coordin­ ate covalent, bonds.

Diehl (7) has classified chelation

reactions, and reports that amine groups and derivatives possess strong tendencies to form chelate complexes*

The

well-known complex formed by dimethylglyoxime with nickel is a representative example of chelation* A series of ethylene amines was obtained and was studied, together with dimethylglyoxime, to investigate the possibil­ ity of precipitating soluble geimanium as a chelate complex. These reagents were added to 3 types of germanium-containing solutions:

the acid and neutral leach solutions and acidic

solutions containing germanium, only.

Time temperature and

pH were varied within as wide limits as possible*

The re­

sults of the investigations were as follows : Dime thylglyoxime The results were negative at temperatures from 0 to 100 degrees C, when the solution containing germanium, only, was investigated in the pH range 0.5 to 7*0.

Some

15

precipitate was formed when dimethylglyoxime was added to a sample of acid leach solution, but it did not contain spec­ trograph! c amounts of germanium. Ethylene diamine A voluminous white precipitate was observed upon the addition of ethylene diamine to both the acid and neutral leach solutions. pound,

The precipitate was obviously a zinc com­

No germanium was detected spectrographically as hav­

ing been adsorbed by the zinc-complex precipitate from either the acid or neutral leach solutions.

No precipitation was

observed when ethylenediamine was added to a portion of the solution containing germanium, only.

The temperature range

0 to 100 degrees C and the pH range 0,5 to 7*0 were inves­ tigated. Diethylenetrlamine No precipitate was observed in the pH range of 0,5 to 7*0 and temperature range of 0 to 100 degrees C, when di­ ethylene tri amine was added to the solution containing ger­ manium, only.

A voluminous white precipitate was observed

when the compound was added to the acid and neutral leach solutions.

No adsorbed germanium was detected on the pre­

cipitate by spectrographic methods, Triethylenetetramine Negative results were obtained when triethylenetetramine

16

was added to th.e solution containing germanium, only, under the same experimental conditions as before.

Rose and violet

colored precipitates were observed upon the addition of the compound to acid and neutral leach samples.

No germanium

was detected as having been adsorbed on the acid and neutral leach precipitates.

Investigation of the color noted in the

acid and neutral leach zinc-complex precipitates disclosed that cobalt and nickel were responsible for the hues pro­ duced.

It was interesting to note that with a pH change

from acidic to basic, disperse systems containing approxi­ mately one gram per liter of cobalt and 10 drops of tri­ ethylenetetramine per 50 milliliters of solution changed from red to green. approximately pH 7*

The systems displayed a yellow hue at Further, disperse systems containing

one gram per liter of nickel and triethylenetetramine changed from green to violet hues with a similar pH change.

It is

suggested that these reactions might prove of value if studied from the standpoint of either pH indication or trace analysis by absorption spectrograph!c methods* Te traethylenepent amine Negative results were obtained when the compound was added to solutions containing germanium, only.

A volumin­

ous zinc-complex precipitate was formed upon addition of tetraethylenepentamine to acid and neutral leach solution samples. tates •

No adsorbed germanium was detected on the precipi­

17

II*

Tannic Acid

Tannic acid, or tannin, has been reported previously as a reagent for the gravimetric quantitative determination of germanium.

Davies and Morgan (6 ) and Holness (12) each

report its selectivity as being high*

Preliminary investi­

gations indicated that germanium was removed quantitatively from both the acid and neutral leach solutions containing approximately 0*1 gram per liter of germanium*

This method

had been discarded earlier as an analytical procedure be­ cause of a lack of reproducibility*

The receipt of the

patented work of Zischkau (29) corroborated the adaptability of the process to the problem*

Zischkau outlined a process

for the removal and recovery of g e m a n i u m from zinc sulfate leach solutions as the tannin complex* tions by the author were twofold:

Further investiga­

First, a study was made

concerning the effect of pH on the precipitation of the germanium-tannin complex.

Second, a study was made of the

purity of the germanium-tannin complex as precipitated from the leach solutions. Experiments relative to the determination of the effect of pH on the precipitation of the germanium-tannin complex were carried out on go milliliter samples of solutions con­ taining 0*01 grams per liter of germanium*

These solutions

were made from a stock solution of sodium germanate, which had been prepared by the dissolution of pure germanium

18

dioxide in sodium hydroxide solution#

The solutions were

acidified with dilute sulfuric acid to a pH of approximately 0#5»

Further pH adjustment was carried out by the addition

of sodium hydroxide, which had been standardized against 0.1 N hydrochloric acid.

The primary standard acid was ob­

tained by the dilution of a constant-boiling hydrochloric acid mixture, after the method described by Mellon (17)» pH measurements were taken with a Beckman pH meter. Model M# 12.0.

The pH range studied was approximately 0#5 to

After the pH of each sample solution was adjusted

to the desired value, 5 milliliters of tannic acid (concen­ tration 10 grams per liter) were added.

The time required

for complete precipitation, as well as the nature of each precipitate, was studied.

Spectrographic analyses were made

of the solutions, filtered after precipitation, to check the completeness of precipitation# Figure 3 shows the typical neutralization curve obtained by plotting the amount of sodium hydroxide added to the solutions versus their pH after addition#

The nature of the

precipitates which resulted from tannin addition has been divided into 3 pH ranges.

From pH 0*5 to pH 1*5» the pre­

cipitation was complete immediately upon the addition of tannin#

From pH 1*5 to pH 5*9* disperse systems resulted,

which coagulated to yield complete precipitation after vari­ ous periods of time up to 1|_8 hours.

From pH 5*9 to pH 11*9,

the resultant disperse solution did not agglomerate within

19

m

20

4.8 hours, nor was precipitation determined to be complete within 24-0 hours. Figure 4- shows the effect of the pH of the solutions on the time required for complete precipitation.

It will

be noted that above a pH of approximately 3.0 the time re­ quired is greater than 24- hours, and that above a pH of ap­ proximately 7*0, precipitation is not complete within 5 days. The purity of the tannin-germanium complex as precipi­ tated from acid leach solutions of pH 1.0 was determined semi-quantitatively by the emission spectrographic method. Table 1 records the ions found to be present in the precipi­ tate after 3 washings with distilled water carried out both at room temperature and elevated temperatures.

Table 2 lists

the ions present in the precipitate after dissolution in a 20 percent sodium hydroxide solution and reprecipitation through the addition of 10 percent sulfuric acid.

From com­

parison of Table 1 and Table 2, it is seen that the majority of the ions present after washing are not present after dis­ solution and reprecipitation.

Therefore, it is assumed that

adsorption plays a major role in the contamination of the germanium-tannin complex precipitate.

It was noted, also,

that the precipitate, after dissolution and reprecipitation was more disperse and more difficult to agglomerate.

Spec­

trographic analysis of the filtrates from such precipitates indicated that reprecipitation was only about 75 percent complete.

21

22

Table 1 Ions Present in the Gennanium-Tannin Complex After Washing

Ion A1 As Au Cd Cu Fe Ge Mn Ni Pb Sb Si Zn (W

Wavelength 3082 .16a 231I.9 .814A 2i(.27 .95a 2288.02A 282k.37A 2338.01A 3039.06a 2576.10A 3002.50A 2833.07A 2528.54a 2506.90A 2712.50A

Relative Intensity 800 250 400 1500 1000 15 1000 300 1000 500 300 300 300

Remarks clearly visible visible visible clear, strong faintly visible visible clearly visible faintly visible faintly visible faintly visible clearly visible clear, strong clear, strong

The relative intensities are those listed by Brode for arc spectra#

Table 2 Ions Present in the Germanium-Tannin Complex After Dissolution and Reprecipitation

Ion Cd Sb Zn Ge

Wavelength 2288.02A 2528.54a 2712.50a 3039.06a

Relative Intensity 1500 300 300 1000

Remarks very faint faint faint clear, strong

Dissolution accomplished with 0# 1 N sodium hydroxide solution; reprecipitation upon acidifying the solution with 0.1 N sulfuric acid.

23

The conclusions which may be drawn from the above in­ vestigations tend to limit the scope of usefulness of tannin as a separatory reagent for obtaining germanium from zinc sulfate leach solutions.

Figure 3 and Figure If demonstrate

the limitations placed on the reaction by the hydrogen ion concentration.

Consideration of the times required for com­

plete precipitation makes it obvious that the removal of germanium would have to take place during the acid cycle of zinc sulfate leaching.

The pH being of the order of 5*0 to

6 o5 » precipitation attempts during the neutral leach cycle would involve too long a period of time for efficient opera­ tion on a commercial scale. The nature of the complex precipitate places a limita­ tion on the process, also.

Its high degree of adsorption

of other cations makes purification of a germanium-rich product exceedingly difficult.

The difficulty is enhanced

by the fact that arsenic and antimony are among those cations adsorbed, and would complicate attempts to remove the ger­ manium as the volatile chloride.

Zinc losses due to ad­

sorption might be significantly high, also.

Dissolution

and reprecipitation, while accomplishing a certain degree of purification, are on the order of 75 percent efficient, and lead to filtration problems because of the disperse nature of the product.

24

III.

Organic Reagents Similar to Tannin

The literature indicates no exact formulae for the tannins.

McLaughlin and Theis (18) describe them as complex

molecules bearing over-all similarity to glucose.

Since the

tannins occur as solvent-extraction products of trees and shrubs, investigations were made as to the ability to pre­ cipitate germanium possessed by other vegetable-extracted products and various commercial waste products which might contain tannin or similar molecules. A sample of the waste hydrolyzate from the treatment of corncobs for the recovery of furfural was obtained from the U. S. Department of Agriculture at Peoria, Illinois* Portions of the hydrolyzate were tried as précipitants for germanium in acid and neutral zinc sulfate leach solutions and in solutions containing only germanium.

The pH of the

3 types of germanium-containing solutions was varied from 0.5 to as high a value as possible, and the temperature of investigation was varied from 0 to 100 degrees C.

Negative

results were obtained. A portion of magnesium lignosulfonate was obtained from the Marathon Paper Company, Neenah, Wisconsin*

The

compound had been prepared as a by-product of the papermaking operation.

Negative results were obtained when the

compound was investigated in an attempt to precipitate ger­ manium under the conditions listed previously. A sample of waste liquor was obtained from the sulfite

25

paper-making process of the Kimberly-Clark Paper Company, Little Chute, Wisconsin*

Negative results were obtained

when attempts were made to precipitate germanium* A sample of commercial blackstrap molasses was also investigated*

Although the molasses may have possessed

some glucose-type molecules, it did not have the property of precipitating germanium, A commercial type of tea was brewed and added to the acid and neutral leach solutions.

Precipitates appeared

which were quite similar in nature to those of the germaniumtannin complex*

Analysis showed that a complete separation

of germanium had been achieved.

These results were to be

expected, since tea leaves contain a high percentage of the tannins, and tea-brewing is a so1vent-extract!on process* Two types of commercial coffee were investigated with negative results»

Although coffee-making is also an extrac­

tion process, the beans do not contain tannin or similar molecules which will precipitate germanium under the con­ ditions listed above* Commercial tobaccos were also investigated. extraction products produced negative results.

Hot water

26

IV#

Ion Exchange

Hussey (13), of the U. 3. Bureau of Mines, reports the successful application of ion exchange separations to cyanided gold and silver ores.

Tompkins and Mayer (28) re­

port that the Atomic Energy Commission has been successful in adapting the principles of of rare earths.

ion exchange to the recovery

On the basis of reports such as these,it

was decided to investigate the possibilities of separation of small amounts

of germanium from acidified solutions

through exchange

with a resin cation#

Table 3 lists the results of cation exchange experi­ ments with several different types of commercially avail­ able resins.

In each case, 20-gram portions of the resins

were agitated with 100 milliliters of leach solutions con­ taining about 0.1 gram per liter of germanium.

The agita­

tion times were 2 hours, after which each solution was filtered.

The resins were washed thoroughly with distilled

water, and both filtrates and resins were analyzed for ger­ manium with the spectrograph. It is indicated by Table 3 that the zeolite type ex­ change resins had definite partitioning effects, although colloidal silica was noted after agitation#

Decalso, a

precipitated sodium aluminosilicate with a 1 :1:6 ratio of Ha^O:Al^O^:3iO^ gave the strongest indication of germanium adsorption#

The zeolite cation exchange is essentially:

27

Table 3 Qualitative Spectrographic Results of Ion Exchange Experiments with Various Resins

Resin

Type

Amount Germanium Filtrate

Present Resin

IR-120

sulfonic acid

all

no trace

IRC-50

carboxyl!c acid

all

no trace

Zeo-Karb

sulfonated coal

all

no trace

Zeo-Dur

glauconite (hydrous silicate)

most

trace

Decalso

precipitated sodium aluminosilicate

about 1/2

about 1/2

Zeo-Rex

phenolic

all

no trace

Silica gel

about 3/4

about 1/4

Kaolin

about 3/4

about 1/4

Zeo-Dur and Decalso are zeolitic type resins.

Silica

gel and Kaolin are siliceous materials not ordinarily used for ion exchange work#

cation+x + xNaZ

cation Z + xNa+

(I)

Subsequently, other siliceous materials, such as silica gel and Kaolin were investigated.

Confirmation of

the affinity of germanium for SiOg was strengthened, since both showed strong qualitative indications of partition. However, further experimentation was not performed with

28

these materials because silica gel produced an unwieldy amount of colloidal silica in suspension after agitation, and Kaolin was virtually unfilterable after agitation*

The

colloidal silica was found to yield a precipitate with tannin similar to the tannin-germanium complex* Of the resins listed in Table 3, Decalso gave indica­ tion of the most promise*

Two series of experiments were

performed with Decalso to attempt to determine its adapt­ ability to germanium removal on a large scale*

The distri­

bution coefficient, K^, for the ion exchange reaction in­ volving Decalso and germanium, was studied from two aspects : First, the effect of germanium concentration on the distri­ bution coefficient was studied*

Secondly, the effect of

zinc concentration on the distribution coefficient was as­ certained, under conditions similar to those which occur industrially* Figure 5 demonstrates the effect of germanium concen­ tration on the distribution coefficient, K#*

Nachod (20)

defines the distribution coefficient as: Kjj = Mg/Mi x Vol. soln,v/mass of resin, m where M s and

(II)

are the fractions of the cation in the

resin and liquid phases, respectively*

The ratio Mg/Mj may

be more conveniently expressed as $adsorbed/l00$-$adsorbed* According to Schubert and Richter (2l|_), the distribution coefficient remains constant regardless of a change in the

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