US2431997A - Manufacture of nickel and cobalt salts - Google Patents

Description

Dec. 2, 1947. A. H. DU ROSE MANUFACTURE OF NICKEL AND COBALI SALTS Filed June 2, 1944 RATE OF sqLur/ow or SULFUR/ZED ELECTROSHEET xwcksz. //v 20 pm 'CENT (By VOLUME) SULFUR/C ACID w m w w a PER CENT \SI-ILI-"IJR /N THE METAL INVENTOR.

ARTHUR H. DU ROSE BY W 6% Patented Dec. 2, 1947 MANUFACTURE OF NICKEL AND COBALT ALTS Arthur H. Du Rose, Eucld, Ohio, a signor to The Harshaw Chemical Company, Elyria, Ohio, a

corporation of Ohio Application June 2, 1944, Serial No. 538,436

6 Claims.

This invention relates to the manu acture of compounds of nickel and cobalt using nickel or cobalt metal or an alloy of nickel and cob-alt in massive form as the source of nickel and cobalt. More specifically, the invention is concerned with methods of preparing compounds from such metall c masses which are relatively pure so as to be difficultly soluble in such acids, for example, as sulfuric and hydrochloric.

Nickel is available to the market in various forms adapted to the practice of the pre ent invention. including various forms of scrap metal principally cons sting of nickel and especia'ly a highly pure form of nickel known as electrosheet which is recovered from nickel ores by electrolytic processes. Such materials have been found to dissolve in ordinary, aqueous solutions of acids, such as sulfuric and hydrochloric, at a rate too low to be satisfactory. As a result, attempts have been made to speed up the solution by the use of current, blowing with air, etc. These procedures, although more or less successful, are objectionable in respect to cost and present various equipment diificulties which have discouraged their use.

I have now discovered that the relatively pure forms of nickel as well as cobalt, nickel-cobalt alloys, and alloys with other metals principally composed of nickel or cobalt, can be dissolved much more readily in such acids as sulfuric, hydrochloric, nitric, acetic and formic, if they are first sulfurized'. Sulfurization may take the form of heating the massive metal with a suitable sulfurizing agent. It is, of course, possible to melt the metal with the sulfurizing agent and thereby introduce a sufiicient quantity of sulfur, but I find that this is not necessary to the result and a much cheaper method of sulfurization can be employed,

In the drawing, the figure is a graphical representation of the relationship between the amount of sulfur in the metal and the rate of solution in sulfuric acid expressed in. grams dissolved per square foot per hour.

The introduction of sulfur into the metal may be accomplished, as above indicated, by meling the metal with sulfur, or it may be accomplished byheating the metal in massive form with a sul-' fu-rizing agent. Again, it may be accomplished by co-electrodepositin the metal with a suitable sulfurizing agent by including such sulfurizing agent in the electrodeposition bath whereby it will be codeposited and then followingv this by heat treating the resulting deposit. It will not be necessary to describe the procedure for incorporae tion of sulfur by melting the metal with sulfur or suiable sulfur compound, since that is a metallurgical procedure within the skill of the art and can be accomplished by any metallurgist skilled in the art of working nickel. Special procedures for sulfurizing by heating the massive metal with a sulfurfzing agent, and special procedures for incorporating sulfur into the metal by co-electrodeposition and heat treatment will now be descr bed.

The introduction of sulfur into the metal by heating the massive metal with a sulfurizing agent below the melting point of the metal mass depends upon several variables, temperature, time, pressure, concentration of the sulfurizing agent, and the nature of the sulfurizing agent. In general, the massive metal is heated in OOH-.- tact with the sulfurizing agent whereby the sulfur or sulfur compound is caused to diffuse into the metal. In selecting a set of conditions suitable for this type of sulfurization, I prefer to employ a pressure not much above atmospheric because such low pressures require a relatively less complicated and expensive type of equipment. I prefer to use a gaseous sulfurizing agent, such as HzS, sulfur vapor, carbon bisulfide vapor, sulfur chloride vapor, or S02 plus a reducing gas. These may be diluted with nitrogen or other inert gas for the purpose of controlling the introduction of sulfur into the electro-sheet.

While I prefer to use a gaseous sulfurizing agent as indicated, I may use various non-gaseous agents. I may, for example, dip the massive metal, such as electro-sheet nickel, into a solution of sulfur in carbon bisulfide whereby a sulficient amount of sulfur will be caused to adhere to the surface of the sheet, and then by heating the so-treated sheet I am able to cause sulfur to be diffused through the metal. Again, I may dip the nickel mass in sodium polysulfide solution or in various solutions or emulsions of sulfur in liquid carriers. In each case the sulfur-containing coating is applied and the metal is then heated at a temperature suflicient to Cause-the sulfur to migrate into the metal. Such heating will be, in general, well below the melting point of the metal mass. Heating, in general, will be continued sufficiently to cause the sulfur to diffuse substantially uniformly through the mass ofmet'al. The advantages of the invention may berealized to some extent without heating for a sufficient time to cause the sulfur to become ho mogeneously distributed throughout, but in gen-- eral it is desirable to heat long enough to secure t result; I

It is possible, also, to contact the metallic mass with finely divided sulfur by placing in a furnace a layer of metal and a layer of sulfur, another layer of metal, etc., and then heating the furnace charge to cause the sulfur to be absorbed into the metal. The amount of sulfur employed may be regulated so as to give the desired final result and the heat treating continued until the sulfur is sufficiently diffused through the metal. Preferably, such treatment would result in vaporizing the sulfur and so would be equivalent to the use of a gaseous sulfurizing agent, but a portion of the treatment might be carried out below the boiling point of sulfur.

The term sulfur when used herein to describe the composition of the treated metal is to be read as including elemental sulfur and combined sulfur, that is, sulfur compounds, it being my belief that sulfur is present in the treated metal at least partially in the form of the metal sulfide, but possibly to some extent as elemental sulfur or the compound used as the sulfurizing agent. The term sulfurizing agent includes HzS, sulfur vapor, solutions of sulfur in liquids, emulsions and other suspensions of sulfur in liquids, solid or liquid sulfur, carbon bisulfide, sulfur chloride (S2012), S02 with a reducing gas, heavy metal sulfides (e. g., sulfides of copper, lead, iron, nickel, cobalt, manganese), and mixtures of such of these as may be in gas or vapor phase with inert gases such as nitrogen.

Having selected a suitable sulfurizing agent, I treat sample pieces of the metal to be treated for various lengths of time and then test them for sulfur content. I select a time of treatment such as will introduce the desired percentage of sulfur under the selected conditions of temperature and pressure. I prefer to introduce at least .01% of sulfur into the metal. This percentage is determined by analyzing for elemental sulfur. It is desirable to introducefrom .02 to .1% of sulfur (elemental sulfur based upon the weight of the metal) and a greater amount, for example, or 2% can be used, but is not necessary. This will be apparent by reference to the draw-- ings which indicate a very good solution rate at .02% and very little increase as a result of use of large percentages of sulfur.

It will be noted that the individual determinations indicated on the drawings by small circles do not fall upon a sharply defined curve but do fall Within a clearly defined area. The reason for this is that there is very substantial individual variation in the determinations which I believe is explained by the existence of a fairly large experimental error. This experimental error arises from (1) variation due to the fact that the metal dissolved in the solubility test and the metal analyzed chemically for sulfur content could not be the same, and (2) variation due to inability to measure the actual surface exposed which varies from the apparent surface on account of small irregularities.

Havingdetermined the optimum conditions for introduction of the selected amount of sulfur, I proceed to follow these conditions in the treatment of the metal or alloy to be treated, after which such metal is dissolved in sulfuric acid or hydrochloric acid or another of the acids mentioned above depending upon the compound to be made. I find that the solution rate is quite Satisfactory when from 02% to .1% of sulfur has-been introduced as is clearly indicated in the drawing.

Heat treating will normally be a separate p from the step of absorbing the sulfur into the metal, but obviously it is possible to overlap or combine the two steps by placing a predetermined amount of the sulfurizing agent and the body of metal in a heating furnace or oven and elevating the temperature to the desired degree.

Normally the absorbing step will be carried out at a temperature of the order of 300 C. to 700 C. for a few minutes, say one to ten minutes, and then the supply of sulfurizing agent will be cut off and the temperature will be raised to from 600 C. to 1000" C. and held there from a quarter hour to five or even ten hours to thoroughly diffuse the sulfur throughout the plate, or continued heating at 500 C. (after stopping the fiow of sulfurizing gas) for two to 24 hours. After diffusion of the sulfur, the metal may be air cooled, furnace cooled, water quenched, or acid quenched.

It may be desirable, instead of melting the sulfur with the metal or of introducing it by heating with a sulfurizing agent below the melting point of the metal, to introduce the sulfur by co-electrodepositing a sulfur compound with the metal and then heat treating. This might be done in connection with the electrolytic recovery of nickel or cobalt by simply including a suitable sulfur compound in the solution from which the electro-sheet is deposited.

I am aware that co-electrodeposits have been made from solutions containing sulfur compounds and resulting in the inclusion to a small extent of such sulfur compounds in the deposit. For example, in the deposition of nickel in brilliant form for ornamental purposes, it is common to make use of a sulfur-containing compound such as a naphthalene sulfonic acid, and this does result in the inclusion of a small amount of the sulfur compound in the deposit. Such deposits. however, even if it were attempted to use them as a source of metal to be dissolved for the formation of nickel compounds, would not prove satisfactory in view of, the nature of the deposit. I have found that in making co-electrodeposits from electroplating solutions containing sulfur compounds, the sulfur compounds are laid down in layers. There thus results a layer which is diflicult to dissolve because it contains insuificient sulfur, followed by a layer which contains more sulfur than is necessary. The result is that the solution rate of co-deposits thus formed is relatively low. I have found, however, that if a deposit so made is heat treated, the sulfur becomes diffused and substantially homogeneously distributed and the solution rate is increased to a satisfactory level.

In preparing electrodeposits of nickel or cobalt for solution in acids to form the corresponding compounds, I may make use of any of various electroplating solutions, including therein a suitable source of sulfur, such as thiourea, sodium thiosulfate, saccharine, various aromatic sulfonic acids, such as the benzene and naphthalene sulfonic acids and their sodium, nickel and cobalt salts. Various other soluble sulfur compounds capable of co-depositing with metal may be employed. While the inclusion of sulfur in the deposit results in some improvement in the rate of solution without the heat treating step, I have observed that by heat treating at relatively low temperatures and for relatively short periods of time, I am able to more than double the solution rate. I attribute this mainly to the breaking down of the laminar structure of the electrodeposit, and it may also be due in some degree to the 5, breaking down of; the sulfur compound used; the plating solution toa simpler compound Qrto, the reaction of: such compound with the metal to form a, metal sulfide. I preferto. makeuse of plating solutions containing such quantities. of sulfur compounds asto result in the inclusion in the. electrodeposit of at least 01%: of sulfur cal-. culated as elemental sulfur, and preferably from 02% to. 1%. I do not mean to imply that the sulfur is necessarily present in the deposit as elemental sulfur but only that the sulfur com-. ponent of whatever compound is there present amounts to the percentages indicated.

Heat treatment of the electrodeposit should include heating at a temperature from 250 C. to 13009 C. for a time sufiicient to cause substantial diffusion of the sulfur whereby to increase the solubility in sulfuric, hydrochloric, nitric, ace tie and formic acids. This can be accomplished in as little as one minute at 1300- C. but may requireas much as 30 minutes at 250C. Longer heatingtimes are advantageous especially at, the w r emn r tu s.

The following examples will serve to illustrate the invention:

Example I A body of electro-sheet nickel was exposed to; a

mixture of one part H2S and parts nitrogen.

by volume. The temperature was 600 C., the pressure only slightly elevated above atmospheric, and the time was 3 minutes. The body was then heat treated at 800 C. for one hour to diffuse the sulfur, the nitrogen flow being continued throughout the heat treatment to an extent sufficient to prevent oxidation. That is, the atmosphere in the heat treating furnace was non-oxidizing throughout the treatment. The resulting body contained approximately 0.13% sulfur and when introduced into 35% (by vol ume) sulfuric acid at boiling temperature exhibited a solution rate of approximately 148 grams per square foot of apparent surface per hour. (The surface was approximately fiat but rough and no attempt was made to measure the increase of surface due to roughness. The apparent surface was used. Numerous similar determinations were made with electro-sheet nickel sulfurized by means of HzS, using aqueous sulfuric acid as the solvent. These are plotted in the drawing.)

Example II A body of electro-sheet nickel was placed in a combustion tube with a combustion boat containing sulfur chloride ($2012). The temperature was 600 C. and nitrogen was passed through the tube so as to vaporize the sulfur chloride and bring it into contact with the electro-sheet nickel. This treatment was continued for hour and then the temperature was raised at 800 C. for one hour. The resulting nickel analyzed .24% sulfur and dissolved very readily in both sulfuric and hydrochloric acid, approximately 60 grams per square foot of apparent surface per hour in 20% (by volume) sulfuric acid.

Example III A small piece of electro-sheet nickel was packed in lead sulfide in a crucible and heated for one hour at 750 C. The nickel analyzed .007% sulfur and showed increased solubility in both sulfuric and hydrochloric acid as compared to pure electro-sheet. In a similar case, using copper sulfide instead of lead sulfide, the nickel 6. nalyzed: -Q su fur nd; dissol ed in. sulfuric. and; hydrochloric. acid-1 more readilythan pure; electroesheetnickel. (Solution; rate. was. not.- quantitatively determined):

Ex mp e V A nickel. pl tin olut on conta nin .90. r ms of m 1 sulfate .NiSQiGHZQ 0- eram p r:

liter; of ni el hloride N C1a6H2Ol. 37-5 rams. per; iter bor cacid. H 303)... 4.. crl ter of formi acid. and. ne. ram. per lit r of. thi rea. remainde wateuwas used} to p oduc anelectr deposit. The depositwasfound. to contain 0.5 4%. sulfur}. Before heat; tr atment, this deposit. dissolvedin; 2.0% (by. volume) sulfuric acid at the; rate; of" 110 grams per square foot perhour. After heating at 700 C. for A; hour, the solution rate. in the same acid had increased to. 2811 grams per square foot. per hour. This compares with a solutionrate. of- 4 to. 8 grams per square. foot per hourin the case of untreated nickel electro-sheet.

that used in Example IV' contained 2 grams per liter: of saccharine in place of the thiourea ofExample This'deposit analyzed 028% sulfur, and before heat treatment had a solution rate of 22 grams persquare foot per hour in 20% (-by' volume) sulfuric acid. Afterheating at 700"" C. foa houuthe solution rate had increased to 52 grams per square foot per hourin the same acid.

Having thus described my invention, what I claim is:

1. In the manufacture of compounds of nickel and cobalt from the metal, the steps of sulfurizing a body of metal of the class consisting of nickel and cobalt and alloys of nickel and cobalt by heating such'body in contact with a sulfurizing agent of the class consisting of hydrogen sulfide, sulfur, carbon'bisulfide, sulfur chloride, sulfur dioxide with a reducing gas, and the sulfides of copper, lead, iron, nickel, cobalt and manganese and mixtures of such materials, the temperature of heating being at least 300 C. and being continued for a sufficient time to introduce from .01% to 2% of sulfur, calculated as elemental sulfur, into the metallic body and to diffuse the same therethrough, and then dissolving the resulting sulfurized metallic body in an acid of the class consisting of sulfuric, hydrochloric, nitric, acetic and formic.

2. In the manufacture of compounds of nickel and cobalt from the metal, the steps of sulfurizing a body of metal of the class consisting of nickel and cobalt and alloys of nickel and cobalt by heating such body in contact with hydrogen sulfide, the heating being carried out between 300 C. and 700 C. for a sufficient time to introduce from .01 to 2% of sulfur, calculated as elemental sulfur, into the metallic body and to diffuse the same approximately evenly throughout, and then dissolving the resulting sulfurized metallic body in an acid of the class consisting of sulfuric, hydrochloric, nitric, acetic and formic.

3. In the manufacture of compounds of nickel and cobalt from the metal, the steps of sulfurizing a body of metal of the class consisting of nickel and cobalt and alloys of nickel and cobalt by heating such body in contact with sulfur, the heating being carried out between 300 C. and 700 C. for a suiiicient time to introduce from .01 to 2% of sulfur, calculated as elementalsulfur,

into the metallic body and to difiuse thesameapproximately evenly throughout, and then dissolving the resulting sulfurized metallic body in an acid of the class consisting of sulfuric, hydrochloric, nitric, acetic and formic.

4. In the manufacture of compounds of nickel and cobalt from the metal, the steps of sulfurizing a body of metal of the class consisting of nickel and cobalt and alloys of nickel and cobalt by heating such body in contact with a mixture of an inert gas and hydrogen sulfide, the heating being carried out between 300 C. and 700 C. for a suflicient time to introduce from .01 to 2% of sulfur calculated as elemental sulfur into the metallic body and to diffuse the same approximately evenly throughout, and then dissolving the resulting sulfurized metallic body in sulfuric acid. a

5. In the manufacture of compounds of nickel and cobalt from the metal, the steps of sulfurizing a body of metal of the class consisting of nickel and cobalt and alloys of nickel and cobalt by heating such body in contact with a sulfurizing agent of the class consisting of hydrogen sulfide, sulfur, carbon bisulfide, sulfur chloride, sulfur dioxide with a reducing gas, and the sulfides of copper, lead, iron, nickel, cobalt and manganese and mixtures of such materials, the heating being continued at high enough temperatures and for a sufficient time to introduce from .01 to 2% of sulfur, calculated as elemental sulfur, into the metallic body, thereafter bringing the temperatureto at least 600 C. for at least 15 minutes to diffuse the sulfur through said body, and then dissolving the resulting sulfurized metallic body in an acid of the class consisting of sulfuric, hydrochloric, nitric, acetic and formic.

6. In the manufacture of compounds of nickel and cobalt from the metal, the steps of sulfurizing a body of metal of the class consisting of nickel and cobalt and alloys of nickel and cobalt by heating such body in contact with a sulfurizing agent of the class consisting of hydrogen sulfide, sulfur, carbon bisulfide, sulfur chloride, sulfur dioxide with a reducing gas, and the sulfides of copper, lead, iron, nickel, cobalt and manganese and mixtures of such materials, the temperature of heating being at least 300 C. and being continued for a sufficient time to introduce from REFERENCES CITED The following references are of record in the file of this patent:

Carpenter and Robinson, Metals, vol. II, page 1386. Published by Oxford University Press, London,-New- York, and Toronto (1939).

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