BE521966A - - Google Patents

Description

       

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  IMPROVEMENTS IN THE MANUFACTURING OF PULVERIZED METALS.



   The present invention relates to obtaining the pulverized metals. More particularly, it relates to obtaining metals in powder form by direct reduction with a gas. More particularly still, it refers to the direct reduction by a gas, of metal salts in acidic, neutral or basic solution, in order to obtain the metal in a good yield and in a commercially acceptable purity.
In general, the present invention relates to the obtaining and / or refining of metals as varied as cadmium, cobalt, copper, mercury, nickel, silver and some of the more rare metals. res located between silver and cadmium in the order of increasing electromotive forces, and capable of forming a complexed ion with ammonia. Among these,

   those most commonly encountered are the problems of copper, nickel and cobalto As these problems are general and their solutions are applicable throughout the field considered * the discussion of obtaining the metal from solutions contained these cations should be regarded as illustrative
A general description of the method according to the present invention is simple. A clarified solution containing a dissolved salt of the desired metal is adjusted to optimum values for hydrogen ion content and dissolved matter, and subjected to increased temperatures, usually above the boiling point, under partial and high pressure. the presence of a suitable reducing gas, the solution preferably being thoroughly stirred during the process.

   The reducing conditions are maintained until the reduction is sufficiently complete. The above product is collected, washed, dried and used or shipped. The residual washing solutions and / or liquors are subjected to various recovery and recycling treatments
However, the simplicity of the process thus described is more apparent.

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 than real. In the past, many attempts have been made to process like solutions under superficially like conditions, with the stated aim of obtaining like products. However, due to the large and growing demand for such a method, the complete failure of these proposals to obtain the desired results is made evident by the absence of their commercial success.

   These proposals have failed either because of the purity of the product, or because of the product yield, or for various reasons based on economic considerations and they have not been able to develop them to the point of making them competitive.



   The main aim of the present invention is therefore to achieve a suitable wet metallurgy process which does not have the various drawbacks of the known processes. Such a process should lead to the products in the form of metals with high yield, high purity, reasonable price, without the need for unusual or expensive equipment and using reagents, simple and readily available.



   It is surprising, considering past failures, that this goal has been achieved in a very satisfactory manner. This was made possible by the combination of two factors. First of all, a strict control is made of the composition of the adjusted solution, namely its concentration of dissolved metal, its content of free hydrogen or of hydroxyl ions, of ions or salts capable of forming a soluble complex of the metal and in dissolved foreign matter; reduction temperature; the partial pressure of the reducing gas; reaction time; proper use of agitation and proper use of reducing gas. Secondly, the composition of the solution is checked on a new basis not yet recognized.

   It is the control of the composition of the solution at the final and not necessarily the initial stages of the reduction period that is critical to obtaining the optimum desired results. Finally, the control is suitable for obtaining the metallic product in the desired physical state.



   Attempts to practice previously proposed methods have always resulted in one or more of the following unsatisfactory results. In many cases, no elemental metal powder is obtained at all. Rather, an oxide, hydroxide, carbonate or sulfide is obtained. In some cases, some metal may initially precipitate, after which the reaction ceases or is accompanied by precipitation of a compound of the metal.



   It has been found, of paramount importance to the present process, that these failures are mainly due to the failure to recognize the importance of avoiding certain terminal conditions until the precipitation. of the metal has reached the satisfactory phase. In the present process, the operating conditions are adjusted initially and if necessary subsequently to prevent these conditions from being obtained prematurely.



     It has also been found in accordance with the present invention that the conditions for the completion of the reduction have certain defined optimum limitations. Within certain limits, individual conditions can be changed considerably. However, for each of the conditions that must be checked, limitations must be observed. Optimum condition intervals may vary in some cases for different metals in different solutions. Therefore, they will be described more fully for these particular cases.



   Beforehand, however, one can, one should note certain generalizations. First, perhaps, it should be noted that the initial source of the solution containing metals is uninfluenced. It can be any or all of 1) the sulphide ores or concentrates that have been attacked

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 by various known methods including ancillary roasting and / or mixing phases;

   2) oxidized ores, precipitates containing metal, crude metal, slag, slag, which have been attacked, or 3) used surface treatment or pickling solutions or other waste solutions or by-products resulting from some other unimportant operations.,
In the following description, for the sake of simplicity, the abbreviations "atm" will be used to denote kg / cm2, g / l. grams per liter, and M / 1, gram molecules per liter. The terms “free acid” and “free ammonia” will also be used. Solutions of metal sulphates and ammonium sulphate have an acid reaction with a pH in the range of about 2.0 to 4.5. However, these solutions are considered to have no "free acid" or "free ammonia" content.

   When the amount of sulfate or other anions present exceeds that required for the combination with the metal and ammonium cations, the solution is considered to contain "free acid".
When ammonia is added to these solutions, an ammonium salt forms with the free acid. If ammonia is continued to be added, part of it remains dissolved in the solution, intact or in the form of ammonia; one part combines with the metal to form a metal-ammonia complex ion or "amine" metal. The term "free ammonia" present is considered to include each of the latter forms, but not that which forms an ammonium salt. The term "total ammonia" refers to the sum of the "free ammonia" and the ammonia present as the ammonium salt.



   The amount of "free acid", or "free ammonia" present is determined by titrating the natural pH of the sulfate or other salt in solution. It is therefore possible to have not only salt solutions having a clean acidic pH without containing "free acid", but also having a pH below 7 but which contain an appreciable amount of free ammonia. It should also be noted that when we speak of the amount of ammonium, sulphate or other ions, we mean both the associated and disassociated forms. An exception is hydrogen ions and only their dissociated form is referred to.



   In addition, it will be assumed in this description that the solution to be treated contains only a single metal reducible by a gas under the operating conditions. This is an assumption which can be guaranteed, since various methods of selective precipitation or dissolution, fractional crystallization and the like are known, by which substantially pure solutions of single metal salts can be obtained. The means by which this solution is obtained is therefore not a characteristic of the present invention. It will be assumed that the solutions to be treated have a usable concentration of metals. This depends to some extent on the value of the metal itself.

   For high value metals such as cobalt or silver, low concentration solutions of up to 10g / l or less can be usefully treated. On the other hand, for a metal such as copper, solutions containing 20g / l or more are desirable.



     It should also be noted that the solutions to be treated will ordinarily be of aqueous origin and nature. However, in the selective separations of various metals and salts, by known methods, other solvents such as alkanols, ethers, ketones, esters and the like have been possible. Any solvent which dissolves the metal compound at reasonable concentrations and which withstands the other operating conditions can be used in the present process if desired. In some cases the reducing gas may be more soluble than in water, hydrogen being more soluble in methanol, for example. However, aqueous solutions will be those most commonly encountered and will be taken as illustration.



   As noted above, the present invention relates to

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 metals whose oxidation-reduction potential lies between those of cadmium and silver included and which are capable of forming a complex ion which can be reduced by a gas. This can be in the form of an amino complex cation of the type [Mex (Am) y] in which Me is the metal and Am is a complex forming amine. Oh can find them in solution under conditions ranging from a little acidic to strongly basic. On the other hand, one can find complex anions of the AcxMey type in which Ac represents an acid radical in solutions ranging from slightly basic to strongly acidic.



   Ammonia is generally taken as the amine forming a complex and the invention relates mainly to its complexes with cobalt, nickel or copper as a type of "amine" o Ammonia is the most economical of the amines available. and in practice the most commonly encountered.



  However, similar or even better results, although usually at a higher cost, can be obtained by using various organic amines such as methylamine, ethylene diamine and the like in place of some or all. ammonia.



   The anion can vary widely, depending to some extent on whether the solution is acidic or basic. In ammonia solution other anions may be present, except those which form an undissociated complex with the metal or which react with the reducing gas. Under acidic conditions, fluosilicate, acetate or other anions can be used which give adequate solubility of the metal if they do not react with the reducing gas. Strong monoacids such as nitric and hydrochloric acids cannot be used commercially although they can be made active in ammoniacal solution.



   From a practical point of view, for economic reasons, the anions which are encountered commercially are quite limited. In basic solution these will be the sulphate or carbonate ions. In acidic solution, it will be the sulphate, fluosilicate or acetate ions that may be encountered. They will therefore be taken as illustrative for the present description.



   In general, many gases can be used to reduce metal salt solutions. However, for the practice of the present invention, it has been found that gases containing sulfur eg H2S and SO2 generally lead to products containing sulfur. Therefore, it is highly desirable if not absolutely necessary to avoid the use of reducing gases containing elements which react with the metal of interest to form undesirable compounds, for example sulfur which tends to form sulphides.



   The reducing gas may be most convenient for this purpose is hydrogen. It is easily obtained by a large number of different and industrial processes. Its use did not lead to contamination of the metal obtained.



   Carbon monoxide can also be used. It is somewhat more potent than hydrogen, and reductions can usually be made at lower temperatures. Carbon monoxide is particularly useful for the reduction of copper-ammonium carbonate solutions, where it also tends to produce a larger and usually denser powder. However, for the reduction of the other solutions the pulverized products obtained with hydrogen are very suitable. If carbon monoxide is used as a reducing agent, it is converted into carbon dioxide.



   In reducing acidic solutions, the release of carbon dioxide increases the pressure required for optimum reduction and may limit the degree of reduction that can be achieved in a single operation. In addition, with some metals, for example nickel, carbon monoxide forms carbonyl compounds especially in solution.

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 basic and for these solutions, the difficulty in handling carbonyl makes the use of carbon monoxide undesirable.
Many organic compounds which are ordinarily gaseous or give rise to gases at the reduction temperature technically reduce the metals in their solution. Among them are formaldehyde, formic acid, hydrazine, and the like. Many are economically impractical.

   Many do not-reduce to elemental metal. Some are operationally unsuitable. Hydrocarbon reducing gases such as methane are not particularly useful. Even at total pressures as high as 63 atm, at temperatures where hydrogen or carbon monoxide is effective, methane and the like do not precipitate the metal. The need to use higher temperatures and pressures does not eliminate their use but makes it unlikely because uneconomical.
In general, therefore, the use of hydrogen, carbon monoxide, or mixtures thereof is the most desirable or commonly encountered practice.

   In the present process, the reduction is usually carried out in stirred vessels, capable of withstanding a total pressure of about 70 atm or more. It is therefore economically desirable to complete a reduction in the shortest practicable time, and the conditions are usually adjusted to achieve a reduction of adequate completion in a relatively short time. Preferably this should be about half an hour or less. If this is not possible, longer reduction times of up to about two hours may be required. The conditions referred to herein as optimum will therefore be those which will provide the desired degree of reduction in about one-half to two hours.



   Although in many cases, if the processing conditions are maintained long enough beyond two hours, the reduction can be carried out at lower temperatures and pressures and in non-optimum composition solutions, it is not possible to achieve this reduction. there is no economic justification for doing so. Conversely in many cases the reduction can be achieved in less than half an hour, particularly if sufficiently high temperatures and pressures are used. However, the additional heat and usually the additional strength of the required vessel outweighs the actual economic benefit of this time saving.



   When supplying reducing gas it is desirable to maintain its partial pressure above the fluid in the reaction vessel at about one atmosphere or more until the reaction period is complete. Although it may be possible in some cases to achieve some reduction to metal in the presence of a smaller quantity of gas, for example hydrogen, it is usually not worth lowering the limit d. 'an atmosphere. Usually even higher pressures initially, up to about 21-35 atm. are desirable.

   When and if an adjustment is required during reducibn, it can be achieved by a) increasing the partial and total pressure by introducing more reducing gas; b) reducing the total pressure by allowing gas to escape from the container, or c) by a combination of the two means. The exact process can be determined by measuring the composition of the vapor phase.



   Some agitation of the solution is desirable. Adequate contact must be made between the reducing gas and the solution. This is facilitated by the addition of the reducing gas below the surface of the liquid.



  Further help if the added gas is dispersed by the agitator. Suction of gas from above liquid by the agitator is also desirable.



  Stirring generally helps the reduction reaction. However, when the reduction conditions are such that the formed powder is of fine size, prolonged stirring beyond the point at which the reduction is complete should be avoided, as these fine particles tend to accumulate as a deposit on it.

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 apparatus and / or to agflomerate in low density mass. It is therefore necessary to control the degree of agitation to obtain the mixing required for rapid reduction. It should not be too intense or be continued for an extended period sufficient to produce a deleterious effect on the metal produced.



   In the practice of the invention, the optimum conditions for each element to be precipitated as a metal can be varied somewhat. Hence, the optimum conditions will be separately illustrated in the following examples with respect to the desirable process to be used in obtaining each of the illustrative metals. This not only illustrates the practical applications of the invention, but also the general characteristics of the process.



   In discussing the various practices of the invention, it should be noted that many ions can be present in solution in small amounts without affecting the desired reduction. For example, there may be cations of various metals higher than cadmium in the range of electromotive forces. However, they must be soluble.



  Other anions should be present provided that they do not limit the solubility of the reduced metal or do not react with the reducing gas. However, since large amounts of these foreign salts reduce the solubility of the desired materials and lower the reaction rate, they should be avoided as much as possible even if they do not react.



   In the discussion of the examples given below, the solutions used are usually those containing only a metal reducible by a gas under the conditions used. On the other hand, it is not necessary that the optimum conditions for the precipitation of the metal lead to a pure metal. However, other gas-reducible metals may be present under certain circumstances. This is the case when their joint reduction with the desired metal results in a useful alloy. In some cases, too, they may be present in an amount which is practically not worth removing, either because of their small amount or because their presence in the desired metal does not affect its slit or its subsequent use.

   In other cases, the metals can be precipitated separately by preferential reduction procedures.



   COPPER REDUCTION.



   Commercially pure copper is obtained in large quantities by processing sulphide ores, oxidized ores or secondary metals. From the attack of sulphurous ores or concentrates, copper is usually obtained in the form of a sulphate solution which may also contain ammonium sulphate and either free ammonia or free sulfuric acid. . In attacking oxidized ores, secondary metals or other raw forms of copper, the solution obtained may be similar or be an ammoniacal carbonate solution.



   Hence, by way of illustration, an aqueous solution containing copper sulphate and / or carbonate and ammonia ions will be used, the latter being present largely in a complex with copper and in the form of copper. ammonium ion.



   COMPOSITION OF THE SOLUTION,
We can meet various copper salts. Sulphates and carbonates will be taken by way of illustration. Copper, as the sulfate, is soluble in acidic or basic solution containing a complex amine, usually ammonia, up to about 100 g / L at room temperatures and more at elevated temperatures.

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   Cuprous and cupric carbonates are both soluble in ammoniacal solution. These solutions containing both can be prepared with more than 200 g / l of dissolved copper at room temperature. At higher temperatures, both are less soluble, the solubility of cuprous copper decreasing faster. As a result, upon heating to temperatures above the atmospheric boiling point, which as will be seen is necessary for reduction to metal in a reasonable time, excess copper over about 135 - 150 g / l precipitates as of a copper compound, usually an oxide.

   This occurs, either immediately, or when, during reduction by metal or hydrogen, enough cupric copper is reduced to the cuprous state to cause the solubility limit of the total cuprous copper to be exceeded. in the following table I are given illustrative values of NH2, CO2 and Cu + (expressed in CuO) which, if the cuprous copper content is not exceeded, do not precipitate the cuprous oxide in 10 minutes of heating these solutions at approximately 377.



   TABLE I.



  Oxide precipitation limit for the system (Cu2O-NH2-CO2)
 EMI7.1
 
 <tb> Molecules <SEP> for <SEP> hundred <SEP> Report <SEP> NH3 / C02
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Cu2O <SEP> CO2 <SEP> NH3
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 0 <SEP> 0 <SEP> 100 <SEP> 00
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 3 <SEP> 7 <SEP> 90 <SEP> 12.9
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 4.5 <SEP> 10.5 <SEP> 85 <SEP> 8.1
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 6 <SEP> 14 <SEP> 80 <SEP> 5.7
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 7.5 <SEP> 17.5 <SEP> 75 <SEP> 4.3
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 7.75 <SEP> 22,

  25 <SEP> 70 <SEP> 3.1
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 7.75 <SEP> 27.25 <SEP> 65 <SEP> 2.4
 <tb>
 
The values given in Table I are for solutions in which the actual cuprous copper content is approximately 135 g / l. For solutions of other dilutions, the molecular percentage of Cu2O differs and is presumably decreased. Continued heating of the solution to this temperature is accompanied by slow continuous precipitation of Cu2O until the cuprous content of the solution has reached. decreased to about 90 g / 1. It should be noted that if carbon monoxide is present, a cuprous complex forms and it does not precipitate oxide under otherwise similar conditions.



   If copper compounds are precipitated by heating they are reduced to metallic copper during further reduction. In general, this practice is not desirable since the resulting metal is a light, flaky, dendritic powder of poor physical characteristics, and which has a marked tendency to carry impurities which dilute it. Therefore, in the preferred practice, the solution of either carbonate, sulphate or other salt should be below copper saturation both at room temperature and at room temperature. erase reduction. If more concentrated solutions are to be used, their preparation and handling should take place at a controlled temperature to avoid this unwanted precipitation of salts or oxides.

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 of copper.

   In general therefore, the solutions commonly encountered of sulphate will preferably contain less than about 100 g / l of copper, those of carbonate less than about 130 g / l. It is seldom desirable, for reasons of economy, to process solutions of less than about 20 g / l.



   Other dissolved matter contents may vary. For example, metallic copper can be successfully reduced from solutions with widely varying hydrogen ion content. Therefore, solutions can range from solutions of strongly basic amines containing a lot of free ammonia or other amines to those containing large amounts of free acid. In addition, regardless of the pH or anion present, it is desirable, and generally is, that the solution contain some other dissolved salt other than those of the metal usually ammonium salts.



   It appears that, at least in the initial stages, braking the reduction speed produces a better, denser metal. These salts produce the desired result. Dilute solutions as low as 0.1 M / L, for concentrated solutions of about 0.5 M / L, produce an observable improvement, leading to a metallic copper powder that is denser and more granular than the sponge metal obtained. when she is absent. On the other hand, one must avoid a great excess. Although ammonium salts are soluble to 4 M / L or more at ambient temperatures, without noticeable reduction in the solubility of the copper salt, reduction to metal from solutions with a high ammonium salt content requires more severe reducing conditions to obtain equal yield.

   Therefore, it is good practice to use about 0.1 - 2.5 M / L of ammonium salts or their equivalents.



   The reduction can be started in a basic solution containing free amines, namely ammonia. Some free ammonia is needed if reduction is to be started on the basic side regardless of the anion. This criterion differs somewhat, however, depending on the anions. We will take as illustration sulfates and carbonates.



   In carbonate solutions the amine content can be high. For example, reduction has been achieved at free ammonia concentrations of up to 9 M / l. However, increasing the free ammonia content increases the vapor pressure of the solution and can unnecessarily delay the reaction. Hence, excessively large amounts require heavier and more expensive equipment to maintain the reaction at the reduction temperature. Illustrative results of the effect of modifying the NH 3 or CO 2 content for ammoniacal carbonate solutions of different cuprous / cupric proportions are shown in Table II.



   TABLE II.



  Effect of variations in NE) or CO2 content on reduction o
 EMI8.1
 Reduction% (nar H2 at I77 and 63 atm for 75 minutes).
 EMI8.2
 gJ1 147 dl Gu ++ 104 gel Ce-- 49 gJ1 Gu ++ 0 glicc + C02 a If or 52 "Or + 47" Cu '156 "Cut
 EMI8.3
 
 <tb> (155 <SEP> " <SEP> NH3) <SEP> (155 " <SEP> NH3) <SEP> (L45 <SEP> " <SEP> NH3)
 <tb>
 <tb> 70 <SEP> - <SEP> 98 <SEP> -
 <tb>
 <tb> 80 <SEP> - <SEP> - <SEP> 97
 <tb>
 <tb> 90 <SEP> 75 <SEP> 96 <SEP> 98
 <tb>
 

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 EMI9.1
 g / 1 147 g / 1 Cu 104 g / 1 Cu + 49 gll Cu * + 0 g / lCu '""' C02 0 i1 Cu + 52 Ii Cu 1- 4? Cu + 156 t Cut (155 '3) (155 "NH3) (145" NH3)
 EMI9.2
 
 <tb> 100 <SEP> 77 <SEP> 98 <SEP> 98
 <tb>
 <tb> 110 <SEP> 79 <SEP> 90 <SEP> 98
 <tb>
 <tb> 120 <SEP> 76 <SEP> 75 <SEP> 90
 <tb>
 <tb>
 <tb> g / 1
 <tb>
 
 EMI9.3
 (110 y1 C02) (105 g / 1,002) (100 g / 1 C02)

   BORN
 EMI9.4
 
 <tb> 110- <SEP> 78 <SEP> 55
 <tb>
 <tb>
 <tb> 120 <SEP> 86- <SEP> -
 <tb>
 <tb>
 <tb> 130 <SEP> 96- <SEP> -
 <tb>
 <tb>
 <tb> 140 <SEP> 99 <SEP> 98 <SEP> 66
 <tb>
 <tb>
 <tb> 150 <SEP> 99 <SEP> 98 <SEP> 80
 <tb>
 <tb>
 <tb> 160 <SEP> 98 <SEP> 80
 <tb>
 <tb>
 <tb> 170 <SEP> 99- <SEP> -
 <tb>
 <tb>
 <tb> 180- <SEP> - <SEP> 80
 <tb>
 <tb>
 <tb> 190- <SEP> 99
 <tb>
 
One cannot define the desirable amount of CO2 or HN3 to be present without referring to one to the other or to the amount of
 EMI9.5
 copper dissolved. If the content of 002 and therefore of (NHI) C03 is too high, the reduction rate is affected, in particular at high copper / copper proportions.

   However, the results shown in Table II may be influenced by the precipitation of cuprous oxide and should not be extrapolated to application at more dilute concentrations of copper or to solutions of other salts.



   For carbonate solutions, the maximum molecular ratio of CO2 / Cu initially present which allows obtaining pure granular copper powder is of the order of approximately 0.8 for solutions containing 2 molecules of NH3; total per molecule of Cu, to about 1.5 for solutions containing 6 molecules of total NH3 per molecule of Cu. In general, the optimum total ammonia content is found to be about 4 NH3 molecules per Cu molecule, resulting in about 3.8 free NH3 molecules per Cu molecule. For higher CO 2 contents it has been found that some of the copper obtained is likely to consist of a foil-like deposit on the wet surface of the apparatus.
 EMI9.6
 



  By way of comparison, for sulphate solutions, if the reduction is started on the basic side, it is usually found that the ammonia content need not be as high as for the carbonates. At less than about 1.8 free NE molecules per Cu molecule, the solution is no longer basic. From this proportion up to about 3-5, one can operate but there is no particular utility in using a

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 excess.



   Other metal salts can also be present. They can even replace part of the previous ammonium salts and contribute to the success of the reduction to copper, provided that the cation is not reducible by a gas under the conditions of the reduction and that the anion does not react. with reducing gas. However, the presence of excessive amounts of foreign salts should be avoided, as tending to reduce the solubility of copper in solution. When other elements which can form amino complexes are present, the composition of the solution must be adjusted to meet their requirements in addition to those of copper.



   It is easy to show this effect. A small amount of Zn is frequently found in certain ammoniacal solutions of copper carbonate.



  A series of copper-zinc solutions containing approximately 160 g / 1 of dissolved metal are subjected to different Cu / Zn ratios and approximately 105 g / 1 of C02, 150 g / 1 of NH3 and a Cu ++ / Cu + ratio equal to 1 to reduction for about 75 minutes to about 1770 and a total pressure of 63 atmospheres using hydrogen. Illustrative results are shown in Table III.



   TABLE III.



  Effect of Zn present during Cu reduction.
 EMI10.1
 
 <tb> g / 1 <SEP> Zn <SEP>% <SEP> Reduction <SEP> of <SEP> Cu
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 10 <SEP> 80
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 20 <SEP> 87
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 30 <SEP> 90
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 40 <SEP> 93
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 50 <SEP> 94
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 60 <SEP> 94
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 70 <SEP> 94
 <tb>
 Under the conditions of the test, the presence of zinc produced a marked improvement.

   However, for notably more dilute solutions of copper or in which the content of NH3 and CO2 is too low to retain zinc, this advantageous result should not be expected.



   In addition to these issues of copper solubility, amine content, and foreign salt content, all of which have been noted for basic solutions of salts such as carbonate and sulfate, the issue of content should be noted. in free acid. Anions, such as sulfate, form salts which are both stable and soluble in acidic solution. The solution can be strongly acidic. Reduction of copper is possible to hydrogen ion contents equivalent to those of solutions containing up to 170 g H2SO4 per kg H2O or more. However, at these or higher H + contents, the sulfate ion may be reduced to sulfide and the copper powder may contain copper sulfide.

   When copper is reduced, either by hydrogen or by carbon monoxide, a stoichiometric amount of acid anions is released which forms acid and the H + concentration increases. It is therefore desirable to avoid starting with a solution that is too acidic.



   On the other hand, the H + content may become too high for reduction to metallic copper alone while a large amount of copper.

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 vre is still in solution.



   In order to illustrate the effect of varying amounts of free acid, ammonium sulfate, copper sulfate and temperature, various samples of a copper solution are subjected to reducing conditions by H2 for 30 minutes at a total pressure of about 63 atm.



  The final acid is calculated assuming the product is metallic copper, with no correction for copper sulphide. The actual acid at the end of the reduction is less than the calculated value due to the corrosive attack of the acid on the apparatus used. Illustrative results are shown in Table IV.



   TABLE IV.



  Effects of the acid concentration on the reduction of coppero g / 1 final
 EMI11.1
 
 <tb> M / 1. <SEP> initial <SEP> Temp. <SEP>% <SEP> H2SO4
 <tb>
 <tb> CuSO4 <SEP> H2SO4 <SEP> (NH4) 2SO4 <SEP> C <SEP> Reduced <SEP> Cu <SEP> Found <SEP> Calc. <SEP>% <SEP> S
 <tb>
 <tb>
 <tb> 0.5 <SEP> 0.2 <SEP> 0 <SEP> 204 <SEP> 99.5 <SEP> 0.3 <SEP> 70 <SEP> 0.074
 <tb>
 <tb> 0.75 <SEP> 0.2 <SEP> 0 <SEP> 232 <SEP> 99.0 <SEP> 0.47 <SEP> 93 <SEP> 0.025
 <tb> 0.5 <SEP> 0.3 <SEP> 0 <SEP> 204 <SEP> 99.5 <SEP> 0.3 <SEP> - <SEP> 80 <SEP> 0.05
 <tb>
 <tb> 0.75 <SEP> 0.5 <SEP> 0 <SEP> 232 <SEP> 98.7 <SEP> 0.61 <SEP> 100 <SEP> 123 <SEP> 0.085
 <tb>
 <tb> 1, <SEP> 0.2 <SEP> 00 <SEP> 204 <SEP> 94.8 <SEP> 3.2 <SEP> 111 <SEP> 114 <SEP> < <SEP> 0.01
 <tb>
 <tb> 1.5 <SEP> 0.2 <SEP> 0 <SEP> 204 <SEP> 95.4 <SEP> 4.4 <SEP> 127 <SEP> 167 <SEP> 0.038
 <tb>
 <tb> 0.75 <SEP> 0,

  8 <SEP> 0 <SEP> 232 <SEP> 99.5 <SEP> 0.3 <SEP> 138 <SEP> 153 <SEP> 0, <SEP> 005 <SEP>
 <tb>
 <tb> 0.75 <SEP> 1.4 <SEP> 0 <SEP> 232 <SEP> 99.4 <SEP> 0.3 <SEP> 170 <SEP> 213 <SEP> 0.74
 <tb>
 <tb> 2, <SEP> 0.2 <SEP> 0 <SEP> 204 <SEP> 95.8 <SEP> 5.3 <SEP> 171 <SEP> 208 <SEP> < <SEP> 0.01
 <tb>
 <tb> 0.5 <SEP> 0.2 <SEP> 1 <SEP> 204 <SEP> 99.5 <SEP> 0.3 <SEP> 62 <SEP> 70 <SEP> 0.034
 <tb>
 <tb> 0.5 <SEP> 0.2 <SEP> 2 <SEP> 204 <SEP> 99.0 <SEP> 0.6 <SEP> 63 <SEP> 70 <SEP> 0.12
 <tb>
 x Tests conducted for two hours.



  It may be noted that this high content of free acid, high content of free ammonium sulfate, high temperature and prolonged time tend to increase the sulfide content of the metallic copper produced. Thus, it is preferable to avoid exceeding 17% free sulfuric acid, which is easy. However, if for some reason it is desired to operate under these conditions, the solution should be low in ammonium sulfate, and high temperature and excessive residence time should be avoided. For example, one should not exceed a temperature of about 232 for more than about 30 minutes.



   As noted, some ammonium sulfate is normally present. However, when adjusting the solution care must be taken to avoid low concentrations of NH3 and free acid, as the concentration of ammonium sulfate approaches saturation. On the other hand, the double copper-ammonium salt can be precipitated.

  <Desc / Clms Page number 12>

 



   . CONDITION OF REDUCTION.



   Any non-sulphurizing reducing gas can be used.



  Preferred reducing gases in the practice of the invention are hydrogen, carbon monoxide, and mixtures thereof. The partial pressure of the reducing gas does not have to be high to reduce the copper in these reductions. However, appreciable pressure may be necessary to reduce all of the precipitated copper oxide. Four illustrative tests are carried out in an autoclave set so that there are no leaks.



  The solution is heated to a boil and the autoclave is purged of air with steam. The vent is then closed and the autoclave is heated to the reduction temperature. The hydrogen overpressure is brought to 14 atm and the hydrogen valve is closed. The time taken for the pressure to return to the initial vapor pressure is noted. The autoclave is cooled and the residual pressure is noted. The results are shown in Table V.



   TABLE V.
 EMI12.1
 



  Splution ,. M / 1 Te Temc & Pressure Cu NH3 â2â-04, 0 C Min. Residual Remarks 1.4 - le4 218 10 1 atmos. clear metal
 EMI12.2
 
 <tb> 1.4 <SEP> - <SEP> 0.5 <SEP> 190 <SEP> 18 <SEP> " <SEP> " <SEP> "
 <tb>
 <tb> 1.5 <SEP> 1.25 <SEP> - <SEP> 190 <SEP> 23 <SEP> " <SEP> oxide <SEP> + <SEP> metal
 <tb>
 
 EMI12.3
 1,012,14 - 218 13 "St" 1 (in Gq20) - 204 150 50 no metal
 EMI12.4
 
 <tb> observed
 <tb>
 
Also shown in Table V is a test on a "reagent" grade of cuprous oxide in which no reduction occurs below 3.5 atm. Under acidic conditions, the reaction rate is high even when the partial pressure of the reducing gas is less than 1.5 atm. Under acidic conditions, cuprous oxide is soluble and therefore does not precipitate.

   However, under basic conditions and especially in the absence of ammonium sulfate, cuprous oxide precipitates and although some metal is produced, it is mixed with oxide. Therefore, under the conditions where the oxide precipitates, a reducing gas pressure greater than 3.5 atm and preferably 21 to 35 atm is desirable to obtain the oxide free metal.



   Another important factor is the temperature. Reduction can be achieved at a lower average temperature with carbon monoxide than with hydrogen. In fact, solutions of copper sulphate can be reduced by carbon monoxide at room temperature. However, to ensure a reasonable rate of reaction with CO or H2, the temperature should be above about 121.



   To illustrate the above, samples of a sulfate solution were reduced at various temperatures for 45 minutes under a partial pressure of 35 atmospheres of H2. Particular illustrative results are shown in Table VI.

  <Desc / Clms Page number 13>

 



  TABLE VI.
 EMI13.1
 
 <tb> Gas <SEP> Tempo <SEP> <SEP> C <SEP>% <SEP> Reduction.
 <tb>
 <tb>
 <tb>
 <tb>



  H2 <SEP> 204 <SEP> 100
 <tb>
 <tb>
 <tb> H2 <SEP> 175 <SEP> 85
 <tb>
 <tb>
 <tb>
 <tb> H2 <SEP> 121 <SEP> 30
 <tb>
 
For the reduction of similar sulphated liquors with hydrogen, it is best practice to use the range 177-260, the range 204-232 being generally the optimum. Sulphate solutions can be reduced with H2 at optimum temperatures and at a total pressure of about 63 atm to obtain a yield of about 100% copper in 15 minutes under acidic conditions. If free NH3 is present, the reduction is 2-4 times longer. The reduction can be achieved even faster at higher temperatures and pressures, but the decrease in reaction time is not sufficient to allow operation above about 232 - 260 and 63 atm. be economical.



   For reduction of carbonate solutions, a lower temperature is usually optimum. As the metallic copper precipitates, the free ammonia and ammonium carbonate contents of the solution both increase. If the initial solution contains a normal optimum of 130 g / l copper, and is reduced to about 93 - 177 at 63 atm, after reduction of about 60 - 70% of the. copper, the reaction rate becomes very slow, practically negligible. One reason, for example, is that the increasing content of free ammonia and ammonium carbonate causes the partial pressures of NE; and CO2 to increase, so that for a constant total pressure, the partial pressure of the reducing gas becomes too low. for a useful speed.

   In addition, the rate of reduction of the complex appears to be inversely related to the formation of free uncomplexed ammonia, which varies as the metal precipitates.



   The carbonate-amine solutions are normally obtained in etching cycles without the addition of anion. As a result, the solution is recycled to dissolve the additional copper in the next cycle. This is economically possible after only 60 - 70% of the copper has been collected in metallic form. Therefore the question of the completion of the precipitation is not as important as in the case of liquors obtained by oxidative attack of sulphides, a process in which the anion is formed.



   Yields of greater than about 60-70% in the reduction of carbonate liquors can be obtained by using lower temperatures for a longer period of time, or by using higher operating pressure. Alternatively, NH3 and CO2 can be removed by opening the autoclave to a lower total pressure and applying adequate pressure of reducing gas to complete the reduction. The escaped gases can be condensed and redissolved for reuse in the attack if desired.



   A roughly similar limit applies to the reduction by CO of acidic sulphate solutions with a high copper content which can usually be completely reduced. The CO2 produced by the reaction accumulates in the vapor phase. If allowed to build up to too great a partial pressure, it can lower that of the reducing gas and limit performance. For example, in the treatment of a molecular solution in an autoclave two-thirds full of liquid at 63 atm. you get only 90% reduction in 30 minutes, unless you eliminate

  <Desc / Clms Page number 14>

 CO2, for example by letting it escape. In ammoniacal sulphate sclutions, however, sufficient CO2 remains in solution, so that the yield is not limited for this reason.



   PROPERTIES OF THE POWDERED PRODUCT.



   The properties of the powder obtained differ according to the reducing gas used and the nature of the solution. For carbonate solutions of optimum composition, when using hydrogen alone, the average particle size of copper powder is about 325 mesh and the bulk density is usually about 1.5 g / cc. When carbon monoxide is used, a much larger powder can be obtained, a particular product having a particle size of about 100 mesh and a mass density of about 3 to 4.5 g / cc. . Mixtures of reducing gases give intermediate results.

   For sulphate solutions the powder obtained with H2 has an average size of about 200 mesh and a density of 2.5 g / cc or more, while with CO a very coarse powder or coarse powder can be obtained. pills.



   Excessive or prolonged agitation should be avoided for several reasons. For example, if the powder is allowed to form into too fine particles, i.e. particles less than about 400 mesh in total, the small particles tend to agglomerate and thus occlude or absorb impurities from the liquor. when subjected to excessive or prolonged agitation. Likewise when carbon oxide is used, excessive agitation during the period when the reduction rate is slow can result in the formation of large balls of copper containing inside the solution not. scaled down. This difficulty can be avoided to a large extent by changing the stirring speed.

   However, it is better to add the solution to avoid encountering conditions that cause these poor results.



   Precipitation of excessively fine powder can be avoided by carrying out the reduction under conditions ensuring a lower speed. This is possible by one or the other of two-variants. One is the addition of the salts described above, usually a salt of the complexing material, such as an ammonium salt of the same acid for basic conditions or of an acid forming a compatible anionic complex. acidic conditions. The other is to avoid an excessive concentration of hydrogen ions, i.e. to minimize the amount of free acid present during reduction.



   The remarkable formation of balls during prolonged agitation when using CO to reduce carbonate liquors occurs only under conditions where plaque or sheet formation is possible. This can be avoided in part by using a metal seed powder; it can also be minimized by avoiding an excessive content of foreign salts and / or free ammonia and by operating closer to the optimum conditions set out above.



   Reduction to metallic copper can be performed for any initial cupric / cupric ratio in solution. However, some control is necessary to obtain optimum results. For example, as noted in Table I, in treating ammoniacal solutions of copper carbonate containing more than the optimum of about 130 g / L total copper, some copper oxide. copper can precipitate on heating above 1770. It precipitates more copper as oxide when all copper is cuprous, its oxide being less soluble than cupric oxide. However, from solutions containing a little cupric copper the precipitate, although smaller, nevertheless contains a little CuO.

   Although, as we have seen, a metal oxide precipitate can be reduced by H2, the metal powder formed is of poor quality and the reduction is slower. In addition, the oxygen content of the copper obtained

  <Desc / Clms Page number 15>

 is higher for concentrated solutions of cupric copper. Under comparable conditions, the obtained copper powder usually contains less oxygen if the cuprous / cupric ratio is greater than about 2 when the solution is heated before reduction. Under preferred conditions, the O 2 content in the precipitated powder can be lowered to 0.001% or less.



   The cuprous to cupric ratio can be adjusted if necessary by contacting the solution with a material containing metallic copper. This product can be powdered copper or a metallic copper containing material obtained from another source. The treatment can be carried out by stirring the powder in the solution or by passing the solution through a bed of this powder or in any other suitable manner. In addition to the visible effect on reduction rate and product properties, oxide precipitation in carbonate solutions is undesirable for other reasons. Certain impurities in carbonate etchant precipitate rapidly on heating.

   They are easily removed by filtration if the precipitate of copper oxides is not too great to cause excessive loss. On the other hand, a trace of oxide precipitate appears to promote reduction to metal. As noted above, an optimum carbonate solution should not give an oxide precipitate immediately upon heating. This allows impurities to be coagulated and filtered without appreciable loss of copper: An optimum solution, however, forms a slight precipitate of cuprous oxide after about 10 to 20 minutes at the reduction temperature.



   When CO constitutes the reducing gas, the small precipitate of cuprous oxide may not appear on heating. When CO is used, there is usually some of it in the solution from previous operations. If so, some soluble cuprous carbon monoxide complex appears to be formed rather than precipitation of the carbon monoxide. 'oxide. This simplifies the heating problem. A further reduction of these solutions is easily initiated. As a result, there is a wider latitude in the composition of the solutions which can be effectively used when carrying out the reduction by carbon monoxide. The oxygen content of the final copper powder is also easily maintained well below 0.01%.



   From the foregoing, it can be deduced in summary that an initial solution must contain approximately the contents in g / l indicated in the following Table VII and must be treated under the conditions indicated.



  - TABLE VII.



  Content of adjusted copper solutions (g / 1)
 EMI15.1
 
 <tb> Carbonates <SEP> Sulphates
 <tb>
 <tb>
 <tb> intervalē¯¯¯¯¯optimum <SEP> intervalē¯¯¯optimum
 <tb>
 <tb>
 <tb> Gas <SEP> reducer <SEP> H2 <SEP> CO <SEP> H2 <SEP> CO
 <tb> used
 <tb>
 <tb>
 <tb> Copper <SEP> total <SEP> 20-200 <SEP> 130 <SEP> 130 <SEP> 20-100 <SEP> 75 <SEP> 75
 <tb>
 <tb>
 <tb> copper <SEP> 0-200 <SEP> (1) <SEP> (1) <SEP> 20-100 <SEP> (2) <SEP> (2)
 <tb>
 <tb>
 <tb> copper <SEP> 0-150- <SEP> -:

    <SEP> 20-100- <SEP> -
 <tb>
 

  <Desc / Clms Page number 16>

 
 EMI16.1
 
 <tb> NH3 <SEP> for <SEP> 10-220 <SEP> 165 <SEP> 165 <SEP> 0-220 <SEP> 75 <SEP> 65
 <tb>
 <tb>
 <tb>
 <tb> sys-
 <tb>
 <tb>
 <tb> CO2 <SEP> temes <SEP> 15-150 <SEP> 110 <SEP> 110 <SEP> - <SEP> - <SEP> -
 <tb>
 <tb>
 <tb> basi-
 <tb>
 <tb>
 <tb> his <SEP> 4 <SEP> ques (3) <SEP> - <SEP> - <SEP> - <SEP> 40-220 <SEP> 130 <SEP> 130
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> H2SO4 <SEP> free
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> systems <SEP> - <SEP> - <SEP> - <SEP> 0-170 <SEP> 0-20 <SEP> 0-20
 <tb>
 <tb>
 <tb>
 <tb> acids
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Temperature
 <tb>
 <tb>
 <tb>
 <tb> (C) <SEP> 121-260 <SEP> 177 <SEP> 149 <SEP> 121-288 <SEP> 204 <SEP> 190
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> H2 <SEP> close.
 <tb>
 <tb>
 <tb>
 <tb> part.

    <SEP> (Atm.) <SEP> 3.5-70 <SEP> 21 <SEP> 21 <SEP> 0.7-70 <SEP> 21 <SEP> 21
 <tb>
 (1) the copper / copper ratio should be greater than about 2.



  (2) The copper / cupric ratio has no influence on sulphates.



  (3) For basic solutions containing ammonium sulfate.



   Illustrative examples of the reduction of copper carbonate solutions are given below in Table VIII. In tests A and C the reducing gas is H2 supplied at an initial partial pressure of approximately 37.8 - 39.9 atm. respectively, the final partial pressures after cooling being 17.5 atm at 60 and 24.5 atm at 35 respectively.



  In Test B the gas is CO at an initial partial pressure of about 36.4 atm and a final partial pressure of 0 to about 60 due to dissolution.



   TABLE VIII.



  Reduction of copper from solution by NE) and CO first part. Reduction conditions and composition of the solution.



   Composition of the solution (g / 1)
 EMI16.2
 
 <tb> Es- <SEP> Echan- <SEP> Cu <SEP> Rendt
 <tb>
 <tb>
 <tb>
 <tb> sai <SEP> tillon <SEP> total <SEP> Cu + <SEP> NH3 <SEP> CO2 <SEP> Zn <SEP>% <SEP> Cu <SEP> Remarks
 <tb>
 <tb>
 <tb> n
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> A <SEP> head <SEP> to <SEP> 114 <SEP> 55 <SEP> 165 <SEP> 125 <SEP> 37.5 <SEP> (Heating. <SEP> until
 <tb>
 <tb>
 <tb>
 <tb> (16 <SEP> minutes
 <tb>
 <tb>
 <tb> 350 <SEP> 133 <SEP> 64 <SEP> 158 <SEP> 130 <SEP> -17 <SEP> (Residue <SEP> of <SEP> for
 <tb>
 <tb>
 <tb>
 <tb> (dre <SEP> of a <SEP> cycle
 <tb>
 <tb>
 <tb> + <SEP> 30 <SEP> min. <SEP> 92 <SEP> 84 <SEP> 143 <SEP> 96 <SEP> 19 <SEP> (previous
 <tb>
 <tb>
 <tb>
 <tb> (in <SEP> auto-
 <tb>
 <tb>
 <tb> + <SEP> 60 <SEP> min.

    <SEP> 62 <SEP> 57 <SEP> 139 <SEP> 89 <SEP> 44 <SEP> (clave
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> + <SEP> 90 <SEP> mino <SEP> 46 <SEP> 48 <SEP> 137 <SEP> 89 <SEP> 60
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> B <SEP> head <SEP> to <SEP> 122 <SEP> 52 <SEP> 181 <SEP> 127 <SEP> 31 <SEP> (heat. <SEP> until
 <tb>
 <tb>
 <tb>
 <tb> (25 <SEP> minutes.
 <tb>
 <tb>
 <tb>



  350 <SEP> 118 <SEP> 88 <SEP> 147 <SEP> 107 <SEP> 3 <SEP> (Residue <SEP> of <SEP> for <SEP>
 <tb>
 <tb>
 <tb>
 <tb> mino <SEP> $ 14 <SEP> 113 <SEP> (dre <SEP> of a <SEP> cy--
 <tb>
 <tb>
 <tb> + <SEP> 30 <SEP> min. <SEP> 98 <SEP> 75 <SEP> 148 <SEP> 113 <SEP> 20 <SEP> (key <SEP> previous
 <tb>
 <tb>
 <tb> (in <SEP> auto-
 <tb>
 <tb>
 <tb>
 <tb> + <SEP> 60 <SEP> mine <SEP> 74 <SEP> 63 <SEP> 150 <SEP> 123 <SEP> 39 <SEP> (clave.
 <tb>
 

  <Desc / Clms Page number 17>

 
 EMI17.1
 
 <tb>



  Is- <SEP> Echan- <SEP> Cu <SEP> Returns
 <tb>
 <tb>
 <tb>
 <tb> sai <SEP> tillon <SEP> total <SEP> Cu + <SEP> NH3 <SEP> CO2 <SEP> Zn <SEP>% <SEP> Or <SEP> Remarks
 <tb>
 <tb>
 <tb> n
 <tb>
 <tb>
 <tb>
 <tb> + <SEP> 90 <SEP> min. <SEP> 56 <SEP> 52 <SEP> 146 <SEP> 118 <SEP> 54
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> C <SEP> head <SEP> to <SEP> 128 <SEP> 83 <SEP> 186 <SEP> 127 <SEP> 23 <SEP> (heat. <SEP> 28 <SEP> min. <SEP>
 <tb>
 <tb>
 <tb>



  (H2 <SEP> under <SEP> 13.5
 <tb>
 <tb>
 <tb> 350 <SEP> 142 <SEP> 93 <SEP> 168 <SEP> 124 <SEP> -it <SEP> (1 <SEP> min. <SEP> for
 <tb>
 <tb>
 <tb> - (hold <SEP> 63
 <tb>
 <tb>
 <tb> + <SEP> 58 <SEP> min. <SEP> 66 <SEP> 59 <SEP> 141 <SEP> 77 <SEP> 48 <SEP> (atm.
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>



  +104 <SEP> min. <SEP> 37 <SEP> 34 <SEP> 141 <SEP> 64 <SEP> 71
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> +141 <SEP> min. <SEP> 20 <SEP> 14 <SEP> 113 <SEP> 54 <SEP> 84
 <tb>
 Part two Handling (1) and analysis of copper powder.
 EMI17.2
 
 <tb>



  Test <SEP> No <SEP> Size <SEP> of <SEP> product <SEP> A <SEP> B <SEP> C
 <tb>
 <tb>
 <tb> A <SEP> B <SEP> C <SEP> (size <SEP> of <SEP> sieve) <SEP>% <SEP> in <SEP> weight
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Densi- <SEP> 1.61 <SEP> 2.52 <SEP> 2.54
 <tb>
 <tb>
 <tb> tee
 <tb>
 <tb>
 <tb> g / cc
 <tb>
 <tb>
 <tb> Flow
 <tb>
 <tb>
 <tb>
 <tb> Sec /
 <tb>
 <tb>
 <tb> 50 <SEP> go <SEP> 30 <SEP> 34 <SEP> 35 <SEP> +60 <SEP> 0 <SEP> 5 <SEP> 29
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>% <SEP> Zn <SEP> 0 <SEP> 0 <SEP> - <SEP> -60 + 80 <SEP> 1 <SEP> 47 <SEP> 21
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>% <SEP> Pb <SEP> 0.002 <SEP> 0.001 <SEP> 0.003 <SEP> -80 + 100 <SEP> 10 <SEP> 28 <SEP> 15
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>% <SEP> Sn <SEP> 0.03 <SEP> 0.03 <SEP> 0.004 <SEP> -100 + 140 <SEP> 18 <SEP> 14 <SEP> 15
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>% <SEP> Fe <SEP> 0.014 <SEP> 0,

  004 <SEP> - <SEP> -140 + 200 <SEP> 20 <SEP> 4 <SEP> 13
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>% <SEP> Neither <SEP> 0 <SEP> 0.002 <SEP> 0 <SEP> -200 + 230 <SEP> 8 <SEP> 1 <SEP> 4
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>% <SEP> 02 <SEP> 0.03 <SEP> 0, <SEP> 03 <SEP> 0, <SEP> 03 <SEP> -230 + 270 <SEP> 6 <SEP> tr <SEP> 2
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>% <SEP> Cu <SEP> 99.90 <SEP> 99.92 <SEP> 99.93 <SEP> -270 + 325 <SEP> 10 <SEP> tr- <SEP> 1
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> -325 <SEP> 27 <SEP> tr <SEP> tr
 <tb>
 (1) In each test the copper powder produced is clear and practically free of oxygen when filtered from the spent solution. Exposure to air during filtration oxidizes the powder to a dark red color.

   It is then washed successively with a 0.5% NH3, H2SO4, 5.0% solution of 10% aguous acetic acid and water, then dried in a heated drum with the addition of a slight current of H2. After 20 minutes, the temperature is 1000 and the water has evaporated. Heating is continued for a further 10 minutes at a temperature of 260. Water is poured over the drum to cool it to 26, the H2 is turned off and the drum is opened. The resulting powder is analyzed.



   Illustrative examples of reduction of solutions of copper sulphates obtained by attack of concentrates of sulphurous ores are given in Table IX.

  <Desc / Clms Page number 18>

 
TABLE IX.



  Copper powder from sulphate solutions.
 EMI18.1
 
 <tb>



  Analysis <SEP>% <SEP> or <SEP> g / 1.
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>



  Liters <SEP> g <SEP> Or <SEP> Fe <SEP> H2 <SEP> SO4 <SEP> S <SEP> O2 <SEP> Yield
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> free <SEP> total <SEP>%
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Liquor
 <tb>
 <tb>
 attack <tb> <SEP> 1.6 <SEP> 42 <SEP> 72 <SEP> 43 <SEP> 82
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Liquor
 <tb>
 <tb>
 <tb> residual <SEP> 1.1 <SEP> 2.2 <SEP> 57 <SEP> 92 <SEP> 67
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Powder <SEP> of
 <tb>
 <tb>
 <tb> Cu <SEP> 24 <SEP> 99.90% <SEP> 0.027% <SEP> - <SEP> 0.06% <SEP> 0.01% <SEP> 96.3
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Liquor <SEP> #
 <tb>
 <tb>
 attack <tb> <SEP> 0.65 <SEP> 92 <SEP> 17 <SEP> 89 <SEP> 91
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Liquor
 <tb>
 <tb>
 <tb> residual <SEP> 1, <SEP> 04 <SEP> 0,

    <SEP> 3 <SEP> 16 <SEP> 138 <SEP> 55
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Powder
 <tb>
 <tb>
 <tb> from <SEP> Or <SEP> 40 <SEP> 99.91% <SEP> 0.015% <SEP> - <SEP> 0.005% <SEP> 0.03% <SEP> 99.5
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Liquor
 <tb>
 <tb>
 <tb> attack ', <SEP> 1.1 <SEP> 76 <SEP> # 22 <SEP> 86 <SEP> 74 <SEP> + <SEP> log <SEP> 99.9% <SEP> Cu
 <tb>
 <tb>
 <tb> powder <SEP> like
 <tb>
 <tb>
 <tb>
 <tb> germs
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Liquor
 <tb>
 <tb>
 <tb> residual-
 <tb>
 <tb>
 <tb>
 <tb> the <SEP> 1.18 <SEP> 0.2 <SEP> # 21 <SEP> 75 <SEP> 72
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Powder <SEP> of
 <tb>
 <tb>
 <tb>
 <tb> Cu <SEP> 75 <SEP> 99.92% <SEP> 0.008% <SEP> - <SEP> 0.02% <SEP> 0.02% <SEP> 99.8
 <tb>
 Note: Etching liquors obtained by oxidative attack of chalcopyrite concentrates.

   Reduction by H3 at 2040 and under 56 atm (total) for 30 minutes. The powders obtained are washed in water and dried in a hydrogen atmosphere before analysis. The volumes of residual liquor indicated include some wash water.



   REDUCTION OF NICKEL.



   Metallic nickel is normally obtained from sulphide, oxidized or silicate ores. The present invention can be put into practice on any of the attack solutions of these ores or their enrichment or pyrometallurgical concentrates. Nickel is usually found only in sulphated or carbonated solutions, the former usually containing, and the latter always, free ammonia.



  As in the case of copper, other anions can be present in ammoniacal solutions, except those which form an undissociated complex with the metal or which react with the reducing gas. In acidic solution, fluosilicate, acetate or other anions can be used which give adequate solubility of nickel if they do not react with the reducing gas. Strong monoacids, such as nitric or hydrochloric acid, are also not industrially useful, although they can be made active in ammoniacal solutions.

  <Desc / Clms Page number 19>

 



   The practice of the present invention will be described for nickel solutions containing sulfates and / or carbonates with ammonia as the particular amine, both as complex ions with nickel and in the form of ammonia. ammonium ions. The first main phase is still the adjustment of the composition of the solution to approximately the optimum conditions.
 EMI19.1
 adjustment of the goM2osition of the solution.



   Nickel is soluble in water as sulfates up to about 90-100 g / 1 Ni under ambient conditions. Its solubility is somewhat reduced by the presence of appreciable amounts of free sulfuric acid, but it increases with temperature. Nickel is soluble to approximately the same degree in carbonate solutions if sufficient free ammonia is present. The solution should therefore ordinarily contain less than about 100 g / l of nickel to avoid precipitation before reduction. Otherwise, it must be prepared and handled at increased temperature. Solutions containing less than about 10 g / l Ni, although technically usable, are usually not economical.



   The concentrations of nickel in the solution do not appear to significantly affect the reduction rate under optimum conditions.



  To illustrate this fact, a series of solutions containing varying amounts of nickel and about 2 mol are suspended. ammonia per mol of nickel with about 100 g / l of nickel seed powder and the suspension is reduced with hydrogen to about 177 under a total pressure of 35 atm. Particular results which show the time required to precipitate all of the metal from solutions containing various amounts of nickel are shown in Table X. It is seen that the time required is roughly proportional to the nickel initially present.



   PAINTINGS.



  Effect of nickel concentration on reduction time.
 EMI19.2
 
 <tb>



  Nickel <SEP> (g / 1.) <SEP> 80 <SEP> 63 <SEP> 40 <SEP> 18 <SEP> 7
 <tb>
 <tb> Time <SEP> of <SEP> reduction <SEP> (min,) <SEP> 60 <SEP> 40 <SEP> 25 <SEP> 15 <SEP> 7
 <tb>
 
An adjusted ammonia solution of nickel sulphate, containing ammonia-nickel complex ions, obtained either from an ammoniacal attack liquor, or from an acidic attack liquor neutralized with ammonia, or from a solution of sulphates ammonium-nickel in aqueous ammonia, must contain both free ammonia and ammonium sulphate for best results o Even if the solution does not initially contain ammonium sulphate. 'ammonium,

   sulfuric acid and ammonia are released from the complex during reduction and form ammonium sulphate
Illustrative examples of the effect of varying ammonium sulfate and free ammonia concentrations on the reduction of nickel from these solutions are shown in Table XI.

  <Desc / Clms Page number 20>

 



   TABLE XI.



  Effect of free NH3 and (NH4) 2SO4 on nickel reduction. from sulphate solutions.
 EMI20.1
 
 <tb>



  Content <SEP> initial <SEP> of <SEP> Conditions <SEP> of <SEP> the <SEP> Neither <SEP> product
 <tb>
 <tb>
 <tb> the <SEP> solution <SEP> reaction
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Neither <SEP> NH4 <SEP> NH3 <SEP> C <SEP> Atm. <SEP> Gas <SEP> Time <SEP> Yield
 <tb>
 <tb>
 <tb>
 <tb> 4 <SEP> 3 <SEP> total <SEP> (Min.) <SEP>%
 <tb>
 <tb>
 <tb> free
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 1.35 <SEP> 2.7 <SEP> 2.8 <SEP> 232 <SEP> 56 <SEP> H2 <SEP> 60 <SEP> 98.6
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 0.89 <SEP> 1.8 <SEP> 4.65 <SEP> 232 <SEP> 56 <SEP> H2 <SEP> 60 <SEP> 76.3
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 0.89 <SEP> 1.8 <SEP> (1) <SEP> 4.65 <SEP> 232 <SEP> 56 <SEP> H2 <SEP> 60 <SEP> 55.6
 <tb>
 
 EMI20.2
 
 <tb> (2) <SEP> 1,2 <SEP> 0 <SEP> 1,2 <SEP> 204 <SEP> 49 <SEP> H2 <SEP> 60 <SEP> (3) <SEP> 60
 <tb>
 
 EMI20.3
 
 <tb> 1.2 <SEP> 0 <SEP> 2,

  4 <SEP> 204 <SEP> 50.4 <SEP> H2 <SEP> 10 <SEP> 100
 <tb>
 <tb> 1.2 <SEP> 0 <SEP> 3.6 <SEP> 204 <SEP> 525 <SEP> H2 <SEP> 15 <SEP> 100
 <tb>
 <tb> 1.2 <SEP> 0 <SEP> 4.8 <SEP> 204 <SEP> 56 <SEP> H2 <SEP> 30 <SEP> 100
 <tb>
 <tb> 1.35 <SEP> 0 <SEP> (4) <SEP> 2.8 <SEP> 232 <SEP> 56 <SEP> H2 <SEP> 60 <SEP> 98.3
 <tb>
 <tb> 1.35 <SEP> 2.7 <SEP> 2.8 <SEP> 232 <SEP> 56 <SEP> H2 <SEP> 60 <SEP> 98.6
 <tb>
 <tb> 1.35 <SEP> 4.5 <SEP> 2.8 <SEP> 232 <SEP> 56 <SEP> H2 <SEP> 60 <SEP> 92.6
 <tb>
 <tb> 1.35 <SEP> 6.3 <SEP> 2.8 <SEP> 232 <SEP> 56 <SEP> H2 <SEP> 60 <SEP> 84.5
 <tb> 1.35 <SEP> 0 <SEP> 4.65 <SEP> 232 <SEP> 56 <SEP> H2 <SEP> 60 <SEP> 90.0
 <tb>
 <tb> 1.35 <SEP> 1.8 <SEP> 4.65 <SEP> 232 <SEP> 56 <SEP> H2 <SEP> 60 <SEP> 76.3
 <tb>
 <tb>
 <tb> 1.35.

    <SEP> 3.0 <SEP> 4.65 <SEP> 232 <SEP> 56 <SEP> H2 <SEP> 60 <SEP> 34.5
 <tb> 1.35 <SEP> 4.0 <SEP> 4.65 <SEP> 232 <SEP> 56 <SEP> H2 <SEP> 60 <SEP> 0
 <tb>
 Note - (1) Plus 7 atm of partial pressure when cold = about 5 M / 1 (2) In tests 4-7, about 100 g / 1 of nickel powder are suspended in the solution as seeds.



   (3) The final solution contains approximately 4% free H2SO4.



   (4) Final free NH3 is only about 0.12 M / 1 or 0.2%.



   From these and similar tests it can be assumed in principle: (a) that even with seeds, a NH3 / Ni ratio greater than 1 is necessary for good reduction speeds, but higher ratios at about 2.0 - 211 tend to decrease in speed;

   (b) that a good NH3 / Ni ratio of about 1.8 - 2.0 increasing the (NH4) 2SO4 content has no detrimental effect on the speed until the NH4 + / Ni ratio reaches about 3, above which the speed decreases; and (c) that with higher NH3 / Ni ratios, i.e. above about 2.1, an NH4 + / Ni ratio as low as 2 can have an adverse effect on speed.

  <Desc / Clms Page number 21>

 
Nickel tends to be deposited on walls and other damp parts when reduction is carried out on solutions too concentrated in NH3 or ammonium salts. However, the addition of nickel powder from a previous reduction;

   as in tests 4 - 7 of Table XI. provides enough seeds to avoid this deposit This also shortens the reaction period o It seems that optimum speeds are obtained for free NH3 / Ni ratios of about 2, although ratios of about 1.4-4.0 can be used. In the test in which the NE / Ni molecular ratio is reduced to only 1, the reduction is interrupted when the solution reaches about 4% free acid although it contains: still 28 g / 1 of nickel . The adjusted solution should have a higher ratio to avoid reaching this acid content before more of the nickel has been reduced, or ammonia is added during the reduction.



   Illustrative results obtained during the treatment of various solutions with insufficient ammonia content and containing ammonium sulphate with hydrogen at 204 - 2320 C and a total pressure of about 63 atm are summarized in the table. XII. The reduction is continued until the reduction of Ni becomes negligible, which is determined by the variation in acidity. In the table, the final acidity corresponds with the unreduced nickel.



     TABLE XII.



  Effect of final acidity on reduction of sulphate solutions.
 EMI21.1
 
 <tb>



  Content <SEP> final <SEP> in <SEP> pH <SEP> Content <SEP> final <SEP> in
 <tb> H + <SEP> (acid <SEP> free <SEP>%) <SEP> final <SEP> NI <SEP> (g / l)
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 0.1 <SEP> 1.8 <SEP> 0.5
 <tb>
 <tb>
 <tb> 0.33 <SEP> 1,2 <SEP> 0.25
 <tb>
 <tb>
 <tb> 0.35 <SEP> 1,2 <SEP> 1.30
 <tb>
 <tb>
 <tb> 0.5 <SEP> 1,2 <SEP> 0.70
 <tb>
 <tb>
 <tb> 0.6 <SEP> 0.9 <SEP> 0.15
 <tb>
 <tb>
 <tb> 0.9 <SEP> 0.30
 <tb>
 <tb>
 <tb> 0.9 <SEP> 1.45
 <tb>
 <tb>
 <tb> 1.0 <SEP> 4.0
 <tb>
 <tb>
 <tb> 2.5 <SEP> 8.0
 <tb>
 <tb>
 <tb> 3.5 <SEP> 11.7
 <tb>
 <tb>
 <tb> 3.8 <SEP> 28.0
 <tb>
 
Nickel cannot be reduced to an appreciable degree from an aqueous sulfate solution containing about 5% or more free sulfuric acid. -However, assuming that from a practical point of view a complete reduction is obtained when the Ni content is reduced to less than about 1 g / l.

   complete reduction is not obtained when more than about 0.9% free acid is present. Reduction tests of a solution of nickel sulphate which does not contain free acid, free ammonia or ammonium sulphate give a reaction interrupted at pH 1.8-2 after formation of a trace of acid. By adding ammonium sulphate or even sulfuric acid, the reduction can be carried out in the absence of free ammonia. Table XIII shows the effect of

  <Desc / Clms Page number 22>

 
 EMI22.1
 varying amounts of E2S0 and (NH4) 2SO4 All the tests are carried out for one hour at 204 under 70 atm of total pressure using hydrogen. 1 M / L nickel sulfate is present and 10 g / L of seed nickel is added.



   TABLE XIII
 EMI22.2
 
 <tb> Head <SEP> Filtrate
 <tb>
 
 EMI22.3
 H2S04 (xi) (NH4) 2S04 (M / 1) pH xzso4 (g / 1) H2SO4
 EMI22.4
 
 <tb> product <SEP> g / 1
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 9.60 <SEP> - <SEP> 1.28 <SEP> 5.72 <SEP> -3.88 <SEP> witness
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 7.53 <SEP> - <SEP> 1.50 <SEP> 7.22 <SEP> +3.57
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 14.5 <SEP> - <SEP> 1.23 <SEP> 13.2 <SEP> +2.6
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 16.0 <SEP> - <SEP> 1.10 <SEP> 14.4 <SEP> +2.3
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 0.57 <SEP> 0.2 <SEP> 1.08 <SEP> 15.4 <SEP> +18.7
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 0.23 <SEP> 0.5 <SEP> 0.84 <SEP> 29.0 <SEP> +32.7
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 0.23 <SEP> 1.0 <SEP> 0.70 <SEP> 37.6 <SEP> +41.3
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 5.85 <SEP> 0.2 <SEP> 1.20 <SEP> 16.6 <SEP> +14,

  6
 <tb>
 The control test is carried out to determine the quantity of sulfuric acid consumed by corrosion of the autoclave. This amount of 3.88 g / L is added to the analysis of the filtrate in each run to determine the total amount of acid produced.



   The results indicate that the sulfate ions added as ammonium sulfate or sulfuric acid allow reduction to continue to a high free acid content of the solution before it ceases. It is believed that an anionic nickel complex such as Ni (SO4) 2- forms and this allows the reduction to continue.



   However, in acidic solution, the sulphate ions will change to bisulphate ions which apparently do not form a complex, and as a result the reaction stops. The acidity up to which the reaction occurs in the absence of free ammonia depends on the concentration of sulfate ions.



   In ammoniacal solution, the presence of a little ammonium sulphate is also useful. In the absence of ammonium sulphate, on addition of NH3 to a solution of nickel sulphate, a small amount of hydroxide may precipitate. A further addition of ammonia redissolves this precipitate. For these solutions, the NH3 / Ni molecular ratio is reduced to about 2 when at least about 0.5 M / L ammonium sulfate is present. As noted above, however, an excessive amount should be avoided.



   It has been noted that the optimum rate of reductions is obtained for solutions having an initial NE / Ni molecular ratio of about 2. The reduction of solutions having about this ratio also produces dense nickel powder. When the initial ratio exceeds about 4 or when the ammonium sulphate concentration exceeds about 2N, deposits sometimes occur even when germs are used. When

  <Desc / Clms Page number 23>

 The reduction in acidic solution is carried out especially with a minimum initial concentration of ammonium sulfate, and gradual addition of ammonia to prevent reaching a terminal acid content, the nickel powder produced must be very fine. It can form spongy agglomerates by prolonged agitation.

   Under these conditions, the seed powder is not necessary and if it is present it has little advantageous effect.
When a solution initially containing 2 molecules of ammonia per mol of nickel is reduced by hydrogen, the following reaction represents the total result
 EMI23.1
 Ni (NH3) 2S04 + H2 ###) - (NE,) 25 4 + Ni Under these conditions, the ammonia liberated from the complex combines with the sulfuric acid formed by the reduction to give ammonium sulfate, theo - hardly without modification of the pH. However, good results can be obtained when the NH3 / Ni ratio is about 1.4 - 4. With higher ammonia contents, the vapor pressure is increased and for the same total pressure the partial pressure of the gas. reducer is decreased.



  For this reason and because of the deleterious effect of the free ammonia, the reaction rate is consequently reduced. For ratios less than about 1.5 especially for concentrated solutions, reduction of nickel makes the solution too acidic for completion of the solution.



   As noted, some ammonium sulfate should be present. However, when adjusting the solution, care must be taken to avoid low NH3 concentrations and low free acid concentrations as the ammonium sulfate concentration approaches saturation. On the other hand, the nickel-ammonium double salt can precipitate.



   When working with carbonate solutions, the same initial levels of free ammonia and ammonium carbonate are desirable.



  However, one should note a precaution. Carbon dioxide vapor pressure must be allowed. This is a further reason why it is undesirable to decrease the NH3 / Ni molecular ratio too much below about 2.



   CONDITIONS OF REDUCTION.



   In the reduction of nickel, the use of carbon monoxide as a reducing gas is limited. In ammoniacal solution at reduction temperatures, carbonyl nickel is formed. Opening the autoclave not only results in the loss of nickel, but the carbonyl compound is dangerous. Although in acidic solution difficulties in ventilation do not arise, carbonyl is not easily converted into a satisfactory powder and it is still preferable to use hydrogen.



   In order to obtain the reduction economically, not only must the solution have the optimum composition, but also the conditions of temperature, partial pressure of the reducing gas and degree of agitation must be controlled. Each of these variables significantly affects the rate of reaction. The increase in the temperature and the pressure of reducing gas as well as the use of agitation decreases the reaction time but increases not only the direct operating expenses, but also the requirements of the strength of the apparatus.



  The optimum conditions are therefore determined by an economic equilibrium.



  This is possible by increasing the temperature and the degree of agitation until the savings obtained by the reduction in processing time and the volume of equipment required no longer exceed the increase in costs. operative.

  <Desc / Clms Page number 24>

 



   The function of agitation is to ensure a reasonable uniform dispersion in the solution of the reducing gas and the pulverized metallic nickel, both seed, if used, and produced when formed. To illustrate the effect of modifying the agitation, reduction of an optimum solution is achieved using 100 g / l of 1700 seeds using 24.5 atm of H2 in a 3.78 liter autoclave. equipped with an agitator. The time required for the reduction to 0.1 g / l of Ni is measured at different speeds of the stirrer. Specific results are shown in Table XIV.



   TABLE XIV.
 EMI24.1
 
 <tb>



  Speed <SEP> of <SEP> the agitator <SEP> Minutes <SEP> for <SEP> a <SEP> reduction
 <tb> T / minute <SEP> complete
 <tb>
 <tb>
 <tb> 550 <SEP> 80
 <tb>
 <tb> 730 <SEP> 40
 <tb>
 <tb> 900 <SEP> 35
 <tb>
 Although the degree of agitation is difficult to define, it can be seen, however, that the higher agitation speed does not correspond to a commensurate benefit. Under acidic conditions, agitator speed is more critical than in basic conditions in reducing nickel.



  As noted above, excessive agitation tends to form agglomerates of fine, low density pulverized products.



   The temperature and pressure conditions are not easily debatable independently. Moreover, they both depend on the composition of the solution. By way of illustration, an ammoniacal solution of nickel sulphate containing about 1.2 mol of Ni / 1 and 5 M free NH3 per mol of Ni is reduced with hydrogen, using about 100 g / 1 of powder of seeding nickel. The other conditions then being approximately constant it is found that at about 166-170 by increasing the total pressure by increasing the partial pressure of hydrogen, the yield obtained is increased in about 20 minutes from 0 to 35 atm if the partial pressure is negligible, at about 15-20% at about 42 atm, 80 - 85% at 49 atm, but only 90% at about 63 atm.



  Economics indicate that the use of a higher total pressure increases expenses too rapidly to be profitable. However, when reducing a solution containing only 2M NH3 / Ni M to about 14 atm of H2 partial pressure, and about 149, the reduction proceeds at a low rate. At about 177 the speed is approximately tripled, but at about 204 it is only about four times faster. Thus, increasing the temperature above 149 and maintaining the NH3 / Ni ratio at about 2 is more important for the rate increase than increasing the partial pressure of H2, but under conditions. unfavorable conditions, increasing the partial pressure is helpful.

   Tests on a nickel solution were carried out using the same procedure as in Table V, in which a partial pressure of 14 atm H2 was established and the reaction time of H2 recorded. The results are shown in Table XV below.

  <Desc / Clms Page number 25>

 



  TABLE XV.
 EMI25.1
 
 <tb>



  Solution <SEP> M / 1 <SEP> Germs <SEP> Tempo <SEP> Time. <SEP> Pressures <SEP> RemarNiSO <SEP> NH3 <SEP> (NH4) 2SO4 <SEP> (g / 1) <SEP> (C) <SEP> (Min.) <SEP> residual- <SEP> ques
 <tb> the
 <tb>
 <tb>
 <tb> 0.72 <SEP> 1.4 <SEP> 0.36 <SEP> 0 <SEP> 190 <SEP> 230 <SEP> 1 <SEP> atm <SEP> (sulfate <SEP> basic <SEP> of <SEP> Ni)
 <tb>
 <tb> 1 <SEP> 2 <SEP> 0.5 <SEP> 0 <SEP> 220 <SEP> 96 <SEP> " <SEP> 95% <SEP> Neither
 <tb>
 <tb> 1 <SEP> 2 <SEP> 1.5 <SEP> 50 <SEP> 190 <SEP> 146 <SEP> " <SEP> 98.5% <SEP> Neither
 <tb>
 <tb> 1 <SEP> 2 <SEP> 1.5 <SEP> 50 <SEP> 425 <SEP> 86 <SEP> " <SEP> 95 <SEP>% <SEP> Neither
 <tb>
 
In the first test the reduction does not take place below 5.6 atm of partial pressure. In the second test, a more concentrated solution of the same composition is largely reduced to metal at a higher temperature.

   In the second and the other tests, the metallic nickel is not free from oxide. The germs have a useful effect despite the increase in ammonium sulfate and the reaction is faster at the higher temperature. Although reduction at a reasonable rate is obtained at a partial pressure of less than 1.05 atm, to obtain an oxide free metal a higher partial pressure of at least 3.0 atm, and preferably 21. at 31 atm is desirable. Of course, if the reduction is carried out on solutions containing free acid, there is no danger of contamination by the oxide, even with partial pressures below 1 atm.



   The reduction of ammoniacal sulphate and carbonate solutions is carried out under similar optimum conditions, except that ammoniacal solutions exert higher vapor pressures. Therefore, temperatures significantly above about 177 ° C should be avoided. It is also desirable to limit the initial nickel concentration in the carbonate to about 70 g / l if it is not intended to operate. a pressure greater than about 63 atm.



   Also preferably, even when treating a solution of optimum composition, a seed powder should be suspended therein.



  In general, 5 to 100 g / l should be used depending on the size and activity of the seed powder. The sprouts must have a low density, preferably less than 1.



   Although the sulphate and carbonate solutions have been described by way of illustration, other anions may be present. As the corresponding acids may have different strengths from sulfuric acid, it is important to consider the final conditions not from the point of view of the percentage of free acid, but of free hydrogen ions, which is usually expressed by the pH. However, the free acid content can be so high that the pH value, logarithmic function, does not highlight the differences in conditions. In the present description, this factor has therefore been defined by the concentrations of hydrogen ions equivalent to those found in solutions with a given content of free sulfuric acid.



   In summary, for optimum nickel reduction, certain initial conditions are desirable. However, for a reduction to less than 1 g / l the final conditions are critical. The initial conditions can be adjusted to produce the desired final conditions, as well as to allow initiation and reduction, and often is done. Or, other adjustments can be made during the reduction. We can summarize these limitations for illustrative cases in Table XVI

  <Desc / Clms Page number 26>

 below. The "optimum" columns indicate conditions giving residual nickel concentrations of g / l or less.



     TABLE XVI.



   Adjusted ammonia solutions Adjusted acid solutions.
 EMI26.1
 
 <tb>



  Carbonate <SEP> Sulphate <SEP> Sulphate
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> inter- <SEP> optimum <SEP> inter- <SEP> optimum <SEP> inter- <SEP> optimum
 <tb>
 <tb>
 <tb> valle <SEP> valle <SEP> valle
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Content <SEP> ini- <SEP> 10-100 <SEP> 65-70 <SEP> 10-135 <SEP> 80 <SEP> 10-100 <SEP> 70
 <tb>
 <tb>
 <tb> tiale <SEP> in
 <tb>
 <tb>
 <tb>
 <tb> Neither <SEP> (g / 1)
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Report <SEP> 1.5-8 <SEP> 1.8-2.2 <SEP> 1.5-8 <SEP> 1.8-2.2 <SEP> -
 <tb>
 <tb>
 <tb>
 <tb> molecular
 <tb>
 <tb>
 <tb> initial
 <tb>
 <tb>
 <tb>
 <tb> NH3 / Ni
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Content <SEP> ini- <SEP> 0.3 <SEP> 0.5-1 <SEP> 0.3 <SEP> 0.5-1 <SEP> 0.3 <SEP> 0.5-1
 <tb>
 <tb>
 <tb>
 <tb> tiale <SEP> in <SEP> salts
 <tb>
 <tb>
 ammonium <tb>
 <tb>
 <tb>
 <tb> (M / 1)

  
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Content <SEP> fina- <SEP> - <SEP> - <SEP> 0.5 <SEP> 0-0.5 <SEP> 0.5 <SEP> 0-0.5
 <tb>
 <tb>
 <tb>
 <tb> the <SEP> in <SEP> H2SO4-
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> free <SEP> (% <SEP> p / v)
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Temperature <SEP> 121-260 <SEP> 177 <SEP> 149 <SEP> 204 <SEP> 149 <SEP> 177-232
 <tb>
 <tb>
 <tb> re <SEP> initial
 <tb>
 <tb>
 <tb> C
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Pressure <SEP> by- <SEP> 3.5 <SEP> - <SEP> 3.5 <SEP> - <SEP> 0.70 <SEP> -
 <tb>
 <tb>
 <tb> tielle <SEP> minimum
 <tb>
 <tb>
 <tb>
 <tb> from <SEP> gas <SEP> reducer
 <tb>
 <tb>
 <tb>
 <tb> (atm-H2)
 <tb>
 
Two ammoniacal attack liquors are treated from a copper-nickel-cobalt ore to remove most of the copper and neutralize it to pH 5,

  5 with sulfuric acid to precipitate nickel in the form of crystals of nickel-ammonium sulphates. The crystals of the first liquor which contain more copper and cobalt are washed thoroughly to remove the thionates. Samples were dissolved with 3 mol NH3 per mol nickel at 80 g / 1 Ni and reduced to 225 G under a pressure of 28 atm H2 for 30 minutes. The first sample is reduced in the presence of commercial nickel seed powder and successive samples of the powder from the previous run are used as the seed.

   A sample of each metal obtained is taken and each sample is washed with alcohol, then with ether and dried in a water bath and analyzed.
The crystals of the second liquor are only subjected to a slight washing and consequently thionates are still present. When dissolved and reduced as described above, the metallic nickel produced contains sulfur. However, after heating to 4000 in a hydrogen atmosphere, the sulfur is removed.

  <Desc / Clms Page number 27>

 
The powder analyzes of these tests are given in Table XVII.



   TABLE XVII.
 EMI27.1
 
 <tb>



  Product <SEP>% <SEP> germ <SEP>% <SEP> Neither <SEP>% <SEP> Or <SEP> + <SEP> Co <SEP>% Fe <SEP>% <SEP> S
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Germ <SEP> 100 <SEP> 99.59 <SEP> 0.62 <SEP> 0.33 <SEP> 0.022
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> First <SEP> test
 <tb>
 <tb> first <SEP> solu-
 <tb>
 <tb> tion <SEP> 55 <SEP> 98.84 <SEP> 0.85 <SEP> 0, <SEP> 009 <SEP> < <SEP> 0.01
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Second <SEP> test
 <tb>
 <tb> first <SEP> solu-
 <tb>
 <tb> tion <SEP> 40 <SEP> 98.84 <SEP> 0.72 <SEP> 0.008 <SEP> <0.01
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Third <SEP> test
 <tb>
 <tb> first <SEP> solu-
 <tb>
 <tb> tion <SEP> 32 <SEP> 99.38 <SEP> 0.71 <SEP> 0.008 <SEP> <0.01
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Second <SEP> solu- <SEP> x
 <tb>
 <tb> tion <SEP> 0 <SEP> 99.68 <SEP> 0.17 <SEP> 0.005 <SEP> 0,

  14
 <tb>
 <tb>
 <tb>
 <tb> Second <SEP> solu-
 <tb>
 <tb>
 <tb> tion <SEP> H2 <SEP> dried <SEP> 99.81 <SEP> 0.17 <SEP> 0.008 <SEP> < <SEP> 0.01
 <tb>
 * Seeding powder from previous cycles under identical conditions
Spectrographic examination shows that no impurities are present above 0.001-0.01%. Apart from other gas-reducible metals, the nickel produced contains less than 0.1% of total impurities. Even iron in germs is largely removed.



   REDUCTION OF COBALT.



   Co is normally obtained from sulphide, sulphurous-arsenide or oxidized ores. These can be attacked by various methods to dissolve the cobalt. An ammoniacal carbonate or sulfate solution or acidic sulfate solutions can be obtained. In ammoniacal solution, any other anion can be present except those which, like cyanide, form a practically non-reducible complex, or which, like permanganate, react with the reducing gas. Some, such as sulfates, are preferable to others, such as carbonates, due to their higher solubility. In addition, as will be seen below, the terminal acidity below which the cobalt salts can be reduced to metal is low.

   An ammoniacal cobalt sulfate system will most commonly be encountered in industrial practice and hence will be taken as illustration for the present description.



   Cobaltous sulfate is soluble in both acidic and ammoniacal solutions of suitable composition up to about 120 g / 1 Co at ambient conditions. Under neutral and slightly acidic conditions, when ammonium sulfate is present in sufficient quantity, the double salt can be precipitated. This is another reason for preferring basic conditions. In ammoniacal solutions containing free NH3, basic sulfate precipitates for NH3 / Co molecular ratios of less than 3, unless a sufficient amount of ammonium sulfate is present.



  Although this is possible for economic reasons, it is seldom desirable to process liquors containing less than 4 g / 1 Co.

  <Desc / Clms Page number 28>

 COBALTIC REDUCTION.



  Cobalt is more easily oxidized in the trivalent state than ni-
 EMI28.1
 ckel. In addition, the "amine" cobalt sulfate (Go (NH) 6) z (S0) 3, 2H20 is precipitated by strong oxidation of strongly ammoniacal solutions. This process can sometimes be used to separate cobalt either from other gas-reducible metals or from dilute solutions.

   However, if it is suspended in water or in dilute ammoniacal solution, it is reduced by hydrogen to 149 - 232, cobalt and ammonium sulphate are obtained o Only a slight reduction or zero of these cobaltic amines below about 149, some reduction is obtained at 160 - 165 and a complete reduction can be obtained for about half an hour above about 188 - 190 if conditions are otherwise correct. Seeding with pulverized cobalt according to the aforementioned process is in this case highly desirable. If the "free" ammonia exceeds about 3M / L, sufficient hydrogen is needed to produce a total pressure greater than about 51 atm at 204.

   Due to the high partial pressure of ammonia which increases with the reduction, the partial pressure of hydrogen can be reduced to less than 3.5 atm.



  A minimum total pressure of 56 atm is best. Typical temperatures encountered are from about 160 to about 260, preferably using a partial pressure of H2 of 14-35 atm and a total pressure of about 51-63 atm. The resistance of equipment required to withstand more than about 70 atm is seldom cost effective for increasing reaction rates using these pressures. The content of free ammonia should be kept above that of the amino salt but below about 3 M / l. The ammonium sulfate minimum is that derived from the reaction of the amine salt, the maximum being maintained above about 4 and preferably below 0.8-1.0 M / L.



   GOBALTHUSE REDUCTION.



   Cobalt solutions with a high ammonia and ammonium sulfate content and similar in composition to cobalt amine suspensions may also be reduced. Illustrative results of reducing these solutions to about 232 using a hydrogen partial pressure of 28 atm. and no seeding are shown in Table XVIII.



   TABLE XVIII.



   Effect of high NH3 and (NH4) 2SO4 content
 EMI28.2
 
 <tb> Content <SEP> initial <SEP> (M / 1) <SEP> Time <SEP> Yield
 <tb>
 <tb>
 
 EMI28.3
 Go NH3 (NH4) + "(Min ..)% ---------
 EMI28.4
 
 <tb> 0.88 <SEP> 10.3 <SEP> 1.6 <SEP> 60 <SEP> 65
 <tb>
 <tb> 0.87 <SEP> 9, <SEP> 4 <SEP> 1.75 <SEP> 60 <SEP> 81
 <tb>
 <tb> 0.85 <SEP> 8.2 <SEP> 1.7 <SEP> 60 <SEP> 83
 <tb>
 <tb> 0.75 <SEP> 6.4 <SEP> 5.4 <SEP> 120 <SEP> 44
 <tb>
 <tb> 0.79 <SEP> 5.2 <SEP> 5.0 <SEP> 120 <SEP> 69
 <tb>
 <tb> 0.82 <SEP> 6.65 <SEP> 3.5 <SEP> 120 <SEP> 80
 <tb>
 <tb> 0.88 <SEP> 6.75 <SEP> 1.7 <SEP> 120 <SEP> 88
 <tb>
 

  <Desc / Clms Page number 29>

 
From these and similar tests it was found that the increase in ammonium sulfate content above 0.85 M (1.7 mol NH4 +)

     affects yield as the increase of free ammonia above 7MB
Seeding with metallic cobalt powder allows faster speeds and / or lower temperatures and pressures to be used Reduction of solutions containing smaller amounts of ammonia and ammonium sulfate takes place rapidly to 204 and 56 atm of total pressure when sprouts are added. Particular results obtained under these conditions are illustrated below in Table XIX.



   TABLE XIX Seeding in the reduction of intermediate solutions
 EMI29.1
 
 <tb> Content <SEP> initial <SEP> (M / 1) <SEP> Germs <SEP> Time <SEP> Yield
 <tb>
 
 EMI29.2
 Co NH NH (9/1.) (Min.) (%) ------------- 2 ------ H ------------- -------------------------
 EMI29.3
 
 <tb> 0.12 <SEP> 0.48 <SEP> 0.48 <SEP> 665 <SEP> 30 <SEP> 100
 <tb>
 <tb> 0.12 <SEP> 0.48 <SEP> 0.48 <SEP> 200 <SEP> 20 <SEP> 100
 <tb>
 <tb> 0.6 <SEP> 2.4 <SEP> 1.44 <SEP> 665 <SEP> 30 <SEP> 99
 <tb>
 <tb> 0.69 <SEP> 2.8 <SEP> 2.8 <SEP> 200 <SEP> 20 <SEP> 86
 <tb>
 <tb> 0.95 <SEP> 3.8 <SEP> 3.8 <SEP> 665 <SEP> 30 <SEP> 89
 <tb>
 <tb> 1.2 <SEP> 9.5 <SEP> 2.4 <SEP> 100 <SEP> 20 <SEP> 82
 <tb>
 <tb> 1.2 <SEP> 9.2 <SEP> 4,

  6 <SEP> 100 <SEP> 20 <SEP> 32
 <tb>
 
It can be seen that in the first five tests, NH / Co and NH4 + / Co molecular ratios of about 4 are used with excellent results, but that the increases in the amounts of ammonia and / or ammonium sulphates decrease the amounts. returns.



   Solutions containing even lower NH3 / Co ratios can also be rapidly reduced. The particular results obtained with hydrogen in about 1 hour at 220 and 59.5 atm of total pressure are shown in Table XX below.



   TABLE XX.
 EMI29.4
 
 <tb>



  Content <SEP> initial <SEP> (M / 1) <SEP> NH3 <SEP> adds <SEP> Solution <SEP> final
 <tb>
 
 EMI29.5
 -------------------------------------------------- ----------------------
 EMI29.6
 
 <tb> Co <SEP> (NH4) <SEP> pH <SEP> (M / l) <SEP> pH <SEP> NH3 <SEP> free <SEP> (M / 1) <SEP> Reduction
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> * <SEP>%
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 0.91 <SEP> 0.25 <SEP> 3.0 <SEP> 4.4 <SEP> 9.6 <SEP> 1.5 <SEP> 99.9
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 0.85 <SEP> 0.64 <SEP> 3.7 <SEP> 3.4 <SEP> '9.05 <SEP> 0.75 <SEP> 100.0
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 0.95 <SEP> 1.19 <SEP> 3.0 <SEP> 2.4 <SEP> 10.9 <SEP> 0.5 <SEP> 99.5
 <tb>
 
 EMI29.7
 0.4 0.77 6.0 1.2 8.4 0., 1 97.5
 EMI29.8
 
 <tb> 0.43 <SEP> 1.3 <SEP> 2.1 <SEP> 1.1 <SEP> 8.3 <SEP> 0.04 <SEP> 93,

  5
 <tb>
 

  <Desc / Clms Page number 30>

 
 EMI30.1
 Co (NH,) pH (1-1 / 1) pH free NE3 (M / 1) Reduction m% -------------------------- ------------------------------------------------ 0, 14 li, 3 24 0.35 8.0 99.5
 EMI30.2
 
 <tb> 0.88 <SEP> 0.73 <SEP> 3.0 <SEP> 1.76 <SEP> 2.5 <SEP> 80.0
 <tb>
 * Note; The solutions used in these tests are obtained by acid attack and the attack liquors are treated with lime to precipitate the impurities. The pH after liming but before the addition of NH3 is indicated.



   The last test shows that when the amount of ammonia added is less than an NH3 / Co molecular ratio of about 2, the solution soon becomes too acidic and the reduction stops at a pH of about 2.5 with up to about 10 g / l of cobalt still in solution.



   The cobalt content of a neutral solution, i.e. one which does not contain free ammonia, can be reduced to some extent by applying sufficient pressure of hydrogen. However, a significant reduction can be obtained by adding ammonia gas in autoclaving during reduction. When the ammonia content is insufficient and some free acid is present, the reduction is incomplete. However, it can be made complete by maintaining a pH slightly above 7. When only small amounts of ammonia are added before reduction, for example one NH3 molecule per cobalt molecule, the reduction ceases when the solution becomes acidic. , but the product contains basic cobalt sulfate.

   The reduction under these conditions of a cobalt solution containing about 0.5 M / L of cobalt and 1.0 M / L of NH + at 2320 is indicated by the four specific results in Table XXI. In the first cycle, no NH3 is added. In the second, one molecule is added per initial molecule of cobalt, in the third and fourth cycle, NH3 is periodically added during the cycle to return to basic conditions. and the fourth solution is kept basic until the end.



    TABLE XXI.



   Acid reduction of cobalt sulfate solution.
 EMI30.3
 
 <tb>



  Solution <SEP> initial <SEP> (M / 1) <SEP> Solution <SEP> Time <SEP> Tempo <SEP> Pres- <SEP> Yield
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> final <SEP> sion <SEP> to- <SEP>%
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> tale
 <tb>
 
 EMI30.4
 Co (NH4) + pH Free H2S04 Min. (OC) ---------- ---- ----------------------% -
 EMI30.5
 
 <tb> 0.5 <SEP> 1.0 <SEP> 0.09 <SEP> 60 <SEP> 232 <SEP> 1370 <SEP> 16
 <tb>
 <tb> 0.5 <SEP> 1.0 <SEP> 0.04 <SEP> 60 <SEP> 232 <SEP> 900 <SEP> * <SEP> 55
 <tb>
 <tb> 0.5 <SEP> 1.0 <SEP> 0.012 <SEP> 90 <SEP> 232 <SEP> 1000 <SEP> 76
 <tb>
 <tb> 0.5 <SEP> 1.0 <SEP> 7.4 <SEP> 100 <SEP> 232 <SEP> 1000 <SEP> 93
 <tb>
 * Note: A yield of 55% metal is obtained.

   It also precipitates some basic sulfate.
In summary, solutions containing cobalt can be successfully reduced from mildly acidic conditions to strongly ammonia.

  <Desc / Clms Page number 31>

 niacals and containing varying proportions of ammonia, ammonium sulphate and cobalt. There are, however, definite limits which must be observed for this process to be applicable, and even narrower conditions which must be observed in order to obtain optimum results.



   Table XXII gives the analysis of a cobalt powder obtained by treating a sulfate solution from which the nickel has not previously been removed. The solution contains ammonia in a molecular ratio of 3 with Co and ammonium sulfate in a molecular ratio of 0.81 with Go. The reduction with hydrogen is carried out at 177 under a total pressure of 42 atm for 90 minutes. 80 g / l of seed powder of less than 325 mesh is used.



     TABLE XXII.



   Cobalt powder from sulphate solutions.



     Analysis% or g / 1
 EMI31.1
 
 <tb> Co <SEP> Neither <SEP> Fe <SEP> Cu <SEP> Az <SEP> S
 <tb>
 
 EMI31.2
 ------------------------------------------------- - -
 EMI31.3
 
 <tb> Solution <SEP> initial <SEP> 49.0 <SEP> 3.38 <SEP> 0.05 <SEP> 0.0 <SEP> 0.0
 <tb>
 <tb> Liquor <SEP> of <SEP> tail <SEP> 0.16 <SEP> 0.03
 <tb>
 
 EMI31.4
 Co powder 949 9 4p7% O, io% 000 ± 0.01% 0.039%
The reaction is facilitated if one operates with at least one, preferably at least two, but not more than about 7 molecules of ammonia per molecule of cobalt. Best results are obtained for NH3 / Co ratios of from about 2 to about 4. Preferably, there should be at least 0.5 or more molecules of ammonium sulfate per liter.

   Upper limits range from NH4 / + / Co ratios of around 0.8 - 1.0 for high NH3 / Co ratios greater than around 4, up to around 3 - 4 for NH3 / Co ratios of 2 - 4 In the presence of ammonium sulfate some reduction may occur in solutions containing as much as 0.9% free sulfuric acid but for complete recovery, i.e. reduction to less than 1 g / 1, ammonia solutions more basic than pH 7.0 are required.



   ADDITIONAL REDUCTIONS.



   Other metals forming complexes.



   In addition to the copper, nickel and cobalt discussed in the previous discussion, other metals such as silver, mercury, cadmium, zinc and manganese also form similar amino complexes. Among these illustrative examples, the first two are more easily reducible by hydrogen than copper; the last three are more difficult than cobalt.



     Ag and Hg are even more easily reducible than copper, so that like copper they can be reduced directly by hydrogen in the presence of a lot of free acid. This can be illustrated in the following Table XXIII showing the results obtained under the conditions indicated.

  <Desc / Clms Page number 32>

 



  TABLE XXIII,
 EMI32.1
 
 <tb> Metal <SEP> M / 1 <SEP> Anion <SEP> Temp (C) <SEP> Pressure <SEP> Time <SEP> Yield
 <tb>
 <tb>
 <tb>
 <tb> total <SEP> (Min.) <SEP> (%)
 <tb>
 <tb>
 <tb>
 <tb> (atm)
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Ag <SEP> 0.1 <SEP> S04 <SEP> 204 <SEP> 70 <SEP> 60 <SEP> 80+
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Hg <SEP> 0.5 <SEP> NO3 <SEP> 204 <SEP> 49 <SEP> 60 <SEP> 60+
 <tb>
 
These and similar results are interesting for several reasons. The yields are quite good, so that a complete reduction can be obtained in a closed circuit. Although the yields can be improved by complexion, this is not industrially necessary. It is possible to use anions such as nitrate which for basic metal salts react with the residual gas.

   Direct reduction from the acid obviates the need to handle the silver and mercury compounds which are hazardous in the dry state. Silver and mercury roughly represent the limit-metals from the point of view of the lower position (electro-negative) in the table of oxidation-reduction potentials.
Cobalt on the other hand is reducible from solutions containing only a low free acid content, even when the amine is complexed. Among the more active metals which form amino complex ions whose sulfates and / or carbonates are soluble in amino solutions with a suitable electrolyte, some can be usefully reduced by gas, others not.

   This is likely to be illustrated by the reductions in ammoniacal sulphate solutions attempted by hydrogen at about 225 for 60 minutes at a total pressure of 84 atmospheres shown in the following Table XXIV:
TABLE XXIV.



  Content of the solution.
 EMI32.2
 
 <tb>



  Metal <SEP> M / 1 <SEP> Amine <SEP> $ / la <SEP> Electrolyte <SEP> M / 1. <SEP> Reduction
 <tb> obtained
 <tb>
 <tb>
 <tb>
 
 EMI32.3
 Cd 1.0 NFi3 4, 0 (I1H,) zSO 0, 5 yes Cd l, o C2H4 (NH2) Z 4.0 H2SO4 0.9 yes Zn 1, 0 NH3 z, 0 (NH4) 2S 04 0, 5 no
 EMI32.4
 
 <tb> Zn <SEP> 0.5 <SEP> CH3NH2 <SEP> 2.0 <SEP> - <SEP> - <SEP> no
 <tb>
 <tb> Zn (l) <SEP> 1.0 (2) <SEP> C2H4 (NH2) 2 <SEP> 5.0 <SEP> H2SO4 <SEP> 1.4 <SEP> no
 <tb>
 <tb> Zn (l) <SEP> 1.0 <SEP> C5H5N <SEP> 3, <SEP> 0 <SEP> H2S04 <SEP> 1.8 <SEP> no
 <tb>
 Notes: (1) total pressure 140 atm (2) 120 minutes
Cadmium is reduced to metal while zinc is not despite more vigorous treatment.
USE ADDITIONAL DIAMINES.



   Much of the previous discussion has concerned NH3 com-

  <Desc / Clms Page number 33>

 amine me. It has been noted that other amines can be used if desired. Cobalt, nickel and copper are all reduced completely (to less than about 1 g / L in solution) from complexes with organic amines such as methyl and ethylamine, ethylene diamine, pyridine and the like. In solution of sulfates, the electrolyte can be a free acid in certain cases. In solution of sulfates and carbonates, it can be an ammonium salt or a salt of the amine used.



   In the successive selective reduction of metals from amine solutions of salts of more than one metal, some of these amines allow a more selective separation than ammonia. However, their use as shown in Table XXIV does not achieve the reduction of zinc. The usable range appears to be that of non-ferrous metals which form complexes with ammonia and whose oxidation potentials include and are between those of silver or mercury and cadmium.



   SOLUTION OTHER THAN WATER.



   In the previous examples aqueous solutions were used. However, it is not necessary to use water. For example, hydrogen is more soluble in alcohols than in water. Other acids produced by reduction are considerably less ionized in non-aqueous solutions and therefore do not affect reduction. Cadmium, which is the most difficult metal to reduce in aqueous solution, is easily reduced in an alcoholic solution of its acetate as shown in Table XXV.



   TABLE XXV.
 EMI33.1
 
 <tb>



  Solvent <SEP> Salt <SEP> Time <SEP> Temp. <SEP> Pressure <SEP> Rende- <SEP> Purity
 <tb>
 <tb>
 <tb> (Hrs) <SEP> (C) <SEP> partial- <SEP> lie
 <tb>
 <tb>
 <tb> there <SEP> H2 <SEP> (%)
 <tb>
 <tb>
 <tb> (atm)
 <tb>
 
 EMI33.2
 Methanol, 5M Cd (OH3COO) 2 1 392 35 65 99%
 EMI33.3
 
 <tb> Cd
 <tb>
 <tb> Isopro-
 <tb>
 <tb> panol <SEP> " <SEP> 1 <SEP> 392 <SEP> 35 <SEP> 80 <SEP> 99 +%
 <tb>
 <tb> Cd
 <tb>
 ANIONS OTHER THAN SULPHATE AND CARBONATE.



  * Anions other than SO4 and C03, in whole or in part, can be used in solutions in which Cu, Ni and Co are reduced, provided they allow adequate solubility, are stable in solution at temperatures reduction, that they do not react with the reducing gas or that they do not form non-reducible complexes.



   In ammoniacal solution, there are few anions which do not give adequate solubility of the illustrative metals in the form complexed with ammonia. In acidic solution, the choice is more limited, for example the phosphate causes precipitation in acidic solution. In addition, a complex forming anion is highly desirable if there is no ammonia present, eg the chloride works, but poorly to keep up with it and is not usable for nickel. However, the complex should not be too strong, for example cyanide allows a considerable reduction of copper, but cannot be used with nickel. Other anions such as nitrate not only do not appear to form complexes with these metals but can react with reductant gas in acidic solution although they are stable in basic solution.

   Other anions such as fluosilicate are suitable in acidic solution but in ammonia solution.

  <Desc / Clms Page number 34>

 niacale are decomposed at the reaction temperature (to NH4F and Si-02 gel). Examples of reduction of solutions of 2.5-1M metals at 204-2320 for 60 minutes at 63 atm by H2 are given in Table XXVI.



   TABLE XXVI.



   Content of the solution
 EMI34.1
 
 <tb> Metal <SEP> Anion <SEP> Amine <SEP> or <SEP> M / 1 <SEP> Electrolyte <SEP> M / 1 <SEP> Yield
 <tb> acidity
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> Cu <SEP> Cl <SEP> pH <SEP> 2 <SEP> NH4Cl <SEP> 0.5 <SEP> bad
 <tb>
 <tb>
 <tb> Cu <SEP> Cl <SEP> pH <SEP> 2 <SEP> NaCl <SEP> 1.0 <SEP> good
 <tb>
 
 EMI34.2
 Cu PO4 NH3 4 (NH 4) 3 PO 4 0.2 bad
 EMI34.3
 
 <tb> Gu <SEP> SiF6 <SEP> NH3 <SEP> 4 <SEP> (NH4) 2SiF6 <SEP> 0.3 <SEP> high
 <tb>
 
 EMI34.4
 Cu S04 - KCN t, 0 'good Ni Cl NE 3 4 NH4C' 0.5 high Ni CH3GOZ CH3 C02H 1 NH 4Ac 0.2 comp.



  Ni P04 Ni 4 (NH4) 3PO4 0.2 3 ± good Ni SiF 6 NH3 4 (NH4) 2SiF6, 3 3 ± comp.
 EMI34.5
 
 <tb> Neither <SEP> SiF6 <SEP> pH <SEP> 2 <SEP> (NH4) 2SiF6 <SEP> 0.3 <SEP> high
 <tb>
 * Some non-metallic precipitate
In the test with nickel acetate the final solution contains 3M free acid and in the test with nickel fluosilicate the final acidity is 1 Mo.However, these acids are weaker than sulfuric and the concentration actual hydrogen ions is not higher than that of a sulphate solution containing 1% free acid.



   In the foregoing discussion of the present invention the sources of the solutions described and illustrated are considered irrelevant as long as they consist essentially of a single reducing metal. When obtained by attacking ores or mineral concentrates and the like, these solutions are not chemically pure to the point of containing only compounds of the particular metal. It is very surprising that the results obtained by the present process on these "impure" solutions are generally very satisfactory.

** ATTENTION ** end of DESC field can contain start of CLMS **.


    

Claims (1)

CLAIMS. the - Process for the preparation of powdered metals characterized in that it consists in forming a solution containing a soluble salt of a non-ferrous metal, this metal having an oxidation-reduction potential between those of cadmium and of l 'silver in the range of electro-motive forces of the elements and being capable of forming with ammonia in solution a complex ion reducible by a gas, this solution being unsaturated with respect to the salt of the metal at the reduction temperature and having a hydrogen ion concentration at which reduction of the elemental metal takes place under reducing conditions., in treating this solution under super-atmospheric pressure and temperature with a non-sulphurous reducing gas <Desc / Clms Page number 35> furant while maintaining the concentration of hydrogen ions in the 1-l interval in which elemental metal continues to precipitate during the treatment, then to separate and collect the elemental metal from the treated solution. 2. A method according to claim 1, characterized in that the metal is cobalt, nickel, silver, cadmium or copper. 30 - Process according to claim 1 or 2, characterized in that the solution is an aqueous solution which contains in solution in addition to the salt of the metal at least a measurable quantity of a compatible electrolyte. 4.- Method according to one of the preceding claims, characterized in that the soluble salt of the non-ferrous metal is in the form of a soluble metal amine. 5. - Method according to one of the preceding claims, characterized in that the solution is a sulfuric or carbonic acid solution in which ammonia is present. 6. - Method according to claim 2, characterized in that the acid is sulfuric acid, the solution is adjusted to a dissolved metal content not exceeding about 135 g / 1 and the concentration of hydrogen ions in the solution is maintained for reduction of silver below that equivalent to an aqueous solution of about 20% free sulfuric acid, for reduction of copper and mercury below that equivalent to an acid at about 15%, for the reduction of nickel, below that equivalent to an acid to about 5%, for the reduction of cobalt below that equivalent to an acid to about 0.5% and for the reduction of cadmium below about the - 8 molecules of hydrogen ions per liter of solution. 7. - Method according to one of claims 1 to 5, characterized in that the acid is carbonic acid, the solution is adjusted to a dissolved metal content not exceeding about 200 g / 1 and the ion concentration is maintained. hydrogen so that the partial pressure of CO2 at the reduction temperature is lower than that of the reducing gas. 8.- Method according to one of the preceding claims, characterized in that the main component of the reducing gas is hydrogen and the minimum partial pressure of the reducing gas is about 3.5 atm. 90 - Process according to claim 1, characterized in that the non-ferrous metal is copper, nickel or cobalt and the solution is adjusted to contain a quantity of metal dissolved in the form of sulphated ammoniacal complex not exceeding 100 g / 1 , a total NE) molecular ratio / metal of about 8 for copper, about 4 for nickel and about 7 for cobalt and a compatible sulfate not exceeding in molecular amount 3.6 minus the molecular amount of copper initially present, 4.6 minus the molecular amount of nickel initially present and 5.6 minus the molecular amount of cobalt initially present.