DE1037145B - Process for the extraction of cobalt from ores containing arsenic - Google Patents

Description

Process for the extraction of cobalt from ores containing arsenic Di (_ vGrlic-ciid 1, cseliriebelie invention relates to the extraction of carbon from ores containing arsenic. Sie 1); 'Further rifft the recovery of cobalt from its kGiiipl ", xcii, Schwcfcl-Arseii-, Nlineralien. Ini special Ixfaßt them to an improved process for the recovery of cobalt from such ores in]` Crin a metal or Oxvdes or salt in the # vc #; ciitlielieil of copper, 2 # ickel and other free state.

\ 'icl (- otherwise valuable ores are due to their high arsetigeba, itcs not degraded and processed. This is particularly true with regard to some complex gold, silver, platinum, radium, uranium, nickel and carbon ores, often in iron and arsenic-1-nin, eralen, such as arsenic pyrite, are contained or with these appear together. This problem also lies in some copper ores and in lesser ones Grade 1) for some iron and pyrite "sulphurous" ores.

In recent years there has been a noticeable and steadily increasing demand after making inanchen. Metals, before, usually from arsenic, to sulfur and usually accompanied by some iron. It is therefore a primary objective of the present Invention to develop a method that is simple, quick and complete Allows extraction of the valuable metal or metals from such ores. Another goal is to remove the ass while doing it in a form that is suitable for immediate removal without any associated Has to take risks or unaffordable costs.

It was already known to take arsenic-like ores at higher temperatures To treat pressure by means of oxygen or oxygen-containing air and thereby dic in the metals contained in ores in soluble compounds. convict. With this one The process is carried out under such conditions that it cannot be prevented that (read all arsenic, all sulfur and a large part of the iron goes into solution. According to your method according to the invention on the other hand worked under conditions in which only minimal. \ 'lcligcii of iron and arsenic are dissolved and at the same time the dissolution of a considerable Amount of cobalt is possible.

In the invention these objects are achieved in a surprisingly simple process. The process will be discussed with reference to the drawings, in which FIG. 1 is a flow scherna showing the typical main operations in the treatment of nodule-free ore; and Fig. 2 shows a flow schema used for ores containing both nickel. such as cobalt is suitable.

As can be seen from the flow sheet, a slurry of the ore in an aqueous liquid, preferably one containing some sulfuric acid, is first treated by oxidation at elevated temperature and pressure. This not only removes the acid-soluble metals contained. but also the arsenic dissolved. Dissolved iron in a quantity of up to one equivalent is quickly converted into an insoluble arsenate, probably a basic ferric arsenate or FeAso41, by g, clOste Arsell. Any further dissolved arsenic is made insoluble by the addition of iron, lime, or any other economic starting material, 1 for a cation which forms an insoluble arsenic. In this way, at pressures above about 7, atins. and temperatures of about 121 to 343 ° C. both the arsenic and a large part of the iron are converted into largely insoluble, easily disposable arsenates. At the same time, valuable metals that were originally physically or chemically associated with arsenic are released. The oxidized slurry is removed, cooled, and the solution is separated off from the residue. Usually the residue is washed. Both the acid-insoluble residue and the solution freed from the residue are processed further.

The solution can be easily removed from the residue and precipitated solids. split off. It is evident. that the arsenic conversion process is applicable to a wide variety of ores and processes because both the solution and the solids can be treated to recover any valuable material contained therein. The gold, platinum and similar metals contained in the solids, as well as the silver, can, as shown in FIG. 1 , if desired by further treatment . like leaching. Treatment with Cvanid and the like can be obtained.

The # \, irlun "-sgra, d of this process and the economy its implementation are in view of the previously unfulfilled demand for., inem such \ 'experienced particularly surprising. -Not only will (read troublesome arsenic removed. and most of it with iron, which is just as worthless, ziisaiiiiii (-, n. but the resulting chemical compounds are not only in water, but (learn completely insoluble in the caustic solution. Hence, at least part of the iron becomes and the entire .Arsenic by filtration, settling or the like. Easily animated #, animated. The insoluble arsenic compounds can be (Jen and easily thrown away, even in open waste ponds. The gold and other metals in the remaining solids 'can be more complete and economical than any hitherto known Procedure can be obtained.

Typical of the metals for which the demand is rising and the be found in ores of this type. is cobalt.

A cobalt ore of this kind normally contains cobalt, iron, nickel, arsenic, sulfur, etc., also copper, gold, silver and the like should. Accordingly, the Be-11-Aldierung of such an ore is to be taken to illustrate the invention. The removal of the arsenic as such is not the subject of the present invention. However, its application is an essential part of the process according to the invention .

In most processes loading is "chic kung material -i% Iinera, lko # nzentraten. In some cases, this is particularly suitable for obtaining you" made of cobalt content. In other i #, # this concentrate is the result of a preliminary selective concentration of other minerals contained in the original ore. In each case ## it represents a type of concentrate from which %% - (- iii, z-stens gait constituents have been removed, and the mass to be handled is N-Lrringerii, as shown in the flow sheet. # _t2rscliiedetie procedures for this purpose are known and do not form part of the present invention.

An essential lUerkmal of the invention is (1 - # i-in (the presence of let, arsenic, which has hitherto been considered ciiideutigur drawback 'in voren \ NEN V Utgend --erfahren a ausgesproche orteil 1) (-.. (Lutitet Common ores of cobalt, nickel, or copper often contain large amounts of excess in iron. It is desirable to prevent iron from being dissolved in the leaching liquor in too small amounts as described here. Arsenic practices the process important function of precipitating large amounts of iron from the solution, thereby considerably reducing the need for a later operation to remove iron, and these solids are easily removed by filtration has an effect on the entire process. However, as far as the present process is concerned, it is not necessary to reduce the grain size more than is necessary, - to separate the valuable Xlineral from dead rock and to enable the appropriate transfer as a water slurry.

The liquid for slurrying and leaching out the particles can. Be water, as sulfuric acid is formed during the oxidative exposure when (The concentrate contains sulfur. The initial presence of any acid supports, however, the medium of the reactions. Consequently, a dilute one Sulfuric acid solution is useful and commonly used. Of course you could another cheap mineral acid is added to initiate the reaction, but there is no need to do it. Sufficient amounts of a suitable sulfuric acid-containing Liquid are considered as one in other steps in the overall process, e.g. B. at Äleta The recycled solution, discussed further below, is available. The salary this recycled liquid in sulfuric acid can be low. In almost all of them Cases, more than enough sulfuric acid is formed during oxidative leaching. to carry out the necessary T # Ti-nsetuiigen.

There is one factor to be considered with regard to the amount of acid in the caustic solution sent for the oxidation treatment. A low degree of acidity favors the removal of the arsenic. For example, in the case of a cobalt extract derived from cobalt ores, it has been found that high cobalt extraction is obtained with very low arsenic extraction when the leach solution from the oxidation contains no more than about 5 to 811% sulfuric acid. Appropriately, the acid content should therefore not be much greater than for example. 1001o. On the other hand, it should be below a pH of around 4.5.

The finely divided feedstocks, usually fed as a slurry, are subjected to the primary or oxidative leach process under elevated pressures and temperatures. The total pressure on the operating vessel only needs about 7Atni with this method. to be. however, a temperature slightly higher than that corresponds to these low pressures is generally preferred. Taking into account the strength of the usual. A temperature of about 121 to 288 ° C. is expediently used for vessels, which, however, as noted above, can be about 56 ° C. higher. The pressure should be yours and usually around 28 to 45.5 Atni. be. Higher temperatures and pressures can also be used if they can be generated and handled easily enough. Usually, however, the increased cost does not correspond to the increased benefits resulting therefrom.

Oxidation in itself is achieved by using an oxidising gas, preferably oxygen, carried out in the bridge tank. Also enriched with oxygen Air or air alone can be used. When using the latter are however, the large volumes to be handled by ', \' a.cliteil.

Under oxidizing conditions, the implementation is exotic. Through this it becomes an easy-to-regulate process. The regulation is carried out in such a way that that you have steam, nitrogen and / or others Exhaust gases from the pressure vessel can flow away, in algae, which is sufficient, the pressure and thus that of him to regulate the appropriate temperature. In the case of many stylistic ores, this way enough steam for different steps of the process inside and outside the hall) of the plant. In some cases it can, for. B. at least a part the force that is required to compress air for the oxidation reaction will.

A successful procedure requires insolubilization of the whole dissolved arsenic fore concentrate. This is usually done at least in part the presence of iron achieved during the oxidation. Many concentrates contain Iron. in some cases even more than the equivalent for arsenic. Some. # Iron can also. usually in the form of full ferric salts, full of the recirculated leaching liquids be delivered, if the whole, with the caustic solution or in, form of the charge The iron introduced into the autoclave is not equivalent to the arsenic, then what is missing must be can be added. In practice, this shortfall can be reduced by adding cheap Iron minerals such as pvrite and the like, or by the addition of ground limestone can be added. The former additions beat the arsenic as an insoluble iron salt while the latter quickly remove it as the equally insoluble calcium arsenate.

However, the addition of iron and sulfur to the feed is undesirable, when both are not a winning part. That is why it is expediently cheap Alkaline-earth-containing raw material is used. The arsenates produced in the process, in particular those of calcium and magnesium are just as or even more insoluble than that of iron. Lime, limestone, dolomite and the like can be used.

As shown in the drawings, the Zufügcn llzalimetallquelle zurEinstellungeines can fully substances, such as lime and / or limestone as rda, pH be carried out in various ways. As shown above, e.g. B. favors high extraction of acid-soluble metals with low arsenic extraction in an acidity range between a pli value of about 4.5 and a sulfuric acid content of less than 10%. To support the maintenance of these conditions, limestone or the like can be added directly to the tub. As shown in the drawing, this treatment can also be carried out. when the liquid is removed from your tank or tanks, however, this requires treatment under pressure. a process which requires special equipment and is therefore undesirable. To eliminate this need, limestone or the like can be added after the slurry is cooled and pressure-relieved, but before filtration, as indicated as the main flow in the drawing.

In some cases it may also be desirable to use the insoluble To separate arsenates separately from the undissolved residue that has arisen after sufficiency, for example, if the undissolved residue is used for further metal extraction should be processed. In this case, the undissolved residue must be removed from the pil setting filtered off and the insoluble arsenates must be filtered off after the pil setting will.

The equipment and conditions for the leaching can be varied depending on the nature of the concentrate or residue. It can be carried out in stages. Appropriately, but not necessarily, it is directed in such a way that enriched liquid is continuously drained off. For example! a battery of caustic jars can be gradually drained. Each vessel can be drained and refilled in turn at successive intervals to ensure flow of treated material to the remainder of the process. In some arrangements it is also possible to load and drain each of the kettles continuously.

In either case, the effluent enriched latige is a slurry of undissolved or inert 'materials in a solution of sulfates. This ageless one Slurry is depressurised before the undissolved material is stripped off and cooled, Sufficient cooling can easily be achieved if the hot slurry is drained through a flash tank. whereby the heat released by means of a heat exchange device for other purposes can be won. Such steps are simply called "cooling" on the flow sheet. designated.

The solids of the cooled slurry then become preferred separated by filtration or by A0) and decanting or centrifuging. Usually the separated solids are washed in order to recover the entire part to secure dissolved salts. After this treatment, it is found that the filtrate or the liquid fraction contains valuable metals such as copper, cobalt and nickel. If zinc and / or silver are present, these are also largely dissolved. the Solid fraction contains the worthless iron and arsenic, partially combined, as an insoluble, easy-to-filter, easy-to-discard residue. Heavy 'metals and the precious metals like gold, platinum and not dissolved Silver, if present in the ore, is in the solid fraction in one economically viable form present.

If desired, the filtrate and wash water are used to obtain the further processed dissolved metals. In the drawings is one such method using crystallization to purify the dissolved salts of the desired Metals: and, in the illustrated company 11, for obtaining a concentrate of cobalt sulfate crystals shown. Usually this is done by evaporation and / or cooling in some usual way.

The crystallization can be carried out so far that essentially pure cobalt salt crystals are still deposited. The rest of the solution will then treated separately to the salts of any other metals and those left behind to win dissolved cobalt salts. But you can also use the crystallization up to carry out to a degree that the greatest quantity of cobalt salt crystals are precipitated and that all the remaining metal salt crystals are also deposited.

The latter method is preferable when copper is in the ore only present in small amounts. In such cases crystallize because of the larger ones Solubility of the copper salts, preferably cobalt salts. The same consideration is to apply to the nickel usually present. Cobalt and / or in solution Nickel sulfate can be crystallized directly in a copper-free state as long as prevented is that the l # Iiitterlauge is saturated with copper salts. This procedure is shown as the main flow line according to the drawing. The crystals are through any desired solids and liquids separation process, usually with simultaneous washing, collected. According to the drawing, these will become crystals treated along one line of the process, the mother liquor along another Flow line.

The mother liquor is usually returned. As noted above, it is advisable to prevent the circulation from becoming saturated with copper salts. if crystallization is the first step performed on the filtrate, therefore becomes the Copper content of the mother liquor reduced as much as possible to prevent that Copper is enriched to a concentration at which it is next Circulation with nickel and cobalt can crystallize out.

The copper deposition indicated in the flow chart can be achieved by simple Cementation can be done with scrap iron or metal recycled through the process. Copper is easily replaced in acidic solution by iron, cobalt, nickel or the like. But not nickel and cobalt. If iron is used, it will do the same The amount of iron in the solution sent to the leaching process is increased. What, as discussed above, is desirable in many cases. Undissolved iron gets together removed with spongy copper, either as shown in the drawing Filtration or by decanting or the like. The remaining solution, the cobalt and / or contains nickel salts and sulfuric acid, becomes the leaching system as the Liquid returned, which is used for the production of further, to be treated in the autoclave Slurring is used. In some cases, the content of the mother liquor can of copper or another replaceable ion must be sufficiently low that the Treatment is not needed on every cycle. In such cases, as in a alternative flow line is shown, the mother liquor can be recycled directly, without going through the steps of copper removal and filtration.

In many cases it may also be desirable to do some or that remove all copper before separating the cobalt and / or nickel salts. then is the precipitation of copper, such as cementation with scrap iron or the like., and the subsequent filtration performed prior to crystallization as in the flow sheet shown.

If desired, copper can also be removed by other methods will. For example, it is easy to precipitate out of solution as -insoluble sulfide. This can be done by adding. a soluble sulfide such as an alkali or ammonium sulfide. or by introducing hydrogen sulfide. It can also be done by appropriate Treatment of the solution with a reducing gas such as carbon monoxide or hydrogen, metallic copper are deposited.

If only relatively pure cobalt salt crystals are precipitated, these are dissolved in the usual way in a suitable container and the solution, e.g. B. by filtration, clarified. If copper is precipitated before crystallization and only cobalt sa, ize is present, these steps can be omitted. The clarified solution is treated with sufficient ammonia to convert all of the cobalt ions to Co (NH3) "+ '- ions, where x is a number from about 2 to 6. A reducing gas such as hydrogen is then bubbled through the solution for a sufficient time essentially precipitate all cobalt as metallic cobalt powder, the latter being collected, washed, dried, and used or sold.

The nickel sulfate crystals usually contain admixtures of cobalt sulfate crystals, and in order to keep these metals separate, their crystals or their solutions must be. be separated. This is best done in solution. Accordingly, the mixed crystals dissolved, and the resulting solution, as in the treatment for cobalt crystals alone, cleared.

Steps to achieve such a result are shown in the attached flow sheet. As in the case of cobalt alone, the ions of both nickel and cobalt are converted with ammonia, 1, to ions of the type Me (NH.), ++, where x is a number from about 2 to 6 , in one as p11 -Adjustment of the step. The resulting solution should be concentrated on animonium sulphate, which is either formed as such or added as such. A sulfur-free reducing gas is then passed through to precipitate the metals.

The crackdown in the event. that only cobalt crystals are dissolved, 1 is shown in Fig.. The pH of the clarified solution is raised to above 6.8 with a sufficient amount of ammonia gas or aqueous antnionia to convert the cobalt ions into the complex Co (NH.), # '- ions. where x is a number from about 2 to 6 . The solution is then reduced with a reducing gas at about 218 to 260 ° C. and a pressure above the critical pressure. The resulting suspension is cooled, relieved of pressure and filtered. Cobalt in the form of metal powder is collected as a product. The solution is sent to an ammonia recovery system.

When both cobalt and nickel are present. must be a slightly different procedure, z. B. that shown in Fig. 2 can be used. With a pf value in the range from about 4.5 to 6.7 and in a saturated solution, cobalt remains in solution; Nickel, however, is precipitated in the form of double salt crystals of nickel sulfate amniotic sulfate. These crystals are collected and dissolved in aqueous ammonia to a solution with a pH above about 6.8 . This solution of the complex "Niclel-Amnionitiniion" is treated like the cobalt solution, as discussed above, only preferably at a somewhat lower temperature of about 191 to 218 ° C. to precipitate nickel metal powder. The filtrate, which contains cobalt, is treated to precipitate cobalt metal powder After the metal products have been collected, the filtrates are sent to some ammonia recovery system.

Ammonium sulphate is formed during the pH setting. However If available, ammonium sulfate can also be returned for concentration purposes reducing the amount of ammonia used in your circulation must to neutralize excess acid for this purpose.

The preferred reducing gas is hydrogen. however, the method is not necessarily limited to this. Carbon monoxide can also be used. Gases containing sulfur are undesirable. Hence, essentially any available, relatively sulfur-free, economical. reducing gas containing hydrogen and / or carbon dioxide can be used. As noted, the reduction is carried out under pressure at elevated temperatures, expediently at about 177 to 232 ° C., preferably about 218 ° C., for nickel and 232 to 260 ° C., preferably 238 ° C., for cobalt. The total pressures used must be at least above the critical pressure and sufficient to maintain the pressure of the reducing gas, which is usually in the range of about 14 to 35 atmospheres for conventional equipment. lies. The total pressure depends to a certain extent on the partial pressure of the ammonia which must be allowed at the process temperature.

In order to be economical, the process must involve recovery and reuse of ammonia. For the sake of completeness, one such common procedure is a distillation with lime, shown in the Fließscliema. In some cases it can it may be desirable to simply mine and sell the ammonium sulfate crystals. However, since gaseous ammonia is not available everywhere, another one can also be used Procedure may be desirable.

In the lime distillation shown in the drawing, the liquid after recovery of the metal powder passed to a Kalldestillationsapparat in which it is subjected to steam distillation in the presence of lime. The ammonium sulfate is converted to equivalent amounts of calcium sulfate and ammonia gas and recycled to the cobalt and / or nickel deposition steps. Ammonia required for supplementation can be delivered directly to your if desired Vessel can be added in which metal powder is precipitated. It can but also, as shown in the drawing, your recycled ammonia stroin was added will.

The invention is to be explained in more detail below with reference to examples, for which two ore samples were used with the following analyzes: Sample I Sample 11 As .................... 27.60 / 0 19.11 / 0 S .......... . . ......... 22.80 / 0 19.70 / 0 Fe .................... 16.7 "/ o 13.7% Cu .................... 0.20 / 0 16.3% Co ........... .... 18.4% 4.80 / 0 Ni .................... 1.00 / 0.5.50 / 0 Zn .................... - 1.20 / 0 Example 1 1 part of iron pyrite was added to 10 parts of Sample 1 to give a composite solid sample containing iron and arsenic in a 1: 1 molar ratio. This mixture was slurried with 3 parts of water and the resulting slurry was placed in an autoclave and subjected to a temperature of 232 ° C. in contact with oxygen at a total pressure of 42 atmospheres for 2 hours. The partial pressure of oxygen was approximately 10.5 atmospheres. A slurry of limestone was then added to the mixture to neutralize the excess acid generated in the reactions of the above ingredients and the combined slurries were removed from the autoclave, the solids separated from the liquid, washed, dried and analyzed. The dried solids were found to contain over 99.90 / o of the arsenic and over 99.911 / o of the iron originally present in the crude concentrates. Cobalt and nickel were crystallized out of the liquid by evaporation of a larger part of the water. The crystals contained 800/0 of the cobalt and nickel with a trace of copper. The mother liquor contained practically all of the copper and 20% of the cobalt and nickel. The crystals were separated from the mother liquor and dissolved in an ammoniacal solution. The resulting ammoniacal cobalt solution was subjected to a temperature of about 218 ° C., a pressure of about 59.5 atmospheres and a reducing hydrogen atmosphere, partial pressure about 10.5 atmospheres, until the deposition of cobalt was almost complete. Over 99% of the cobalt with a purity of about 99.5 % was reduced from the ammoniacal solution. Example 2 1 part of sample 1 was mixed with 3 parts of an aqueous liquor containing 10% sulfuric acid, and the mixture was autoclaved for 2 hours at about 238 ° C., treatment with oxygen at a total pressure of about 42 atm subject. The treated slurry was then removed from the autoclave and the solids separated from the liquid, washed, dried and analyzed. These solids contained approximately 99% of the arsenic, 98% of the iron and 27% of the sulfur, all in a highly insoluble form. Analysis indicated that the liquid contained as good as 100% of the copper and nickel and over 981% of the cobalt originally present in the crude concentrates.

Approximately 50% of the cobalt and nickel crystallized out of the solution. The mixed cobalt-nickel sulfate crystals were practically free of iron, arsenic and copper which remained in the mother liquor. The crystals were treated as shown in Example 1 to recover cobalt. Example 3 1 part of sample 2 was treated in the same manner as sample 1 in example 1. The treated solids then contained over 99% of the arsenic, 98% of the iron and 20% of the sulfur in a highly insoluble form. Analysis of the filtrate indicated that the liquid contained as good as 100% of the copper, nickel, zinc and over 99% of the cobalt.

Claims (2)

PATENT ANSI1RÜCHE- 1. Process for the extraction of comminuted ores, concentrates and mixtures thereof, the. Iron and cobalt-sulfur-arsenic complex minerals contain, containing cobalt, whereby a slurry of the particles is formed in an aqueous sulfuric acid leach solution and at a temperature of about 121 to 343 ° C and pressures above the vapor pressure of the slurry an oxidation with air, enriched with oxygen Air or subjected to oxygen, the solution thus treated is relieved of pressure and cooled, the solution obtained is separated from remaining solid materials and cobalt is obtained from the cobalt sulfate solution obtained, characterized in that the oxidation treatment is carried out at an acid content which is higher than a pH -Value of 4.5, preferably with an acid content of 5 to 8 percent by weight, is initiated and the oxidation is continued until the unisetzgut essentially ceases, during which the acid content of the slurry is kept higher than a pff value of 4.5 , but below about 10% by weight, whereby the Au Dissolution of cobalt is maximal, the dissolution of iron and arsenic is kept minimal and equivalent amounts of iron and arsenic gone into solution are precipitated again and remain as acid-insoluble arsenate, that before or after the treated slurry obtained the known measures of pressure relief , Cooling and removal of solid materials - is subjected, the acid content of the solution is reduced to a pH value of not below 4.5 by adding a neutralizing agent, preferably one that can deliver alkaline earth metal ions, and that if this takes place after the known removal of the undissolved residue, the solution is filtered again and only then is cobalt obtained from the solution obtained. 2. The method according to claim 1, characterized in that with a copper content of the materials, the leaching liquor freed from arsenic is subjected to a process for removing cobalt, the removal of cobalt being carried out only so far that the ratio of the remaining dissolved cobalt to dissolved copper is such that copper is removed with the cobalt and that the remaining cobalt is returned. 3. The method according to claim 2, characterized in that the cobalt is removed by crystallizing a cobalt salt, which is only carried out so far that the cobalt salt crystallizes almost free of copper, and that the remaining cobalt-containing liquid is returned. 4. The method according to claim 2, characterized in that before the cobalt separation, the copper is first removed from the acidic solution and collected. 5. The method according to claim 2, characterized in that before the separation of the cobalt, the copper is first removed from the acidic solution by a treatment with waste metal, which is able to replace the copper in acidic solution, and is collected. 6. The method according to claim 2, characterized in that prior to removing the cobalt, copper is removed by treating the solution with a reducing gas. 7. The method according to claim 2, characterized in that prior to the removal of cobalt Küpfer is removed by treating the solution with a water-soluble sulfide which is capable of forming copper sulfide in acidic solution. 8. The method according to claim 3, characterized in that if the material has a nickel content, cobalt and nickel are crystallized out as a mixture of salts of both metals. Publications considered: German Patent No. 744 120.