FI65450C - HYDROMETALLURGICAL SCOPE - Google Patents

Description

2,65450 An important problem is the high variability in the compositions of such materials, which often forces the use of different process programs for different types of materials to recover all valuable metal components. For example, metallurgical intermediates containing non-ferrous metals such as nickel, cobalt and copper can be extracted under oxidizing conditions into basic or acidic media to dissolve valuable metals and, if possible, to leave undesired impurities in the extraction residue. Extraction with basic media, such as aqueous ammonia solutions, although the process is very useful in the treatment of relatively simple intermediates containing, for example, only nickel, cobalt, copper, iron and sulfur, has certain drawbacks. One such is that the cleaning of air used in ammonia-air pressure extraction processes requires complex air pollution control equipment, such as ammonia scrubbers to clean the used air. Similarly, when using the method for materials containing economically significant amounts of precious metals, these are soluble in ammonia-pitols extraction solvents together with nickel, copper and iron and can only be separated from the solutions by difficult and expensive methods.On the other hand, acidic extraction media which are useful in handling more complex contain precious metals, are highly corrosive at the high temperatures and pressures normally used as extraction materials for such. The extraction must therefore be carried out in very expensive pressure vessels with an acid-resistant liner.

The main object of the present invention is an economical and efficient hydro-metallurgical process which can be used for the treatment of a wide variety of metallurgical intermediates containing non-ferrous metals comprising at least one of nickel, copper and cobalt, and which may contain precious metals.

In addition, the present invention relates to a process which operates at a relatively low temperature under slightly acidic conditions and in which the process equipment can thus be made of a relatively inexpensive material.

Another object of the invention is a process for treating metallurgical intermediates containing precious metals, dissolving non-ferrous metals therefrom, whereby the precious metals remain insoluble and concentrate in the residue, so that the separation of non-ferrous metals from the precious metals can be easily performed by simple liquid-solid separation processes.

Yet another object of the invention is a method which, compared with the ammonia-air pressure extraction, requires little or no anti-pollution equipment.

These and other objects of the invention are accomplished by a process wherein a slurry of non-ferrous garage-containing metallurgical intermediates as finely divided particles is formed in a substantially ammonia-free aqueous medium dissolved in about 25 to about 300 g / L of at least one of the following sulfate salts: ammonium sulfate, sodium sulfate, sodium sulfate, ammonia-free, the pH of the aqueous slurry is adjusted to about 4.5 to about 6.3, and the slurry is reacted under positive oxygen partial pressure with a gas containing free oxygen at a temperature in the range of about 80 to about 180 ° C (the reaction is continued with nickel in the material). , to convert copper, cobalt or other non-ferrous metals forming soluble sulphates to the corresponding hydroxides, the slurry thus formed is cooled to below 100 ° C, the pressure is reduced to atmospheric pressure, sufficient sulfuric acid is added to the cooled slurry to adjust the pH to about 3. 4.3 and this acid-treated slurry is stirred at atmospheric pressure to dissolve the non-ferrous metal hydroxides, and the solution containing dissolved non-ferrous metals is separated from the acid-treated slurry.

The process provides rapid and substantially complete extraction of soluble sulfate-forming non-ferrous metals such as nickel and copper from the treated material without the strongly acidic or ammoniacal conditions used in conventional hydrometallurgical processes. This, in turn, makes it possible to carry out the process with relatively inexpensive equipment which cannot handle strongly acidic solutions, and also to ensure that the precious metals in the starting material are recovered in a concentrated residue.

Metallurgical intermediates that can be treated by the process of the present invention are artificially produced materials that contain at least one of the following metals: nickel, cobalt, and copper, but that do not contain enough sulfur to react ethiometrically with non-ferrous metals to sulfates. Non-ferrous metals can be in the form of metals and / or sulfides, e.g. nickel sulfulfide (Ni 2 S 2), copper sulfulfide (Cu 2 S), etc. The material may also contain iron and various other metallic and non-metallic impurities as well as small but economically significant amounts of precious metals such as gold, silver, palladium, platinum, iridium, ruthenium and rhodium. Typical raw materials include non-ferrous metal rock, copper rock, broken anodes, metallurgical deposits, sludges and residues, and scrap metal.

To ensure satisfactory reaction rates and substantially complete extraction of non-ferrous metals, the material fed to the process should be in the form of 4,65450 particles, of which at least 80 # pass through a standard Tyler sieve with a mesh width of 0.045 nm (325 mesh). Particles larger than this should be comminuted by some suitable method to at least this size.

If the material contains water-soluble impurities such as halogen salts, especially chlorides, such impurities should be removed before the material is subjected to the oxidation described below in an aqueous medium.

This can usually be accomplished simply by washing the impure material with a suitable impurity solvent. For example, halogen salts can be removed by washing the material with hot water containing an amount of alkali that maintains the pH at or above 9 to keep the dissolution of nickel, cobalt and / or copper from the material at an insignificant level.

After possible washing, the particles are dispersed in a solution containing the sulfate salt, which is substantially free of free ammonia. The sulphate salt preferably used in this invention is ammonium sulphate, although other suitable sulphate salts such as sodium sulphate and nickel sulphate may be used either alone or in combination with ammonium sulphate. The preferred concentration range of the sulfate salt in solution is from about 25 to about 300 g / L, more preferably from about 50 to 100 g / L. A solution containing a higher concentration of the sulfate salt can be used, but it is less advantageous because nickel tends to form insoluble salts at the lower pH used in the subsequent hydroxide solvent step. The solution containing the sulphate salt must be practically free of free ammonia, since the ammonia dissolves the precious metals contained in the raw material, so that they are lost as dissolved rather than concentrated in the residue. (Umax melt "free ammonia" as used herein means ammonia titratable with sulfuric acid).

The relative amounts of feed material and sulphate salt-containing solution are preferably adjusted so that the slurry has a density of about. 20 to about 40% by weight of solids, with the most preferred density of the slurry in each case depending on the nature of the material to be fed and the desired metal content in the solution produced. Production factors such as the size and shape of the reaction vessel and the type of mixture used also affect the density of the slurry selected in each case.

The pH of the slurry to be treated in the oxidation step must be adjusted to a range of about 4.5 to about 6.5, preferably about 5 to about 6. If the pH of the slurry is initially above the desired range, as usual after removing chloride salts by washing with alkaline solution, it is lowered by adding sulfuric acid. and when the pH of the slurry is initially below the minimum limit, it is adjusted upwards by the addition of a suitable alkali such as sodium hydroxide or ammonium hydroxide.

The slurry, the pH of which has been adjusted as above, is reacted with free oxygen in a pressure vessel equipped with a stirrer, such as an autoclave. The reaction is carried out at a temperature in the range of about 80 to about 180 ° C, preferably 120 to 150 ° C under oxidizing conditions obtained by supplying oxygen or a free oxygen-containing gas such as air, oxygen-enriched air or pure oxygen to the slurry at a pressure sufficient to provide oxygen overpressure. which is greater than about 0.03 MPa and preferably about 0.14 to 0.69 MPa. Of course, higher pressures and temperatures can be used, but the additional costs caused by such more stressful conditions on the equipment are such that the increase in reaction rate achieved does not match the cost. Once initiated, the reaction is exothermic and thus external heating is only required to initiate the reaction.

The oxidation reaction is continued until substantially all of the nickel, cobalt and / or copper in the feed material has been converted to hydroxides. Oxidation times of 4 hours or more are usually required to accomplish this.

The oxidation of nickel and copper-containing intermediates in ammonium sulfate solution is assumed to involve the following reactions: 2Ni5S2 + 4 (HH4) 2SO4 + 902 + 2H2O> 4NiSO4. (NH4) 2SO4 + 2Ni (OH) 2 (1) 2Ni04 2Ni (0H) 2 (2)

(NH 4) 2 SO 4 + 2H 2 O - (NH 4) 2 S (> 4 + Ni (OH) 2 + H 2 SO 4 (3) 2Cu 2 S + 502 + 2H 2 O -> 2CuSO 4 + 2Cu (OH) 2 4, (4)

CuSO 4 + Ni (OH) 2 _ ^ NiSO 4 + Cu (OH) 2 (5) f-

It is believed that at a pH of about 4 to 5 to about 6.3, rapid oxidation of Ni 2 S 2 and Ni 0 to diamine sulfate occurs according to Equations (1) and (2). The diamine sulfate is then rapidly hydrolyzed to Ni (OH) 2 at a temperature of about 80 to about 180 ° according to Equation (3). All the Cu2S in the particles is likely to dissolve when oxidized directly to CuSO 4 according to equation (4) and then to insoluble Cu (OH) 2 in the presence of Ni (OH) 2 according to equation (3) »

During the oxidation reaction, a viscous slurry is formed containing nickel, cobalt and / or copper hydroxide and precious metals, if present in the starting material. After completion of the reaction, the slurry is preferably cooled to a temperature below about 100 ° C and the excess oxygen is allowed to drop to normal pressure.

6 65450 An amount of sulfuric acid is added to the cooled slurry such that the pH drops to about 3-4.5 · The acidified slurry is stirred and digested at a temperature below about 100 ° C until the nickel, cobalt and / or copper are completely dissolved. The insoluble residue, which contains substantially all the precious metals present as well as any impurities, is separated from the solution by conventional liquid-solid separation methods and can be treated in the usual manner to recover the precious metals therefrom.

After suitable purification treatment steps, the extraction solution can be treated by known methods to recover nickel, cobalt and / or copper.

The following examples illustrate the implementation of the method according to the invention:

Example 1 In this example, the starting material was dried nickel anode waste slurry formed as a by-product in the electrolytic purification of nickel sulfide anodes by the method described by Boldt and Queneau in The Winning of Nickel, Longsman Canada Limited, 1967 · pp. 364-68. This material was ground to a maximum particle size of about 45 microns and then washed to remove chlorides with warm aqueous sodium hydroxide solution having a pH of 9. About 930 g of the washed material was slurried in about 6.3 liters of ammonium sulfate solution containing 37 g / L ammonium sulfate. The pH of the slurry, which was initially about 9, was adjusted by adding ^ SO 2 to about 5 * 8. After adjusting the pH, the slurry was reacted in a closed, stirred reaction vessel at 120 ° C and 0.14 MPa oxygen overpressure for 4 hours. After this reaction time, the slurry was cooled, depressurized with oxygen, and sulfuric acid was added to the slurry to adjust the pH to 3-5. The acidified slurry was stirred for 15 minutes, after which the solution was separated from the residue. The analytical values of the input material and the final solution and the recovery of non-ferrous metal extracts and precious metals are shown in Table I.

Table I

io g / ton

Ni Co Cu S Pt Pd

Feed (927 g) 597l 0.245 8.01 26 7.7 30.1

Extraction residue (32.4 g) 28.2 0.55 21.9 19.3 212 992

Extraction solution (g / l) 77 °, 37 10.0

Recovery of non-ferrous metals and precious metals io 98.3 93.0 91.0 99 99 65450 7

Example 2 This example illustrates the effect of ammonium sulphate content on nickel and copper extracts. · The starting material was obtained in the same manner as in Example 1 and with the following analysis (by weight): Hi 55.4 # Co 0.238, Cu 8.02,

Fe 0.43 »total-s 24.1» Cl 0.77 * The material was treated to remove Cl ions in the same manner as in Example 1. The washed particles were then dispersed in 613 liters of water as a slurry. The pH of the slurry was adjusted to 6 h and thereafter. The slurry was divided into 150 ml samples, each of which could be reacted at 121 ° C and 0.14 MPa oxygen partial pressure in ammonium sulfate solutions of different strengths. At the end of each reaction, sulfuric acid was added to the resulting slurry samples to adjust the pH to 3 ° 0. The resulting solution was subjected to nickel and copper analyzes and the analyzes were calculated from the treated material.

proportion of extracted nickel and copper * The results are shown in Tables II and III below. Table II

Ammonium- Kickel and copper analyzes of the solution at different reaction times (g / l) sulphate- 0.5 hours 1.0 hours 2: 0 hours 4 hours P “Ni Cu .Ni Cu Ni Cu Ni Cu • 0 '15.0 0.36 23.0 0 .94 38.0 1.36 58.0 2.3 10 22.0 0.50 33.0 1.0 52.0 1.1 71.0 4.6 50 '34.0 1.0 51.0 2.0 69.5 3.0 78.0 7.9 100 34.5 0.25 46.5 3.0 64.0 3.6 78.5 11.1 300 47.0 6.5 64.0 7.1 76.5 10.3 · 79.5 10.5

Table III

Metal extraction- $ st at different reaction times (based on liquid analysis)

Ammonium sulphate 0.5 hours 1.0 hours 2.0 hours 4 hours phate content BUU (g / l) Ni Cu Ni Cu Ni Cu Ni Cu 0 19.0 3.1 28.4 8.0 45.9 11, 3 68.3 18., 7 10 27.8 4.4 40.8 8.5 62.8 9.2 83.6 37.5 50 43.0 8.9 63.0 17.1 83.9 25 .0 91.9 64.5 100 46.2 2.2 57.5 25.6 77.3 30.0 92.5 90.4 300 59.5 56.9 79.1 60.7 92.3 85.9 93.6 85.5 8 65450

The figures in Table III show that the ammonium sulphate content has a clear effect on the extraction of nickel and copper. With an ammonium sulfate content of 0, a 4-hour extract under oxygen pressure could be extracted from only $ 68.3 nickel and $ 18.7 copper. The amount of nickel extracted with an ammonium sulfate content of 100 5/1 over a reaction time of 4 hours was $ 92.5 and the amount of copper was $ 90.4 ·

Example 3 This example illustrates the use of NagSO 4 and NiSO 4 as sulfate salts. The treated material was a metal rock residue with analysis: Ni 64.1 wt- $, Co 0.2 wt- $, Cu 4.45 wt- $, sulfur 24.8 wt- $, Pt 4 »8 g / ton, Pd 23 * 5 g / ton. Two samples of this material were otherwise treated as in Example 1 except that in one case the sulfate salt was NagSO 4 and in the other case the sulfate salt was NiSO 4. The results and other relevant information are presented in Table 17.

Table IV

entered am. (g) 2SÖ§-i

Sulfate salt NagSO ^ NiSO ^

Sulphate salt content (g / l) 107 26

The molar ratio of total S to metals in the feedstock is 0.677 0.677

Oxidation time (h) 6 6

Nickel extraction 00 92.2 90.0

Copper extraction 00 52.0 50.0

Palladium recovery 00 73 78.5

Platinum recovery 00 99 80.0

From the above results, it is found that although Na 2 SO 4 and NiSO 4 are not as effective as (NH 2) 2 SO 4 as nickel and copper extraction promoters, these salts substantially improve the extraction results compared to extraction without a sulfate salt.

Claims (5)

9 Claims: 6 5450 A process for the treatment of metal-containing intermediates containing (a) one or more of the following metals: nickel, cobalt and copper, (b) sulfuric acid below the amount required for stoichiometric sulphate formation of these metals, and (c) optionally one or more. several of the following precious metals: palladium, platinum, silver and gold, characterized in that a slurry of fine particles of this material is formed into a substantially ammonia-free aqueous solution containing about 25 to about 300 g / l of ammonium sulphate and / or sodium sulphate and / or nickel sulphate, the pH of this slurry adjusted to 4.5 to 6.5 and then the slurry is reacted with a gas containing free oxygen at a temperature in the range of about 80 to about 180 ° C under positive oxygen partial pressure, the reaction being continued until the metals of group (a) have been converted to hydroxides, the resulting reacted slurry is cooled to below about 100 ° C and the pressure is reduced to Norma aliquot, a sufficient amount of sulfuric acid is added to the cooled slurry to lower its pH to about 3 to about 4.5, this acid-treated slurry is stirred to dissolve the metal hydroxides of group (a), and the solution containing dissolved Group (a) metals is separated from the acid-treated slurry. Process according to Claim 1, characterized in that the sulphate salt content of the aqueous solution used for slurrying is from about 50 to about 100 g / l. Process according to Claim 1, characterized in that the sulphate salt is ammonium sulphate. Process according to claim 1, 2 or 3, characterized in that the slurry is reacted at an overpressure of oxygen of about 0.14 to about 0.69 MPa and at a temperature of about 120 to about 150 ° C. Process according to Claim 1, 2 or 3, characterized in that the substance to be treated contains at least one metal of group (c), and this metal is recovered in concentrated form in the insoluble residue obtained in the dissolution step of the metal hydroxides of group (a).