LU85970A1 - ORE PROCESSING - Google Patents

Description

ί "Ore treatment".

The present invention relates to the processing of ores, such as polymetallic nodules, and more particularly to a process for recovering upgrading elements, such as nickel, copper, cobalt and manganese, from these ores.

The nodules which dot the deep ocean floor, and whose total mass has been estimated at 10 ^ tonnes for the Pacific Ocean alone, constitute a significant potential reserve, not only of manganese, but also of nickel and copper and cobalt, and to a lesser extent, tin, lead, zinc, molybdenum, vanadium. Since the nodules are by nature porous, moist and not susceptible to concentration treatments by physical means, given their very fine texture, it is the hydrometallurgical rather than pyrometallurgical processes which seem best suited to their treatment with a view to extract the aforementioned metals. The processes described in the literature are many and varied; in this regard, mention will be made of the pyrometallurgical processes: cobalt and some part of the iron; - Extraction with sulfuric acid solutions, which is not very effective for the recovery of cobalt; - treatment with alkaline solutions (NH ^ - NH ^ Cl) after reduction at high temperature; A / 2 - extraction with water after treatment with SO 2 at high temperature; - the treatment at moderate temperature with gaseous SO 2, followed by an extraction with water which releases manganese (II) sulphate, then a treatment with SO 2 + 02 and an extraction of the Cu, 5 Co sulphates , Neither trained in this second stage.

'. These processes of the prior art have the drawbacks, either of being complex, or of ensuring only an incomplete extraction of the elements of interest, in particular of cobalt. In addition, reactions are generally quite slow.

The object of the invention is to remedy the abovementioned drawbacks, and to offer a process for treating ores, and more particularly polymetallic nodules, very simple to carry out, allowing high recovery of the upgrading elements which they contain, such than nickel, copper, cobalt and manganese.

* To this end, according to the invention, the upgrading elements of these minerals are dissolved using an aqueous solution of formaldexime so as to obtain a solution relatively concentrated in upgrading elements and these 20 upgrading elements are extracted from said solution .

According to a particular embodiment of the process of the invention, the ores are ground in the form of fine particles, of an average size of the order of 5 to 200 microns, preferably of 100 microns, before the dissolution of the 25 rewarding elements.

According to another particular embodiment, the pH of the aqueous solution of formaldexime is adjusted by adding to it an aqueous solution of sodium hydroxide or ammonia.

The subject of the invention is also the upgrading elements, such as nickel, copper, cobalt, manganese, and possibly tin, lead, zinc, molybdenum and vanadium, recovered from these ores.

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3 Other details and particularities of the invention will emerge from the description below, given by way of nonlimiting example.

As just specified, the process of the present invention consists of a process for dissolving the beneficiating elements of the ores, such as polymetallic nodules, based on the use of aqueous solutions of formaldexime.

Formaldoxime, or oxime of the formaldehyde CH2 = N - OH

10 is a boiling liquid at 84 ° C., spontaneously polymerizing as a trimer ("triformoxime") solid at ordinary temperature, corresponding to the following formula: OH 1 i 1 y N - CH9 / \

15 CH2 vN —OH

N - CH2

OH

It is easily prepared in the laboratory by reaction between aqueous solutions of formaldehyde and hydroxylamine hydrochloride, according to the following reaction: H - C + OHNH0. HCl— * CH- = N - OH + H-O + HCl v 2 '2 2

H

An acidic aqueous solution of formaldoxime is thus obtained. One can also, to a concentrated solution of hydroxylamine cooled below 5 ° C, add a concentrated solution of formaldehyde: the triformoxime precipitates.

It has been known since the end of the last century (Dénigès) 30 that formaldexime solutions constitute a very sensitive reagent for metals in solution, such as copper, iron, manganese, nickel and cobalt (added since vanadium and cerium).

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Current analytical practice maintains the use of the reagent for the colorimetric determination of manganese and cerium. The metal-formaldehime complexes are most often made in the 1/6 ratio and are stable in an alkaline medium. Atmospheric oxygen generally readily oxidizes metal complexes in their lower oxidation state; thus the Fe (f.OX) g complex, yellow-orange in color, is easily transformed into the ferric Fe 3_ (f.OX) ^ complex, purple in color; similarly, the colorless Mn (II) complex, Mn- (f.OX) ^, is rapidly oxidized to a brown-red color Mn (IV) complex, Mn- (f.OX) g. The symbol f.OX in the above formulas signifies the anion CH ^ N-O ".

It has been surprisingly found, according to the invention, that the aqueous solutions of formaldexime put with astonishing ease the ores, and more particularly the nodules in solution, and this in a very wide pH range, ie from 0 at 12. Above this pH, formaldexime oxidizes rapidly in air. Depending on the conditions of pH, concentration and ratio between the quantities of solid and formaldehime involved, it is possible to ensure a more or less selective extraction of metal-containing enhancing elements, such as nickel, copper, cobalt, manganese, zinc, molybdenum and vanadium, while not dissolving iron. Preferably, an aqueous solution of formaldexime is used, a 0.1 to 4 molar solution of formaldexime.

According to the invention, the pH of the aqueous solution of formaldexime 25 is preferably adjusted by adding thereto an aqueous solution of sodium hydroxide or ammonia.

It has also been found, according to the invention, that a better extraction of the beneficiating elements * from the ores is obtained, when these are subjected to prior grinding, for example in the form of fine particles of a size average of the order of 50 to 200 microns, preferably of the order of 100 microns.

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The examples given below make it possible to illustrate certain features of the process according to the invention.

EXAMPLE 1.

Underwater polymetallic nodules 3 are used, originating from the Haiti pit (1975 sample), previously ground until they have passed through a 140 mesh (106 µm) sieve.

The material appears poorly crystallized by X-ray diffraction; (todorokite type spectrum). The dissolution residues show the diffraction lines characteristic of quartz and labradonte jq (feldspar plagioclase). Chemical analysis gave the following results (% by weight);

Mn: 28.9; Fe: 5.02; Ni: 1.29; Cu: 1.04; Co: 0.24; Zn: 0.131;

Mo: 0.065; V: 0.051.

An acid solution of formaldoxime j2 was prepared by mixing, in the stoichiometric ratio, a concentrated solution of formaldehyde (37% by weight) and hydroxylamine hydrochloride. The resulting liquid was diluted to form a stock solution, acid (pH 0), 2M in formaldehyde. For the dissolution tests, the pH was adjusted to the desired value using 2q NaOH or ammonia solutions.

The kinetics of dissolution were followed in an excess of formaldexime reagent, the conditions being as follows: setting: 1.5 g of nodule - solution: 0.51 of 0.50M formaldexime - temperature: 0 ° C - magnetic stirring. The tests were carried out at different pH values; the results obtained are given below, by way of example, at pH 7.5 (adjustment with ammonia to 7.5 at the start, 6.9 after dissolution). The dissolved fractions of the different elements were expressed as a function of the reaction time.

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t (min) Mn Fe Ni Cu Co Zn Mo V

1 22 7 17 20 28 2 22 15 3 42 17 38 37 46 4 32 30 5 53 24 51 50 59 10 39 41 10 70 33 67 66 70 18 46 54 20 82 31 77 79 80 25 51 68 10 35 90 44 82 85 85 24 54 76 60 93 47 85 91 91 29 55 82 90 95 50 86 92 92 28 55 85 180 98 54 96 92 92 49 54 92 15

Similar experiments were carried out at pH 5.5, 8.5, 9.5 and 10.5, still in an ammoniacal medium. In general, the kinetics of dissolution of iron is always slower than that of copper, cobalt, nickel and manganese.

EXAMPLE 2.

Under identical conditions of concentration and ratio of the reactants to those of Example 1, dissolution experiments were carried out at ordinary temperature. We find, ^ below, the dissolved fractions of the different elements, after three hours of reaction and at different pH.

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30 7 4 i initial M "Fe Ni Cu Co Z" V final 1.5 96 80 97 100 94 90 82 95 2.0 5 2.5 95 71 98 100 92 - - · - 3.5 3.5 95 41 91 92 89 - - - 5.9 4.5 95 44 84 95 88 - - - 6.3 5.5 97 55 97 100 92 87 74 88 6.3 10 '' 7.5 98 55 96 100 89 67 74 93 6.9 8.5 99 65 96 97 88 30 96 92 7 , 7 9.5 100 76 100 100 94 86 100 87 9.0 [5 10.5 91 76 100 100 94 70 77 69 10.4

It will be noted, for this purpose, that a maximum dissolution of manganese is obtained, as well as nickel, copper and molybdenum at pH 9.5.

EXAMPLE 3.

In this example, dissolution tests were also carried out in the presence of an excess of nodules.

The conditions were as follows: temperature: 20 ° C.

weight of solid material (polymetallic nodule): 1.00g 25 pH adjusted with ammonia duration of the dissolution test: 60 hours volume of formaldehime solution: 50 ml concentration of formaldehyde solution: 0.8 M in formalaldoxime.

The table below gives the dissolved fractions (in%) of the various elements, as well as the final pH of the solution.

fj <; i 8 initial Mn Fe Wi Cu C ° final 5 6.0 22 1 16 68 67 8.0 7.0 22 1 16 69 59 8.1 8.0 23 0.6 19 71 50 8.4 9.0 30 0.2 40 43 67 9.1 '10 10.0 66 0.2 92 77 92 10.1 _______ *

It can be seen that at all pHs, the extraction of iron is practically negligible. We can admit, to explain this phenomenon apparently in contradiction with the kinetic data I exposed above, that a real equilibrium between the solid phase and the solution ends up being achieved, and that in particular the iron complexes -formaldoxime which are certainly formed in the early stages of the reaction can react with excess manganese oxide from the solid to form the Mn-formaldoxime complex and reprecipitate an iron hydroxide or oxyhydroxide. The phenomenon is obviously economically very interesting.

It will be noted, in view of the above, that it is therefore possible to dissolve the enhancers of the polymetallic nodules with a certain selectivity, so as in particular to obtain solutions poor in iron, relatively concentrated in manganese, and containing the almost all of the cobalt, nickel and copper in the starting material.

The dissolution process can be extended to other minerals than polymetallic nodules.

EXAMPLE 4.

Manganese ore from "* 9

New Hebrides, containing ^ 6% of Mn and 1.9% of P (that is a phosphorus content much too high for the ore to be recoverable) is crushed under 200 pm. 1.5 g of the powder obtained are treated with 300 ml of formaldexime solution at pH 10 and at ordinary temperature. After one hour of stirring of the mixture, it is filtered - and the filtrate is analyzed: the latter contains 2250 mg / 1 of Mn and 1.5 mg / 1 of phosphorus. An almost selective dissolution of manganese with respect to phosphorus is therefore observed, since 9896 and 1.696 are respectively dissolved in the content of these elements. The dissolution residue 10, identified by X-ray diffraction, consists of fluoroapatite and calcite.

According to the invention, the separation of the anion complexes thus obtained with the different metals, in order to obtain pure metal fractions, will be done, for example, on ion exchange resins. With regard to the recovery of the formaldoxime reagent, it seems that we should move towards recovery of the formaldehyde by thermal decomposition of the metal complexes or by electrolytic precipitation of the metals. Solvent extraction methods of metals or selective precipitation techniques could also be used, but will come up against the very high stability of formaldehime complexes in an aqueous medium. These complexes themselves do not appear to be extractable in a non-aqueous medium, resembling that, for example, of amine complexes of copper, nickel and cobalt.

It should be understood that the present invention is in no way limited to the above embodiments and that many modifications can be made thereto without departing from the scope of this patent.

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Claims (11)

10 ¢ - "" CLAIMS. 1. Method for recovering upgrading elements, such as nickel, copper, cobalt and manganese, from ores, such as polymetallic nodules, characterized in that it comprises dissolving the upgrading elements of these ores by means of an aqueous solution of formaldexime so as to obtain a solution relatively concentrated in upgrading elements and the extraction of these upgrading elements from said solution. 2. Method according to claim 1, characterized in that before the above-mentioned dissolution of the upgrading elements, the ores are ground in the form of fine particles. 3. Method according to claim 2, characterized in that the particles have an average size of the order of 50 to 200 microns. 4. Method according to claim 1, characterized in that the particle size is of the order of 100 pm. 5. Method according to any one of claims 1 to 4, characterized in that an aqueous solution of formaldexime is used a 0.1 to 4 · molar solution of formaldexime. 6. Method according to any one of claims 1 to 5, characterized in that one adjusts the pH of the aqueous solution of formaldexime by adding thereto an aqueous solution of sodium hydroxide or ammonia. 7. Process according to any one of claims 1 to 6, characterized in that the enhancing elements are extracted from the aforementioned solution by fixing the anionic complexes formed therewith on anion exchange resins . S. Method according to any one of claims 1 to 7, characterized in that the formaldehime 30 is recovered after the extraction of the enhancing elements. 9. Process for the recovery of upgrading elements, such as nickel, copper, cobalt and manganese, from minerals, such as polymetallic nodules, as described above, in particular in the examples given. 10. Enhancing elements, such as nickel, copper, cobalt, manganese, when they are recovered by the process according to any one of claims 1 to 9. 10 Drawings *. .jf ... rianches pages including A ........ cover page 15 ...... pages of description of claims .. ....... descriptive abstract Luxembourg, îe 2 1 JUNE 1985 The agent \ t 20 Me // 25 30