EP1504820B1 - In an ore flotation process usable composition of mercaptans. - Google Patents

Abstract

Composition comprising 70 - 95% of a combination of (A) n-dodecyl mercaptan (NDM) and tert-dodecyl mercaptan (TDM) in which the weight ratio NDM/TDM is 0.5-1.5, and 5 - 30% of a product (B) comprising one or aromatic or aliphatic compounds with 4-100 C and having one or two hydroxyl groups. An independent claim is also included for the process of ore recovery by flotation using the additive described.

Description

The present invention relates to the field of the extraction of metals, and more particularly the flotation of ores, especially ores based on oxides and sulfides. More particularly, it relates to a novel mercaptan-based composition that can be used, in particular, in combination with a flotation agent, and to a process for the recovery, by flotation, of valuable metal compounds.

Flotation is a well-known process for extracting a metal from low grade ores by a concentration step. This step is before further processing including heat treatment (also known as smelting) or leaching and refining. This is particularly the case for oxide ores and / or sulphides of lead, zinc, copper, silver, gold, molybdenum and metals belonging to the platinum group: platinum, palladium, rhodium, ruthenium, iridium and osmium.

The ores contain the compounds (such as oxides or sulphides) of the metals to be extracted (or valuable metal compounds), in the form of crystals which are dispersed in a gangue composed of various impurities, in particular siliceous impurities. The ores are, after extraction of the mine, crushed and then milled in a humid environment to give particles of finesse sufficient to release the crystals of the desired compounds.

During flotation, the highly heterogeneous mixture of the crystals of the desired compounds and gangue particles is introduced into water containing appropriate additives, including flotation agents, also called flotation collectors. Air is injected into the aqueous suspension thus obtained, placed in a suitable device (generally a flotation cell), so as to create bubbles which adhere to the crystals of the compounds (such as oxides and / or sulfides) containing the metal. research. The adhesion of bubbles to said crystals is promoted by the action of the agent or flotation agents used. The crystals of the metal compounds then rise to the surface and are recovered in the form of a foam, also called a flotation concentrate. The gangue particles are recovered in the lower part of the flotation cell.

The flotation concentrate has a desired metal content which is therefore considerably higher than that of the original ore. This content depends on the initial content of the ore and the selectivity of the flotation process. The amount of metal recovered in the form of flotation concentrate depends on the efficiency of the process.

Flotation agents commonly employed in the metal extraction industry include, for example, alkali xanthates of alkyl radicals having less than 6 carbon atoms, particularly potassium ethyl, amyl or isobutyl xanthate, mercaptobenzothiazoles, thiocarbamates, dithiocarbamates and dithiophosphates.

After a filtration drying step, the flotation concentrates, for example in the case of copper, are then introduced, for the heat treatment step (or smelting), in an oven at temperatures that may exceed 1500 ° C. During this step, the desired metal is melt-separated from other substances, including impurities from the ore gangue, which must be removed in the form of a slag.

It is thus understood, in particular for this reason, that it is very important from a practical point of view to obtain, at the end of the flotation step, in addition to a high yield, a concentrate having a content as high as possible in the desired metal. , so as to facilitate subsequent operations of treatment of said concentrate and final insulation of the metal. This technical interest for high-grade metal flotation concentrates is also reflected in the valuation and price of such concentrates, sold by mining companies to companies in charge of metal recovery and purification (or refining). This aspect of the metal content of the concentrate from flotation is particularly critical in the case of platinum, whose content in ores is extremely low, and usually in the range of 2 to 15 ppm.

The use of mercaptans as flotation agent is already known.

French patent application FR 2 371 967 thus discloses the use for obtaining flotation concentrates of a solution of n-dodecyl mercaptan in a polyglycol. However, this document teaches such use for obtaining flotation concentrates in increased copper content.

South African patent ZA 8405787 describes the use as a flotation collector of a solution of tert-dodecyl mercaptan in cresylic acid. This document also describes the application of such collectors for the treatment of copper ores.

However, the platinum mining industry, and more specifically the concentration of platinum ores by flotation, is, for the reasons stated above, still seeking new ways of improving the concentration of platinum ores. Platinum flotation (or selectivity), as well as flotation efficiency.

The object of the invention is to propose such a means, the description of which is given hereinafter. In what follows, the percentages which are indicated are, in the absence of indications to the contrary, percentages corresponding to contents by weight.

• de 70 à 95 % d'une combinaison (A) de n-dodécyl mercaptan (ou NDM) et de tertio-dodécyl mercaptan (ou TDM) dont le rapport pondéral NDM/TDM est compris entre 0,5 et 1,5, et
• de 5 à 30 % d'un produit (B) consistant d'un ou plusieurs composés aromatiques ou aliphatiques comprenant de 4 à 100 atomes de carbone, de préférence de 5 à 40, et possédant un ou deux groupes -OH.

The subject of the present invention is therefore primarily a composition intended for the flotation of ores, comprising:

• from 70 to 95% of a combination (A) of n-dodecyl mercaptan (or NDM) and of tert-dodecyl mercaptan (or TDM) whose weight ratio NDM / CT is between 0.5 and 1.5, and
• from 5 to 30% of a product (B) consisting of one or more aromatic or aliphatic compounds comprising from 4 to 100 carbon atoms, preferably from 5 to 40, and having one or two -OH groups.

It has indeed been found that this specific composition makes it possible to significantly improve the platinum content of the flotation concentrates which are obtained from the ores by the use of the usual collecting agents, as well as, optionally, the yield of the flotation operation.

N-dodecyl mercaptan is the thiol derivative of the straight chain alkyl radical having 12 carbon atoms of formula nC ₁₂ H ₂₅ -SH. It is a commercially available product.

By tert-dodecyl mercaptan is meant a mixture of compounds of formula:

R-SH (I)

wherein R is an alkyl radical having 9 to 15 carbon atoms and having at least one tertiary carbon, which is attached to the SH group.

The average number of carbon atoms of the alkyl radical is 12. The content in the mixture of the compound of formula (I) in which R is a dodecyl radical is greater than 50%, preferably greater than or equal to 60% by weight. .
Such a mixture is also commercially available, and may be prepared by the process described in patent application EP 0101356.

Without being bound in any way to the exact role in the composition according to the invention of the product (B), it seems that the latter plays a role of dispersing and / or foaming agent.

According to a first preferred variant, the product (B) is chosen from the group comprising phenols optionally substituted with one or more C ₁ -C ₄ alkyl radicals, cresols, naphthols, xylenols and indanols, as well as mixtures of these compounds. Such mixtures, in which the compounds are generally present in the form of their different isomers, are referred to herein as "cresylic acid".

• un oligomère d'oxyde de propylène de masse moléculaire comprise entre 50 et 2000, de préférence entre 100 et 800 ; et
• le 2-méthyl-4-pentanol, composé également dénommé Méthyl IsoButyl Carbinol ou MIBC, de formule :
  
          CH₃-CH(OH)-CH₂-CH(CH₃)-CH₃
  
  

According to another preferred variant, the product (B) is chosen from the group comprising:

• an oligomer of propylene oxide with a molecular mass of between 50 and 2000, preferably between 100 and 800; and
• 2-methyl-4-pentanol, also called Methyl IsoButyl Carbinol or MIBC, of formula:
  
  CH ₃ -CH (OH) -CH ₂ -CH (CH ₃ ) -CH ₃
  
  

The composition according to the invention advantageously comprises from 75 to 85% of the combination (A) of NDM and TDM, and from 15 to 25% of the product (B).

According to a preferred variant, taken in combination with one of the preceding, the product (B) used is cresylic acid.

According to another preferred variant, the product (B) used is MIBC or an oligomer of propylene oxide with a molecular mass of between 50 and 2000, preferably between 100 and 800.

According to yet another preferred variant, the composition according to the invention is a solution.

A composition according to the invention in which the NDM / TDM ratio is close to 1 is particularly advantageous.

The subject of the present invention is also a process for the recovery by flotation of valuable metal compounds contained in ores, comprising the introduction into a suitable cell of at least one flotation collector, characterized in that it also comprises introducing into said cell an effective amount of the composition as defined above.

It is preferred to use as a flotation collector (or agent) a compound selected from alkali xanthates of alkyl radicals having less than 6 carbon atoms, mercaptobenzothiazoles, as well as from alkali thiocarbamates, dithiocarbamates and dithiophosphates.

A particularly advantageous flotation collector is an alkali xanthate of an alkyl radical having less than 6 carbon atoms or an alkaline dithiophosphate.

It is preferred to use potassium or sodium ethyl, amyl or isobutyl xanthate as the flotation agent.

In the process according to the invention, the amount of composition based on NDM and TDM, as defined above, to be introduced into the process can be easily determined by those skilled in the art from preliminary tests, depending on various parameters such as the desired metal content of the ore. This amount generally corresponds to a weight ratio expressed on the basis of the weight of processed ore of between 2 g / ton and 150 g / ton, preferably between 5 and 50 g / tonne. The ratio of the weight of the composition according to the invention to the total weight of flotation agent can vary within very wide limits, for example between 0.5 and 200%, preferably between 15 and 125%.

The process according to the invention may be suitable for the recovery of metal compounds such as oxides and / or sulphides, comprising one or more metals selected from the group containing: lead, zinc, copper, molybdenum, nickel, cobalt, palladium, osmium, ruthenium, rhodium, iridium, and platinum. Said method may also be suitable for recovering said metals in the native state.

However, it is preferred to use it for the recovery of platinum compounds.

The introduction of the composition according to the invention and the flotation collector or collectors can be simultaneous or sequential. Generally we prefer an introduction sequential flotation collector (s), followed by that of the composition based on NDM and TDM, according to the invention.

Finally, the composition according to the invention can be introduced both at the stage of primary flotation and secondary flotation (carried out on the sterile fraction corresponding to the particles settled in the lower part of the cell, during the primary flotation).

The invention is illustrated by the following examples which are in no way limiting.

Example 1 (Reference) : Flotation of platinum ore with xanthate and dithiophosphate as flotation agents:

This flotation test is carried out on UG2 type platinum sulphide ore from a South African mine in the Rustenburg region with a platinum content of 2.5 ppm.

Step 1 : Preparation of an aqueous suspension of the ore by grinding and sieving

1150 g of this mineral are mixed with 572 g of water and introduced into a ball mill. The ore is ground for 30 minutes. The suspension is sieved through a sieve with a mesh size of 0.1 mm, and an aqueous suspension A containing 933 g of dry ore, whose particles have a mean diameter (measured by laser particle size) of 40 μm, is thus recovered.

Step 2 : Introduction of flotation additives into the aqueous suspension of the ore

To the suspension is added 4.5 ml of a 10.3 g / l copper sulphate solution as a depressant (promoting the fall of the gangue particles in the lower part of the flotation cell). .

About 2 minutes later, 79.3 mg of sodium isobutyl xanthate and 42 mg of thiophosphate are added, these two products being in the form of an aqueous solution.

About 4 minutes later, 56 mg of cresylic acid marketed by Rütgers-Huiles Goudrons and Derivatives are added.

The amount of water needed to add a total volume of 2.5 l is added.

Step 3 : Primary Flotation

After about 1 minute of resting, the mixture obtained in step 2 is floated for 5 minutes at a pH of about 8 in a Wemco type 2.5 liter laboratory cell.

73 g of concentrate are collected by skimming on the surface of the flotation cell.

This concentrate has a platinum content of 18 ppm (corresponding to the selectivity) and contains 51.2% of the Pt contained in the ore processed (the latter percentage corresponding to the yield).

Step 4 : Secondary Flotation

The sterile fraction corresponding to the settled particles is recovered in the lower part of the flotation cell, to which 13 mg of sodium isobutyl xanthate and 9.7 mg of sodium dithiophosphate are added.

After mixing for 4 minutes, 5.6 mg of cresylic acid is added, and the volume of water is adjusted to 2.5 l.

The product obtained is floated for 3 minutes under the same conditions as in step 3.

26.5 g of flotation concentrate with a platinum content of 6.6 ppm, corresponding to a yield of 6.8% in Pt, are recovered.

The total recovery rate of platinum (or total yield) is 58%.

Example 2

The following solution is prepared by simple mixing: NDM 40% CT 40% Cresyl acid 20%

The NDM and TDM used are the products marketed by Atofina.

The cresylic acid used also comes from the company Rütgers-Oils Tars and Derivatives.

Example 3

Reference Example 1 is repeated, introducing in step 2, in addition to the flotation agents, 28 mg of the solution prepared according to Example 2.

67 g of concentrate having a platinum content of 26.6 ppm, corresponding to a yield of 66.4%, are recovered after the primary flotation of step 3.

The secondary flotation of step 4 of Reference Example 1 is also repeated by adding 28 mg of the solution of Example 2. 5 g of flotation concentrate with a corresponding platinum content of 10 ppm are recovered. at 1.9% yield.

The total yield is therefore 68.3%.

Example 4 (Reference) : Flotation of platinum ore with xanthate and dithiophosphate as flotation agents:

This flotation test is carried out on UG2-type platinum sulphide ore from a South African mine in the Rustenburg region with a platinum content of 2 ppm.

Step 1 : Preparation of an aqueous suspension of the ore by grinding and sieving

1000 g of this ore are mixed with 508 g of water and introduced into a ball mill. The ore is ground for 50 minutes. The suspension is sieved through a sieve with a mesh size of 0.1 mm, 20 to 30 g of ore are taken for analysis and an aqueous suspension A is thus recovered, containing approximately 945 g of dry ore, the particles of which have a mean diameter ( measured by laser granulometry) of about 30 microns.

Step 2 : Introduction of flotation additives into the aqueous suspension of the ore

In the flotation cell stirred at 1200 rpm, 50 grams (expressed in equivalent per ton of milled ore) of copper sulphate are added to the suspension. aqueous solution, as depressant agent (favoring the fall of gangue particles in the lower part of the flotation cell).

About 2 minutes later, 85 grams (per ton of milled ore) of sodium isobutyl xanthate and 45 grams (per ton of milled ore) of sodium dithiophosphate are added, these 2 products being in the form of an aqueous solution. .

About 4 minutes later, 60 grams (per ton of milled ore) of a cresylic acid comprising about 25% of a mixture of meta and para cresol, 27% of a mixture of 2,4-xylenol and 2% are added. , 5-xylenol, and about 30% of a mixture of methyl ethyl phenol and propyl ethyl phenol. Such a cresylic acid is marketed by the Merisol Company.

The amount of water needed to add a total volume of 2.5 l is added.

Step 3 : Primary Flotation

After about 1 minute of contacting the ingredients, the mixture obtained in step 2 is floated for 5 minutes at a pH of about 8 in a Wemco type 2.5 liter laboratory cell. The volume of the solution is maintained at 2.5 liters by adding water for the duration of the flotation.

The mass of concentrate collected by skimming on the surface of the flotation cell is 124 g. The platinum content of said concentrate (corresponding to the selectivity) is 12.2 ppm and the amount of platinum recovered (expressed as a percentage of that contained in the ore treated, corresponding to the yield) is 80%.

Example 5

Example 2 is repeated using as cresylic acid that used in step 2 of Example 4.

Example 6

Reference Example 4 is repeated, introducing in step 2, in addition to the flotation agents, 30 grams (per ton of ore) of the solution prepared according to Example 5.

The concentrate mass collected is 88.7 g, for a selectivity of 14 ppm and a yield of 65.9%.

Example 7

Example 2 is repeated, replacing the cresylic acid with a propylene oxide oligomer of average molecular weight 425, sold by Bayer under the name ARCOL® PPG-425.

Example 8

Reference Example 4 is repeated, introducing in step 2, in addition to the flotation agents, 30 grams (per tonne of ore) of the solution prepared according to Example 7.

The concentrate mass collected is 115.6 g, for a selectivity of 12.6 ppm and a yield of 76.4%.

Example 9

Example 2 is repeated, replacing the cresylic acid with MIBC.

Example 10

Reference Example 4 is repeated, introducing in step 2, in addition to the flotation agents, 30 grams (per tonne of ore) of the solution prepared according to Example 9.

The concentrate mass collected is 104.8 g, for a selectivity of 12.8 ppm and a yield of 70.5%.

These examples show that the addition of the composition according to the invention to the flotation collectors conventionally used for the platinum concentration, significantly increases the platinum content of the flotation concentrate and / or the yield.

Claims (11)

1. Composition intended for the flotation of ores, comprising:

   - from 70 to 95% of a combination (A) of n-dodecyl mercaptan (or NDM) and of tert-dodecyl mercaptan (or TDM), the NDM/TDM ratio by weight of which is between 0.5 and 1.5, and

   - from 5 to 30% of a product (B) composed of one or more aromatic or aliphatic compounds comprising from 4 to 100 carbon atoms, preferably from 5 to 40, and having one or two -OH groups.
2. Composition according to Claim 1, characterized in that the product (B) is chosen from the group consisting of phenols optionally substituted by one or more C₁-C₄ alkyl radicals, cresols, naphthols, xylenols, indanols and mixtures of these compounds.
3. Composition according to Claim 1, characterized in that the product (B) is chosen from the group consisting of:

   - a propylene oxide oligomer with a molecular mass of between 50 and 2000, preferably between 100 and 800; and

   - 2-methyl-4-pentanol (or MIBC).
4. Composition according to one of Claims 1 to 3, characterized in that it comprises from 75 to 85% of the combination (A) of NDM and TDM and from 15 to 25% of the product (B).
5. Composition according to one of Claims 1 to 4, characterized in that cresylic acid is used as product (B).
6. Composition according to one of Claims 1 to 4, characterized in that use is made, as product (B), of MIBC or a propylene oxide oligomer with a molecular mass of between 50 and 2000, preferably between 100 and 800.
7. Composition according to one of Claims 1 to 6, characterized in that it is a solution.
8. Composition according to one of Claims 1 to 7, characterized in that the NDM/TDM ratio is in the region of 1.
9. Process for the recovery by flotation of metal compounds of value present in ores comprising the introduction into an appropriate cell of at least one flotation collector, characterized in that it additionally comprises the introduction into the said cell of an effective amount of the composition as defined in one of Claims 1 to 8.
10. Process according to Claim 9, characterized in that the flotation agent is an alkali metal xanthate of an alkyl radical having less than 6 carbon atoms or an alkali metal dithiophosphate.
11. Process according to either of Claims 9 and 10, characterized in that it is employed in the recovery of platinum compounds.