EP0107561A1 - Flotation of ores - Google Patents

Abstract

Ore flotation process which consists in introducing the flotation collector in the form of a microemulsifiable composition into the pulp of the ore to be treated. The collecting agents are generally organic compounds containing sulfur, in particular mercaptans, thioethers, polysulphides in general very poorly soluble in water. This process is particularly suitable for ores based on oxides and sulphides.

Description

The present invention relates to an improvement in the flotation of ores, in particular ores based on oxides and sulphides. It relates more specifically to the use, for flotation, of organic collectors with little or no water solubility; such collectors are found in particular among thio-organic compounds. Thus, the invention relates to a flotation process using collectors which are poorly or not water-soluble; it includes new collectors of this type, as well as a composition containing flotation collectors.

Flotation, a now classic process for the separation and concentration of different minerals, is well known, so there is no need to expose it here. It will only be recalled that this method is extremely useful for the enrichment of poor ores before the treatment of these by pyrometallurgy or hydrometallurgy; this is the case, for example, with ores of oxides and / or sulfides of lead, zinc, copper, molybdenum, etc. We know the different collectors, commonly used, such as alkaline xanthates, lower alkyl chain, in particular ethyl- or potassium amyl-xanthate, mercaptobenzo thiazols, dithiocarbamates, thiocarbamates and dithio phosphates. These compounds are sufficiently soluble in water, so that they can be added directly to the ore pulp to be treated. There are, however, compounds which could be very effective as flotation collectors, but whose solubility in water is too low for these products to lead to good results. This is for example the case of mercaptans, with more than 8 carbon atoms in the hydrocarbon chain, and xanthates with alkyls with more than 6 carbon atoms, which it would be interesting to use because of their high selectivity. Attempts have therefore been made in the prior art to dissolve such compounds so that they can better serve as a flotation collector. Thus, US Pat. No. 4,211,644, which relates to the use, as collectors, of C ₁₂ or more alkyl mercaptans, recommends the addition of a polyglycol for the purpose of wetting or / and emulsify the mercaptan which is not very soluble in water. If this solution brings some progress, it is however only partial. According to this patent, the solubilizing agent must itself be soluble in water, which limits the range of products which can be used.

The present invention provides a substantial improvement in this matter: it makes possible the use of certain collectors which are very insufficiently soluble or practically insoluble in water, to give excellent results all the same, in terms of both yield and which concerns selectivity.

The new process according to the invention consists in introducing the flotation collector in the form of a micro-emulsifiable composition into the ore pulp to be treated.

The new composition for flotation, according to the invention, is therefore characterized in that it contains the collector, a surfactant compound, a co-surfactant and optionally water, the whole being dilutable with water from the pulp to be treated, with the formation of a microemulsion.

The microemulsions according to the invention are with external water, the co-surfactant being able to not be soluble in water, unlike the adjuvants of the polyglycol type recommended in the prior art, mentioned above.

As is well known, microemulsions are systems very different from emulsions: their definition is known in the art, so it is no longer necessary to recall it here (P.A. Winsor Trans. Faraday Soc. 1948-44-376).

Collecting agents, to which the present invention applies particularly well, are generally organic compounds containing sulfur, in particular mercaptans, thioethers, polysulphides, etc. Thus, the invention makes it possible to very significantly improve the collecting effect of mercaptans with more than 8 carbon atoms and more especially in C ₁₂ to C _{18 ′,} that is to say mercaptans which are very sparingly soluble in water. An improvement is also obtained when organic sulfides of the RS-R 'type are used, in which R and R', which are similar or different, are C ₁ to C ₂₄ hydrocarbon groups; those of these compounds in which the R ′ carries a group -OH, -SH, -COOR ", -CSOR" or CSSR ", R" being H, a cation or a C ₁ to C ₁₈ hydrocarbyl group, are themselves suitable as good collectors, as shown in French patent application 2,429,617, but they give even better results when they are used in the form of a microemulsion, in accordance with the present invention. Another type of collectors giving excellent results, according to the present invention, are polysulphides RS _X -R 'where R and R' have the same meaning as above, while x takes mean values of the order of 2 to 8 and, most often, from 3 to 5; these polysulphides are new flotation agents, the interest of which comes out especially when they are put in the form of microemulsion.

Although all of the above-mentioned thiocompounds benefit, as flotation collectors, from the application of the microemulsion process according to the invention, some of the following are cited as non-limiting examples these compounds usable. Mercapto alkyl esters _HS ( _CH2 ) _nCOOR where _n is ₁ or 2 and R is C ₁ -C ₁₂ alkyl; when R is a heptyl or an octyl, in particular an ethyl-2-hexyl, these compounds, very soluble in water, are excellent collectors, especially for chalcopyrite. Their counterparts, of higher molar mass, less soluble, become interesting when they are used in microemulsion.

Dihexyl or dioctyl sulfides.

The sulfides C ₁₀ H ₂₁ SCH ₃ , C ₁₂ H ₂₅ SCH ₃ and C ₁₄ H ₂₉ SCH ₃ give excellent results with chalcopyrite, galena, blende and pyrite in the conventional method, and their counterparts with alkyls heavier instead of CH ₃ are suitable for microemulsion. It is the same for the 2-alkyl thio-acetic acids RSCH ₂ COOH which give excellent results, in the ordinary way, when R is C ₁₂ to C ₁₆ , and are well suited in microemulsion for heavier and branched R. When the acetic group of these sulfides is esterified, the conventional manner is still very well suited for methyl and ethyl esters, while for esters of higher alcohols, in particular C ₄ to C 12, it is preferable to use the collector in microemulsion . As regards the polysulfides RS _x -R or RS _x -R ', they give good results, without it being necessary to put them in microemulsion, as long as their molar mass and the sulfur content do not exceed a certain limit. So for example, di-hexyl trisulfide C ₆ H ₁₃ SSSC ₆ H ₁₃ , as well as dihexyl penta sulfide, are good collectors of chalcopyrite and galena, but the results are better when they are used in microemulsion; for polysulphides of higher molar masses, the improvement, due to the microemulsion, becomes very significant.

où R peut être un alkyle en C₁ à C₃₀, de préférence en C₆ à C₁₈ ; un aryle ou aryle substitué portant de préférence un alkyle linéaire en C₁ à C₁₈ ou mieux en C₆ à C₁₂ ; un groupe hétérocyclique ou un cyclo-alkyle ou éventuellement un atome d'hydrogène ; R désigne un alkylène, généralement linéaire, le plus souvent en C₁ à C₆ ; n est un nombre entier de 1 à 12 et, le plus souvent, de 2 à 6. Les composés industriellement les plus courants, correspondant à la formule (1), sont des polyoxy éthylènes et des alkyl phényl polyoxy éthylènes, connus dans le commerce sous la dénomination de "SIMULSOL" et de "TRITON X".The particularity of the compositions of the collectors for flotation, according to the invention, resides in that the liquid phase, associated with the collector itself, consists of a liquid surfactant or at least dissolved in a small amount of suitable solvent. Such preferred surfactants are nonionic compounds which can be selected from the many classes known per se; these are, for example, polyoxyalkylene which can carry different groups, corresponding to the general formula

where R can be C ₁ -C ₃₀ , preferably C ₆ -C ₁₈ alkyl; an aryl or substituted aryl preferably bearing a linear C ₁ -C ₁₈ or better C ₆ -C ₁₂ alkyl; a heterocyclic group or a cycloalkyl or optionally a hydrogen atom; R denotes an alkylene, generally linear, most often C ₁ to C ₆ ; n is an integer from 1 to 12 and, most often, from 2 to 6. The industrially most common compounds, corresponding to formula (1), are polyoxyethylenes and alkyl phenyl polyoxyethylenes, known in the trade under the name of "SIMULSOL" and "TRITON X".

Polyoxyethylenes can also be used in the form of their adducts with sorbitan esters, known under the name of "TWEEN". Other useful surfactant compounds are polyoxyalkylene esters or ethers of formula (1), such as laurates, stearates, oleate or ricinoleate of a polyoxyethylene, optionally carrying an alkylphenol group. Can also be used thio polyoxyalkylene ethers, that is to say bodies in which the first oxygen in formula (1) is replaced by sulfur; this is for example the case of tert-dodecyl monothio ether and dodeca-ethylene glycol. Also suitable are surfactants of the type alkyl glucoside.

The liquid surfactant compounds listed above are non-ionic compounds which appear to be most suitable. However, it is also possible to use anionic or cationic surfactants, when the desired pH for the pulp treated by flotation allows it. Thus, can the invention be achieved by the use of compositions of collectors mixed in advance, in the form of liquid, with surfactants constituted by petroleum sulfonates, fatty alcohol sulfates, which are anionic or alkylolamides, fatty amines or quaternary ammoniums, cationic.

When the surfactant is solid or viscous, it is always possible to create a liquid medium by the addition of a little water or a third solvent, for example a mono- or polyol; moreover, the co-surfactant may be sufficient to make the medium liquid.

As indicated above, in the very definition of the invention, the composition according to the invention comprises a third constituent, namely a cosurfactant. The nature and role of this agent are known in the art: it is sufficient, to carry out the invention, to choose one or more co-surfactants from those which have been described in the prior art. It will only be recalled that the agents in question are organic molecules having a lipophilic part and at least one polar group; these are, for example, alcohols, generally C ₃ or more, alkylene glycols, in particular ethylene-, propylene-, butylene- or hexylene glycols; these compounds can be linear or branched. Also suitable as co-agents are alkyl ethers and glycol esters, ketones, fatty acid esters, i.e. with more than C ₄ and on all in C ₆ to C _{18 ′} of primary, secondary and tertiary amines, preferably with more than 4 carbon atoms, urea and its derivatives, etc. For economic reasons, it is different alcohols, and more particularly C ₃ to C ₈ alcohols, which are the most used. The water-solubility of the co-surfactant is not necessary in the case of the present invention.

Since the very principle of the invention resides in the microemulsion of the compound intended to serve as a flotation collector, it goes without saying that the proportions of the constituents must be such that the microemulsion can be formed. In other words, the nature and the proportions of collector, surfactant compounds and co-surfactant, are chosen so that the mixture obtained is stable, optically isotropic, homogeneous and dilutable with water. At the time of this dilution, a microemulsion or swollen micellar solution of the collector is formed in water, which corresponds to an extremely fine dispersion of this collector; thus, even with substances insoluble in water, used as a collector, it can be dispersed very finely in the pulp at the time of use.

The compositions according to the invention can be completely anhydrous, but it is possible to add a certain amount of water to them to facilitate their handling.

Although the proportions of the 3 constituents defined above vary according to the nature of these constituents, the following approximate proportions can be indicated - by way of non-limiting example: for compositions practically free of water:

In the case of an aqueous composition, for example:

The compositions according to the invention may optionally contain other substances, such as, for example, foaming products. They are suitable for different flotation modes, in particular primary, secondary flotation, etc.

The invention is illustrated by the following nonlimiting examples.

EXAMPLE 1

A first series of flotation tests is carried out on copper sulphide ore from the South African mine at Palabora, with a copper content of 0.45 to 0.48%.

600 g of this ore are ground to a fineness such that 76% of the powder passes through a 148 micron mesh screen.

The product is subjected to flotation for 20 minutes at pH 7.5 in a 2.5-liter laboratory cell of the MINEMET M 130 type, in the presence of methyl isobutyl carbinol (MIBC) as a foaming agent, added at the right rate. 25g per tonne of ore.

The experienced collector is n.dodecyl mercaptan, the introduction of which into the pulp is carried out in 4 ways different, as shown below.

ME Introduction in the form of a composition which gives rise to the formation of a microemulsion, when it is added to the pulp of the ore.

• E1 Introduction sous la forme d'une émulsion classique de composition pondérale :
  
  Ce qui correspond au même rapport mercaptan/tensioactif que dans le mélange ME précédent.
• E2 Sous la forme d'une émulsion classique :
  
• E3 Emulsion :
  

This composition comprises by weight:

• E1 Introduction in the form of a conventional emulsion of weight composition:
  
  This corresponds to the same mercaptan / surfactant ratio as in the previous ME mixture.
• E2 In the form of a classic emulsion:
  
• E3 Emulsion:
  

The following table 1 gives the results of these flotation tests. The second vertical column of this table indicates the quantities of n.dodecyl mercaptan used: on the one hand in grams per tonne of ore, g / T, and on the other hand, in brackets, in mole per tonne.

See Table 1 on the next page.

As can be seen, the recovery of Cu is considerably increased when the ME method is applied, that is to say the introduction of the collector in a microemulsifiable form.

For an equal quantity of collector, the emulsion processes, E1 and E2, corresponding to the prior art, give much less good results than the microemulsion method.

EXAMPLE 2

The operations are the same as in Example 1, except that the n.dodecyl mercaptan is replaced by tert.dodecyl mercaptan as a collector. The latter has been used in three different forms.

E1 Emulsion ordinaire :

E2 Emulsion :

ME Micro-emulsifiable collector

E1 Ordinary emulsion:

E2 Emulsion:

Table 2, similar to the previous one, combines the results obtained.

As in the previous example, it can be seen that the same collector gives much better results when it is introduced in a form leading to the microemulsion (ME).

EXAMPLE 3

Flotation tests similar to those of the preceding examples are carried out with di.tert.dodecyl pentasulfide as collector.

The three modes of introduction are the same as in Example 2.

ME Microemulsifiable collector

E1 Ordinary emulsion:

E2 Emulsion

The advantage of operating the collector in a micro-emulsifiable form is confirmed by these results.

EXAMPLE 4

The tests of Example 3 are repeated with di-tert.dodecyl trisulfide in place of pentasulfide. For the microemulsifiable collector, the proportions of the two alcohols have been modified: iso-propanol 6.25%, 2-ethylhexa- The results are collated in Table 4.

As with pentasulfide, we therefore find much better results when trisulfide is introduced in the form of a composition which gives a microemulsion in the pulp.

EXAMPLE 5

In a flotation test, similar to those of Example 3, the ME operation is repeated, replacing the di-tert.dodecyl pentasulfide with dedi-tert.nonyl pentasulfide, all the other conditions being the same as above.

With a collector quantity of 71.6 g / T, or 0.173 mole per tonne of ore, a copper content of 15.8% in the concentrate is obtained, and a copper recovery of 65.2%. It is therefore seen that the change of the alkyls in the pentasulfide modifies the% recovery little and does not change the copper content in the concentrate, this content being higher than in the operations using a simple emulsion (tests E1 and E2).

EXAMPLE 6

The flotation test of Example 4ME at 0.173 mole of collector per ton is repeated with di-tert.nonyl trisulfide instead of di-tert.dodecyl.

The result obtained is even better than in Table 4 above, since there is a Cu content of 16.4% in the concentrate and a percentage of Cu recovered of 59.9.

EXAMPLE 7

Under the same conditions as in Examples 3 to 6, on the same ore, flotation tests are carried out with, as collector, potassium amyl xanthate very usual in this technique. This agent is introduced into the pulp in the usual way, that is to say in the form of its aqueous solution.

The following results are found.

As a result, if the xanthate allows a greater recovery of Cu, it on the other hand provides concentrates with a copper content much lower than that which one arrives with microemulsified polysulphides. By comparing the 10.3 to 10.4% copper content in the concentrate, obtained with xanthate, with the 14.6 to 16.4% that give the tests ME of examples 3 to 6, it can be seen that the process according to the invention is capable of increasing the concentration of desired metal in the flotation product by about 50%, which constitutes a considerable improvement.

EXAMPLE 8

The flotation tests were carried out in a manner similar to that of the previous tests, but on a lead-zinc sulphide ore coming from the Pyrenean mine of NERBIOU. This ore contains 4.8% lead and 12.1% zinc.

500 g are crushed until 90% pass through a 100 micron mesh screen. The powder is subjected to flotation at pH 10 for 15 minutes.

The cell used was the same as in the previous tests. The sample was added beforehand with 30 g of foaming agent per ton.

The collector used is n.dodecyl mercaptan. It is taken, in a first test, in the form of a microemulsion ME1, identical to that of Example 1.

In a second test, the formula for the ME2 micromulsion was:

In addition, a test was carried out with the collector taken in the form of an ordinary emulsion E constituted by:

The results of this flotation are given in Table 5.

It follows that for zinc and lead, also the microemulsion method leads to a considerable improvement in the recovery yield by flotation.

Claims (11)

1. Ore flotation process, characterized in that the flotation collector is used in the form of a composition which, added to the ore pulp to be treated, gives a microemulsion. 2. Method according to claim 1, characterized in that the collector is an organic thiocompound and that it is mixed with a surfactant compound, added with a co-surfactant. 3. Application of the process according to claim 1 or 2 to the enrichment of ores with sulphides or / and metal oxides, in particular of Cu, Pb, Zn and Mo. 4. Composition of the mineral flotation collector, characterized in that it consists of a mixture of a compound serving as a collector, with a surfactant compound, and a co-surfactant. 5. Composition according to claim 4, characterized in that the collecting compound is a mercaptan with more than 8 carbon atoms, or a sulfide of the RS -R 'type where R and R', similar or different, are hydrocarbon groups, more particularly in C ₁ to C ₂₄ , x being 2 to 8. 6. Composition according to claim 4, characterized in that the collecting compound is a mercaptan of the HS (CH ₂ ) _n COOR type where n is 1 or 2 and R a hydrocarbon group with more than 8 carbon atoms. 7. Composition according to one of claims 4 to 6, characterized in that the surfactant is a polyoxyalkylene of the form R (OR1) _n OH, R being a C ₁ to C ₃₀ alkyl, an aryl, an aryl carrying a linear C ₁ to C ₁₈ alkyl, a heterocyclic or cycloalkyl group, R a C ₁ to C alkylene ₆ and n an integer from 1 to 12, it being possible for this polyoxyalkylene to be esterified or etherified. 8. Composition according to one of claims 4 to 6, characterized in that the surfactant is a petroleum sulfonate, a fatty alcohol sulfate, an alkylolamide or a quaternary ammonium. 9. Composition according to one of claims 4 to 8, characterized in that the co-surfactant consists of one or more alcohols, polyalcohols, amines and / and ureas, and in particular alcohols with at least 3 carbon atoms. 10. Composition according to one of Claims 4 to 9, characterized in that it comprises by weight 30 to 60% of collecting compound, 20 to 55% of surfactant and 5 to 20% of co-surfactant, this composition possibly containing l or organic thinner. 11. Composition according to claim 10, characterized in that the co-surfactant is insoluble in water.