FR2673617A1 - PROCESS FOR SEPARATING RHENIUM FROM ACID SOLUTIONS CONTAINING MOLYBDENE. - Google Patents

Abstract

Process for the separation of rhenium from molybdenum and / or other elements from acid solutions by fixing the Re on resin or solvent of the tertiary amine type, washing the fixing agent with an acid solution of a compound of pure Re, and elution with a basic solution.

Description

PROCESS FOR THE SEPARATION OF RHENIUM FROM ACID SOLUTIONS CONTAINING

MOLYBDENE

TECHNICAL AREA

  The invention relates to a process for the selective separation of rhenium from molybdeniferous acid solutions, generally resulting from the processing of molybdeniferous ores, for example rheniferous molybdenite, or other ores such as those coming from the mining industry.

copper and also containing Re.

STATE OF THE ART

  The treatments of these ores, generally based on sulphides, lead to acid solutions containing rhenium; they usually include: a stage of oxidizing roasting of the sulphide-based ore leading to a gas which is filtered and which contains 502, SQ 3, and volatile oxidized Re (in the form of Re 207) and a drive of oxidized molybdenum in the form Mo O 3, the other components remaining mainly in solid condensed form of oxidized compounds of Mo and / or Cu, etc; entrainment of the impurities in the gases can however take place, for example Mo O compounds of Cu, of Se a capture of this gas by an aqueous solution or water, which leads to a sulfuric acid solution enriched in perrhenic acid and containing molybdic acid This solution can contain more than 90% of Re present in the ore, but also molybdenum and other impurities in significant quantity (Mo / Re ratio can

reach 10/1).

  It is then necessary to separate Re from Mo as completely as possible to recover all of Re without entailing Mo

and other impurities.

  To carry out this separation Re / Mo in acid solution, it is known to neutralize this solution in order to pass to basic medium (generally using sodium hydroxide) o Re and Mo are soluble, while completing the oxidation using of a hypochlorite, then of carrying out an extraction on a strongly basic resin of the quaternary amine type R 4 N (for example Amberlite IRA 400); Re and Mo are then fixed on the resin and Mo is then eluted with a sodium hydroxide solution while Re is eluted with a solution of very strong acid, for example perchloric acid, to give perrhenic acid in solution This solution can then be neutralized by ammonia to give a

ammonium perrhenate.

  To improve the purity of the product obtained, one can, before neutralization with NH 3, acidify with H Cl, inject H 2 S to precipitate a heptasulfide of Re, filter, dissolve in an ammonia and peroxide solution

  of hydrogen and finally precipitate the pure ammonium perrhenate.

  Such a separation process is complex and also requires transforming the starting acid solution into a basic solution, which constitutes an expensive operation and an additional source of effluents.

DESCRIPTION OF THE INVENTION

  Given these drawbacks, the applicant has developed a process for the separation of rhenium from molybdenum and / or possibly other impurities, sometimes in large quantities, contained in an acid starting solution, characterized in that successively performs a preferential fixation of Re by passing the starting solution over a fixing agent (resin or solvent)) of the tertiary or secondary amine type to obtain a fixing agent loaded with all the Re of the starting solution and d 'a residue of Mo and possible impurities, and an effluent free of Re containing the major part of Mo and any other impurities; a reflux wash of the fixing agent loaded with Re with an acid solution containing pure Re to displace the residue of Mo and the other impurities and obtain a fixing agent comprising only pure Re and an effluent containing Mo and the other impurities eluted as well as a balance of Re, which effluent is preferably recycled in the fixing step; an elution of the fixing agent loaded with pure Re with a solution

  basic to obtain a final solution of pure perrhenate.

  During this description, the expressions Mo, Re, Cu, Se

  relate to the elements contained in a chemical combination, and do not represent the isolated metallic or metalloid element as such. The invention is especially interesting for treating acid solutions originating from molybdenum ores, for example of the rheniferous molybdenite type, containing Re, but also from other ores where Re is in

presence of other elements.

  The starting solution containing mainly Re and Mo has an acidity generally between 1 and 8 N, and can comprise a significant amount of Mo, the weight ratio Mo / Re being able to reach 5/1 but is generally close to or less than 3/1 This solution can also contain other impurities, sometimes in significant quantity, coming from the upstream of the process, for example Cu, Se It is essential to use a weakly basic fixing agent (resin or solvent), preferably of the tertiary amine type, but also secondary, more weakly basic than the agents of the quaternary ammonium type. The use of these is to be avoided and even when they are used in mixture with tertiary amines the selective fixation of Re does not work, in fact they easily fix at least Mo and are especially useful when we want to fix Mo, from of solutions previously purified in Re, with a view to its recovery, as will be seen later On the other

  On the other hand, they make it difficult to re-extract rhenium in the aqueous phase.

  The tertiary amine fixing agent is for example the resin AMBERLITE IRA 93 SP from the company RHOM and HAAS, the solvent ALAMINE 336 from the company HENKEL; as secondary amine, AMBERLITE LA 2 of the

RHOM and HAAS.

  After fixing, the agent contains all of the Re but also a little Mo and, if necessary, traces of entrained impurities. As for the effluent, it evacuates most of the Mo and the other impurities as well as acid. The fixing operation is continued as long as no observed

  leakage of Re into the effluent containing Mo, impurities and acid.

  The washing operation is carried out with an acid solution containing a pure Re compound. Such a solution is advantageously obtained by adding a strong acid, preferably H 2504, to a fraction of the pure perrhenate solution obtained after the operation. elution by a base; its acidity is generally between 4 and 10 N Washing is continued until the desired purity of Re is obtained. The balance of Mo and of the other impurities which may have been fixed with Re during the fixing are eliminated in the effluent. which is generally recycled at the start of the process at the fixing stage. It is important that the washing solution is sufficiently concentrated in pure Re so that the elimination of the

co-attached molybdenum to be total.

  The elution, that is to say the recovery of the fixed Re, is carried out using a basic solution, preferably a weak base, for example ammonia in 1 M solution, to obtain a very perrhenate. pure in solution, for example ammonium perrhenate The purity obtained is

  such that in general the Mo / Re ratio is less than 500 ppm, this limit easily being able to not exceed 100 ppm.

  The elution can be carried out hot (for example 600 ° C.) which advantageously makes it possible to obtain a concentrated solution of perrhenate; by allowing this solution to cool, the solid perrhenate can be obtained by crystallization and moreover an additional purification is thereby carried out. The fixing agent (resin or solvent) after elution of Re is reused in a new fixing-washing-elution cycle In the case where a solvent is used, this is generally in solution in a diluent (for example hydrocarbon) and the process can be carried out in continuous mode, the solvent circulating in a loop for example in three columns (fixing, washing, elution) and each of the aqueous solutions circulating at

  against the current in its respective column.

  The process according to the invention thus makes it possible to obtain a very pure rhenium salt which can easily be recovered. It is important to note that the best results are obtained with starting and / or washing solutions concentrated in Re in order to have better salting out. of Mo and

  other impurities in the effluents.

  When the starting solution comes, as described above, from a gas capture tower from the roasting of ores, for example from rheniferous molybdenite or from minerals containing Cu (such as dzehzkazgasite, of the Cu Re S type) 4), or other sources of Re, it is advantageous to carry out a preliminary treatment of partial precipitation of the capture solution (before fixing on resin or solvent) using lime to remove part of the sulfuric acid. contained in the form of Ca SO 4 (gypsum), then filtration This treatment also makes it possible to remove the fine particles of almost infiltrable solid matter entrained by the roasting gases, and the materials

  organic from mineral flotation treatments.

  We can notice that the toasting operation can be considered as an operation of concentration of Re compared to the elements of the

  starting material remaining in solid form after said roasting.

  The method according to the invention can also be used to treat any aqueous solution containing Re, Mo or other elements which may be present in high proportions in which it is desired to recover in the pure state all of the Re contained; it is enough to modify and adapt the composition of the solution (for example addition of acid) so that it

  can be treated according to the invention.

  A first variant makes it possible to improve the economy of the process. It consists in treating the acid effluent resulting from the fixing, containing Mo, the other possible impurities and a part of the acid, in order to recover Mo. fixes the Mo on a resin or a solvent of the quaternary ammonium type (for example AMBERLITE IRA 400 of the Company RHOM and HAAS) One obtains as effluent a sufficiently pure acid solution which can be used to acidify the part of the pure solution of final perrhenate used in the washing step The molybdenum attached to the quaternary ammonium is then eluted using a basic solution (for example Na OH) which makes it possible to recover it under

form of molybdate in solution.

  When the starting solutions are too diluted in Re, it may be advantageous, in a second variant, to make a preconcentration of said starting solutions; this will contribute to improving the final purity of the Re and / or may make it possible to recover Re in sites where it

is scarce.

  A mode of application of this second variant, which is particularly advantageous, consists in making a preconcentration by selective precipitation of Re using an organic reagent, in aqueous or organic solution miscible with water, generally of the alkyl phosphorium type. of general formula RP + Br such as for example tetraphenylphosphonium bromide, n-tetradecyl-triphenylphosphonium bromide, n- hexadecyl-triphenyl

  phosphonium bromide, n-hexadecyl-tri-n-butylphosphonium bromide.

  The precipitate obtained enriched in Re is recovered by any solid-liquid separation means (for example filtration, flotation, decantation), thermally decomposed, the resulting Re in gaseous form then being dissolved in an acid; this acid solution constitutes the starting solution which is then sent to the fixing step. The organic precipitate titers approximately 25% (weight) of Re content and allows a Mo / Re ratio not generally exceeding 1%. obvious that we can be satisfied with this precipitation

  selective in an acid medium if the Mo / Re ratio obtained is satisfactory.

  In this case, the precipitate can be put back into solution, after thermal decomposition, by slaughtering the Re in gaseous form using

  of a base to directly obtain a perrhenate.

  Figure 1/1 illustrates a particular mode of sequence of operations starting from a molybdenite ore containing Re; it includes the preliminary treatment of partial precipitation using lime and the first variant intended to recover Mo This sequence can be continuous or discontinuous depending on the number of columns of fixing agents used. A represents an oxidizing roasting furnace, for example of molybdenite, which produces molybdenum oxide in (1) and a gas (2) containing 502 and SO 3 from roasted sulphides, all of Re in the form of oxides volatile, part of Mo also in the form of volatile oxides, other volatile or non-volatile impurities and noncondensable gases. B represents a gas filtration installation (2) giving a filtered gas (3) which may however still contain solid products which are not

retained.

  C represents a gas slaughter tower supplied with slaughter liquid (4) generally water or a suitable aqueous solution; the incondensable gases are evacuated in (5); (6) represents the effluent acid solution mainly containing Re, Mo and possibly other impurities. D represents the partial precipitation of the sulfuric acid contained in the solution (6) using lime (7) to give a slurry

(8).

  E represents the filtration of the gypsum formed during partial precipitation; it is eliminated in (9) with other solid impurities and organic matter still present; (10) an acid starting solution is obtained, intended for the selective fixing operation, containing Re, Mo and possibly other soluble impurities (for example Se); the solution (10) is mixed with a solution (18) of the same kind from the washing operation to give the solution

resulting to be treated (11).

  F represents a column filled with the fixing agent (for example tertiary amine resin), Fl, F 2, F 3 representing this same column

  respectively during the fixing, washing and elution operations.

  To carry out a continuous process, one could use several columns F1 therefore represents the fixing, on the resin, of Re, of a residue of Mo and of possible impurities; it gives rise to an effluent (12) containing almost all of Mo and impurities and the major

part of the acid.

  F 2 represents the washing of the column of fixing agent obtained previously; the washing is carried out by the solution (17) which is a mixture of a solution (15) of pure perrhenate, obtained at the end of the process, and of a strong acid (16) which can come from a treatment operation of the effluent (12) to recover Mo, which will be seen later; it gives rise to the effluent (18) containing Re polluted by the residue of Mo and impurities re-extracted during this operation, this effluent is recycled at the head of the fixing operation; the washing solution (17) must be sufficiently concentrated in Re to allow good release of the Mo fixed on the resin; the

  resin obtained then contains pure Re.

  F 3 represents the elution of the column of fixing agent obtained previously; the elution is carried out with an alkaline solution (19) (for example ammonia in concentration 1 M) to obtain a solution of pure perrhenate (13) and the fixing agent discharged from Re and reusable in Fl for a new cycle of operations; a part (15) of the final perrhenate solution (13) is removed in order to carry out, after acidification by (16), the washing operation; the part

remaining (14) is merchantable.

  G represents a column of fixing agent (quaternary ammonium) of the molybdenum according to the first variant, Gi and G 2 representing this same

  column respectively during the fixation and elution operations.

  Gl represents the fixation of Mo contained in the effluent (12) of the fixation column (Fl) of Re; there comes out an effluent (19) exhausted in MB and containing sulfuric acid; a part (16) of this acid can be used for the acidification of the solution (15) of pure perrhenate used for the washing operation (F 2) The remaining fraction (20) of acid can be available; a fixing agent is obtained

in MB.

  G 2 represents the elution of the column of fixing agent obtained previously; it is carried out with a basic solution (21), for example Na OH, and gives rise to a solution (22) containing the Mo in the form of a molybdate solution; the discharged resin can be used

  for a new fixation-elution cycle.

  It should be noted that the fixing-elution-washing cycle according to the invention can be carried out on a varied range of acid solutions, by their nature, their concentration of acid or of elements Re or Mo etc. and that in particular the solutions 6, 8, 10, 11, 18 may be suitable. The second variant consisting of a prior concentration of rhenium by selective precipitation can also be carried out, as

  optional on solutions 6, 8, 10, 11, 18.

EXAMPLE 1

  This example illustrates the application of the invention to industrial solutions whose composition in main elements is as follows: Re 0.9 g / l Mo 2 g / l or Mo / Re = 2.2 Se 29 mg / l

H 25 04 6 N

  and suspended Mo and Se dusts. Lime milk of 100 g / i was prepared and added to the solution.

previous rate at 12.5%.

  The suspension obtained was filtered through a gypsum pre-layer, and the cake was washed; losses on the cake are minimal The solution obtained title, after washing the gypsum cake Re 0.68 g / l Mo 1.6 g / l or Mo / Re = 2.3 Se 23 mg / l

H + 4 N

  The extraction was carried out on a column of AMBERLITE IRA 93-SP resin from

  diameter 1 cm with a "bed volume" (BV) of 40 ml.

  the fixing was carried out with a flow rate of 10 BV / h; a leak of Re appears after passage of approximately 40 BV of the acid solution; the maximum rhenium load being obtained after passing 100 BV, the fixation is then stopped. The leak in Mo appeared after passing from 2 to 3 BV of the acid solution; we can see that the resin has been enriched in Re

in an important way.

  washing, consisting in removing the Mo from the resin, was carried out with the ammonium perrhenate solution NH 4 Re O 4 in the following sulfuric solution Re 4.5 g / l

H 2 SO 4 8 N.

  wash solution flow 1 BV / h.

  After passing around 12 BV we note that there is no longer any trace of Mo

  and Se and that the Re introduced has been largely fixed.

  the elution of Re was carried out with a 1 M ammonia solution. 1 l flow rate of the solution: 1 BV / h The Re is completely eluted after passage of 10 BV, in the form of a solution of ammonium perrhenate titrating Re 9.5 g / l Mo 4.6 mg / l i.e. Mo / Re = 0.048

EXAMPLE 2

  This example illustrates the application of the invention to the case where the rhenium is preconcentrated by selective precipitation using a reagent of the

alkylphosphonium type.

  The industrial solution used is the same as that obtained in

  Example 1 after washing the gypsum cake.

  To this solution, a solution of tetraphenylphosphonium-bromide was added at 600 ° C. at the rate of 4 moles of this reagent per gram atom of rhenium. After 30 minutes of stirring, the suspension was filtered. After drying, the precipitate contained 25% rhenium and 0.2% molybdenum (ie Mo / Re = 0.8%) The rhenium content of the filtrate was only 0.03 g / l, i.e. a yield of recovery of upper rhenium

95%.

  The precipitate obtained is then thermally decomposed and the volatile rhenium oxide is slaughtered using an acidic aqueous solution. A solution containing 21 g / l of rhenium and 0.2 g / l of molybdenum was obtained. As in Example 1, this solution was introduced into a column filled with an AMBERLITE IRA 935 P ion exchange resin. The fixed rhenium was then eluted with a molar ammonia solution. A pure solution of ammonium perhenate containing 45 g / l of rhenium and 0.05 g / l of molybdenum, i.e. a Mo / Re ratio close to 0.01%, whereas it was 2.2 in the solution

initial industrial.

EXAMPLE 3

  In this example, the precipitate obtained in Example 2 by precipitation using tetraphenylphosphonium bromide is thermally decomposed, and the volatile rhenium oxide is killed using a

basic solution (NH 4 OH 2 M).

  The resulting solution contains 52 g / l of rhenium and 0.25 g / l of Mo.

  After concentration by evaporation and crystallization, ammonium perrhenate crystals were obtained having a low Mo content (Mo / Re

  = 0.1%), which has therefore been improved by crystallization.

Claims (7)

  1 Process for the separation of rhenium from molybdenum and / or possibly other impurities, sometimes in large quantities, contained in an acid starting solution, characterized in that one carries out successively: a preferential fixing of Re by passing the starting solution on a fixing agent (resin or solvent) of the tertiary or secondary amine type in order to obtain a fixing agent charged with all of the Re of the starting solution and of a residue of Mo and of the possible impurities, and a effluent free of Re containing the major part of Mo and possible other impurities; a reflux wash of the fixing agent loaded with Re with an acid solution containing pure Re to displace the residue of Mo and the other impurities and obtain a fixing agent comprising only pure Re and an effluent containing Mo and the other impurities eluted as well as a balance of Re, which effluent is preferably recycled to the fixing step.   an elution of the fixing agent loaded with pure Re with a solution   basic to obtain a final solution of pure perrhenate.   2 Method according to claim 1 characterized in that the starting solution has an acidity between 1 and 8 N, and a Mo / Re ratio reaching 10/1.   3 Method according to any one of claims 1 or 2 characterized   in that the washing solution has an acidity between 4 and ON.   4 Method according to any one of claims 1 to 3 characterized in   what the washing solution is made from a fraction of the final pure perrhenate solution.   Process according to any one of Claims 1 to 4, characterized in   what elution is done with a weak base solution.   6 Method according to any one of claims 1 to 5 characterized in   that the elution is carried out hot to obtain a concentrated solution of perrhenate which is allowed to cool to allow it to crystallize solid perrhenate.   7 Method according to any one of claims 1 to 6 characterized in   that the starting solution is a solution obtained by capturing the oxidizing roasting gases of rheniferous molybdenite, this capturing solution then being treated by partial lime precipitation and filtration.   l-j O 8 -A method according to any one of claims 1 to 7 characterized in   that the fixing effluent is passed over a fixing agent of the quaternary ammonium type in order to fix the contained Mo therein, said agent then being   eluted with a basic solution to recover a molybdate in solution.   9 Method according to any one of claims 1 to 8 characterized in   that the starting acid solution is previously concentrated by selective precipitation of Re using an organic reagent of the alkyl phosphonium type, solid-liquid separation, and redissolution of the   precipitate obtained enriched in Re with an acid.