Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B1/00—Preliminary treatment of ores or scrap
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B23/00—Obtaining nickel or cobalt
  • C22B23/005—Preliminary treatment of ores, e.g. by roasting or by the Krupp-Renn process
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B34/00—Obtaining refractory metals
  • C22B34/20—Obtaining niobium, tantalum or vanadium
  • C22B34/22—Obtaining vanadium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B60/00—Obtaining metals of atomic number 87 or higher, i.e. radioactive metals
  • C22B60/02—Obtaining thorium, uranium, or other actinides
  • C22B60/0204—Obtaining thorium, uranium, or other actinides obtaining uranium
  • C22B60/0208—Obtaining thorium, uranium, or other actinides obtaining uranium preliminary treatment of ores or scrap

Definitions

• the invention relates to a process for pretreatment at atmospheric pressure or close to atmospheric pressure, by alkaline wetting and heat treatment of ground ores whose gangue contains clay compounds capable of forming a stable plastic suspension in the presence of water and containing at ' minus one metallic element recoverable by hydrometallurgy.
• pretreatment the applicant intends to define a treatment prior to a hydrometallurgical recovery action allowing the extraction of the recoverable element (s) from the ore, the pretreatment having the aim of subsequently imparting to the solid phase, in the presence of a liquid phase, an ability to separate the two phases present.
• the applicant also intends to define all the metallic elements present in at least one of the minerals constituting the clay ore, capable of being extracted therefrom with a view to their valorization by hydrometallurgy.
• the clay compounds capable of forming a plastic suspension in contact with water, and frequently present in the abovementioned ores with clayey matrix can belong to the groups formed by kaolinites, such as for example kaolinite, dickite, halloysity, disordered kaolinites, serpentines; the group of micas, such as for example muscovite, biotite and paragonite, pyrophyllite and talc, illites and glauconite; the group of montmorillonites, such as, for example, beidellite, stevensite, saponite, and hectorite; the vermiculites group; the group of interstratified clays whose unitary structure is a combination of the preceding groups; the group of fibrous clays, such as for example attapulgite (palygorskite), sepiolite.
• kaolinites such as for example kaolinite, dickite, halloysity, disordered kaolinites,
• clay-matrix minerals may also contain other compounds such as, for example, quartz, calcite (CaC0 3 ), dolomite, gypsum, limonite (Fe0 (HO) nH 2 0) and other oxides and hydroxides. metallic.
• the alkaline treatment is oxidizing, it is generally carried out in the presence of free oxygen blown into the hot reaction medium in order to allow the oxidation of uranium, and its solubilization, but also to ensure the oxidation of sulfides d 'impurities, and organic matter present in the ore.
• a uranium-bearing ore preferably with a high carbonate content
• a liquor containing 40 to 50 g / 1 of Na 2 C0 3 and 10 to 20 g / 1 of NaHC0 3 in the presence of oxygen or of air blown into the reaction medium.
• the conditions of the treatment which is carried out in an autoclave, are in a range of temperatures between 95 ° C and 120 ° C, total prevailing pressure in the enclosure between 2 and 6.5 bars, with durations d 'attack which can vary between 4 and 20 hours.
• the same uranium-bearing ore with a high carbonate content is treated with the same liquor, containing 40 to 50 g / 1 of Na 2 C0 3 and 10 to 20 g / 1 of NaHCO 3 , in the presence of oxygen or of air blown into the reaction medium.
• the conditions of the treatment which is carried out in a "Pachuca" are different: the temperature is between 75 ° C to -80 ° C, while the injection pressure of air or oxygen in the reaction medium is in the range of 2 to 3 bars, for an attack time of 96 hours.
• the uranium ore containing hexavalent uranium is treated for approximately 6 hours, in the presence of oxygen, with a liquor containing from 4.2 g / 1 to 70 g / 1 sodium bicarbonate and 40 g / 1 to 100 g / 1 sodium carbonate, this treatment being carried out in the presence of an oxidation catalyst at a temperature of about 80 ° C to 90 ° C.
• the ore is subjected to an alkaline treatment at a higher temperature by means of a much more concentrated solution of bicarbonate and sodium carbonate, possibly in an oxidizing medium.
• the clay ore is first subjected to a calcination between about 315 ° C and 425 ° C, then to the actual acid treatment, in order to obtain a suspension the phases of which can be separable. But such calcination prior to treatment can make the element recoverable, refractory to the solubilizing action of acids.
• the clay mineral is first treated with the acid agent at pH 1.5 in a suspension that is not very concentrated in dry matter (65 g / l), then the suspension containing the solubilized metal to be recovered is put in contact with ion exchange resins, which fix the metal to be recovered, finally the metalliferous resins are separated by elutriation thanks to a difference in particle size.
• Such clay gangue ores can thus be condemned not to be exploited, even though they are rich in elements to be valued, or else are exploited by means of specific complex and costly treatments.
• the method according to the invention pursues the aim of restoring to those skilled in the art minerals with a clay matrix containing at least one metallic element to be recovered, pondered to be difficult to exploit by conventional acid or alkaline treatments, due to the physical consequences previously mentioned, this process consisting in subjecting said ores to a simple and inexpensive alkaline pretreatment preceding the hydrometallurgical upgrading treatments, by means of which the suspension, resulting from said upgrading treatments, becomes suitable for easy separation of the liquid and solid phases by filtration and / or decantation.
• the ore at the time of contacting with the alkaline pretreatment agent must have a particle size corresponding at most to the mesh of release of the or recoverable metallic elements.
• the ore When the ore does not naturally have such a particle size, it is subjected to a grinding operation, preferably carried out in the absence of any addition of aqueous phase.
• the ore has such a quantity of water before grinding, that the solid particles after grinding have tend to create agglomerates or granules that prevent the proper flow of these particles f.
• the ore is subjected to drying prior to grinding or is simultaneously ground and dried in such a way that the solid particles resulting therefrom have a flow capacity equivalent to that of dry silica sand.
• the alkaline pretreatment agent according to the invention can be introduced in a solid form or in the form of an aqueous solution.
• the alkaline agent When the alkaline agent is introduced in the aqueous form, it may come from a preparation by dissolving the hydroxide in natural or possibly brackish water or else by dissolving in a recycling liquor, for example from a treatment hydrometallurgical, located downstream of the pretreatment according to the invention, said liquor possibly containing chemical compounds as diverse as for example NaCl , Na 2 SO 4 , Na 2 C0 3 , NaV0 3 , NaCN.
• This agent is such that when it comes into contact with water, it releases OH ions.
• This alkaline agent can be chosen from the group formed by alkali or assimilated, and / or alkaline-earth hydroxides, and preferably from sodium and potassium and ammonium hydroxides, as well as calcium hydroxide.
• the alkaline agent can consist of a single hydroxide, such as sodium hydroxide or by the mixture of at least two hydroxides, such as, for example, sodium and calcium hydroxides.
• the quantity of the alkaline agent brought into intimate contact with the ore to carry out the alkaline wetting is at least 4 kg expressed as OH per tonne of clay contained in the ore.
• the quantity of the alkaline agent expressed as OH can be chosen in the range of 4 to 100 kg per tonne of clay contained in the ore, and preferential It can also be chosen in the range of 10 to 90 kg per tonne of clay contained in the ore.
• the ore As soon as the ore has the granulometry corresponding at most to the mesh of liberation of the recoverable metallic element or elements, it is brought into intimate contact with the alkaline agent, thus forming the pretreatment medium which has the appearance of 'A phase moistened by said agent whose physical state can vary from solid to pasty depending on whether the alkaline agent is introduced in the solid form or in the form of an aqueous solution.
• the intimate contact of the ore with a clay matrix with the alkaline agent can also be carried out by introduction of said agent before or during the grinding operation.
• the alkaline agent When the alkaline agent is in the solid form, it can be introduced with the ore into the grinding zone, the wetting taking place at least partially in said zone.
• the alkaline agent When the alkaline agent is in the liquid form, it can also be introduced dropwise or by fine spraying into the grinding zone, by partial moistening of the ore both before its introduction into said zone, and during grinding himself.
• said introduction of the alkaline agent into the grinding zone can be carried out as soon as the alkaline solution is sufficiently concentrated and desirably not too far from saturation.
• the alkaline agent Simultaneously with the introduction of the alkaline agent, it may prove useful to subject the mixture to kneading favoring the good distribution of the alkaline agent within the ore.
• the ratio of the liquid phase expressed in cubic meters to the solid phase expressed in tonnes of ore (L / S) is always at most equal to 1, is generally between 0, 05 and 0.99.
• the L / S ratio of the liquid phase present, expressed in cubic meters, to the solid phase, expressed in tonnes of ore, is all the higher as the clay content of the ore subjected to the pretreatment is itself high, so as to obtain a moist, neither fluid nor sticky dough.
• the moistened medium is then subjected to a pre-treatment temperature chosen in the interval from 15 ° C to 450 ° C.
• the duration of the pretreatment is generally short and is not a parameter to be controlled by the process according to the invention, it being understood that the pretreatment time is as much shorter as the temperature is chosen in the high values of the corresponding interval .
• the quantity of the alkaline agent brought into intimate contact with the ore to carry out the alkaline wetting is at least 4 kg expressed as OH per tonne of clay contained in the ore. More generally, the quantity of the alkaline agent expressed as OH can be chosen in the range from 4 to 45 kg per tonne of clay contained in the ore, and preferably can be chosen in the range from 10 to 40 kg per tonne of clay contained in the ore.
• the ratio of the liquid phase expressed in cubic meters to the solid phase expressed in tonnes of ore is generally between 0.2 and 0.99 and is preferably between 0.2 and 0.8.
• the moistened medium is subjected to the elimination of the releasable water present in said medium by at least one known means, such as for example evaporation, until upon obtaining a phase report liquid present expressed in cubic meters at the solid phase expressed in tonnes of ore (L / S) at most equal to 0.2 and preferably at most equal to 0.15.
• the moistened medium thus depleted in water is then brought to the pretreatment temperature of at least 105 ° C.
• This temperature at which the pretreatment is carried out is therefore defined as the minimum pretreatment temperature.
• This temperature can be chosen, in general, in the range from 105 ° C to 450 ° C, and can preferably be chosen in the range from 110 ° C to 200 ° C, depending on the nature of the clay matrix of the ore.
• the duration of the pretreatment is generally short, it being understood that the pretreatment time is shorter the higher the temperature is chosen in the corresponding range.
• the quantity of the alkaline agent brought into intimate contact with the ore to carry out the alkaline wetting is at least 4 kg expressed as OH per tonne of clay contained in the ore. More generally, the quantity of the alkaline agent expressed as, OH can be chosen in the range from 4 to 100 kg per tonne of clay contained in the ore, and preferably can be chosen in the range from 10 to 90 kg. per ton of clay contained in the ore.
• the ratio of the liquid phase expressed in cubic meters to the solid phase expressed in tonnes of ore is always at most equal to 0.6, is generally between 0.05 and 0.5 and is preferably between 0.10 and 0; 40.
• the L / S ratio of the liquid phase present, expressed in cubic meters, to the solid phase, expressed in tonnes of ore, is all the more high as the clay content of the ore subjected to the pretreatment is itself higher, so as to obtain a moist paste, neither fluid nor sticky.
• the moistened medium is then subjected to the pretreatment temperature of at most 105 ° C.
• This temperature can be chosen, in general, in the wide range from 15 ° C to 100 ° C, and can preferably be chosen in the range from 30 ° C to 90 ° C, depending on the nature of the clay matrix of the ore .
• the duration of the pretreatment is generally greater than 30 minutes, but: is not a parameter to be controlled of the process according to the invention, it being understood that the pretreatment time is all the longer as the temperature is chosen in the low values of the corresponding interval.
• the medium moistened with the alkaline agent can be subjected to minimal mechanical stirring.
• the disintegration process of the clays which occurs in the presence of an aqueous phase, is inhibited in an almost irreversible manner allowing subsequent treatment to be carried out at the appropriate time.
• upgrading such as for example an acid or alkaline attack in a reactor of pretreated clay-gangue ore, which can without inconvenience include stirring, storage, transfer and separation steps.
• the pretreatment method according to the invention does not subsequently cause limitation of the solubilization yields of the metallic element to be recovered, whatever the type of practical treatment, acid or alkaline, at low temperature.
• a flocculating agent in dilute aqueous solution, generally of a concentration at most equal to one gram per liter, in quantities not exceeding 500 grams per tonne of ore, but always suited to the desired results.
• This example illustrates the behavior of the clay matrix of a urano-vanadiferous ore when the latter is suspended in an aqueous, neutral or alkaline phase, cold or hot, without having been subjected to the pretreatment according to the invention.
• the clays consisted mainly of illite and kaolinite.
• a first test was carried out in the following manner 100 g of this dry ore, ground and passing through a sieve of 500 microns, were placed in a cylindrical reactor of 500 milliliters of total capacity, with 300 g of water introduced with a gradually with stirring, forming a suspension.
• the mixture obtained had, cold as hot (90 ° C), the appearance of a gelatinous paste, which after 24 hours of rest had shown no ability to decant.
• This example illustrates the beneficial influence, on the separation of the liquid and solid phases, of the pretreatment according to the invention of an ore with argillaceous gangue by means of an alkaline agent and more particularly the. various quantities of said agent which can be used, in the form of an aqueous solution, during the moistening of the ore, before heating the ore, before heating the mixture.
• Example 2 the same urano-vanadiferous ore with a clay gangue was pretreated as in Example 1, according to the first variant of the invention, 100 g of this ore (test No. 8), ground and passing through a sieve. 500 microns, were placed in the presence of an amount of sodium hydroxide equivalent to 50 kg per tonne of ore, but in solution in an amount of water such that the ratio of the liquid phase expressed in cubic meters to the phase solid expressed in tonnes has the value of 0.2.
• the pretreatment time which was 1 hour, was counted from the moment when said L / S ratio fell below 0.2 m3 / tonne.
• the four pretreated samples were subjected to a degradation test. This test consisted in introducing each sample of pretreated ore into a cylindrical-hemispherical stainless steel reactor with water according to a ratio of the liquid phases expressed in cubic meters and solid expressed in tonnes equal to 3.
• Each reactor with a capacity of 1 liter, was fitted with a vertical axis turbine, comprising 3 vertical blades, rotating at 375 revolutions per minute.
• the reaction medium was kept at the temperature of 90 ° C for one hour, all these operations being carried out with vigorous stirring.
• the reactor was immersed in cold water in order to cause rapid cooling of the suspension.
• the suspension thus pretreated was subjected to a separation test which consisted in passing the suspension over a Büchner filter by practicing a vacuum of 500 millimeters of mercury, and thus measuring the separation speed. of the liquid phase in cubic meter. hour meter -2 .
• This table reveals, first of all, by comparison with the results of Example 1, the excellent filterability of the clay ore after it has been subjected to the pretreatment according to the invention.
• this table confirms that the value of the L / S ratio in m3 / t of wetting of the clay-gangue ore can be chosen indifferently in the range 0.2 to 0.99, while retaining an excellent ability to filtration.
• This example demonstrates the minimum quantity of the alkaline agent, expressed in kilograms of OH per tonne of clay present in the ore which it is necessary to use to successfully carry out the pretreatment according to the invention.
• test 12 to 19 100 g of this crushed ore and passing through a 500 micron sieve were placed in the presence of increasing amounts of sodium hydroxide, dissolved in an amount of water such that the ratio of the liquid phase expressed in cubic meters to the solid phase expressed in tonnes has the value of 0.3 for each test.
• tests 12 to 19 were then dehydrated according to the first variant of the invention by evaporation until a value of the L / S ratio in m3 / t less than 0.2 (close to 0.15), in an electric oven intended for pretreatment and heated to 130 ° C.
• the temperature at the heart of the sample remained very close to 100 ° C, during evaporation, then rose rapidly to 130 ° C as soon as the L / S ratio in m3 / t became less than 0.2 .
• the pretreatment time which was 1 hour and 15 minutes, was counted from the moment when said L / S ratio became less than 0.2 m3 / tonne.
• the eight pretreated samples were subjected to a degradation test. This test consisted in introducing each sample of pretreated ore into a cylindrical-hemispherical stainless steel reactor with water, according to a ratio of the liquid phases expressed in cubic meters and solid expressed in tonnes equal to 3.
• Each reactor with a capacity of 1 liter, was fitted with a vertical axis turbine, comprising 3 vertical blades, rotating at 375 revolutions per minute.
• the reaction medium was kept at the temperature of 90 ° C for one hour, all these operations being carried out with vigorous stirring.
• the reactor was immersed in cold water in order to cause rapid suspension cooling.
• the suspension thus pretreated was subjected to a separation test which consisted in passing the suspension over a Büchner filter by practicing a vacuum of 500 millimeters of mercury, and thus measuring the speed -1 -2 separation of the liquid phase in cubic meter. Hour meter.
• this table reveals that it is necessary to use a minimum of 4 kg of alkaline agent expressed as OH per tonne of clay so that the effectiveness of the pretreatment can be observed, and that the ore with a clay matrix acquires the ability to separate the liquid and solid phases which are the subject of the invention.
• the pretreatment according to the invention could be carried out at any temperature in the range from 105 ° C to 450 ° C, according to the first variant of the invention.
• test 20 to 26 100 g of this ground ore, and passing through a 500 micron sieve, were placed in the presence of a quantity of sodium hydroxide equivalent to 50 kg per tonne of ore, dissolved in an amount of water such that the ratio of the liquid phase expressed in cubic meters to the solid phase expressed in tonnes has the value of 0.3.
• the pretreatment temperatures were chosen at 105, 110, 130, 150, 180, 250 and 450 ° C.
• This table confirms the excellent results obtained by the application of a process according to the invention when the pretreatment is carried out at a temperature of at least 105 ° C.
• the alkaline agent used in the pretreatment according to the invention could be either sodium hydroxide, potassium hydroxide or a mixture of the two.
• tests 27 to 29 For each of. tests (tests 27 to 29), 100 g of this crushed ore and passing through a 500 micron sieve, were placed in the presence of a quantity of sodium hydroxide, potassium and the mixture of the two hydroxides, equivalent to 30 kg of OH per tonne of ore, dissolved in an amount of water such that the ratio of the liquid phase expressed in cubic meters to the solid phase expressed in tonnes has the value of 0.3.
• This example illustrates the beneficial influence on the separation of the liquid and solid phases of the pretreatment according to the invention of another uraniferous ore with clay gangue by means of an alkaline agent.
• Clays were mainly made up of smectites, attapulgite and sepiolite.
• test 30 Two tests, 30 and 31, were carried out using this ore, one having only undergone the only degradation test (test 30), the other having successively undergone the pretreatment according to the invention and then the degradation, according to the pretreatment and / or degradation protocols described in example 3 of test 17.
• This example relates to and illustrates the pretreatment according to the method of the invention of a urano-molybdenum ore with relatively little clay matrix.
• the product obtained was taken up in water and carbonated in a stirred reactor, then subjected to a filtration test according to the protocol of Example 3.
• test 32 another 100 g sample (test 32) was taken of the same ore on which no pretreatment was carried out and which was immediately subjected to the same degradation test in aqueous phase as previously, but by incorporating 1 g of NaOH into the water of the carbonation reactor.
• This example illustrates the beneficial influence on the separation of the liquid and solid phases of the pretreatment according to the invention on a weakly clayey laterite, using an alkaline agent.
• This laterite containing nickel and cobalt, contained 30% of clay (kaolinite) and was known for its inability to decantation as to filtration once suspended in water.
• This laterite had, after drying, the following composition in% by weight:
• Test 34 corresponds to the only degradation test.
• Test 35 relates to the application of the pretreatment according to the invention followed by the degradation test.
• This example illustrates the application of the process according to the invention to a gold ore with a clay gangue.
• Example 6 a first fraction of 100 g of this ore (test 37) was treated according to the invention, then underwent aqueous recovery in a carbonation reactor, this latter operation constituting the degradation test, while 'a second fraction of 100 g (test 36) of the same gold ore underwent the only degradation test in the same highly agitated reactor.
• Table IX shows the results of the two filtration tests carried out at the end of the above-mentioned respective degradation tests.
• This example illustrates the application of the method according to the invention to a vanadiferous ore with a highly bentonite gangue (95% bentonite).
• test 38 and 39 Two 100 g samples (tests 38 and 39) ground passing through a 500 micron sieve were treated as the two samples of Example 6.
• the first test (test 39) underwent the pretreatment then the degradation test, the second (test 38) only the degradation test.
• the pretreatment according to the invention makes it possible to make a practically pure clay filterable, which, in the absence of said pretreatment could not have been indebted for a hydrometallurgical treatment, such as an acid or alkaline attack.
• This example illustrates the beneficial influence on the separation of the phases. liquid and solid, of the pretreatment according to the invention of an ore with a clay matrix using an alkaline agent and more particularly the various quantities of said agent which can be used, in the form of an aqueous solution, during moistening the ore, prior to heating the mixture to the temperature used for the tests.
• Example 2 the same urano-vanadiferous ore with a clay gangue was pretreated as in Example 1, according to the second variant of the invention.
• This quantity of sodium hydroxide, expressed as OH represented in the moistening medium 30 kg of OH equivalent per tonne of clay contained in the ore.
• test 41, 42, 43 and 44 Four other tests (tests 41, 42, 43 and 44) corresponding to samples of 100 g of the same ore, were carried out by treating said ore with the same amount of sodium hydroxide, but with volumes of water different in such a way that the L / S ratio in m3 / T takes values 0.17 - 0.30 - 0.45 and 0.6.
• the five samples were then placed in an oven for pretreatment and heated to 50 ° C.
• the pre-treatment time was 3 hours.
• the five pre samples treated were subjected to a degradation test. This test consisted in introducing each sample of pretreated ore into a cylindrical-hemispherical stainless steel reactor with water according to a ratio of the liquid phases expressed in cubic meters and solid expressed in tonnes equal to 3.
• Each reactor with a capacity of 1 liter, was fitted with a vertical axis turbine, comprising 3 vertical blades, rotating at 375 revolutions per minute.
• the reaction medium was kept at the temperature of 90 ° C for one hour, all these operations being carried out with vigorous stirring.
• the reactor was immersed in cold water in order to cause rapid cooling of the suspension.
• the suspension thus pretreated was subjected to a separation test which consisted in passing the suspension over a Büchner filter by practicing a vacuum of 500 millimeters of mercury, and thus measuring the speed of separation of the liquid phase in cubic meters. hour -1. meter -2 .
• This table reveals, first of all, by comparison with the results of Example 1, the good ability to filter the clay ore after it has been subjected to the pretreatment of the second variant according to the invention.
• this table confirms for this particular ore that the value of the L / S ratio in m3 / T of wetting of the ore with clay matrix can be chosen indifferently in the range 0.1 to 0.4, while retaining a good filtration ability.
• test 45 to 50 100 g of this crushed ore passing through a 500 micron sieve were placed in the presence of increasing amounts of sodium hydroxide, dissolved in an amount of water such that the ratio of the liquid phase expressed in cubic meters at the solid phase expressed in tonnes has the value of 0.3 for each test.
• tests 45 to 50 were then placed in an oven intended for pretreatment and heated to 50 ° C.
• the pretreatment time was 3 hours.
• the six pretreated samples were subjected to a degradation test.
• This test consists in introducing each sample of pretreated ore into a cylindrical-hemispherical stainless steel reactor with water, according to a ratio of the liquid phases expressed in cubic meters and solid expressed in tonnes equal to 3.
• Each reactor with a capacity of 1 liter, was fitted with a vertical axis turbine, comprising 3 vertical blades, rotating at 375 revolutions per minute.
• the reaction medium was kept at the temperature of 90 ° C for one hour, all these operations being carried out with vigorous stirring.
• the reactor was immersed in cold water in order to cause rapid cooling of the suspension.
• the suspension thus pre treated was subjected to a separation test which consisted in passing the suspensions on a Büchner filter by practicing a vacuum of 500 millimeters of mercury, and thus measuring the speed of separation of the liquid phase in cubic meters. hour -1. meter -2 .
• this table reveals that it is necessary to use a minimum of 4 kg of alkaline agent expressed as OH per tonne of clay so that the effectiveness of the pretreatment can be observed, and that the ore with a clay matrix acquires the ability to separate the liquid and solid phases which are the subject of the invention.
• the pretreatment according to the invention could be carried out at any temperature in the range from 25 ° C to 100 ° C, when use is made of the second variant according to the invention .
• tests 51 to 57 100 g of this crushed ore, and passing through a 500 micron sieve, were placed in the presence of a quantity of sodium hydroxide equivalent to 60 kg per tonne of ore, dissolved in an amount of water such that the ratio of the liquid phase expressed in cubic meters to the solid phase expressed in tonnes has the value of 0.3.
• the pretreatment temperatures were chosen at 25, 30, 50, 60, 80 and 100 ° C.
• the alkaline agent used in the pretreatment according to the invention could be indifferently sodium hydroxide, potassium hydroxide, ammonium hydroxide, calcium hydroxide -or a mixture-
• This example illustrates the beneficial influence on the separation of the liquid and solid phases of the pretreatment according to the invention of another uraniferous ore with clay gangue by means of an alkaline agent, by use of the second variant.
• a clay uranium ore was used having, after drying, the following composition in% by weight:.
• the clays consisted mainly of smectite, atta-. pulgite and sepiolite.
• test Nos. 63 and 64 Two tests, Nos. 63 and 64, were carried out from this ore, one having only undergone the only degradation test (test No. 63), the other having successively undergone the pretreatment according to the invention then the degradation test, according to the pretreatment and / or degradation protocols described in test No. 49 of Example 12.
• This example relates to and illustrates, allegedly according to the method of the invention, a urano-molybdeniferous ore with relatively little clay matrix by use of the second variant.
• the solid thus moistened was placed in an oven brought to 50 ° C. for 180 minutes.
• the product obtained was taken up in water and carbonated in a stirred reactor, then subjected to a filtration test according to the protocol of Example 12.
• test no. 65 another 100 g sample (test no. 65) was taken of the same ore on which no pretreatment was carried out and which was immediately subjected to the same degradation test in aqueous phase as previously. , but by incorporating 1 g of NaOH into the water of the carbonation reactor.
• the process of the invention also makes it possible to improve the filterability of a low-clay urano-molybdenum ore.
• This example illustrates the beneficial influence on the separation of the liquid and solid phases of the pretreatment according to the invention on a slightly clayey laterite, by means of an alkaline agent, by application of the second variant.
• This laterite containing nickel and cobalt, contained 30% of clay (kaolinite) and was known for its inability to decantation as to filtration once suspended in water.
• This laterite had, after drying, the following composition in% by weight:
• Test No. 67 corresponds to the only degradation test.
• Test No. 68 relates to the application of the pretreatment according to the invention, followed by the degradation test.
• This example illustrates the application of the process according to the invention to a gold ore with a clay gangue.
• Example 15 As in Example 15, a first fraction of 100 g of this ore (test No. 70) was treated according to the invention, then underwent aqueous recovery in a carbonation reactor, this latter operation constituting the degradation test, while a second fraction of 100 g (test no. 69) of the same gold ore underwent the only degradation test in the same highly agitated reactor.
• Table XVIII indicates the results of the two filtration tests carried out at the end of the respective abovementioned degradation tests.
• Tests No. 72 to 75 underwent the pretreatment and then the degradation test, while test No. 71 underwent only the degradation test.
• the pretreatment according to the invention makes it possible, by adapting the L / S ratio according to the nature and the quantity of the clay, to make filterable a mineral even consisting of practically pure clay, and which, in the absence of said pretreatment does not could have been indebted for hydrometallurgical treatment, such as an acid or alkaline attack.

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