JPH021093B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a novel combination of alkaline attack of molybdenum-containing materials using aqueous solutions of alkaline carbonates, bicarbonates or hydroxides, and precipitation of the eluted molybdenum in an acid medium. 3. Concerning the method for collecting in the shape of ₃ . Alkaline attack of molybdenum (MoS ₂ ) by aqueous carbonate solutions has been known for a long time. For example, “GMELIN HANDBUCH,
MOLYBDA¨N, A ₁ edition - Technologie des
Metals, 1977, pages 31-34, describes several methods of alkaline attack of molybdenum-containing ores such as those mentioned above. In the first method, a pre-roasted molybdenite concentrate is heated to Erosion with an aqueous carbonate solution for 1 to 2 hours at ℃.The weight ratio of ore to aqueous etching solution is at least equal to 5 to ensure that the molybdenum is leached in the form of alkaline molybdate into the erosion medium. Furthermore, the authors propose to improve the method by increasing the erosion temperature to increase the leaching rate.The erosion temperature is increased in the range below 300°C, i.e. always at a pressure below 50 bar. This improved method also yields an aqueous solution of alkaline molybdate.Then, the aqueous solution is treated with iron or calcium sulfides or salts under suitable acidic conditions. , molybdenum can be precipitated in the form of sulfides or iron or calcium molybdates, and these precipitates can be recovered by phase separation. They have the following disadvantages and thus limit the industrial development of these methods.Furthermore, the treatments carried out for the recovery of molybdenum leached by erosion are
Sometimes it is expensive and sometimes it is not possible to obtain molybdenum compounds of sufficient industrial grade.
For example, recovering sodium molybdate from its aqueous solution requires evaporation of most of the aqueous phase. This creates, on the one hand, a high consumption of thermal energy, and, on the other hand, a serious risk that other sodium salts present during erosion, in particular excess erosive agent, will precipitate at the same time. Furthermore, precipitating molybdenum in the form of molybdenum sulfide or iron or calcium molybdates requires the use of precipitants that are different from the erosion medium, and one of the ionic groups of these precipitants is responsible for the molybdenum in the precipitate. and form new impurities. The quality of the molybdenum concentrate obtained is therefore reduced. For example, when molybdenum is precipitated in the form of calcium molybdate for metallurgical purposes, the precipitate must be subjected to a new conversion process in order to obtain an industrially usable form, usually in the form of the oxide _MoO3 . It won't happen. Also, the use of Na ₂ S as a precipitant has the serious drawback of generating H ₂ S gas. Containment of _H2S gas is extremely difficult and therefore poses a real danger to personnel. On the other hand, the acid hydrolysis treatment of aqueous solutions of alkaline molybdates is also known. “Nuvo Trete Dough Stain Mineral” by Paul Pascal
Nouveau Traite′ de Chimie Mine′rale”XIV
Vol., published in 1959, page 664, in the method for hydrolyzing alkaline molybdate, an aqueous solution of the molybdate is acidified with hydrochloric acid, the resulting liquid is heated to a temperature of about 70°C, and the formula _MoO3・_H2O
Precipitate the monohydrated oxide of. In this method, the hydrolysis reaction is slow and the resulting precipitate has very small, hexagonal-looking white crystals that are difficult to filter and wash. This creates problems regarding industrial purity and utilization. An aqueous solution of alkaline molybdate is formed by acidification of the medium with sulfuric acid or by oxidation of the sulfur initially present SO ₄ ⁼
If it also contains (SO ₄ ^2- ) ions, the ions SO ₄ ⁼
The hydrolysis is difficult and may even be impossible because complexation of MoVI occurs as shown in the formula MoO ₃ +H ₂ SO ₄ MoO ₂ (SO ₄ )H ₂ O. Regarding this,
“Russian Journal of Inorganic Chemistry”15
(5), 1970, page 697 FYIRKOV, A.A. Pallant AA
PALANT and V.A. Reznichenko V.
A. REZNICHENKO's paper “Solubility of anhydrous molybdenum VI oxide in aqueous sulfuric acid solution”
Anhydrous Molybdenum VI Oxide in
Finally, the first cited document mentions that methods exist for the oxidation of aqueous suspensions of concentrated molybdenite (MoS ₂ ) by oxygen injection at high temperatures. One of these methods is described, for example, in French Patent Application No. 2064092, in which the formula MoS ₂ +9/2O ₂ +2H ₂ O→MoO ₃ +2H ₂ SO ₄ To effect the indicated conversion reaction, the material containing molybdenum disulfide is dispersed in water to form an aqueous slurry, heated to 150° to 250° C., and stirred while contacting an atmosphere containing free oxygen. Both the partial pressure of free oxygen and the contact duration must be sufficient for conversion of at least some of the MoS ₂ to occur.The conversion reaction naturally makes the reaction medium increasingly acidic and the MoO ₃ However, since the reaction medium becomes increasingly acidic, the oxidation efficiency of molybdenum sulfide is not sufficient.According to the examples of the patent, the efficiency is between 54.1% and 54.1%.
There is a variation in the range of 89.8%. For this reason, US Pat. No. 4,165,362 proposes an improvement to the method. In the improved method, a temperature of 150°C to 230°C is used to oxidize an aqueous suspension of molybdenite according to the formula MoO ₂ +9/2O ₂ +3H ₂ O →MoO ₃ ·H ₂ O + 2H ₂ SO ₄ Oxygen is injected into the medium to convert the molybdenum sulfide. At this time, a sufficient amount of alkaline hydroxide is introduced to neutralize some of the sulfuric acid generated by the reaction, and the treatment medium is Maintain pH between 0.05 and 0.5. According to the improved method described above, the oxidation efficiency of molybdenite is certainly improved. However, for example
Despite the use of high temperatures such as 195° C., the disadvantage remains that the reaction times are too long, ranging from 2 to 4 hours. Furthermore, the pressure also increases due to the introduction of oxygen at a partial pressure of 200 to 400 psi (ie approximately 14 to 28 bar). Finally, the method does not dissolve molybdenum in the eroding reaction medium. Therefore, all the impurities originally present in the molybdenite and insoluble in the erosion medium are
Since it accompanies the obtained molybdenum oxide, purification treatment to remove impurities is required as a post-treatment. The applicant continued his research to eliminate the above-mentioned drawbacks and achieved a method for recovering molybdenum in the form of anhydrous MoO ₃ by precipitation using a liquid obtained by alkaline attack of molybdenum-containing materials. The method of the present invention for recovering molybdenum in the form of anhydrous _MoO3 consists of high-temperature alkaline attack of molybdenum-containing materials, separation of a liquid phase containing dissolved molybdenum obtained by the attack and a solid phase consisting of waste, and extraction of molybdenum. processing of the liquid phase for A feature of the method of the invention is that molybdenum-containing substances are attacked using an aqueous solution of alkaline carbonates, hydrogen carbonates or hydroxides, the alkaline liquid phase obtained by the attack is then acidified, and then the solution phase to a temperature of at least
It involves a novel combination of heating to 120°C. Molybdenum-containing materials that can be treated by the method of the invention are molybdenum-containing ores with or without uranium, concentrated molybdenite, residual calcium molybdate as a by-product of uranium hydrometallurgy, spent catalysts, and the like. The material may contain sulfur that is not bonded to molybdenum. Depending on the nature of the molybdenum-containing material to be treated by the method of the invention, an alkaline solution containing an alkaline carbonate, bicarbonate or hydroxide is used to alkali attack the molybdenum-containing material as described above. After molybdenum is converted to alkaline molybdate and sulfur is converted to alkaline sulfate, CO ₃ ⁼ (CO ₃ ^2- ) is 100g/
Less than 100g/HCO ₃ ^- , 150g/OH ^-
CO ₃ ⁼ , HCO ₃ ^- and OH ^- such that less than g/g/
Use an alkaline solution with a concentration of . In order to obtain such a concentration after erosion, the reagent is used in the form of an aqueous solution or suspension, taking into account the amount of reagent consumed during erosion. alkaline carbonates, used as erosion agents;
As hydrogen carbonates or hydroxides, in practice sodium and potassium carbonates, hydrogen carbonates or hydroxides are used. The temperature range for carrying out the erosion can be selected from a wide range. Usually temperatures below 300°C are used, preferably temperatures between 80°C and 250°C. The duration of the attack depends on the nature of the molybdenum-containing material and the temperature of use. Usually, the time is from several minutes to 6 hours. As is well known, when molybdenum-containing materials contain reducing elements such as sulfur and organic substances, attack is carried out in the presence of oxidizing agents. Usually this oxidant is oxygen, which is blown into the reaction medium in the form of oxygen-enriched air or in the form of oxygen alone. The oxygen partial pressure within the reactor is between 0.1 and 40 bar, preferably between 5 and 15 bar. However, for the erosion of uranium-containing ores, it is also possible to obtain an oxidizing medium by introducing a liquid or solid oxidizing agent under standard conditions, such as oxygenated water or sodium peroxide. It is. In the case of certain ores as a special lease,
such as Fe compounds or cuprammonium compounds,
It has been found that the introduction of conventional oxidation catalysts into the reaction medium is advantageous for promoting the kinetics of erosion. When the erosion is carried out at temperatures above the boiling point, the suspension after the erosion is cooled to bring the cooled medium below the boiling point. Cooling as described above is performed by a known method.
Cooling may be carried out, for example by expansion, and/or
Alternatively, in the case of a continuous process, countercurrent exchange may be carried out between the post-erosion suspension and the pre-erosion suspension. When cooling by expansion, a certain amount of water evaporates depending on the temperature at which the erosion is carried out, so that it is possible to obtain a much more concentrated liquid phase without expending thermal energy. As described above, when cooling is performed only by direct heat exchange between the two suspensions, no evaporation occurs. Immediately after cooling is completed, the liquid phase and solid phase of the suspension are separated. The separated solid phase consisting of useless components is washed with water. The cleaning solution is usually reused to attack molybdenum-containing materials. The liquid phase obtained by separation of the suspension after erosion is acidified using either nitric acid, hydrochloric acid or sulfuric acid. The weight of free acid after acidification of the liquid is 2 to 20% of the total weight of the liquid phase after acidification, preferably 5 to 15%.
Select the amount of acid to be used so that %. The CO ₃ ⁼ and HCO ₃ ⁻ ions that were initially present in the liquid phase before the acidification treatment are removed in the form of CO ₂ evolution. In practice, the acidified liquid phase constituting the molybdenum-containing feed liquid must be at least 0.5% of the weight of the acidified liquid phase.
%, preferably at least 2%. The acidified liquid phase is then heated in an autoclave.
The heating temperature is selected in the range of 120°C to 250°C, preferably in the range of 140°C to 180°C to cause precipitation of anhydrous MoO ₃ . The duration of maintaining the temperature in the above range is usually between 0.5 and
Although it is 10 hours, this time itself is not critical. In order to improve the physical properties of anhydrous MoO ₃ crystals, such as those that affect the suitability of the reaction medium and the phenomenon of crust deposition on the reactor walls, the precipitation medium of MoO ₃ is seeded with a small amount of anhydrous MoO ₃ . It is advantageous to introduce it as The aqueous suspension of anhydrous MoO ₃ obtained as described above is cooled to a temperature that allows solid-liquid separation, and then a separation treatment is performed to separate the precipitate of anhydrous MoO ₃ from nitrate, hydrochloride, and sulfate. An acidic mother liquor containing alkaline salts such as alkaline salts alone or in a mixture may be recovered. The anhydrous MoO ₃ precipitate is then washed. The precipitate of anhydrous MoO ₃ impregnated with the mother liquor is washed with an aqueous acid solution, preferably an aqueous acid solution containing an amount of water capable of solubilizing a significant portion of the precipitate. The pH of the acidic aqueous solution for cleaning is preferably 1 to 2. The washing solution of the anhydrous MoO ₃ precipitate and the acidic mother liquor obtained from the separation are mixed. This mixture often forms a molybdenum-poor effluent.
It is also possible to treat this waste liquid with lime to neutralize the acidity and precipitate residual molybdenum. However, in many cases it is advantageous to reuse the acid mixture described above as an auxiliary agent for acidifying the molybdenum-containing liquid after erosion. In this case, the acidic mixture is previously treated to remove dissolved alkaline salts. Any known method may be used for the removal treatment, particularly evaporation and crystallization of the alkaline salt. Finally, the applicant has confirmed that when molybdenum-containing materials are treated with the method of the invention, anhydrous MoO ₃ is obtained. This anhydrous MoO ₃ was specifically identified by X-ray spectrography. According to the spectrograph, when cobalt is used as an anticathode and the lattice spacing dA between various lattice planes is expressed in angstroms,
It has been found that the anhydrous MoO ₃ obtained by the method of the present invention exhibits spectral lines having the same lattice spacing and relative intensity as the anhydrous MoO ₃ crystallized in a hexagonal system.

[Table] The method of the invention for recovering molybdenum in the form of anhydrous MoO ₃ having the characteristics as described above can be carried out by a process comprising the following steps. (a) Hot attack of molybdenum-containing materials by alkaline liquids or suspensions containing alkaline carbonates, bicarbonates, hydroxides at temperatures below 300°C, preferably between 80°C and 250°C. After erosion, respectively,
CO ₃ ^-- is less than 100g/HCO ₃ ^- is 100g/
Erosion is carried out to achieve a concentration of less than 150 g/OH ^- . (b) Blowing an oxidizing agent, such as oxygen, into the erosion medium if the molybdenum-containing material contains reducing elements, such as sulfur. (c) Cooling of the suspension after erosion. This is done in such a way that the temperature of the medium after cooling is below the boiling point. (d) Separation of a first precipitate formed from non-erodible waste and impregnated with mother liquor. (e) Washing of the first precipitate to extract the impregnated liquid. The used wash water is either reused for erosion or added to the liquid obtained in separation (d). (f) Acidification of the liquid phase after separation (d) with either nitric acid, hydrochloric acid or sulfuric acid. The amount of acid used is selected such that the weight of free acid in the liquid is between 2 and 20% of the total weight of the liquid phase after acidification. Optional introduction of a small amount of anhydrous MoO ₃ into the acidified liquid phase, which acts as a seed crystal. (h) Heating the acidified liquid phase at a temperature of 120°C to 250°C, typically maintained for less than 10 hours. This causes precipitation and a suspension of anhydrous MoO ₃ is obtained. (i) Separation of solid and liquid phases of an aqueous suspension of precipitated anhydrous MoO ₃ . This makes it possible to recover a second precipitate formed from anhydrous MoO ₃ and an acidic mother liquor containing alkaline salts such as nitrates, hydrochlorides and sulfates, alone or in combination. (j) Acid solution washing of anhydrous MoO ₃ precipitate impregnated with mother liquor. (K) Mixing of the washing solution of precipitated anhydrous MoO ₃ with the acidic mother liquor after separation (i). The present invention will be more fully understood from the following description based on the accompanying drawings. The figure is a schematic explanatory diagram of the method of the present invention. The solid line shows the circuit used when it is desired to recover only molybdenum, and the dotted line shows the circuit for implementing various processes. Various treatments include additional purification of organic matter, carbonation, concentration, removal of alkaline sulfates or additional treatments carried out for these purposes or recycling of the liquid at various points in the cycle of the process according to the invention. refers to additional processing, etc. performed for the purpose of According to the figure, the divided molybdenum-containing material and the erosion liquid consisting of fresh reagent and recycle liquid L ₄ are introduced into the heated reactor A. If necessary, it is also possible to simultaneously blow oxygen into the reaction medium in the reactor. The suspension after erosion is cooled by expansion at B, and a predetermined amount of water is removed to form a cooled suspension _L1 . The suspension L ₁ is introduced into C, a cake S ₂ consisting of the waste portion of the mother liquor, an aqueous solution L ₂ in which carbonates, hydrogen carbonates or hydroxides of alkali metals and eluted molybdenum are dissolved; separated into The mother liquor of cake _S2 is removed in D with water. All or part of the mother liquor L ₃ removed in this way is recycled and used for erosion as a liquid L ₄ . If part of the mother liquor is recycled for erosion,
The _remaining part of the mother liquor from washing zone D is C.
It is added to the raw material aqueous solution after separation in . The molybdenum-containing aqueous solution _L2 is usually subjected to an acidification treatment induced by F. However, preferably the liquid _L2 is divided into two parts, one fraction _L7 is recycled for erosion, and the remaining fraction _L6 is sent directly to the acidification zone F or after washing in D. Mix the recycled liquid _L5 to form liquid _L8 . Liquid L ₆ obtained by fractionating molybdenum-containing liquid L ₂
The aqueous solution L ₈ obtained by mixing and liquid L ₅ is directly guided to the acidification zone. However, in step E, it is advantageous to subject the molybdenum-containing liquid _L8 to at least one of various treatments, such as concentration treatment by evaporation and organic matter removal treatment. In this case, the molybdenum-containing liquid L ₉ coming out of E is introduced into an acidification zone F using one of the above-mentioned strong acids and then, if necessary, seeded.
Anhydrous MoO ₃ is heated in precipitation zone G to which MoO ₃ is added. The suspension leaving the precipitation zone G is introduced into the zone H, where it is separated into a cake S ₁₀ consisting of precipitated MoO ₃ impregnated with mother liquor and a liquid L ₁₀ . Cake ₁₀ is introduced into zone I and washed with water.
yields L ₁₁ . Liquid L ₁₁ is added to liquid L ₁₀ to form liquid L ₁₂ . The cake S ₁₁ after washing consists of anhydrous MoO ₃ and is practically free of impurities. Liquid L ₁₂ is discharged in a discontinuous manner. Alternatively, liquid L ₁₂ is directed to treatment zone J as indicated by L ₁₄ . Concentration, for example by evaporation, takes place in this zone. When the molybdenum-containing starting material contained sulfur and/or SO ₄ ⁼ ions were dissolved in the liquid due to the use of sulfuric acid to acidify the molybdenum-containing liquid L ₉ , the above-mentioned evaporative concentration treatment Alkali metal sulfates can be precipitated by. In zone K, the solid phase S ₁₅ and the liquid phase L ₁₅ are separated, and the liquid L ₁₅ is recycled to zone F, where the acidification of the molybdenum-containing liquid L ₉ takes place. Example 1 Calcium molybdate, a by-product of uranium extraction using an acidic method, was treated by the method of the present invention. Calcium molybdate had the following composition. Molybdenum 33.3% Uranium 1.6% Phosphorus 0.45% Bound CO ₃ 5.2% Bound SO ₄ 2.05% Calcium 17.85% SiO ₂ 0.19% Impurities + Water + Oxygen 39.36% 1000 g of the above molybdenum-containing material was placed in zone A in an aqueous suspension of sodium carbonate. It was eroded by muddy liquid.
This suspension is made by adding 450g to 870g of washing liquid _L4 .
It consisted of Na ₂ CO ₃ suspended, and the liquid L ₄ had the following composition. Molybdenum 95.6 g Na ₂ CO ₃ 25.0 g SO ₄ 6.0 g Water + Impurities 74.34 g The stirred reactor A was heated until the reaction medium reached a temperature of 95° C. and the erosion medium was maintained at this temperature for 5 hours. After erosion, suspension L ₁ is introduced into zone C and solid S ₂
and liquid _L2 were separated. The cake S ₂ impregnated with liquid L ₂ weighed 1050 g. When this was washed with 830 g of water in zone D, the above-mentioned liquid _L4 was produced. The weight of Cake _S3 after washing was 1012 g. Liquid _L2 coming out of separation zone C weighed 1268 g and had the following composition. Molybdenum 311 g Na ₂ CO ₃ 81 g SO ₄ 20 g Water + impurities 856 g This liquid L ₂ was acidified with 1275 g of 32% hydrochloric acid in zone F, producing 33 g of CO ₂ . Put the acidified liquid L ₂ into autoclave G,
1 g of anhydrous MoO ₃ was present as seed crystals and heated at 160° C. for 3 hours. After 3 hours, 2510 g of anhydrous MoO ₃ suspension had precipitated. This was cooled to 60° C. and decanted in zone H to perform solid-liquid separation to produce cake S ₁₀ and liquid L ₁₀ . Liquid L ₁₀ weighed 1950 g and had the following composition. Molybdenum 5g SO ₄ 19g NaCl 445g HCl 109g Water + Impurities 1372g 400g acidified with 1% HCl in Zone I
Wash the cake S ₁₀ with water and the cake with anhydrous MoO ₃
S ₁₁ and liquid L ₁₁ were produced. cake impregnated with water
S ₁₁ weighed 595 g and had the following weight composition. Anhydrous MoO ₃ 451.5 g Water 141.0 g NaCl 2.4 g Impurities 0.1 g After washing, a mixture of liquid L ₁₀ and liquid L ₁₁ was collected. The mixture weighed 2315 g and had the following composition. Molybdenum 10 g NaCl 468 g HCl 119 g Water + impurities 1718 g Example 2 Concentrated molybdenite containing 75% MoS ₂ was treated with the method of the invention. 1000 g of the molybdenum-containing material was mixed with 6000 g of 20% NaOH aqueous solution in autoclave A.
It was eroded using a cleaning solution _L4 having the composition shown below. Molybdenum 14g NaOH 2.7g Na ₂ SO ₄ 40.7g Water + Impurities 454.6g While maintaining the temperature of the erosion medium in the range of 180°C to 220°C for 1 hour, 750% oxygen was injected to remove the 75% surplus. When the suspension after erosion was expanded, 1100 g of water was separated and a suspension L ₁ was obtained which was cooled to 80°C.
The suspension _L1 was introduced into zone C and separated into a solid phase _S2 and a liquid phase _L2 . The weight of cake S ₂ impregnated with liquid L ₂ was 470 g. This cake was washed with 700 g of water in zone D to produce liquid L ₄ and cake S ₃ .
Cake S ₃ weighed 450 g after washing and contained only 7 g of molybdenum. Liquid L ₂ coming out of separation zone C weighed 6805 g and had the following composition. Molybdenum 443 g NaOH 87 g Na ₂ SO ₄ 1310 g Water + impurities 4965 g This liquor L ₂ was then acidified in zone F with 2220 g HNO ₃ 65% nitric acid. Put the acidified liquid L ₂ into autoclave G,
160 °C in the presence of 1 g of anhydrous _MoO3 as seed crystals.
It was heated for 3 hours. After 3 hours, 9005 g of anhydrous MoO ₃ suspension had precipitated. This was cooled to 60°C and decanted in zone H to perform solid-liquid separation to produce cake S ₁₀ and liquid L ₁₀ . Liquid L ₁₀ weighed 8153 g and had the following composition. Molybdenum 34g NaNO ₃ 952g Na ₂ SO ₄ 1271g Water + Impurities 5896g 2000g acidified with 1% HNO ₃ in zone
Cake S ₁₀ was washed with water to obtain anhydrous MoO ₃ cake S ₁₁ and liquid L ₁₁ . The water-impregnated cake S ₁₁ weighed 842 g and had the following composition: MoO ₃ 612.0 g Water 226.0 g HNO ₃ 2.0 g Na ₂ SO ₄ 1.8 g Impurities 0.2 g After washing, a mixture of liquid L ₁₀ and liquid L ₁₁ was collected.
The mixture weighed 10,163 g and had the following composition. Molybdenum 35g NaNO ₃ 980g HNO ₃ 726g Na ₂ SO ₄ 1308g Water + impurities 7114g Example 3 1000g of catalyst after being used for hydrogenation was treated according to the method of the invention. This material had the following weight composition: Al ₂ O ₃ 72.0% by weight Molybdenum 6.9 % Cobalt 2.9 % Nickel 0.017 % Lead 3.46 % Iron 1.0 % SiO ₂ 0.91 % Sulfur 0.82 % Impurities 11.993 % Molybdenum-containing materials into autoclave A, It was eroded by 6839g of eroding liquid. An eroding solution having the following composition was used. Molybdenum 835 g Na ₂ CO ₃ 564 g Na ₂ SO ₄ 453 g NaOH 70 g Water + impurities 4917 g This solution is made from a mixture of liquid L ₄ and liquid L ₇ , 140 g of 50% sodium hydroxide solution and 45 g of solid Na ₂ CO ₃ Become. Liquid _L4 weighed 2722 g and had the following composition. Molybdenum 198g Na ₂ CO ₃ 120g Na ₂ SO ₄ 108g Water + impurities 2296g Liquid L ₇ weighed 3932g and had the following composition. Molybdenum 637g Na ₂ CO ₃ 399g Na ₂ SO ₄ 345g Water + Impurities 2551g Autoclave A was stirred and heated so that the reaction medium was maintained at a temperature of 220°C for 1 hour.
60g of oxygen was injected and 10g of excess was removed. After erosion, the suspension expanded and 1420 g of water separated, producing a cooled suspension L ₁ at 85 °C. This suspension L ₁ was introduced into zone C, and separation into solid phase S ₂ and liquid phase L ₂ was performed. Cake S ₂ impregnated with liquid L ₂ weighed 3160 g. This cake was washed with 2500 g of water in zone D to produce liquid L ₄ and cake S ₃ .
After washing, Cake _S3 weighed 1913 g and had the following composition. Molybdenum 4.2g Na ₂ CO ₃ 7.0g Sulfur 0.2g Na ₂ SO ₄ 2.2g Water + impurities 1899.4g Liquid L ₂ discharged from separation zone C weighed 4332g and had the following composition. Molybdenum 702 g Na ₂ CO ₃ 440 g Na ₂ SO ₄ 380 g Water + impurities 2810 g Liquid L ₂ was fractionated into liquid L ₇ with a weight of 3932 g and liquid L ₈ with a weight of 400 g, which were recycled for erosion. Liquid _L8 had the following composition. Molybdenum 64.8 g Na ₂ CO ₃ 40.6 g Na ₂ SO ₄ 35.1 g Water + impurities 259.5 g This liquid L ₈ was acidified with 350 g of 50% sulfuric acid in zone F, producing 17 g of CO ₂ . Put the acidified liquid L ₈ into autoclave G,
1 g of anhydrous MoO ₃ was present as seed crystals and maintained at 160° C. for 3 hours. After 3 hours, 733 g of anhydrous MoO ₃ suspension had precipitated. This was cooled to 60° C. and then decanted in zone H for solid-liquid separation to produce cake S ₁₀ and liquid L ₁₀ . Liquid L ₁₀ weighed 560 g and had the following composition. Molybdenum 10.3g Na ₂ SO ₄ 185.0g H ₂ SO ₄ 91.0g Water + Impurities 273.7g 100g acidified with 1% sulfuric acid in Zone I
Wash Cake S ₁₀ with water and Cake S ₁₁ of anhydrous MoO ₃ .
and liquid L ₁₁ were produced. The water-impregnated cake S ₁₁ weighed 101 g and had the following composition: MoO ₃ 76.5 g Na ₂ SO ₄ 0.3 g H ₂ SO ₄ 0.2 g Water + impurities 24.0 g After washing, a mixture of liquid L ₁₀ and liquid L ₁₁ was collected.
This mixture weighed 832 g and had the following composition. Molybdenum 13.8g Na ₂ SO ₄ 184.0g H ₂ SO ₄ 106.0g

[Brief explanation of drawings]

The accompanying drawings are schematic illustrations of the method of the invention. A...Reactor, B...Expansion zone, C...Separation zone, D...Washing zone, E...Various treatment zones, F...Acidification zone, G...Precipitation zone, H
... Separation zone, I ... Washing zone, J ... Concentration zone, K ... Separation zone, L ... Liquid, S ... Cake.

Claims (1)

[Claims] 1. High-temperature alkali erosion of a molybdenum-containing material in a divided form in order to recover molybdenum in the form of anhydrous MoO ₃ , and a solid phase consisting of an eluted molybdenum-containing liquid phase and waste obtained by the erosion. separation of
A method for the recovery of molybdenum comprising: treatment of the molybdenum with an acidic medium in the liquid phase to extract the molybdenum; anhydrous MoO ₃ by acidification of the alkaline liquid phase after erosion and heating to a temperature of at least 120 °C under pressure.
and the amount of acid is selected such that the weight of free acid after acidification is between 2% and 20% of the total weight of the liquid phase after acidification. Characteristic molybdenum recovery method. 2 Alkaline erosion of molybdenum-containing substances causes CO ₃ ⁼ ,
It is carried out using an alkaline liquid containing HCO ₃ ^- or OH ^- , and after molybdenum is converted to MoO ₄ ^2- and sulfur is converted to SO ₄ ^2- , the concentration of CO ₃ ^2- is 100
The method for recovering molybdenum according to claim 1, characterized in that HCO ₃ ^- is less than 100 g/, or OH ^- is less than 150 g/. 3. Claims 1 or 2, characterized in that the alkaline carbonate, hydrogen carbonate or hydroxide is formed from sodium or potassium.
Molybdenum recovery method described in section. 4. The method for recovering molybdenum according to any one of claims 1 to 3, wherein the alkali attack of the molybdenum-containing substance is carried out in the presence of an oxidizing agent. 5 Erosion temperature is less than 300℃, preferably 80℃
2. The method for recovering molybdenum according to claim 1, wherein the temperature is from .degree. C. to 250.degree. 6. The method for recovering molybdenum according to any one of claims 1 to 4, wherein the alkali attack of the molybdenum-containing substance is carried out in the presence of an oxidation catalyst. 7. Claim characterized in that the weight of free acid after acidification of the alkaline liquid phase obtained by erosion is preferably in the range from 5% to 15% of the total weight of said liquid phase after acidification. The method for recovering molybdenum according to item 1. 8 The molybdenum-containing liquid phase obtained by erosion and acidification is at least 0.5 of the weight of the acidified liquid.
% preferably equal to at least 2% by weight of molybdenum. 9. The method for recovering molybdenum according to claim 1, characterized in that the precipitation of anhydrous MoO ₃ occurs in the presence of MoO ₃ seed crystals. 10 The acidified liquid phase produced by erosion is heated to 120°C to 250°C, preferably 140°C to 180°C.
The method for recovering molybdenum according to claim 1, wherein the molybdenum is heated to a temperature in the range of . 11. The method for recovering molybdenum according to claim 1, wherein the alkaline liquid phase generated by erosion is concentrated before acidification. 12 If the molybdenum-containing substance contains sulfur, before recycling all or part of the liquid phase obtained after precipitation and separation of anhydrous MoO ₃ for acidification of the alkaline liquid phase produced by erosion. The method for recovering molybdenum according to claim 1, characterized in that the molybdenum is concentrated to remove alkaline salts. 13. The method for recovering molybdenum according to claim 1, wherein the precipitate of anhydrous MoO ₃ obtained by separation from the acidified alkaline liquid phase is washed with an acidic aqueous solution. 14. The method for recovering molybdenum according to claim 13, wherein the pH of the cleaning acidic aqueous solution is in the range of 1 to 2. 15. Process for the recovery of molybdenum according to claim 12, characterized in that the acidification of the molybdenum-containing liquid phase produced by erosion is carried out at least partially using a recirculated liquid.