Method for extracting and recovering molybdenum from alkaline solution by using methyl carbonate quaternary ammonium salt extracting agent

Abstract

The invention discloses a method for extracting and recovering molybdenum from an alkaline solution by using a methyl carbonate quaternary ammonium salt extracting agent, which comprises the following steps: directly mixing the extracting agent methyl carbonate quaternary ammonium salt with a phase regulator and a diluent to obtain an extracted organic phase, and directly mixing the extracted organic phase with an alkaline molybdenum-containing solution for molybdenum extraction, and washing the loaded organic phase with a sodium hydroxide solution, then washing with pure water, and then carrying out reverse extraction. The adopted methyl carbonate quaternary ammonium salt extraction agent does not contain chlorine, can be used without transformation, is high in extraction rate, low in extraction agent loss, fast in phase splitting and free of emulsification, can avoid precipitation and three phases in the extraction process, and is simple in use step and low in cost.

Description

Technical Field

[0001] The invention relates to the technical field of molybdenum smelting, and in particular to a method for extracting and recovering molybdenum using an alkaline solution using a quaternary ammonium salt of methyl carbonate as an extractant. Background Art

[0002] Molybdenum, a globally strategic minor metal, possesses excellent electrical conductivity, wear resistance, corrosion resistance, and high-temperature resistance, and is primarily used in alloy manufacturing and new energy sectors. Molybdenum occurs primarily in nature as single molybdenum ores and copper-molybdenum associated ores, both in the form of MoS2.

[0003] The smelting of molybdenum concentrate usually involves roasting and desulfurization followed by alkaline leaching, including ammonia leaching and sodium hydroxide leaching. The alkaline intermediate water generated during the production process is usually recovered by ion exchange, acid adjustment followed by N235 extraction, or N263 extraction to recover valuable metals such as molybdenum and rhenium.

[0004] (1) Ion exchange: Large-pore anion exchange resin is used, but the alkaline solution usually needs to be acidified and adjusted to a specific pH to achieve a good adsorption capacity, and the saturated adsorption capacity of the resin is usually less than 200 mg / g, resulting in a large investment in the resin and a large amount of wastewater generated during operation.

[0005] (2) N235 (trioctyldecyl tertiary amine) extraction: N235 extractant is suitable for acidic conditions. Molybdenum is limited by the ionic form and usually has a good extraction performance for Mo at pH = 1-3. The raffinate needs to be neutralized with alkali before being discharged. This process requires the consumption of a large amount of acid and alkali, and the operating cost is relatively high.

[0006] (3) N263 extraction: N263 has two forms, namely, chlorine-type N263 (methyltrialkylammonium chloride) and carbonate-type N263 (trialkylmethylammonium carbonate). When alkaline molybdenum-containing leachate is extracted with N263, no pH adjustment process is required. Chlorine-type N263 (methyltrialkylammonium chloride) has high purity and controllable impurities, and has a good extraction effect on molybdenum. However, it needs to be fully transformed in contact with sodium carbonate before use, as shown in Chinese patent application CN101376528A. The process will produce a large amount of chlorine-containing wastewater, and it needs to be frequently regenerated in contact with sodium carbonate during operation. The process consumes a large amount of sodium carbonate, which limits the large-scale application of this process. In order to overcome the disadvantages of using chlorine-type N263, Central South University synthesized carbonate-type N263 using chlorine-type N263 as raw material. However, due to the limitations of the synthesis process and the stability of trialkylmethylammonium carbonate, the purity of the obtained carbonate-type N263 did not meet the requirements, fluctuating between 75% and 85%, and the impurities were uncontrollable. Continuous operation would cause emulsification, and the three-phase production was also significantly higher than that of chlorine-type N263.

[0007] (4) Extraction of methyl carbonate quaternary ammonium salt: In Chinese patent application CN107118104 A, methyl carbonate quaternary ammonium salt needs to be converted into a carbonic acid type-N263 extractant through saponification-solution separation-reduced pressure distillation before being used for extraction and recovery of molybdenum. The steps are complicated and the cost is high. Summary of the Invention

[0008] In view of the shortcomings of the existing technology, the present invention aims to provide a method for extracting and recovering molybdenum using a quaternary ammonium salt of methyl carbonate as an extractant in an alkaline solution, overcoming the problems of reagent consumption and chlorine-containing wastewater generation caused by the frequent transformation and regeneration of chlorine-type N263, optimizing the unsatisfactory extraction effect of carbonate-type N263, avoiding emulsification and three-phase generation, simplifying the use steps of the quaternary ammonium salt of methyl carbonate extractant, and reducing the cost of use.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A method for extracting and recovering molybdenum using a quaternary ammonium salt of methyl carbonate as an extractant in an alkaline solution comprises the following steps:

[0011] S1, directly mixing the extractant methyl carbonate quaternary ammonium salt with a phase regulator and a diluent to obtain an extracted organic phase;

[0012] S2, the extracted organic phase obtained in step S1 is directly mixed with an alkaline molybdenum-containing solution to perform molybdenum extraction;

[0013] S3. After the extraction is completed, the loaded organic phase is washed with sodium hydroxide solution and then with pure water;

[0014] S4. The loaded organic phase washed in step S3 is stripped with a mixed solution containing 2-3 mol / L NH4HCO3 and 1-2 mol / L NH3·H2O. The blank organic phase obtained after stripping is directly returned to step S2 for extraction. The stripping solution is deoiled and then evaporated to prepare an ammonia dimolybdate product.

[0015] Furthermore, the synthesis process of methyl carbonate quaternary ammonium salt in step S1 is: using dimethyl carbonate and dodecyl dimethyl tertiary amine as raw materials, anhydrous methanol as solvent, mixing the raw materials and the solvent, and reacting at a temperature of 120-150° C. for 3-7 hours to obtain methyl carbonate quaternary ammonium salt; the molar ratio of the dimethyl carbonate and dodecyl dimethyl tertiary amine is 4-8, and the mass of the solvent accounts for 5%-15% of the total mass of the raw materials and the solvent.

[0016] Furthermore, in step S1, the phase regulator is isooctyl alcohol or sec-octanol, and the diluent is kerosene.

[0017] Furthermore, in step S1, in the extracted organic phase, the volume concentration of methyl carbonate quaternary ammonium salt is 10%-40%, the volume concentration of the phase regulator is 10%, and the balance is diluent.

[0018] Furthermore, in step S2, the source of the alkaline molybdenum-containing solution includes one or more of the alkaline leaching solution produced by alkaline leaching of ammonia leaching slag produced by molybdenum smelting, the alkaline leaching solution of molybdenum roasting sand, and the alkaline leaching solution produced by the tungsten-molybdenum separation process; the alkaline molybdenum-containing solution has a pH of ≥11 and contains 0.1-120 g / L of molybdenum.

[0019] Furthermore, in the extraction of step S2, the oil-water ratio is 1 / 10-10 / 1, the number of extraction stages is 4-10, and the pH of the raffinate is ≥8.

[0020] Furthermore, in step S3, the concentration of the sodium hydroxide solution is 10-20 g / L; the oil-water ratio of washing with sodium hydroxide solution is 3 / 1-10 / 1, and the washing stages are 3-5; the oil-water ratio of washing with pure water is 5 / 1-10 / 1, and the washing stages are 2-3.

[0021] Furthermore, in the stripping of step S4, the oil-water ratio is 1 / 1-10 / 1, and the number of stripping stages is 5-10.

[0022] The beneficial effects of the present invention are:

[0023] (1) No generation of chlorine-containing wastewater: The methyl carbonate quaternary ammonium salt extractant used in the present invention does not contain chlorine. Compared with the existing chlorine-type N263 extractant, it can be put into use without undergoing transformation into a mixed solution of sodium carbonate and sodium hydroxide, thereby avoiding the generation of chlorine-containing wastewater and saving the excess sodium carbonate and sodium hydroxide reagents used for the transformation.

[0024] (2) High extraction rate and low loss of extractant: The saturated molybdenum loading of the methyl carbonate quaternary ammonium salt extractant at the same concentration is 1.1 times that of the chlorine type-N263 and 1.2-1.4 times that of the carbonate type-N263. Therefore, the amount of extractant used in the present invention is less and the loss during use is lower.

[0025] (3) Fast phase separation and no emulsification: If the alkalinity of the carbonate type-N263 is too high or the regeneration is insufficient during use, the problem of emulsification and inability to separate the phases will occur during use. However, the present invention uses the methyl carbonate quaternary ammonium salt extractant without emulsification, fast phase separation, and stronger applicability.

[0026] (4) Avoiding precipitation and three-phase generation during the extraction process: During the use of N263, a small amount of white flocculent precipitate will be produced in the raffinate, which will lead to sedimentation in the production process and easily block the pipeline. However, the methyl carbonate quaternary ammonium salt extractant used in the present invention has a higher purity, and after extraction, the raffinate is clear and bright.

[0027] (5) Simple use steps and low cost: The methyl carbonate quaternary ammonium salt extractant used in the present invention does not need to be converted into carbonic acid type-N263 through saponification-solution separation-distillation before use, and can be directly used for extracting and recovering molybdenum in an alkaline solution, which is lower in cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The chemical structure diagram of the quaternary ammonium salt of methyl carbonate prepared in Examples 1-2 of the present invention;

[0029] Figure 2 This is a flow chart for implementing the method in Examples 1-2 of the present invention;

[0030] Figure 3 Schematic diagram of extraction phase separation in Example 1-2 and Comparative Example 1-2. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0032] Example 1

[0033] Taking the ammonia leaching residue produced by molybdenum smelting as an example, after the ammonia leaching residue is subjected to normal pressure alkali leaching, the contents of Mo, P, As and Si in the alkali leaching solution are 39.9g / L, 0.26g / L, 0.28g / L and 1.33g / L respectively, and the pH is 13.56. The alkali leaching solution is used as the stock solution to extract with methyl carbonate quaternary ammonium salt. Figure 2 The specific process is as follows:

[0034] Synthesis of methyl carbonate quaternary ammonium salt: dimethyl carbonate (mass fraction 99.5%) and dodecyl dimethyl tertiary amine (mass fraction 96.8%) are used as raw materials, anhydrous methanol is used as solvent (mass fraction 99.5%), the molar ratio of dimethyl carbonate to dodecyl dimethyl tertiary amine is 5, the mass of anhydrous methanol accounts for 10% of the total mass of the raw materials and solvent, the reaction temperature is 130°C, the reaction time is 5h, and the purity of the obtained methyl carbonate quaternary ammonium salt is 95.64%; the structural formula of the methyl carbonate quaternary ammonium salt is as follows: Figure 1 shown.

[0035] Extraction: 20% methyl carbonate quaternary ammonium salt, 10% isooctyl alcohol and 70% kerosene were mixed by volume to obtain the extracted organic phase, which was directly used to extract the above alkaline leaching solution without transformation. The oil-water ratio was 2 / 1, the extraction stage was 5, the pH value of the raffinate was 10.51, and the extraction oil-water phase diagram was as follows: Figure 3 As shown in (a) (extraction and separation for 1 min).

[0036] Washing: After the extraction, the loaded organic phase was washed with 20 g / L sodium hydroxide solution, with an oil-water ratio of 5 / 1 and 3 stages, and then washed with pure water, with an oil-water ratio of 5 / 1 and 2 stages.

[0037] Stripping: The washed loaded organic phase was treated with NH4HCO3 3mol / L and NH3·H2O

[0038] 1 mol / L mixed solution was used for stripping, with an oil-water ratio of 5 / 1 and 5 stages.

[0039] The blank organic phase obtained after stripping is directly returned to the extraction without regeneration, and the stripping liquid is deoiled and then evaporated to prepare the dimolybdate ammonia product.

[0040] The extraction results of this embodiment are shown in Table 1.

[0041] Table 1

[0042]

[0043] Example 2

[0044] Taking the atmospheric pressure alkaline leaching solution of molybdenum roasted sand as an example, the contents of Mo, P, As, and Si in the alkaline leaching solution are 103.3 g / L, 0.02 g / L, 0.1 g / L, and 2.45 g / L, respectively, and the pH is 13.11. The alkaline leaching solution is used as the stock solution and methyl carbonate quaternary ammonium salt is used for extraction. The specific process is as follows:

[0045] Synthesis of extractant methyl carbonate quaternary ammonium salt: dimethyl carbonate (mass fraction 99.5%) and dodecyldimethyl tertiary amine (mass fraction 96.8%) are used as raw materials, anhydrous methanol is used as solvent (mass fraction 99.5%), the molar ratio of dimethyl carbonate to dodecyldimethyl tertiary amine is 6, methanol accounts for 10% of the total mass of the raw materials and solvent, the reaction temperature is 140°C, the reaction time is 7 hours, and the purity of the obtained methyl carbonate quaternary ammonium salt is 96.13%.

[0046] Extraction: 40% methyl carbonate quaternary ammonium salt, 10% isooctyl alcohol and 50% kerosene were mixed by volume to obtain an organic phase for extraction, which was directly used to extract the alkaline extract without transformation. The oil-water ratio was 4 / 1, the number of extraction stages was 6, and the pH of the raffinate was 9.11.

[0047] Washing: After the extraction, the loaded organic phase was washed with 20 g / L sodium hydroxide solution, with an oil-water ratio of 6 / 1 and 5 stages, and then washed with pure water, with an oil-water ratio of 6 / 1 and 2 stages.

[0048] Stripping: The washed loaded organic phase was stripped with a mixed solution containing 3 mol / L NH4HCO3 and 2 mol / L NH3·H2O, with an oil-water ratio of 5 / 1 and 5 stages.

[0049] The blank organic phase obtained after stripping is directly returned to the extraction without regeneration, and the stripping liquid is deoiled and then evaporated to prepare the dimolybdate ammonia product.

[0050] The extraction results of this embodiment are shown in Table 2.

[0051] Table 2

[0052]

[0053]

[0054] Comparative Example 1

[0055] In this comparative example, the same alkaline leaching solution treated by the method of Example 1 was used as the stock solution, and carbonic acid type-N263 was used for extraction.

[0056] Extraction: 20% carbonate type N263, 10% isooctyl alcohol and 70% kerosene were mixed to form the extraction organic phase according to the volume concentration. The oil-water ratio was 2 / 1, the extraction stage was 5, the pH value of the raffinate was 13.51, and the extraction oil-water phase diagram was as follows: Figure 3 (b) (extraction and separation 1 min) and Figure 3 As shown in (c) (extraction and separation for 30 min);

[0057] Washing: After the extraction, the loaded organic phase was washed with 20 g / L sodium hydroxide solution, with an oil-water ratio of 5 / 1 and 3 stages, and then washed with pure water, with an oil-water ratio of 5 / 1 and 2 stages;

[0058] Stripping: The washed loaded organic phase was stripped with a mixed solution containing 3 mol / L NH4HCO3 and 1 mol / L NH3·H2O, with an oil-water ratio of 5 / 1 and 5 stages.

[0059] The extraction results of this comparative example are shown in Table 3.

[0060] Table 3

[0061]

[0062] Comparative Example 2

[0063] In this comparative example, the same alkaline leaching solution treated by the method of Example 1 was used as the stock solution, and chlorine-type-N263 was used for extraction.

[0064] Transformation: 20% chloroform N263, 10% isooctyl alcohol and 70% kerosene were mixed by volume to obtain an extracted organic phase, and the extracted organic phase was fully transformed with a mixed solution containing 50 g / L sodium carbonate and 100 g / L sodium hydroxide, with an oil-water ratio of 2 / 1 and a stage number of 10.

[0065] Extraction: The alkaline extract was extracted with the transformed organic phase, with an oil-water ratio of 2 / 1, 5 extraction stages, and a raffinate pH of 13.51. The extraction oil-water phase diagram is shown in the figure below: Figure 3 As shown in (d) (extraction and separation for 30 min);

[0066] Washing: The loaded organic phase obtained by extraction was first washed with 20 g / L sodium hydroxide solution, with an oil-water ratio of 5 / 1 and 3 stages, and then washed with pure water, with an oil-water ratio of 5 / 1 and 2 stages;

[0067] Stripping: The washed loaded organic phase was stripped with a mixed solution containing 3 mol / L NH4HCO3 and 1 mol / L NH3·H2O, with an oil-water ratio of 5 / 1 and 5 stages.

[0068] The extraction results of this comparative example are shown in Table 4.

[0069] Table 4

[0070]

[0071] It can be seen from the results of Examples 1-2 and Comparative Examples 1-2 that, compared with chlorine-type N263, carbonate-type N263 does not require transformation, and the generation of chlorine-containing wastewater can be avoided, but the molybdenum extraction rate is significantly reduced, and the separation effect of molybdenum and impurities is not significantly improved. The oil-water separation rate in the extraction process is slow and easy to emulsify; compared with the two N263 extractants, Example 1-2 uses methyl carbonate quaternary ammonium salt as the extractant and can be used for extraction without transformation to carbonate-type N263, which simplifies the use steps and avoids the generation of chlorine-containing wastewater. At the same time, the impurity removal effect is better, the Mo extraction rate is higher, the oil-water separation rate is fast, the effect is good, no emulsification occurs during the whole process, and it has good applicability.

[0072] Those skilled in the art can make various corresponding changes and modifications based on the above technical solutions and concepts, and all of these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims

1. A method for extracting and recovering molybdenum using a quaternary ammonium salt of methyl carbonate as an extractant in an alkaline solution, characterized in that: The steps include: S1, directly mixing the extractant methyl carbonate quaternary ammonium salt with a phase regulator and a diluent to obtain an extracted organic phase; S2, the extracted organic phase obtained in step S1 is directly mixed with an alkaline molybdenum-containing solution to perform molybdenum extraction; S3. After the extraction is completed, the loaded organic phase is washed with sodium hydroxide solution and then with pure water; S4. The loaded organic phase washed in step S3 is stripped with a mixed solution containing 2-3 mol / L NH4HCO3 and 1-2 mol / L NH3·H2O. The blank organic phase obtained after stripping is directly returned to step S2 for extraction. The stripping solution is deoiled and then evaporated to prepare an ammonia dimolybdate product.

2. The method according to claim 1, characterized in that The synthesis process of the methyl carbonate quaternary ammonium salt in step S1 is as follows: dimethyl carbonate and dodecyl dimethyl tertiary amine are used as raw materials, anhydrous methanol is used as solvent, the raw materials and the solvent are mixed, and the reaction is carried out at a temperature of 120-150° C. for 3-7 hours to obtain the methyl carbonate quaternary ammonium salt; the molar ratio of the dimethyl carbonate to the dodecyl dimethyl tertiary amine is 4-8, and the mass of the solvent accounts for 5%-15% of the total mass of the raw materials and the solvent.

3. The method according to claim 1, characterized in that In step S1, the phase regulator is isooctyl alcohol or sec-octanol, and the diluent is kerosene.

4. The method according to claim 3, characterized in that In step S1, in the extracted organic phase, the volume concentration of methyl carbonate quaternary ammonium salt is 10%-40%, the volume concentration of the phase regulator is 10%, and the balance is diluent.

5. The method according to claim 1, wherein In step S2, the source of the alkaline molybdenum-containing solution includes one or more of the alkaline leachate produced by alkaline leaching of ammonia leached slag produced by molybdenum smelting, the alkaline leachate of molybdenum roasted sand, and the alkaline leachate produced by the tungsten-molybdenum separation process; the alkaline molybdenum-containing solution has a pH of ≥11 and contains 0.1-120 g / L of molybdenum.

6. The method according to claim 1, characterized in that In the extraction of step S2, the oil-water ratio is 1 / 10-10 / 1, the number of extraction stages is 4-10, and the pH of the raffinate is ≥8.

7. The method according to claim 1, characterized in that In step S3, the concentration of the sodium hydroxide solution is 10-20 g / L; the oil-water ratio of washing with sodium hydroxide solution is 3 / 1-10 / 1, and the washing stages are 3-5; the oil-water ratio of washing with pure water is 5 / 1-10 / 1, and the washing stages are 2-3.

8. The method according to claim 1, characterized in that In the stripping of step S4, the oil-water ratio is 1 / 1-10 / 1, and the number of stripping stages is 5-10.

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