Method for eliminating molybdenum reverse extraction three phases in classical ammonia leaching process and improving molybdenum and rhenium recovery rate

Abstract

The invention discloses a method for eliminating molybdenum reverse extraction three phases in a classical ammonia leaching process and improving the molybdenum and rhenium recovery rate, which organically couples ammonia leaching residue and presoaking liquid treatment processes by adopting the processes of twice countercurrent alkaline leaching of ammonia leaching residues, extraction after neutralization of presoaking liquid and return alkaline leaching of neutralized residues, so that the Mo loss in the ammonia leaching residues can be reduced, and the molybdenum and rhenium recovery rate can be improved. The alkaline leaching liquid is efficiently treated, three phases generated by reverse extraction are eliminated, and the loss rate of molybdenum and rhenium in the liquid is reduced.

Description

Technical Field

[0001] This invention relates to the field of molybdenum smelting technology, specifically to a method for eliminating the three phases of molybdenum back-extraction in the classic ammonia leaching process and improving the recovery rate of molybdenum and rhenium. Background Technology

[0002] The molybdenum concentrate produced from copper-molybdenum separation contains a certain amount of Re and high levels of impurities such as Cu, K, Na, and Fe. This mine employs the "classic ammonia leaching process" to prepare ammonium molybdate. This typically involves oxidative roasting of the molybdenum concentrate to produce qualified molybdenum roasted sand. The roasted sand is then pre-leached with nitric acid to remove Cu, K, and Na, followed by multi-stage ammonia leaching, purification, and acid precipitation to prepare ammonium tetramolybdate. The pre-leaching liquor is then extracted to recover molybdenum and rhenium, and the raffinate is sulfided and precipitated to recover copper. However, in actual production, the extraction-back-extraction process of the pre-leaching liquor usually generates a large amount of three-phase material, resulting in low molybdenum and rhenium extraction rates, significant organic consumption and molybdenum and rhenium loss, and operational inefficiencies. Furthermore, the ammonia leaching residue has a high molybdenum content, leading to a low pricing factor for direct sale and hindering maximum profitability.

[0003] Regarding the three-phase formation generated during back-extraction, Zhang Yongming et al. (Zhang Yongming, Niu Yuqing, Zhi Meifeng, et al. Analysis of the causes and elimination of interface contaminants in molybdenum back-extraction [J]. Uranium Mining and Metallurgy, 2020, 39(2):87-91) slightly reduced the generation of the three-phase formation through improvements in the back-extraction process and equipment, but the three-phase formation was not completely eliminated. Chinese patent application CN114369731A discloses a method for reducing the three-phase formation during molybdenum back-extraction, proposing to add polyether to the leachate for deep desiliconization and to replace the back-extraction agent with a mixed solution of sodium hydroxide and hydrogen peroxide, which can reduce the three-phase formation by more than 95%. However, this method is costly and difficult to widely apply. Chinese patent application CN119571059A discloses a method for suppressing the generation of the three-phase formation during the molybdenum-rhenium extraction process, proposing to add sulfuric acid to the extraction solution and carry out extraction under high acidity, which can reduce the three-phase formation and suppress the extraction of molybdenum, thereby improving the separation effect of rhenium and molybdenum. However, this method will lead to a significant increase in the cost of subsequent wastewater neutralization, and molybdenum cannot be effectively recovered.

[0004] For molybdenum recovery from ammonia leaching residue, pressure leaching can be used, and the leachate can then be ion exchanged to recover molybdenum. However, this process is lengthy and involves a large volume of water. Alternatively, pressure alkaline leaching solution can be used to recover molybdenum through acid precipitation, and the precipitated solution can then be used for extraction. However, due to the high silicon content in the alkaline leaching solution, the formation of the three phases in the extraction system will be aggravated. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide a method for eliminating the three-phase back-extraction of molybdenum and improving the recovery rate of molybdenum and rhenium in the classic ammonia leaching process. This method integrates the ammonia leaching residue and pre-leaching solution treatment processes by performing two-stage countercurrent alkaline leaching for deep molybdenum extraction, neutralization and extraction of the pre-leaching solution, and return of the neutralized residue to alkaline leaching for molybdenum and rhenium recovery. This approach completely eliminates the three-phase process, improves the extraction rate of molybdenum and rhenium, reduces the molybdenum content in the ammonia leaching residue, increases the overall recovery rate of molybdenum and rhenium, shortens the process flow, and achieves green and efficient molybdenum smelting.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for eliminating the three-phase back-extraction of molybdenum and improving the recovery rate of molybdenum and rhenium in the classic ammonia leaching process includes the following steps: S1. The molybdenum concentrate is oxidized and roasted to produce molybdenum roasted sand. The molybdenum roasted sand is then pre-leached with nitric acid solution. The pH of the pre-leaching endpoint is controlled to be 1. The pre-leached residue enters step S2 for ammonia leaching, and the pre-leaching solution enters step S6. S2, First ammonia leaching: The pre-leaching residue obtained in step S1 is slurried with pure water, and then ammonia water is added for a first ammonia leaching under normal pressure. The pH of the final step of the first ammonia leaching is controlled to be 8-9, and a first ammonia leaching residue and a first ammonia leaching solution are obtained. After the first ammonia leaching solution is purified by adding ammonium sulfide, the purified solution is acid-precipitated to prepare ammonium molybdate product. Nitric acid is added to the acid precipitation solution and it participates in the pre-leaching in step S1. S3, First alkaline leaching: The first ammonia leaching residue obtained in step S2 is subjected to a first countercurrent alkaline leaching under normal pressure. During the initial operation, sodium hydroxide is added to the first alkaline leaching of the first ammonia leaching residue, and the final pH is controlled at 10-11. In subsequent operations, the second alkaline leaching solution from step S4 is used for the first alkaline leaching, and the final pH is controlled at <11. After the first alkaline leaching, the first alkaline leaching residue and the first alkaline leaching solution are obtained. The first alkaline leaching residue enters step S4 for a second countercurrent alkaline leaching, and the first alkaline leaching solution enters step S5 for molybdenum precipitation. S4. Secondary alkaline leaching: After adjusting the slurry of the primary alkaline leaching residue obtained in step S3, alkali is added, and a second alkaline leaching is carried out under normal pressure, with the endpoint pH controlled at 13-13.5, to obtain secondary alkaline leaching residue and secondary alkaline leaching liquor. The secondary alkaline leaching residue is washed and sold externally, the wash water of the secondary alkaline leaching residue is reused for adjusting the slurry of the primary alkaline leaching residue, and the secondary alkaline leaching liquor is returned to step S3 to participate in the first alkaline leaching. S5, Molybdenum precipitation in primary alkaline leaching solution: Nitric acid is added to the primary alkaline leaching solution to precipitate molybdenum. The pH of the reaction endpoint is controlled to be ≤1 to obtain molybdenum acid precipitate and molybdenum precipitation solution. The molybdenum acid precipitate is returned to step S2 for primary ammonia leaching, and the molybdenum precipitation solution is entered into step S6 for neutralization. S6, Neutralization: The pre-leaching solution and the molybdenum precipitation solution are neutralized by adjusting the pH with sodium hydroxide to obtain neutralization residue and neutralized solution. The neutralization residue is returned to step S4 for alkaline leaching to recover molybdenum and rhenium, and the neutralized solution is entered into step S7 for extraction. S7. Extraction: The neutralized liquid is extracted using a system of N235, isooctanol and kerosene. The raffinate is then treated with copper sulfide precipitation and then sent to wastewater treatment. S8. Back-extraction: After washing, the organic-rich phase produced by extraction in step S7 is back-extracted with sodium hydroxide. The pH at the end of the back-extraction is controlled to be greater than 13. The back-extraction solution is then used for rhenium-molybdenum separation.

[0007] Furthermore, in step S1, the liquid-to-solid ratio of nitric acid solution to molybdenum calcined sand is 3-6:1 (mL / g), the pre-soaking temperature is 85-95℃, and the reaction time is 1-3h.

[0008] Further, in step S2, the liquid-to-solid ratio of pure water to pre-impregnated residue is 3-5:1 (mL / g); the temperature of the first ammonia leaching is 50-60℃, and the reaction time is 1-2 hours; the mass concentration of the ammonia sulfide agent used for purification is 10%, the amount of ammonia sulfide added is 1.5 times the total molar number of impurity ions, the purification temperature is 50℃, and the reaction time is 1 hour.

[0009] Furthermore, in step S3, during the first alkaline leaching, the liquid-to-solid ratio (mL / g) is 3-5:1, the temperature is 85-95℃, and the reaction time is 1-2 hours.

[0010] Further, in step S4, the liquid-to-solid ratio of the first alkaline leaching residue slurry is 3-5:1 (mL / g), and the added alkali includes sodium hydroxide and sodium carbonate, with a mass ratio of sodium oxide to sodium carbonate of 4-7:1-2; the temperature of the second alkaline leaching is 90-95℃, and the reaction time is 2-3 hours.

[0011] Furthermore, in step S5, the temperature for molybdenum precipitation is 80-90℃, and the reaction time is 1-2 hours.

[0012] Furthermore, in step S6, the pH of the neutralization reaction is 5-6, and the reaction time is 0.5-1 h.

[0013] Further, in step S7, the volume concentration of N235 is 5-10%, the volume concentration of isooctyl alcohol is 10%, and the remainder is kerosene; the extraction ratio is 1 / 2-1 / 5, and the number of extraction stages is 3-5.

[0014] Furthermore, in step S8, the back-extraction ratio is 2 / 1 to 5 / 1.

[0015] The beneficial effects of this invention are as follows: This invention organically couples the treatment processes of ammonia leaching residue and pre-leaching solution by employing a process of two countercurrent alkaline leachings of ammonia leaching residue, extraction after neutralization of the pre-leaching solution, and return of the neutralized residue to alkaline leaching, thereby achieving the following effects: (1) Reduce Mo loss in ammonia leaching residue: The Mo content in the residue can be reduced to below 1% by only three atmospheric pressure leaching processes (one ammonia leaching and two alkaline leaching processes), without the need for multiple leaching processes or the addition of high-pressure leaching equipment, thus reducing the generation of ammonia waste gas; (2) High-efficiency treatment of alkaline leaching solution: Si in the alkaline leaching solution is effectively controlled, so only nitric acid precipitation is needed to recover molybdenum. The Mo concentration in the solution after molybdenum precipitation is <100mg / L, and there is no need to process it through a complex ion exchange process. (3) Elimination of three phases: The pre-soaking solution is neutralized and impurities are removed before entering the extraction. The back-extraction uses sodium hydroxide to control the endpoint pH > 13, which can completely eliminate the three phases generated by back-extraction and make the extraction section run smoothly. (4) Reduce the loss rate of molybdenum and rhenium in the liquid: The pre-leaching liquid neutralizes and precipitates copper and iron, and precipitates some molybdenum and rhenium. After extraction, the Mo in the raffinate is less than 100 mg / L and Re is less than 2 mg / L, which reduces the loss rate of molybdenum and rhenium in the liquid. The neutralized residue is returned to the second alkaline leaching to recover molybdenum and rhenium. The residue from the second alkaline leaching is sold as copper concentrate. (5) Simple and efficient process: The whole process does not require additional special equipment or special reagents for silicon removal and elimination of three phases. The extraction of three phases and the improvement of the total recovery rate of molybdenum and rhenium can be achieved simply by integrating the new process and controlling the parameters. The process is simple and highly practical. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the implementation of the method in Embodiment 1 of the present invention; Figure 2 This is a comparison diagram of the raffinate obtained in Example 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings. It should be noted that this embodiment is based on the present technical solution and provides detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to this embodiment.

[0018] Example 1

[0019] This embodiment provides a method for eliminating the three-phase back-extraction of molybdenum and improving the recovery rate of molybdenum and rhenium in the classic ammonia leaching process, such as... Figure 1 As shown, it includes the following steps: (1) Pre-leaching: Molybdenum concentrate is oxidized and roasted to produce molybdenum roasted sand. The acid precipitation solution obtained in step (2) is replenished with nitric acid, and molybdenum roasted sand is added at a liquid-to-solid ratio of mL / g = 4:1. The mass contents of Mo, Cu and S in the molybdenum roasted sand are 46.21%, 3.86% and 0.09%, respectively. The pH of the pre-leaching endpoint is controlled at 1, the temperature at 90℃ and the reaction time at 2h. The pre-leaching residue is then entered into step (2) for ammonia leaching, and the pre-leaching solution is then entered into step (6). (2) First ammonia leaching: The above pre-leached residue was slurried with pure water at a liquid-to-solid ratio of mL / g = 4:1. Ammonia water was added and ammonia leaching was carried out under normal pressure. The pH of the first ammonia leaching endpoint was controlled at 8.5, the temperature at 60℃, and the reaction time was 2h. A 10% ammonium sulfide solution (the mass of ammonium sulfide is 1.5 times the total molar number of impurity ions) was added to the generated first ammonia leaching solution for purification. The purification temperature was 50℃ and the reaction time was 1h. After purification, the purified solution was acid-precipitated to prepare ammonium molybdate product. The acid-precipitated solution was returned to participate in the pre-leaching. The first ammonia leaching residue entered step (3) for the first alkaline leaching. (3) First alkaline leaching: Add the second alkaline leaching solution from step (4) to the above first ammonia leaching residue at a liquid-to-solid ratio of mL / g=4:1 and carry out the first alkaline leaching under normal pressure, temperature 90℃, reaction time 1h, endpoint pH=10.67, the resulting first alkaline leaching residue enters step (4) for the second alkaline leaching, and the first alkaline leaching solution enters step (5) for molybdenum precipitation. (4) Secondary alkaline leaching: The first alkaline leaching residue is added to the washing water of the second alkaline leaching residue at a liquid-to-solid ratio of mL / g=4:1. 60g / L sodium hydroxide and 20g / L sodium carbonate are added. The second alkaline leaching is carried out under normal pressure at a temperature of 95℃ for 2 hours. The final pH is 13.46. The resulting second alkaline leaching residue is washed and sold. The second alkaline leaching solution is returned to step (3) to participate in the first alkaline leaching. (5) Precipitation of molybdenum in the first alkaline leaching solution: Nitric acid is added to the first alkaline leaching solution to precipitate molybdenum at a temperature of 90℃ for 2 hours. The pH of the reaction endpoint is controlled to be 1. The resulting molybdenum acid precipitate is returned to step (2) for ammonia leaching. The precipitated molybdenum solution is then entered into step (6) for neutralization. (6) Neutralization of pre-leaching solution: The pH of the pre-leaching solution and the molybdenum precipitation solution is adjusted to 5 with sodium hydroxide and reacted for 1 hour. The resulting neutralization residue is returned to step (4) to participate in alkaline leaching to recover molybdenum and rhenium. The neutralized solution enters step (7) for extraction. (7) Extraction: The neutralized liquid was extracted using a system of "N235 + isooctanol + kerosene". The volume concentration of N235 was 5%, the volume concentration of isooctanol was 10%, and the remainder was kerosene. The extraction ratio was 1 / 3, and the number of stages was 4. The raffinate was then treated with copper sulfide precipitation before being sent to wastewater treatment. (8) Back-extraction: After washing, the organic-rich phase produced in step (7) is back-extracted using sodium hydroxide. The back-extraction ratio is 3 / 1, and the pH at the back-extraction endpoint is controlled at 13.10. The resulting back-extraction solution is then subjected to rhenium-molybdenum separation. The obtained back-extraction solution is as follows: Figure 2 As shown in (a).

[0020] The results obtained in this embodiment are shown in Tables 1 and 2 below.

[0021] Table 1 category Mo (%) Re(g / t) Cu (%) Fe (%) Secondary alkaline leaching residue 0.91 1.03 0.13 9.64 neutral slag 3.65 236.12 26.89 12.65 After the neutralized residue is added to the secondary alkaline leaching 0.06 0.56 43.29 19.87 Table 2 category Mo (g / L) Re (mg / L) Si (mg / L) Alkali leaching solution 41.36 89.63 56.37 After one alkaline leaching solution precipitation of Mo 0.068 86.94 55.37 Extraction solution (a mixture of pre-soaking solution and post-molybdenum precipitation solution) 3.21 189.73 103.94 Neutralized liquid 0.39 113.43 46.36 residual liquid 0.064 1.67 35.62 Comparative Example 1 Taking molybdenum calcined sand with Mo, Cu and S contents of 46.21%, 3.86% and 0.09% as an example, the classic ammonia leaching process is adopted, in which the ammonia leaching adopts a 4-stage countercurrent ammonia leaching process.

[0022] (1) Pre-soaking: Take the acid precipitation liquid from step (2) and add nitric acid. Add molybdenum calcined sand according to the liquid-solid ratio mg / L=4:1. Control the endpoint pH=1, temperature 90℃, reaction time 2h. The resulting pre-soaking residue enters the first ammonia leaching, and the pre-soaking liquid enters the extraction. (2) Primary ammonia leaching: The pre-leached residue was slurried with all the secondary ammonia leaching solution from step (2), and ammonia water was used for the first ammonia leaching. The final pH was controlled at 8.5, the temperature at 60℃, and the reaction was carried out for 2 hours. The resulting primary ammonia leaching solution was purified by adding a 10% ammonium sulfide solution (the mass of ammonium sulfide was 1.5 times the total molar number of impurity ions) at a purification temperature of 50℃ and a reaction time of 1 hour. After purification, ammonium molybdate was prepared by acid precipitation. The acid precipitation solution was returned to the pre-leaching solution, and the primary ammonia leaching residue was used for secondary ammonia leaching. (3) Secondary ammonia leaching: The above primary ammonia leaching residue is slurried with all the tertiary ammonia leaching liquid from step (4), and ammonia water is added for secondary ammonia leaching. The endpoint pH is controlled at 9, the temperature is 65℃, and the reaction time is 2h. All the secondary ammonia leaching liquid is returned to the primary ammonia leaching, and the secondary ammonia leaching residue is subjected to a third ammonia leaching. (4) Three-time ammonia leaching: The above-mentioned secondary ammonia leaching residue is slurried with all the fourth ammonia leaching liquid from step (4), and ammonia water is added for the third ammonia leaching. The final pH is controlled at 9.5, the temperature is 70℃, and the reaction time is 2h. All the third ammonia leaching liquid is returned to the second ammonia leaching, and the third ammonia leaching residue is subjected to the fourth ammonia leaching. (5) Four ammonia leachings: The residue from the three ammonia leachings above were slurried with pure water and the wash water from the four ammonia leachings at a liquid-to-solid ratio of 15:1. Ammonia water was added for the fourth ammonia leaching. The final pH was controlled at 10, the temperature at 75°C, and the reaction time was 2 hours. All the liquid from the four ammonia leachings was returned to the third ammonia leaching. The residue from the four ammonia leachings was washed and sold. The wash water was reserved for the next fourth ammonia leaching. (6) Extraction: The pre-impregnation solution was extracted using a system of "N235 + isooctyl alcohol + kerosene". The concentration of N235 was 30%, the concentration of isooctyl alcohol was 10%, the extraction ratio was 1 / 3, and the number of stages was 4. (7) Back-extraction: After washing, the resulting organic-rich phase is back-extracted with ammonia water. The pH at the back-extraction endpoint is controlled at 9.5, and the back-extraction ratio is 3:1. The resulting back-extraction solution is as follows: Figure 2 As shown in (b).

[0023] The results obtained from this comparative example are shown in Tables 3 and 4.

[0024] Table 3 category Mo (%) Re(g / t) Cu (%) Fe (%) Four-time ammonia leaching residue 4.62 2.13 0.11 8.93 Table 4 category Mo (g / L) Re (mg / L) Si (mg / L) Extraction liquid 3.96 167.38 106.73 residual liquid 1.56 43.56 32.34 Comparative Example 2 The molybdenum calcined sand in this comparative example contains 46.21% Mo, 3.86% Cu, and 0.09% S by mass, respectively. The difference from Example 1 is that the two countercurrent alkaline leachings of the ammonia leaching residue are replaced with two cocurrent leachings; otherwise, they are the same as in Example 1. Details are as follows: First alkaline leaching: Take 50% of the first ammonia leaching residue, add washing water and fresh water at a liquid-to-solid ratio of 8:1, add 30g / L NaOH and 20g / L Na2CO3, temperature 95℃, reaction time 2h, endpoint pH=13.21, the resulting first alkaline leaching residue is washed and sold, and the first alkaline leaching solution enters the second alkaline leaching. Secondary alkaline leaching: 50% of the primary ammonia leaching residue is added to the primary alkaline leaching solution at a liquid-to-solid ratio of 8:1. 15 g / L sodium hydroxide and 10 g / L sodium carbonate are also added. The temperature is 95℃, the reaction time is 2 hours, and the final pH is 13.16. The resulting secondary alkaline leaching residue is washed and sold externally, while the secondary alkaline leaching solution enters the molybdenum precipitation process.

[0025] The results are shown in Tables 5 and 6.

[0026] Table 5 category Mo (%) Re(g / t) Cu (%) Fe (%) Alkali leaching residue 1.12 1.56 0.11 9.54 Secondary alkaline leaching residue 1..01 1.25 0.13 9.61 neutral slag 12.36 243.98 19.68 8.63 After alkali leaching of neutralized residue 0.10 1.36 40.51 18.69 Table 6 category Mo (g / L) Re (mg / L) Si (mg / L) Secondary alkaline leaching solution 39.64 89.63 1640.53 After the second alkaline leaching solution precipitates Mo 38.59 84.98 158.61 Extraction liquid 21.56 168.34 865.21 Neutralized liquid 10.34 123.68 264.38 residual liquid 3.06 56.91 195.62 As shown in Example 1, the classic ammonia leaching process employs a two-stage countercurrent alkaline leaching of the ammonia leaching residue and extraction after neutralization of the pre-leaching solution, with the neutralized residue being returned to alkaline leaching. The Mo and Re contents in the secondary alkaline leaching residue obtained in Example 1 are 0.91% and 1.03 g / t, respectively. After molybdenum precipitation with nitric acid in the first countercurrent alkaline leaching solution, the Mo concentration is 68 mg / L, indicating high molybdenum precipitation efficiency. After neutralization and extraction, the extraction solution (i.e., the mixture of the pre-leaching solution and the molybdenum-precipitated solution) yields 64 mg / L and 1.67 mg / L of Mo and Re in the raffinate, respectively. Figure 2 As shown in (a), there was no obvious precipitate at the bottom of the separatory funnel, indicating that no three phases were generated during the back-extraction process.

[0027] Comparative Example 1 used the classic ammonia leaching process. The Mo and Re contents in the residue from the four ammonia leaching processes were 4.62% and 2.13%, respectively, while the Mo and Re concentrations in the raffinate were 1.56 g / L and 43.56 mg / L, respectively. Significant losses of molybdenum and rhenium were observed. Figure 2 As shown in (b), there is obvious precipitate at the bottom of the separatory funnel, indicating severe three-phase reaction during the back-extraction process.

[0028] In Comparative Example 2, the two countercurrent alkaline leaching processes were changed to cocurrent alkaline leaching. The alkaline leaching solution was treated with nitric acid to precipitate Mo, and almost no precipitate was produced. Mo in the alkaline leaching solution could not be effectively recovered, which worsened the subsequent extraction and resulted in the concentrations of Mo and Re in the raffinate as high as 3.06 g / L and 56.91 mg / L, respectively.

[0029] For those skilled in the art, various corresponding changes and modifications can be made based on the above technical solutions and concepts, and all such changes and modifications should be included within the protection scope of the claims of this invention.

Claims

1. A method for eliminating the three-phase back-extraction of molybdenum and improving the recovery rate of molybdenum and rhenium in the classic ammonia leaching process, characterized in that, Includes the following steps: S1. The molybdenum concentrate is oxidized and roasted to produce molybdenum roasted sand. The molybdenum roasted sand is then pre-leached with nitric acid solution. The pH of the pre-leaching endpoint is controlled to be 1. The pre-leached residue enters step S2 for ammonia leaching, and the pre-leaching solution enters step S6. S2, First ammonia leaching: The pre-leaching residue obtained in step S1 is slurried with pure water, and then ammonia water is added for a first ammonia leaching under normal pressure. The pH of the final step of the first ammonia leaching is controlled to be 8-9, and a first ammonia leaching residue and a first ammonia leaching solution are obtained. After the first ammonia leaching solution is purified by adding ammonium sulfide, the purified solution is acid-precipitated to prepare ammonium molybdate product. Nitric acid is added to the acid precipitation solution and it participates in the pre-leaching in step S1. S3, First alkaline leaching: The first ammonia leaching residue obtained in step S2 is subjected to a first countercurrent alkaline leaching under normal pressure. During the initial operation, sodium hydroxide is added to the first alkaline leaching of the first ammonia leaching residue, and the final pH is controlled at 10-11. In subsequent operations, the second alkaline leaching solution from step S4 is used for the first alkaline leaching, and the final pH is controlled at <11. After the first alkaline leaching, the first alkaline leaching residue and the first alkaline leaching solution are obtained. The first alkaline leaching residue enters step S4 for a second countercurrent alkaline leaching, and the first alkaline leaching solution enters step S5 for molybdenum precipitation. S4. Secondary alkaline leaching: After adjusting the slurry of the primary alkaline leaching residue obtained in step S3, alkali is added, and a second alkaline leaching is carried out under normal pressure, with the endpoint pH controlled at 13-13.5, to obtain secondary alkaline leaching residue and secondary alkaline leaching liquor. The secondary alkaline leaching residue is washed and sold externally, the wash water of the secondary alkaline leaching residue is reused for adjusting the slurry of the primary alkaline leaching residue, and the secondary alkaline leaching liquor is returned to step S3 to participate in the first alkaline leaching. S5, Molybdenum precipitation in primary alkaline leaching solution: Nitric acid is added to the primary alkaline leaching solution to precipitate molybdenum. The pH of the reaction endpoint is controlled to be ≤1 to obtain molybdenum acid precipitate and molybdenum precipitation solution. The molybdenum acid precipitate is returned to step S2 for primary ammonia leaching, and the molybdenum precipitation solution is entered into step S6 for neutralization. S6, Neutralization: The pre-leaching solution and the molybdenum precipitation solution are neutralized by adjusting the pH with sodium hydroxide to obtain neutralization residue and neutralized solution. The neutralization residue is returned to step S4 for alkaline leaching to recover molybdenum and rhenium, and the neutralized solution is entered into step S7 for extraction. S7. Extraction: The neutralized liquid is extracted using a system of N235, isooctanol and kerosene. The raffinate is then treated with copper sulfide precipitation and then sent to wastewater treatment. S8. Back-extraction: After washing, the organic-rich phase produced by extraction in step S7 is back-extracted with sodium hydroxide. The pH at the end of the back-extraction is controlled to be greater than 13. The back-extraction solution is then used for rhenium-molybdenum separation.

2. The method according to claim 1, characterized in that, In step S1, the liquid-to-solid ratio of nitric acid solution to molybdenum calcined sand is 3-6:1 (mL / g), the pre-soaking temperature is 85-95℃, and the reaction time is 1-3h.

3. The method according to claim 1, characterized in that, In step S2, the liquid-to-solid ratio of pure water to pre-impregnated residue is 3-5:1 (mL / g); the temperature of the first ammonia leaching is 50-60℃, and the reaction time is 1-2 hours; the mass concentration of the ammonia sulfide agent used for purification is 10%, the amount of ammonia sulfide added is 1.5 times the total molar number of impurity ions, the purification temperature is 50℃, and the reaction time is 1 hour.

4. The method according to claim 1, characterized in that, In step S3, during the first alkaline leaching, the liquid-to-solid ratio (mL / g) is 3-5:1, the temperature is 85-95℃, and the reaction time is 1-2 hours.

5. The method according to claim 1, characterized in that, In step S4, the liquid-to-solid ratio of the first alkaline leaching residue slurry is 3-5:1 (mL / g), and the added alkali includes sodium hydroxide and sodium carbonate, with a mass ratio of sodium oxide to sodium carbonate of 4-7:1-2. The temperature of the second alkaline leaching is 90-95℃, and the reaction time is 2-3 hours.

6. The method according to claim 1, characterized in that, In step S5, the temperature for molybdenum precipitation is 80-90℃, and the reaction time is 1-2 hours.

7. The method according to claim 1, characterized in that, In step S6, the pH of the neutralization reaction is 5-6, and the reaction time is 0.5-1 h.

8. The method according to claim 1, characterized in that, In step S7, the volume concentration of N235 is 5-10%, the volume concentration of isooctanol is 10%, and the remainder is kerosene; the extraction ratio is 1 / 2-1 / 5, and the number of extraction stages is 3-5.

9. The method according to claim 1, characterized in that, In step S8, the back-extraction ratio is 2 / 1 to 5 / 1.

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