Method for improving molybdenum and rhenium recovery rate in classical ammonia leaching process

Abstract

Aiming at the problem of loss of molybdenum and rhenium in tailings and waste liquid of the classic ammonia leaching process, the method comprises the following steps of: performing countercurrent alkaline leaching on ammonia leaching residues twice, adsorbing and recovering molybdenum by using a primary alkaline leaching solution and an acid precipitation solution, precipitating molybdenum in a desorption solution, supplementing water for diluting, and returning to pre-leaching. The Mo content in the slag can be reduced, the ammonium concentration in the preimpregnation process can be controlled, the influence of ammonium on subsequent extraction is eliminated, the extraction rate of Mo and Re in the preimpregnation liquid is increased, the classic ammonia leaching process, the classic alkaline leaching process, the classic adsorption process and the classic extraction process are organically integrated, and the total recovery rate of Mo and Re in the smelting process is increased.

Description

Technical Field

[0001] This invention relates to the field of molybdenum smelting, and more specifically to a method for improving the recovery rate of molybdenum and rhenium in the classic ammonia leaching process. Background Technology

[0002] The smelting of molybdenum concentrate is mainly divided into pyrometallurgical-hydrometallurgical combined processes and all-hydrometallurgical processes, among which "oxidative roasting-ammonia leaching" is the most widely used process (classic ammonia leaching process). The "oxidative roasting-ammonia leaching" process typically involves oxidative roasting to desulfurize, pre-leaching to remove impurities, multiple ammonia leachings, purification to remove heavy metals, and acid precipitation to produce ammonium tetramolybdate. The acid precipitation solution is returned to the pre-leaching solution, and molybdenum, rhenium, and copper are recovered from the pre-leaching solution. The ammonia leaching residue produced by this process has a Mo content as high as 7%-20%, and the raffinate has a Mo concentration >1g / L and a Re concentration >20mg / L, indicating significant losses of Mo and Re.

[0003] There are several ways to treat ammonia leaching residue: (1) Repeated countercurrent ammonia leaching to reduce the Mo content in the ammonia leaching residue to less than 2%, but this method will generate a large amount of ammonia waste gas and the cost is high; (2) High molybdenum ammonia leaching residue is used for ferromolybdenum smelting, but this process requires high purity of raw materials, large equipment investment, and high energy consumption; (3) Molybdenum is recovered by pressure leaching, but the pressure equipment used in this process has a high investment and operation risk factor; (4) Molybdenum is recovered by atmospheric pressure alkaline leaching, but the silicon leaching in atmospheric pressure leaching is usually uncontrollable, and an additional silicon removal process is required to form a colloidal precipitate containing silicon, which leads to serious loss of molybdenum due to adsorption and entrainment, and liquid-solid separation is difficult.

[0004] The resulting pre-impregnation solution is usually extracted to recover rhenium and molybdenum. However, actual production and research have found that although ammonium ions in the acid precipitation solution can inhibit the leaching of Mo during the pre-impregnation and impurity removal process and reduce the concentration of Mo in the pre-impregnation solution, excessively high ammonium ion concentrations will also worsen the subsequent extraction, resulting in an extraction rate of Mo <30% and an extraction rate of Re <50%.

[0005] Regarding the disposal of ammonia leaching residue, Chinese patent application CN101660045A discloses a method for extracting molybdenum from ammonia leaching residue by decomposing sodium hypochlorite, which can reduce the molybdenum content in the tailings to below 1%, but requires equipment with high corrosion resistance. Chinese patent application CN106241876A proposes a process of acid treatment-ammonia leaching-impurity removal-neutralization crystallization to prepare ammonium molybdate from tertiary ammonia leaching residue. The impurity removal process uses a series of reagents such as ammonium carbonate, ammonium sulfide, hydrogen peroxide, and magnesium nitrate, but this process leads to further molybdenum loss and is complex. Chinese patent application CN104152707A proposes a scheme for smelting ferromolybdenum from ammonia leaching residue, which can reduce the molybdenum content in the residue to below 0.5%, but the pyrometallurgical process is highly polluting, energy-intensive, and requires significant investment. However, research on the rhenium-molybdenum extraction rate of acidic pre-leaching solutions with high ammonia content is scarce, resulting in high molybdenum and rhenium losses in the tailings and tailings of the current classic ammonia leaching process, and low overall metal recovery rate. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention aims to provide a method for improving the recovery rate of molybdenum and rhenium in the classic ammonia leaching process.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for improving the recovery rate of molybdenum and rhenium in the classic ammonia leaching process includes the following steps: S1. After desulfurization by oxidative roasting, the molybdenum concentrate is pre-leached with nitric acid solution, and the final pH is controlled to be 0.95-1.12 to obtain pre-leached residue and pre-leaching solution. The pre-leaching solution is transferred to step S7 for further processing. S2, Primary ammonia leaching: After mixing the pre-leaching residue and pure water, ammonia leaching is carried out under normal pressure using ammonia water or liquid ammonia, controlling the endpoint pH=8-9, to produce primary ammonia leaching solution and primary ammonia leaching residue; after purifying the primary ammonia leaching solution with ammonium sulfide, the purified solution is acid-precipitated to prepare ammonium molybdate product, and the acid precipitation solution produced by acid precipitation is transferred to step S5 for treatment. S3. First alkaline leaching: The first ammonia leaching residue obtained in step S2 is subjected to a first 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 to perform a first alkaline leaching of the first ammonia leaching residue, and the final pH is controlled at 10-11. The first alkaline leaching yields first alkaline leaching residue and first alkaline leaching solution. The first alkaline leaching residue is processed in step S4, and the first alkaline leaching solution is processed in step S5. S4. Secondary alkaline leaching: The primary alkaline leaching residue obtained in step S3 is subjected to a second alkaline leaching under normal pressure, with the endpoint pH controlled at 13-13.5, to obtain secondary alkaline leaching residue and secondary alkaline leaching solution. The secondary alkaline leaching residue is washed and sold externally, while the secondary alkaline leaching solution is returned to step S3 to participate in the first alkaline leaching. S5. Adsorption of primary alkaline leaching solution and acid precipitation solution: Mix the primary alkaline leaching solution and acid precipitation solution and adjust the pH to 3-5 to obtain a mixed solution. Use resin to adsorb the mixed solution. S6, Washing-Desorption-Molybdenum Precipitation: The loaded resin after adsorption in step S5 is washed with pure water, and then the washed loaded resin is desorbed. The desorbed solution is precipitated with nitric acid, and the acid-precipitated solution is diluted with water and returned to step S1 for pre-soaking. The desorbed empty resin is returned to step S5. S7. Extraction: The pre-impregnation solution is extracted using a system of N235 + isooctyl alcohol + kerosene. The resulting organic-rich phase is washed and back-extracted to recover molybdenum and rhenium. The raffinate is treated as wastewater after copper recovery through sulfide precipitation.

[0008] Furthermore, in step S1, the liquid-to-solid ratio in the pre-soaking is 3-6:1 (mL / g), the temperature is 85-95℃, and the reaction time is 1-3h.

[0009] Further, in step S2, the liquid-to-solid ratio of pure water and pre-impregnated residue is 3-5:1 (mL / g), the temperature of the first ammonia leaching is 50-60℃, and the reaction time is 1h; 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 1h.

[0010] Furthermore, in step S3, the liquid-to-solid ratio of the first alkaline leaching is 3-5:1 (mL / g), the temperature is 85-95℃, and the reaction time is 1-2 hours.

[0011] Further, in step S4, the liquid-to-solid ratio in the second alkaline leaching is 3-5:1 (mL / g), and 40-70 g / L sodium hydroxide and 10-20 g / L sodium carbonate are added, the temperature is 90-95℃, and the reaction time is 2-3 h.

[0012] Further, in step S5, the resin is a macroporous weakly basic anion exchange resin, the flow rate of the mixed liquid is 0.5-3 BV / h, the adsorption endpoint is the Mo concentration of the adsorption tail liquid > 100 mg / L, and the adsorption tail liquid is treated as wastewater.

[0013] Further, in step S6, the washing water flow rate is 1-3 BV / h, and the washing endpoint is that the Na content in the washing tail liquid is <5 mg / L; the washed loaded resin is desorbed using ammonia water with a mass concentration of 5-10%, and the ammonia water flow rate is 1-5 BV / h; the desorbed liquid is precipitated with industrial nitric acid with a mass concentration of 68% at a temperature of 40℃, and after adding acid to the endpoint pH=3.5, it is immediately filtered.

[0014] Furthermore, the wash water generated from washing the secondary alkaline leaching residue in step S4 enters the second alkaline leaching process and mixes with the primary alkaline leaching residue to participate in the second alkaline leaching.

[0015] Further, in step S7, the volume concentration of N235 is 5-10%, the volume concentration of isooctanol is 10%, and the remainder is kerosene; the oil-to-water ratio of the extraction is 1 / 2-1 / 5, and the number of extraction stages is 3-5.

[0016] The beneficial effects of this invention are as follows: The core advantage of this invention lies in achieving efficient recovery of molybdenum (Mo) and rhenium (Re) through process innovation. It relies on a leaching system of "one-time ammonia leaching of molybdenum roasted sand + two-time countercurrent alkaline leaching," coupled with a cyclic process of "synergistic adsorption for molybdenum extraction—molybdenum precipitation to ammonium tetramolybdate—water replenishment and pre-leaching," deeply integrating ammonia leaching residue treatment with the classic ammonia leaching process. This not only reduces residual molybdenum in the tailings but also controls the ammonium concentration in the pre-leaching solution to overcome extraction inhibition, ultimately improving the total recovery rate of rhenium and molybdenum. Specific effects are as follows: (1) Reduce Mo loss in slag and shorten process flow: The three-stage atmospheric pressure leaching process of "one ammonia leaching + two countercurrent alkaline leaching" can stably control the molybdenum content in the tailings to below 1%. Compared with the traditional process, there is no need to add multiple leaching units and high-pressure equipment, which shortens the process from the source: It avoids the high investment and operation and maintenance costs of high-pressure equipment, reduces the amount of ammonia waste gas generated by ammonia leaching, reduces environmental pressure, and avoids the cumulative molybdenum loss caused by multiple leaching. (2) Precise control of silicon to extract molybdenum and save on reagent consumption: In the leaching stage, the alkalinity is precisely controlled. The pH of the first alkaline leaching is 10-11 and the pH of the second alkaline leaching is 13-13.5. This allows silicon to be directionally retained in the second alkaline leaching solution, preventing silicon from migrating to subsequent processes and thus solving the adverse effects of high silicon on the adsorption unit. At the same time, it reduces the excess coefficient of alkaline leaching reagent and the amount of sulfuric acid consumed in the subsequent acid adjustment process. (3) Improve the extraction rate of Mo and Re in the pre-leaching solution: The acid precipitation solution and the primary alkaline leaching solution are combined to adsorb and recover molybdenum. After desorption-acid precipitation to prepare ammonium tetramolybdate, the concentration of ammonium ions in the pre-leaching solution is adjusted by adding water for dilution. This adjustment achieves a two-way balance of ammonium ion concentration: it retains its inhibitory effect on excessive leaching of molybdenum while controlling the concentration within a reasonable range that does not affect subsequent extraction, thereby improving the rhenium-molybdenum extraction rate. Attached Figure Description

[0017] Figure 1 The above are process flow diagrams for embodiments 1-3 of the present invention. Detailed Implementation

[0018] 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.

[0019] Example 1

[0020] This embodiment provides a method for 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, roasted and desulfurized to obtain molybdenum roasted sand. The mass contents of Mo, Cu and S in the molybdenum roasted sand are 45.11%, 4.03% and 0.11%, respectively. Take 500 ml of the acid precipitation liquid obtained in step (6), add 2500 ml of fresh water to dilute to 3000 mL, add 250 g of nitric acid, add 1000 g of roasted sand at a liquid-solid ratio of 3:1 mL / g, temperature 90℃, reaction time 2 h, endpoint pH=1.12, to obtain pre-leaching solution and pre-leaching residue. The concentrations of Mo, Re and Cu in the pre-leaching solution are 4.38 g / L, 163.80 mg / L and 13.88 g / L, respectively, and the weight of the pre-leaching residue is 895.31 g. The pre-leaching solution is sent to step (7) for treatment. (2) First ammonia leaching: Add pure water to the above 895.31g of pre-leaching residue at a liquid-to-solid ratio of 3:1 mL / g to slurry, add ammonia water and carry out ammonia leaching under normal pressure, control the endpoint pH=9, temperature 60℃, and react for 1h to obtain a first ammonia leaching solution and 330.22g of first ammonia leaching residue. After purifying the first ammonia leaching solution with a mass concentration of 10% ammonium sulfide solution, the purified solution is acid-precipitated to prepare ammonium molybdate product; the acid-precipitated solution is transferred to step (5) for adsorption treatment; (3) First alkaline leaching: Add the second alkaline leaching solution from step (4) to the above 330.22g of first ammonia leaching residue, with a liquid-to-solid ratio of mL / g 3:1, and carry out the first alkaline leaching under normal pressure at a temperature of 90℃ for 1h. The final pH is 11, and the first alkaline leaching residue and the first alkaline leaching solution are obtained. The first alkaline leaching solution is transferred to step (5) for adsorption treatment. (4) Secondary alkaline leaching: The above-mentioned primary alkaline leaching residue is added to the washing water and fresh water of the secondary alkaline leaching residue at a liquid-solid ratio of 5:1, and 50g / L sodium hydroxide and 20g / L sodium carbonate are added. The secondary alkaline leaching is carried out under normal pressure at a temperature of 90℃ for 2 hours. The final pH is 13.36. The secondary alkaline leaching residue is washed and sold. All the secondary alkaline leaching liquid is returned to step (3) to participate in the first alkaline leaching. (5) Adsorption of primary alkaline leaching solution and acid precipitation solution: The primary alkaline leaching solution and acid precipitation solution are mixed and the pH is adjusted to 5 to obtain the mixed solution. The mixed solution is treated with D314 large-pore weak alkaline anion exchange resin at a flow rate of 1 BV / h until the Mo concentration of the adsorption tail liquid is >100 mg / L. The adsorption tail liquid is treated as wastewater. (6) Washing-desorption-molybdenum precipitation: After adsorption, the loaded resin is washed with pure water at a flow rate of 2 BV / h until the Na content of the washing tail liquid is <5 mg / L. The loaded resin is desorbed with 6% ammonia water at a flow rate of 2 BV / h. The desorbed liquid is precipitated with industrial nitric acid with a mass concentration of 68% at a temperature of 40℃. After adding acid to the endpoint pH=3.5, it is immediately filtered. The acid precipitation liquid is diluted with water and returned to the pre-impregnation step (1). The empty loaded resin is returned to step (5). (7) Extraction: The pre-leaching solution was extracted using a system of "N235 + isooctanol + kerosene". The volume concentration of N235 was 10%, the volume concentration of isooctanol was 10%, and the remainder was kerosene. The oil-to-water ratio of the extract was 1 / 3, and the number of stages was 3. The resulting organic-rich phase was washed and back-extracted to recover molybdenum and rhenium. The raffinate was treated as wastewater after copper precipitation by sulfidation.

[0021] The process parameters of this embodiment are shown in Table 1.

[0022] Table 1

[0023] Note: "*" indicates the unit is g / t.

[0024] Example 2

[0025] This embodiment provides a method for 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 was oxidized, roasted and desulfurized to obtain molybdenum roasted sand, in which the mass contents of Mo, Cu and S were 40.35%, 7.52% and 0.10%, respectively. Take 500 ml of the acid precipitation solution obtained in step (6), add 2500 ml of fresh water to dilute to 3000 mL, add 450 g of nitric acid, add 1000 g of roasted sand at a liquid-to-solid ratio of 3:1 mL / g, the temperature was 90℃, the reaction time was 2 h, and the final pH was 0.95 to obtain pre-leaching solution and pre-leaching residue. The concentrations of Mo, Re and Cu in the pre-leaching solution were 3.95 g / L, 159.36 mg / L and 24.98 g / L, respectively, and the weight of the pre-leaching residue was 822.51 g. (2) Primary ammonia leaching: Pure water was added to the above pre-leached residue at a liquid-to-solid ratio of 3:1 mL / g to form a slurry. Ammonia water was added and ammonia leaching was carried out under normal pressure. The final pH was controlled at 8.5 and the temperature at 60℃. The reaction was carried out for 1 hour to obtain primary ammonia leaching solution and 301.32 g of primary ammonia leaching residue. After the primary ammonia leaching solution was purified with a 10% ammonium sulfide solution, the purified solution was acid-precipitated to prepare ammonium molybdate product. The acid-precipitated solution was transferred to step (5) for adsorption treatment. (3) First alkaline leaching: The above 301.32g of the first ammonia leaching residue was added to all the second alkaline leaching solution from step (4), with a liquid-to-solid ratio of 4:1 mL / g. The first alkaline leaching was carried out under normal pressure at a temperature of 90℃ for 1 hour, with an endpoint pH of 10.35, to obtain the first alkaline leaching solution and the first alkaline leaching residue. The first alkaline leaching solution was sent to step (5) for adsorption treatment; (4) Secondary alkaline leaching: Add the washing water and fresh water of the secondary alkaline leaching residue to the above primary alkaline leaching residue at a liquid-solid ratio of 5:1, add 60g / L sodium hydroxide and 20g / L sodium carbonate, carry out the second alkaline leaching under normal pressure, temperature 90℃, reaction time 2h, and endpoint pH=13.5. The generated secondary alkaline leaching residue is washed and sold, and all the secondary alkaline leaching liquid is returned to step (3) to participate in the first alkaline leaching. (5) Adsorption of primary alkaline leaching solution and acid precipitation solution: The primary alkaline leaching solution and acid precipitation solution are mixed and the pH is adjusted to 5. The mixed solution is treated with D314 large-pore weak alkaline anion exchange resin at a flow rate of 1 BV / h until the Mo concentration of the adsorption tail liquid is >100 mg / L. The adsorption tail liquid is treated as wastewater. (6) Washing-desorption-molybdenum precipitation: The loaded resin obtained after adsorption in step (5) is washed with pure water at a flow rate of 2 BV / h until the Na content of the washing tail liquid is <5 mg / L. The washed loaded resin is desorbed with 5% ammonia water at a flow rate of 1 BV / h. The desorbed liquid is precipitated with industrial nitric acid with a mass concentration of 68% at a temperature of 40℃. After adding acid to the endpoint pH=3.5, it is immediately filtered. The acid precipitation liquid is diluted with water and returned to the pre-impregnation process in step (1). The empty adsorbent is returned to step (5). (7) Extraction: The pre-impregnation solution is extracted using the “N235 + isooctyl alcohol + kerosene” system. The volume concentration of N235 is 10%, the volume concentration of isooctyl alcohol is 10%, the oil-water ratio is 1 / 2, and the number of stages is 3. The resulting organic-rich phase is washed and back-extracted to recover molybdenum and rhenium. The raffinate is treated as wastewater after copper precipitation by sulfidation.

[0026] The process parameters obtained in this embodiment are shown in Table 2.

[0027] Table 2

[0028] Note: "*" indicates the unit is g / t.

[0029] Example 3

[0030] This embodiment provides a method for 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-impregnation: The raw material of molybdenum calcined sand is the same as in Example 2. Take 500 ml of the acid-precipitated liquid obtained in step (6), add 2500 ml of fresh water to dilute to 3000 mL, add 450 g of nitric acid, add 1000 g of calcined sand according to the liquid-to-solid ratio of mL / g 3:1, the temperature is 90℃, the reaction time is 2 h, the endpoint pH=0.96, and the pre-impregnation liquid and pre-impregnation residue are obtained. The concentrations of Mo, Re and Cu in the pre-impregnation liquid are 3.86 g / L, 153.12 mg / L and 23.86 g / L, respectively, and the weight of the pre-impregnation residue is 820.11 g; (2) Primary ammonia leaching: Pure water was added to the above pre-leached residue at a liquid-to-solid ratio of 3:1 (mL / g) to form a slurry. Ammonia water was added and ammonia leaching was carried out under normal pressure. The final pH was controlled at 8, the temperature at 60℃, and the reaction was carried out for 1 hour to obtain primary ammonia leaching solution and 308.67g of primary ammonia leaching residue. After the primary ammonia leaching solution was purified with a 10% ammonium sulfide solution, the purified solution was acid-precipitated to prepare ammonium molybdate product. The acid-precipitated solution was transferred to step (5) for adsorption treatment. (3) First alkaline leaching: The above 308.67g of the first ammonia leaching residue was added to all the second alkaline leaching solution obtained in step (4), with a liquid-to-solid ratio of 3.5:1 mL / g. The first alkaline leaching was carried out under normal pressure at a temperature of 90℃ for 1 hour, with an endpoint pH of 10, to obtain the first alkaline leaching solution and the first alkaline leaching residue. The first alkaline leaching solution was sent to step (5) for adsorption treatment; (4) Secondary alkaline leaching: Add the washing water and fresh water of the secondary alkaline leaching residue to the above primary alkaline leaching residue at a liquid-solid ratio of 5:1, add 50g / L sodium hydroxide and 20g / L sodium carbonate, carry out the second alkaline leaching under normal pressure, temperature 90℃, reaction time 2h, endpoint pH=13, the generated secondary alkaline leaching residue is washed and sold, and all secondary alkaline leaching liquid is returned to step (3) to participate in the first alkaline leaching; (5) Adsorption of primary alkaline leaching solution and acid precipitation solution: The primary alkaline leaching solution and acid precipitation solution are mixed and the pH is adjusted to 5. The mixed solution is treated with D314, a large-pore weak basic anion exchange resin, at a flow rate of 1.5 BV / h until the Mo concentration of the adsorption tail liquid is >100 mg / L. The adsorption tail liquid is then treated as wastewater. (6) Washing-desorption-molybdenum precipitation: The loaded resin obtained after adsorption in step (5) is washed with pure water at a flow rate of 2 BV / h until the Na content of the washing tail liquid is <5 mg / L. The washed loaded resin is desorbed with 6% ammonia water at a flow rate of 1 BV / h. The desorbed liquid is precipitated with industrial nitric acid with a mass concentration of 68% at a temperature of 40℃. After adding acid to the endpoint pH=3.5, it is immediately filtered. The acid precipitation liquid is diluted with water and returned to the pre-impregnation process in step (1). The empty adsorbent is returned to step (5). (7) Extraction: The pre-impregnation solution is extracted using the “N235 + isooctanol + kerosene” system. The volume concentration of N235 is 10%, the volume concentration of isooctanol is 10%, the oil-water ratio is 1 / 3, and the number of stages is 3. The resulting organic-rich phase is washed and back-extracted to recover molybdenum and rhenium. The raffinate is treated as wastewater after copper precipitation by sulfidation.

[0031] The process parameters obtained in this embodiment are shown in Table 3.

[0032] Table 3

[0033] Note: "*" indicates the unit is g / t.

[0034] Comparative Example 1 Taking molybdenum calcined abrasive with Mo, Cu, and S contents of 45.11%, 4.03%, and 0.11%, respectively, as an example, the classic ammonia leaching process is adopted. The molybdenum calcined abrasive undergoes four countercurrent ammonia leaching processes. Ammonium molybdate is prepared by acid precipitation of the first ammonia leaching solution. The acid precipitation solution is not subjected to adsorption treatment but is entirely returned to the pre-leaching solution for extraction. The specific process is as follows: (1) Pre-impregnation: Take 3000ml of acid precipitation solution, add 250g of nitric acid, add 1000g of calcined sand according to the liquid-solid ratio of mL / g 3:1, temperature 90℃, reaction time 2h, endpoint pH=1.09, the concentrations of Mo, Re and Cu in the obtained pre-impregnation solution are 4.21g / L, 171.80mg / L and 12.56g / L respectively, and 912.5g of pre-impregnation residue is obtained; (2) Primary ammonia leaching: The above pre-leached residue is added to all the secondary ammonia leaching liquid from step (3) for pulping. Ammonia water is added to control the endpoint pH=8.5, the temperature is 60℃, and the reaction is carried out for 1 hour to obtain primary ammonia leaching liquid and primary ammonia leaching residue. The generated primary ammonia leaching liquid is purified, and the purified liquid is acid-precipitated to prepare ammonium molybdate product. All acid-precipitated liquid is returned to pre-leaching, and the primary ammonia leaching residue is subjected to a second ammonia leaching. (3) Secondary ammonia leaching: The above primary ammonia leaching residue is added to all the tertiary ammonia leaching liquid from step (4) and pulped. The final pH is controlled by ammonia water, the temperature is 65℃, and the reaction time is 1h to obtain secondary ammonia leaching liquid and secondary ammonia leaching residue. 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 added to all the fourth ammonia leaching liquid from step (5) for pulping. The final pH is controlled by ammonia water, the temperature is 70℃, and the reaction time is 1h to obtain the third ammonia leaching liquid and the third ammonia leaching residue. 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-time ammonia leaching: The residue from the three-time ammonia leaching was slurried with pure water and washing water at a liquid-to-solid ratio of 15:1. The final pH was controlled at 10 using ammonia water, the temperature was 75℃, and the reaction time was 2 hours to obtain the four-time ammonia leaching solution and the four-time ammonia leaching residue. All of the four-time ammonia leaching solution was returned to the third ammonia leaching, and the four-time ammonia leaching residue was sold after washing. (6) Extraction: The pre-leaching solution was extracted using a system of "N235 + isooctanol + kerosene". The concentration of N235 was 30%, the concentration of isooctanol was 10%, and the remainder was kerosene. The oil-to-water ratio of the extract was 1 / 3, and the number of stages was 3. The resulting organic-rich phase was washed and back-extracted to recover molybdenum and rhenium. The raffinate was treated as wastewater after copper precipitation by sulfidation.

[0035] The results of this comparative example are shown in Table 4.

[0036] Table 4

[0037] Note: "*" indicates the unit is g / t.

[0038] Comparative Example 2 Taking molybdenum calcined sand with Mo, Cu and S contents of 45.11%, 4.03% and 0.11% as an example, the pH control conditions for the two countercurrent alkaline leachings were changed, while the rest were the same as in Example 1.

[0039] In the first alkaline leaching, the residue from the first ammonia leaching is added to all the second alkaline leaching solution, sodium hydroxide is added, the final pH is controlled at 13, the temperature is 90℃, and the reaction time is 1 hour to obtain the residue from the first alkaline leaching. In the secondary alkaline leaching process, the primary alkaline leaching residue is added to the secondary alkaline leaching residue washing water and fresh water at a liquid-to-solid ratio of 5:1. 40 g / L sodium hydroxide and 20 g / L sodium carbonate are added, the temperature is 90℃, the reaction time is 2 h, and the final pH is 13.46. The resulting secondary alkaline leaching residue is washed and sold, while all the secondary alkaline leaching solution is returned to the primary alkaline leaching process.

[0040] The results obtained from this comparative example are shown in Table 5.

[0041] Table 5

[0042] Note: "*" indicates the unit is g / t.

[0043] It can be seen that Examples 1, 2 and 3 can achieve Mo content <1%, Re <1.5g / t in the residue, Mo <100mg / L and Re <2mg / L in the raffinate, and Si <100mg / L in the primary alkaline leaching solution.

[0044] As can be seen from Comparative Example 1, even with multiple ammonia leaching processes (four times), the Mo content in the residue is still as high as 4.56%. In the pre-leaching extract unit, even with the N235 extractant concentration increased to 30%, the Mo and Re concentrations in the raffinate are still as high as 1.06 g / L and 25.96 mg / L, respectively, resulting in severe losses of molybdenum and rhenium.

[0045] As can be seen from Comparative Example 2, increasing the pH of the first alkaline leaching to 13 leads to a significant increase in the Si content of the first alkaline leaching solution. In the subsequent ion exchange, Si will be adsorbed together with Mo, and the formed silica gel easily clogs the microporous structure of the resin, affecting product purity and adsorption. Therefore, controlling the final pH of the first alkaline leaching at 10-11 and the pH of the second alkaline leaching at 13-13.5 can not only save reagent consumption and reduce the molybdenum content in the tailings, but also control the entry of silicon into the first alkaline leaching solution, avoiding the harm of silicon to the entire process system.

[0046] In summary, based on the classic ammonia leaching process, the process of "one ammonia leaching + two countercurrent alkaline leaching" and "alkaline leaching solution and acid precipitation solution adsorb and recover molybdenum, desorption solution precipitates molybdenum and then replenishes water for dilution and returns to pre-leaching" can effectively reduce the Mo content in the residue, control the ammonium concentration in the extraction solution, improve the extraction rate of Mo and Re, and significantly improve the total recovery rate of Mo and Re.

[0047] 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 improving the recovery rate of molybdenum and rhenium in a classic ammonia leaching process, characterized in that, Includes the following steps: S1. After desulfurization by oxidative roasting, the molybdenum concentrate is pre-leached with nitric acid solution, and the final pH is controlled to be 0.95-1.12 to obtain pre-leached residue and pre-leaching solution. The pre-leaching solution is transferred to step S7 for further processing. S2, Primary ammonia leaching: After mixing the pre-leaching residue and pure water, ammonia leaching is carried out under normal pressure using ammonia water or liquid ammonia, controlling the endpoint pH=8-9, to produce primary ammonia leaching solution and primary ammonia leaching residue; after purifying the primary ammonia leaching solution with ammonium sulfide, the purified solution is acid-precipitated to prepare ammonium molybdate product, and the acid precipitation solution produced by acid precipitation is transferred to step S5 for treatment. S3. First alkaline leaching: The first ammonia leaching residue obtained in step S2 is subjected to a first 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 to perform a first alkaline leaching of the first ammonia leaching residue, and the final pH is controlled at 10-11. The first alkaline leaching yields first alkaline leaching residue and first alkaline leaching solution. The first alkaline leaching residue is processed in step S4, and the first alkaline leaching solution is processed in step S5. S4. Secondary alkaline leaching: The primary alkaline leaching residue obtained in step S3 is subjected to a second alkaline leaching under normal pressure, with the endpoint pH controlled at 13-13.5, to obtain secondary alkaline leaching residue and secondary alkaline leaching solution. The secondary alkaline leaching residue is washed and sold externally, while the secondary alkaline leaching solution is returned to step S3 to participate in the first alkaline leaching. S5. Adsorption of primary alkaline leaching solution and acid precipitation solution: Mix the primary alkaline leaching solution and acid precipitation solution and adjust the pH to 3-5 to obtain a mixed solution. Use resin to adsorb the mixed solution. S6, Washing-Desorption-Molybdenum Precipitation: The loaded resin after adsorption in step S5 is washed with pure water, and then the washed loaded resin is desorbed. The desorbed solution is precipitated with nitric acid, and the acid-precipitated solution is diluted with water and returned to step S1 for pre-soaking. The desorbed empty resin is returned to step S5. S7. Extraction: The pre-impregnation solution is extracted using a system of N235 + isooctyl alcohol + kerosene. The resulting organic-rich phase is washed and back-extracted to recover molybdenum and rhenium. The raffinate is treated as wastewater after copper recovery through sulfide precipitation.

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

3. The method according to claim 1, characterized in that, In step S2, the liquid-to-solid ratio of pure water and pre-impregnated residue is 3-5:1 (mL / g), the temperature of the first ammonia leaching is 50-60℃, and the reaction time is 1h; 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 1h.

4. The method according to claim 1, characterized in that, In step S3, the liquid-to-solid ratio of the first alkaline leaching is 3-5:1 (mL / g), 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 in the second alkaline leaching is 3-5:1 (mL / g), and 40-70 g / L sodium hydroxide and 10-20 g / L sodium carbonate are added. The temperature 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 resin is a macroporous weakly basic anion exchange resin, the flow rate of the mixed liquid is 0.5-3 BV / h, the adsorption endpoint is when the Mo concentration of the adsorption tail liquid is >100 mg / L, and the adsorption tail liquid is treated as wastewater.

7. The method according to claim 1, characterized in that, In step S6, the washing water flow rate is 1-3 BV / h, and the washing endpoint is that the Na content in the washing tail liquid is <5 mg / L; the washed loaded resin is desorbed using ammonia water with a mass concentration of 5-10% at a flow rate of 1-5 BV / h; the desorbed liquid is precipitated with industrial nitric acid with a mass concentration of 68% at a temperature of 40℃, and after adding acid to the endpoint pH=3.5, it is immediately filtered.

8. The method according to claim 1, characterized in that, The wash water generated from washing the secondary alkaline leaching residue in step S4 enters the second alkaline leaching process and mixes with the primary alkaline leaching residue to participate in the second alkaline leaching.

9. 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 oil-to-water ratio of the extraction is 1 / 2-1 / 5, and the number of extraction stages is 3-5.

Images