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CN-121974399-A - Preparation method for producing high-purity ammonium tetramolybdate by using low-grade molybdenite

CN121974399ACN 121974399 ACN121974399 ACN 121974399ACN-121974399-A

Abstract

The invention belongs to the technical field of production and preparation of ammonium tetramolybdate, and particularly relates to a preparation method for producing high-purity ammonium tetramolybdate by using low-grade molybdenite. The invention selectively oxidizes and activates the surface of molybdenite under mild conditions, and simultaneously utilizes ammonium ions to inhibit the dissolution of associated metal sulfides. The synergistic purification strategy of lime milk sulfur fixation and carbon dioxide carbonation is adopted, sulfate radical is efficiently precipitated by low-cost lime milk, ammonia gas is synchronously recovered, and the pH value is accurately regulated and controlled through the mild acidification of carbon dioxide, so that residual calcium, magnesium and heavy metal ions are deeply removed in a carbonate form. Finally, by means of the specific chelation of the aminophosphonic acid functionalized mesoporous adsorbent to heavy metal ions and the membrane separation and resource recycling of the electrodialysis-mother solution circulation system to impurity ions, the ammonium tetramolybdate product purity is ensured, and meanwhile, the production process with no roasting and high resource utilization rate is formed.

Inventors

  • XU HONGFEI
  • XU SHENGYUN
  • RAO SENLIN
  • XU ZUNPING

Assignees

  • 安庆市月铜钼业有限公司

Dates

Publication Date
20260505
Application Date
20260320

Claims (10)

  1. 1. The preparation method for producing high-purity ammonium tetramolybdate by using low-grade molybdenite is characterized by comprising the following steps of: S1, activating and leaching: after the ground low-grade molybdenite is pretreated and activated, oxygen-enriched air is introduced into an ammoniacal medium for pressurized oxidation leaching, so that the selective leaching of molybdenum is realized; s2, collaborative purification: Adding lime milk into the leaching solution to remove sulfate radical, recovering ammonia gas, and introducing CO 2 to remove residual calcium, magnesium and heavy metal ions to obtain a pre-purified solution; s3, targeted adsorption refining: deeply adsorbing the pre-purified liquid by an aminophosphonic acid functionalized silicon-based adsorbent to remove trace heavy metal impurities; s4, crystallization and post-treatment: evaporating, concentrating, cooling and crystallizing the solution after the adsorption refining, and obtaining a high-purity ammonium tetramolybdate product after solid-liquid separation, washing and drying; s5, mother liquor circulation: Removing impurity ions from the crystallization mother liquor through membrane separation, and returning the crystallization mother liquor to the system for recycling after purification.
  2. 2. The preparation method according to claim 1, wherein step S1 specifically comprises: S101, crushing and grinding low-grade molybdenite until the grain diameter is less than or equal to 45 mu m, adding water for size mixing, adding soluble ammonium salt with the mass of 3-5% of mineral powder and sodium silicate with the mass of 0.05-0.15%, dropwise adding 3-5% of hydrogen peroxide solution in batches, and pre-treating for 0.8-1.2 h at 55-65 ℃; S102, adding ammonia water into the pretreated ore pulp to adjust the pH value to 9.8-10.2, adding 5-8% of NH 4 HCO 3 as a buffering agent, introducing oxygen-enriched air with the oxygen volume fraction of 15-25%, and reacting for 3-4 hours at the temperature of 85-90 ℃ and the gauge pressure of 0.3-0.4 MPa, so as to maintain the dissolved oxygen to be more than or equal to 6mg/L.
  3. 3. The preparation method according to claim 2, wherein the soluble ammonium salt is one of ammonium sulfate, ammonium nitrate or ammonium chloride, and the hydrogen peroxide solution is added in 3-4 times at intervals of 10-20 min each time.
  4. 4. The preparation method according to claim 1, wherein step S2 specifically comprises: S201, heating the leaching solution to 60-70 ℃, adding saturated lime milk to pH 10.5-11.0, reacting for 30-45 min, filtering to remove CaSO 4 ·2H 2 O precipitate, and recovering escaped ammonia gas; And S202, introducing CO 2 gas into the filtrate, adjusting the pH of the system to 8.5-9.0, reacting for 20-30 min, and filtering to enable residual calcium, magnesium and heavy metal ions to generate carbonate or basic carbonate to be removed.
  5. 5. The preparation method according to claim 1, wherein step S3 specifically comprises: The prepurification liquid is passed through two-stage series-connected aminophosphonic acid functionalized silicon-based adsorbent at the flow rate of 1.5-2.5 BV/h, the adsorbent takes ordered mesoporous silica as a carrier, aminophosphonic acid groups are grafted by a vapor deposition method, the phosphorus element content is more than or equal to 2.5mmol/g, and the concentration of Cu 2+ 、Fe 3+ in the outlet liquid is controlled to be less than or equal to 0.1mg/L.
  6. 6. The method of claim 5, wherein the preparation of the aminophosphonic acid functionalized silica-based adsorbent comprises the steps of: (1) Placing ordered mesoporous silica with the specific surface area of more than or equal to 600m 2 /g and the aperture of 6-8 nm in a muffle furnace, heating to 550-600 ℃ at the speed of 2-3 ℃/min under the air atmosphere, carrying out heat preservation and roasting for 4-6 h, and then carrying out vacuum drying at 120-130 ℃ for 10-14 h to obtain an activated carrier; (2) Placing the activated carrier obtained in the step (1) into a fluidized bed reactor, preheating a reactor jacket to 115-125 ℃, placing 3-aminopropyl triethoxysilane into a constant temperature evaporator, heating to 85-95 ℃ to vaporize the 3-aminopropyl triethoxysilane, taking high-purity N 2 as carrier gas, controlling the volume fraction of 3-aminopropyl triethoxysilane vapor in the nitrogen carrier gas to be 5-10%, controlling the flow rate of the carrier gas to be 200-300 mL/min, introducing the carrier gas into the fluidized bed reactor, carrying silane vapor to react with the carrier in a contact manner for 2.5-3.5 h under the condition of 3-8 kPa, stopping introducing silane vapor after the reaction is finished, and continuing to purge the carrier gas with pure nitrogen at the flow rate of 300-400 mL/min for 1-1.5 h to obtain an amino-functionalized silicon-based intermediate; (3) Transferring the intermediate obtained in the step (2) into a sealed corrosion-resistant reaction kettle lined with polytetrafluoroethylene, adding high-purity phosphorus trichloride into an independent liquid storage tank at the bottom of the reaction kettle, wherein the mass ratio of the phosphorus trichloride to the intermediate is (0.15-0.25): 1; (4) Transferring the solid product obtained in the step (3) into a Soxhlet extractor, extracting with absolute ethyl alcohol under reflux for 22-26 h, placing the extracted material into a supercritical CO 2 drying device, drying for 5-7 h under the conditions of 40-45 ℃ and 9-11 MPa, and finally activating the dried material for 1.5-2.5 h under the conditions of vacuum degree of less than or equal to-0.095 MPa and 80-85 ℃ to obtain the aminophosphonic acid functional silicon-based adsorbent.
  7. 7. The preparation method according to claim 6, wherein the gradient temperature-increasing reaction specifically comprises: the first stage, cooling the system to-5 to 0 ℃ and keeping the temperature for 1 to 1.5 hours; a second stage, namely raising the system temperature from-5 ℃ to 58-62 ℃ at a rate of 0.8-1.2 ℃ per minute, and keeping the system temperature for 3.5-4.5 hours; And in the third stage, 80-85 ℃ saturated steam is introduced into the reaction kettle through a precise metering pump, the water steam introduction rate is controlled to be 0.4-0.6 g/min, the continuous introduction is carried out for 1.8-2.2 h, and the hydrogen chloride gas as a reaction byproduct is treated through a tail gas alkali liquor absorption system.
  8. 8. The preparation method according to claim 1, wherein step S4 specifically comprises: S401, evaporating and concentrating the solution subjected to the adsorption refining to a density of 1.25-1.32 g/cm 3 at a vacuum degree of-0.07 to-0.09 MPa and a temperature of 65-75 ℃; S402, cooling the concentrated solution from 70 ℃ to 50 ℃ at a rate of 3-5 ℃ per hour, adding ammonium tetramolybdate seed crystals accounting for 0.05-0.15% of the total mass of the solution, cooling to 20-25 ℃ at a rate of 8-12 ℃ per hour, aging for 1-2 hours, and then performing solid-liquid separation to obtain ammonium tetramolybdate wet crystals; And S403, washing the wet ammonium tetramolybdate crystal with deionized water and absolute ethyl alcohol at 0-10 ℃ in sequence, and then drying the wet ammonium tetramolybdate crystal at 80-95 ℃ under vacuum conditions to obtain a high-purity ammonium tetramolybdate product.
  9. 9. The method according to claim 5 or 6, further comprising an adsorbent regeneration step of desorbing the saturated adsorbent at a flow rate of 0.8-1.2 BV/h with a dilute hydrochloric acid or dilute nitric acid solution having a concentration of 0.5-1.2 mol/L for a desorption time of 1.5-2.5 h, and then sequentially washing and regenerating with deionized water and 2-5% by mass of dilute ammonia water until the pH value of the effluent is 8.0-9.0.
  10. 10. The method according to claim 1, wherein the membrane separation in step S5 is electrodialysis, the electrodialysis is a monovalent selective anion exchange membrane, the electrodialysis is operated at a voltage of 10 to 20 v/membrane pair and a current density of 10 to 30ma/cm 2 .

Description

Preparation method for producing high-purity ammonium tetramolybdate by using low-grade molybdenite Technical Field The invention belongs to the technical field of production and preparation of ammonium tetramolybdate, and particularly relates to a preparation method for producing high-purity ammonium tetramolybdate by using low-grade molybdenite. Background Molybdenite (MoS 2) is the main mineral raw material for extracting molybdenum. The main flow process for producing ammonium tetramolybdate is an oxidizing roasting-alkaline leaching-ion exchange/extraction-acid precipitation crystallization route. For low-grade molybdenite, the method has the remarkable defects of (1) roasting pollution, namely a large amount of low-concentration SO 2 smoke generated in the oxidizing roasting process, high treatment cost and serious environmental pollution. (2) The impurity interference is large, a large amount of impurities such as copper, iron, lead, calcium, silicon dioxide and the like associated in low-grade ores enter the solution during alkaline leaching, the load of the subsequent purification section is heavy, the molybdenum loss rate is high, and the purity of the product is difficult to ensure. And (3) the process is long, and the reagent consumption is high. In order to avoid roasting pollution, the prior art proposes wet direct leaching schemes such as normal pressure alkaline oxidation leaching or oxygen pressure leaching, and the like, and generally uses a NaOH or Na 2CO3 system and adds a strong oxidant (such as sodium chlorate and sodium nitrate). However, these methods have poor selectivity in the treatment of low-grade ores, severe co-leaching of impurities, and the introduction of new impurity ions (e.g., cl -、NO3-) is possible. The subsequent deep impurity removal usually depends on toxic vulcanizing agents to precipitate heavy metals, or a large amount of acid and alkali are used for carrying out multiple precipitation-dissolution operations, so that the process is complex and new environmental protection and safety problems are generated. Therefore, the development of a short-flow preparation method which does not need roasting, avoids the use of toxic reagents and has the functions of high-selectivity leaching and high-efficiency separation on low-grade molybdenite has important significance. Disclosure of Invention The invention aims at solving the existing problems and provides a preparation method for producing high-purity ammonium tetramolybdate by using low-grade molybdenite. The invention is realized by the following technical scheme: a preparation method for producing high-purity ammonium tetramolybdate by using low-grade molybdenite comprises the following steps: S1, activating and leaching: after the ground low-grade molybdenite is pretreated and activated, oxygen-enriched air is introduced into an ammoniacal medium for pressurized oxidation leaching, so that the selective leaching of molybdenum is realized; s2, collaborative purification: Adding lime milk into the leaching solution to remove sulfate radical, recovering ammonia gas, and introducing CO 2 to remove residual calcium, magnesium and heavy metal ions to obtain a pre-purified solution; s3, targeted adsorption refining: deeply adsorbing the pre-purified liquid by an aminophosphonic acid functionalized silicon-based adsorbent to remove trace heavy metal impurities; s4, crystallization and post-treatment: evaporating, concentrating, cooling and crystallizing the solution after the adsorption refining, and obtaining a high-purity ammonium tetramolybdate product after solid-liquid separation, washing and drying; s5, mother liquor circulation: Removing impurity ions from the crystallization mother liquor through membrane separation, and returning the crystallization mother liquor to the system for recycling after purification. Further, the step S1 specifically includes: S101, crushing and grinding low-grade molybdenite until the grain diameter is less than or equal to 45 mu m, adding water for size mixing, adding soluble ammonium salt with the mass of 3-5% of mineral powder and sodium silicate with the mass of 0.05-0.15%, dropwise adding 3-5% of hydrogen peroxide solution in batches, and pre-treating for 0.8-1.2 h at 55-65 ℃; S102, adding ammonia water into the pretreated ore pulp to adjust the pH value to 9.8-10.2, adding 5-8% of NH 4HCO3 as a buffering agent, introducing oxygen-enriched air with the oxygen volume fraction of 15-25%, and reacting for 3-4 hours at the temperature of 85-90 ℃ and the gauge pressure of 0.3-0.4 MPa, so as to maintain the dissolved oxygen to be more than or equal to 6mg/L. Further, the soluble ammonium salt is one of ammonium sulfate, ammonium nitrate or ammonium chloride, and the hydrogen peroxide solution is added for 3-4 times at intervals of 10-20 min each time. Further, the step S2 specifically includes: S201, heating the leaching solution to 60-70 ℃, adding saturated lime milk to pH 10.5-11.0, reac