Green and environment-friendly ammonium molybdate production process

Abstract

The invention discloses a green and environment-friendly ammonium molybdate production process. The process specifically comprises the following steps: adding acid precipitation mother liquor, hydrochloric acid and industrial molybdenum oxide into a reaction kettle for pickling; separating the pickled material into a filter cake and wastewater, and performing ammonia leaching reaction on the filter cake; mixing the ammonia leaching liquid with hydrochloric acid for acid precipitation to generate mother liquor and ammonia leaching residues; precipitating iron in the wastewater by using sodium hydroxide, adding sodium sulfide and a chelating agent, filtering, and adding sodium hydroxide into filtrate to carry out ammonia gas concentration recovery, so as to obtain a concentrated solution which is a sodium chloride solution; the ammonia leaching residues are subjected to alkaline leaching, and soluble molybdenum metal in the residues is leached out; soluble molybdenum metal is adsorbed and desorbed, an ammonium molybdate solution is obtained after desorption, and column passing liquid obtained after adsorption is a sodium chloride solution. According to the production process, nitric acid in the pretreatment procedure and the acid precipitation procedure is replaced with hydrochloric acid, the ammonia leaching residue and wastewater treatment method is optimized, all finally formed wastewater is a sodium chloride solution, and the whole production process better conforms to the green and environment-friendly production mode.

Description

Technical Field

[0001] The invention belongs to the technical field of ammonium molybdate preparation, and in particular relates to a green and environment-friendly ammonium molybdate production process. Background Art

[0002] As an important chemical raw material, ammonium molybdate is widely used in aviation, aerospace, metallurgy, chemical industry and catalyst industries. The production process of ammonium molybdate mainly includes acid salt pretreatment production process, ion exchange resin and water washing pretreatment process. The acid salt pretreatment production process belongs to the traditional ammonium molybdate production process. The characteristics of this process are strong adaptability to raw materials, and it can produce ammonium tetramolybdate and ammonium dimolybdate at the same time, and the product quality is stable. The domestic production process mainly uses nitric acid for pretreatment and acid precipitation crystallization, so a large amount of acidic high ammonia nitrogen nitro wastewater is produced. Subject to the current environmental protection and safety policies, this production process can no longer adapt to the existing production and social environment. In addition, there is also a water-washed ammonium molybdate production process introduced by domestic companies from abroad. Although it solves the problem of ammonia nitrogen wastewater, the treatment process of water washing wastewater in the later stage is still immature, the production line has high requirements for raw materials, and the product categories are limited.

[0003] A Chinese patent (application number: 202211171590.5, publication number: CN115650293A, publication date: 2023.01.31) discloses a method for producing ammonium molybdate, specifically: pickling solid industrial molybdenum oxide and performing solid-liquid separation after the pickling operation to obtain a pickling solution and a filter cake; recovering molybdenum in the pickling solution, and treating the filter cake with an ammonia leaching process to obtain an ammonia leaching solution and ammonia leaching residue; acid precipitation treatment of the ammonia leaching solution to obtain ammonium molybdate and acid precipitation mother liquor, and the acid precipitation mother liquor is returned to the pickling operation for reuse. The ammonium molybdate production method greatly improves the pickling effect and the yield of ammonium molybdate. However, the production process uses nitric acid for production, and its disadvantage is that a large amount of acidic high-ammonia nitrogen wastewater is produced, the treatment cost is high, and the environmental protection requirements are also high. Summary of the invention

[0004] The purpose of the present invention is to provide a green and environmentally friendly production process of ammonium molybdate, which is safe and environmentally friendly and improves the production efficiency of ammonium molybdate.

[0005] The technical solution adopted by the present invention is a green and environmentally friendly ammonium molybdate production process, which is specifically implemented according to the following steps: Step 1, adding acid precipitation mother liquor, hydrochloric acid and industrial molybdenum oxide into a reaction kettle for pickling; Step 2, using plate and frame filtration to separate the pickled material into filter cake and wastewater, and subjecting the separated filter cake to an ammonia leaching reaction to generate an ammonia leaching solution; Step 3, mixing the ammonia leaching solution with hydrochloric acid, performing acid precipitation, and generating mother liquor and ammonia leaching residue; Step 4, adjusting the pH of the wastewater obtained in step 2 to 4-5 with sodium hydroxide, precipitating the iron in the wastewater, adding sodium sulfide and a chelating agent, filtering, adding sodium hydroxide to the filtrate to adjust the pH to 10-11, using a stripping tower to concentrate and recover ammonia, and reusing the concentrated ammonia water produced in the ammonia leaching process. The solution after concentration is a sodium chloride solution; Step 5, alkali leaching the ammonia leached residue to leach the soluble molybdenum metal in the residue; Step 6, using ion exchange method to adsorb and analyze the soluble molybdenum metal, the ammonium molybdate solution obtained after analysis, and the column liquid after adsorption is a sodium chloride solution.

[0006] The present invention is also characterized in that: In step 1, the pickling temperature is 90-100° C., the pickling time is 1-2 hours, and the stirring speed is 200-300 rpm.

[0007] In step 3, during acid precipitation, the temperature is 40-60° C., the time is 30-35 hours, and the stirring speed is 300-400 rpm.

[0008] In step 5, during alkali leaching, the temperature is 150-180° C., the pressure is 2.3-2.8 MPa, and the alkali is specifically sodium hydroxide.

[0009] In step 6, the ion exchange resin is specifically a macroporous strongly basic anion resin for adsorbing molybdenum.

[0010] The beneficial effect of the present invention is that the production process of the present invention optimizes the treatment method of ammonia leaching residue and wastewater by replacing nitric acid in the pretreatment process and the acid precipitation process with hydrochloric acid, and finally all the wastewater formed is only sodium chloride solution, so that the environmental protection treatment process of the entire production line becomes simple and easy, greatly reducing the cost, and making the entire production process more in line with the green and environmentally friendly production method. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The present invention is a flow chart of the green and environmentally friendly ammonium molybdate production process. DETAILED DESCRIPTION

[0012] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0013] The green and environmentally friendly ammonium molybdate production process of the present invention is as follows: Figure 1 As shown, the specific implementation steps are as follows: Step 1, adding acid precipitation mother liquor, hydrochloric acid and industrial molybdenum oxide into a reaction kettle, performing acid washing to wash out impurity ions in the industrial molybdenum oxide; Each ton of finished product produces 5-6 cubic meters of acid precipitation mother liquor, and the unit consumption of hydrochloric acid is 1.4-1.5 tons. The solid-liquid ratio of molybdenum oxide to acid precipitation mother liquor and hydrochloric acid is 1:3; The pickling temperature is 90-100°C, the pickling time is 1-2 hours, and the stirring speed is 200-300 rpm; Step 2, using plate and frame filtration to separate the pickled material into filter cake and wastewater, and subjecting the separated filter cake to an ammonia leaching reaction to generate an ammonia leaching solution; The ammonia leaching reaction is carried out by utilizing the property that industrial molybdenum oxide is easily soluble in alkaline solution. The reaction is an exothermic reaction.

[0014] Step 3, mixing the ammonia leaching solution with hydrochloric acid, performing acid precipitation, generating mother liquor and ammonia leaching residue, and the mother liquor enters the acid salt pretreatment process; Each cubic meter of ammonia leaching solution consumes 500-600 liters of hydrochloric acid; During acid precipitation, the temperature is 40-60°C, the time is 30-35 hours, and the stirring speed is 300-400 rpm; Using hydrochloric acid with higher impurity removal efficiency for acid precipitation can improve the acid salt pretreatment efficiency; using hydrochloric acid acid precipitation crystallization can improve the purity of the product compared with nitric acid precipitation; Step 4, adjusting the pH value of the wastewater obtained in step 2 to 4-5 using sodium hydroxide to precipitate the iron in the wastewater, adding sodium sulfide and a chelating agent to remove impurities by chelating precipitation, then filtering, adding sodium hydroxide to the filtrate and adjusting the pH to 10-11, using a stripping tower to concentrate and recover ammonia, and reusing the concentrated ammonia water produced in the ammonia leaching process. The solution after concentration is a sodium chloride solution, which can be evaporated to produce industrial salt or directly discharged; Sodium sulfide and chelating agents are used to remove other heavy metal ions in wastewater; chelating agents can remove iron, copper and other heavy metal ions, and sodium sulfide can remove most heavy metal impurities, and the effect is better when used in combination with chelating agents; The acidic wastewater generated in the production process of ammonium molybdate can be adjusted in pH using sodium hydroxide to remove impurities such as iron and copper; the ammonia generated in the process of treating the acidic wastewater can be recycled, turning waste into treasure; the wastewater is processed through the steps of impurity removal and ammonia removal to form a sodium chloride solution.

[0015] Step 5, leaching the soluble molybdenum metal in the ammonia leached residue by high temperature and high pressure alkaline leaching; The temperature is 150-180°C, the pressure is 2.3-2.8 MPa, and the alkali is specifically sodium hydroxide; Using the alkaline nature of sodium hydroxide solution, industrial molybdenum oxide can be dissolved in the solution to form sodium molybdate solution. The soluble molybdenum metal in the ammonia leached residue is effectively recovered by high-pressure alkaline leaching. Step 6, using ion exchange method to adsorb and analyze the soluble molybdenum metal, the ammonium molybdate solution obtained after analysis can be reused in the production process; the column liquid after adsorption is a sodium chloride solution, which can be evaporated to produce industrial salt or directly discharged.

[0016] The ion exchange resin is specifically a macroporous strongly basic anion resin for adsorbing molybdenum; The column liquid produced by ion exchange is mainly a sodium chloride solution that is harmless to the environment; the molybdenum metal adsorbed by the ion exchange resin is analyzed to form ammonium molybdate, which can be directly used in the production process; The ammonium molybdate production process of the present invention involves the following reaction principles: (1) Wastewater treatment NH4Cl+NaOH=NaCl+ NH3+H2O (2) Alkali leaching M O O4 2- +2 Na + =Na2M O O4 (3) Ion exchange Na2M O O4+2ACl=A2M O O4+ 2NaCl A2M O O4+ NH4.OH= (NH4)2M O O4+2 AOH AOH + HCl = ACl + H2O The green and environmentally friendly ammonium molybdate production process of the present invention utilizes the characteristics of hydrochloric acid molecules to form sodium chloride solutions in both the pickling wastewater and ammonia leaching residue treatment processes, perfectly avoiding the safety and environmental protection problems caused by the environmental protection treatment of traditional processes, and can achieve direct discharge in areas with low emission requirements. In areas with high emission requirements, only evaporation is required to produce industrial salt. The environmental protection treatment cost is low and is simple and reliable. In addition, the metal recovery rate of the production process is higher than that of the traditional process.

[0017] In addition, hydrochloric acid is corrosive to stainless steel equipment, especially under high temperature conditions, the corrosion is more serious, so the pickling, acid precipitation and auxiliary pipelines should use fluorine-lined, rubber-lined equipment, organic materials such as PPH, and corrosion-resistant materials such as titanium. Ammonia overflowed during the production process can be recycled separately.

[0018] Example 1 The green and environmentally friendly ammonium molybdate production process of the present invention is specifically implemented according to the following steps: Step 1, adding acid precipitation mother liquor, hydrochloric acid and industrial molybdenum oxide into a reaction kettle, performing acid washing to wash out impurity ions in the industrial molybdenum oxide; Each ton of finished product produces 5 cubic meters of acid precipitation mother liquor, and the hydrochloric acid consumption is 1.4 tons. The solid-liquid ratio of molybdenum oxide to acid precipitation mother liquor and hydrochloric acid is 1:3; The pickling temperature was 90°C, the pickling time was 1 hour, and the stirring speed was 200 rpm; Step 2, using plate and frame filtration to separate the pickled material into filter cake and wastewater, and subjecting the separated filter cake to an ammonia leaching reaction to generate an ammonia leaching solution; Step 3, mixing the ammonia leaching solution with hydrochloric acid, performing acid precipitation, generating mother liquor and ammonia leaching residue, and the mother liquor enters the acid salt pretreatment process; Each cubic meter of ammonia leaching solution consumes 500 liters of hydrochloric acid; During acid precipitation, the temperature was 40°C, the time was 30 hours, and the stirring speed was 300 rpm; Step 4, adjusting the pH value of the wastewater obtained in step 2 to 4 using sodium hydroxide to precipitate the iron in the wastewater, adding sodium sulfide and a chelating agent to remove impurities by chelating precipitation, then filtering, adding sodium hydroxide to the filtrate and adjusting the pH to 10, using a stripping tower to concentrate and recover ammonia, and reusing the concentrated ammonia water produced in the ammonia leaching process. The solution after concentration is a sodium chloride solution, which can be evaporated to produce industrial salt or directly discharged; Step 5, leaching the soluble molybdenum metal in the ammonia leached residue by high temperature and high pressure alkaline leaching; The temperature is 150°C, the pressure is 2.3 MPa, and the alkali is specifically sodium hydroxide; Step 6, using ion exchange method to adsorb and analyze the soluble molybdenum metal, the ammonium molybdate solution obtained after analysis can be reused in the production process; the column liquid after adsorption is a sodium chloride solution, which can be evaporated to produce industrial salt or directly discharged.

[0019] Example 2 The green and environmentally friendly ammonium molybdate production process of the present invention is as follows: Figure 1 As shown, the specific implementation steps are as follows: Step 1, adding acid precipitation mother liquor, hydrochloric acid and industrial molybdenum oxide into a reaction kettle, performing acid washing to wash out impurity ions in the industrial molybdenum oxide; Each ton of finished product produces 6 cubic meters of acid precipitation mother liquor, and the hydrochloric acid consumption is 1.5 tons. The solid-liquid ratio of molybdenum oxide to acid precipitation mother liquor and hydrochloric acid is 1:3; The pickling temperature was 95°C, the pickling time was 1.5 hours, and the stirring speed was 220 rpm; Step 2, using plate and frame filtration to separate the pickled material into filter cake and wastewater, and subjecting the separated filter cake to an ammonia leaching reaction to generate an ammonia leaching solution; Step 3, mixing the ammonia leaching solution with hydrochloric acid, performing acid precipitation, generating mother liquor and ammonia leaching residue, and the mother liquor enters the acid salt pretreatment process; Each cubic meter of ammonia leaching solution consumes 530 liters of hydrochloric acid; During acid precipitation, the temperature was 50°C, the time was 33 hours, and the stirring speed was 360 rpm; Step 4, adjusting the pH value of the wastewater obtained in step 2 to 5 using sodium hydroxide to precipitate the iron in the wastewater, adding sodium sulfide and a chelating agent to remove impurities by chelating precipitation, then filtering, adding sodium hydroxide to the filtrate and adjusting the pH to 11, using a stripping tower to concentrate and recover ammonia, and reusing the concentrated ammonia water produced in the ammonia leaching process. The solution after concentration is a sodium chloride solution, which can be evaporated to produce industrial salt or directly discharged; Step 5, leaching the soluble molybdenum metal in the ammonia leached residue by high temperature and high pressure alkaline leaching; The temperature is 170°C, the pressure is 2.6 MPa, and the alkali is specifically sodium hydroxide; Step 6, using ion exchange method to adsorb and analyze the soluble molybdenum metal, the ammonium molybdate solution obtained after analysis can be reused in the production process; the column liquid after adsorption is a sodium chloride solution, which can be evaporated to produce industrial salt or directly discharged.

[0020] Example 3 The green and environmentally friendly ammonium molybdate production process of the present invention is specifically implemented according to the following steps: Step 1, adding acid precipitation mother liquor, hydrochloric acid and industrial molybdenum oxide into a reaction kettle, performing acid washing to wash out impurity ions in the industrial molybdenum oxide; Each ton of finished product produces 6 cubic meters of acid precipitation mother liquor, and the hydrochloric acid consumption is 1.5 tons. The solid-liquid ratio of molybdenum oxide to acid precipitation mother liquor and hydrochloric acid is 1:3; The pickling temperature was 100°C, the pickling time was 2 hours, and the stirring speed was 300 rpm; Step 2, using plate and frame filtration to separate the pickled material into filter cake and wastewater, and subjecting the separated filter cake to an ammonia leaching reaction to generate an ammonia leaching solution; Step 3, mixing the ammonia leaching solution with hydrochloric acid, performing acid precipitation, generating mother liquor and ammonia leaching residue, and the mother liquor enters the acid salt pretreatment process; Each cubic meter of ammonia leaching solution consumes 600 liters of hydrochloric acid; During acid precipitation, the temperature was 60°C, the time was 35 hours, and the stirring speed was 400 rpm; Step 4, adjusting the pH value of the wastewater obtained in step 2 to 5 using sodium hydroxide to precipitate the iron in the wastewater, adding sodium sulfide and a chelating agent to remove impurities by chelating precipitation, then filtering, adding sodium hydroxide to the filtrate and adjusting the pH to 11, using a stripping tower to concentrate and recover ammonia, and reusing the concentrated ammonia water produced in the ammonia leaching process. The solution after concentration is a sodium chloride solution, which can be evaporated to produce industrial salt or directly discharged; Step 5, leaching the soluble molybdenum metal in the ammonia leached residue by high temperature and high pressure alkaline leaching; The temperature is 180°C, the pressure is 2.8 MPa, and the alkali is specifically sodium hydroxide; Step 6, using ion exchange method to adsorb and analyze the soluble molybdenum metal, the ammonium molybdate solution obtained after analysis can be reused in the production process; the column liquid after adsorption is a sodium chloride solution, which can be evaporated to produce industrial salt or directly discharged.

[0021] The green and environmentally friendly production process of the present invention is comprehensively compared with two production processes on the market, as shown in Table 1. It can be seen from the table that all the wastewater finally formed by the process of the present invention is only sodium chloride solution, which makes the environmental protection treatment process of the entire production line simple and easy, and greatly reduces the cost. It is more in line with the green and environmentally friendly production method.

[0022] Table 1 Process comparison results

Claims

1. A green and environmentally friendly ammonium molybdate production process, characterized in that: Follow the steps below to implement it: Step 1, adding acid precipitation mother liquor, hydrochloric acid and industrial molybdenum oxide into a reaction kettle for pickling; Step 2, using plate and frame filtration to separate the pickled material into filter cake and wastewater, and subjecting the separated filter cake to an ammonia leaching reaction to generate an ammonia leaching solution; Step 3, mixing the ammonia leaching solution with hydrochloric acid, performing acid precipitation, and generating mother liquor and ammonia leaching residue; Step 4, adjusting the pH of the wastewater obtained in step 2 to 4-5 with sodium hydroxide, precipitating the iron in the wastewater, adding sodium sulfide and a chelating agent, filtering, adding sodium hydroxide to the filtrate to adjust the pH to 10-11, using a stripping tower to concentrate and recover ammonia, and reusing the concentrated ammonia water produced in the ammonia leaching process. The solution after concentration is a sodium chloride solution; Step 5, alkali leaching the ammonia leached residue to leach the soluble molybdenum metal in the residue; Step 6, using ion exchange method to adsorb and analyze the soluble molybdenum metal, the ammonium molybdate solution obtained after analysis, and the column liquid after adsorption is a sodium chloride solution.

2. The green and environmentally friendly ammonium molybdate production process according to claim 1, characterized in that: In the step 1, the pickling temperature is 90-100° C., the pickling time is 1-2 hours, and the stirring speed is 200-300 rpm.

3. The green and environmentally friendly ammonium molybdate production process according to claim 1, characterized in that: In the step 3, during the acid precipitation, the temperature is 40-60° C., the time is 30-35 hours, and the stirring speed is 300-400 rpm.

4. The green and environmentally friendly ammonium molybdate production process according to claim 1, characterized in that: In step 5, during alkali leaching, the temperature is 150-180° C., the pressure is 2.3-2.8 MPa, and the alkali is specifically sodium hydroxide.

5. The green and environmentally friendly ammonium molybdate production process according to claim 1, characterized in that: In step 6, the ion exchange resin is specifically a macroporous strong alkaline anion resin for adsorbing molybdenum.

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