Method for resource utilization of vanadium precipitation wastewater

Abstract

The invention belongs to the technical field of industrial wastewater resource utilization, and particularly discloses a vanadium precipitation wastewater resource utilization method which comprises the following steps: hydrogen peroxide oxidation: adding industrial-grade hydrogen peroxide into vanadium precipitation wastewater; adjusting pH: adding liquid caustic soda into the oxidized vanadium precipitation wastewater to obtain vanadium-containing precipitate and filtrate 1; recycling chromium: enabling the filtrate 1 to pass through an ultrafiltration membrane to obtain chromium-containing regenerated liquid and filtrate 2, and performing evaporative crystallization on the chromium-containing regenerated liquid to obtain a sodium dichromate dehydrate product; recycling ammonium sulfate: adjusting the pH value of the filtrate 2 to 4-4.5 by using sulfuric acid, and enabling the filtrate 2 to enter an evaporative crystallization system to obtain a concentrated solution 1, an anhydrous sodium sulfate product and a condensate 1; cooling the concentrated solution 1, and performing solid-liquid separation to obtain a sodium sulfate decahydrate product and a concentrated solution 2; according to the method, after the vanadium precipitation wastewater is treated, vanadium, chromium and ammonia resources in the vanadium precipitation wastewater are fully recycled; according to the method, no wastewater is generated, and a new way is provided for vanadium precipitation wastewater resource utilization.

Description

Technical Field

[0001] The invention relates to the technical field of industrial wastewater resource utilization, in particular to a method for utilizing wastewater resources in the vanadium extraction industry. The method of the invention is suitable for treating wastewater generated by sodium salt roasting and ammonium sulfate salt vanadium precipitation processes. Background Art

[0002] Vanadium is known as the "vitamin" of metals because of its many excellent physical and chemical properties. At present, vanadium is mostly used in steel to increase the strength, toughness and wear resistance of steel. Later, people gradually discovered the excellent improvement effect of vanadium in titanium alloys and applied it to the aerospace field. With the leapfrog development of science and technology, human beings have increasingly higher requirements for vanadium. Its scope covers many fields such as aerospace, chemistry, batteries, pigments, glass, optics, and medicine.

[0003] The main method of extracting vanadium from vanadium ore is the "sodium salt roasting, ammonium sulfate salt vanadium precipitation" process, which produces ammonium polyvanadate (APV) precipitation, and then melts and casts it to produce vanadium pentoxide. The process produces a large amount of vanadium precipitation wastewater in the process of producing ammonium polyvanadate (APV) precipitation. Vanadium precipitation wastewater is a kind of wastewater with high salt, high ammonia nitrogen, low vanadium and low chromium. In recent years, zero discharge of vanadium precipitation wastewater has become the goal of every vanadium enterprise, so the reuse of valuable resources in vanadium precipitation wastewater is imperative.

[0004] The domestic resource utilization treatment methods for vanadium precipitation wastewater are: 1. Recovery of heavy metals. That is, using reducing substances to reduce high-valent chromium and vanadium, and adjusting the pH value to form heavy metal hydroxide precipitation. However, this method cannot effectively separate chromium and vanadium. 2. Ammonia recovery. That is, using multiple evaporation and crystallization methods to obtain anhydrous sodium sulfate and ammonium sulfate respectively. This method has a large evaporation and crystallization processing capacity, high energy consumption, and anhydrous sodium sulfate and sulfuric acid cannot be completely separated.

[0005] The above methods cannot achieve the step-by-step removal of vanadium and chromium, and the treatment cost is too high and the process is too complicated. It is particularly important to recover the valuable resources of vanadium precipitation wastewater in an efficient, short process and low cost manner.

[0006] Therefore, it is necessary to invent a method for utilizing vanadium precipitation wastewater resources to solve the above problems. Summary of the invention

[0007] In view of the above problems, the present invention proposes a method for utilizing vanadium precipitation wastewater resources. The source of the vanadium precipitation wastewater is the wastewater generated by sodium salt roasting and ammonium sulfate salt vanadium precipitation process; the pH value of the vanadium precipitation wastewater is 2-2.5, the total vanadium content is between 50-200 mg / L, the total chromium content is between 100-500 mg / L, the ammonium sulfate content is between 1-4%, and the sodium sulfate content is between 10-15%.

[0008] The present invention achieves its invention object by adopting the following technical scheme.

[0009] A method for utilizing vanadium precipitation wastewater resources, comprising the following steps: Step 1: Hydrogen peroxide oxidation: adding industrial-grade hydrogen peroxide to the vanadium precipitation wastewater to oxidize low-valent chromium and low-valent vanadium in the wastewater; The source of the vanadium precipitation wastewater in step 1 is the wastewater generated by sodium salt roasting and ammonium sulfate salt vanadium precipitation process, and its pH value is 2-2.5; The molar amount of hydrogen peroxide added in step 1 is 1-1.5 times the sum of the molar amounts of total chromium and total vanadium; Step 2: Adjusting the pH to 5-5.5: Adding liquid alkali to the oxidized vanadium precipitation wastewater to adjust the pH to 5-5.5, reacting for 1-2 hours, separating the solid and the liquid, and obtaining a vanadium-containing precipitate and a filtrate 1; In the step 2, an expansion type fine filter is used for precipitation without adding any polymer flocculant; In the step 2, the removal rate of vanadium in the wastewater is 40-60%, and the removal rate of chromium is <1%.

[0010] The vanadium-containing precipitate in step 2 can be returned to the previous sodium salt roasting process and used as a raw material; Step 3: Recovering chromium: filtrate 1 first passes through an ultrafiltration membrane and then enters a chromium ion exchange resin to obtain a chromium-containing regeneration liquid and a filtrate 2. The chromium-containing regeneration liquid is evaporated and crystallized to obtain a sodium dichromate dihydrate product; In the step 3, the analytical solution of the chromium ion exchange resin is a 6% sodium hydroxide solution, and the regeneration solution is a 10% dilute sulfuric acid solution; The chromium removal rate of step three is ≥99%; The mass content of sodium dichromate dihydrate in the sodium dichromate dihydrate product of step three is ≥98%.

[0011] Step 4: Recycling of ammonium sulfate: After adjusting the pH of filtrate 2 to 4-4.5 with sulfuric acid, the filtrate 2 enters the evaporation crystallization system to obtain concentrated solution 1, anhydrous sodium sulfate product, and condensate 1. After the concentrated solution 1 is cooled and crystallized, solid-liquid separation is performed to obtain sodium sulfate decahydrate product and concentrated solution 2. The concentrated solution 2 is recycled to the ammonium sulfate salt vanadium precipitation process, and the condensate 1 can be recycled as process water to replenish the system reagents; The mass content of anhydrous sodium sulfate in the anhydrous sodium sulfate product in step 4 is ≥ 97%; In the step 4, the salt concentration (mass percentage) in the concentrated solution 1 is ≤56%, the ammonium sulfate concentration (mass percentage) in the concentrated solution 1 is between 5-30%, and the pH is 4-5; In the step 4, the density of the concentrated solution 2 is ≤52 g / L, the concentration (mass percentage) of ammonium sulfate in the concentrated solution 2 is between 24-35%, and the pH is 4-5; In the step 4, the ammonia nitrogen in the condensate 1 is less than 100 mg / L, and the evaporation crystallization system operates normally. When the ammonia nitrogen is ≥100 mg / L, the evaporation crystallization process ends immediately and enters the cooling crystallization process.

[0012] The mass content of sodium sulfate decahydrate in the sodium sulfate decahydrate product in step 4 is ≥99%.

[0013] Technical effects and advantages of the present invention: 1. Recovery of vanadium, chromium and ammonia nitrogen resources from vanadium precipitation wastewater The present invention can distribute and recover valuable components such as vanadium, chromium, and ammonium sulfate in vanadium precipitation wastewater. Vanadium is used as a roasting raw material, chromium is produced as potassium dichromate dihydrate, and ammonium sulfate is recycled to the front-end vanadium precipitation stage.

[0014] 2. Achieved effective separation of ammonium sulfate and anhydrous sodium sulfate In the present invention, the high-concentration ammonium sulfate solution is concentrated and then reused in the vanadium precipitation stage, and the anhydrous sodium sulfate product and the sodium sulfate decahydrate product have high purity, and the removal rate of sodium sulfate in wastewater is ≥90%, thereby achieving effective separation of ammonium sulfate and anhydrous sodium sulfate. The evaporation process is simple and the evaporation treatment volume is small.

[0015] 3. Achieve zero discharge of vanadium precipitation wastewater In the present invention, anhydrous sodium sulfate and sodium sulfate decahydrate products are produced in the system as products, high-concentration ammonium sulfate is recycled to the vanadium precipitation process, chromium is produced in the form of sodium dichromate dihydrate product, and condensed water is recycled to the system, truly achieving zero discharge of vanadium precipitation wastewater.

[0016] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 The present invention is a basic flow chart of a method for utilizing vanadium precipitation wastewater resources. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Embodiment 1

[0020] like Figure 1 As shown, this embodiment takes the vanadium precipitation wastewater of a vanadium ore smelter in Hubei as the treatment object, and the vanadium precipitation wastewater is the wastewater produced by the sodium salt roasting and ammonium sulfate salt vanadium precipitation process, and its pH value is 2.1, the total vanadium content is between 124mg / L, the total chromium content is between 421mg / L, the ammonium sulfate content is 3.1%, and the sodium sulfate content is 12.4%; A method for utilizing vanadium precipitation wastewater resources, comprising the following steps: Step 1: Hydrogen peroxide oxidation: Add 1.11 mL of industrial grade 27.5% hydrogen peroxide to the above 1 L of vanadium precipitation wastewater (calculation formula: molar concentration of hydrogen peroxide = 1.463*0.275 / 34 = 0.0118 mol / mL, amount of hydrogen peroxide = 0.0118*1.11 = 0.013 mol, amount of vanadium = 124 / 51 / 1000 = 0.0024 mol / L, amount of chromium = 421 / 52 / 1000 = 0.0081 mol / L, H2O2 / (V+Cr) molar ratio = 0.013 mol / 0.0105 mol = 1.24 / 1) Step 2: Adjust pH value: Liquid alkali was added to adjust the pH to 5.3. After reacting for 2 hours, an expansion fine filter was used to separate the solid and liquid to obtain a vanadium-containing precipitate and a filtrate 1. The vanadium and chromium contents of the filtrate 1 were 55.4 mg / L and 420.7 mg / L, respectively, and the removal rates of vanadium and chromium were 55.3% and 0.06%, respectively. The vanadium-containing precipitate could be returned to the previous sodium salt roasting process as a raw material. Step 3: Chromium recovery: Filtrate 1 first passes through an ultrafiltration membrane and then enters a chromium ion exchange resin to obtain a chromium-containing regeneration liquid (chromium content 10.7 g / L) and filtrate 2 (chromium content 0.7 mg / L). The chromium-containing regeneration liquid is evaporated and crystallized to obtain a sodium dichromate dihydrate product; Step 4: Recycling of ammonium sulfate: After adjusting the pH value of filtrate 2 to 4.0 with sulfuric acid, the filtrate 2 enters the evaporation crystallization system to obtain concentrated solution 1 (salt concentration of 50.9%, ammonium sulfate concentration of 25.2%, sodium sulfate concentration of 25.7%), anhydrous sodium sulfate product (content of 97.8%), and condensate 1 (ammonia nitrogen content of 20.4 mg / L); after the concentrated solution 1 is cooled, solid-liquid separation is performed to obtain sodium sulfate decahydrate product (content of 99.4%) and concentrated solution 2 (ammonium sulfate concentration of 30.7%). The concentrated solution 2 is recycled to the vanadium precipitation stage of the system, and the condensate 1 (density 1.4 g / cm 3 ) can be returned to the system as process water.

[0021] Comparative implementation case 1 - oxidation without hydrogen peroxide In step 2, liquid alkali is added to adjust the pH to 5.3. After reacting for 2 hours, an expansion fine filter is used for solid-liquid separation to obtain a vanadium-containing precipitate and a filtrate 1. The vanadium and chromium contents of the filtrate 1 are 72.8 mg / L and 13.5 mg / L, respectively, and the removal rates of vanadium and chromium are 41.29% and 96.79%, respectively. The vanadium-containing precipitate can be returned to the previous sodium salt roasting process as a raw material, but the vanadium-containing precipitate contains more chromium, which is returned to the system for enrichment, affecting the product quality.

[0022] Comparative implementation case 2-pH value adjusted to 7~8 Liquid alkali was added to adjust the pH to 7.5. After reacting for 2 hours, an expansion fine filter was used for solid-liquid separation to obtain a vanadium-containing precipitate and a filtrate 1. The vanadium and chromium contents of the filtrate 1 were 12.1 mg / L and 360.5 mg / L, respectively, and the removal rates of vanadium and chromium were 90.2% and 14.3%, respectively. The vanadium-containing precipitate could be returned to the previous sodium salt roasting process as a raw material. However, the vanadium-containing precipitate contained a large amount of chromium, which was returned to the system for enrichment, affecting the product quality.

[0023] Comparative Example 3-pH value adjusted to 8.0 After adjusting the pH of filtrate 2 to 8.0 with sulfuric acid, it enters the evaporation crystallization system to obtain condensate 1 (ammonia nitrogen content 568.3 mg / L. The ammonia nitrogen concentration of the condensate is too high and cannot be reused as process water in the system. Embodiment 2

[0024] like Figure 1 As shown, this embodiment takes the vanadium precipitation wastewater of a vanadium ore smelter in Hubei as the treatment object, and the vanadium precipitation wastewater is the wastewater produced by the sodium salt roasting and ammonium sulfate salt vanadium precipitation process, and its pH value is 2.5, the total vanadium content is between 60mg / L, the total chromium content is between 120mg / L, the ammonium sulfate content is 1.5%, and the sodium sulfate content is 10.3%; A method for utilizing vanadium precipitation wastewater resources, comprising the following steps: Step 1: Hydrogen peroxide oxidation: Add 0.43 mL of industrial grade 27.5% hydrogen peroxide to the above 1 L of vanadium precipitation wastewater (calculation formula: molar concentration of hydrogen peroxide = 1.463*0.275 / 34 = 0.0118 mol / mL, amount of hydrogen peroxide = 0.0118*0.43 = 0.0051 mol, amount of vanadium = 60 / 51 / 1000 = 0.0012 mol / L, amount of chromium = 120 / 52 / 1000 = 0.0023 mol / L, H2O2 / (V+Cr) molar ratio = 0.0051 mol / 0.0035 mol = 1.46 / 1) Step 2: Adjust pH value: Liquid alkali was added to adjust the pH to 5.0. After reacting for 2 hours, an expansion fine filter was used to separate the solid and liquid to obtain a vanadium-containing precipitate and a filtrate 1. The vanadium and chromium contents of the filtrate 1 were 35.4 mg / L and 119 mg / L, respectively, and the removal rates of vanadium and chromium were 41% and 0.08%, respectively. The vanadium-containing precipitate could be returned to the previous sodium salt roasting process as a raw material. Step 3: Chromium recovery: Filtrate 1 first passes through an ultrafiltration membrane and then enters a chromium ion exchange resin to obtain a chromium-containing regeneration liquid (chromium content 3.01 g / L) and filtrate 2 (chromium content 0.5 mg / L). The chromium-containing regeneration liquid is evaporated and crystallized to obtain a sodium dichromate dihydrate product; Step 4: Recycling of ammonium sulfate: After adjusting the pH value of filtrate 2 to 4 with sulfuric acid, the filtrate 2 enters the evaporation crystallization system to obtain concentrated solution 1 (salt concentration of 53.2%, ammonium sulfate concentration of 6.9%, sodium sulfate concentration of 46.3%), anhydrous sodium sulfate product (content of 98.6%), and condensate 1 (ammonia nitrogen content of 18.4 mg / L); after cooling, concentrated solution 1 is subjected to solid-liquid separation to obtain sodium sulfate decahydrate product (content of 99.2%) and concentrated solution 2 (ammonium sulfate concentration of 9.2%), and concentrated solution 2 (density 1.2 g / cm 3 ) is reused in the vanadium precipitation stage of the system, and the condensate 1 can be reused in the system as process water.

[0025] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for utilizing vanadium precipitation wastewater resources, the steps of which are as follows: Step 1: Hydrogen peroxide oxidation: adding industrial-grade hydrogen peroxide to the vanadium precipitation wastewater to oxidize low-valent chromium and low-valent vanadium in the wastewater; Step 2: Adjusting the pH: adding liquid alkali to the oxidized vanadium precipitation wastewater to adjust the pH to 5-5.5, reacting for 1-2 hours, separating the solid and the liquid, and obtaining a vanadium-containing precipitate and a filtrate 1; Step 3: Recovering chromium: filtrate 1 first passes through an ultrafiltration membrane and then enters a chromium ion exchange resin to obtain a chromium-containing regeneration liquid and a filtrate 2. The chromium-containing regeneration liquid is evaporated and crystallized to obtain a sodium dichromate dihydrate product; Step 4: Recycling of ammonium sulfate: After adjusting the pH of filtrate 2 to 4-4.5 with sulfuric acid, the filtrate 2 enters an evaporation crystallization system to obtain a concentrated solution 1, an anhydrous sodium sulfate product, and a condensate 1; after the concentrated solution 1 is cooled, solid-liquid separation is performed to obtain a sodium sulfate decahydrate product and a concentrated solution 2, and the concentrated solution 2 is recycled to the vanadium precipitation stage of the system, and the condensate 1 can be recycled to the system as process water.

2. The method for utilizing vanadium precipitation wastewater resources according to claim 1, characterized in that: The source of the vanadium precipitation wastewater in step 1 is the wastewater generated by sodium salt roasting and ammonium sulfate salt vanadium precipitation process; the pH value of the vanadium precipitation wastewater is 2-2.5, the total vanadium content is between 50-200 mg / L, the total chromium content is between 100-500 mg / L, the ammonium sulfate content is between 1-4%, and the sodium sulfate content is between 10-15%.

3. The method for utilizing vanadium precipitation wastewater resources according to claim 1, characterized in that: The molar amount of hydrogen peroxide added in step 1 is 1-1.5 times the total molar amount of total chromium and total vanadium.

4. The method for utilizing vanadium precipitation wastewater resources according to claim 1, characterized in that: In the step 2, the removal rate of vanadium in the wastewater is 40-60%, and the removal rate of chromium is <1%.

5. The method for utilizing vanadium precipitation wastewater resources according to claim 1, characterized in that: In the step 3, the wastewater first passes through an ultrafiltration membrane and then enters a chromium ion exchange resin. The ion exchange resin regeneration liquid is a sodium hydroxide solution, and the chromium removal rate is ≥99%.

6. The method for utilizing vanadium precipitation wastewater resources according to claim 1, characterized in that: The ammonia nitrogen concentration in the condensate 1 in step 4 is <100 mg / L.

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