A method for preparing chromium trioxide and vanadium pentoxide using chromium-vanadium-containing slag

Abstract

The invention discloses a method for preparing chromium trioxide and vanadium pentoxide by using chromium-containing vanadium slag, comprising: calcifying and roasting the chromium-containing vanadium slag to extract vanadium by acid leaching to obtain a vanadium-containing solution, then sodiumizing and roasting the separated solid to extract chromium by water to obtain a chromium-containing solution, adding ammonium carbonate to adjust the pH value and temperature of the vanadium-containing solution to precipitate vanadium, filtering and separating to obtain ammonium metavanadate, and roasting the ammonium metavanadate to obtain vanadium pentoxide; adding a reducing agent to the chromium-containing leaching solution, adjusting the pH to precipitate chromium, filtering to obtain chromium hydroxide precipitate, and precipitating and roasting to obtain chromium trioxide. The vanadium-chromium waste liquid can be recycled. The invention selects different roasting temperatures at the front end to achieve efficient separation of vanadium and chromium, avoids the complex separation process of vanadium and chromium at the back end, shortens the vanadium-chromium separation process, and the purity of the vanadium pentoxide and chromium trioxide obtained respectively is relatively high. At the same time, the vanadium-chromium waste liquid can be returned for recycling, thereby avoiding water pollution and effectively saving production costs.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and more specifically, relates to a method for preparing chromium trioxide and vanadium pentoxide by utilizing chromium-vanadium-containing slag. Background Art

[0002] Both vanadium and chromium are important strategic resources, both have a wide range of applications and prospects, and vanadium and chromium belong to the fourth period transition elements, their chemical properties are similar, and they often exist in minerals in a symbiotic form in nature, making it difficult to separate vanadium and chromium. Vanadium and chromium in vanadium-titanium magnetite enter vanadium slag after pyrometallurgical extraction, and exist in the vanadium slag in the form of spinel. At present, the domestic sodium roasting and calcification roasting processes of vanadium slag are mainly aimed at the extraction and recovery of vanadium, and the chromium element enters the vanadium precipitation wastewater, which is converted into low-value chromium waste after wastewater treatment and stored in slag yards or exported at low prices. The chromium element has not been effectively recycled, its potential economic benefits have not been explored, and the disposal of chromium waste requires a large increase in the cost of "three wastes" treatment.

[0003] Currently, there are few methods for the combined extraction of vanadium and chromium from vanadium slag, and most of these methods are complex, difficult to operate, and costly, and have not been industrially commercialized.

[0004] Patent CN110436523A uses organic acid to adjust the pH value of vanadium-chromium solution, then adds vanadium precipitant, separates solid and liquid, calcines solid to prepare vanadium pentoxide product, adds oxidant and vanadium removal agent to liquid, then introduces a large amount of carbon dioxide to remove impurities, and then concentrates and crystallizes to prepare sodium chromate. This method has a long process flow, consumes a large amount of organic acid, and has high cost. Patent CN104357671A uses sulfuric acid to adjust the pH value of vanadium-chromium solution, then adds melamine as vanadium precipitant, separates solid and liquid, calcines solid to prepare vanadium pentoxide, and removes impurities and evaporates and concentrates liquid to prepare sodium chromate crystals. This method has a short process flow and can effectively recover chromium elements, but it consumes organic melamine and has high cost. Patent CN118929751A uses sodium calcination to obtain clinker from vanadium slag, and then obtains vanadium pentoxide through wet grinding and other processes. The chromium element in the vanadium slag is not utilized, and there are certain environmental risks in the treatment of tailings. Patent CN114394620A directly sodium-calcines high-chrome vanadium slag to obtain clinker, and then soaks the clinker to obtain a high-chrome vanadium solution. The high-chrome vanadium sodium solution is then used to separate vanadium from chromium to obtain vanadium pentoxide and chromium trioxide. After calcination and soaking, chromium and vanadium still exist in the solution at the same time, which may lead to incomplete subsequent separation.

[0005] Comprehensively considering the existing vanadium and chromium resource utilization processes, it has failed to effectively achieve vanadium and chromium separation and product high value. The process of recovering chromium resources is complicated, the product quality is poor, and the amount of wastewater generated is large, making it impossible to achieve effective separation and coupled co-production of vanadium and chromium resources. Summary of the invention

[0006] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0007] In order to achieve these objects and other advantages according to the present invention, a method for preparing chromium trioxide and vanadium pentoxide using chromium-vanadium-containing slag is provided, comprising the following steps:

[0008] Step 1: uniformly mix the chromium-vanadium slag and the calcium-containing compound and roast them to obtain clinker, and leaching the clinker with dilute sulfuric acid to obtain a vanadium-containing solution and chromium-containing slag;

[0009] Step 2, adding an impurity remover to the vanadium-containing solution to obtain a high-purity vanadium solution, and then adding ammonium carbonate to obtain ammonium metavanadate, and calcining to obtain vanadium pentoxide;

[0010] Step 3: roast the chromium-containing slag with oxygen-enriched sodium, then soak it in water to obtain a chromium-containing solution, add a reducing agent to the chromium-containing solution, stir the reaction, and then separate the solid and liquid. The solid is chromium hydroxide, which is calcined and ground to obtain high-purity chromium trioxide. The liquid is a solution containing a reducing substance.

[0011] Preferably, in the step one, the content of vanadium in the chromium-vanadium slag is 10-16wt% as V2O5, and the content of chromium in the chromium-vanadium slag is 6-10wt% as Cr2O3; the calcium-containing compound is one of calcium oxide, calcium hydroxide and calcium carbonate, the amount of the calcium-containing compound accounts for 20-30% of the total mass of the chromium-vanadium slag and the calcium-containing compound, the concentration of dilute sulfuric acid is 50-70%, the solid-liquid ratio during leaching is 1:2-2:1, the leaching time is 0.5-2h, the calcification roasting temperature is 600°C-850°C, and the roasting time is 2-3h.

[0012] Preferably, in step 2, the impurity remover is a mixture of magnesium oxide and aluminum sulfate, the amount of the impurity remover is in the range of 1.2 to 1.3 times the silicon content in the solution, and the mass ratio of magnesium oxide to aluminum sulfate is 1:2.

[0013] Preferably, in step 2, the solution is adjusted to pH 7.5-9.5 with an alkaline or acidic substance, the acidic substance is sulfuric acid, and the alkaline substance is sodium hydroxide, and the mixture is stirred and kept warm at 60° C.-100° C. for 30 min-90 min.

[0014] Preferably, in the step 2, the amount of ammonium carbonate added is: the ammonium addition coefficient is 2.0 to 2.6, the ammonium carbonate is added and stirred for 50 to 70 minutes and then allowed to stand, the solution is layered, the vanadium in the solution is precipitated as ammonium metavanadate, the solid-liquid is separated, the ammonium metavanadate solid is dried and dehydrated, and then calcined at a temperature of 500° C. to 600° C. and kept warm for 120 to 240 minutes to obtain vanadium pentoxide.

[0015] Preferably, in the step three, the oxygen-enriched sodium roasting conditions are roasting at 1100-1300° C., oxygen concentration of 25-35%, roasting for 1-2 h, roasting for 1-2 h, and the sodium salt is sodium carbonate, and the amount of sodium carbonate is 50%-80%.

[0016] Preferably, in step three, the reducing agent is at least one of sodium sulfite, sodium bisulfite, sodium pyrosulfite and sulfurous acid, the molar ratio of S in the reducing agent to Cr in the chromium-containing solution is 1.5 to 4:1, the reduction temperature is 55°C to 80°C, the reduction time is 30min to 70min, and the precipitation time is 30min to 360min.

[0017] Preferably, in the step three, the calcination temperature when calcining chromium hydroxide is 1000-1300° C., the calcination time is 30-240 min, and the calcined product is ground to less than 300 mesh to obtain high-purity chromium trioxide.

[0018] Preferably, in step three, the solution containing the reducing substance obtained can be returned to step three to reduce the chromium-containing solution.

[0019] The present invention has at least the following beneficial effects:

[0020] (1) The method of the present invention uses high-chromium vanadium slag as a raw material, and first extracts vanadium through calcination roasting and acid leaching. During the calcination roasting process, vanadium in the high-chromium vanadium slag is oxidized to pentavalent vanadium, which then enters the solution through acid leaching. Under this condition, chromium does not react and continues to remain in the slag. The chromium and vanadium in the high-chromium vanadium slag can be directly separated into chromium-containing slag and vanadium-containing solution, respectively. Therefore, efficient separation and extraction of vanadium and chromium can be achieved in the calcination roasting stage; and the complexity of subsequent sodium roasting to extract chromium can also be reduced;

[0021] (2) Compared with the prior art of leaching vanadium and chromium into a solution and then separating vanadium and chromium, the present invention selects calcium roasting and acid leaching for vanadium extraction, which has a high vanadium leaching rate, and selects sodium roasting and water leaching for chromium extraction, which is calcium-free roasting and meets environmental protection requirements;

[0022] (3) The vanadium-chromium extraction waste liquid generated in this process can be recycled, avoiding water pollution and effectively saving production costs;

[0023] (4) Compared with the existing method of preparing high-purity vanadium pentoxide from vanadium slag, the vanadium pentoxide prepared by the present invention has a short process, low cost and high efficiency. In addition, chromium trioxide can be obtained while obtaining high-purity vanadium pentoxide, thereby reducing the environmental risk of difficult treatment of chromium in the tailings after vanadium extraction from vanadium slag.

[0024] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a schematic diagram of a method for preparing chromium trioxide and vanadium pentoxide by utilizing chromium-vanadium-containing slag. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0027] Example 1

[0028] A method for preparing chromium trioxide and vanadium pentoxide by using chromium-vanadium-containing slag comprises the following steps:

[0029] Step 1: Take 8 kg of sieved chromium-vanadium slag (the content of vanadium is 10 wt% in terms of V2O5, and the content of chromium is 8 wt% in terms of Cr2O3) and mix them evenly with 2 kg of calcium hydroxide (accounting for 20% of the reaction material), calcine and roast at a temperature of 600°C to obtain clinker, and acid-leach the clinker with 50% dilute sulfuric acid at a solid-liquid ratio of 1:2 to extract vanadium, to obtain a vanadium-containing solution and chromium-containing slag;

[0030] Step 2: Mix magnesium oxide and aluminum sulfate at a mixing mass ratio of 1:2 to obtain an impurity remover, add the impurity remover to the vanadium-containing solution in an amount of 1.2 times the silicon content in the solution, convert silicon, phosphorus and chromium in the vanadium-containing solution into insoluble precipitates and remove them to obtain a high-purity vanadium solution, adjust the pH value of the high-purity vanadium-containing solution with sodium hydroxide or sulfuric acid, adjust the pH value of the solution to 8.5, stir and keep warm at 80°C for 60 minutes, and then add ammonium carbonate at 50°C with an ammonium addition coefficient of 2.0, i.e. 1.6 kg, stir for 60 minutes and then stand, the solution is layered, solid-liquid separation is performed to obtain ammonium metavanadate, dry and dehydrate the ammonium metavanadate, and then calcine at 510°C, keep warm for 150 minutes to obtain vanadium pentoxide, and the vanadium content (in terms of V2O5) is 99.2%;

[0031] Step 3: calcining the chromium-containing slag with sodium enrichment at 1100° C. and an oxygen content of 30% for 1 hour, then immersing in water to obtain a chromium-containing solution, adding sodium sulfite to the chromium-containing solution (the molar ratio of S in the sodium sulfite to Cr in the chromium-containing solution is 2:1), reducing at 60° C. for 60 minutes, then precipitating for 240 minutes, and then separating the solid and the liquid to obtain a chromium hydroxide solid and a solution containing a reducing substance, calcining the chromium hydroxide solid at 1200° C. for 120 minutes, grinding to less than 300 mesh after calcination, and obtaining high-purity chromium trioxide with a chromium content (in terms of Cr2O3) of 99.1%.

[0032] Example 2

[0033] A method for preparing chromium trioxide and vanadium pentoxide by using chromium-vanadium-containing slag comprises the following steps:

[0034] Step 1: Take 7.5 kg of sieved chromium-vanadium slag (the content of vanadium is 11 wt% in terms of V2O5, and the content of chromium is 9 wt% in terms of Cr2O3) and mix them evenly with 2.5 kg of calcium hydroxide (accounting for 25% of the reaction material), calcify and roast at a temperature of 600°C to obtain clinker, and acid-leach the clinker with 50% dilute sulfuric acid at a solid-liquid ratio of 1:2 to extract vanadium, to obtain a vanadium-containing solution and chromium-containing slag;

[0035] Step 2: Mix magnesium oxide and aluminum sulfate at a mixing mass ratio of 1:2 to obtain an impurity remover, add the impurity remover to the vanadium-containing solution in an amount of 1.25 times the silicon content, convert silicon, phosphorus and chromium in the vanadium-containing solution into insoluble precipitates and remove them to obtain a high-purity vanadium solution, adjust the pH value of the high-purity vanadium-containing solution with sodium hydroxide or sulfuric acid, adjust the solution pH to 8.2, stir and keep warm at 60°C for 60 minutes, and then add ammonium carbonate at 55°C with an ammonium addition coefficient of 2.6, i.e. 2.145 kg, stir for 60 minutes and then stand, the solution is layered, solid-liquid separation is performed to obtain ammonium metavanadate, dry and dehydrate the ammonium metavanadate, and then calcine at 520°C, keep warm for 120 minutes to obtain vanadium pentoxide, and the vanadium content (in terms of V2O5) is 99.3%;

[0036] Step 3: calcining the chromium-containing slag with sodium enrichment at 1100° C. and an oxygen content of 30% for 1.5 h, then immersing in water to obtain a chromium-containing solution, adding sodium sulfite to the chromium-containing solution (the molar ratio of S in sodium sulfite to Cr in the chromium-containing solution is 2:1), reducing at 65° C. for 55 min, then precipitating for 240 min, and then solid-liquid separation to obtain chromium hydroxide solid and a solution containing a reducing substance, calcining the chromium hydroxide solid at 1150° C. for 110 min, grinding to less than 300 mesh after calcination, and obtaining high-purity chromium trioxide with a chromium content (in terms of Cr2O3) of 99.3%.

[0037] Example 3

[0038] A method for preparing chromium trioxide and vanadium pentoxide by using chromium-vanadium-containing slag comprises the following steps:

[0039] Step 1: take 7.8 kg of sieved chromium-vanadium slag (the content of vanadium element is 12 wt% as V2O5, and the content of chromium element is 9 wt% as Cr2O3) and 2.2 kg of calcium hydroxide (accounting for 22% of the reaction material) and mix them evenly, calcify and roast them at a temperature of 600°C to obtain clinker, and acid-leach the clinker with 50% dilute sulfuric acid at a solid-liquid ratio of 1:2 to extract vanadium, so as to obtain a vanadium-containing solution and chromium-containing slag;

[0040] Step 2: Mix magnesium oxide and aluminum sulfate at a mixing mass ratio of 1:2 to obtain an impurity remover, add the impurity remover to the vanadium-containing solution in an amount of 1.2 times the silicon content, convert silicon, phosphorus and chromium in the vanadium-containing solution into insoluble precipitates and remove them to obtain a high-purity vanadium solution, adjust the pH value of the high-purity vanadium-containing solution with sodium hydroxide or sulfuric acid, adjust the solution pH to 8.5, stir and keep warm at 80°C for 60 minutes, and then add ammonium carbonate at 50°C with an ammonium addition coefficient of 2.3, i.e. 2.153 kg, stir for 60 minutes and then stand, the solution is layered, solid-liquid separation is performed to obtain ammonium metavanadate, dry and dehydrate the ammonium metavanadate, and then calcine at 550°C, keep warm for 120 minutes to obtain vanadium pentoxide, and the vanadium content (in terms of V2O5) is 98.7%;

[0041] Step 3: calcining the chromium-containing slag at 1100° C. and an oxygen content of 25% for 1 hour, then immersing in water to obtain a chromium-containing solution, adding sodium sulfite to the chromium-containing solution (the molar ratio of S in the sodium sulfite to Cr in the chromium-containing solution is 2:1), reducing at 60° C. for 50 minutes, then precipitating for 240 minutes, and then separating the solid and the liquid to obtain a chromium hydroxide solid and a solution containing a reducing substance, calcining the chromium hydroxide solid at 1100° C. for 120 minutes, and grinding to less than 300 mesh after calcination to obtain high-purity chromium trioxide with a chromium content (in terms of Cr2O3) of 99.0%.

[0042] Example 4

[0043] A method for preparing chromium trioxide and vanadium pentoxide by using chromium-vanadium-containing slag comprises the following steps:

[0044] Step 1: Take 8kg of sieved chromium-vanadium slag (the content of vanadium is 11wt% in terms of V2O5, and the content of chromium is 10wt% in terms of Cr2O3) and mix them evenly with 2kg of calcium hydroxide (accounting for 20% of the material), calcify and roast at a temperature of 600°C to obtain clinker, and acid-leach the clinker with 50% dilute sulfuric acid at a solid-liquid ratio of 2:1 to extract vanadium, to obtain a vanadium-containing solution and chromium-containing slag;

[0045] Step 2: Mix magnesium oxide and aluminum sulfate at a mixing mass ratio of 1:2 to obtain an impurity remover, add the impurity remover to the vanadium-containing solution in an amount of 1.2 times the silicon content, convert silicon, phosphorus and chromium in the vanadium-containing solution into insoluble precipitates and remove them to obtain a high-purity vanadium solution, adjust the pH value of the high-purity vanadium-containing solution with sodium hydroxide or sulfuric acid, adjust the solution pH to 9.0, stir and keep warm at 60°C for 50 minutes, and then add ammonium carbonate at 50°C with an ammonium addition coefficient of 2.5, i.e. 2.2 kg, stir for 70 minutes and then stand, the solution is layered, solid-liquid separation is performed to obtain ammonium metavanadate, the ammonium metavanadate is dried and dehydrated, and then calcined at 500°C, and kept warm for 150 minutes to obtain vanadium pentoxide, with a vanadium content (in terms of V2O5) of 99.3%;

[0046] Step 3: calcining the chromium-containing slag with sodium enrichment at 1100° C. and an oxygen content of 25% for 1 hour, then immersing in water to obtain a chromium-containing solution, adding sodium sulfite to the chromium-containing solution (the molar ratio of S in the sodium sulfite to Cr in the chromium-containing solution is 2:1), reducing at 60° C. for 80 minutes, then precipitating for 240 minutes, and then separating the solid and the liquid to obtain a chromium hydroxide solid and a solution containing a reducing substance, calcining the chromium hydroxide solid at 1150° C. for 120 minutes, grinding to less than 300 mesh after calcination, and obtaining high-purity chromium trioxide with a chromium content (in terms of Cr2O3) of 99.5%.

[0047] Embodiment 4 is a preferred embodiment, so the purity of the obtained vanadium pentoxide and chromium trioxide is the highest.

[0048] Comparative Example 1

[0049] The difference between this comparative example and Example 4 is that in step 1, no calcification roasting is performed, but 8 kg of sieved chromium-vanadium-containing slag (the content of vanadium element as V2O5 is 11wt%, and the content of chromium element as Cr2O3 is 10wt%) is directly subjected to acid leaching with 50% dilute sulfuric acid at a solid-liquid ratio of 2:1 to extract vanadium, to obtain a vanadium-containing solution and chromium-containing slag, and the rest is consistent with Example 4.

[0050] Without calcification roasting in step 1, direct oxygen-enriched roasting in step 3 will cause vanadium and chromium to be contained in the water solution after roasting, which is difficult to separate. The cost of separating vanadium and chromium in the solution is high. The purity of the obtained chromium trioxide product is only 90.3%.

[0051] Comparative Example 2

[0052] The difference between this comparative example and Example 4 is that in step 3, sodium-enriched oxygen roasting is not performed, but the chromium-containing slag obtained in step 2 is directly leached in water to obtain a chromium-containing solution, sodium sulfite is added to the chromium-containing solution (the molar ratio of S in sodium sulfite to Cr in the chromium-containing solution is 2:1), the reduction time is 80 minutes at 60°C, then precipitated for 240 minutes, and then solid-liquid separation is performed to obtain chromium hydroxide solid and a solution containing a reducing substance, the chromium hydroxide solid is calcined at 1150°C for 120 minutes, and after calcination, it is ground to less than 300 mesh to obtain chromium trioxide. The rest is consistent with Example 4.

[0053] Since sodium-enriched oxygen roasting is not used in step three, the amount of chromium leached out during water leaching is reduced, and the chromium content in the resulting tailings is high, posing an environmental risk.

[0054] Comparative Example 3

[0055] According to the patent CN118929751A disclosed in "A method for preparing vanadium pentoxide using high chromium vanadium slag", vanadium pentoxide is prepared using high chromium vanadium slag:

[0056] Step 1: Mix high chromium vanadium slag (chromium content is 10wt% in terms of Cr2O3, vanadium content is 13.5wt% in terms of V2O5, and iron content is 16.5wt% in terms of elemental iron) with sodium carbonate and sodium chloride;

[0057] Step 2: After mixing, the mixture is roasted in a rotary kiln for 280 minutes and then cooled to obtain clinker; the amount of sodium carbonate added is 75% of the mass of the refined vanadium slag, and the amount of sodium chloride added is 25% of the mass of the refined vanadium slag; the roasting treatment includes oxidation roasting, sodium roasting and cooling treatment in sequence; the end point temperature of the oxidation roasting is 650°C, the end point temperature of the sodium roasting is 825°C, and the end point temperature of the cooling treatment is 575°C;

[0058] Step 3: Mix the clinker and water at a solid-liquid ratio of 1:3 for wet grinding for 4 minutes, leaching and filtering, mixing calcium chloride and the filtrate obtained by leaching and filtering for phosphorus removal, standing for 16 hours to obtain a supernatant, and then adding sulfuric acid and adjusting the pH value to 2 at 100°C, and then adding ammonium sulfate for vanadium precipitation to obtain ammonium polyvanadate with a water content of 40wt%; the ammonium sulfate addition coefficient is 1.1; then the ammonium polyvanadate is dried at 325°C, and then calcined at 450°C for deamination, and melted at 950°C to obtain the vanadium pentoxide. The purity of the obtained vanadium pentoxide is 98.32%.

[0059] This comparative example does not utilize the chromium element present in the vanadium slag, and there are certain environmental risks in the treatment of the tailings. In addition, the purity of the vanadium pentoxide finally obtained is lower than the purity of the vanadium pentoxide prepared in the embodiment of the present invention. The method of the present invention rationally utilizes the chromium and vanadium in the vanadium slag as resources through step-by-step roasting, thereby maximizing the utilization of resources and reducing the environmental risks of the tailings treatment.

[0060] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for preparing chromium trioxide and vanadium pentoxide using chromium-vanadium-containing slag, characterized in that: The following steps are involved: Step 1: uniformly mix the chromium-vanadium slag and the calcium-containing compound and roast them to obtain clinker, and leaching the clinker with dilute sulfuric acid to obtain a vanadium-containing solution and chromium-containing slag; Step 2, adding an impurity remover to the vanadium-containing solution to obtain a high-purity vanadium solution, and then adding ammonium carbonate to obtain ammonium metavanadate, and calcining to obtain vanadium pentoxide; Step 3: roast the chromium-containing slag with oxygen-enriched sodium, then soak it in water to obtain a chromium-containing solution, add a reducing agent to the chromium-containing solution, stir the reaction, and then separate the solid and liquid. The solid is chromium hydroxide, which is calcined and ground to obtain high-purity chromium trioxide. The liquid is a solution containing a reducing substance.

2. The method for preparing chromium trioxide and vanadium pentoxide using chromium-vanadium-containing slag according to claim 1, characterized in that: In the step 1, the content of vanadium in the chromium-vanadium slag is 10-16wt% in terms of V2O5, and the content of chromium in the chromium-vanadium slag is 6-10wt% in terms of Cr2O3; the calcium-containing compound is one of calcium oxide, calcium hydroxide, and calcium carbonate, the amount of the calcium-containing compound accounts for 20-30% of the total mass of the chromium-vanadium slag and the calcium-containing compound, the concentration of dilute sulfuric acid is 50-70%, the solid-liquid ratio during leaching is 1:2-2:1, the leaching time is 0.5-2h, the calcification roasting temperature is 600-850°C, and the roasting time is 2-3h.

3. The method for preparing chromium trioxide and vanadium pentoxide using chromium-vanadium-containing slag according to claim 1, characterized in that: In the step 2, the impurity remover is a mixture of magnesium oxide and aluminum sulfate, the dosage of the impurity remover ranges from 1.2 to 1.3 times the silicon content in the solution, and the mass ratio of magnesium oxide to aluminum sulfate is 1:

2.

4. The method for preparing chromium trioxide and vanadium pentoxide using chromium-vanadium-containing slag according to claim 1, characterized in that: In the step 2, the solution pH is adjusted to 7.5-9.5 with an alkaline or acidic substance, the acidic substance is sulfuric acid, and the alkaline substance is sodium hydroxide, and the mixture is stirred and kept warm at a temperature of 60° C. to 100° C. for 30 min to 90 min.

5. The method for preparing chromium trioxide and vanadium pentoxide using chromium-vanadium-containing slag according to claim 1, characterized in that: In the step 2, the amount of ammonium carbonate added is: the ammonium addition coefficient is 2.0 to 2.6, the ammonium carbonate is added and stirred for 50 to 70 minutes and then allowed to stand, the solution is layered, the vanadium in the solution is precipitated as ammonium metavanadate, the solid-liquid separation is performed, the ammonium metavanadate solid is dried and dehydrated, and then calcined at a temperature of 500 to 600° C. and kept warm for 120 to 240 minutes to obtain vanadium pentoxide.

6. The method for preparing chromium trioxide and vanadium pentoxide using chromium-vanadium-containing slag according to claim 1, characterized in that: In the step 3, the oxygen-enriched sodium calcination conditions are 1100-1300° C., an oxygen concentration of 25-35%, and calcination for 1-2 hours.

7. The method for preparing chromium trioxide and vanadium pentoxide by using chromium-vanadium-containing slag according to claim 1, characterized in that: In the step three, the reducing agent is at least one of sodium sulfite, sodium bisulfite, sodium pyrosulfite, and sulfurous acid, the molar ratio of S in the reducing agent to Cr in the chromium-containing solution is 1.5 to 4:1, the reduction temperature is 55° C. to 80° C., the reduction time is 30 min to 70 min, and the precipitation time is 30 min to 360 min.

8. The method for preparing chromium trioxide and vanadium pentoxide using chromium-vanadium-containing slag according to claim 1, characterized in that: In the step 3, the calcination temperature of chromium hydroxide is 1000-1300° C., the calcination time is 30-240 min, and the calcined product is ground to less than 300 meshes to obtain high-purity chromium trioxide.

9. The method for preparing chromium trioxide and vanadium pentoxide by using chromium-vanadium-containing slag according to claim 1, characterized in that: In the step three, the solution containing the reducing substance obtained can be returned to the step three to reduce the chromium-containing solution.

Images