Method and device for recycling vanadium and chromium in schreyerite vanadium extraction tail end wastewater step by step

Abstract

The invention discloses a method and a device for recycling vanadium and chromium in vanadium-titanium ore vanadium extraction tail end wastewater step by step. The method comprises the following steps of pH regulation and filtration, biological aerobic selective reduction, alkaline elution, precipitation roasting, reduction vanadium precipitation and filtration roasting. In the biological aerobic selective reduction step of the method, hexavalent chromium in the wastewater is reduced by reducing microorganisms under an aerobic condition, and chromium is separated from a liquid phase. Compared with a traditional chemical reduction treatment method, efficient recovery of vanadium in the vanadium extraction tail end wastewater can be achieved, flake vanadium and high-purity chrome green products are obtained, and the additional value of the products is upgraded.

Description

Technical Field

[0001] The invention belongs to the technical field of vanadium-titanium ore smelting, and particularly relates to a method for recovering vanadium and chromium in waste water at the end of vanadium extraction from vanadium-titanium ore in steps. Background Art

[0002] Vanadium is a rare and precious metal widely used in materials, chemical industry, aerospace and other fields. It is mainly extracted from vanadium-titanium ore by smelting. This process often produces vanadium-extraction wastewater with high abundance of chromium and vanadium. While removing vanadium and chromium heavy metals from the vanadium-extraction wastewater, the rare and precious metals of vanadium and chromium can be recovered and recycled. This can not only meet the treatment needs of the wastewater from vanadium-titanium ore extraction, but also use wastewater as a resource for extracting vanadium and chromium, which can improve the economic benefits of the process and the utilization efficiency of resources. At present, the main technology for the resource utilization of vanadium-titanium ore vanadium wastewater is a chemical method based on reduction precipitation. First, vanadium and chromium are reduced to Cr by a reducing agent. 3+ and V 3+ , then add sodium hydroxide solution to adjust the pH to generate chromium hydroxide / vanadium precipitate. Then, basic chromium sulfate is produced through processes such as acid dissolution-impurity removal-filtration-spray drying. During the reduction process, since V(IV) / V(III) and Cr(III) have similar potential ranges, it is difficult for chemical reducing agents to selectively reduce Cr(VI) and V(V), causing vanadium to enter the precipitation together and cannot be separated independently to form products. Therefore, this process cannot effectively extract vanadium. In addition, the chromium product has low purity and low added value. Summary of the invention

[0003] Based on the technical problems raised in the background technology, the purpose of the present invention is to provide a method and device for step-by-step recovery of vanadium and chromium in the terminal wastewater of vanadium-titanium ore extraction, so as to improve the degree of vanadium and chromium resource utilization of the terminal wastewater of vanadium-titanium ore extraction, realize the step-by-step extraction of vanadium and chromium rare and precious metals, and enhance the added value of resource products and resource utilization rate.

[0004] The present invention proposes a method for recovering vanadium and chromium in wastewater from the end of vanadium extraction from vanadium-titanium ore in steps, comprising the following steps:

[0005] (1) adjusting the pH of the wastewater from the vanadium-titanium ore extraction to 6-9 by adding liquid alkali, causing the iron-silicon substances to precipitate and coagulate, and removing the iron-silicon precipitate by solid-liquid separation to obtain iron-silicon-removing wastewater;

[0006] (2) passing the iron-silicon removal wastewater obtained in step (1) into a reaction tank I containing a chromium-reducing bacteria microbial suspension filler and a carbon source, controlling the dissolved oxygen concentration to 0.5 to 4 mg / L by aeration, hydraulic retention for 5 to 10 hours, and performing solid-liquid separation to obtain chromium mud and chromium removal wastewater I;

[0007] (3) passing the chromium-removing wastewater I obtained in step (2) into a reaction tank II containing a chromium-reducing bacteria microbial suspension filler and a carbon source, controlling the dissolved oxygen concentration to 0.5 to 4 mg / L by aeration, hydraulic retention for 5 to 10 hours, and performing solid-liquid separation to obtain chromium mud and chromium-removing wastewater II;

[0008] (4) adding a reducing agent to the chromium removal wastewater II obtained in step (3), and performing solid-liquid separation to obtain vanadium slag;

[0009] (5) washing the vanadium slag obtained in step (4) in water, drying it, and roasting it at 300-600° C. to obtain a high-purity vanadium pentoxide product;

[0010] (6) The chrome mud obtained in steps (2) and (3) is subjected to roasting, alkaline elution and drying to obtain a chrome green product.

[0011] Furthermore, the community composition of the chromium-reducing bacteria described in steps (2) and (3) mainly includes Serratia, Bacillus, Leuconostoc, Panlongea, and Achromobacter.

[0012] Furthermore, the carbon source in steps (2) and (3) is at least one of sodium lactate, sodium acetate, sodium citrate or glucose.

[0013] Furthermore, the stoichiometric ratio of the carbon source to chromium in steps (2) and (3) is 0.8 to 2.2:1.

[0014] Furthermore, the chromium-reducing bacteria microbial suspension filler in steps (2) and (3) is a polyurethane-ethersulfone polymer porous material loaded with chromium-reducing microorganisms to form a film, and the porosity is 10000-17000m 2 / m 3 , the biofilm thickness is 1.5 to 1.8 mm.

[0015] Furthermore, the reducing agent added in step (4) is at least one of sodium pyrosulfite, ascorbic acid or sodium bisulfite.

[0016] Furthermore, in step (4), the molar ratio of the reducing agent to the vanadium substance is 1.1 to 1.5:1.

[0017] Furthermore, in step (5), the calcination temperature of the vanadium slag is 500-800° C., and the calcination time is 30-60 min.

[0018] Furthermore, the calcination temperature of the chromium mud in step (6) is 400-700° C., and the calcination time is 30-60 min; the elution conditions of the chromium mud after calcination in step (6) are: liquid-solid ratio 5-20 mL / g, sodium hydroxide solution concentration 0.2-2 mol / L, elution temperature 10-30° C., and elution times 1-5.

[0019] A device used in the above-mentioned method for step-by-step recovery of vanadium and chromium in the terminal wastewater of vanadium-titanium ore extraction, including a pH regulating device, a reaction tank I, a reaction tank II, a chromium removal wastewater reduction device, a reduced chromium removal wastewater solid-liquid separation device, a vanadium slag elution and drying integrated device, a chromium mud calcining device and a chromium mud elution and drying integrated device.

[0020] In the present invention, the pH is first adjusted to form a hydroxide precipitate of iron, and a coagulation effect is generated, which promotes the sedimentation of silica gel suspended in the liquid phase, which helps to avoid filtration membrane blockage. The removal of iron silicon can prevent iron silicon from precipitating with chromium when the pH rises in the biochemical process, which helps to improve the purity of the chromium product.

[0021] The iron and silicon removal wastewater is treated in a two-step aerobic biochemical reaction tank (steps (2) and (3)), in which chromium is selectively reduced to Cr(III) by microbial enzymatic reaction and forms Cr(OH)3 precipitation, while vanadium is still reduced to VO2 + The formation exists in the solution, realizing the selective step-by-step reduction of chromium and vanadium. Compared with the one-step aerobic biochemical reaction that prolongs the time, by decomposing the reaction process into two steps, the reaction conditions, such as temperature, pH value, substrate concentration, etc., can be better controlled, thereby regulating the reduction performance of chromium in the aerobic biochemical reaction. This step-by-step approach can avoid the incomplete or excessive reaction that may occur in the one-step reaction, and improve the overall treatment efficiency.

[0022] The process of microbial reduction of chromium and separation of vanadium can be enhanced by regulating the dissolved oxygen concentration in the aerobic biochemical process. Since Cr2O3*3H2O exists in the corresponding Eh-pH range, VO2 and V2O3 exist at the same time, that is, chromium and vanadium are both low-valent precipitates. In the narrow Eh-pH range, it is difficult to select a suitable reducing agent to selectively reduce chromium and vanadium for separation. Some microorganisms can selectively reduce chromium under aerobic conditions through enzymatic reactions. Due to Eh Cr(VI) >Eh O2 >Ehv(v), under aerobic conditions, pentavalent vanadium has no reducing effect. Therefore, maintaining a certain dissolved oxygen concentration can not only promote the metabolism and enzyme production of microorganisms, but also maintain the stability of pentavalent vanadium.

[0023] The chromium mud obtained after solid-liquid separation is roasted to decompose the main phase Cr(OH)3 to generate chromium trioxide (chrome green). The small amount of organic matter contained in the chromium mud is burned and decomposed into gas.

[0024] Chromium removal wastewater is reduced by reducing agent, VO2 + After reduction, V(OH)3 and V2O5·xH2O precipitate are generated, and the vanadium form therein is converted into V2O5 by roasting to obtain vanadium pentoxide product.

[0025] When the carbon source is treated in an aerobic biochemical reaction tank, the molecular ratio of carbon source to chromium needs to be regulated, requiring the carbon source / chromium stoichiometric ratio to be 0.8-2.2:3 to ensure that the microorganisms have sufficient electron donors and substrates, maintain high enzyme activity, and fully reduce chromium. When the carbon source / chromium stoichiometric ratio is less than 0.8:1, insufficient electron donors lead to inadequate chromium reduction, reducing the chromium extraction rate and the purity of subsequent vanadium products.

[0026] When roasting chromium slag, the roasting time and temperature need to be regulated. The roasting time and temperature are regulated to increase the decomposition conversion rate of Cr(OH)3 and the decomposition rate of organic matter, and to avoid the presence of chromium hydroxide impurities and organic matter residues in the chrome green product.

[0027] When reducing vanadium in chromium removal wastewater by adding a reducing agent, the molecular ratio of the reducing agent to vanadium needs to be regulated, requiring the reducing agent / vanadium molecular ratio to be 1.1-1.5:1 to ensure that the reducing agent reacts with vanadium and fully reduces vanadium. When the reducing agent / vanadium molecular ratio is 1.1-1.5:1, insufficient reducing agent leads to inadequate vanadium reduction, reducing the vanadium extraction rate.

[0028] When roasting vanadium slag, the roasting time and temperature need to be regulated. The roasting time and temperature are regulated to increase the decomposition conversion rate of V(OH)3 and V2O5·xH2O and avoid the presence of vanadium hydroxide impurities in the vanadium pentoxide product.

[0029] The beneficial effects of this method are as follows:

[0030] By controlling the appropriate ratio of carbon source and reducing agent, roasting temperature and time, the chromium in the wastewater at the end of vanadium-titanium ore extraction can be selectively reduced to chromium hydroxide by biological aerobic method, so that chromium and vanadium can be separated; this is conducive to the step-by-step extraction of vanadium and chromium to form high-value-added and high-purity products.

[0031] In the chromium removal wastewater, vanadium is reduced by a reducing agent and converted into V(OH)3 and V2O5·xH2O precipitation, and vanadium is extracted separately, which is conducive to the subsequent production of high-value-added vanadium pentoxide products. This invention can significantly improve the resource utilization degree and product added value of the terminal wastewater of vanadium-titanium ore extraction, and efficiently extract chromium and vanadium in it step by step to form two high-value-added products.

[0032] In summary, the present invention can improve the resource utilization degree and product added value of the wastewater at the end of vanadium-titanium ore extraction, and efficiently convert vanadium and chromium in the wastewater to form two high value-added products. The step-by-step selective reduction process of chromium and vanadium disclosed in the present invention has the advantages of simple process, low cost, green and high efficiency, and avoids the defects of low product purity and low added value of traditional methods. Considering the huge amount of wastewater at the end of vanadium-titanium ore extraction each year, this invention has broad market application prospects, can generate huge economic benefits, and is conducive to the green and efficient recycling treatment of smelting wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0034] Figure 1 The present invention is a process flow chart of the method for step-by-step recovery of vanadium and chromium from wastewater at the end of vanadium extraction from vanadium-titanium ore.

[0035] Figure 2 The K-edge XANES spectrum and analysis results of chromium in chromium-vanadium products.

[0036] Figure 3 K-edge XANES spectrum and analysis results of vanadium for chrome vanadium products.

[0037] Figure 4 The invention discloses a device for recovering vanadium and chromium in waste water at the end of vanadium extraction from vanadium-titanium ore in steps. DETAILED DESCRIPTION

[0038] The technical solutions 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 only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0039] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of description and simplified description of the present invention, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0040] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or suggesting relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0041] This embodiment provides a method for recovering vanadium and chromium from the wastewater at the end of vanadium-titanium ore extraction in steps, referring to Figure 1 , including the following steps:

[0042] (1) adjusting the pH of the wastewater from the vanadium-titanium ore extraction to 6-9 by adding liquid alkali, causing the iron-silicon substances to precipitate and coagulate, and removing the iron-silicon precipitate by solid-liquid separation to obtain iron-silicon-removing wastewater;

[0043] (2) passing the iron-silicon removal wastewater obtained in step (1) into a reaction tank I containing a chromium-reducing bacteria microbial suspension filler and a carbon source, controlling the dissolved oxygen concentration to 0.5 to 4 mg / L by aeration, hydraulic retention for 5 to 10 hours, and performing solid-liquid separation to obtain chromium mud and chromium removal wastewater I;

[0044] (3) passing the chromium-removing wastewater I obtained in step (2) into a reaction tank II containing a chromium-reducing bacteria microbial suspension filler and a carbon source, controlling the dissolved oxygen concentration to 0.5 to 4 mg / L by aeration, hydraulic retention for 5 to 10 hours, and performing solid-liquid separation to obtain chromium mud and chromium-removing wastewater II;

[0045] (4) adding a reducing agent to the chromium removal wastewater II obtained in step (3), and performing solid-liquid separation to obtain vanadium slag;

[0046] (5) washing the vanadium slag obtained in step (4) in water, drying it, and roasting it at 300-600° C. to obtain a high-purity vanadium pentoxide product;

[0047] (6) The chrome mud obtained in steps (2) and (3) is subjected to roasting, alkaline elution and drying to obtain a chrome green product.

[0048] The community composition of the chromium-reducing bacteria described in steps (2) and (3) mainly includes Serratia, Bacillus, Leuconostoc, Panlongea, and Achromobacter.

[0049] The carbon source in steps (2) and (3) is at least one of sodium lactate, sodium acetate, sodium citrate or glucose.

[0050] The stoichiometric ratio of the carbon source to chromium in steps (2) and (3) is 0.8 to 2.2:1.

[0051] The chromium-reducing bacteria microbial suspension filler in steps (2) and (3) is a polyurethane-ethersulfone polymer porous material loaded with chromium-reducing microorganisms to form a film, and the porosity is 10000-17000m 2 / m 3 , the biofilm thickness is 1.5 to 1.8 mm.

[0052] The reducing agent added in step (4) is at least one of sodium pyrosulfite, ascorbic acid or sodium bisulfite.

[0053] In step (4), the molar ratio of the reducing agent to the vanadium substance is 1.1 to 1.5:1.

[0054] In step (5), the calcination temperature of the vanadium slag is 500-800° C., and the calcination time is 30-60 min.

[0055] The calcination temperature of the chromium mud in step (6) is 400-700° C., and the calcination time is 30-60 min. The elution conditions of the chromium mud after calcination in step (6) are: liquid-solid ratio 5-20 mL / g, sodium hydroxide solution concentration 0.2-2 mol / L, elution temperature 10-30° C., and elution times 1-5.

[0056] Figure 2 and Figure 3 The K-edge XANES spectrum and analysis results of chromium / vanadium of chromium-vanadium products. The carbon source was selected as sodium lactate, the carbon source / chromium molecular ratio was 4:3, the reducing agent was selected as sodium pyrosulfite, the reducing agent and vanadium molecular ratio was 1.3:1, the chromium slag roasting temperature was 700℃, and the roasting time was 40min. The alkaline elution conditions of the chromium slag roasting product were: sodium hydroxide concentration 0.5mol / L, liquid-solid ratio 10mL / g, elution temperature 20℃, and elution times 3 times. The vanadium slag roasting temperature was 500℃ and the roasting time was 50min.

[0057] like Figure 4 As shown, on the other hand, this embodiment provides a device used in the above-mentioned method for stepwise recovery of vanadium and chromium in the terminal wastewater of vanadium-titanium ore extraction, comprising a pH adjusting device 100, a reaction tank I200, a reaction tank II300, a chromium removal wastewater reduction device 400, a reduced chromium removal wastewater solid-liquid separation device 500, a vanadium slag elution and drying integrated device 600, a chromium mud roasting device 700 and a chromium mud elution and drying integrated device 800. The pH adjusting device is used for pH adjustment in step (1), the reaction tank I and the reaction tank II are used for reduction in steps (2) and (3), the chromium removal wastewater reduction device and the reduced chromium removal wastewater solid-liquid separation device are used for the implementation of step (4), the vanadium slag elution and drying integrated device is used for the implementation of step (5), and the chromium mud roasting device and the chromium mud elution and drying integrated device are used for the implementation of step (6).

[0058] In order to highlight the technical problems, technical solutions and advantages to be solved by the present invention, specific embodiments are described in detail below.

[0059] In the embodiments and comparative examples of the present invention, vanadium extraction terminal wastewater from a vanadium-titanium magnetite smelter was selected, and the main chemical composition is shown in Table 1.

[0060] Table 1 Main chemical composition of wastewater from vanadium-titanium ore extraction

[0061]

[0062] Comparative Example 1

[0063] By adding 12g / L of sodium metabisulfite to the wastewater at the end of vanadium-titanium ore extraction, the chromium and vanadium in the liquid phase are reduced, and a chromium-vanadium precipitate is obtained by solid-liquid separation. The obtained chromium-vanadium precipitate is roasted at 900°C for 90 minutes to obtain a crude chrome green product. Under these conditions, the chromium recovery rate is 87.7%, the vanadium recovery rate is 76.4%, the Cr2O3 content in the crude chrome green product is 81.6%, and the V2O5 content is 3.97%. At this time, the purity of the chrome green product is low, and most of the vanadium enters the crude chrome green. It can be seen that direct chemical reduction precipitation cannot extract chromium and vanadium in steps.

[0064] Comparative Example 2

[0065] By adding 8g / L of sodium metabisulfite to the wastewater at the end of vanadium-titanium ore extraction, the chrome and vanadium in the liquid phase are reduced, and a chrome-vanadium precipitate is obtained by solid-liquid separation. The obtained chrome-vanadium precipitate is roasted at 900°C for 90 minutes to obtain a crude chrome green product. Under these conditions, the chromium recovery rate is 78.5%, the vanadium recovery rate is 49.8%, the Cr2O3 content in the crude chrome green product is 86.5%, and the V2O5 content is 5.37%. At this time, the purity of the chrome green product is low, and most of the vanadium enters the crude chrome green. It can be seen that reducing the amount of reducing agent will reduce the chrome-vanadium recovery rate, and chrome-vanadium cannot be extracted step by step.

[0066] Comparative Example 3

[0067] By adding 10g / L of ascorbic acid to the wastewater at the end of vanadium extraction from vanadium-titanium ore, the chromium and vanadium in the liquid phase are reduced, and a chromium-vanadium precipitate is obtained by solid-liquid separation. The obtained chromium-vanadium precipitate is roasted at 900°C for 90 minutes to obtain a crude chrome green product. Under these conditions, the chromium recovery rate is 92.5%, the vanadium recovery rate is 62.4%, the Cr2O3 content in the crude chrome green product is 85.1%, and the V2O5 content is 2.15%. At this time, the purity of the chrome green product is low, and most of the vanadium enters the crude chrome green. It can be seen that adjusting the type of reducing agent cannot extract chromium and vanadium in steps.

[0068] Example 1

[0069] The pH of the wastewater at the end of vanadium extraction from vanadium-titanium ore is adjusted to 8.5 by adding liquid alkali, so that the iron-silicon substances are precipitated and coagulated, and the iron-silicon precipitation is removed by solid-liquid separation to obtain iron-silicon-removed wastewater; the iron-silicon-removed wastewater in step (1) is passed into two-stage reaction tanks containing chromium-reducing bacteria biological suspension fillers and carbon sources, and the hydraulic retention is 8 hours. The carbon source is selected as sodium lactate, and the carbon source / chromium molecular ratio is 2.2:1, and solid-liquid separation is performed to obtain chromium mud and chromium-removed wastewater; the chromium mud is roasted at 700°C for 50 minutes, and the chromium slag roasting product is eluted 3 times with 1.0 mol / L sodium hydroxide concentration and 10 mL / g liquid-solid ratio at 20°C. The reducing agent sodium pyrosulfite is added to the chromium-removed wastewater, and the reducing agent / vanadium molecular ratio is 1.5:1. After solid-liquid separation, the vanadium slag is roasted at 500°C for 40 minutes. Under these conditions, the chromium recovery rate is 99.3%, the Cr2O3 content in the chrome green is 99.7%, the vanadium recovery rate is 96.2%, and the V2O5 content in the vanadium pentoxide product is 94.5%.

[0070] Example 2

[0071] The pH of the wastewater at the end of vanadium extraction from vanadium-titanium ore is adjusted to 8.5 by adding liquid alkali, so that the iron-silicon material is precipitated and coagulated, and the iron-silicon precipitate is removed by solid-liquid separation to obtain iron-silicon-removed wastewater; the iron-silicon-removed wastewater in step (1) is passed into two-stage reaction tanks containing chromium-reducing bacteria biological suspension filler and carbon source, and the hydraulic retention is 8 hours. The carbon source is selected as sodium lactate, and the carbon source / chromium molecular ratio is 1.7:1, and solid-liquid separation is performed to obtain chromium mud and chromium-removed wastewater; the chromium mud is roasted at 700°C for 40 minutes, and the chromium slag roasting product is eluted 4 times with 1.5 mol / L sodium hydroxide concentration and 20 mL / g liquid-solid ratio at 20°C. The reducing agent ascorbic acid is added to the chromium-removed wastewater, and the reducing agent / vanadium molecular ratio is 1.3:1. After solid-liquid separation, the vanadium slag is roasted at 500°C for 40 minutes. Under these conditions, the chromium recovery rate is 98.4%, the Cr2O3 content in the chrome green is 98.2%, the vanadium recovery rate is 89.2%, and the V2O5 content in the vanadium pentoxide product is 90.1%.

[0072] Example 3

[0073] The pH of the wastewater at the end of vanadium extraction from vanadium-titanium ore is adjusted to 8.5 by adding liquid alkali, so that the iron-silicon material is precipitated and coagulated, and the iron-silicon precipitate is removed by solid-liquid separation to obtain iron-silicon-removed wastewater; the iron-silicon-removed wastewater in step (1) is passed into two-stage reaction tanks containing chromium-reducing bacteria biological suspension filler and carbon source, and the hydraulic retention is 8 hours. The carbon source is selected as sodium citrate, and the carbon source / chromium molecular ratio is 1.5:1, and solid-liquid separation is performed to obtain chromium mud and chromium-removed wastewater; the chromium mud is roasted at 600°C for 40 minutes, and the chromium slag roasting product is eluted 4 times with 0.5 mol / L sodium hydroxide concentration and 10 mL / g liquid-solid ratio at 20°C. The reducing agent ascorbic acid is added to the chromium-removed wastewater, and the reducing agent / vanadium molecular ratio is 1.2:1. After solid-liquid separation, the vanadium slag is roasted at 500°C for 40 minutes. Under these conditions, the chromium recovery rate is 95.9%, the Cr2O3 content in the chrome green is 88.2%, the vanadium recovery rate is 83.5%, and the V2O5 content in the vanadium pentoxide product is 90.8%.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for recovering vanadium and chromium from the wastewater at the end of vanadium-titanium ore extraction in steps, It is characterized in that The following steps are involved: (1) adjusting the pH of the wastewater from the vanadium-titanium ore extraction to 6-9 by adding liquid alkali, causing the iron-silicon substances to precipitate and coagulate, and removing the iron-silicon precipitate by solid-liquid separation to obtain iron-silicon-removing wastewater; (2) passing the iron-silicon removal wastewater obtained in step (1) into a reaction tank I containing a chromium-reducing bacteria microbial suspension filler and a carbon source, controlling the dissolved oxygen concentration to 0.5 to 4 mg / L by aeration, hydraulic retention for 5 to 10 hours, and performing solid-liquid separation to obtain chromium mud and chromium removal wastewater I; (3) passing the chromium-removing wastewater I obtained in step (2) into a reaction tank II containing a chromium-reducing bacteria microbial suspension filler and a carbon source, controlling the dissolved oxygen concentration to 0.5 to 4 mg / L by aeration, hydraulic retention for 5 to 10 hours, and performing solid-liquid separation to obtain chromium mud and chromium-removing wastewater II; (4) adding a reducing agent to the chromium removal wastewater II obtained in step (3), and performing solid-liquid separation to obtain vanadium slag; (5) washing the vanadium slag obtained in step (4) in water, drying it, and roasting it at 300-600° C. to obtain a high-purity vanadium pentoxide product; (6) The chrome mud obtained in steps (2) and (3) is subjected to roasting, alkaline elution and drying to obtain a chrome green product.

2. According to the method described in claim 1, a method for recovering vanadium and chromium from the wastewater at the end of vanadium extraction from vanadium-titanium ore in steps, It is characterized in that The community composition of the chromium-reducing bacteria described in steps (2) and (3) mainly includes Serratia, Bacillus, Leuconostoc, Panlongea, and Achromobacter.

3. According to the method for recovering vanadium and chromium from the wastewater at the end of vanadium extraction from vanadium-titanium ore in steps as described in claim 1, It is characterized in that The carbon source in steps (2) and (3) is at least one of sodium lactate, sodium acetate, sodium citrate or glucose.

4. A method for recovering vanadium and chromium from wastewater at the end of vanadium extraction from vanadium-titanium ore in steps according to claim 1, 2 or 3, It is characterized in that The stoichiometric ratio of the carbon source to chromium in steps (2) and (3) is 0.8 to 2.2:

1.

5. According to the method for recovering vanadium and chromium from the wastewater at the end of vanadium extraction from vanadium-titanium ore in steps as described in claim 1, It is characterized in that The chromium-reducing bacteria microbial suspension filler in steps (2) and (3) is a polyurethane-ethersulfone polymer porous material loaded with chromium-reducing microorganisms to form a film, and the porosity is 10000-17000m 2 / m 3 , the biofilm thickness is 1.5 to 1.8 mm.

6. A method for recovering vanadium and chromium from wastewater at the end of vanadium extraction from vanadium-titanium ore in steps according to claim 1, It is characterized in that The reducing agent added in step (4) is at least one of sodium pyrosulfite, ascorbic acid or sodium bisulfite.

7. A method for recovering vanadium and chromium from wastewater at the end of vanadium extraction from vanadium-titanium ore in steps according to claim 1 or 6, It is characterized in that In step (4), the molar ratio of the reducing agent to the vanadium substance is 1.1 to 1.5:

1.

8. According to the method for recovering vanadium and chromium from the wastewater at the end of vanadium extraction from vanadium-titanium ore in steps as described in claim 1, It is characterized in that In step (5), the calcination temperature of the vanadium slag is 500-800° C., and the calcination time is 30-60 min.

9. A method for recovering vanadium and chromium from wastewater at the end of vanadium extraction from vanadium-titanium ore in steps according to claim 1, It is characterized in that The calcination temperature of the chromium mud in step (6) is 400-700° C., and the calcination time is 30-60 min. The elution conditions of the chromium mud after calcination in step (6) are: liquid-solid ratio 5-20 mL / g, sodium hydroxide solution concentration 0.2-2 mol / L, elution temperature 10-30° C., and elution times 1-5.

10. A device used in the method for stepwise recovery of vanadium and chromium from wastewater at the end of vanadium-titanium ore extraction as claimed in claim 1, Features: It includes a pH regulating device, a reaction tank I, a reaction tank II, a chromium removal wastewater reduction device, a reduced chromium removal wastewater solid-liquid separation device, a vanadium slag eluting and drying integrated device, a chromium mud roasting device and a chromium mud eluting and drying integrated device.

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