Selective separation and resource utilization method of chromium in sodium vanadium solution

Abstract

The invention discloses a selective separation and resource utilization method of chromium in a sodium vanadium solution, which comprises the following steps: S1, measuring a predetermined volume of sodium vanadium solution, and heating to a predetermined temperature; s2, a preset amount of divalent manganese salt is added into the sodium vanadium solution, so that hexavalent chromium is subjected to a reduction reaction; s3, after the reaction is finished, carrying out solid-liquid separation and washing to obtain chromium and vanadium removed liquid and precipitates; s4, vanadium precipitation and calcination are conducted on the chromium and vanadium removal liquid, and a vanadium oxide product is obtained; and calcining the precipitate at high temperature to obtain the chromium-manganese oxide. According to the method, the sodium vanadium solution is used as a raw material, the divalent manganese salt is used as a reducing agent, hexavalent chromium is reduced into trivalent chromium, the trivalent chromium generates chromium hydroxide precipitate under the alkaline condition, vanadium is not reduced and is reserved in the solution, and efficient separation of vanadium and chromium is achieved; the dechromed vanadium liquid is subjected to vanadium precipitation and calcination, and a vanadium oxide product is obtained; after the precipitate is subjected to high-temperature calcination, chromium-manganese oxide is obtained and can be used for preparing chromium-manganese alloy, and resource utilization is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of vanadium-chromium separation, and in particular to a method for selectively separating and resourcefully utilizing chromium in sodium vanadium liquid. Background Art

[0002] my country is rich in vanadium-titanium magnetite resources, but the V2O5 content in the raw ore is generally low (<1.0%). Usually, vanadium slag is obtained by iron concentrate blast furnace ironmaking-converter vanadium extraction process. Among the many processes for vanadium slag extraction, sodium vanadium extraction is still the mainstream process for vanadium oxide production, and its production capacity accounts for about 70% of the industry. Its main steps are vanadium slag roasting with sodium salt-water leaching to remove impurities-ammonium salt precipitation of vanadium, and finally obtain V2O5 products. Due to the symbiotic relationship between vanadium and chromium elements in vanadium-titanium magnetite, and the properties of vanadium and chromium are very similar, there is a certain content of chromium in the sodium vanadium solution (c(V)=25~45g / L, c(V)=1~5g / L). In the subsequent vanadium precipitation process, whether it is weakly alkaline ammonium salt precipitation or acidic ammonium salt precipitation, the obtained ammonium metavanadate or ammonium polyvanadate contains a part of the impurity chromium, which limits the improvement of the purity of the vanadium oxide product. In recent years, with the rapid development of all-vanadium redox flow batteries (VRFB), higher quality requirements have been put forward for low-chromium vanadium oxide products. Selective removal of chromium from sodium vanadium solution to obtain low-chromium vanadium solution is one of the important ways to prepare low-chromium vanadium oxide, and it is also an important link in achieving vanadium-chromium separation.

[0003] For example, the Chinese patent application number 201710249005.1 mentions a method for separating and recovering vanadium and chromium, which specifically includes using calcium chloride or barium chloride as a precipitation reagent to co-precipitate vanadium and chromium, and then undergoing alkaline leaching of vanadium and acid leaching of chromium to produce vanadium and chromium products respectively; The document "Separation of Vanadium and Chromium in Alkaline Solutions and Preparation of Their Products" mentions that alkaline vanadium-chromium solution is used as raw material, and hydrolysis vanadium precipitation technology is adopted to make vanadium form a vanadium-containing filter cake, and chromium remains in the solution. The vanadium-containing filter cake is dissolved in alkali, precipitated with ammonium salt, and calcined to obtain a V2O5 product. The chromium solution is then subjected to processes such as iron salt vanadium removal, sodium sulfite reduction, alkali precipitation, and calcination to obtain a Cr2O3 product.

[0004] The above processes can all achieve the separation and recovery of vanadium and chromium, but the consumption of acid and alkali is large and the process flow is long.

[0005] For example, the Chinese patent application number 201810660661.5 mentions a method for extracting and separating chromium from an alkaline vanadium-chromium solution, which specifically includes using ionic liquids including trihexyltetradecylphosphonium chloride, tributyl phosphate, and diphenyl sulfone as extractants, mixing them with the alkaline vanadium-chromium solution for extraction to achieve selective extraction of chromium. The extractant of this method can be recycled and is low in cost, but the introduction of phosphorus will have a certain impact on subsequent processes.

[0006] For example, the Chinese patent application number 201610239290.4 mentions a method for separating and recovering vanadium and chromium from a vanadium-chromium solution, the main steps of which include: (1) adding a reducing agent to a vanadium-chromium solution at a pH of 8 to 14 and a temperature of 20 to 100°C to reduce pentavalent vanadium and hexavalent chromium to tetravalent vanadium and trivalent chromium; (2) forming a chromium hydroxide precipitate from the trivalent chromium in situ, filtering to obtain a chromium hydroxide filter cake and a vanadium-containing filtrate; (3) using the chromium hydroxide filter cake to prepare chromium trioxide; (4) using the vanadium-containing filtrate to prepare hydrated vanadium dioxide, vanadium oxysulfate or vanadium pentoxide. In this patent, vanadium and chromium are completely reduced, and the reducing agent is added at 1.1 to 2 times the theoretical amount of the pentavalent vanadium and hexavalent chromium in the vanadium-chromium solution to reduce them to tetravalent vanadium and trivalent chromium, respectively, which is a relatively large amount.

[0007] The vanadium-chromium separation technology of sodium vanadium liquid in the above method has technical difficulties such as long process flow and high production cost, which makes it difficult to realize industrial application.

[0008] In view of this, the existing technology should be improved. Summary of the invention

[0009] The main purpose of the present invention is to provide a method for selectively separating chromium from sodium vanadium liquid and recycling it as a resource. The sodium vanadium liquid is used as a raw material, a divalent manganese salt is used as a reducing agent, hexavalent chromium is reduced to trivalent chromium, the trivalent chromium generates chromium hydroxide precipitation under alkaline conditions, vanadium is not reduced and remains in the solution, and efficient separation of vanadium and chromium is achieved; the vanadium liquid after chromium removal is subjected to vanadium precipitation and calcination to obtain a vanadium oxide product; the precipitate is calcined at high temperature to obtain chromium-manganese oxide, which can be used to prepare chromium-manganese alloy and realize resource utilization.

[0010] According to one aspect of the present invention, a method for selectively separating and recycling chromium from sodium vanadium solution is provided, which comprises the following steps: S1, measuring a predetermined volume of sodium vanadium solution and heating it to a predetermined temperature; S2, adding a predetermined amount of divalent manganese salt to the sodium vanadium solution to cause a reduction reaction of hexavalent chromium; S3, after the reaction is completed, solid-liquid separation and washing are performed to obtain a dechromized vanadium liquid and a precipitate; S4. The vanadium oxide product is obtained by precipitating and calcining the dechromized vanadium liquid; the precipitate is calcined at high temperature to obtain chromium manganese oxide.

[0011] According to one embodiment of the present invention, the pH value of the sodium vanadium solution is 10.0-12.0.

[0012] According to an embodiment of the present invention, the predetermined temperature is 60-90°C.

[0013] According to one embodiment of the present invention, the divalent manganese salt includes at least one of manganese chloride and manganese sulfate.

[0014] According to one embodiment of the present invention, the amount of divalent manganese salt added is 1.0 to 1.4 times the theoretical value of hexavalent chromium being reduced to trivalent chromium.

[0015] According to one embodiment of the present invention, the vanadium precipitation includes at least one of weakly alkaline ammonium salt vanadium precipitation and acidic ammonium salt vanadium precipitation.

[0016] According to one embodiment of the present invention, the reaction parameters of weakly alkaline ammonium salt precipitation of vanadium are: the mass ratio of ammonium salt to vanadium in solution is 2.0-3.0, the reaction pH is 9.0-10.0, the reaction temperature is 5-15°C, and the reaction time is 30-90 min.

[0017] According to one embodiment of the present invention, the reaction parameters of acidic ammonium salt precipitation of vanadium are: the mass ratio of ammonium salt to vanadium in solution is 1.0-2.0, the reaction pH is 2.0-2.5, the reaction temperature is 90-100°C, and the reaction time is 30-90 min.

[0018] According to one embodiment of the present invention, the reaction temperature for calcination after vanadium precipitation in the dechromized vanadium solution is 500-600° C., and the reaction time is 120-240 min.

[0019] According to one embodiment of the present invention, the reaction temperature of the high-temperature calcination of the precipitate is 600-900° C., and the reaction time is 60-180 min.

[0020] In a method for selectively separating and recycling chromium from sodium vanadium liquid according to an embodiment of the present invention, sodium vanadium liquid is used as a raw material, and a divalent manganese salt is used as a reducing agent to reduce hexavalent chromium to trivalent chromium. The trivalent chromium generates chromium hydroxide precipitate under alkaline conditions, and the vanadium is not reduced and remains in the solution, thereby realizing efficient separation of vanadium and chromium; the vanadium liquid after dechromization is subjected to vanadium precipitation and calcination to obtain a vanadium oxide product; the precipitate is calcined at high temperature to obtain chromium-manganese oxide, which can be used to prepare chromium-manganese alloy to realize resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings required for use in the embodiment will be briefly introduced below. Obviously, the drawings described below are only some implementation cases of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A process flow chart of a method for selectively separating and recycling chromium from sodium vanadium liquid according to an exemplary embodiment of the present invention is shown; Figure 2A V-H2O system E-pH diagram showing a method for selective separation and resource utilization of chromium in sodium vanadium solution according to an exemplary embodiment of the present invention; Figure 3 A Cr-H2O system E-pH diagram showing a method for selective separation and resource utilization of chromium in sodium vanadium solution according to an exemplary embodiment of the present invention; Figure 4 A schematic diagram showing the Gibbs free energy of alkaline reduction of hexavalent chromium by divalent manganese in a method for selective separation and resource utilization of chromium in sodium vanadium liquid according to an exemplary embodiment of the present invention is shown. DETAILED DESCRIPTION

[0023] The detailed description of the following embodiments is used to exemplify the principles of the present invention, but cannot be used to limit the scope of the present invention. The present invention can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0024] The present invention provides these embodiments to make this disclosure thorough and complete, and fully express the scope of the present invention to those skilled in the art. It should be noted that unless otherwise specifically stated, the relative arrangement of the parts and steps, the composition of materials, numerical expressions and numerical values ​​set forth in these embodiments should be interpreted as being merely exemplary, rather than as limiting.

[0025] It should be noted that, in the description of the present invention, unless otherwise specified, the meaning of "multiple" is greater than or equal to two; the terms "upper", "lower", "left", "right", "inner", "outer", etc., indicating the orientation or positional relationship, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0026] It should also be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. When a specific device is described as being located between a first device and a second device, there may or may not be an intermediate device between the specific device and the first device or the second device.

[0027] All terms used in the present invention have the same meanings as those understood by those of ordinary skill in the art to which the present disclosure belongs, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries, for example, should be interpreted as having meanings consistent with their meanings in the context of the relevant technology, and should not be interpreted in an idealized or extremely formal sense, unless explicitly defined herein.

[0028] Technologies, methods, and apparatus known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, these technologies, methods, and apparatus should be considered part of the specification.

[0029] like Figure 1 As shown, the present invention provides a method for selective separation and resource utilization of chromium in sodium vanadium liquid, which comprises the following steps: S1, measuring a predetermined volume of sodium vanadium solution and heating it to a predetermined temperature; S2, adding a predetermined amount of divalent manganese salt to the sodium vanadium solution to cause a reduction reaction of hexavalent chromium; S3, after the reaction is completed, solid-liquid separation and washing are performed to obtain a dechromized vanadium liquid and a precipitate; S4. The vanadium oxide product is obtained by precipitating and calcining the dechromized vanadium liquid; the precipitate is calcined at high temperature to obtain chromium manganese oxide.

[0030] In the method for selective separation and resource utilization of chromium in sodium vanadium liquid according to an embodiment of the present invention, sodium vanadium liquid is used as a raw material, and a divalent manganese salt is used as a reducing agent to reduce hexavalent chromium to trivalent chromium. The trivalent chromium generates chromium hydroxide precipitate under alkaline conditions, and the vanadium is not reduced and remains in the solution, thereby realizing efficient separation of vanadium and chromium; the vanadium liquid after dechromization is subjected to vanadium precipitation and calcination to obtain a vanadium oxide product; the precipitate is calcined at high temperature to obtain chromium-manganese oxide, which can be used to prepare chromium-manganese alloy to realize resource utilization.

[0031] In some specific embodiments, the pH value of the sodium vanadium solution is 10.0-12.0.

[0032] Based on the above embodiment, the predetermined temperature is 60-90°C.

[0033] In some specific embodiments, the divalent manganese salt includes at least one of manganese chloride and manganese sulfate. The divalent manganese salt is preferably manganese sulfate.

[0034] Based on the above embodiments, the amount of divalent manganese salt added is 1.0 to 1.4 times the theoretical value of hexavalent chromium being reduced to trivalent chromium. At this time, compared with the added theoretical value, the concentration of the reducing agent in the reaction system is relatively high, which increases the probability of effective collision between reactants in the reaction system.

[0035] In some specific embodiments, the vanadium precipitation includes at least one of weakly alkaline ammonium salt vanadium precipitation and acidic ammonium salt vanadium precipitation.

[0036] Under weakly alkaline conditions, ammonium salts and vanadium mainly form ammonium metavanadate precipitation. This precipitation method is relatively selective for vanadium because many other impurity metal ions (such as iron, aluminum, manganese, etc.) are not easy to form similar precipitation within this pH range. The ammonium metavanadate precipitation particles generated by weakly alkaline ammonium salt precipitation of vanadium are relatively large, which is easier to operate in subsequent separation processes such as filtration and washing. Larger precipitation particles are not easy to clog the pores of filter paper or filter cloth, which can make the filtration process smoother and reduce the filtration time.

[0037] Under acidic conditions, the existence form of vanadium is conducive to combining with ammonium ions to form precipitation, and ammonium salts and vanadium can quickly form ammonium polyvanadate precipitation. Acidic ammonium salt precipitation of vanadium has strong adaptability to the concentration of vanadium in the solution, and can effectively precipitate both high-concentration and low-concentration vanadium solutions. For some complex solutions with low vanadium content, such as industrial waste slag leachate, acidic ammonium salt precipitation of vanadium can achieve vanadium precipitation and recovery by properly adjusting the reaction conditions (such as ammonium salt dosage, acidity, etc.).

[0038] Based on the above examples, the reaction parameters for precipitation of vanadium with weakly alkaline ammonium salt are: the mass ratio of ammonium salt to vanadium in solution is 2.0-3.0, the reaction pH is 9.0-10.0, the reaction temperature is 5-15°C, and the reaction time is 30-90 min.

[0039] In some specific embodiments, the reaction parameters of acidic ammonium salt precipitation of vanadium are: the mass ratio of ammonium salt to vanadium in solution is 1.0-2.0, the reaction pH is 2.0-2.5, the reaction temperature is 90-100° C., and the reaction time is 30-90 min.

[0040] The mass ratio of ammonium salt to vanadium in solution is also called the ammonium addition coefficient.

[0041] Based on the above examples, the reaction temperature for calcination after vanadium precipitation in the dechromized vanadium solution is 500-600° C., and the reaction time is 120-240 min.

[0042] Based on the above examples, the reaction temperature of the high-temperature calcination of the precipitate is 600-900° C., and the reaction time is 60-180 min.

[0043] A specific application of the present application includes: first, pumping a certain volume and concentration of sodium vanadium liquid into a precipitation tank, heating it to 60-90°C, adding manganese sulfate of 1.0-1.4 times the theoretical value of hexavalent chromium being reduced to trivalent chromium, and stirring the reaction for 30-90 minutes; secondly, filtering and washing the slurry after the reaction; then, subjecting the obtained dechromized liquid to vanadium precipitation (weakly alkaline ammonium salt precipitation or acidic ammonium salt precipitation) and calcination, and using it to prepare a high-purity vanadium oxide product; finally, calcining the obtained manganese-chromium precipitate, and using it to smelt manganese-chromium alloy.

[0044] like Figure 2-3 As shown in the figure, the pH value of sodium vanadium solution is usually 10.0~12.0. According to the E-pH diagram of V / Cr-H2O system, it can be determined that the existence forms of V(V), V(IV), Cr(VI) and Cr(III) in alkaline solution are HV2O7 3- 、HV2O5 - 、CrO4 2- , Cr(OH)3, among which only Cr(OH)3 is in the form of precipitation, indicating that alkaline reduction precipitation can be used to effectively separate vanadium and chromium from the solution.

[0045] Based on the chemical reaction formula and thermodynamic data of the reduction of V(V) and Cr(VI) within this pH range (see equation 1 and equation 2), it can be calculated that when the pH is 10.0-12.0, φ (CrO4 2- / Cr(OH)3) values ​​are greater than φ (HV2O7 3- / HV2O5 - ) (see Table 1 for specific calculation results), which shows that CrO4 2- The oxidizing property is stronger than HV2O7 3- , namely CrO4 2- Relative to HV2O7 3- Therefore, under alkaline conditions, the chromium in the solution can be preferentially reduced and precipitated by using a suitable reducing agent, thereby achieving vanadium-chromium separation.

[0046] (Formula 1) (Formula 2) MnO2+2H2O+2e=Mn(OH)2+2OH - φ =1.23-0.02958lga(Mn(OH)2)-0.11832pH (Formula 3) Table 1 Theoretical calculation values ​​of electrode potential in the pH range of 10.0~12.0

[0047] According to the redox reaction of divalent manganese salt under alkaline conditions (Formula 3) and φ (Mn 4+ / Mn(OH)2) (see Table 1), it is not difficult to see that divalent manganese salts can achieve CrO4 in alkaline vanadium liquid 2- The selective reduction of Cr(OH)3 and the formation of HV2O7 3- If it is not reduced by divalent manganese salt, it will continue to remain in the solution. In addition, the excess divalent manganese will also co-precipitate with chromium hydroxide in the alkaline solution, so no new impurities will be introduced into the solution system. The main reactions involved in the entire vanadium-chromium separation process are shown in Formula 4 and Formula 5.

[0048] Mn 2+ +2OH - =Mn(OH)2↓(Formula 4) 3Mn(OH)2↓+2CrO4 2- +4H + =3MnO2↓+ 2Cr(OH)3↓+2H2O (Formula 5) 3×(Formula 4)+(Formula 5) is: 3Mn 2+ +2CrO4 2- +2OH - +2H2O=3MnO2↓+ 2Cr(OH)3↓(Formula 6) like Figure 4 As shown, the Gibbs free energy of formula 6 is calculated using thermodynamic software HSC 6.0 to obtain the △GT curve of the reaction. It can be seen that when divalent manganese salt is used as a reducing agent, △G is less than 0 in the conventional temperature range of 0~100℃, and the reaction can proceed spontaneously, indicating that it is thermodynamically feasible to separate vanadium and chromium from alkaline vanadium liquid. Based on theoretical analysis, the present invention proposes a patented technology for separating vanadium and chromium from alkaline vanadium liquid using divalent manganese salt, and also provides examples for demonstration.

[0049] The present application is described below through specific embodiments.

[0050] Example 1 500 mL of alkaline vanadium solution (typical composition of vanadium solution is shown in Table 2), pH value was adjusted to 11.0, heated to 70 °C, 5.04 g of manganese sulfate (1.2 times the theoretical value of hexavalent chromium being reduced to trivalent chromium) was added, and stirred for 30 min. After the reaction was completed, the slurry was filtered and washed to obtain a dechromized solution (constant volume 500 mL, c(V) = 33.78 g / L, c(Cr) = 0.023 g / L), with a chromium removal rate of 98.81%, a V loss of 3.82%, and a vanadium-chromium separation efficiency of 97. 34%; the chromium-removed liquid was subjected to weak alkaline ammonium salt vanadium precipitation (pH 9.0, addition of 50.67 g of ammonium sulfate (ammonium addition coefficient 3.0), vanadium precipitation temperature 5°C, time 30 min) to obtain ammonium metavanadate, which was calcined at 500°C for 240 min to obtain 29.15 g of V2O5 product (V2O5 content 99.63%, Cr content 0.003%); the chromium-removed slag was calcined at 600°C for 180 min to obtain 2.05 g of chromium-manganese oxide (Cr content 42.50%, Mn content 21.87%).

[0051] Example 2 800 mL of alkaline vanadium solution was measured, the pH value was adjusted to 11.5, heated to 80°C, 7.40 g of manganese sulfate was added, which was 1.1 times the theoretical value of hexavalent chromium being reduced to trivalent chromium, and stirred for 70 minutes; after the reaction, the slurry was filtered and washed to obtain a dechromized liquid (constant volume 800 mL, c(V)=33.60 g / L, c(Cr)=0.018 g / L), with a chromium removal rate of 99.07%, a V loss of 4.33%, and a vanadium-chromium separation efficiency of 96.57%; dechromization The latter liquid was subjected to weak alkaline ammonium salt precipitation (pH 10.0, addition of 53.76 g of ammonium sulfate (ammonium addition coefficient 2.0), precipitation temperature 15°C, time 90 min) to obtain ammonium metavanadate, which was calcined at 600°C for 120 min to obtain 45.95 g of V2O5 product (V2O5 content 99.77%, Cr content 0.002%); the chromium-removing slag was calcined at 900°C for 60 min to obtain 3.35 g of chromium manganese oxide (Cr content 42.87%, Mn content 22.01%).

[0052] Example 3 1000mL of alkaline vanadium solution was measured, the pH value was adjusted to 12.0, heated to 60°C, 8.41g of manganese sulfate (1.0 times the theoretical value of hexavalent chromium being reduced to trivalent chromium) was added, and the reaction was stirred for 90 minutes. After the reaction was completed, the slurry was filtered and washed to obtain a dechromed liquid (constant volume 1000mL, c(V)=33.38g / L, c(Cr)=0.010g / L), with a chromium removal rate of 99.99%, a V loss of 3.45%, and a vanadium-chromium separation efficiency of 96.56%. The post-chromium liquid was subjected to acidic ammonium salt vanadium precipitation (pH 2.0, addition of 33.38 g of ammonium sulfate (ammonium addition coefficient 1.0), precipitation temperature 100°C, time 30 min) to obtain ammonium polyvanadate, which was calcined at 500°C for 240 min to obtain 59.67 g of V2O5 product (V2O5 content 99.83%, Cr content 0.001%); the chromium-removing slag was calcined at 800°C for 120 min to obtain 4.25 g of chromium manganese oxide (Cr content 43.05%, Mn content 21.72%).

[0053] Example 4 200 mL of alkaline vanadium solution was measured, the pH value was adjusted to 10.0, heated to 90°C, 2.35 g of manganese sulfate was added, which was 1.4 times the theoretical value of hexavalent chromium being reduced to trivalent chromium, and stirred for reaction for 50 minutes; after the reaction was completed, the slurry was filtered and washed to obtain a dechromed liquid (constant volume 200 mL, c(V)=33.82 g / L, c(Cr)=0.012 g / L), with a chromium removal rate of 99.38%, a V loss of 3.30%, and a vanadium-chromium separation efficiency of 96.90%; dechroming The latter liquid was subjected to acidic ammonium salt vanadium precipitation (pH 2.5, addition of 13.53 g of ammonium sulfate (ammonium addition coefficient 2.0), precipitation temperature 90°C, time 90 min) to obtain ammonium polyvanadate, which was calcined at 550°C for 180 min to obtain 11.85 g of V2O5 product (V2O5 content 99.80%, Cr content 0.001%); the chromium-removing slag was calcined at 700°C for 150 min to obtain 0.75 g of chromium-manganese oxide (Cr content 42.87%, Mn content 21.79%).

[0054] Table 2 Typical composition of sodium vanadium solution / g·L -1

[0055] After the implementation of the present invention, at least the following beneficial effects are achieved: (1) Small amount of reducing agent is used and the cost is low; (2) During the reduction process, no other impurities are introduced, which will not affect the quality of subsequent vanadium products; (3) High vanadium and chromium separation efficiency; (4) The sediment can be easily recycled.

[0056] The above are exemplary embodiments disclosed in the present invention. The order disclosed in the above embodiments of the present invention is for description only and does not represent the advantages and disadvantages of the embodiments. However, it should be noted that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope disclosed in the embodiments of the present invention (including the claims) is limited to these examples. Various changes and modifications may be made without departing from the scope defined in the claims. The functions, steps and / or actions of the method claims according to the disclosed embodiments described herein do not need to be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or required in individual form, they may also be understood as multiple unless explicitly limited to the singular.

[0057] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A method for selective separation and resource utilization of chromium in sodium vanadium solution, characterized in that: The following steps are involved: S1, measuring a predetermined volume of sodium vanadium solution and heating it to a predetermined temperature; S2, adding a predetermined amount of divalent manganese salt to the sodium vanadium solution to cause a reduction reaction of hexavalent chromium; S3, after the reaction is completed, solid-liquid separation and washing are performed to obtain a dechromized vanadium liquid and a precipitate; S4, the dechromized vanadium liquid is subjected to vanadium precipitation and calcination to obtain a vanadium oxide product; the precipitate is subjected to high-temperature calcination to obtain chromium-manganese oxide.

2. The method for selective separation and resource utilization of chromium in sodium vanadium liquid according to claim 1, characterized in that: The pH value of the sodium vanadium solution is 10.0-12.

0.

3. The method for selective separation and resource utilization of chromium in sodium vanadium liquid according to claim 1, characterized in that: The predetermined temperature is 60-90°C.

4. The method for selective separation and resource utilization of chromium in sodium vanadium liquid according to claim 1, characterized in that: The divalent manganese salt includes at least one of manganese chloride and manganese sulfate.

5. The method for selective separation and resource utilization of chromium in sodium vanadium liquid according to claim 1, characterized in that: The amount of the divalent manganese salt added is 1.0 to 1.4 times the theoretical value of the hexavalent chromium being reduced to trivalent chromium.

6. The method for selective separation and resource utilization of chromium in sodium vanadium liquid according to claim 1, characterized in that: The vanadium precipitation includes at least one of weakly alkaline ammonium salt vanadium precipitation and acidic ammonium salt vanadium precipitation.

7. The method for selective separation and resource utilization of chromium in sodium vanadium liquid according to claim 6, characterized in that: The reaction parameters of the weakly alkaline ammonium salt precipitation of vanadium are: the mass ratio of ammonium salt to vanadium in the solution is 2.0-3.0, the reaction pH value is 9.0-10.0, the reaction temperature is 5-15° C., and the reaction time is 30-90 min.

8. The method for selective separation and resource utilization of chromium in sodium vanadium liquid according to claim 6, characterized in that: The reaction parameters of the acidic ammonium salt precipitation of vanadium are: the mass ratio of ammonium salt to vanadium in the solution is 1.0-2.0, the reaction pH value is 2.0-2.5, the reaction temperature is 90-100° C., and the reaction time is 30-90 min.

9. The method for selective separation and resource utilization of chromium in sodium vanadium liquid according to claim 1, characterized in that: The reaction temperature of calcining after vanadium precipitation in the dechromized vanadium solution is 500-600° C., and the reaction time is 120-240 min.

10. The method for selective separation and resource utilization of chromium in sodium vanadium liquid according to claim 1, characterized in that: The reaction temperature of the high-temperature calcination of the precipitate is 600-900° C., and the reaction time is 60-180 min.

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