Two-stage solvent extraction method for removing impurities from stone coal sulfuric acid leaching solution

Abstract

This invention belongs to the field of vanadium chemical technology, specifically a two-stage solvent extraction method for removing impurities from sulfuric acid leaching solutions of coal shale. In the first impurity removal stage, hydrochloric acid is used to selectively back-extract the loaded oil phase obtained through solvent extraction to obtain a purified vanadium-containing hydrochloric acid solution. In the second vanadium enrichment stage, sulfuric acid is used as the back-extraction agent, and the oil-water ratio of extraction and back-extraction is adjusted to obtain an enriched vanadium-containing sulfuric acid solution. Hydrogen peroxide is used to oxidize and enrich the vanadium-containing sulfuric acid solution, and the pH value of the aqueous phase is adjusted with ammonia. Then, water bath calcination is performed to prepare a high-purity V₂O₅ product. This invention fully utilizes the extraction and back-extraction characteristics of different back-extraction media and extractants, separating the impurity removal and enrichment stages of solvent extraction into two stages, successfully solving the problem of repeated long-cycle extraction and impurity removal inherent in traditional solvent extraction techniques.

Description

Technical Field

[0001] This invention belongs to the field of vanadium chemical technology, specifically a two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal shale. Background Technology

[0002] Energy storage technology is a key technology for solving large-scale power storage and dispatch, playing a vital role in maintaining the stability and flexibility of the power system. Currently, various energy storage technologies have their own advantages and disadvantages. Among them, electrochemical energy storage technology has a wider range of applications. The mainstream energy storage system on the market is currently the alkali metal group lithium-ion battery, but it still has certain safety hazards and difficulties in material recycling. Compared to lithium-ion batteries, vanadium redox flow batteries store energy through redox reactions between vanadium in different valence states, exhibiting an ultra-long cycle life. Because no other impurity ions participate in the energy storage process, the vanadium element can be effectively recovered and reused. Therefore, vanadium redox flow batteries have great potential for large-scale energy storage applications. Currently, the production cost of vanadium electrolyte accounts for more than 50% of the total production cost of vanadium redox flow batteries. Vanadium is mainly extracted from the leaching solutions of various vanadium-containing ores (such as sulfuric acid leaching solutions from coal shale). Solvent extraction can effectively purify and enrich vanadium in the leaching solution. However, since a certain amount of other impurity elements are extracted during the extraction process, multi-stage and multi-level circulating extraction and back-extraction are often adopted in industry to reduce the content of impurity elements in the liquid. The circulating process brings certain difficulties to practical applications, resulting in unavoidable vanadium loss and reagent waste. Summary of the Invention

[0003] To address the problems existing in the prior art, the main objective of this invention is to propose a two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal shale.

[0004] To address the aforementioned technical problems, according to one aspect of the present invention, the present invention provides the following technical solution:

[0005] A two-stage solvent extraction method for removing impurities from sulfuric acid leachate of coal shale includes the following steps:

[0006] S1. Sodium sulfite was added to the sulfuric acid leachate of coal for pre-reduction treatment, and then the pH value was adjusted with ammonia to prepare the original extract. The original extract was extracted with an extractant to prepare a loaded oil phase, and then the loaded oil phase was selectively back-extracted with hydrochloric acid to obtain a vanadium-containing hydrochloric acid solution.

[0007] S2. The pH of the vanadium-containing hydrochloric acid solution was adjusted with ammonia to prepare the second-stage extraction stock solution; the second-stage extraction stock solution was extracted with an extractant to prepare a second-stage loaded oil phase; then the oil-water ratio was adjusted and the second-stage loaded oil phase was concentrated and back-extracted with sulfuric acid to obtain a concentrated vanadium-containing sulfuric acid solution.

[0008] S3. Add hydrogen peroxide to oxidize the concentrated vanadium-containing sulfuric acid solution and adjust the pH value with ammonia water. Then, perform a water bath to obtain ammonium polyvanadate. Roast the ammonium polyvanadate to obtain vanadium pentoxide.

[0009] As a preferred embodiment of the two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal shale according to the present invention, in step S1, the amount of sodium sulfite added is 0.08~0.12g / mL, the pre-reduction treatment time is 20~40min; the concentration of ammonia is 25.0~30.0wt%, the pH value is adjusted to 2~3; and the concentration of hydrochloric acid is 5~8mol / L.

[0010] As a preferred embodiment of the two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal according to the present invention, in steps S1 and S2, the extractant is 15 vol% P2O4 + 1~10 vol% TBP (tributyl phosphate) + 75~85 vol% sulfonated kerosene.

[0011] As a preferred embodiment of the two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal shale according to the present invention, in steps S1 and S2, the extraction conditions are: oil-water ratio of 1:(2~3), mixing speed of 100~600 r / min, time of 5~15 min, and extraction stages of three to six.

[0012] As a preferred embodiment of the two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal shale according to the present invention, in steps S1 and S2, the back-extraction conditions are: oil-water ratio of (2~3):1, mixing speed of 100~600 r / min, time of 10~20 min, and back-extraction stages of one to three.

[0013] As a preferred embodiment of the two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal according to the present invention, in step S2, the sulfuric acid concentration is 1~2 mol / L, the ammonia concentration is 25.0~30.0 wt%, and the pH value is adjusted to 2~3.

[0014] As a preferred embodiment of the two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal according to the present invention, in step S3, the amount of hydrogen peroxide added is 5~10g / L, and the oxidation time with hydrogen peroxide is 20~40min.

[0015] As a preferred embodiment of the two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal according to the present invention, in step S3, the water bath temperature is 90~110℃ and the water bath time is 0.5~2h.

[0016] As a preferred embodiment of the two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal according to the present invention, in step S3, the calcination temperature is 500~600℃ and the calcination time is 2~3h.

[0017] As a preferred embodiment of the two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal according to the present invention, in step S3, the ammonia concentration is 25.0~30.0 wt%, and the pH value is adjusted to 2~3.

[0018] To solve the above-mentioned technical problems, according to another aspect of the present invention, the present invention provides the following technical solution:

[0019] A high-purity V2O5 was prepared by the above-mentioned two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal, and its purity was ≥99.3%.

[0020] The beneficial effects of this invention are as follows:

[0021] This invention proposes a two-stage solvent extraction method for removing impurities from sulfuric acid leachate of coal shale. The method involves treating the sulfuric acid leachate of coal shale with sodium sulfite and ammonia to prepare an extraction stock solution; extracting the stock solution with an extractant to prepare a first-stage loaded oil phase, followed by selective back-extraction of the loaded oil phase with hydrochloric acid to obtain a vanadium-containing hydrochloric acid solution; treating the vanadium-containing hydrochloric acid solution with ammonia to prepare a second-stage extraction stock solution; extracting the second-stage extraction stock solution with an extractant to prepare a second-stage loaded oil phase, then adjusting the oil-to-water ratio and concentrating the second-stage loaded oil phase with sulfuric acid to obtain a concentrated vanadium-containing sulfuric acid solution; oxidizing the concentrated vanadium-containing sulfuric acid solution with hydrogen peroxide and adjusting the pH with ammonia, followed by a water bath to obtain ammonium polyvanadate; and calcining the ammonium polyvanadate to obtain a high-purity V₂O₅ product. This invention uses hydrochloric acid as a selective back-extraction medium to remove impurities. The synergistic effect of hydrochloric acid and TBP can achieve a good impurity removal effect. A two-stage solvent extraction process is adopted with vanadium-containing hydrochloric acid solution as the dividing line. By making full use of the extraction and back-extraction characteristics of different back-extraction media and extractants, the problem of repeated cyclic extraction and impurity removal in traditional solvent extraction technology is successfully shortened. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 This is a schematic flowchart of the impurity removal method of the present invention.

[0024] Figure 2 SEM images of coal shale and sulfuric acid leaching residue.

[0025] Figure 3 This is a comparison chart showing the effects of back-extraction with hydrochloric acid and sulfuric acid in Example 1 of the present invention.

[0026] Figure 4 The image shows the XRD pattern of vanadium pentoxide prepared in Example 1 of this invention.

[0027] Figure 5 The image shows the XRD pattern of the product prepared in Comparative Example 1.

[0028] Figure 6 The image shows the XRD pattern of the product prepared in Comparative Example 2.

[0029] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0030] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] This invention proposes a two-stage solvent extraction method for removing impurities from sulfuric acid leachate of coal shale. Hydrochloric acid exhibits good selectivity for vanadium and shows a synergistic effect with TBP in the extracted oil phase, thus effectively removing impurities. This invention has the following advantages:

[0032] 1) The purification method described in this invention has the advantages of short process and good impurity removal effect, and can be used for rapid impurity removal of vanadium-containing leachate.

[0033] 2) This invention is the first to refine solvent extraction into two stages, namely impurity removal and enrichment, based on the synergistic effect between hydrochloric acid and TBP. Furthermore, purified vanadium oxysulfate solution can be obtained through only two stages of solvent extraction.

[0034] 3) The vanadium pentoxide prepared by this invention has high purity and can be used to prepare high-purity vanadium-containing products.

[0035] According to one aspect of the present invention, the present invention provides the following technical solution:

[0036] like Figure 1 As shown, a two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal shale includes the following steps:

[0037] S1. Sodium sulfite was added to the sulfuric acid leachate of coal for pre-reduction treatment, and then the pH value was adjusted with ammonia to prepare the original extract. The original extract was extracted with an extractant to prepare a loaded oil phase, and then the loaded oil phase was selectively back-extracted with hydrochloric acid to obtain a vanadium-containing hydrochloric acid solution.

[0038] S2. The pH of the vanadium-containing hydrochloric acid solution was adjusted with ammonia to prepare the second-stage extraction stock solution; the second-stage extraction stock solution was extracted with an extractant to prepare a second-stage loaded oil phase; then the oil-water ratio was adjusted and the second-stage loaded oil phase was concentrated and back-extracted with sulfuric acid to obtain a concentrated vanadium-containing sulfuric acid solution.

[0039] S3. Add hydrogen peroxide to oxidize the concentrated vanadium-containing sulfuric acid solution and adjust the pH value with ammonia water. Then, perform a water bath to obtain ammonium polyvanadate. Roast the ammonium polyvanadate to obtain vanadium pentoxide.

[0040] Preferred, coal stone (its SEM image is as follows) Figure 2 (As shown) Sulfuric acid leaching solution can be obtained using common methods in existing technologies. For example, raw coal ore is crushed by a grinding mill and screened to prepare sulfuric acid leaching raw material; then, the coal ore is leached with sulfuric acid; finally, the solid-liquid mixture after leaching is separated into leaching residue by a vacuum filter (its SEM image is shown). Figure 2 As shown), sulfuric acid leachate of coal shale was obtained. Further preferred, the coal shale particle size obtained after sieving is less than 200 mesh; the coal shale leaching conditions are: sulfuric acid concentration 30 wt%, leaching temperature 95℃, leaching time 9 h, leachate-to-solid ratio 2 mL / g, and mixing speed 400 r / min.

[0041] A comparison of the effects of back-extraction with hydrochloric acid and sulfuric acid is shown in the figure below. Figure 3 As shown, hydrochloric acid exhibits a better iron removal effect than sulfuric acid during the back-extraction process, while sulfuric acid exhibits a better aluminum removal effect than hydrochloric acid. Therefore, combining the two-stage extraction and impurity removal process can make full use of the advantages of the two back-extraction media to remove impurities from the vanadium-containing aqueous phase.

[0042] Preferably, in step S1, the amount of sodium sulfite added is 0.08~0.12 g / mL, the pre-reduction treatment time is 20~40 min; the ammonia concentration is 25.0~30.0 wt%, the pH value is adjusted to 2~3; and the hydrochloric acid concentration is 5~8 mol / L.

[0043] Preferably, in steps S1 and S2, the extractant is 15 vol% P2O4 + 1~10 vol% TBP (tributyl phosphate) + 75~85 vol% sulfonated kerosene.

[0044] Preferably, in steps S1 and S2, the extraction conditions are: oil-to-water ratio of 1:(2~3), mixing speed of 100~600 r / min, time of 5~15 min, and extraction stages of three to six.

[0045] Preferably, in steps S1 and S2, the back-extraction conditions are: oil-water ratio of (2~3):1, mixing speed of 100~600 r / min, time of 10~20 min, and back-extraction stages of one to three.

[0046] Preferably, in step S2, the sulfuric acid concentration is 1~2 mol / L, the ammonia concentration is 25.0~30.0 wt%, and the pH value is adjusted to 2~3.

[0047] Preferably, in step S3, the amount of hydrogen peroxide added is 5~10g / L, and the oxidation time with hydrogen peroxide is 20~40min.

[0048] Preferably, in step S3, the water bath temperature is 90~110℃ and the water bath time is 0.5~2h.

[0049] Preferably, in step S3, the calcination temperature is 500~600℃ and the calcination time is 2~3h.

[0050] Preferably, in step S3, the ammonia concentration is 25.0~30.0 wt%, and the pH value is adjusted to 2~3.

[0051] According to another aspect of the present invention, the present invention provides the following technical solution:

[0052] A high-purity V2O5 was prepared by the above-mentioned two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal, and its purity was ≥99.3%.

[0053] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0054] The raw coal ore was crushed by a grinding mill and screened to prepare sulfuric acid leaching raw material with a particle size of less than 200 mesh. The pretreated coal ore was then leached with sulfuric acid. Finally, the solid-liquid mixture after leaching was separated from the leaching residue by a vacuum filter to obtain coal ore sulfuric acid leachate. The coal leaching conditions were: sulfuric acid concentration 30wt%, leaching temperature 95℃, leaching time 9h, leachate-to-solid ratio 2mL / g, and mixing speed 400r / min.

[0055] Example 1

[0056] A two-stage solvent extraction method for removing impurities from sulfuric acid leachate of coal shale includes the following steps:

[0057] S1. Sodium sulfite was added to the sulfuric acid leachate of coal shale for pre-reduction treatment, and then the pH value was adjusted with ammonia to prepare the extraction stock solution. The extraction stock solution was subjected to a first-stage impurity removal treatment with an extractant to prepare a loaded oil phase. Then, the loaded oil phase was selectively back-extracted with hydrochloric acid to obtain a vanadium-containing hydrochloric acid solution. The amount of sodium sulfite added was 0.1 g / mL, the treatment time was 30 min, the concentration of ammonia was 28.0 wt%, and the pH value was adjusted to 2.5. The concentration of hydrochloric acid was 6 mol / L. The extractant was 15 vol% P2O4 + 5 vol% TBP (tributyl phosphate) + 80 vol% sulfonated kerosene. The extraction conditions were: oil-water ratio of 1:3, mixing speed of 400 r / min, time of 10 min, and three extraction stages. The back-extraction conditions were: oil-water ratio of 3:1, mixing speed of 400 r / min, time of 15 min, and one back-extraction stage.

[0058] S2. The pH of the vanadium-containing hydrochloric acid solution was adjusted with ammonia to prepare the second-stage extraction stock solution. The second-stage extraction stock solution was then extracted with an extractant to prepare a second-stage loaded oil phase. The oil-water ratio was then adjusted, and the second-stage loaded oil phase was concentrated and back-extracted with sulfuric acid to obtain a concentrated vanadium-containing sulfuric acid solution. The extractant was 15 vol% P2O4 + 5 vol% TBP (tributyl phosphate) + 80 vol% sulfonated kerosene. The extraction conditions were: oil-water ratio of 1:3, mixing speed of 400 r / min, time of 10 min, and three extraction stages. The back-extraction conditions were: oil-water ratio of 3:1, mixing speed of 400 r / min, time of 15 min, one back-extraction stage, sulfuric acid concentration of 1.5 mol / L, ammonia concentration of 28.0 wt%, and pH adjusted to 2.5.

[0059] S3. A concentrated vanadium-containing sulfuric acid solution was oxidized with hydrogen peroxide, and the pH was adjusted with ammonia. Then, an ammonium polyvanadate was obtained by water bath oxidation. The ammonium polyvanadate was then calcined to obtain vanadium pentoxide. The hydrogen peroxide dosage was 8 g / L, the oxidation time was 30 min, the water bath temperature was 95℃, the water bath time was 2 h, the calcination temperature was 550℃, the calcination time was 2 h, the ammonia concentration was 28.0 wt%, and the pH was adjusted to 2.5.

[0060] The XRD pattern of V2O5 prepared in this embodiment is shown below. Figure 4 As shown, its purity is 99.32%. Thanks to the two-stage solvent extraction process for impurity removal, the prepared V2O5 exhibits obvious characteristic peaks, and no other obvious impurity peaks were detected.

[0061] Comparative Example 1

[0062] The difference from Example 1 is that 1.5 mol / L sulfuric acid is used as the back-extraction medium in step S1.

[0063] The XRD pattern of the product prepared in this comparative example is shown below. Figure 5 As shown, no V2O5 characteristics were observed. This comparative example used sulfuric acid, which has low vanadium selectivity, in both the first impurity removal stage and the second vanadium enrichment stage, thus failing to achieve the impurity removal and enrichment described in this invention and failing to obtain high-purity V2O5.

[0064] Comparative Example 2

[0065] The difference from Example 1 is that sulfuric acid is used as the back-extraction medium in step S1, and a 6-stage solvent extraction / back-extraction process is used to purify and remove impurities from the leachate.

[0066] The XRD pattern of the product prepared in this comparative example is shown below. Figure 6 As shown, no V2O5 characteristics were observed. This comparative example used a 6-stage circulating solvent extraction / back-extraction process to purify the leachate. However, in the absence of a high-vanadium-selective impurity removal reagent, due to the low selectivity of sulfuric acid, even increasing the number of circulation stages could not achieve deep purification of the leachate. Furthermore, with the increase in the number of circulation stages, the inherent limitations of solvent extraction / back-extraction resulted in greater vanadium loss, leading to a decrease in vanadium recovery and making it difficult to further increase the proportion of vanadium and impurity elements in the product.

[0067] This invention uses hydrochloric acid as a selective back-extraction medium to remove impurities. The synergistic effect of hydrochloric acid and TBP can achieve a good impurity removal effect. A two-stage solvent extraction impurity removal process is adopted with the vanadium-containing hydrochloric acid solution as the dividing line. By making full use of the extraction and back-extraction characteristics of different back-extraction media and extractants, the problem of repeated cycle extraction and impurity removal in traditional solvent extraction impurity removal technology is successfully shortened. Through the above examples and comparative examples, it is proved that the two-stage solvent extraction impurity removal method of sulfuric acid leaching solution of coal stone of this invention has a good impurity removal effect on coal stone leaching solution and can be used for the production of high-purity vanadium pentoxide.

[0068] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal shale, characterized in that, Includes the following steps: S1. Sodium sulfite was added to the sulfuric acid leachate of coal shale for pre-reduction treatment, and then the pH value was adjusted with ammonia to prepare the extraction stock solution. The extraction stock solution was extracted with an extractant to prepare a loaded oil phase, and then the loaded oil phase was selectively back-extracted with hydrochloric acid to obtain a vanadium-containing hydrochloric acid solution. The extractant was 15 vol% P2O4 + 1~10 vol% TBP + 75~85 vol% sulfonated kerosene; the hydrochloric acid concentration was 5~8 mol / L. S2. The pH of the vanadium-containing hydrochloric acid solution was adjusted with ammonia to prepare the second-stage extraction stock solution; the second-stage extraction stock solution was extracted with an extractant to prepare a second-stage loaded oil phase; then the oil-water ratio was adjusted and the second-stage loaded oil phase was concentrated and back-extracted with sulfuric acid to obtain a concentrated vanadium-containing sulfuric acid solution; the extractant was 15 vol% P2O4 + 1~10 vol% TBP + 75~85 vol% sulfonated kerosene; the sulfuric acid concentration was 1~2 mol / L. S3. Add hydrogen peroxide to oxidize the concentrated vanadium-containing sulfuric acid solution and adjust the pH value with ammonia water. Then, perform a water bath to obtain ammonium polyvanadate. Roast the ammonium polyvanadate to obtain vanadium pentoxide with a purity ≥99.3%. In steps S1 and S2, the back-extraction conditions are: oil-water ratio of (2~3):1, mixing speed of 100~600 r / min, time of 10~20 min, and back-extraction stages of one to three. Hydrochloric acid is used as a selective back-extraction medium to remove impurities. The synergistic effect of hydrochloric acid and TBP is used to achieve a good impurity removal effect. A two-stage solvent extraction process is adopted with the vanadium-containing hydrochloric acid solution as the dividing line. The extraction and back-extraction characteristics of different back-extraction media and extractants are fully utilized. A purified vanadium oxysulfate solution can be obtained by only two stages of solvent extraction.

2. The two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal shale according to claim 1, characterized in that, In step S1, the amount of sodium sulfite added is 0.08~0.12 g / mL, the pre-reduction treatment time is 20~40 min, the ammonia concentration is 25.0~30.0 wt%, and the pH value is adjusted to 2~3.

3. The two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal shale according to claim 1, characterized in that, In steps S1 and S2, the extraction conditions are: oil-to-water ratio of 1:(2~3), mixing speed of 100~600 r / min, time of 5~15 min, and extraction stages of three to six.

4. The two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal shale according to claim 1, characterized in that, In step S2, the ammonia concentration is 25.0~30.0 wt%, and the pH value is adjusted to 2~3.

5. The two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal shale according to claim 1, characterized in that, In step S3, the amount of hydrogen peroxide added is 5~10g / L, and the oxidation time with hydrogen peroxide is 20~40min.

6. The two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal shale according to claim 1, characterized in that, In step S3, the water bath temperature is 90~110℃ and the water bath time is 0.5~2h; the calcination temperature is 500~600℃ and the calcination time is 2~3h.

7. The two-stage solvent extraction method for removing impurities from sulfuric acid leaching solution of coal shale according to claim 1, characterized in that, In step S3, the ammonia concentration is 25.0~30.0 wt%, and the pH value is adjusted to 2~3.

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