Two-stage solvent extraction and impurity removal method for stone coal sulfuric acid leachate

Abstract

The invention belongs to the technical field of vanadium chemical industry, and particularly relates to a two-stage solvent extraction impurity removal method for stone coal sulfuric acid leachate, which comprises the following steps: in a first impurity removal stage, performing selective reverse extraction on a loaded oil phase obtained by solvent extraction by using hydrochloric acid to obtain a purified hydrochloric acid vanadium-containing solution; in the second vanadium enrichment stage, sulfuric acid is used as a stripping agent, and an enriched vanadium-containing sulfuric acid solution is obtained by adjusting the oil-water ratio of extraction and stripping; and oxidizing and enriching the vanadium-containing sulfuric acid solution by using hydrogen peroxide, adjusting the pH value of a water phase by using ammonia water, and then carrying out water bath roasting to prepare a high-purity V2O5 product. According to the method, the extraction and reverse extraction characteristics of different reverse extraction media and extraction agents are fully utilized, impurity removal and enrichment of solvent extraction are divided into two stages, and the problem of repeated long-cycle extraction impurity removal in a traditional solvent extraction impurity removal technology is successfully solved.

Description

Technical Field

[0001] The invention belongs to the technical field of vanadium chemical industry, and in particular relates to a two-stage solvent extraction and impurity removal method for stone coal sulfuric acid leaching solution. Background Art

[0002] Energy storage technology is a key technology to solve the large-scale storage and dispatch of electricity, and plays an important role in maintaining the stability and flexibility of the power system. At present, various energy storage technologies have their own advantages and disadvantages. Among them, electrochemical energy storage technology has a relatively wider range of applications. The mainstream energy storage system in the market is lithium-ion batteries of the alkali metal family, but it still has certain safety hazards and certain difficulties in material recycling. Compared with lithium-ion batteries, all-vanadium liquid flow batteries store energy through the redox reaction between vanadium in different valence states, and have an ultra-long cycle life. Since there are no other impurity ions involved in the energy storage process, the vanadium element can be effectively recycled and reused. Therefore, all-vanadium liquid flow batteries have great potential in large-scale energy storage applications. At present, the production cost of vanadium electrolyte accounts for more than 50% of the production cost of all-vanadium liquid flow batteries. Vanadium is mainly extracted from the leachate of various vanadium-containing ores (such as stone coal sulfuric acid leachate, etc.). The solvent extraction method can effectively purify and enrich the vanadium element in the leachate. However, since a certain amount of other impurity elements will be extracted during the extraction process, the industry often adopts multi-stage and multi-stage cyclic extraction and stripping methods to reduce the content of impurity elements in the liquid. The cyclic process brings certain difficulties to practical applications, resulting in inevitable vanadium loss and reagent waste. Summary of the invention

[0003] In order to solve the problems existing in the prior art, the main purpose of the present invention is to provide a two-stage solvent extraction and impurity removal method for stone coal sulfuric acid leaching solution.

[0004] To solve the above technical problems, according to one aspect of the present invention, the present invention provides the following technical solutions: A two-stage solvent extraction and impurity removal method for stone coal sulfuric acid leachate comprises the following steps: S1, adding sodium sulfite to the stone coal sulfuric acid leaching solution for pre-reduction treatment, and then adjusting the pH value with ammonia water to prepare an extraction stock solution; extracting the extraction stock solution with an extractant to prepare a loaded oil phase, and then selectively stripping the loaded oil phase with hydrochloric acid to obtain a vanadium-containing hydrochloric acid solution; S2, using ammonia water to adjust the pH value of the vanadium-containing hydrochloric acid solution to prepare a second-stage extraction stock solution; using an extractant to extract the second-stage extraction stock solution to prepare a second-stage loaded oil phase, and then adjusting the oil-water ratio to use sulfuric acid to concentrate and strip the second-stage loaded oil phase to obtain a concentrated vanadium-containing sulfuric acid solution; S3, adding hydrogen peroxide to oxidize the concentrated vanadium-containing sulfuric acid solution and adjusting the pH value with ammonia water, then performing a water bath to obtain ammonium polyvanadate, and calcining the ammonium polyvanadate to obtain vanadium pentoxide.

[0005] As a preferred embodiment of the two-stage solvent extraction impurity removal method for a stone coal sulfuric acid leachate described in the present invention, wherein: in the 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; the hydrochloric acid concentration is 5-8 mol / L.

[0006] As a preferred embodiment of the two-stage solvent extraction and impurity removal method of the stone coal sulfuric acid leachate described in the present invention, wherein: in the steps S1 and S2, the extractant is 15vol% P2O4+1~10vol% TBP (tributyl phosphate)+75~85vol% sulfonated kerosene.

[0007] As a preferred embodiment of the two-stage solvent extraction impurity removal method for a stone coal sulfuric acid leachate described in the present invention, wherein: in the steps S1 and S2, the extraction conditions are: the oil-water ratio is 1:(2~3), the mixing speed is 100~600 r / min, the time is 5~15min, and the extraction level is three to six.

[0008] As a preferred embodiment of the two-stage solvent extraction impurity removal method for a stone coal sulfuric acid leachate described in the present invention, wherein: in the steps S1 and S2, the stripping conditions are: the oil-water ratio is (2~3):1, the mixing speed is 100~600 r / min, the time is 10~20min, and the stripping stage is one to three.

[0009] As a preferred embodiment of the two-stage solvent extraction impurity removal method for a stone coal sulfuric acid leachate described in the present invention, wherein: in the step S2, the concentration of sulfuric acid is 1-2 mol / L, the concentration of ammonia water is 25.0-30.0 wt%, and the pH value is adjusted to 2-3.

[0010] As a preferred embodiment of the two-stage solvent extraction impurity removal method for coal sulfuric acid leachate described in the present invention, wherein: in the step S3, the amount of hydrogen peroxide added is 5-10 g / L, and the hydrogen peroxide oxidation time is 20-40 min.

[0011] As a preferred embodiment of the two-stage solvent extraction impurity removal method for coal sulfuric acid leachate described in the present invention, wherein: in the step S3, the water bath temperature is 90-110° C., and the water bath time is 0.5-2 h.

[0012] As a preferred embodiment of the two-stage solvent extraction impurity removal method for stone coal sulfuric acid leaching solution described in the present invention, wherein: in the step S3, the roasting temperature is 500-600°C and the roasting time is 2-3h.

[0013] As a preferred embodiment of the two-stage solvent extraction method for removing impurities from coal sulfuric acid leachate described in the present invention, wherein: in step S3, the concentration of ammonia water is 25.0-30.0wt%, and the pH value is adjusted to 2-3.

[0014] To solve the above technical problem, according to another aspect of the present invention, the present invention provides the following technical solution: A high-purity V2O5 is prepared by adopting the above-mentioned two-stage solvent extraction and impurity removal method of stone coal sulfuric acid leaching solution, and its purity is ≥99.3%.

[0015] The beneficial effects of the present invention are as follows: The invention provides a two-stage solvent extraction impurity removal method for coal sulfuric acid leaching solution, comprising the steps of treating the coal sulfuric acid leaching solution with sodium sulfite and ammonia water to prepare an extraction stock solution; extracting the extraction stock solution with an extractant to prepare a first-stage loaded oil phase, and then selectively stripping the loaded oil phase with hydrochloric acid to obtain a vanadium-containing hydrochloric acid solution; treating the vanadium-containing hydrochloric acid solution with ammonia water 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, and then adjusting the oil-water ratio to concentrate and strip 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 value with ammonia water, and then performing a water bath to obtain ammonium polyvanadate, and roasting the ammonium polyvanadate to obtain a high-purity V2O5 product. The present invention adopts hydrochloric acid as a selective stripping and impurity removal medium, utilizes the synergistic effect of hydrochloric acid and TBP to achieve a good impurity removal effect, and adopts a two-stage solvent extraction and impurity removal process with a hydrochloric acid vanadium-containing solution as a dividing line, fully utilizing the extraction and stripping characteristics of different stripping media and extractants, and successfully shortening the problem of repeated cyclic extraction and impurity removal in traditional solvent extraction and impurity removal technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0017] Figure 1 It is a schematic diagram of the process of the impurity removal method of the present invention.

[0018] Figure 2 This is the SEM photo of stone coal and sulfuric acid leaching residue.

[0019] Figure 3 This is a comparison chart of the effects of stripping with hydrochloric acid and sulfuric acid in Example 1 of the present invention.

[0020] Figure 4 This is the XRD pattern of vanadium pentoxide prepared in Example 1 of the present invention.

[0021] Figure 5 This is the XRD pattern of the product prepared in Comparative Example 1.

[0022] Figure 6 This is the XRD pattern of the product prepared in Comparative Example 2.

[0023] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0024] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The present invention proposes a two-stage solvent extraction impurity removal method for stone coal sulfuric acid leaching solution. Hydrochloric acid has good selectivity for vanadium and exhibits a synergistic effect with TBP in the extracted oil phase to effectively remove impurities. The present invention has the following advantages: 1) The purification method of the present invention has the advantages of short process and good impurity removal effect, and can be used for rapid impurity removal of vanadium-containing leaching solution.

[0026] 2) The present invention is the first to further refine and separate solvent extraction into two stages, namely, impurity removal and enrichment, based on the synergistic effect between hydrochloric acid and TBP, and a purified vanadyl sulfate solution can be obtained through only two stages of solvent extraction.

[0027] 3) The vanadium pentoxide prepared by the present invention has a higher purity and can be used for the preparation of high-purity vanadium-containing products.

[0028] According to one aspect of the present invention, the present invention provides the following technical solution: like Figure 1 As shown, a two-stage solvent extraction and impurity removal method for stone coal sulfuric acid leachate comprises the following steps: S1, adding sodium sulfite to the stone coal sulfuric acid leaching solution for pre-reduction treatment, and then adjusting the pH value with ammonia water to prepare an extraction stock solution; extracting the extraction stock solution with an extractant to prepare a loaded oil phase, and then selectively stripping the loaded oil phase with hydrochloric acid to obtain a vanadium-containing hydrochloric acid solution; S2, using ammonia water to adjust the pH value of the vanadium-containing hydrochloric acid solution to prepare a second-stage extraction stock solution; using an extractant to extract the second-stage extraction stock solution to prepare a second-stage loaded oil phase, and then adjusting the oil-water ratio to use sulfuric acid to concentrate and strip the second-stage loaded oil phase to obtain a concentrated vanadium-containing sulfuric acid solution; S3, adding hydrogen peroxide to oxidize the concentrated vanadium-containing sulfuric acid solution and adjusting the pH value with ammonia water, then performing a water bath to obtain ammonium polyvanadate, and calcining the ammonium polyvanadate to obtain vanadium pentoxide.

[0029] Preferably, stone coal (its SEM photo is as follows Figure 2 The sulfuric acid leaching solution can be obtained by a common method in the prior art, for example, by crushing the stone coal ore with a grinding machine and screening it with a sieve to prepare the sulfuric acid leaching raw material; then the stone coal is leached with sulfuric acid; finally, the solid-liquid mixed system after leaching is separated into leaching residues by a vacuum filter (the SEM photo of which is shown in FIG. Figure 2 As shown), obtain coal sulfuric acid leaching solution. Further preferably, the stone coal particle size obtained after screening is less than 200 mesh; the stone coal leaching conditions are: sulfuric acid concentration 30wt%, leaching temperature 95°C, leaching time 9h, leaching liquid-solid ratio 2mL / g, mixing speed 400r / min.

[0030] The comparison of the effects of stripping with hydrochloric acid and sulfuric acid is shown in the figure below. Figure 3 As shown, in the stripping process, hydrochloric acid showed a better iron removal effect than sulfuric acid, while sulfuric acid showed a better aluminum removal effect than hydrochloric acid. Therefore, combining the two-stage extraction and impurity removal process can fully utilize the advantages of the two stripping media to remove impurities from the vanadium-containing aqueous phase.

[0031] 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 concentration of ammonia water is 25.0-30.0 wt%, the pH value is adjusted to 2-3; and the concentration of hydrochloric acid is 5-8 mol / L.

[0032] Preferably, in steps S1 and S2, the extractant is 15 vol% P2O4 + 1-10 vol% TBP (tributyl phosphate) + 75-85 vol% sulfonated kerosene.

[0033] Preferably, in steps S1 and S2, the extraction conditions are: oil-water ratio is 1:(2-3), mixing speed is 100-600 r / min, time is 5-15 min, and extraction level is three to six.

[0034] Preferably, in steps S1 and S2, the stripping conditions are: oil-water ratio is (2-3):1, mixing speed is 100-600 r / min, time is 10-20 min, and stripping stage is one to three.

[0035] Preferably, in step S2, the concentration of sulfuric acid is 1-2 mol / L, the concentration of ammonia water is 25.0-30.0 wt%, and the pH value is adjusted to 2-3.

[0036] Preferably, in step S3, the amount of hydrogen peroxide added is 5-10 g / L, and the oxidation time using hydrogen peroxide is 20-40 min.

[0037] Preferably, in step S3, the water bath temperature is 90-110° C., and the water bath time is 0.5-2 h.

[0038] Preferably, in step S3, the calcination temperature is 500-600° C., and the calcination time is 2-3 hours.

[0039] Preferably, in step S3, the concentration of aqueous ammonia is 25.0-30.0 wt %, and the pH value is adjusted to 2-3.

[0040] According to another aspect of the present invention, the present invention provides the following technical solution: A high-purity V2O5 is prepared by adopting the above-mentioned two-stage solvent extraction and impurity removal method of stone coal sulfuric acid leaching solution, and its purity is ≥99.3%.

[0041] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0042] The stone coal ore is crushed by a grinding machine and sieved by a sieve to prepare a sulfuric acid leaching raw material with a particle size of less than 200 mesh, and the pretreated stone coal is leached with sulfuric acid; finally, the solid-liquid mixed system after leaching is separated from the leaching residue by a vacuum filter to obtain the stone coal sulfuric acid leaching solution; the stone coal leaching conditions are: sulfuric acid concentration 30wt%, leaching temperature 95℃, leaching time 9h, leaching liquid-solid ratio 2mL / g, and mixing speed 400r / min.

[0043] Example 1 A two-stage solvent extraction and impurity removal method for stone coal sulfuric acid leachate comprises the following steps: S1. Sodium sulfite is added to the stone coal sulfuric acid leaching solution for pre-reduction treatment, and then ammonia water is used to adjust the pH value to prepare an extraction stock solution; the extraction stock solution is subjected to the first stage impurity removal treatment using an extractant to prepare a loaded oil phase, and then hydrochloric acid is used to selectively strip the loaded oil phase to obtain a vanadium-containing hydrochloric acid solution; the amount of sodium sulfite added is 0.1 g / mL, and the treatment time is 30 min; the ammonia concentration is 28.0 wt%, and the pH value is adjusted to 2.5; the hydrochloric acid concentration is 6 mol / L; the extractant is 15 vol% P2O4+5 vol% TBP (tributyl phosphate)+80 vol% sulfonated kerosene, and the extraction conditions are: oil-water ratio of 1:3, mixing speed of 400 r / min, time of 10 min, and extraction level of three, and the stripping conditions are: oil-water ratio of 3:1, mixing speed of 400 r / min, time of 15 min, and stripping level of one.

[0044] S2. Use ammonia water to adjust the pH value of the vanadium-containing hydrochloric acid solution to prepare a second-stage extraction stock solution; use an extractant to extract the second-stage extraction stock solution to prepare a second-stage loaded oil phase, then adjust the oil-water ratio and use sulfuric acid to concentrate and strip the second-stage loaded oil phase to obtain a concentrated vanadium-containing sulfuric acid solution; the extractant is 15 vol% P2O4+5 vol% TBP (tributyl phosphate)+80 vol% sulfonated kerosene, the extraction conditions are: oil-water ratio of 1:3, mixing speed of 400 r / min, time of 10min, extraction stage of three, stripping conditions are: oil-water ratio of 3:1, mixing speed of 400 r / min, time of 15min, stripping stage of one, sulfuric acid concentration of 1.5 mol / L; ammonia concentration is 28.0wt%, and the pH value is adjusted to 2.5.

[0045] S3, oxidizing the concentrated vanadium-containing sulfuric acid solution with hydrogen peroxide and adjusting the pH value with ammonia water, then performing a water bath to obtain ammonium polyvanadate, and roasting the ammonium polyvanadate to obtain vanadium pentoxide. The amount of hydrogen peroxide added is 8 g / L, the hydrogen peroxide oxidation time is 30 min, the water bath temperature is 95° C., the water bath time is 2 h, the roasting temperature is 550° C., the roasting time is 2 h, the ammonia concentration is 28.0 wt%, and the pH value is adjusted to 2.5.

[0046] The XRD pattern of V2O5 prepared in this example is as follows Figure 4 As shown, its purity is 99.32%. Thanks to the two-stage solvent extraction and impurity removal process, the prepared V2O5 shows obvious characteristic peaks, and no other obvious impurity peaks are detected.

[0047] Comparative Example 1 The difference from Example 1 is that 1.5 mol / L sulfuric acid is used as the stripping medium in step S1.

[0048] The XRD pattern of the product prepared in this comparative example is as follows Figure 5 As shown, no V2O5 characteristics appear. This comparative example uses sulfuric acid with low vanadium selectivity in both the first impurity removal stage and the second vanadium enrichment stage, which cannot achieve the impurity removal and enrichment described in the present invention, and cannot obtain high-purity V2O5.

[0049] Comparative Example 2 The difference from Example 1 is that sulfuric acid is used as the stripping medium in step S1, and a 6-stage solvent extraction / stripping process is used to purify and remove impurities from the leachate.

[0050] The XRD pattern of the product prepared in this comparative example is as follows Figure 6As shown, no V2O5 characteristics appear. This comparative example uses a 6-stage circulating solvent extraction / stripping process to purify the leachate, but in the absence of a high vanadium selective impurity removal agent, due to the low selectivity of sulfuric acid, even if the number of circulating stages is increased, the leachate cannot be deeply purified and impurized, and as the number of circulating stages increases, due to the limitations of the characteristics of the solvent extraction / stripping itself, more vanadium loss will be caused, resulting in a decrease in the vanadium recovery rate, and it is difficult to further increase the ratio of vanadium to impurity elements in the product.

[0051] The present invention adopts hydrochloric acid as a selective stripping and impurity removal medium, utilizes the synergistic effect of hydrochloric acid and TBP to achieve a good impurity removal effect, and adopts a two-stage solvent extraction and impurity removal process with a hydrochloric acid vanadium-containing solution as a dividing line, fully utilizes the extraction and stripping characteristics of different stripping media and extractants, and successfully shortens the problem of repeated cyclic extraction and impurity removal in traditional solvent extraction and impurity removal technology. The above embodiments and comparative examples prove that the two-stage solvent extraction and impurity removal method of stone coal sulfuric acid leachate of the present invention has a good impurity removal effect on the stone coal leachate, and can be used for the production of high-purity vanadium pentoxide.

[0052] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A two-stage solvent extraction impurity removal method for stone coal sulfuric acid leachate, characterized in that: The steps include: S1, adding sodium sulfite to the stone coal sulfuric acid leaching solution for pre-reduction treatment, and then adjusting the pH value with ammonia water to prepare an extraction stock solution; extracting the extraction stock solution with an extractant to prepare a loaded oil phase, and then selectively stripping the loaded oil phase with hydrochloric acid to obtain a vanadium-containing hydrochloric acid solution; S2, using ammonia water to adjust the pH value of the vanadium-containing hydrochloric acid solution to prepare a second-stage extraction stock solution; using an extractant to extract the second-stage extraction stock solution to prepare a second-stage loaded oil phase, and then adjusting the oil-water ratio to use sulfuric acid to concentrate and strip the second-stage loaded oil phase to obtain a concentrated vanadium-containing sulfuric acid solution; S3, adding hydrogen peroxide to oxidize the concentrated vanadium-containing sulfuric acid solution and adjusting the pH value with ammonia water, then performing a water bath to obtain ammonium polyvanadate, and calcining the ammonium polyvanadate to obtain vanadium pentoxide.

2. The two-stage solvent extraction impurity removal method of stone coal sulfuric acid leachate according to claim 1, characterized in that: In the 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 concentration of ammonia water is 25.0-30.0 wt %, and the pH value is adjusted to 2-3; The concentration of hydrochloric acid is 5~8mol / L.

3. The two-stage solvent extraction impurity removal method of stone coal sulfuric acid leachate according to claim 1 is characterized in that: In the steps S1 and S2, the extractant is 15 vol% P2O4+1-10 vol% TBP+75-85 vol% sulfonated kerosene.

4. The two-stage solvent extraction impurity removal method of stone coal sulfuric acid leachate according to claim 1, characterized in that: In the steps S1 and S2, the extraction conditions are: oil-water ratio is 1:(2-3), mixing speed is 100-600 r / min, time is 5-15 min, and extraction level is three to six.

5. The two-stage solvent extraction impurity removal method of stone coal sulfuric acid leachate according to claim 1, characterized in that: In the steps S1 and S2, the stripping conditions are: oil-water ratio is (2-3):1, mixing speed is 100-600 r / min, time is 10-20 min, and stripping stage number is one to three.

6. The two-stage solvent extraction impurity removal method of stone coal sulfuric acid leachate according to claim 1, characterized in that: In step S2, the concentration of sulfuric acid is 1-2 mol / L, the concentration of ammonia water is 25.0-30.0 wt%, and the pH value is adjusted to 2-3.

7. The two-stage solvent extraction impurity removal method of stone coal sulfuric acid leachate according to claim 1, characterized in that: In step S3, the amount of hydrogen peroxide added is 5-10 g / L, and the oxidation time using hydrogen peroxide is 20-40 min.

8. The two-stage solvent extraction impurity removal method of stone coal sulfuric acid leachate according to claim 1, characterized in that: In step S3, the water bath temperature is 90-110° C., and the water bath time is 0.5-2 h; the roasting temperature is 500-600° C., and the roasting time is 2-3 h.

9. The two-stage solvent extraction impurity removal method of stone coal sulfuric acid leachate according to claim 1, characterized in that: In step S3, the concentration of ammonia water is 25.0-30.0 wt %, and the pH value is adjusted to 2-3.

10. A high-purity V2O5, characterized in that: The product is prepared by the two-stage solvent extraction and impurity removal method of the stone coal sulfuric acid leaching solution according to any one of claims 1 to 9, and its purity is ≥99.3%.

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