Method for Coextracting Scandium from Titanium White Waste Acid and Low-Temperature Chlorination Dust Collection Residue

Abstract

The present invention discloses a method for co-extracting scandium from titanium white waste acid and low-temperature chlorination dust collection slag, which comprises the following steps: leaching the low-temperature chlorination dust collection slag with titanium white waste acid to obtain a leaching solution; adding a mixed solution of HF or NaF and phosphoric acid or phosphate to the leaching solution to remove zirconium, and filtering to obtain a scandium-containing solution; extracting scandium in the scandium-containing solution with a first composite extractant to obtain a first loaded organic phase; then using a strongly oxidizing and strongly alkaline solution to strip the first loaded organic phase to obtain a stripped product enriched in scandium and a stripped organic phase; leaching scandium in the stripped product with dilute acid, filtering to obtain a scandium-rich solution, and extracting scandium in the scandium-rich solution with a second composite extractant to obtain a second loaded organic phase; eluting impurities such as residual titanium, manganese, calcium, zirconium, iron, magnesium, and vanadium in the second loaded organic phase with a mixed solution of hydrogen peroxide-sulfuric acid / hydrochloric acid-phosphoric acid to obtain a third loaded organic phase; stripping the third loaded organic phase with an alkaline solution to obtain scandium hydroxide with an impurity content <1%.

Description

Technical Field

[0001] The present invention relates to the field of comprehensive utilization of industrial waste liquid and waste residue, and particularly to a method for co-extracting scandium from titanium white waste acid and low-temperature chlorination dust collection residue. Background Art

[0002] Scandium is a rare earth element and a strategic resource. However, more than 75% of scandium is associated with other minerals. The complex production process, low recovery rate, high cost and other factors of scandium result in insufficient international supply and high price of scandium products. It is known as one of the most expensive metals in the world. Domestic scandium ore resources are mainly distributed in bauxite, phosphorite (including weathered leached phosphorite deposits), vanadium-titanium magnetite, tungsten ore, rare earth ore and other minerals.

[0003] At present, the main sources of scandium extraction raw materials are secondary resources such as waste liquid or solid waste generated in the process of comprehensive utilization of its associated minerals. Existing secondary resources that can be used as scandium extraction raw materials include by-products of uranium ore, tungsten ore and tungsten ore slag, hydrolysis acidic waste liquid produced by sulfuric acid method for producing titanium dioxide, chlorination dust produced by fluidized bed chlorination for titanium extraction, titanium-bearing blast furnace slag, red mud, ion-adsorbed rare earth ore, Bayan Obo tailings, etc. For different scandium-containing raw materials, their physical and chemical properties are different, especially the chemical composition and the solubility in different leaching agents vary greatly, so the involved scandium extraction processes are different.

[0004] Although a large amount of research work has been carried out on the comprehensive utilization of recovering scandium, titanium, sulfuric acid, etc. from titanium white waste acid, and on the comprehensive utilization of recovering scandium, titanium, etc. from the dust collection residue generated in the low-temperature chlorination titanium extraction process, however, whether it is recovering scandium from titanium white waste acid or from low-temperature chlorination dust collection residue, the processes have problems such as complex process flow, high production cost, difficulty in industrialization, and environmental pollution caused by unreasonable waste treatment of titanium white waste acid or titanium extraction tailings. Summary of the Invention

[0005] To solve the above technical problems, the present invention proposes a method for co-extracting scandium from titanium white waste acid and low-temperature chlorination dust collection residue, which can solve the technical problems of complex process flow, high production cost, difficulty in industrialization and poor environmental protection benefits existing in the existing recovery of scandium from titanium white waste acid and from the dust collection residue generated in the low-temperature chlorination titanium extraction process.

[0006] An embodiment of the present invention discloses a method for co-extracting scandium from titanium white waste acid and low-temperature chlorination dust collection residue, including the following steps:

[0007] Leach the low-temperature chlorination dust collection residue with titanium white waste acid at a predetermined liquid-solid ratio to obtain a leachate and a leach residue;

[0008] Add a mixed solution of HF or NaF and phosphoric acid or phosphate to the leachate to remove zirconium, and obtain a scandium-containing solution after filtration;

[0009] Scandium in the scandium-containing solution is extracted by multi-stage countercurrent cyclone extraction with a first composite extractant at a first predetermined ratio to obtain a first loaded organic phase;

[0010] Then, a strong oxidizing and strong alkaline solution with a predetermined concentration is used to perform multi-stage countercurrent cyclone stripping on the first loaded organic phase at a second predetermined ratio to obtain a stripping product enriched in scandium and a stripped organic phase;

[0011] Scandium in the stripping product is leached with dilute acid, and after filtration, a scandium-rich solution is obtained. Scandium in the scandium-rich solution is extracted by countercurrent cyclone extraction with a second composite extractant at a third predetermined ratio to obtain a second loaded organic phase;

[0012] Impurities such as titanium, manganese, calcium, zirconium, iron, magnesium, and vanadium remaining in the second loaded organic phase are eluted with a mixed solution of hydrogen peroxide - sulfuric acid / hydrochloric acid - phosphoric acid with a predetermined concentration to obtain a third loaded organic phase;

[0013] Scandium in the third loaded organic phase is subjected to multi-stage countercurrent cyclone stripping with an alkali solution to obtain scandium hydroxide with an impurity content < 1%.

[0014] According to an embodiment of the present invention, it further includes one or more of the following steps:

[0015] The leaching residue is washed with water having a pH < 2 until the salt content (mass percentage) < 0.05%. The washed leaching residue can be further used for titanium recovery, and the washing water is recycled until a certain extent and then collected as a raw material for scandium extraction;

[0016] The stripped organic phase is regenerated with dilute acid and reused for scandium extraction;

[0017] The scandium hydroxide is successively dissolved in hydrochloric acid with a concentration of 1 - 5 mol / L and precipitated with oxalic acid to obtain a precipitate. The addition amount of oxalic acid is 1 - 1.5 times the theoretical mass required for complete precipitation of scandium ions. The precipitate is centrifuged, filtered, dehydrated, and calcined at 600 - 900 °C for 3 - 6 h, and finally scandium oxide with a purity ≥ 99.9% is obtained.

[0018] According to an embodiment of the present invention, the scandium content in the low-temperature chlorination dust collection residue is 10 - 150 g / t, the scandium concentration in the titanium white waste acid is 1 - 40 mg / L, the sulfuric acid concentration in the titanium white waste acid is 15% - 25%, the predetermined liquid-solid ratio is the volume ratio of the titanium white waste acid to the mass of the low-temperature chlorination dust collection residue is (1 - 10):1. Stirring is strengthened during the leaching process, and the leaching time is 2 - 5 h.

[0019] According to an embodiment of the present invention, in the mixed solution of HF or NaF and phosphoric acid or phosphate, the molar ratio of fluorine to phosphorus is 1:1 to 3, and the total addition amount of the mixed solution of HF or NaF and phosphoric acid or phosphate is 1 to 1.3 times the theoretical amount required to completely precipitate zirconium ions.

[0020] According to an embodiment of the present invention, the first composite extractant comprises the following components in volume percentages: tributyl phosphate TBP (5% - 30%) + bis(2-ethylhexyl) phosphate P204 (5% - 30%) + cyanex925 (0% - 10%) + 260# solvent oil (50% - 90%); the first predetermined phase ratio is the volume ratio of the first composite extractant to the leaching solution after reduction in the aqueous phase is 1:(1 - 30), and the first composite extractant is not saponified before extraction.

[0021] According to an embodiment of the present invention, the strongly oxidizing and strongly alkaline solution is strongly oxidizing and alkaline waste brine generated from the purification of molten salt chlorination tail gas or waste liquid from the absorption of chlor-alkali chemical tail gas; the second predetermined phase ratio is the volume ratio of the first loaded organic phase to the strongly oxidizing and strongly alkaline solution is 1:(1 - 10).

[0022] According to an embodiment of the present invention, the dilute acid is hydrochloric acid or sulfuric acid with a concentration of 1 - 5 mol / L, the second composite extractant comprises the following components in volume percentages: tributyl phosphate TBP (5% - 30%) + bis(2-ethylhexyl) phosphate P204 (5% - 30%) + cyanex925 (0% - 10%) + 260# solvent oil (50% - 90%), the third predetermined phase ratio is the volume ratio of the second composite extractant to the leaching solution after reduction in the aqueous phase is (1 - 30):1, and the second composite extractant is not saponified before extraction.

[0023] According to an embodiment of the present invention, in the mixed solution of hydrogen peroxide - sulfuric acid / hydrochloric acid - phosphoric acid: the concentration of sulfuric acid or hydrochloric acid is 1 - 5 mol / L, the concentration of hydrogen peroxide is 1 - 2 mol / L, the addition amount of phosphoric acid is 1 to 1.5 times the theoretical amount required to completely remove titanium and zirconium in the second loaded organic phase; the elution time is 10 - 30 min, the number of elution stages ≥ 1, and the elution phase ratio is the volume ratio of the mixed solution of hydrogen peroxide - sulfuric acid / hydrochloric acid - phosphoric acid to the second loaded organic phase is (0.5 - 5):1.

[0024] According to an embodiment of the present invention, the alkali solution is NaOH or ammonia water, the concentration of the alkali solution is 1.5 - 3 mol / L, and the volume ratio of the third loaded organic phase to the alkali solution is 1:(0.5 - 2).

[0025] According to an embodiment of the present invention, the extraction device or the stripping device is an acid- and alkali-resistant cyclone extractor, and the number of extraction stages ≥ 1 or the number of stripping stages ≥ 1.

[0026] Adopting the above technical solution, the present invention has at least the following beneficial effects:

[0027] The method for co-extracting scandium from titanium white waste acid and low-temperature chlorination dust collection slag provided by the present invention makes full use of sulfuric acid in the titanium white waste acid to leach scandium from the scandium-containing minerals in the low-temperature chlorination dust collection slag. While utilizing the waste acid in the titanium white waste acid, the comprehensive extraction of scandium in the titanium white waste acid and scandium in the low-temperature chlorination dust collection slag is realized, solving the problem of high production cost caused by extracting scandium from the low-temperature chlorination dust collection slag alone or from the titanium white waste acid alone, which is conducive to greatly saving costs and thus realizing industrial production. On the other hand, due to the impurities contained in the titanium white waste acid and the low-temperature chlorination dust collection slag, the present invention effectively removes impurities from the leaching solution to maximize the effective separation of scandium and various impurities, and finally scandium oxide with a purity ≥ 99.9% can be obtained. In addition, both the titanium white waste acid and the low-temperature chlorination dust collection slag are industrial wastes that have an adverse impact on the environment and both need to be environmentally treated. By jointly treating the titanium white waste acid and the low-temperature chlorination dust collection slag to extract scandium together through the method of the present invention, the purpose of treating waste with waste is achieved, and it has the advantages of good environmental protection benefits and simple process flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 It is a process schematic diagram of the method for co-extracting scandium from titanium white waste acid and low-temperature chlorination dust collection slag disclosed in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] In order to make the purpose, technical solution and advantages of the present invention clearer, the following will further describe the embodiments of the present invention in detail with reference to specific embodiments and the accompanying drawings.

[0031] It should be noted that all the expressions using "first" and "second" in the embodiments of the present invention are for distinguishing two entities or parameters with the same name but different, and it can be seen that "first" and "second" are only for the convenience of expression and should not be construed as a limitation to the embodiments of the present invention. This will not be elaborated in the subsequent embodiments one by one.

[0032] As shown in the figure, an embodiment of the present invention discloses a method for co-extracting scandium from titanium white waste acid and low-temperature chlorination dust collection residue, comprising the following steps:

[0033] Leach the low-temperature chlorination dust collection residue with titanium white waste acid at a predetermined liquid-solid ratio to obtain a leachate and a leach residue;

[0034] Add a mixed solution of HF or NaF and phosphoric acid or phosphate to the leachate to remove zirconium, and obtain a scandium-containing solution after filtration;

[0035] Extract scandium in the scandium-containing solution by multi-stage countercurrent swirl extraction with a first composite extractant at a first predetermined phase ratio to obtain a first loaded organic phase;

[0036] Then use a strong oxidizing and strong alkaline solution with a predetermined concentration to perform multi-stage countercurrent swirl stripping on the first loaded organic phase at a second predetermined phase ratio to obtain a scandium-enriched stripping product and a stripped organic phase;

[0037] Leach scandium in the stripping product with dilute acid, and obtain a scandium-rich solution after filtration. Extract scandium in the scandium-rich solution by countercurrent swirl extraction with a second composite extractant at a third predetermined phase ratio to obtain a second loaded organic phase;

[0038] Elute impurities such as residual titanium, manganese, calcium, zirconium, iron, magnesium, and vanadium in the second loaded organic phase with a mixed solution of hydrogen peroxide-sulfuric acid / hydrochloric acid-phosphoric acid at a predetermined concentration to obtain a third loaded organic phase;

[0039] Perform multi-stage countercurrent swirl stripping on scandium in the third loaded organic phase with an alkali solution to obtain scandium hydroxide with an impurity content <1%.

[0040] In the above embodiment, adding a mixed solution of HF or NaF and phosphoric acid or phosphate to the leachate to remove zirconium results in basically no loss of scandium during this process. Extracting scandium in the scandium-rich solution by countercurrent swirl extraction with a second composite extractant at a third predetermined phase ratio not only obtains a second loaded organic phase but also obtains a raffinate.

[0041] Leaching scandium from the low-temperature chlorination dust collection residue with titanium white waste acid, on the one hand, both titanium white waste acid and low-temperature chlorination dust collection residue contain scandium, and the combined use of the two can increase the scandium content in the leachate. For the low-temperature chlorination dust collection residue, compared with leaching with an acid without scandium, the scandium content in the leachate is increased; on the other hand, sulfuric acid in the titanium white waste acid can leach scandium from the scandium-containing minerals in the low-temperature chlorination dust collection residue, which is beneficial to cost savings.

[0042] In some embodiments, the method for co-extracting scandium from titanium white waste acid and low-temperature chlorination dust collection residue further includes: washing the leaching residue with water having a pH < 2 until the salt content (mass percentage) of the leaching residue is < 0.05%. The washed leaching residue can be further used for titanium recovery. The washing water is recycled and collected as a raw material for scandium extraction after being used to a certain extent; the organic phase after back-extraction is regenerated with dilute acid and then used for scandium extraction again. Treating the washing water and the organic phase after back-extraction and using them for scandium extraction again is beneficial to greatly improving the recovery rate of scandium. Among them, washing the leaching residue with water having a pH < 2 can prevent the hydrolysis of scandium ions.

[0043] In some embodiments, the method for co-extracting scandium from titanium white waste acid and low-temperature chlorination dust collection residue further includes: dissolving scandium hydroxide successively with hydrochloric acid having a concentration of 1 - 5 mol / L and then precipitating with oxalic acid to obtain a precipitate. The addition amount of oxalic acid is 1 - 1.5 times the theoretical mass required to completely precipitate scandium ions. The precipitate is centrifuged, filtered, dehydrated, and then calcined at 600 - 900 °C for 3 - 6 h, and finally scandium oxide with a purity ≥ 99.9% is obtained. In this embodiment, the hydrochloric acid dissolution process can completely remove silicon-containing impurities, and the scandium-containing impurity-removing solution is then used to precipitate scandium ions with oxalic acid.

[0044] In some embodiments, the scandium content in the low-temperature chlorination dust collection residue is 10 - 150 g / t, the scandium concentration in the titanium white waste acid is 1 - 40 mg / L, the sulfuric acid concentration in the titanium white waste acid is 15% - 25%, the predetermined liquid-solid ratio is the volume ratio of the titanium white waste acid to the mass of the low-temperature chlorination dust collection residue is (1 - 10):1. Stirring is intensified during the leaching process, and the leaching time is 2 - 5 h.

[0045] In some embodiments, the molar ratio of fluorine to phosphorus in the mixed solution of HF or NaF and phosphoric acid or phosphate is 1:1 - 3. The total addition amount of the mixed solution of HF or NaF and phosphoric acid or phosphate is 1 - 1.3 times the theoretical amount required to completely precipitate zirconium ions. A scandium-containing solution is obtained after filtration, and scandium is basically not lost during this process.

[0046] In some embodiments, the first composite extractant includes the following components by volume percentage: tributyl phosphate TBP (5% - 30%) + bis(2-ethylhexyl) phosphoric acid ester P204 (5% - 30%) + cyanex925 (0% - 10%) + 260# solvent oil (50% - 90%); the first predetermined phase ratio is the volume ratio of the first composite extractant to the reduced leaching solution of the aqueous phase is 1:(1 - 30). The first composite extractant is not saponified before extraction, which is beneficial to simplifying the process flow and improving efficiency. In some other embodiments, increasing the acidity of the reduced leaching solution to be extracted during the extraction process has basically no effect on the extraction of scandium ions but is beneficial to inhibiting the extraction of other ions.

[0047] In some embodiments, the strongly oxidizing and strongly alkaline solution is the strongly oxidizing and alkaline waste brine generated from the purification of molten salt chlorination tail gas or the waste liquid from the absorption of chlor-alkali chemical tail gas; the second predetermined phase ratio is that the volume ratio of the first loaded organic phase to the strongly oxidizing and strongly alkaline solution is 1:(1 - 10).

[0048] In some embodiments, scandium in the stripping product is leached with dilute acid. The dilute acid is hydrochloric acid or sulfuric acid with a concentration of 1 - 5 mol / L. The second composite extractant comprises the following components by volume percentage: tributyl phosphate TBP (5% - 30%) + bis(2-ethylhexyl) phosphate P204 (5% - 30%) + cyanex925 (0% - 10%) + 260# solvent oil (50% - 90%). The third predetermined phase ratio is that the volume ratio of the second composite extractant to the leaching solution after reduction of the aqueous phase is (1 - 30):1, and the second composite extractant is not saponified; increasing the acidity of the leaching solution after reduction to be extracted has basically no effect on the extraction of scandium ions but is beneficial to inhibiting the extraction of other ions.

[0049] In some embodiments, a mixed solution of hydrogen peroxide - sulfuric acid / hydrochloric acid - phosphoric acid with a predetermined concentration is used to elute the impurities such as titanium, manganese, calcium, zirconium, iron, magnesium, and vanadium remaining in the second loaded organic phase. In the mixed solution of hydrogen peroxide - sulfuric acid / hydrochloric acid - phosphoric acid: the concentration of sulfuric acid or hydrochloric acid is 1 - 5 mol / L, the concentration of hydrogen peroxide is 1 - 2 mol / L, and the addition amount of phosphoric acid is 1 - 1.5 times the theoretical amount required to completely remove titanium and zirconium in the second loaded organic phase; the elution time is 10 - 30 min, the number of elution stages ≥ 1, and the elution phase ratio is that the volume ratio of the mixed solution of hydrogen peroxide - sulfuric acid / hydrochloric acid - phosphoric acid to the second loaded organic phase is (0.5 - 5):1.

[0050] In some embodiments, scandium in the third loaded organic phase is subjected to multi-stage countercurrent cyclone stripping with an alkali solution. The alkali solution is NaOH or ammonia water, the concentration of the alkali solution is 1.5 - 3 mol / L, the volume ratio of the third loaded organic phase to the alkali solution is 1:(0.5 - 2), the concentration of hydrochloric acid is 1 - 5 mol / L, and the addition amount of oxalic acid is 1 - 1.5 times the theoretical mass required to completely precipitate scandium ions. The precipitate is calcined at high temperature, that is, after centrifugal filtration and dehydration, it is calcined at 600 - 900 °C for 3 - 6 h.

[0051] In some embodiments, the extraction device or the stripping device is an acid - alkali resistant cyclone extractor, and the number of extraction stages ≥ 1 or the number of stripping stages ≥ 1. The acid - alkali resistant cyclone extractor is beneficial to the separation of the stripping product. The model and operating parameters of the acid - alkali resistant cyclone extractor can be adjusted according to the material liquid situation.

[0052] The following takes the titanium white waste acid and low - temperature chlorination dust collected during a certain sampling as an example to specifically illustrate the method for co - extracting scandium from titanium white waste acid and low - temperature chlorination dust disclosed in the embodiments of the present invention.

[0053] Example

[0054] The main components of the titanium white waste acid and the low-temperature chlorination dust collected by sampling are shown in Tables 1 and 2 respectively.

[0055] Table 1 Main components of the titanium white waste acid collected by sampling

[0056]

[0057] Table 2 Main components of the low-temperature chlorination dust collected by sampling

[0058]

[0059] Leach the low-temperature chlorination dust collection residue with titanium white waste acid. The volume ratio of titanium white waste acid to the mass of the low-temperature chlorination dust collection residue is 3:1. Stir vigorously during the leaching process. The leaching time is 4 h, and the leaching rate of scandium is about 90%. Add a mixed solution of NaF and sodium dihydrogen phosphate to the leaching solution to remove zirconium. The molar ratio of fluorine to phosphorus is 1:2, and the total addition amount is 1.1 times the theoretical amount required to completely precipitate zirconium ions. The removal rate of zirconium in this process is 99%. After filtration, a scandium-containing solution is obtained. Use the first composite extractant tributyl phosphate TBP (5%) + bis(2-ethylhexyl) phosphate P204 (20%) + cyanex925 (5%) + 260# solvent oil (70%) to directly perform swirl extraction on the scandium in the scandium-containing solution under the condition of non-saponification. The phase ratio is 1:10. The extraction rate of scandium in this process reaches 99%, and the extraction rates of the remaining impurities in the scandium-containing solution are only about 0.1% - 3%. Then, use the strongly oxidizing and alkaline waste brine generated from the purification of molten salt chlorination tail gas with 10% alkali content adjusted by caustic soda to perform swirl back-extraction on the first loaded organic phase. The phase ratio is 1:1, obtaining a back-extract enriched in scandium and the back-extracted organic phase. The back-extraction rate of scandium reaches 99%. Leach the scandium in the back-extract with 3 mol / L sulfuric acid. The leaching rate of scandium is 100%. After filtration, a scandium-rich solution is obtained. Use the second composite extractant tributyl phosphate TBP (5%) + bis(2-ethylhexyl) phosphate P204 (20%) + cyanex925 (5%) + 260# solvent oil (70%) to directly perform swirl extraction on the scandium in the scandium-rich solution under the condition of non-saponification. The phase ratio is 10:1. The extraction rate of scandium in this process reaches 99%, and the extraction rates of the remaining impurities in the scandium-rich solution are only about 0.1% - 1%. Elute the remaining impurities such as titanium, manganese, calcium, zirconium, iron, magnesium, and vanadium in the second loaded organic phase with a mixed solution of hydrogen peroxide - sulfuric acid - phosphoric acid. The sulfuric acid concentration is 5 mol / L, the hydrogen peroxide concentration is 1.5 mol / L, and the addition amount of phosphoric acid is 1 times the theoretical amount required to completely remove titanium and zirconium in the second loaded organic phase. The elution time is 15 min, the number of elution stages is 3, and the phase ratio is 2:1. The loss rate of scandium in this process is about 0.5%, obtaining the third loaded organic phase. Perform swirl back-extraction on the third loaded organic phase with 3 mol / L NaOH solution. The phase ratio is 1:1, obtaining scandium hydroxide with an impurity content < 1%. The back-extraction rate of scandium in this process is 99%. Scandium hydroxide is completely dissolved with 2.5 mol / L hydrochloric acid in sequence and then precipitated with oxalic acid. The addition amount of oxalic acid is 1.05 times the theoretical mass required to completely precipitate scandium ions. The precipitate is centrifuged, filtered, dehydrated, and then calcined at 850 °C for 6 h. Finally, scandium oxide with a purity of 99.91% is obtained.

[0060] In summary, the method for co-extracting scandium from titanium white waste acid and low-temperature chlorination dust collection slag provided by the embodiments of the present invention makes full use of sulfuric acid in the titanium white waste acid to leach scandium from the scandium-containing minerals in the low-temperature chlorination dust collection slag. While utilizing the waste acid in the titanium white waste acid, it realizes the comprehensive extraction of scandium in the titanium white waste acid and scandium in the low-temperature chlorination dust collection slag, solves the problem of high production cost caused by extracting scandium from the low-temperature chlorination dust collection slag alone or from the titanium white waste acid alone, is conducive to greatly saving costs, and thus realizes industrial production. On the other hand, due to the impurities contained in the titanium white waste acid and the low-temperature chlorination dust collection slag, the present invention effectively removes impurities from the leaching solution to maximize the effective separation of scandium and various impurities, and finally scandium oxide with a purity ≥ 99.9% can be obtained. In addition, both the titanium white waste acid and the low-temperature chlorination dust collection slag are industrial wastes that have an adverse impact on the environment and need to be environmentally treated. By using the method of the present invention to jointly treat the titanium white waste acid and the low-temperature chlorination dust collection slag for co-extracting scandium, the purpose of treating waste with waste is achieved, which has the advantages of good environmental protection benefits and a simple process flow.

[0061] It should be particularly noted that each component or step in the above-mentioned various embodiments can be cross-linked, replaced, added, or deleted with each other. Therefore, the combinations formed by these reasonable permutations and combinations should also fall within the protection scope of the present invention, and the protection scope of the present invention should not be limited to the above-mentioned embodiments.

[0062] The above are the exemplary embodiments disclosed by the present invention. The order of disclosure of the above embodiments of the present invention is only for description and does not represent the superiority or inferiority 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 of disclosure of the embodiments of the present invention (including the claims) is limited to these examples. Without departing from the scope defined by the claims, various changes and modifications can be made. The functions, steps, and / or actions of the method claims according to the disclosed embodiments here do not need to be executed in any specific order. In addition, although the elements disclosed in the embodiments of the present invention can be described or claimed in individual form, they can also be understood as plural unless explicitly limited to the singular.

[0063] Those of ordinary skill 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 disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the idea of the embodiments of the present invention, the technical features between 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 brevity. Therefore, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle 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 co-extracting scandium from titanium white waste acid and low-temperature chlorination dust collection slag, characterized in that, It includes the following steps: Leach the low-temperature chlorination dust collection residue with titanium white waste acid at a predetermined liquid-solid ratio to obtain a leaching solution and a leaching residue; Add a mixed solution of HF or NaF and phosphoric acid or phosphate to the leaching solution to remove zirconium, and obtain a scandium-containing solution after filtration; Extract scandium in the scandium-containing solution by multi-stage countercurrent cyclone extraction with a first composite extractant at a first predetermined phase ratio to obtain a first loaded organic phase; Then, use a strong oxidizing and strong alkaline solution with a predetermined concentration to perform multi-stage countercurrent cyclone stripping on the first loaded organic phase at a second predetermined phase ratio to obtain a stripping product enriched in scandium and a stripped organic phase; Leach scandium in the stripping product with dilute acid, obtain a scandium-rich solution after filtration, and extract scandium in the scandium-rich solution by countercurrent cyclone extraction with a second composite extractant at a third predetermined phase ratio to obtain a second loaded organic phase; Elute the residual impurities in the second loaded organic phase with a mixed solution of hydrogen peroxide-sulfuric acid / hydrochloric acid-phosphoric acid with a predetermined concentration, where the impurities include titanium, manganese, calcium, zirconium, iron, magnesium, and vanadium, to obtain a third loaded organic phase; Perform multi-stage countercurrent cyclone stripping on scandium in the third loaded organic phase with an alkali solution to obtain scandium hydroxide with an impurity content <1%; 2. The method according to claim 1, wherein It also includes one or more of the following steps: Wash the leaching residue with acidic wash water with pH < 2 until the salt content of the leaching residue is <0.05% by mass percentage. The washed leaching residue can be further used for titanium recovery, and the wash water is recycled until a certain extent and then collected as a raw material for scandium extraction; The stripped organic phase is regenerated with dilute acid and reused for scandium extraction; Dissolve the scandium hydroxide in hydrochloric acid with a concentration of 1-5 mol / L in sequence, precipitate with oxalic acid, where the addition amount of oxalic acid is 1-1.5 times the theoretical mass required to completely precipitate scandium ions. The precipitate is centrifuged, filtered, dehydrated, and calcined at 600-900 °C for 3-6 h, and finally obtain scandium oxide with a purity ≥ 99.9%; 3. The method according to claim 1, characterized in that, The scandium content in the low-temperature chlorination dust collection residue is 10-150 g / t, the scandium concentration in the titanium white waste acid is 1-40 mg / L, the sulfuric acid concentration in the titanium white waste acid is 15%-25%, the predetermined liquid-solid ratio is the volume ratio of the titanium white waste acid to the mass of the low-temperature chlorination dust collection residue is (1-10):

1. Stirring is strengthened during the leaching process, and the leaching time is 2-5 h; 4. The method according to claim 1, wherein The molar ratio of fluorine to phosphorus in the mixed solution of HF or NaF and phosphoric acid or phosphate is 1:1-3, and the total addition amount of the mixed solution of HF or NaF and phosphoric acid or phosphate is 1-1.3 times the theoretical amount required to completely precipitate zirconium ions; 5. The method according to claim 1, wherein The first composite extractant includes the following components by volume percentage: 5-30% tributyl phosphate, 5-30% bis(2-ethylhexyl) phosphoric acid ester, 0-10% cyanex925, and 50-90% 260# solvent oil; the first predetermined phase ratio is the volume ratio of the first composite extractant to the reduced leaching solution in the aqueous phase is 1:(1-30), and the first composite extractant is not saponified before extraction; 6. The method according to claim 1, wherein The strongly oxidizing and strongly alkaline solution is strongly oxidizing and alkaline waste brine generated from the purification of molten salt chlorination tail gas or waste liquid from the absorption of chlor-alkali chemical tail gas; the second predetermined phase ratio is that the volume ratio of the first loaded organic phase to the strongly oxidizing and strongly alkaline solution is 1:(1-10).

7. The method according to claim 1, wherein The dilute acid is hydrochloric acid or sulfuric acid with a concentration of 1-5 mol / L. The second composite extractant includes the following components by volume percentage: 5-30% tributyl phosphate, 5-30% bis(2-ethylhexyl) phosphoric acid ester, 0-10% cyanex925, 50-90% solvent oil 260#. The third predetermined phase ratio is that the volume ratio of the second composite extractant to the leaching solution after water phase reduction is (1-30):1, and the second composite extractant is not saponified before extraction.

8. The method according to claim 1, characterized in that, In the mixed solution of hydrogen peroxide - sulfuric acid / hydrochloric acid - phosphoric acid: the concentration of sulfuric acid or hydrochloric acid is 1-5 mol / L, the concentration of hydrogen peroxide is 1-2 mol / L, and the addition amount of phosphoric acid is 1-1.5 times the theoretical amount required to completely remove titanium and zirconium in the second loaded organic phase; the elution time is 10-30 min, the number of elution stages ≥ 1, and the elution phase ratio is that the volume ratio of the mixed solution of hydrogen peroxide - sulfuric acid / hydrochloric acid - phosphoric acid to the second loaded organic phase is (0.5-5):

1.

9. The method according to claim 1, characterized in that, The alkali solution is NaOH or ammonia water, the concentration of the alkali solution is 1.5-3 mol / L, and the volume ratio of the third loaded organic phase to the alkali solution is 1:(0.5-2).

10. The method according to claim 1, characterized in that, The extraction equipment or stripping equipment is an acid and alkali resistant cyclone extractor, and the number of extraction stages ≥ 1 or the number of stripping stages ≥ 1.

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