A method for recovering scandium titanium from titanium dioxide waste acid using a bisphosphonic acid extractant

Abstract

The present invention discloses a method for recovering scandium from titanium dioxide waste acid using a bisphosphonic acid extractant, the steps of which include: single-stage extraction with an extractant N, N-dodecylamine di(methylenephenylphosphonic acid) (TADMPPA) in titanium dioxide waste acid, and the extraction rate of extracting trace scandium in a high-acidity titanium dioxide waste acid simulation liquid can be as high as 99.9% in a single time. The present technology has short extraction time, high efficiency, simple operation, low pollution, and no emulsification. The organic phase after extraction is washed with a sulfuric acid solution, impurities are removed, and the washed organic phase is stripped with a mixed solution of sodium citrate and hydrogen peroxide, and the stripping solution is added with oxalic acid to precipitate scandium, and the precipitate is calcined at 700-1000°C to obtain scandium oxide with a purity greater than 99%. The present invention recovers part of titanium while ensuring the recovery of scandium, reduces the cost of scandium recovery, has the advantages of environmental protection and simple process, high scandium oxide yield, and is suitable for large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of solution extraction, and in particular relates to a method for recovering scandium titanium from titanium dioxide waste acid. Background Art

[0002] Scandium is difficult to enrich in nature to form independent scandium minerals. It is often associated with other minerals. Its recovery process is complex, the recovery rate is low, and the cost is high, which makes scandium one of the most expensive metals in the world. The lack of reliable supply and high production costs have hindered the application of scandium in high-end technologies to a certain extent. Therefore, it is crucial to seek large quantities of cheap recycled scandium raw materials. Most of the scandium oxide produced in my country comes from titanium dioxide plants. my country is the world's second largest producer of titanium dioxide. The industry produces a total of about 8,000 kt / a of waste acid. The average mass concentration of Sc in titanium dioxide waste acid is about 10-20 mg / L, which is a good secondary resource rich in scandium. However, titanium dioxide waste acid has the characteristics of many types of impurity metal elements and high concentrations. Among them, the separation problem of scandium and titanium has not been well solved due to their similar physical properties. Traditional scandium extraction processes mostly use P204, P507, etc. as the main extractant, TBP as the auxiliary extractant for multi-stage continuous synergistic extraction, and then use a high-concentration sulfuric acid + H2O2 mixed solution for multi-stage continuous washing of titanium, which accounts for two-thirds of the total cost and produces a large amount of new wastewater containing H2O2 to be treated, increasing environmental pressure, multiple washing stages, large floor space, high cost, etc., and traditional extractants often have problems such as poor separation of scandium and other impurities, difficult stripping, and easy emulsification. Scandium ions are trivalent cations with high charge, small radius, and strong hydration ability. The extraction rate of general extractants is not high. For example, "A method for recovering scandium from titanium dioxide waste acid" (CN103614560A) uses 20% P204 + 7% TBP + 73% sulfonated kerosene as the extraction system to recover scandium from titanium dioxide waste acid, and can obtain scandium with a purity of 99.78%, but the recovery rate can only reach 70%, and although P204 has a strong ability to extract scandium, the extraction rate can be as high as 99%, but its selectivity is relatively poor, and it is prone to three-phase problems and is not easy to strip. "A composite extractant for extracting scandium from vanadium-titanium-iron tailings leachate, preparation method and extraction method" (CN113151698A) uses P204 + P507 + TTA composite extractant, and through synergistic effect, the extraction rate of scandium can be improved, and the extraction rate can reach 93%, but the problem of separation difficulty still exists, and the addition of TTA has a greater irritation to the eyes, respiratory system and skin. "A new method for extracting scandium oxide from titanium dioxide waste acid using a new type of extractant" (CN112095026A) uses dioctyl phosphate + tributyl phosphate as extractants, and the separation effect is better, but the maximum extraction rate can only reach 85%, and the leaching process will produce a large amount of acidic wastewater, causing environmental pollution.

[0003] In "A method for recovering scandium from titanium dioxide wastewater" (CN201310329294.8), P204+TBP+kerosene is used as an extraction system to obtain an organic phase enriched with scandium and titanium, and then the organic phase is stripped with sodium hydroxide, acid-dissolved, and hydrogen peroxide is added, and then the aforementioned extractant is used to repeat the steps of extraction, stripping, and acid-dissolving until the recovery requirements are met. This process method has a long flow, high reagent consumption, and a low recovery rate of scandium and titanium. In "A method for recovering scandium and titanium from titanium dioxide wastewater" (CN102703709A), P507+TBP+kerosene is used for single-stage extraction, and then a process flow of alkali stripping, acid-dissolving, secondary extraction, acid-dissolving, precipitation, and calcination is used to recover scandium and titanium, thereby reducing the cost of scandium recovery. However, this process requires secondary extraction, which consumes a large amount of extractant, resulting in increased costs and is not conducive to large-scale production. The existing process of recovering scandium titanium from waste titanium dioxide acid uses a high-concentration sulfuric acid-hydrogen peroxide mixed solution for multi-stage countercurrent washing after extraction, which not only produces a large amount of low-concentration waste acid, but also has low efficiency in washing titanium. Some scholars also use hydrolysis to remove titanium or perform secondary extraction to separate scandium titanium, but the process is complicated, the cost is high, and the loss of scandium is large. Therefore, it is necessary to test an efficient, convenient, and low-cost scandium titanium recovery process. Summary of the invention

[0004] The commonly used extractants for extracting scandium from titanium dioxide waste acid generally have problems such as low selectivity, easy emulsification, and easy three-phase formation, which greatly limits its large-scale application in industry. This patent studies a new type of extractant, N, N-dodecylamine di (methylenebenzene phosphite) extractant. This extractant has a bifunctional group, which not only has multiple charges to attract scandium ions, but also can form a chelate ring with scandium ions, greatly improving the ability to capture scandium in titanium dioxide waste acid. The invention extraction process can remove impurities other than scandium and titanium by washing with sulfuric acid solution, and further use sodium citrate + H2O2 mixed solution to first extract scandium and leave titanium in the organic phase, so as to achieve the separation of scandium and titanium, and obtain scandium oxide with a purity of more than 99%, and recover part of high-purity titanium. The N, N-dodecylamine di (methylenebenzene phosphite) extractant used in this patent is simple to synthesize, the required raw materials are all cheap and easy to obtain, and it has strong acid resistance. It can have a good extraction effect on scandium in high-concentration titanium dioxide waste acid. In the entire scandium extraction process, the multi-stage continuous washing process of titanium with a high-concentration sulfuric acid + H2O2 mixed solution is eliminated. Only sulfuric acid solution is used for washing and a mixed solution of sodium citrate and hydrogen peroxide is used for selective stripping of scandium. Scandium and titanium can be well separated, and scandium and titanium can be recovered separately, thereby reducing the scandium recovery cost and improving the yield of scandium and titanium. In addition, the operation is simple, the site is small, and it is easy to scale up production.

[0005] The present invention adopts a method for recovering scandium titanium from titanium dioxide waste acid using a diphosphonic acid extractant, and is carried out according to the following steps:

[0006] (1) Titanium dioxide waste acid is the water phase.

[0007] (2) The diphosphonic acid extractant prepared with a diluent is used as the organic phase.

[0008] (3) The aqueous phase and the organic phase are mixed and extracted, and the mixed solution after extraction is separated into phases to obtain an organic phase loaded with scandium and a raffinate containing other metal elements.

[0009] (4) The organic phase loaded with scandium ions is washed with a sulfuric acid solution for preliminary impurity removal.

[0010] (5) The organic phase washed with the sulfuric acid solution is back-extracted with a mixed solution of sodium citrate and H2O2 to obtain an aqueous solution containing scandium ions and an organic phase loaded with titanium.

[0011] (6) The obtained titanium-loaded organic phase is stripped with a mixed solution of sulfuric acid and H2O2 to recover the titanium; the organic phase is reused in the extraction process.

[0012] (7) The obtained aqueous solution containing scandium ions is precipitated with oxalic acid, and the obtained precipitate is separated. The main component of the precipitate is scandium oxalate.

[0013] (8) calcining the obtained precipitate to obtain a scandium oxide product.

[0014] The scandium content in the titanium dioxide waste acid is 1 to 20 ppm, and the sulfuric acid concentration is 0.5 to 5 mol / L.

[0015] The diphosphonic acid extractant is N,N-dodecylamine di(methylenebenzenephosphonic acid) with a concentration of 0.01-2 mol / L, preferably 0.05-1 mol / L.

[0016] The diluent is dichloromethane or chloroform, preferably chloroform.

[0017] The mixed phase ratio of the aqueous phase and the organic phase is 1:10-10:1, preferably 1:5-5:1; the extraction time is 1-120 minutes, preferably 10-30 minutes; the extraction temperature is 5-100°C, preferably 20-60°C.

[0018] The concentration of the sulfuric acid solution is 0.1-10 mol / L, preferably 3-6 mol / L.

[0019] The concentration of the sodium citrate solution is 0.005-2 mol / L, preferably 0.01-1 mol / L. The concentration of the hydrogen peroxide solution is 1%-30%.

[0020] The calcination temperature is 600°C to 1200°C, preferably 800°C to 1000°C.

[0021] Compared with the prior art, the present invention has the following characteristics and beneficial effects:

[0022] (1) The present invention uses N,N-dodecylamine di(methylenebenzenephosphonic acid) as an extractant, which has a high extraction rate for scandium. At a concentration of 0.1 mol / L, the single extraction rate for scandium can be as high as 99.9% or more. Compared with other commonly used scandium extractants, P204, P507, P350, etc., the extraction rates for scandium at the same concentration are only 60%-70%, and most of them have problems such as severe emulsification and difficulty in stripping. N,N-dodecylamine di(methylenebenzenephosphonic acid) not only has a high extraction rate, but also has rapid phase separation and is easy to strip, and has a good application prospect.

[0023] (2) This extractant is different from other scandium extractants with poor selectivity. It has a good extraction effect only on scandium and titanium. Titanium can be efficiently separated from scandium in the subsequent process to obtain a scandium oxide product with higher purity.

[0024] (3) The extractant has good thermal stability, is not easy to volatilize, and can be reused. The raw materials used in its synthesis are cheap and easily available, and the synthesis is simple, thus saving the cost of scandium recovery.

[0025] (4) After extraction, the extraction process uses sulfuric acid solution for washing and impurity removal, and then uses sodium citrate and H2O2 for back extraction, effectively separating scandium and titanium. This recycling process does not require a lengthy washing process, shortens the process flow, occupies a small area, and saves recycling costs. At the same time, this process shortens the washing process, reduces the amount of waste acid and wastewater, and meets the goal of green production. Specific implementation methods

[0026] The extraction distribution ratio (D) and extraction rate (E) can intuitively show the extraction capacity of the extractant. D represents the ratio of metal ion concentrations in the organic phase and the aqueous phase after extraction. E represents the ratio of the scandium concentration in the titanium dioxide waste acid after extraction to that before extraction. The separation factor (β) is an important basis for reflecting the separation effect. β represents the ratio of the scandium distribution ratio to the distribution ratio of other metal elements. The concentration of ions in this patent is determined by ICP-MS.

[0027] The present invention is described in detail below with reference to specific embodiments, but the protection scope of the present invention is not limited by the embodiments.

[0028] Example 1

[0029] The titanium dioxide waste acid is used as the aqueous phase, and the concentration of sulfuric acid in the aqueous phase is 7 mol / L. The types and contents of metals in the titanium dioxide waste acid are shown in Table 1.

[0030] The organic phase is prepared with 0.1mol / L N,N-dodecylamine di(methylenebenzenephosphite) prepared by diluent, and the diluent is chloroform. Take 100mL of organic phase and mix it with 1L of water phase, the extraction time is 20min, the extraction temperature is 25℃, the concentration of scandium in the raffinate is determined, and the extraction rate of scandium reaches 99.49%. The organic phase loaded with scandium obtained after the extraction of bisphosphonic acid is washed with 6mol / L sulfuric acid solution, and the content of each element in the raffinate is determined. It is found that a large amount of impurity elements such as calcium, iron, chromium, and manganese are removed, which is conducive to the next step of refining. The organic phase loaded with scandium after one washing is washed twice with a mixed solution of 1mol / L sodium citrate + 20% H2O2 to obtain an aqueous solution containing scandium ions and an organic phase loaded with titanium. The titanium in the organic phase is stripped by sulfuric acid + H2O2 to recover the titanium in the organic phase. After the second washing, an aqueous phase containing the scandium element is obtained. The changes of elements in the titanium dioxide waste acid after extraction, washing and stripping are shown in Table 1. The aqueous phase containing the scandium element obtained after the second washing is precipitated with oxalic acid, and the obtained precipitate is separated. The main component of the precipitate is scandium oxalate. The obtained scandium oxalate precipitate is placed in a muffle furnace and calcined at 800℃ for 6h to obtain a scandium oxide product with a purity greater than 99%.

[0031] Table 1

[0032]

[0033] Example 2

[0034] The titanium dioxide waste acid is used as the aqueous phase, and the concentration of sulfuric acid in the aqueous phase is 7 mol / L. The types and contents of metals in the titanium dioxide waste acid are shown in Table 1.

[0035] The organic phase is prepared with 0.01mol / L N,N-dodecylamine di(methylenebenzenephosphite) as the diluent, and the diluent is chloroform. Take 100mL of the organic phase and mix it with 1L of the aqueous phase. The extraction time is 20min and the extraction temperature is 25℃. The concentration of scandium in the raffinate is determined, and the extraction rate of scandium reaches 94.52%. The organic phase loaded with scandium obtained after the extraction of bisphosphonic acid is washed with 6mol / L sulfuric acid solution, and the content of each element in the raffinate is determined. It is found that a large amount of impurity elements such as calcium, iron, chromium, and manganese are removed, which is conducive to the next step of refining. The organic phase loaded with scandium after one washing is washed again with a mixed solution of 1mol / L sodium citrate + 20% H2O2 to obtain an aqueous solution containing scandium ions and an organic phase loaded with titanium. Titanium in the organic phase is stripped with sulfuric acid + H2O2 to recover titanium in the organic phase. The aqueous phase containing scandium element obtained after the second washing is precipitated with oxalic acid, and the obtained precipitate is separated. The main component of the precipitate is scandium oxalate. The obtained scandium oxalate precipitate is placed in a muffle furnace and calcined at 800°C for 6 hours to obtain a scandium oxide product with a purity greater than 90%.

[0036] Example 3

[0037] The titanium dioxide waste acid is used as the aqueous phase, and the concentration of sulfuric acid in the aqueous phase is 7 mol / L. The types and contents of metals in the titanium dioxide waste acid are shown in Table 1.

[0038] The organic phase is prepared with 1mol / L N,N-dodecylamine di(methylenebenzenephosphite) prepared by diluent, and the diluent is chloroform. Take 100mL of organic phase and mix it with 1L of water phase, the extraction time is 20min, the extraction temperature is 25℃, the concentration of scandium in the raffinate is determined, and the extraction rate of scandium reaches 99.68%. The organic phase loaded with scandium obtained after the extraction of bisphosphonic acid is washed with 6mol / L sulfuric acid solution, and the content of each element in the raffinate is determined. It is found that a large amount of impurity elements such as calcium, iron, chromium, and manganese are removed, which is conducive to the next step of refining. The organic phase loaded with scandium after the first washing is washed again with a mixed solution of 1mol / L sodium citrate + 20% H2O2 to obtain an aqueous solution containing scandium ions and an organic phase loaded with titanium. The titanium in the organic phase is stripped by sulfuric acid + H2O2 to recover the titanium in the organic phase. The aqueous phase containing the scandium element obtained after the second washing is precipitated with oxalic acid, and the precipitate obtained is separated. The main component of the precipitate is scandium oxalate. The obtained scandium oxalate precipitate is placed in a muffle furnace and calcined at 800°C for 6 hours to obtain a scandium oxide product with a purity greater than 99%.

[0039] Table 2

[0040] Extractant concentration E(％) Example 1 0.1mol / L 99.49 Example 2 0.01mol / L 94.52 Example 3 1mol / L 99.68

[0041] Example 4

[0042] The titanium dioxide waste acid is used as the aqueous phase, and the concentration of sulfuric acid in the aqueous phase is 7 mol / L. The types and contents of metals in the titanium dioxide waste acid are shown in Table 1.

[0043] The organic phase is prepared with 0.1mol / L N,N-dodecylamine di(methylenebenzenephosphite) as the diluent, and the diluent is chloroform. Take 100mL of the organic phase and mix it with 1L of the aqueous phase. The extraction time is 20min and the extraction temperature is 15℃. The concentration of scandium in the raffinate is determined, and the extraction rate of scandium reaches 99.09%. The organic phase loaded with scandium obtained after the extraction of bisphosphonic acid is washed with 6mol / L sulfuric acid solution, and the content of each element in the raffinate is determined. It is found that a large amount of impurity elements such as calcium, iron, chromium, and manganese are removed, which is conducive to the next step of refining. The organic phase loaded with scandium after one washing is washed again with a mixed solution of 1mol / L sodium citrate + 20% H2O2 to obtain an aqueous solution containing scandium ions and an organic phase loaded with titanium. Titanium in the organic phase is stripped with sulfuric acid + H2O2 to recover titanium in the organic phase. The aqueous phase containing scandium element obtained after the second washing is precipitated with oxalic acid, and the obtained precipitate is separated. The main component of the precipitate is scandium oxalate. The obtained scandium oxalate precipitate is placed in a muffle furnace and calcined at 800°C for 6 hours to obtain a scandium oxide product with a purity greater than 98%.

[0044] Example 5

[0045] The titanium dioxide waste acid is used as the aqueous phase, and the concentration of sulfuric acid in the aqueous phase is 7 mol / L. The types and contents of metals in the titanium dioxide waste acid are shown in Table 1.

[0046] The organic phase is prepared with 0.1mol / L N,N-dodecylamine di(methylenebenzenephosphite) as the diluent, and the diluent is chloroform. Take 100mL of the organic phase and mix it with 1L of the aqueous phase. The extraction time is 20min and the extraction temperature is 30℃. The concentration of scandium in the raffinate is determined, and the extraction rate of scandium reaches 99.92%. The organic phase loaded with scandium obtained after the extraction of bisphosphonic acid is washed with 6mol / L sulfuric acid solution, and the content of each element in the raffinate is determined. It is found that a large amount of impurity elements such as calcium, iron, chromium, and manganese are removed, which is conducive to the next step of refining. The organic phase loaded with scandium after one washing is washed again with a mixed solution of 1mol / L sodium citrate + 20% H2O2 to obtain an aqueous solution containing scandium ions and an organic phase loaded with titanium. Titanium in the organic phase is stripped with sulfuric acid + H2O2 to recover the titanium in the organic phase. The aqueous phase containing scandium element obtained after the second washing is precipitated with oxalic acid, and the obtained precipitate is separated. The main component of the precipitate is scandium oxalate. The obtained scandium oxalate precipitate is placed in a muffle furnace and calcined at 800°C for 6 hours to obtain a scandium oxide product with a purity greater than 99%.

[0047] Example 6

[0048] The titanium dioxide waste acid is used as the aqueous phase, and the concentration of sulfuric acid in the aqueous phase is 7 mol / L. The types and contents of metals in the titanium dioxide waste acid are shown in Table 1.

[0049] The organic phase is prepared with 0.1mol / L N,N-dodecylamine di(methylenebenzenephosphite) as the diluent, and the diluent is chloroform. Take 100mL of the organic phase and mix it with 1L of the aqueous phase. The extraction time is 20min and the extraction temperature is 40℃. The concentration of scandium in the raffinate is determined, and the extraction rate of scandium reaches 99.21%. The organic phase loaded with scandium obtained after the extraction of bisphosphonic acid is washed with 6mol / L sulfuric acid solution, and the content of each element in the raffinate is determined. It is found that a large amount of impurity elements such as calcium, iron, chromium, and manganese are removed, which is conducive to the next step of refining. The organic phase loaded with scandium after one washing is washed again with a mixed solution of 1mol / L sodium citrate + 20% H2O2 to obtain an aqueous solution containing scandium ions and an organic phase loaded with titanium. Titanium in the organic phase is stripped with sulfuric acid + H2O2 to recover the titanium in the organic phase. The aqueous phase containing scandium element obtained after the second washing is precipitated with oxalic acid, and the obtained precipitate is separated. The main component of the precipitate is scandium oxalate. The obtained scandium oxalate precipitate is placed in a muffle furnace and calcined at 800°C for 6 hours to obtain a scandium oxide product with a purity greater than 98%.

[0050] Table 3

[0051] Extraction temperature E(％) Example 4 15℃ 99.09 Example 1 25℃ 99.49 Example 5 30℃ 99.92 Example 6 40℃ 99.21

[0052] Example 7

[0053] The titanium dioxide waste acid is used as the aqueous phase, and the concentration of sulfuric acid in the aqueous phase is 7 mol / L. The types and contents of metals in the titanium dioxide waste acid are shown in Table 1.

[0054] The organic phase is prepared with 0.1mol / L N,N-dodecylamine di(methylenebenzenephosphite) as the diluent, and the diluent is chloroform. Take 100mL of the organic phase and mix it with 1L of the aqueous phase. The extraction time is 20min and the extraction temperature is 30℃. The concentration of scandium in the raffinate is determined, and the extraction rate of scandium reaches 99.92%. The organic phase loaded with scandium obtained after the extraction of bisphosphonic acid is washed with a 6mol / L sulfuric acid solution. The content of each element in the raffinate is determined, and it is found that a large amount of impurity elements such as calcium, iron, chromium, and manganese are removed, which is conducive to the next step of refining. The organic phase loaded with scandium after the first washing is washed again with a mixed solution of 4mol / L sulfuric acid + 20% H2O2 to obtain an aqueous solution containing scandium ions and an organic phase loaded with titanium. The titanium in the organic phase is stripped with sulfuric acid + H2O2 to recover the titanium in the organic phase. The aqueous phase containing the scandium element obtained after the second washing is precipitated with oxalic acid. The main component of the precipitate is scandium oxalate. The obtained scandium oxalate precipitate is placed in a muffle furnace and calcined at 800°C for 6 hours to obtain a scandium oxide product with a purity greater than 70%.

[0055] Example 8

[0056] The titanium dioxide waste acid is used as the aqueous phase, and the concentration of sulfuric acid in the aqueous phase is 7 mol / L. The types and contents of metals in the titanium dioxide waste acid are shown in Table 1.

[0057] The organic phase is prepared with 0.1mol / L N,N-dodecylamine di(methylenebenzenephosphite) as the diluent, and the diluent is chloroform. Take 100mL of the organic phase and mix it with 1L of the aqueous phase. The extraction time is 20min and the extraction temperature is 30℃. The concentration of scandium in the raffinate is determined, and the extraction rate of scandium reaches 99.92%. The organic phase loaded with scandium obtained after the extraction of bisphosphonic acid is washed with 6mol / L sulfuric acid solution, and the content of each element in the raffinate is determined. It is found that a large amount of impurity elements such as calcium, iron, chromium, and manganese are removed, which is conducive to the next step of refining. The organic phase loaded with scandium after one washing is washed again with a mixed solution of 4mol / L sulfuric acid + 20% H2O2 + sodium phosphate to obtain an aqueous solution containing scandium ions and an organic phase loaded with titanium. Titanium in the organic phase is stripped with sulfuric acid + H2O2 to recover the titanium in the organic phase. The aqueous phase containing scandium element obtained after the second washing is precipitated with oxalic acid, and the obtained precipitate is separated. The main component of the precipitate is scandium oxalate. The obtained scandium oxalate precipitate is placed in a muffle furnace and calcined at 800°C for 6 hours to obtain a scandium oxide product with a purity greater than 78%.

[0058] Example 9

[0059] The titanium dioxide waste acid is used as the aqueous phase, and the concentration of sulfuric acid in the aqueous phase is 7 mol / L. The types and contents of metals in the titanium dioxide waste acid are shown in Table 1.

[0060] The organic phase is prepared with 0.1mol / L N,N-dodecylamine di(methylenebenzenephosphite) as the diluent, and the diluent is chloroform. Take 100mL of the organic phase and mix it with 1L of the aqueous phase. The extraction time is 20min and the extraction temperature is 30℃. The concentration of scandium in the raffinate is determined, and the extraction rate of scandium reaches 99.92%. The organic phase loaded with scandium obtained after the extraction of bisphosphonic acid is washed with a 6mol / L sulfuric acid solution. The content of each element in the raffinate is determined, and it is found that a large amount of impurity elements such as calcium, iron, chromium, and manganese are removed, which is conducive to the next step of refining. The organic phase loaded with scandium after the first washing is washed again with a 20% H2O2+sodium phosphate mixed solution to obtain an aqueous solution containing scandium ions and an organic phase loaded with titanium. The titanium in the organic phase is stripped with sulfuric acid+H2O2 to recover the titanium in the organic phase. The aqueous phase containing the scandium element obtained after the second washing is precipitated with oxalic acid, and the precipitate obtained is separated. The main component of the precipitate is scandium oxalate. The obtained scandium oxalate precipitate is placed in a muffle furnace and calcined at 800°C for 6 hours to obtain a scandium oxide product with a purity greater than 74%.

[0061] Table 4

[0062] Washing liquid composition Scandium Oxide Purity Example 5 <![CDATA[1mol / L Sodium citrate + 20% H2O2]]> 99％ Example 7 <![CDATA[Sulfuric acid + H2O2]]> 70％ Example 8 <![CDATA[4 mol / L sulfuric acid + 20% H2O2 + sodium phosphate]]> 78％ Example 9 <![CDATA[20% H2O2 + Sodium Phosphate]]> 74％

[0063] The present invention obtains an organic phase loaded with scandium by using N,N-dodecylamine di(methylenebenzenephosphite) extractant, washes the organic phase twice with sulfuric acid solution and sodium citrate+H2O2 mixed solution to remove most of the impurity ions, obtains a water phase containing scandium and an organic phase containing titanium, recovers the titanium in the organic phase, precipitates the scandium in the water phase with oxalic acid solution to obtain a scandium oxalate precipitate, and calcines the obtained scandium oxalate solution at high temperature in a muffle furnace to obtain a scandium oxide product with a purity greater than 99%. This operation effectively recovers the scandium titanium in the titanium dioxide waste acid, utilizes waste, and solves the problem of a large amount of titanium dioxide waste acid accumulation. The bisphosphonic acid extractant used in the extraction process has good extraction performance for scandium titanium, and no problems such as three phases and emulsification occur in the extraction process, reduces the loss of the organic phase, and is easy to separate. The synthesis of the extractant is simple, and the reagents used are cheap and readily available. The subsequent washing process abandons multi-stage washing and only requires two washes to effectively separate scandium and titanium, meeting the production requirements of green chemical industry.

Claims

1. A method for recovering scandium titanium from titanium dioxide waste acid using a bisphosphonic acid extractant, characterized in that: Scandium in titanium dioxide waste acid is recovered by extraction, washing, stripping, precipitation and calcination with a bisphosphonic acid extractant, wherein the bisphosphonic acid extractant is N,N-n-dodecylamine di(methylenephenylphosphonic acid), and the process specifically comprises the following steps: (1) A bisphosphonic acid extractant prepared with a diluent is used as an organic phase, wherein the diluent is one of toluene, kerosene, carbon tetrachloride, dichloromethane or chloroform; and the concentration of the bisphosphonic acid extractant in the organic phase is 0.01-1.5 mol / L; (2) Mixing the aqueous phase and the organic phase and stirring for 10 to 30 minutes at an extraction temperature of 10 to 50°C. The mixed solution after extraction is subjected to phase separation to obtain an organic phase loaded with scandium and an extract; (3) washing the organic phase loaded with scandium ions with a sulfuric acid solution having a concentration of 3 to 6 mol / L for preliminary impurity removal; (4) stripping the organic phase after washing with the sulfuric acid solution with a mixed solution of a sodium citrate solution and a hydrogen peroxide solution to obtain an aqueous solution containing scandium ions and an organic phase loaded with titanium; (5) stripping the obtained titanium-loaded organic phase with a mixed solution of sulfuric acid solution and H2O2 solution to recover titanium; the organic phase is reused in the extraction process; (6) precipitating the obtained aqueous solution containing scandium ions with oxalic acid to obtain a precipitate, wherein the main component of the precipitate is scandium oxalate; (7) calcining the obtained precipitate at a temperature of 700-1200° C. to obtain a scandium oxide product with a purity greater than 99%.

2. A method for recovering scandium titanium from titanium dioxide waste acid using a bisphosphonic acid extractant according to claim 1, characterized in that: In the step (1), the concentration of the bisphosphonic acid extractant in the organic phase is 0.05-1 mol / L.

3. A method for recovering scandium titanium from titanium dioxide waste acid using a diphosphonic acid extractant according to claim 1, characterized in that: In the step (2), the extraction time is 10-20 min and the extraction temperature is 20-40°C.

4. The method for recovering scandium titanium from titanium dioxide waste acid using a bisphosphonic acid extractant according to claim 1, characterized in that: In the step (4), the concentration of the sodium citrate solution is 0.01-1 mol / L, and the concentration of the hydrogen peroxide solution is 1%-30%.

5. The method for recovering scandium titanium from titanium dioxide waste acid using a bisphosphonic acid extractant according to claim 1, characterized in that: In the step (5), the concentration of the sulfuric acid solution is 1-10 mol / L, and the concentration of the hydrogen peroxide solution is 1%-30%.

6. The method for recovering scandium titanium from titanium dioxide waste acid using a bisphosphonic acid extractant according to claim 1, characterized in that: In the step (7), the calcination temperature is 800-1000°C.

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