A method for selective extraction of fluorine from aqueous solution containing fluorine based on complex extraction

Abstract

The application discloses a method for selectively extracting fluorine from a fluorine-containing aqueous solution based on complex extraction, which comprises the following steps: (1) adding a fluorine complex cation to the fluorine-containing aqueous solution to obtain a solution containing metal-fluorine complex ions; and (2) mixing a saponified organic phase with the solution containing the metal-fluorine complex ions and separating phases to obtain a fluorine-loaded organic phase and a raffinate after fluorine removal. The method can achieve the purpose of deep fluorine removal.

Description

Technical Field

[0001] This invention relates to the technical field of efficient and clean metallurgy of primary minerals, concentrates and secondary resources, and particularly to a method for selectively extracting and removing fluoride from fluoride-containing aqueous solutions. Background Technology

[0002] The leaching solutions, zinc electrolytes, pyrolusite acid leaching solutions, and wet-process phosphoric acid solutions used in the recycling process of waste ternary lithium battery cathode materials all contain small amounts of fluoride, with concentrations ranging from 10 to 5000 μg / mL. However, the preparation of battery-grade nickel-cobalt-manganese sulfate, high-purity electrolytic zinc, and food-grade or higher phosphoric acid has strict requirements on fluoride content. In March 2020, the Beijing Resource Compulsory Recycling Environmental Protection Industry Technology Innovation Strategic Alliance released the latest group standard for battery-grade sulfate solutions, which sets higher requirements for fluoride content in battery-grade sulfate solutions: the upper limit for fluoride content in battery-grade nickel and cobalt sulfate solutions is 4 mg / L (superior grade), and for first-grade solutions: 10 mg / L for cobalt sulfate, 15 mg / L for nickel sulfate, and 50 mg / L for manganese sulfate solution (superior grade), and 100 mg / L (first-grade).

[0003] Existing aqueous solution defluorination technologies are mainly aimed at removing fluoride from wastewater in hydrometallurgical and chemical industries. Typical examples of existing aqueous solution defluorination technologies include precipitation and resin adsorption for deep purification of fluoride-containing wastewater, adsorption for deep defluorination in electrolytic zinc sulfate solution, and extraction for defluorination in wet phosphoric acid. However, these methods are only effective for the aqueous solutions they treat, and there are still many challenges in defluorination of battery-grade nickel-cobalt-manganese sulfate solutions: (1) Precipitation introduces impurities such as calcium and magnesium ions; flocculation precipitation leads to the loss of nickel, cobalt, and manganese metals and secondary hazardous waste; (2) Adsorption has limited adsorbent cycles and is complicated to operate, and some adsorbents introduce impurity ions; (3) Neutral phosphorus solvent extraction is only effective for free HF and is ineffective for complexed ions such as fluorine-silicon, fluorine-aluminum, and fluorine-calcium, making it difficult to meet the 15 mg / L requirement; (4) Ion exchange consumes a lot of water for resin regeneration, and the regenerated liquid is difficult to treat. The feed liquid needs to be de-oiled before entering the ion exchange. In summary, directly applying existing aqueous solution defluorination technologies to battery-grade sulfate solution defluorination still suffers from problems such as high cost, insufficient defluorination depth, and impurity contamination. Table 1 below provides a brief comparison of aqueous solution defluorination technologies.

[0004] Table 1. Brief Comparison of Fluoride Removal Technologies in Aqueous Solutions

[0005]

[0006] Therefore, how to achieve selective and deep removal of fluoride from fluoride-containing aqueous solutions has become a pressing technical problem to be solved in the non-ferrous metal hydrometallurgical industry. Summary of the Invention

[0007] In view of the difficulties faced by traditional fluoride-containing aqueous solution defluorination technology, the purpose of this invention is to overcome the shortcomings of the existing technology and provide a new technology for highly adaptable, highly selective, and deep extraction defluorination.

[0008] To achieve the above objectives, the present invention proposes a method for selectively removing fluoride from fluoride-containing aqueous solutions based on complexation extraction, comprising the following steps:

[0009] (1) Add fluorine complex cations to a fluorine-containing aqueous solution to obtain a solution containing metal-fluorine complex ions;

[0010] (2) The saponified organic phase is mixed with a solution containing metal-fluorine complex ions and the phases are separated to obtain a fluorine-loaded organic phase and a raffinate after fluorine removal.

[0011] Preferably, the fluoride content in the fluoride salt solution is 0.01 g / L to 10 g / L, and the pH value ranges from 0.1 to 7.

[0012] Preferably, the fluorine complex cation in step (1) includes Al 3+ La 3+ Ce 4+ Ce 3+ 、Sm 3+ Eu 3+ Y 3+ One or more of them.

[0013] Preferably, the organic phase in step (2) consists of an extractant, a modifier, and a diluent.

[0014] The extractant includes one or more of P204, P507, Cyanex272, Vorsatic911, and Vorsatic10, and the concentration of the extractant is 3-95%.

[0015] The modifier includes one or more of isooctanol, sec-octanol, ethyl acetate, N235, TBP, and TOPO;

[0016] The diluent includes one or more of sulfonated kerosene, No. 260 solvent oil, or aviation kerosene.

[0017] Preferably, the concentration of the extractant is 5-50%.

[0018] Preferably, the extraction process in step (2) has 1 to 10 extraction stages; when the number of extraction stages is greater than or equal to 2, the extraction method is countercurrent extraction; during the extraction process, the volume flow ratio of the organic phase to the aqueous phase is 1 / 10 to 10 / 1.

[0019] Preferably, the method further includes:

[0020] The fluorine-loaded organic phase is back-extracted using an acid solution or an acid solution containing fluorine complex metal ions to obtain a fluorine-enriched back-extractant and a back-extracted organic phase; wherein the fluorine complex metal ions include Al 3+ Fe 3+ Ce 4+ Zr 4+ La 3+ Ce 3+ Y 3+ One or more of the following; the acid solution includes an aqueous solution of at least one inorganic acid selected from sulfuric acid, nitric acid, and hydrochloric acid; the H in the acid solution + The concentration of the fluorine complex is 0.5–4.0 mol / L, and the concentration of the fluorine complex metal ion is 0.01–1.0 mol / L.

[0021] Preferably, before back-extraction, the fluorine-loaded organic phase is pre-washed; the washing solution is water or a dilute acid solution; during the washing process, the H+ of the dilute acid solution is... + The molar amount is less than or equal to the molar amount of metal ions in the fluorine-loaded organic phase.

[0022] Preferably, the number of back-extraction stages in the back-extraction process is 1 to 10; when the number of back-extraction stages is greater than or equal to 2, the back-extraction method is countercurrent back-extraction; during the back-extraction process, the volume flow ratio of the fluorine-loaded organic phase to the acid solution is 1 / 1 to 15 / 1.

[0023] Preferably, the organic phase obtained from the back-extraction process is returned to step (2) for extraction and defluorination after being treated with liquid alkali saponification.

[0024] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0025] The method of this invention can reduce the fluoride content in the solution to 1-15 ppm, the organic phase can be regenerated, and the amount of wastewater generated throughout the process is small. Detailed Implementation

[0026] To better understand the present invention, the present invention will be further described below through specific embodiments, but the listed embodiments do not limit the scope of protection of the present invention.

[0027] Example 1

[0028] The aqueous feed solution contained Ni 55.35 g / L, Co 11.47 g / L, Mn 22.65 g / L, F 0.2051 g / L, and had a pH of 5.10. 0.5 g / L, 1.0 g / L, 1.5 g / L, and 2.0 g / L of [Al] were added to the feed solution, respectively. 3+The organic phase was 15% P2O4 + 10% 2-octanol + 75% sulfonated kerosene, and extraction was performed at room temperature for 15 min with an O / A ratio of 1:1. The extraction rates of fluorine in the aqueous phase were 65.4%, 80.1%, 92.0%, and 94.2%, respectively; the fluorine concentrations in the raffinate were 0.071 g / L, 0.040 g / L, 0.0164 g / L, and 0.012 g / L, respectively.

[0029] Example 2

[0030] The aqueous feed solution contained Ni 55.47 g / L, Co 12.50 g / L, Mn 21.76 g / L, F 0.2170 g / L, and had a pH of 4.89. 0.5 g / L and 1.0 g / L of [Ce] were added to the feed solution, respectively. 4+ The pH was adjusted to below 0.1, and an organic phase of 15% P2O4 + 10% sec-octanol + 75% sulfonated kerosene was used. Extraction was performed at room temperature for 15 min with an O / A ratio of 1:1. The extraction rates of fluoride in the aqueous phase were 54.3% and 76.2%, respectively, and the fluoride concentrations in the raffinate were 0.099 g / L and 0.051 g / L, respectively.

[0031] Example 3

[0032] The aqueous feed solution contained Ni 55.47 g / L, Co 12.50 g / L, Mn 21.76 g / L, F 0.2170 g / L, and had a pH of 4.89. 2.0 g / L, 4.0 g / L, and 5.0 g / L of [Fe] were added to the feed solution respectively. 3+ The pH was adjusted to below 2.0, and an organic phase of 15% P2O4 + 15% TBP + 70% sulfonated kerosene was used. Extraction was performed at room temperature for 15 min with an O / A ratio of 1:1. The extraction rates of fluoride in the aqueous phase were 71.3%, 93.2%, and 97.5%, respectively, and the fluoride concentrations in the raffinate were 0.062 g / L, 0.015 g / L, and 0.005 g / L, respectively.

[0033] Example 4

[0034] The aqueous feed solution contained Ni 45.37 g / L, Co 24.35 g / L, Mn 15.02 g / L, and F 0.523 g / L, with a pH of 5.09. 2.0 g / L of [Al] was added to the feed solution. 3+ ], 5.5 g / L [Fe 3+ ], 1.5g / L[Ce 4+ The organic phase was 20% P507 + 15% N235 + 65% sulfonated kerosene, and extraction was performed at room temperature for 15 min with an O / A ratio of 1:1. The extraction rates of fluorine in the aqueous phase were 97.2%, 96.4%, and 90.3%, respectively, and the fluorine concentrations in the raffinate were 0.014 g / L, 0.019 g / L, and 0.051 g / L, respectively.

[0035] Example 5

[0036] The aqueous feed solution contained Ni 45.37 g / L, Co 24.35 g / L, Mn 15.02 g / L, and F 0.523 g / L, with a pH of 5.09. 2.0 g / L of [Al] was added to the feed solution. 3+ ], 5.5 g / L [Fe 3+ ], 1.5g / L[Ce 4+ The pH was adjusted to below 2.0, and an organic phase of 25% Cyanex 272 + 15% ethyl acetate + 60% sulfonated kerosene was used. Extraction was performed at room temperature for 15 min with an O / A ratio of 1:1. The extraction rates of fluoride in the aqueous phase were 96.5%, 94.2%, and 88.9%, respectively, and the fluoride concentrations in the raffinate were 0.018 g / L, 0.030 g / L, and 0.058 g / L, respectively.

Claims

1. A method for selectively removing fluoride from a fluoride-containing aqueous solution based on complexation extraction, characterized in that, The method includes the following steps: (1) A solution containing metal-fluorine complex ions is obtained by adding fluorine-containing aqueous solution to a fluorine-containing aqueous solution, wherein the fluorine-containing aqueous solution contains nickel, cobalt and manganese, and the fluorine content is 0.01 g / L to 10 g / L, and the pH value is in the range of 0.1-7; the fluorine complex ions include Al 3+ La 3+ Ce 4+ Ce 3+ 、Sm 3+ Eu 3+ Y 3+ One or more of them; (2) The saponified organic phase is mixed with a solution containing metal-fluorine complex ions and the phases are separated to obtain a fluorine-loaded organic phase and a raffinate after fluorine removal; The organic phase described in step (2) consists of an extractant, a modifier, and a diluent. The extractant includes one or more of P204, P507, Cyanex272, Vorsatic911, and Vorsatic10, and the concentration of the extractant is 3-95%. The modifier includes one or more of isooctanol, sec-octanol, ethyl acetate, N235, TBP, and TOPO; The diluent includes one or more of sulfonated kerosene, No. 260 solvent oil, or aviation kerosene.

2. The method as described in claim 1, characterized in that, The concentration of the extractant is 5-50%.

3. The method as described in claim 1, characterized in that, The extraction process in step (2) has 1 to 10 extraction stages; when the number of extraction stages is greater than or equal to 2, the extraction method is countercurrent extraction; during the extraction process, the volume flow ratio of the organic phase to the aqueous phase is 1:10 to 10:

1.

4. The method according to any one of claims 1 to 3, characterized in that, The method further includes: The fluorine-loaded organic phase is back-extracted using an acid solution or an acid solution containing fluorine complex metal ions to obtain a fluorine-enriched back-extractant and a back-extracted organic phase; wherein the fluorine complex metal ions include Al 3+ Fe 3+ Ce 4+ Zr 4+ La 3+ Ce 3+ Y 3+ One or more of the following; the acid solution includes an aqueous solution of at least one inorganic acid selected from sulfuric acid, nitric acid, and hydrochloric acid; the H in the acid solution + The concentration of the fluorine complex is 0.5~4.0 mol / L, and the concentration of the fluorine complex metal ion is 0.01~1.0 mol / L.

5. The method as described in claim 4, characterized in that, Before back-extraction, the fluorine-loaded organic phase is pre-washed; the washing solution is water or a dilute acid solution; during the washing process, the H+ in the dilute acid solution... + The molar amount is less than or equal to the molar amount of metal ions in the fluorine-loaded organic phase.

6. The method as described in claim 4, characterized in that, The number of back-extraction stages in the back-extraction process is 1 to 10; when the number of back-extraction stages is greater than or equal to 2, the back-extraction method is countercurrent back-extraction; during the back-extraction process, the volume flow ratio of the fluorine-loaded organic phase to the acid solution is 1:1 to 15:

1.

7. The method as described in claim 4, characterized in that, The back-extracted organic phase obtained in the back-extraction process is returned to step (2) for extraction and defluorination after being treated with liquid alkali saponification.

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