阅读说明：本技术 一种利用铁化合物从高浓度盐酸体系中脱除氟离子的方法 (Method for removing fluoride ions from high-concentration hydrochloric acid system by using iron compound ) 是由 杨梦薇 杨瑞甫 赖育河 于 2020-03-31 设计创作，主要内容包括：本发明提供了一种利用铁化合物从高浓度盐酸体系中脱除氟离子的方法,向高浓度盐酸体系中加入铁化合物,与氟离子形成含氟的大基团络合阴离子,再用强碱型阴离子交换树脂脱除大基团络合阴离子。本方法脱氟效率高。(The invention provides a method for removing fluorinion from a high-concentration hydrochloric acid system by using an iron compound. The method has high defluorination efficiency.)

1. A method for removing fluoride ions from a high-concentration hydrochloric acid system by using an iron compound is characterized by comprising the following steps: adding iron compound into hydrochloric acid system, forming fluorine-containing macro-group complex anion with fluorinion, and then removing the macro-group complex anion by strong base type anion exchange resin.

2. The method of claim 1 for removing fluoride ions from a high concentration hydrochloric acid system using an iron compound, wherein: the method comprises the following steps:

s1, adding an iron compound into the high-concentration hydrochloric acid system, and stirring for dissolving;

s2, adsorbing the solution processed in the step S1 by using strong base anion exchange resin.

3. The method of claim 2 for removing fluoride ions from a high concentration hydrochloric acid system using an iron compound, wherein: the iron compound is one or more of ferric oxide, ferric chloride, ferric nitrate, ferric sulfate and ferric phosphate.

4. The method of claim 3 for removing fluoride ions from a high concentration hydrochloric acid system using an iron compound, wherein: the iron compound is used in an amount to ensure Fe³⁺And F^-In a molar ratio of 3: 4.

5. The method of claim 3 for removing fluoride ions from a high concentration hydrochloric acid system using an iron compound, wherein: the strong base anion exchange resin is selected from any one of styrene resin, acrylic resin, phenolic resin, epoxy resin or vinylpyridine resin.

6. The method for removing fluoride ions from a highly concentrated hydrochloric acid system as claimed in claim 5, wherein: the mass concentration of the hydrochloric acid in the high-concentration hydrochloric acid system is 1-38%.

7. The method for removing fluoride ions from a highly concentrated hydrochloric acid system as claimed in claim 6, wherein: the mass concentration of the hydrochloric acid in the high-concentration hydrochloric acid system is 20-30%.

8. The method for removing fluoride ions from a highly concentrated hydrochloric acid system as claimed in claim 2, wherein: the strong base anion exchange resin needs to be pretreated into Cl-type exchange resin before use.

9. The method for removing fluoride ions from a highly concentrated hydrochloric acid system as claimed in claim 2, wherein: the linear velocity of the solution passing through the strong base type anion exchange resin is 0.5-2 mm/s.

Technical Field

The invention relates to a method for removing fluoride ions from a high-concentration hydrochloric acid system by using an iron compound, belonging to the technical field of treatment of lithium hexafluorophosphate synthesis tail gas.

Background

From the first half of the twentieth century, with the progress of science and technology, human society has entered a rapid development stage, and the demand for energy has also become greater and greater, and fossil fuel as primary energy has played an immeasurable role in human development so far, but human also faces the problem of energy exhaustion and environmental pollution from this, and the search for alternative novel clean energy becomes a common challenge facing human beings. In the twenty-first century, development and utilization of new energy have been made, and in particular, lithium ion batteries have been successfully used in the fields of traditional 3C (computers, cameras, mobile phones, etc.), electric industry (e.g., electric vehicles), energy storage, etc.

Lithium hexafluorophosphate, a key raw material of lithium ion batteries, has been industrially produced. Lithium hexafluorophosphate has various synthesis methods, such as a gas-solid reaction method, an HF solvent method, an organic solvent method, an ion exchange method and the like, and only an anhydrous hydrogen fluoride non-aqueous solvent method among the above methods has been successfully industrialized. The electrolytic fluorine preparation process of Nissan Kanto electrochemical technology and the phosphorus pentachloride process of Sendai chemical (Morita) in the anhydrous hydrogen fluoride non-aqueous solvent method have respective unique advantages, wherein the phosphorus pentachloride method has the advantages of simple equipment, concise circuit, low cost and the like, and is adopted by most manufacturers.

In the process for synthesizing lithium hexafluorophosphate by the phosphorus pentafluoride method, the main reactions are as follows:

PCl₅+5HF→PF₅+5HCl

it can be seen that along with the progress of the synthesis reaction, a large amount of synthesis tail gas is often generated, and the components of the tail gas mainly comprise hydrogen chloride, hydrogen fluoride and phosphorus pentafluoride, wherein the hydrogen chloride is generated by the reaction of phosphorus pentachloride and hydrogen fluoride, the phosphorus pentafluoride is generated by incomplete reaction of lithium fluoride and phosphorus pentafluoride, and the hydrogen fluoride is generated by entrainment of the hydrogen chloride and low-boiling-point gasification of the hydrogen fluoride. For the mixed tail gas with complex composition, the current practice of industrial production is to treat the mixed tail gas by a multistage water washing and alkali washing method, which not only causes great hydrogen fluoride loss, low raw material utilization rate and cost rise, but also generates great amount of industrial hazardous wastes, requires special treatment of qualified manufacturers, and further causes cost rise.

According to statistics, about one ton of anhydrous hydrogen fluoride enters a three-waste system along with tail gas when one ton of lithium hexafluorophosphate is produced, and the annual hydrogen fluoride loss of a 1000 ton/year lithium hexafluorophosphate production line exceeds ten million yuan RMB. Therefore, it is an object of the present invention to provide a method for efficiently recovering and utilizing components in exhaust gas.

The mixed acid generated by recovering the lithium hexafluorophosphate tail gas is subjected to dephosphorization and defluorination treatment to form the mixed acid mainly containing hydrochloric acid, wherein the mixed acid still contains about 100ppm of fluoride ions, so that the secondary industrial utilization of the recovered hydrochloric acid is influenced, the content of the fluoride ions in the mixed acid is further reduced, and the mixed acid becomes an important bottleneck for expanding the industrial application field of the recovered hydrochloric acid. The research on a method for removing fluoride ions in high-concentration hydrochloric acid and converting mixed acid into high-purity hydrochloric acid enables the recovered hydrochloric acid to meet the standards of most industrial applications, and becomes a direct cause of the research.

There have been a large number of studies on the treatment of industrial wastewater containing fluorine, and some of the studies have been applied, for example, in the literature [1]]As described above, although there is a certain progress in the treatment of wastewater containing fluorine in high-concentration hydrochloric acid, for example, documents [2 to 3]]Said, but still drawbacks exist. For example, document [2]]High-concentration fluorine-containing hydrochloric acid is treated by precipitation with calcium salt, fluorosilicate, etc., wherein the content of fluorine ions can be reduced to about 0.1%. Document [3]Using calcium salts, e.g. CaCl₂、Ca(OH)₂Etc. by adjusting the pH value, using CaF₂The fluorine removal agent has low solubility in water, achieves the aim of removing fluorine, and has the highest defluorination rate of about 50 percent within the range of 20-50 ppm of fluorine-containing ions. However, in acidic environments, especially high acid concentrations, e.g. acid concentrations>The solubility of CaF2 increases greatly at 10%, and the final fluoride content can reach hundreds or even thousands of ppm, making it difficult to remove fluoride in acidic systems. In addition, the method of adsorbing fluorine ions in water by attaching the adsorbent to a carrier is also a common method for removing fluorine, such as using activated alumina as a fluorine-removing adsorbent for removing fluorine ions in drinking water. Such as document [4]]Using an aluminum-containing compound or silica gel (SiO)₂) As matrix, rare earth oxide CeO₂-TiO₂Removal of fluoride ions from waste water by anion exchange for coatings, e.g. in the literature [5, 6]]The oxides used in these methods have a good defluorination effect and a long service life in a nearly neutral solution, but in a strong acid environment, the oxides used react with acid to generate chloride which gradually dissolves, so that they cannot be used reliably for a long time. There are also silica gel-type adsorbents as a fluorine ion remover, as described in documents [7, 8]]However, in an acidic environment, silica gel reacts with HF to gradually form a colloid which is dissolved in the solution, resulting in unreliable long-term use.

[1] Gah of han gazetty. fluorine-containing wastewater treatment method [ J ] organic fluorine industry, 2005 (3): 27-36

[2] Process for defluorinating fluoric hydrochloric acid [ J ] organic fluorine industry, 2007 (4): 49-51

[3] Experimental study on defluorination of coal gasified concentrated salt low-fluorine wastewater from Wandong of SaJuntao Sun Erimo Palma [ J ] coal processing and comprehensive utilization, 2017(4)59-73

[4] Study on adsorption and defluorination performance of Lirong Fulvo Likuaiguay [ J ] Water supply technology, 2018, 12(1), 21-23,27

[5] Northeast university a method for removing fluorine from bastnaesite sulphuric acid leach liquor using an aluminium-containing adsorbent [ P ]. china: 102936656A, 2013-02-20.

[6] King of China, Wang Dongta, Chenxia and the like, and the principle and the method of the adsorption method fluorine removal technology [ J ] environmental science and management, 2008, 33(8): 121-.

[7] Senwei, Sunwhongyan, Lizhengyong, etc. research on the method for removing fluorine and chlorine from zinc oxide fume [ J ] Yunnan metallurgy, 2013, 42(6)

[8] Preparation of novel activated alumina and analytical study of adsorption defluorination Property of Shihaiping [ D ]. Suzhou: Suzhou institute of science and technology, 2010

[9] Experimental study on defluorination with Al-type strongly acidic cation exchange resin [ J ] Qizihaer university, 2000,16(4):87-89

[10] Development of application research of rare earth compounds in water body defluorination technology [ J ] chemical industry and engineering, 1999,16(5):286-

Disclosure of Invention

The invention provides a method for removing fluoride ions from a high-concentration hydrochloric acid system by using an iron compound, which can effectively solve the problems.

The invention is realized by the following steps:

a process for removing the fluorion from high-concentration hydrochloric acid system by use of iron compound includes such steps as adding iron compound to hydrochloric acid system, reacting with fluorion to form fluorion macro-group complex anion, and removing said macro-group complex anion by strong-alkali anionic exchange resin.

As a further improvement, the method comprises the following steps:

s1, adding an iron compound into the hydrochloric acid system, and stirring for dissolving;

s2, adsorbing the solution processed in the step S1 by using strong base anion exchange resin.

As a further improvement, the iron compound is one or more of ferric oxide, ferric chloride, ferric nitrate, ferric sulfate and ferric phosphate. They can be dissolved in high-concentration hydrochloric acid to form stable macro-group complex anions with fluorine ions, so that the fluorine ions can be effectively removed.

As a further improvement, the iron compound is used in an amount to ensure Fe³⁺And F^-In a molar ratio of 3: 4. At this ratio, Fe³⁺And F^-Can form stable Fe₃F₄ ^-The macro-group complex anion can use strong base anion exchange resin to perform effective ion exchange, thereby achieving the aim of defluorination.

In a further improvement, the strong base anion exchange resin is selected from any one of styrene resin, acrylic resin, phenolic resin, epoxy resin or vinylpyridine resin.

As a further improvement, the mass concentration of the hydrochloric acid in the high-concentration hydrochloric acid system is 1-38%.

As a further improvement, the mass concentration of the hydrochloric acid in the high-concentration hydrochloric acid system is 20-30%. In the optimal acidity range, the strong base type anion exchange resin has higher efficiency of removing the large-group fluorinion, and the volatilization of the hydrogen chloride can be controlled in a smaller range in the implementation process.

As a further improvement, the strong base anion exchange resin needs to be pretreated into Cl-type exchange resin before being used.

As a further improvement, the linear velocity of the solution passing through the strong base anion exchange resin is 0.5-2 mm/s. The linear velocity is critical, and the defluorination efficiency is high in the range, the liquid treatment speed is too slow below the linear velocity, and the defluorination efficiency is seriously reduced after the liquid treatment speed exceeds the linear velocity.

The invention has the beneficial effects that:

1. the invention adds iron compound into high-concentration hydrochloric acid system, the iron compound can be dissolved in high-concentration hydrochloric acid, and forms fluorine-containing large-group complex anion with fluorinion, then uses strong-base anion exchange resin to remove the large-group complex anion, the large-group anion in the solution forms a solvolysis layer on the outer layer of the group, and the solvent on the outer layer is easy to remove when ion exchange occurs, thus ion exchange can be completed in high-concentration acid, the defluorination efficiency is high, the technical problem that the fluorinion is difficult to remove from high-concentration hydrochloric acid in the prior art is well solved, and the invention can be applied to removing the fluorinion in lithium hexafluorophosphate tail gas. The defluorination efficiency of the method is as high as 98.04%.

2. According to the invention, the iron compound is added into the hydrochloric acid system to form fluorine-containing large-group complex anions with fluoride ions, and then the large-group complex anions are removed by using strong-base anion exchange resin, so that compared with the traditional calcium salt precipitation method, the problem that the solubility of the precipitate in high-concentration hydrochloric acid is increased and the effective defluorination is difficult is avoided.

3. According to the invention, the iron compound is added into the hydrochloric acid system to form fluorine-containing large-group complex anions with fluoride ions, and then the large-group complex anions are removed by using the strong-base anion exchange resin, so that compared with the traditional aluminum-containing compound or silica gel adsorption method, the problem that chemical reaction occurs in an acidic environment to influence the defluorination effect is avoided, and the defluorination efficiency is high.

4. The strong base type anion exchange resin adopted by the invention is a common ion exchange resin, has already been industrially and standardly produced, has the advantages of high efficiency, low cost, simple and convenient operation, long service life and the like, and meets the basic requirements of industrial application reliability, long service life and the like.

5. The strong base anion exchange resin adopted by the invention can be regenerated and recycled by a method known in the industry.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 shows F in the original solution in the highly concentrated hydrochloric acid system of example 1 of the present invention^-Ion chromatogram of concentration.

FIG. 2 shows F after treatment with ion exchange resin in the high concentration hydrochloric acid system of example 1 of the present invention^-Ion chromatogram of concentration.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings of the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.