A method for treating FEC production wastewater

Abstract

The present invention relates to a method for treating FEC production wastewater, comprising: S1, adding a strong base to the wastewater and raising the temperature and pressure to 120-160°C and 120-160 kPa; S2, reducing the pressure to atmospheric pressure and then adding NaAlO2 powder and Ca(OH)2. This method overcomes the technical barriers to removing FEC, fluoride ions, and chloride ions from FEC production wastewater, a lithium battery electrolyte additive, and achieves a pretreatment process with COD concentrations below 500 ppm, fluoride ion concentrations below 50 ppm, and chloride ion concentrations below 1500 ppm.

Description

Technical Field

[0001] The present invention belongs to the field of environmental protection and relates to a pretreatment process for industrial wastewater, and specifically to a pretreatment process for wastewater produced by the production of FEC (fluoroethylene carbonate), a lithium battery electrolyte additive. Background Art

[0002] Lithium batteries are an emerging industry. As a crucial component of the new energy sector, global demand for them continues to grow annually as their applications expand. Key technologies for lithium-ion batteries include positive and negative electrode materials, electrolytes, separators, and membrane electrodes. The electrolyte is composed of three ingredients: a solvent (carbonate products, accounting for over 80%), a lithium salt (lithium hexafluorophosphate), and additives (such as VC and FEC).

[0003] With the widespread application of lithium-ion batteries, the research on electrolytes is also developing rapidly. Adding a small amount of non-energy storage substances to the electrolyte can effectively improve certain battery properties, such as battery capacity, cycle efficiency, cycle life, safety performance, etc. These substances are called additives. Since the fluorine element has a strong electron-withdrawing effect, it is beneficial to increase the reduction potential of solvent molecules on the surface of the carbon negative electrode, optimize the solid electrolyte interface film, improve the compatibility between the electrolyte and the active material, and thus stabilize the electrochemical properties of the electrode. At the same time, the flash point of organic fluorine compounds is very high, which improves the safety performance of lithium battery electrolytes. FEC (fluoroethylene carbonate) is widely used as an additive in lithium-ion battery electrolytes. The production of these lithium battery electrolyte additives often uses ethylene carbonate as a raw material. Chlorine or other chlorinating agents are used to chlorinate to produce monochloroethylene carbonate, and then fluorinated with a fluorinating agent to generate FEC, which will then produce a high concentration of F. - 、Cl - , FEC wastewater, this type of wastewater has the characteristics of complex composition, high salt content, irregular discharge, etc. The COD concentration in the wastewater is about 4000-5000 mg / L, the fluoride ion concentration is about 800-1200 mg / L, and the chloride ion concentration is about 8000-11000 mg / L. How to decompose the FEC in this type of wastewater, F - 、Cl - Meeting treatment standards is a pain point in the treatment of FEC wastewater, an electrolyte additive for lithium batteries.

[0004] Through the search of publicly published literature, there are few studies in this area. No relevant research papers or patents have been found to report on how to treat the wastewater produced by the production of FEC, an additive for the lithium battery electrolyte. It is necessary to explore treatment technologies on our own. - 、Cl -NaAlO2, CaO and other agents are added to remove FEC, but FEC cannot be decomposed, the fluorine contained in FEC cannot be removed, and COD cannot be degraded. This type of wastewater is deeply treated to achieve COD, F - 、Cl - The need to meet emission standards will become more urgent. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for treating FEC production wastewater, which solves the problem of excessive fluoride ions and chloride ions in wastewater produced by the production of such lithium battery electrolyte additives.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The present invention provides a method for treating FEC production wastewater, which comprises:

[0008] S1. Add strong alkali to the wastewater and increase the temperature and pressure to 120-160°C and 120-160kPa respectively;

[0009] S2. After reducing to normal pressure, add NaAlO2 powder and Ca(OH)2.

[0010] Preferably, the strong base added in S1 is NaOH powder.

[0011] Preferably, NaAlO2 and Ca(OH)2 in S2 are Al 3+ , Ca 2+ Add in a molar ratio (4-6):1.

[0012] Furthermore, the S2 is added to make Al in water 3+ 、Cl - The ratio is (6-8):1.

[0013] Preferably, said S1 and / or said S2 further includes a stirring step.

[0014] Furthermore, the step S1 is stirred for 16-20 hours, and the step S2 is stirred for 2-4 hours.

[0015] Preferably, it also includes:

[0016] S3, add PAC solution to S2 wastewater and stir for 1-1.5h;

[0017] S4. Add PAM solution to the S3 wastewater and stir for 20-30 minutes, then discharge the precipitate.

[0018] Furthermore, the concentration of the PAC solution added in S3 is 5-10%, and the addition amount is 4000-6000 ppm. The concentration of the PAM solution added in S4 is 1-2‰, and the addition amount is 300-500 ppm.

[0019] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0020] The lithium battery electrolyte solvent production wastewater pretreatment process of the present invention breaks through the technical barrier of difficult removal of FEC, fluoride ions and chloride ions in the production wastewater of lithium battery electrolyte additive FEC, and can achieve the pretreatment process purpose of COD concentration less than 500ppm, fluoride ion concentration less than 50ppm, and chloride ion concentration less than 1500ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0022] Figure 1 It is a step diagram of a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0025] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] like Figure 1 A method for treating FEC production wastewater is shown, comprising:

[0027] S1. Add NaOH powder to the wastewater at a dosage of 5-10 g / L (5-10 g of NaOH powder per 1 L of wastewater), raise the temperature and pressure, and stir thoroughly for 16-20 hours. After heating and increasing the temperature and pressure, the temperature is 120-160°C and the pressure is 120-160 kPa;

[0028] After the wastewater S2 and S1 is decompressed to normal pressure, NaAlO2 powder and Ca(OH)2 powder are added. NaAlO2 and Ca(OH)2 are added according to the pressure of Al 3 + , Ca 2+ The molar ratio (4-6): 1 is added, and after adding, Al 3+ 、Cl - The ratio is (6-8): 1, stir thoroughly for 2-4 hours, and use calcium hydroxide and the Ca in sodium aluminate to 2+ 、Al 3+ and Cl in high-chloride wastewater - The reaction generates an insoluble precipitate Ca2Al(OH)6Cl, and the main reaction equation is as follows: 2Ca(OH)2+AlO2 - +Cl - →Ca2Al(OH)6Cl↓+2OH - , 2F - +Ca 2+ →CaF2↓,F - + Al 3+ →AlF 2+ ↓+ AlF3↓+ AlF 4- ↓+ AlF5 2- ↓+ AlF6 3- ↓;

[0029] S3, add PAC solution to the S2 wastewater, the concentration of the added PAC solution is 5-10%, the addition amount is 4000-6000ppm, and stir thoroughly for 1-1.5h;

[0030] S4. Add PAM solution to the S3 wastewater. The concentration of the added PAM solution is 1-2‰, the addition amount is 300-500ppm, stir thoroughly for 20-30min, and discharge the precipitate.

[0031] Ca was introduced into S2 2+ To remove Cl - Remove F at the same time - , a co-precipitation effect is produced between the two, which better separates mud and water.

[0032] There is no particular limitation on the stirring time, and other stirring times are also possible. However, better results can be achieved by using the above stirring time.

[0033] The technical solutions and effects of the present invention are described in detail below through examples and comparative examples.

[0034] The wastewater (raw water) used below has a COD concentration of approximately 5,000 mg / L, a fluoride ion concentration of approximately 1,000 mg / L, and a chloride ion concentration of approximately 10,000 mg / L.

[0035] Example 1 (Multiple parallel tests, each test was performed many times, and the data was averaged)

[0036] Take a 2L beaker and add 1000mL of raw water, raise the temperature to 120℃, increase the pressure to 120kPa, add 5g of NaOH powder, and stir for 16h; add 60g of NaAlO2 powder and 15g of Ca(OH)2 powder, stir for 2h, add 10mL of 5% concentration PAC solution, stir for 1h, add 3mL of 2‰ concentration PAM solution, stir for 30min, discharge the precipitate and take the supernatant for testing.

[0037] Example 2 (multiple parallel tests)

[0038] Take a 2L beaker and add 1000mL of raw water, raise the temperature to 160℃, increase the pressure to 160kPa, add 5g of NaOH powder, and stir for 16h; add 60g of NaAlO2 powder and 15g of Ca(OH)2 powder, stir for 2h, add 10mL of 5% concentration PAC solution, stir for 1h, add 3mL of 2‰ concentration PAM solution, stir for 30min, discharge the precipitate and take the supernatant for testing.

[0039] Example 3 (multiple parallel tests)

[0040] Take a 2L beaker and add 1000mL of raw water, raise the temperature to 160℃, increase the pressure to 160kPa, add 5g of NaOH powder, and stir for 20h; add 60g of NaAlO2 powder and 15g of Ca(OH)2 powder, stir for 4h, add 10mL of 5% concentration PAC solution, stir for 1h, add 3mL of 2‰ concentration PAM solution, stir for 30min, discharge the precipitate and take the supernatant for testing.

[0041] Example 4 (multiple parallel tests)

[0042] Take a 2L beaker and add 1000mL of raw water, raise the temperature to 160℃, increase the pressure to 160kPa, add 10g of NaOH powder, and stir for 20h; add 80g of NaAlO2 powder and 20g of Ca(OH)2 powder, stir for 4h, add 10mL of 5% concentration PAC solution, stir for 1h, add 3mL of 2‰ concentration PAM solution, stir for 30min, discharge the precipitate and take the supernatant for testing.

[0043] Comparative Example 1 (multiple parallel tests)

[0044] Take a 2L beaker and add 1000mL of raw water. Without increasing the temperature or pressure, add 5g of NaOH powder and stir for 16h; add 60g of NaAlO2 powder and 15g of Ca(OH)2 powder and stir for 2h. Add 10mL of 5% concentration PAC solution and stir for 1h. Add 3mL of 2‰ concentration PAM solution and stir for 30min. After discharging the precipitate, take the supernatant for testing.

[0045] Comparative Example 2 (multiple parallel tests)

[0046] Take a 2L beaker and add 1000mL of raw water, raise the temperature to 80℃, do not increase the pressure, add 10g of NaOH powder, and stir for 20h; add 80g of NaAlO2 powder and 20g of Ca(OH)2 powder, stir for 4h, add 10mL of 5% concentration PAC solution, stir for 1h, add 3mL of 2‰ concentration PAM solution, stir for 30min, discharge the precipitate and take the supernatant for testing.

[0047] Comparative Example 3 (multiple parallel tests)

[0048] Take a 2L beaker and add 1000mL of raw water, raise the temperature to 180℃, increase the pressure to 180kPa, add 10g of NaOH powder, and stir for 20h; add 80g of NaAlO2 powder and 20g of Ca(OH)2 powder, stir for 4h, add 10mL of 5% concentration PAC solution, stir for 1h, add 3mL of 2‰ concentration PAM solution, stir for 30min, discharge the precipitate and take the supernatant for testing.

[0049] The test results are as follows: after multiple parallel tests, the COD concentration of Example 1 is about 1500 mg / L, the removal rate is about 70%, the fluoride ion concentration is about 100 mg / L, the removal rate is about 90%, and the chloride ion concentration is about 2500 mg / L, and the removal rate is about 75%; the COD concentration of Example 2 is about 800 mg / L, the removal rate is about 84%, the fluoride ion concentration is about 100 mg / L, the removal rate is about 90%, and the chloride ion concentration is about 2500 mg / L, and the removal rate is about 75%; the COD concentration of Example 3 is about 450 mg / L, the removal rate is about 91%, the fluoride ion concentration is about 100 mg / L, the removal rate is about 90%, and the chloride ion concentration is about 2500 mg / L, and the removal rate is about 75%; the COD concentration of Example 4 is about 450 mg / L, the removal rate is about 91%, the fluoride ion concentration is about 50 mg / L, the removal rate is about 95%, the chloride ion concentration is about 1500 mg / L, and the removal rate is about 85%; the COD concentration of Comparative Example 1 is 3500 mg / L, the removal rate was about 30%, the fluoride ion concentration was about 500 mg / L, the removal rate was about 50%, and the chloride ion concentration was about 2500 mg / L, the removal rate was about 75%; in Comparative Example 2, the COD concentration was about 1700 mg / L, the removal rate was about 66%, the fluoride ion concentration was about 200 mg / L, the removal rate was about 80%, and the chloride ion concentration was about 1500 mg / L, the removal rate was about 85%; in Comparative Example 3, the COD concentration was about 1200 mg / L, the removal rate was about 76%, the fluoride ion concentration was about 150 mg / L, the removal rate was about 85%, and the chloride ion concentration was about 1500 mg / L, the removal rate was about 85%. The test results show that heating, pressurizing, and stirring under alkaline conditions have a great impact on the removal of FEC.

[0050] The lithium battery electrolyte solvent production wastewater pretreatment process of the present invention breaks through the technical barrier of difficult removal of FEC, fluoride ions and chloride ions in the production wastewater of lithium battery electrolyte additive FEC, and can achieve the pretreatment process purpose of COD concentration less than 500ppm, fluoride ion concentration less than 50ppm, and chloride ion concentration less than 1500ppm.

[0051] The process has the following advantages: the process route of the invention is simple, the treatment effect is outstanding, the impact resistance is strong, the process control parameters are relatively few and can be quantified, and the automated operation is easy to achieve, which reduces the safety risks of daily operation. The types of reagents used are conventional and the operating cost is low.

[0052] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for treating FEC production wastewater, characterized in that: It includes: S1, adding strong alkali to the wastewater and increasing the temperature and pressure. The temperature after heating is 120-160℃, and the pressure after increasing is 120-160kPa; S2, after reducing the pressure to normal pressure, adding NaAlO2 powder and Ca(OH)2. NaAlO2 and Ca(OH)2 are in the form of Al 3+ , Ca 2+ The molar ratio (4-6): 1 is added until Al 3+ 、Cl - The ratio is (6-8):1; The strong base added in S1 is NaOH powder, and the addition amount of the NaOH powder is 5-10 g / L.

2. The method for treating FEC production wastewater according to claim 1, wherein: Said S1 and / or said S2 further comprises a stirring step.

3. The method for treating FEC production wastewater according to claim 2, wherein: The S1 is stirred for 16-20 hours, and the S2 is stirred for 2-4 hours.

4. The FEC production wastewater treatment method according to claim 1, characterized in that: Also includes: S3, add PAC solution to S2 wastewater and stir for 1-1.5h; S4. Add PAM solution to the S3 wastewater and stir for 20-30 minutes, then discharge the precipitate.

5. The method for treating FEC production wastewater according to claim 4, wherein: The concentration of the PAC solution added in S3 is 5-10%, and the addition amount is 4000-6000ppm. The concentration of the PAM solution added in S4 is 1-2‰, and the addition amount is 300-500ppm.

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