A pretreatment process for wastewater from the production of lithium battery electrolyte solvent containing EO

Abstract

The present invention relates to a pretreatment process for wastewater containing EO (Ethylene Oxide) from the production of lithium battery electrolyte solvents. The process comprises: first, adding acid to the wastewater to acidify it to a pH of 2-3 and heating the wastewater to 50-60°C; then, adding hydrogen peroxide and bubbling ozone into the wastewater, with the ratio of hydrogen peroxide to EO by mass being 1:(20-30); finally, adding alkali to the wastewater and using a flocculant to precipitate and remove the precipitate. This process overcomes the technical barriers to biodegradable and deep COD pretreatment of EO (toxic substances) in lithium battery electrolyte solvent production wastewater, achieving a COD pretreatment process of less than 500 ppm. After pretreatment, the wastewater enters a biochemical treatment system for deep removal of COD, ammonia nitrogen, and total nitrogen.

Description

Technical Field

[0001] The present invention belongs to the field of environmental protection and relates to a process for pretreating industrial wastewater, and specifically to a process for pretreating wastewater produced from a lithium battery electrolyte solvent containing EO (ethylene oxide). 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 rapid development of lithium-ion batteries, carbonates such as dimethyl carbonate, ethyl methyl carbonate, and ethylene carbonate have been widely used as solvents in lithium-ion battery electrolytes due to their excellent properties. Furthermore, with the recent surge in the number of non-phosgene-based polycarbonate plants commissioned in the past two years, dimethyl carbonate has become a widespread alternative to phosgene as a carbonylation reagent. However, the production of these lithium-ion battery electrolyte solvents often uses ethylene oxide (EO) as a raw material, which in turn generates difficult-to-degrade production wastewater characterized by complex composition, toxicity, high salinity, irregular discharge, and strong corrosiveness. Due to the non-biodegradability of this wastewater, it has long been a pain point in wastewater treatment for the EO-containing lithium-ion battery electrolyte solvent industry.

[0004] A search of publicly available literature revealed that the Chinese patent document "CN106673275A" (A method and apparatus for treating organic wastewater containing ethylene oxide derivatives) mentions that the wastewater containing EO is subjected to coagulation and sedimentation followed by Fenton oxidation and iron-carbon micro-electrolysis oxidation to degrade the EO. This method produces a large amount of salt and hazardous waste sludge. The service life of the iron-carbon is limited during operation, and the hazardous waste treatment of the old iron-carbon after replacement is less economical for treating EO, and the process flow is also more complicated. Chinese patent document "CN104773928A" (a method for treating wastewater from propylene oxide production) mentions that wastewater containing propylene oxide (which has similar properties to EO) ​​is first subjected to biochemical treatment and then to Fenton oxidation to achieve the degradation of propylene oxide. This method ignores the toxicity of propylene oxide itself, which poses an obstacle to biochemical treatment. The treatment of propylene oxide is mainly guaranteed by Fenton oxidation at the end. This method has problems such as a long process flow, difficulty in stabilizing the operation of biochemical treatment, and the generation of a large amount of salt by Fenton oxidation, which is accompanied by the production of hazardous waste sludge.

[0005] Domestic research and engineering applications for the treatment of this type of wastewater are mainly based on Fenton oxidation. With the increasingly stringent wastewater discharge standards and the rising prices of chemicals and hazardous waste treatment, the Fenton method of treating this type of water will gradually become less applicable, and the demand for deep treatment of this type of wastewater to achieve COD discharge standards will become more urgent. Summary of the Invention

[0006] The purpose of the present invention is to provide a pretreatment process for EO-containing lithium battery electrolyte solvent production wastewater, which solves the problem that COD in lithium battery electrolyte solvent production wastewater is difficult to biodegrade and exceeds the standard.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] The present invention provides a pretreatment process for wastewater produced by the production of EO-containing lithium battery electrolyte solvents, which comprises:

[0009] First, acid is added to the wastewater to make it acidic with a pH of 2-3 and the temperature is raised to 50-60°C.

[0010] Then, hydrogen peroxide and ozone are added to the wastewater, and the ratio of hydrogen peroxide to EO mass content is 1: (20-30);

[0011] Finally, alkali is added to the wastewater and flocculants are used to precipitate and remove the precipitate.

[0012] Preferably, the acid added to the wastewater is concentrated sulfuric acid.

[0013] Preferably, the concentration of the hydrogen peroxide solution added is 20-30%, and the mixture is stirred for 0.5-1 hour, and the temperature is lowered to no more than 40°C.

[0014] Preferably, the dosage of ozone is 300-500 ppm, and the mixture is stirred thoroughly for 3-4 hours.

[0015] Preferably, the alkali added is Ca(OH)2.

[0016] Furthermore, Ca(OH)2 is an emulsion, the concentration of the Ca(OH)2 emulsion is 5-10%, it is fully stirred for 1-2 hours, and the pH value is maintained at 9-10.

[0017] Preferably, the flocculant used is PAM, the concentration of the PAM solution is 1-2‰, the mixture is fully stirred for 20-30 minutes, and the precipitate is discharged.

[0018] Preferably, the ORP value of the wastewater is maintained at 350-400 mV when hydrogen peroxide is added and ozone is bubbled in.

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

[0020] The EO-containing lithium battery electrolyte solvent production wastewater pretreatment process of the present invention breaks through the technical barriers of non-biodegradable EO (toxic substances) and deep degradation of COD pretreatment in lithium battery electrolyte solvent production wastewater, and can achieve the pretreatment process goal of COD less than 500ppm. After pretreatment, the wastewater enters the biochemical treatment system for deep removal of COD, ammonia nitrogen and total nitrogen. 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. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are 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 the 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 The pretreatment process for EO-containing lithium battery electrolyte solvent production wastewater shown includes:

[0027] S1. Add concentrated H2SO4 to the wastewater, maintain the pH value at 2-3, heat to 50-60℃ and stir thoroughly for 20-24h;

[0028] S2. Add H2O2 solution to the S1 wastewater, with a concentration of 20-30% and a ratio of 1:(20-30) (i.e., the range of 1:20 to 1:30, which is the ratio of the mass of H2O2 contained in the H2O2 solution to the mass of EO contained in the wastewater), stir thoroughly for 0.5-1h, and maintain the ORP value at 350-400mV;

[0029] S3, add O3 into the S2 wastewater at a dosage of 300-500ppm, stir thoroughly for 3-4h, and reduce the temperature to no more than 40℃;

[0030] S4. Add Ca(OH)2 emulsion to the S3 wastewater. The concentration of Ca(OH)2 emulsion is 5-10%, the dosage is 100-300ppm, stir thoroughly for 1-2h, and maintain the pH value at 9-10.

[0031] S5. Add PAM solution to the S4 wastewater at a concentration of 1-2‰ and a dosage of 50-70ppm. Stir thoroughly for 20-30 minutes and discharge the precipitate. Anionic flocculants are preferred for PAM.

[0032] In S1, the wastewater undergoes high-temperature acid hydrolysis to hydrolyze cyclic substances into alcohols. Heating the temperature to 50-60°C is an optimal time for engineering implementation. If the temperature is too high, energy consumption will increase, while if the temperature is too low, the reaction time will be long.

[0033] Ozone and hydrogen peroxide work synergistically to produce hydroxyl radicals with extremely strong oxidizing effects, and the addition of hydrogen peroxide will promote the generation of hydroxyl radicals.

[0034] The technical solutions and effects of the present invention are described in detail below through examples and comparative examples.

[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 (the COD concentration in the raw water is about 7000mg / L, the EO concentration is about 1000mg / L, the fluoride ion concentration is about 300 mg / L, and the TP concentration is about 80 mg / L), raise the temperature to 50℃, adjust the acid to pH 3, and stir for 20h; add 20% H2O2 solution at a dosage of 30ppm (the mass ratio with EO is 1:30, and the EO concentration is about 1000ppm), and stir for 0.5h; bubble O3 into the beaker at a dosage of 300ppm and stir for 3h; add 5% Ca(OH)2 emulsion at a dosage of 100ppm and stir for 1h; add 2‰ PAM solution at a dosage of 50ppm and stir for 30min; after discharging the precipitate, take the supernatant for testing.

[0037] Example 2 (multiple parallel tests)

[0038] Take a 2L beaker and add 1000mL of raw water (the COD concentration in the raw water is about 7000mg / L, the EO concentration is about 1000mg / L, the fluoride ion concentration is about 300mg / L, and the TP concentration is about 80mg / L), raise the temperature to 50℃, adjust the acid to pH 2, and stir for 20h; add 30% H2O2 solution at a dosage of 50ppm (with an EO mass content ratio of 1:20, and an EO concentration of about 1000ppm), and stir for 0.5h; bubble O3 into the beaker at a dosage of 500ppm and stir for 4h; add 10% Ca(OH)2 emulsion at a dosage of 100ppm and stir for 1h; add 2‰ PAM solution at a dosage of 50ppm and stir for 30min; after discharging the precipitate, take the supernatant for testing.

[0039] Example 3 (multiple parallel tests)

[0040] Take a 2L beaker and add 1000mL of raw water (the COD concentration in the raw water is about 7000mg / L, the EO concentration is about 1000mg / L, the fluoride ion concentration is about 300 mg / L, and the TP concentration is about 80 mg / L), raise the temperature to 60℃, adjust the acid to pH 2, and stir for 20h; add 30% H2O2 solution at a dosage of 50ppm (the mass content ratio with EO is 1:20, and the EO concentration is about 1000ppm), and stir for 0.5h; bubble O3 into the beaker at a dosage of 500ppm and stir for 4h; add 10% Ca(OH)2 emulsion at a dosage of 100ppm and stir for 1h; add 2‰ PAM solution at a dosage of 50ppm and stir for 30min; after discharging the precipitate, take the supernatant for testing.

[0041] Comparative Example 1 (multiple parallel tests)

[0042] Take a 2L beaker and add 1000mL of raw water (the COD concentration in the raw water is about 7000mg / L, the EO concentration is about 1000mg / L, the fluoride ion concentration is about 300 mg / L, and the TP concentration is about 80 mg / L), without heating or adjusting the acid or alkali, and stir for 20h; add 20% H2O2 solution at a dosage of 50ppm (the mass ratio with EO is 1:20, and the EO concentration is about 1000ppm), and stir for 0.5h; bubble O3 into the beaker at a dosage of 300ppm and stir for 3h; add 5% Ca(OH)2 emulsion at a dosage of 100ppm and stir for 1h; add 2‰ PAM solution at a dosage of 50ppm and stir for 30min; after discharging the precipitate, take the supernatant for testing.

[0043] Comparative Example 2 (multiple parallel tests)

[0044] Take a 2L beaker and add 1000mL of raw water (the COD concentration in the raw water is about 7000mg / L, the EO concentration is about 1000mg / L, the fluoride ion concentration is about 300 mg / L, and the TP concentration is about 80 mg / L), raise the temperature to 30℃, adjust the acid to pH 2, and stir for 20h; add 30% H2O2 solution at a dosage of 50ppm (the mass ratio with EO is 1:20, and the EO concentration is about 1000ppm), and stir for 0.5h; bubble O3 into the beaker at a dosage of 500ppm and stir for 4h; add 10% Ca(OH)2 emulsion at a dosage of 100ppm and stir for 1h; add 2‰ PAM solution at a dosage of 50ppm and stir for 30min; after discharging the precipitate, take the supernatant for testing.

[0045] Comparative Example 3 (multiple parallel tests)

[0046] Take a 2L beaker and add 1000mL of raw water (the COD concentration in the raw water is about 7000mg / L, the EO concentration is about 1000mg / L, the fluoride ion concentration is about 300 mg / L, and the TP concentration is about 80 mg / L), raise the temperature to 70℃, adjust the acid to pH 2, and stir for 20h; add 30% H2O2 solution at a dosage of 50ppm (the mass ratio with EO is 1:20, and the EO concentration is about 1000ppm), and stir for 0.5h; bubble O3 into the beaker at a dosage of 500ppm and stir for 4h; add 10% Ca(OH)2 emulsion at a dosage of 100ppm and stir for 1h; add 2‰ PAM solution at a dosage of 50ppm and stir for 30min; after discharging the precipitate, take the supernatant for testing.

[0047] The test results are as follows: after multiple parallel tests, the COD concentration of Example 1 is about 2500 mg / L, the EO concentration is about 400 mg / L, the fluoride ion concentration is about 100 mg / L, and the TP concentration is about 30 mg / L; the COD concentration of Example 2 is about 800 mg / L, the EO concentration is about 50 mg / L, the fluoride ion concentration is about 30 mg / L, and the TP concentration is about 10 mg / L; the COD concentration of Example 3 is about 450 mg / L, the EO concentration is about 0 mg / L, the fluoride ion concentration is about 30 mg / L, and the TP concentration is about 10 mg / L; the COD concentration of Comparative Example 1 is about 5500 mg / L, the EO concentration is about 900 mg / L, the fluoride ion concentration is about 100 mg / L, and the TP concentration is about 30 mg / L; the COD concentration of Comparative Example 2 is about 2800 mg / L, the EO concentration is about 350 mg / L, and the fluoride ion concentration is about 30 The COD concentration of Comparative Example 3 was about 550 mg / L, the EO concentration was about 10 mg / L, the fluoride ion concentration was about 30 mg / L, and the TP concentration was about 10 mg / L. According to the test results, heating and stirring under acidic conditions has a great influence on the COD degradation rate.

[0048] Among them, the test results are as follows: after multiple parallel tests, the COD degradation rate of Example 1 is about 64%, and the EO degradation rate is about 75%, the COD degradation rate of Example 2 is about 89%, and the EO degradation rate is about 96%, the COD degradation rate of Example 3 is about 94%, and the EO degradation rate is about 100%, the COD degradation rate of Comparative Example 1 is about 15%, and the EO degradation rate is about 10%, the COD degradation rate of Comparative Example 2 is about 60%, and the EO degradation rate is about 65%, and the COD degradation rate of Comparative Example 3 is about 92%, and the EO degradation rate is about 99%. According to the test results, heating and stirring under acidic conditions has a great influence on the COD degradation rate.

[0049] The lithium battery electrolyte solvent production wastewater pretreatment process of the present invention breaks through the technical barriers of non-biodegradable EO (toxic substances) in lithium battery electrolyte solvent production wastewater and deep degradation of COD pretreatment, and can achieve the pretreatment process goal of COD less than 500ppm. After pretreatment, the wastewater enters the biochemical treatment system for deep removal of COD, ammonia nitrogen and total nitrogen.

[0050] 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.

[0051] 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 pretreatment process for wastewater from production of EO-containing lithium battery electrolyte solvents, characterized in that it include: First, acid is added to the wastewater to make it acidic with a pH of 2-3 and the temperature is raised to 50-60°C. Then, hydrogen peroxide and ozone are added to the wastewater, the ratio of hydrogen peroxide dosage to EO mass content is 1: (20-30), the concentration of hydrogen peroxide solution added is 20-30%, and it is fully stirred for 0.5-1h, and the temperature is reduced to no more than 40℃; Finally, add alkali to the wastewater and use flocculants to precipitate and remove the precipitate. The alkali added is Ca(OH)2, which is an emulsion. The concentration of the Ca(OH)2 emulsion is 5-10%. Stir thoroughly for 1-2 hours and maintain the pH value at 9-10.

2. The EO-containing lithium battery electrolyte solvent production wastewater pretreatment process according to claim 1, characterized in that: The acid added to the wastewater is concentrated sulfuric acid.

3. The pretreatment process for EO-containing lithium battery electrolyte solvent production wastewater according to claim 1, characterized in that: The dosage of ozone is 300-500ppm, and it is stirred thoroughly for 3-4 hours.

4. The pretreatment process for EO-containing lithium battery electrolyte solvent production wastewater according to claim 1, characterized in that: The flocculant used is PAM, the concentration of PAM solution is 1-2‰, stir thoroughly for 20-30 minutes, and discharge the precipitate.

5. The pretreatment process for EO-containing lithium battery electrolyte solvent production wastewater according to claim 1, characterized in that: When hydrogen peroxide is added and ozone is injected, the ORP value of the wastewater is maintained at 350-400mV.

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