Method for pretreating complex organic waste salt by deep eutectic solvent and application of method

Abstract

The invention belongs to the technical field of wastewater treatment, and particularly relates to a method for pretreating complex organic waste salt with a deep-eutectic solvent and application thereof.The method comprises the steps that a hydrogen bond donor and a hydrogen bond acceptor are prepared through microwave-assisted heating, and the deep-eutectic solvent is prepared; carrying out microwave-assisted mixing on the eutectic solvent and the organic waste salt to prepare a mixed solution; carrying out solid-liquid separation on the mixed solution to obtain wet salt and a solvent; and fully washing the wet salt, and collecting the washing liquid and the salt. The method provided by the invention can remove most of heavy metal ions and organic acids.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and in particular relates to a method for pretreating complex organic waste salts with a low eutectic solvent and an application thereof. Background Art

[0002] In industries such as pharmaceuticals, petrochemicals, printing and dyeing, and coal chemical engineering, the evaporation and concentration of high-concentration saline organic wastewater generates industrial organic waste salts, which pose significant environmental risks. These waste salts contain complex organic pollutants such as benzene series and polycyclic aromatic hydrocarbons, which are highly carcinogenic and ecotoxic. Improper disposal can lead to persistent contamination of the soil-groundwater system through filtration, posing a threat to human health and ecosystem safety.

[0003] The current mainstream organic waste salt treatment technologies, such as high-temperature pyrolysis, salt washing, extraction, and chemical oxidation, all have significant limitations. Although high-temperature pyrolysis can decompose organic matter, it consumes a lot of energy and is prone to equipment corrosion. The salt washing method uses saturated brine for multi-stage washing. Although it is simple to operate, it consumes a lot of water and is difficult to treat waste salt with complex components, while also producing highly polluted wastewater. The extraction method uses volatile solvents such as ethanol or methanol, which poses flammability risks and secondary pollution hazards, and has low efficiency in removing low-concentration or multi-component organic matter. The chemical oxidation method faces the problems of toxic by-product generation and high treatment costs. In response to the demand for treating low-concentration or mixed high-content organic waste salt, it is urgent to develop new technologies that are both green and environmentally friendly, safe and controllable, and resource-recycling, with a focus on breaking through core difficulties such as efficient organic matter removal, zero-emission process design, and low-cost large-scale application.

[0004] In addition, organic waste salts produced under special circumstances often contain heavy metals. These heavy metal ions easily form stable complexes or chelates with organic substances such as amines, phenols, esters, etc. remaining in the organic waste salts. The stability of such bound heavy metals is much higher than that of free ions. Traditional treatment methods are difficult to break their chemical bonds, resulting in difficulty in releasing heavy metals from the organic matrix and low removal efficiency.

[0005] As a green and efficient solvent, deep eutectic solvent (DES) has demonstrated significant advantages in the fields of bioactive ingredient extraction, food processing, pollutant adsorption and desulfurization, electrochemical material preparation, and organic catalytic synthesis. However, it has not yet been effectively applied in the field of resource treatment of industrial waste salt, especially in the pretreatment of waste salt containing organic matter. There is still a technical gap. According to the analysis of currently disclosed Chinese patent technologies, the mainstream processes for waste salt treatment mainly focus on high-temperature pyrolysis carbonization, catalytic oxidation, and single solvent washing, but none of them involve the innovative application of deep eutectic solvents. It is of great value to design suitable deep eutectic solvent hydrogen bond acceptor / donor components, comprehensively control organic and inorganic impurities in organic waste salt, especially heavy metal components, and achieve the harmlessness of salt. Summary of the Invention

[0006] The present invention primarily provides a highly efficient and stable deep eutectic solvent, a method for circulating and sustainably removing heavy metals and organic pollutants from waste salt using this deep eutectic solvent, and its application, to overcome the problems of prior art in removing mixed impurities containing both organic matter and heavy metals, which can easily cause secondary pollution and high costs. The technical solution is as follows:

[0007] A low eutectic solvent for pretreating complex organic waste salts comprises a hydrogen bond acceptor and a hydrogen bond donor; the hydrogen bond acceptor is a polyol, sugar or amino acid; the hydrogen bond donor is a carboxylic acid compound; and the low eutectic solvent is prepared by microwave-assisted heating.

[0008] Furthermore, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1-4.

[0009] Furthermore, the polyol includes one or both of glycerol and ethylene glycol; the sugar includes one or both of glucose and fructose; and the amino acid includes one or both of proline and β-alanine.

[0010] Furthermore, the hydrogen bond donor includes one or more of citric acid, acetic acid, malic acid, and malonic acid.

[0011] A method for pretreating complex organic waste salts with the above-mentioned low eutectic solvent comprises the following steps: preparing a hydrogen bond donor and a hydrogen bond acceptor by microwave-assisted heating to obtain a low eutectic solvent; microwave-assisted mixing the low eutectic solvent and the organic waste salt to obtain a mixed solution; performing solid-liquid separation on the mixed solution to obtain wet salt and solvent; and fully washing the wet salt and collecting the washing solution and salt.

[0012] Furthermore, the mass ratio of the organic waste salt to the low eutectic solvent is 1:1-5.

[0013] Furthermore, the microwave power is 100-200W; the microwave time is 5-10 minutes; the preparation temperature is 50-80°C; the preparation time is 20-60 minutes; the mixing temperature is 40-90°C; and the mixing time is 20-60 minutes.

[0014] Furthermore, the wet salt is placed in methanol at a mass ratio of 1:1 to 1.5 and fully dispersed, and the salt and the washing liquid are separated and collected.

[0015] Furthermore, the solvent and the washing liquid are purified to recover the deep eutectic solvent.

[0016] Furthermore, the purification is to filter the solvent and the washing liquid, and then perform electrodialysis to recover the deep eutectic solvent.

[0017] Ultrafiltration uses an organic solvent-resistant ultrafiltration membrane, including but not limited to polyethersulfone, polyvinylidene fluoride, and ceramic membranes. The ultrafiltration operating pressure is 0.1-0.5 MPa; the temperature is set at 30-60°C; the filtration mode is circulating filtration, with a flow rate of 10-50 mL / min; the membrane stack is configured as a three- or four-chamber stack consisting of a bipolar membrane, an anion exchange membrane, and a cation exchange membrane; the electric field strength is 10-50 V, and the current density is 10-100 mA / cm 2 The operating temperature is 25 to 50°C; the liquid flow rate is 10 to 50 mL / min, and a circulation mode is adopted; the electrolyte is Na2SO4 or NaCl solution; wherein the selected electrolyte concentration is 0.1 to 0.5 mol / L.

[0018] An application of the above-mentioned deep eutectic solvent in wastewater treatment, wherein the organic waste salt contains organic and heavy metal impurities.

[0019] By adopting the above scheme, the method of the present invention has the following advantages:

[0020] 1. The present invention improves the deep eutectic solvent by adopting hydrophilic ligands such as polyols, sugars or amino acid compounds. It takes advantage of the advantages of carboxylic acid group complexation of heavy metals, protonation of organic acids, and competitive hydrogen bonding to adsorb organic acids containing carboxyl or hydroxyl groups. Combined with microwave-assisted configuration and treatment of organic waste salts, it has the characteristics of efficient removal of heavy metal ions and organic acid pollutants, and all components are biodegradable. In particular, it can also have an outstanding removal effect on potassium, calcium, magnesium and other ions that have similar properties to sodium ions and are difficult to separate without affecting the sodium ion concentration.

[0021] 2. The polar carboxylic acid groups contained in the deep eutectic solvent of the present invention have strong coordination ability and can combine with the multiple coordination sites of heavy metal ions to form stable complexes or chelates. At the same time, they provide an acidic environment combined with catalytic active components to promote the chemical transformation of organic acid pollutants, protonate the organic acid pollutants, enhance their electrostatic interaction with hydrogen bond receptors in the deep eutectic solvent, and improve solubility.

[0022] 3. The polyols or sugars in the deep eutectic solvent of the present invention act as hydrogen bond acceptors, selectively dissolving metal oxides by adjusting the polarity of the solvent and the hydrogen bond network.

[0023] 4. Organic acid pollutants containing carboxyl or hydroxyl groups can be embedded in the hydrogen bond network formed by carboxylic acid and polyol / saccharide hydrogen bond acceptors in the deep eutectic solvent of the present invention and captured through competitive hydrogen bonding.

[0024] 5. The present invention utilizes microwaves to improve the uniformity and stability of DES, effectively destroying the π-π stacking effect and hydrophobic interaction between organic pollutant molecules, and improving the dissolution efficiency of organic matter.

[0025] 6. The carboxylic acids, polyols, sugars, and amino acid compounds contained in the raw material components of the low eutectic solvent of the present invention are all natural metabolites or bio-based raw materials. The raw materials are cheap and easily available, have low volatility, low toxicity, are non-flammable, and are biodegradable, thus avoiding the secondary pollution and flammability risks of traditional solvents.

[0026] 7. The deep eutectic solvent of the present invention can be regenerated by bipolar membrane electrodialysis. The solvent loss after regeneration is low and the properties are stable. It can be recycled multiple times, reducing processing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a comparison chart of three types of organic waste salts before and after treatment in Example 1;

[0028] Figure 2 is the TOC removal rate of the deep eutectic solvent of each embodiment on the three waste salts;

[0029] Figure 3 is the TOC removal rate of the deep eutectic solvents for the three waste salts in each control experiment;

[0030] Figure 4 This is a flow chart for the preparation of a deep eutectic solvent;

[0031] Figure 5 Flow chart of treating organic waste salt with low eutectic solvent. DETAILED DESCRIPTION

[0032] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. 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.

[0033] The properties of the organic waste salts in the following examples and control experiments are shown in Table 1:

[0034] Table 1:

[0035]

[0036] Example 1: (1) Glycerol and citric acid were mixed in a reactor at a molar ratio of 1:2, microwaved at a power of 180 W for 6 min, and then placed in a constant temperature water bath at 70°C and stirred at a speed of 300 rpm for 40 min to obtain a deep eutectic solvent;

[0037] (2) The organic waste salt 1 and the low eutectic solvent were mixed in a reactor at a mass ratio of 1:5, microwaved at a power of 200 W for 20 minutes, and then placed in a constant temperature water bath at 70°C and stirred at a speed of 300 r / min for 30 minutes to obtain a mixed solution; the mixed solution was centrifuged at 4500 r / min for 8 minutes to separate the solvent and wet salt;

[0038] (3) adding methanol (1.25 times the mass of waste salt) to the wet salt and stirring at 300 r / min for 10 min; centrifuging at 4500 r / min for 8 min to separate the washing liquid and salt;

[0039] (4) The obtained salt was washed twice according to step (3), and the final salt was placed in a forced air drying oven at 100° C. and dried for 1 hour to obtain a salt with most of the organic matter and impurities removed.

[0040] (5) The solvent and the washing liquid after multiple washings were filtered through a polyethersulfone ultrafiltration membrane at a flow rate of 30 mL / min at 30-60°C and an operating pressure of 0.3 MPa; then, bipolar membrane electrodialysis was performed in a three-chamber or four-chamber membrane stack configured as a bipolar membrane, an anion exchange membrane, and a cation exchange membrane to recover the deep eutectic solvent, wherein the electric field strength was 25 V and the current density was 50 mA / cm 2 ; The operating temperature is 35℃; the liquid flow rate is 30mL / min, and the circulation mode is adopted; the electrolyte is Na2SO4 solution with a concentration of 0.3mol / L.

[0041] The organic waste salts 2 and 3 were treated according to the method of Example 1 for treating the organic waste salt 1. The comparison between the treated organic waste salts 1 to 3 and the original salt is as follows: Figure 1 As shown in the figure, it can be seen that the color of the treated organic waste salt becomes lighter than that of the original salt, indicating that after treatment according to the method of the present invention, most of the colored impurities can be removed intuitively, and the effect is significant.

[0042] Example 2: The difference from Example 1 is that:

[0043] (1) Ethylene glycol and acetic acid were mixed in a reactor at a molar ratio of 1:4, microwaved at a power of 200 W for 6 min, and then placed in a constant temperature water bath at 60°C and stirred at a speed of 300 rpm for 40 min to obtain a deep eutectic solvent;

[0044] (2) The organic waste salt 1 and the low eutectic solvent were mixed in a reactor at a mass ratio of 1:5, microwaved at a power of 200 W for 25 minutes, and then placed in a constant temperature water bath at 40°C and stirred at a speed of 300 r / min for 30 minutes to obtain a mixed solution; the mixed solution was centrifuged at 4500 r / min for 8 minutes to separate the solvent and wet salt.

[0045] Organic waste salt 2 and organic waste salt 3 were treated according to the method of Example 2 for treating organic waste salt 1.

[0046] Example 3: The difference from Example 1 is that:

[0047] (1) Glucose and propionic acid were mixed in a reactor at a molar ratio of 1:5, microwaved at a power of 180 W for 6 min, and then placed in a constant temperature water bath at 60°C and stirred at a speed of 300 rpm for 20 min to obtain a deep eutectic solvent;

[0048] (2) The organic waste salt 1 and the low eutectic solvent were mixed in a reactor at a mass ratio of 1:5, microwaved at a power of 200 W for 25 minutes, and then placed in a constant temperature water bath at 50°C and stirred at a speed of 300 r / min for 30 minutes to obtain a mixed solution; the mixed solution was centrifuged at 4500 r / min for 8 minutes to separate the solvent and wet salt.

[0049] Organic waste salt 2 and organic waste salt 3 were treated according to the method of Example 3 for treating organic waste salt 1.

[0050] Example 4: The difference from Example 1 is that:

[0051] (1) Fructose and acetic acid were mixed in a reactor at a molar ratio of 1:1, microwaved at a power of 100 W for 6 min, and then placed in a constant temperature water bath at 60°C and stirred at a speed of 300 rpm for 40 min to obtain a deep eutectic solvent;

[0052] (2) The organic waste salt 1 and the low eutectic solvent were mixed in a reactor at a mass ratio of 1:5, microwaved at a power of 100 W for 25 minutes, and then placed in a constant temperature water bath at 50°C and stirred at a speed of 300 r / min for 30 minutes to obtain a mixed solution; the mixed solution was centrifuged at 5000 r / min for 6 minutes to separate the solvent and wet salt.

[0053] Organic waste salt 2 and organic waste salt 3 were treated according to the method of Example 4 for treating organic waste salt 1.

[0054] Example 5: The difference from Example 1 is that:

[0055] (1) Proline and malonic acid were mixed in a reactor at a molar ratio of 1:4, microwaved at a power of 180 W for 6 min, and then placed in a constant temperature water bath at 80°C and stirred at a speed of 300 rpm for 40 min to obtain a deep eutectic solvent;

[0056] (2) The organic waste salt 1 and the low eutectic solvent were mixed in a reactor at a mass ratio of 1:5, microwaved at a power of 200 W for 25 minutes, and then placed in a constant temperature water bath at 80°C and stirred at a speed of 300 r / min for 30 minutes to obtain a mixed solution; the mixed solution was centrifuged at 4500 r / min for 8 minutes to separate the solvent and wet salt.

[0057] Organic waste salt 2 and organic waste salt 3 were treated according to the method of Example 5 for treating organic waste salt 1.

[0058] Example 6: The difference from Example 1 is that:

[0059] (1) β-Alanine and malic acid were mixed in a reactor at a molar ratio of 1:3, microwaved at a power of 150 W for 6 min, and then placed in a constant temperature water bath at 75°C and stirred at a speed of 300 rpm for 40 min to obtain a deep eutectic solvent;

[0060] (2) The organic waste salt 1 and the low eutectic solvent were mixed in a reactor at a mass ratio of 1:5, microwaved at a power of 180 W for 25 min, and then placed in a constant temperature water bath at 70°C and stirred at a speed of 300 r / min for 30 min to obtain a mixed solution; the mixed solution was centrifuged at 4500 r / min for 8 min to separate the solvent and wet salt.

[0061] Organic waste salt 2 and organic waste salt 3 were treated according to the method of Example 5 for treating organic waste salt 1.

[0062] Control experiment 1: The difference from Example 1 is:

[0063] (1) Glycerol and citric acid were mixed in a reactor at a molar ratio of 1:2, and then stirred in a 70°C constant temperature water bath at a speed of 300 rpm for 40 min to obtain a deep eutectic solvent;

[0064] (2) The organic waste salt 1 and the low eutectic solvent were mixed in a reactor at a mass ratio of 1:5, and then stirred at a speed of 300 r / min for 30 min in a constant temperature water bath at 70°C to obtain a mixed solution; the mixed solution was centrifuged at 4500 r / min for 8 min to separate the solvent and wet salt.

[0065] Organic waste salt 2 and organic waste salt 3 were treated according to the method of control experiment 1 for treating organic waste salt 1.

[0066] Control experiment 2: The difference from Example 1 is:

[0067] (1) Ethylene glycol and acetic acid were mixed in a reactor at a molar ratio of 1:4, microwaved at a power of 80 W for 20 min, and then placed in a constant temperature water bath at 60°C and stirred at a speed of 300 rpm for 40 min to obtain a deep eutectic solvent;

[0068] (2) The organic waste salt 1 and the low eutectic solvent were mixed in a reactor at a mass ratio of 1:5, microwaved at a power of 80 W for 25 minutes, and then placed in a constant temperature water bath at 40°C and stirred at a speed of 300 r / min for 30 minutes to obtain a mixed solution; the mixed solution was centrifuged at 4500 r / min for 8 minutes to separate the solvent and wet salt.

[0069] Organic waste salt 2 and organic waste salt 3 were treated according to the method of control experiment 2 for treating organic waste salt 1.

[0070] Control experiment 3: The difference from Example 1 is:

[0071] (1) Lauric acid and glycerol were mixed in a reactor at a molar ratio of 1:2, microwaved at a power of 180 W for 6 min, and then placed in a constant temperature water bath at 80°C and stirred at a speed of 300 rpm for 40 min to obtain a deep eutectic solvent;

[0072] (2) The organic waste salt 1 and the low eutectic solvent were mixed in a reactor at a mass ratio of 1:5, microwaved at a power of 200 W for 25 minutes, and then placed in a constant temperature water bath at 60°C and stirred at a speed of 300 r / min for 30 minutes to obtain a mixed solution; the mixed solution was centrifuged at 4500 r / min for 8 minutes to separate the solvent and wet salt.

[0073] Organic waste salt 2 and organic waste salt 3 were treated according to the method of control experiment 3 for treating organic waste salt 1.

[0074] Control experiment 4: The difference from Example 1 is:

[0075] (1) Ethylene glycol and oleic acid were mixed in a reactor at a molar ratio of 1:2, microwaved at a power of 180 W for 6 min, and then placed in a constant temperature water bath at 75°C and stirred at a speed of 300 rpm for 40 min to obtain a deep eutectic solvent;

[0076] (2) The organic waste salt 1 and the low eutectic solvent were mixed in a reactor at a mass ratio of 1:5, microwaved at a power of 200 W for 30 minutes, and then placed in a constant temperature water bath at 60°C and stirred at a speed of 300 r / min for 30 minutes to obtain a mixed solution; the mixed solution was centrifuged at 4500 r / min for 8 minutes to separate the solvent and wet salt.

[0077] Organic waste salt 2 and organic waste salt 3 were treated according to the method of control experiment 4 for treating organic waste salt 1.

[0078] Control experiment 5: The difference from Example 1 is:

[0079] (1) Ethylene glycol and octanoic acid were mixed in a reactor at a molar ratio of 1:1, microwaved at a power of 180 W for 6 min, and then placed in a constant temperature water bath at 60°C and stirred at a speed of 300 rpm for 40 min to obtain a deep eutectic solvent;

[0080] (2) The organic waste salt 1 and the low eutectic solvent were mixed in a reactor at a mass ratio of 1:5, microwaved at a power of 200 W for 25 minutes, and then placed in a constant temperature water bath at 50°C and stirred at a speed of 300 r / min for 30 minutes to obtain a mixed solution; the mixed solution was centrifuged at 4500 r / min for 8 minutes to separate the solvent and wet salt.

[0081] Organic waste salt 2 and organic waste salt 3 were treated according to the method of control experiment 5 for treating organic waste salt 1.

[0082] Control experiment 6: The difference from Example 1 is:

[0083] (1) 1,3-Propanediol and octanoic acid were mixed in a reactor at a molar ratio of 1:1, microwaved at a power of 180 W for 6 min, and then placed in a constant temperature water bath at 60°C and stirred at a speed of 300 rpm for 30 min to obtain a deep eutectic solvent;

[0084] (2) The organic waste salt 1 and the low eutectic solvent were mixed in a reactor at a mass ratio of 1:5, microwaved at a power of 200 W for 25 minutes, and then placed in a constant temperature water bath at 40°C and stirred at a speed of 300 r / min for 30 minutes to obtain a mixed solution; the mixed solution was centrifuged at 4500 r / min for 8 minutes to separate the solvent and wet salt.

[0085] Organic waste salt 2 and organic waste salt 3 were treated according to the method of control experiment 6 for treating organic waste salt 1.

[0086] Example sample test:

[0087] The TOC removal rates of the organic waste salts 1, 2, and 3 in the examples and control experiments were determined as follows: Figure 2 and Figure 3 As shown. Figure 1 and Figure 2 It can be seen that the TOC removal rate of organic waste salts treated with the deep eutectic solvent and method of the present invention is about 90%, while the removal rate of the control experiment is only above 70%, and some data are even less than 50%. This shows that the method of the present invention is also effective in purifying complex organic waste salts containing heavy metals.

[0088] The lower removal rate of the control experiment 1 and the control experiment 2 reflects the importance of the conditions such as the preparation of the eutectic solvent, the microwave-assisted treatment, the presence or absence of the microwave and the power of the microwave on the TOC removal rate. The sharp decrease of the removal rate of the control experiments 3-6 reflects the influence of the selection of the raw materials of the eutectic solvent on the removal rate. The longer chain length is not conducive to the improvement of the TOC removal rate. However, the TOC removal rate of the control experiment 5 of the octanoic acid combination with a relatively short chain length is obviously lower than that of the control experiments 3 and 4 with a longer chain length, which also shows that the chain length is not the only influencing factor, and the unique synergistic relationship between the acceptor and the donor of the hydrogen bond also affects the TOC removal rate. The difference in the TOC removal rate between the control experiments 5 and 6 containing octanoic acid can also support this point. The combination of 1,3-propanediol and octanoic acid is obviously superior to the combination of ethylene glycol and octanoic acid. It is possible that the eutectic solvent of the application forms a unique relationship with the organic matter in the organic waste salt system, that is, even if 1,3-propanediol is similar to ethylene glycol, the final organic removal effect is very different, which shows that the acceptor and the donor of the hydrogen bond must be selected to realize the synergistic effect, and certain substances cannot be directly replaced even if they are similar.

[0089] The XRF characterization results of the organic waste salts 1-3 before and after the treatment of example 1 are shown in tables 2-4.

[0090] Table 2: Organic waste salt 1:

[0091] element Before treatment After processing O 36.9907％ 37.5069％ Cl 27.1133％ 28.4518％ Na 24.3539％ 26.8463％ S 5.9740％ 4.1760％ Cd 1.6172％ 0.1593％ C 1.1286％ 1.7721％ K 0.9165％ 0.0534％ Br 0.6634％ 0.6821％ Ca 0.4883％ 0.0638％ Si 0.2980％ 0.1327％ P 0.1156％ 0.1054％ Fe 0.1003％ 0.0103％ Al 0.0912％ 0.0237％ Mg 0.9158％ 0.0162％

[0092] Table 3: Organic waste salt 2:

[0093] element Before treatment After processing O 15.5068％ 14.5414％ Cl 42.8518％ 44.8739％ Na 36.8463％ 38.3571％ N 0.4466％ 0.1314％ Cu 1.6593％ 0.0142％ C 1.7721％ 1.8497％ Ca 0.0638％ 0.0126％ Al 0.6585％ 0.0825％ S 0.1948％ 0.1372％

[0094] Table 4: Organic waste salt 3:

[0095]

[0096]

[0097] As can be seen from the above tables 2-4, the content of Cd, Cu and Zn elements in the organic waste salt decreases obviously after the treatment, which shows that the method of the application can remove heavy metals. At the same time, the content of K, Mg and Ca elements in the treated organic waste salt also decreases obviously, which shows that the method of the application has obvious removal effect on K, Mg, Ca and other alkali metal ions similar to sodium ions, solves the problem that such alkali metal ions are difficult to separate from sodium ions, makes the remaining NaCl salt purer, is conducive to promoting the further purification of the NaCl salt, reducing the purification cost and promoting the resource utilization.

[0098] Those skilled in the art can make various other corresponding changes and deformations based on the technical solutions and concepts described above, and all of these changes and deformations should fall within the scope of protection of the claims of the present invention.

Claims

1. A deep eutectic solvent for pretreating complex organic waste salts, characterized in that: The invention comprises a hydrogen bond acceptor and a hydrogen bond donor; the hydrogen bond acceptor is a polyol, sugar or amino acid; the hydrogen bond donor is a carboxylic acid compound; and a low eutectic solvent is prepared by microwave-assisted heating.

2. The deep eutectic solvent for treating complex organic waste salts according to claim 1, characterized in that The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1-4.

3. The deep eutectic solvent for treating complex organic waste salts according to claim 1, characterized in that The polyol includes one or both of glycerol and ethylene glycol; the sugar includes one or both of glucose and fructose; and the amino acid includes one or both of proline and β-alanine.

4. The deep eutectic solvent for treating complex organic waste salts according to claim 1, characterized in that The hydrogen bond donor includes one or more of citric acid, acetic acid, malic acid, and malonic acid.

5. A method for pretreating complex organic waste salts with a deep eutectic solvent according to any one of claims 1 to 4, characterized in that: The following steps are involved: A hydrogen bond donor and a hydrogen bond acceptor are prepared by microwave-assisted heating to obtain a low eutectic solvent; the low eutectic solvent and organic waste salt are mixed by microwave-assisted heating to obtain a mixed liquid; the mixed liquid is subjected to solid-liquid separation to obtain wet salt and solvent; the wet salt is fully washed, and the washing liquid and salt are collected.

6. The method for pretreating complex organic waste salts with a deep eutectic solvent according to claim 5, characterized in that: The mass ratio of the organic waste salt to the deep eutectic solvent is 1:1-5.

7. The method for pretreating complex organic waste salts with a deep eutectic solvent according to claim 5, characterized in that: The microwave power is 100-200W; the microwave time is 5-10 minutes; the preparation temperature is 50-80°C; the preparation time is 20-60 minutes; the mixing temperature is 40-90°C; and the mixing time is 20-60 minutes.

8. The method for pretreating complex organic waste salts with a deep eutectic solvent according to claim 5, characterized in that: The wet salt is fully dispersed in methanol at a mass ratio of 1:1 to 1.5, and the salt and washing liquid are separated and collected.

9. The method for pretreating complex organic waste salts with a deep eutectic solvent according to claim 5, characterized in that: The solvent and washing liquid are purified to recover the deep eutectic solvent.

10. Use of the deep eutectic solvent according to any one of claims 1 to 4 in wastewater treatment, characterized in that: The organic waste salt contains organic and heavy metal impurities.

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