Multi-stage treatment method for coal chemical sewage

Abstract

The invention relates to a multistage treatment method for coal chemical sewage, and belongs to the technical field of wastewater treatment. The organic matter removal agent in the multistage treatment method of the coal chemical sewage has a good removal effect on various organic matters (including lipophilic organic matters such as volatile phenol, thiophene, pyridine, quinoline, furan, naphthalene, anthracene and phenanthrene and hydrophilic organic matters such as carbazole, indole and pyrrole) in the coal chemical sewage with different pH values. The multistage treatment method for the coal chemical sewage is insensitive to the pH value of the wastewater, has wide applicability, can treat various wastewater with different pH values, omits the pretreatment step, and reduces the treatment cost. The dimethyl carbonate and the amidoxime substances in the organic matter removal agent in the multistage treatment method for the coal chemical sewage have a synergistic effect, and the dimethyl carbonate and the amidoxime substances are used together to play the synergistic effect, so that the removal rate of various organic matters in the coal chemical sewage is increased.

Description

Technical Field

[0001] The present invention relates to a multi-stage treatment method for coal chemical wastewater, belonging to the technical field of wastewater treatment. Background Art

[0002] Since the energy utilization rate of direct coal combustion is low, coal is converted to maximize the utilization of its energy. The conversion of coal means liquefying or gasifying it through physical, chemical and other changes. This conversion process is called coal chemical technology, including coal coking, coal liquefaction and low-temperature coal carbonization, etc. Coal chemical wastewater has a large discharge volume and complex wastewater components, and it is a kind of refractory industrial wastewater, which contains a large amount of oil, phenol, ammonia nitrogen and heterocyclic compounds (phenol, quinoline, amine, naphthalene, pyridine, anthracene, phenanthrene, etc.). At the same time, coal chemical wastewater has the characteristics of high waste concentration, high toxicity and poor biodegradability.

[0003] The main method for recycling organic wastes in coal chemical wastewater is solvent extraction. For example, Chinese patent document CN119455450A discloses a coal chemical wastewater deoiling extractant and its preparation method and application. The coal chemical wastewater deoiling extractant includes at least one of petroleum ether, aromatic hydrocarbon compounds and acid ester organic compounds. However, this deoiling extractant is mainly used to remove oil pollutants in coal chemical wastewater. Chinese patent document CN118718469A discloses a safe and efficient phenol-removing and oil-removing extractant and its application. The phenol-removing and oil-removing extractant includes a combination of a main extractant and a co-extractant. The main extractant includes a combination of oxime compounds and ketone compounds, and the co-extractant includes any one or at least two combinations of alcohol compounds, ether compounds and aliphatic hydrocarbons. However, when using this phenol-removing and oil-removing extractant, the pH of coal chemical wastewater needs to be adjusted to 5 to improve the waste removal efficiency, and the removal effect of this phenol-removing and oil-removing extractant on hydrophilic organic compounds such as carbazole, indole and pyrrole is poor. Summary of the Invention

[0004] The purpose of the present invention is to provide a multi-stage treatment method for coal chemical wastewater to solve the problems that the pH of wastewater needs to be adjusted when using an extractant to remove organic matters in coal chemical wastewater and the removal effects of hydrophilic organic compounds such as carbazole, indole and pyrrole in the wastewater are poor.

[0005] The present invention provides a multi-stage treatment method for coal chemical wastewater, including the following steps: subjecting the coal chemical wastewater to sedimentation treatment to obtain sedimentation wastewater; then mixing the sedimentation wastewater and an organic matter removing agent in a mass ratio of 3-4:1, standing for layering, and removing the organic phase to obtain oil-removed wastewater; finally removing metal cations in the oil-removed wastewater to obtain purified water; the organic matter removing agent is composed of dimethyl carbonate and amidoxime substances in a mass ratio of 6-9:1-3, and the structure of the amidoxime substances is as follows:

[0006]

[0007] Among them, R1 is methylene or ethylene, and R2 is a unit represented by Formula 1, Formula 2 or Formula 3;

[0008]

[0009] Preferably, the preparation method of the amidoxime substance is as follows: reacting keto-diacid with thionyl chloride to obtain keto-diacyl chloride; reacting keto-diacyl chloride with iminodiacylonitrile to obtain a keto-diamide dinitrile compound; finally reacting the keto-diamide dinitrile compound with hydroxylamine hydrochloride to obtain the amidoxime substance; the keto-diacid is α-ketoglutaric acid, 2-ketosuccinic acid or 4-ketoheptanoic acid; the iminodiacylonitrile is iminodiacetonitrile or β,β'-iminodipropionitrile.

[0010] Preferably, the temperature for the reaction of the keto-diacid with thionyl chloride is 65-75 °C, and the time is 8-10 h.

[0011] Preferably, the molar ratio of the keto-diacid to thionyl chloride is 1:4-5.

[0012] Preferably, the molar ratio of the keto-diacyl chloride to iminodiacylonitrile is 1:2.

[0013] Preferably, the temperature for the reaction of the keto-diacyl chloride with iminodiacylonitrile is -5-2 °C, and the time is 5-7 h.

[0014] Preferably, the method for the reaction of the keto-diamide dinitrile compound with hydroxylamine hydrochloride is as follows: adjusting the pH of the hydroxylamine hydrochloride methanol solution to 7.5-8.5, then adding the keto-diamide dinitrile compound, and then mixing and reacting at 80-85 °C for 2-3 h, and obtaining the amidoxime substance after impurity removal.

[0015] Preferably, the molar ratio of the keto-diamide dinitrile compound to hydroxylamine hydrochloride is 1:4.2-4.5.

[0016] Preferably, the coal chemical industry wastewater contains volatile phenol, thiophene, pyridine, quinoline, carbazole, indole, furan, pyrrole, naphthalene, anthracene, phenanthrene.

[0017] Preferably, the pH of the settled wastewater is 5-10.5.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) The organic matter remover in the multi-stage treatment method of coal chemical industry wastewater of the present invention contains dimethyl carbonate and amidoxime substances. Dimethyl carbonate has low toxicity and biodegradability. And the experimental results show that the ester group in dimethyl carbonate endows it with good lipophilicity. Compared with diethyl carbonate, dimethyl carbonate has a greater density. When used together with amidoxime substances, it can better dissolve and extract the organic matter in the wastewater into the organic phase, improving the removal rate of organic matter in coal chemical industry wastewater. Moreover, the lipophilic ester group in dimethyl carbonate and the hydrophilic amino group, hydroxyl group and lipophilic amide group in amidoxime substances can cooperate synergistically to form a multi-functional remover. When the two are used together, they can play a synergistic cooperation role, improving the removal rate of various organic matters in coal chemical industry wastewater.

[0020] (2) The present invention studies by investigating the carbon chain length of the diamide group in the molecular chain of amidoxime substances. The experimental results show that as the carbon chain length of the diamide group increases, the removal effect of organic matter shows a trend of first increasing and then decreasing. In addition, compared with the ketoglutaric acid diamide diacetamide oxime prepared from iminodiacetonitrile, the organic matter remover compounded with ketoglutaric acid diamide dipropionamide oxime prepared from β,β'-iminodipropionitrile has a higher removal rate of organic matter.

[0021] (3) Since the organic matter remover in the multi-stage treatment method of coal chemical industry wastewater of the present invention contains various active groups (lipophilic ester group, hydrophilic amino group, hydroxyl group and lipophilic amide group), it can effectively avoid the problem that the organic matter remover is sensitive to the pH of the wastewater when using a single active group. The experimental results prove that the organic matter remover in the multi-stage treatment method of coal chemical industry wastewater of the present invention has good removal effects on various organic matters (including lipophilic organic matters such as volatile phenol, thiophene, pyridine, quinoline, furan, naphthalene, anthracene, phenanthrene and hydrophilic organic matters such as carbazole, indole and pyrrole) in coal chemical industry wastewater with different pH values. The multi-stage treatment method of coal chemical industry wastewater of the present invention is not sensitive to the pH of the wastewater, has a wide applicability, can treat various wastewater with different pH values, omits the pretreatment step, and reduces the treatment cost. Description of the Drawings

[0022] Figure 1 It is the 1H NMR spectrum of ketoglutaric acid diamide dipropionamide oxime prepared in Example 1 of the present invention. Detailed Embodiments

[0023] The following examples are intended to further illustrate the content of the present invention rather than limit the protection scope of the present invention.

[0024] Example 1

[0025] The multi-stage treatment method for coal chemical industry wastewater in this embodiment includes the following steps: feeding the coal chemical industry wastewater into a sedimentation tank for sedimentation to remove solid particles and obtain sedimented wastewater; then stirring and mixing the sedimented wastewater and the organic matter removing agent in a mass ratio of 3:1, standing for layering, and removing the organic phase to obtain oil-removed wastewater; finally, using a weak acid cation exchange resin to remove metal cations in the oil-removed wastewater to obtain purified water.

[0026] Among them, the organic matter removing agent is composed of dimethyl carbonate and ketoglutaric acid diamide dipropionamide oxime, and the mass ratio of dimethyl carbonate to ketoglutaric acid diamide dipropionamide oxime is 6:1; the preparation method of ketoglutaric acid diamide dipropionamide oxime is as follows:

[0027] (1) Add α-ketoglutaric acid and dichloromethane into a reaction kettle, stir until α-ketoglutaric acid is fully dissolved to obtain a 12% mass fraction α-ketoglutaric acid solution; then add thionyl chloride into the reaction kettle, heat to 65 °C, stir and reflux for 8 h, and remove dichloromethane and excess thionyl chloride by vacuum distillation to obtain α-ketoglutaric acid chloride. Among them, the molar ratio of α-ketoglutaric acid to thionyl chloride is 1:4, and the structural formula of α-ketoglutaric acid chloride is as follows:

[0028]

[0029] (2) Add β,β'-iminodipropionitrile and dichloromethane into a reaction kettle, stir evenly to obtain a 20% mass fraction β,β'-iminodipropionitrile solution, then adjust the temperature of the β,β'-iminodipropionitrile solution to -5 °C, and under stirring and at -5 °C, slowly drop the dichloromethane solution of 12% mass fraction α-ketoglutaric acid chloride into the β,β'-iminodipropionitrile solution. After the dropping is completed, add triethylamine into the reaction kettle, then adjust the temperature of the materials in the reaction kettle to room temperature, continue stirring and reacting for 5 h, filter, distill the filtrate under reduced pressure to remove dichloromethane to obtain a concentrate, and then subject the concentrate to column chromatography purification (the eluent is composed of petroleum ether and ethyl acetate with a volume ratio of 2:3) to obtain ketoglutaric acid diamide dipropionitrile. Among them, the molar ratio of β,β'-iminodipropionitrile, α-ketoglutaric acid chloride and triethylamine is 1:2:2.1. The structural formula of β,β'-iminodipropionitrile is as follows:

[0030]

[0031] The structural formula of ketoglutaric acid diamide dipropionitrile is as follows:

[0032]

[0033] (3) Stir hydroxylamine hydrochloride and methanol evenly to obtain a hydroxylamine hydrochloride methanol solution with a mass fraction of 15%. Then add potassium hydroxide to the hydroxylamine hydrochloride methanol solution to adjust the pH of the hydroxylamine hydrochloride methanol solution to 7.5. Then add ketoglutaric diamide dicyanopropane and methanol with a mass ratio of 2:1, and then stir and react at 80 °C for 2 h. Then cool to -3 °C, filter, wash the filter cake with cold water at 0 °C, and dry to obtain ketoglutaric diamide dipropionamide oxime; wherein, the molar ratio of ketoglutaric diamide dicyanopropane to hydroxylamine hydrochloride is 1:4.2, and the nuclear magnetic hydrogen spectrum of ketoglutaric diamide dipropionamide oxime is as shown in Figure 1 shown, and the structural formula is as follows:

[0034]

[0035] Example 2

[0036] The multi-stage treatment method of coal chemical industry sewage in this example includes the following steps: Send the coal chemical industry sewage into a sedimentation tank for sedimentation to remove solid particles to obtain sedimented sewage; then stir and mix the sedimented sewage and the organic matter remover in a mass ratio of 3:1 and let it stand for stratification to remove the organic phase to obtain oil-removed sewage; finally, use a weak acid cation exchange resin to remove metal cations in the oil-removed sewage to obtain purified water.

[0037] Among them, the organic matter remover is composed of dimethyl carbonate and ketoglutaric diamide dipropionamide oxime, and the mass ratio of dimethyl carbonate to ketoglutaric diamide dipropionamide oxime is 7:2; the preparation method of ketoglutaric diamide dipropionamide oxime is as follows:

[0038] (1) Add α-ketoglutaric acid and dichloromethane to a reaction kettle, stir until α-ketoglutaric acid is fully dissolved to obtain an α-ketoglutaric acid solution with a mass fraction of 14%; then add thionyl chloride to the reaction kettle, heat to 70 °C, stir and reflux for 9 h, and remove dichloromethane and excess thionyl chloride by vacuum distillation to obtain α-ketoglutaric acid chloride. Among them, the molar ratio of α-ketoglutaric acid to thionyl chloride is 1:4, and the structural formula of α-ketoglutaric acid chloride is as follows:

[0039]

[0040] (2) Add β,β'-iminodipropionitrile and dichloromethane into a reaction kettle, stir evenly to obtain a β,β'-iminodipropionitrile solution with a mass fraction of 25%. Then adjust the temperature of the β,β'-iminodipropionitrile solution to 0 °C. Under stirring and at 0 °C, slowly dropwise add a dichloromethane solution of α-ketoglutaric acid dichloride with a mass fraction of 15% into the β,β'-iminodipropionitrile solution. After the dropping is completed, add triethylamine into the reaction kettle, then adjust the temperature of the materials in the reaction kettle to room temperature, continue stirring and reacting for 6 h, filter, distill the filtrate under reduced pressure to remove dichloromethane to obtain a concentrate, and then purify the concentrate by column chromatography (the eluent consists of petroleum ether and ethyl acetate with a volume ratio of 2:3) to obtain ketoglutaric acid diamide dipropionitrile. Among them, the molar ratio of β,β'-iminodipropionitrile, α-ketoglutaric acid dichloride and triethylamine is 1:2:2.2. The structural formula of β,β'-iminodipropionitrile is as follows:

[0041]

[0042] The structural formula of ketoglutaric acid diamide dipropionitrile is as follows:

[0043]

[0044] (3) Stir evenly hydrochloric acid hydroxylamine and methanol to obtain a hydrochloric acid hydroxylamine methanol solution with a mass fraction of 15%. Then add potassium hydroxide into the hydrochloric acid hydroxylamine methanol solution to adjust the pH of the hydrochloric acid hydroxylamine methanol solution to 8, and then add ketoglutaric acid diamide dipropionitrile and methanol with a mass ratio of 2:1, and then stir and react at 82 °C for 3 h, then cool to 0 °C, filter, wash the filter cake with cold water at 0 °C, and dry to obtain ketoglutaric acid diamide dipropionamide oxime; among them, the molar ratio of ketoglutaric acid diamide dipropionitrile and hydrochloric acid hydroxylamine is 1:4.4.

[0045] Example 3

[0046] The multi-stage treatment method of coal chemical industry sewage in this example includes the following steps: Send the coal chemical industry sewage into a sedimentation tank for sedimentation to remove solid particles to obtain sedimentation sewage; then stir and mix the sedimentation sewage and an organic matter removing agent in a mass ratio of 4:1, stand and separate layers to remove the organic phase to obtain oil-removing sewage; finally, use a weak acid cation exchange resin to remove metal cations in the oil-removing sewage to obtain purified water.

[0047] Among them, the organic matter removing agent consists of dimethyl carbonate and ketoglutaric acid diamide dipropionamide oxime, and the mass ratio of dimethyl carbonate and ketoglutaric acid diamide dipropionamide oxime is 9:3; the preparation method of ketoglutaric acid diamide dipropionamide oxime is as follows:

[0048] (1) Add α-ketoglutaric acid and dichloromethane to a reaction kettle, stir until α-ketoglutaric acid is fully dissolved to obtain an α-ketoglutaric acid solution with a mass fraction of 16%; then add thionyl chloride to the reaction kettle, heat to 75 °C, stir and reflux for 10 h, and remove dichloromethane and excess thionyl chloride by vacuum distillation to obtain α-ketoglutaric acid chloride. Among them, the molar ratio of α-ketoglutaric acid to thionyl chloride is 1:5, and the structural formula of α-ketoglutaric acid chloride is as follows:

[0049]

[0050] (2) Add β,β'-iminodipropionitrile and dichloromethane to a reaction kettle, stir evenly to obtain a β,β'-iminodipropionitrile solution with a mass fraction of 30%, then adjust the temperature of the β,β'-iminodipropionitrile solution to 2 °C, and under stirring and at 2 °C, slowly dropwise add a dichloromethane solution of α-ketoglutaric acid chloride with a mass fraction of 17% to the β,β'-iminodipropionitrile solution. After the dropping is completed, add triethylamine to the reaction kettle, then adjust the temperature of the materials in the reaction kettle to room temperature, continue stirring and reacting for 7 h, filter, distill the filtrate under reduced pressure to remove dichloromethane to obtain a concentrate, and then purify the concentrate by column chromatography (the eluent consists of petroleum ether and ethyl acetate with a volume ratio of 2:3) to obtain ketoglutaric acid diamide dipropionitrile. Among them, the molar ratio of β,β'-iminodipropionitrile, α-ketoglutaric acid chloride and triethylamine is 1:2:2.3. The structural formula of β,β'-iminodipropionitrile is as follows:

[0051]

[0052] The structural formula of ketoglutaric acid diamide dipropionitrile is as follows:

[0053]

[0054] (3) Stir hydrochloric acid hydroxylamine and methanol evenly to obtain a hydrochloric acid hydroxylamine methanol solution with a mass fraction of 15%, then add potassium hydroxide to the hydrochloric acid hydroxylamine methanol solution to adjust the pH of the hydrochloric acid hydroxylamine methanol solution to 8.5, and then add ketoglutaric acid diamide dipropionitrile and methanol with a mass ratio of 2:1, and then stir and react at 85 °C for 3 h, then cool to 2 °C, filter, wash the filter cake with cold water at 0 °C, and dry to obtain ketoglutaric acid diamide dipropionamide oxime; among them, the molar ratio of ketoglutaric acid diamide dipropionitrile to hydrochloric acid hydroxylamine is 1:4.5.

[0055] Example 4

[0056] The difference between the multi-stage treatment method of coal chemical industry wastewater in this embodiment and that in Embodiment 1 lies only in that in the multi-stage treatment method of coal chemical industry wastewater in this embodiment, the organic matter remover consists of dimethyl carbonate and ketosuccinamide dipropionamide oxime, and the mass ratio of dimethyl carbonate to ketosuccinamide dipropionamide oxime is 6:1; the preparation method of ketosuccinamide dipropionamide oxime is as follows:

[0057] (1) Add 2-ketosuccinic acid and dichloromethane into the reaction kettle, stir until 2-ketosuccinic acid is fully dissolved to obtain a 2-ketosuccinic acid solution with a mass fraction of 12%; then add thionyl chloride into the reaction kettle, heat to 65 °C, stir and reflux for 8 h, and distill off dichloromethane and excess thionyl chloride under reduced pressure to obtain ketosuccinyl chloride. Among them, the molar ratio of 2-ketosuccinic acid to thionyl chloride is 1:4, and the structure of ketosuccinyl chloride is as follows:

[0058]

[0059] (2) Add β,β'-iminodipropionitrile and dichloromethane into the reaction kettle, stir evenly to obtain a β,β'-iminodipropionitrile solution with a mass fraction of 20%, then adjust the temperature of the β,β'-iminodipropionitrile solution to -5 °C, and under stirring and at -5 °C, slowly drop the dichloromethane solution of ketosuccinyl chloride with a mass fraction of 12% into the β,β'-iminodipropionitrile solution. After the dropping is completed, add triethylamine into the reaction kettle, then adjust the temperature of the materials in the reaction kettle to room temperature, continue to stir and react for 5 h, filter, distill off dichloromethane from the filtrate under reduced pressure to obtain a concentrate, and then purify the concentrate by column chromatography (the eluent consists of petroleum ether and ethyl acetate with a volume ratio of 2:3) to obtain ketosuccinamide dipropionitrile. Among them, the molar ratio of β,β'-iminodipropionitrile, ketosuccinyl chloride and triethylamine is 1:2:2.1. The structural formula of β,β'-iminodipropionitrile is as follows:

[0060]

[0061] (3) Stir evenly hydrochloric hydroxylamine and methanol to obtain a hydrochloric hydroxylamine methanol solution with a mass fraction of 15%, then add potassium hydroxide into the hydrochloric hydroxylamine methanol solution to adjust the pH of the hydrochloric hydroxylamine methanol solution to 7.5, add ketosuccinamide dipropionitrile and methanol with a mass ratio of 2:1, then stir and react at 80 °C for 2 h, then cool to -3 °C, filter, wash the filter cake with cold water at 0 °C, and dry to obtain ketosuccinamide dipropionamide oxime; among them, the molar ratio of ketosuccinamide dipropionitrile to hydrochloric hydroxylamine is 1:4.2.

[0062] Example 5

[0063] The difference between the multi-stage treatment method of coal chemical industry wastewater in this embodiment and that in Embodiment 1 lies only in that in the multi-stage treatment method of coal chemical industry wastewater in this embodiment, the organic matter remover consists of dimethyl carbonate and ketoheptanediamide dipropanamide oxime, and the mass ratio of dimethyl carbonate to ketoheptanediamide dipropanamide oxime is 6:1; the preparation method of ketoheptanediamide dipropanamide oxime is as follows:

[0064] (1) Add 4-ketoheptanedioic acid and dichloromethane into a reaction kettle, stir until 4-ketoheptanedioic acid is completely dissolved to obtain a 4-ketoheptanedioic acid solution with a mass fraction of 12%; then add thionyl chloride into the reaction kettle, heat to 65 °C, stir and reflux for 8 h, and remove dichloromethane and excess thionyl chloride by vacuum distillation to obtain ketoheptanedioyl chloride. Among them, the molar ratio of 4-ketoheptanedioic acid to thionyl chloride is 1:4, and the structure of ketoheptanedioyl chloride is as follows:

[0065]

[0066] (2) Add β,β'-iminodipropionitrile and dichloromethane into a reaction kettle, stir evenly to obtain a β,β'-iminodipropionitrile solution with a mass fraction of 20%, then adjust the temperature of the β,β'-iminodipropionitrile solution to -5 °C, and under stirring and at -5 °C, slowly drop the dichloromethane solution of ketoheptanedioyl chloride with a mass fraction of 12% into the β,β'-iminodipropionitrile solution. After the dropping is completed, add triethylamine into the reaction kettle, then adjust the temperature of the materials in the reaction kettle to room temperature, continue to stir and react for 5 h, filter, distill the filtrate under reduced pressure to remove dichloromethane to obtain a concentrate, and then purify the concentrate by column chromatography (the eluent consists of petroleum ether and ethyl acetate with a volume ratio of 2:3) to obtain ketoheptanediamide dipropionitrile. Among them, the molar ratio of β,β'-iminodipropionitrile, ketoheptanedioyl chloride and triethylamine is 1:2:2.1. The structural formula of β,β'-iminodipropionitrile is as follows:

[0067]

[0068] (3) Stir hydrochloric acid hydroxylamine and methanol evenly to obtain a hydrochloric acid hydroxylamine methanol solution with a mass fraction of 15%, then add potassium hydroxide into the hydrochloric acid hydroxylamine methanol solution to adjust the pH of the hydrochloric acid hydroxylamine methanol solution to 7.5, then add ketoheptanediamide dipropionitrile and methanol with a mass ratio of 2:1, and then stir and react at 80 °C for 2 h, then cool to -3 °C, filter, wash the filter cake with cold water at 0 °C, and dry to obtain ketoheptanediamide dipropanamide oxime; among them, the molar ratio of ketoheptanediamide dipropionitrile to hydrochloric acid hydroxylamine is 1:4.2.

[0069] Example 6

[0070] The difference between the multi-stage treatment method of coal chemical wastewater in this embodiment and that in Embodiment 1 is only that in the multi-stage treatment method of coal chemical wastewater in this embodiment, the organic matter remover consists of dimethyl carbonate and ketoglutaric acid diamide diacetamide oxime, and the mass ratio of dimethyl carbonate to ketoglutaric acid diamide diacetamide oxime is 6:1; the preparation method of ketoglutaric acid diamide diacetamide oxime is as follows:

[0071] (1) Add α-ketoglutaric acid and dichloromethane into the reaction kettle, stir until α-ketoglutaric acid is fully dissolved to obtain a 12% mass fraction α-ketoglutaric acid solution; then add thionyl chloride into the reaction kettle, heat to 65 °C, stir and reflux for 8 h, and remove dichloromethane and excess thionyl chloride by vacuum distillation to obtain α-ketoglutaric acid chloride. Among them, the molar ratio of α-ketoglutaric acid to thionyl chloride is 1:4, and the structural formula of α-ketoglutaric acid chloride is as follows:

[0072]

[0073] (2) Add iminodiacetonitrile and dichloromethane into the reaction kettle, stir evenly to obtain a 20% mass fraction iminodiacetonitrile solution, then adjust the temperature of the iminodiacetonitrile solution to -5 °C, and slowly drop the dichloromethane solution of 12% mass fraction α-ketoglutaric acid chloride into the iminodiacetonitrile solution under stirring and at -5 °C. After the dropping is completed, add triethylamine into the reaction kettle, then adjust the temperature of the materials in the reaction kettle to room temperature, continue to stir and react for 5 h, filter, distill the filtrate under reduced pressure to remove dichloromethane to obtain a concentrate, and then purify the concentrate by column chromatography (the eluent consists of petroleum ether and ethyl acetate with a volume ratio of 2:3) to obtain ketoglutaric acid diamide diacetonitrile. Among them, the molar ratio of iminodiacetonitrile, α-ketoglutaric acid chloride and triethylamine is 1:2:2.1. The structural formula of iminodiacetonitrile is as follows:

[0074]

[0075] (3) Stir hydrochloric acid hydroxylamine and methanol evenly to obtain a 15% mass fraction hydrochloric acid hydroxylamine methanol solution, then add potassium hydroxide into the hydrochloric acid hydroxylamine methanol solution to adjust the pH of the hydrochloric acid hydroxylamine methanol solution to 7.5, then add ketoglutaric acid diamide diacetonitrile and methanol with a mass ratio of 2:1, and then stir and react at 80 °C for 2 h, then cool to -3 °C, filter, wash the filter cake with cold water at 0 °C, and dry to obtain ketoglutaric acid diamide diacetamide oxime; among them, the molar ratio of ketoglutaric acid diamide diacetonitrile to hydrochloric acid hydroxylamine is 1:4.2.

[0076] Comparative Example 1

[0077] The difference between the multi-stage treatment method of coal chemical industry wastewater in this comparative example and that in Example 1 lies only in that in the multi-stage treatment method of coal chemical industry wastewater in this comparative example, the organic matter remover is composed of dimethyl carbonate and dimethylglyoxime, and the mass ratio of dimethyl carbonate to dimethylglyoxime is 6:1.

[0078] Comparative Example 2

[0079] The difference between the multi-stage treatment method of coal chemical industry wastewater in this comparative example and that in Example 1 lies only in that in the multi-stage treatment method of coal chemical industry wastewater in this comparative example, the organic matter remover is composed of dimethyl carbonate and salicylaldoxime, and the mass ratio of dimethyl carbonate to salicylaldoxime is 6:1.

[0080] Comparative Example 3

[0081] The difference between the multi-stage treatment method of coal chemical industry wastewater in this comparative example and that in Example 1 lies only in that in the multi-stage treatment method of coal chemical industry wastewater in this comparative example, the organic matter remover is composed of diethyl carbonate and ketoglutaric acid diamide dipropionamide oxime, the mass ratio of diethyl carbonate to ketoglutaric acid diamide dipropionamide oxime is 6:1, and the ketoglutaric acid diamide dipropionamide oxime is the same as that in Example 1.

[0082] Comparative Example 4

[0083] The difference between the multi-stage treatment method of coal chemical industry wastewater in this comparative example and that in Example 1 lies only in that in the multi-stage treatment method of coal chemical industry wastewater in this comparative example, the organic matter remover is composed of ethyl acetate and ketoglutaric acid diamide dipropionamide oxime, the mass ratio of ethyl acetate to ketoglutaric acid diamide dipropionamide oxime is 6:1, and the ketoglutaric acid diamide dipropionamide oxime is the same as that in Example 1.

[0084] Comparative Example 5

[0085] The difference between the multi-stage treatment method of coal chemical industry wastewater in this comparative example and that in Example 1 lies only in that in the multi-stage treatment method of coal chemical industry wastewater in this comparative example, the organic matter remover is composed of a main extractant and a synergistic extractant with a volume ratio of 6:4; the main extractant is composed of benzaldoxime and methyl ethyl ketone, and the volume ratio of benzaldoxime to methyl ethyl ketone is 1:3; the synergistic extractant is composed of sec-octanol and anisole, and the volume ratio of sec-octanol to anisole is 6:4.

[0086] Comparative Example 6

[0087] The difference between the multi-stage treatment method of coal chemical industry wastewater in this comparative example and that in Example 1 lies only in that in the multi-stage treatment method of coal chemical industry wastewater in this comparative example, the organic matter remover is dimethyl carbonate.

[0088] Experimental Example

[0089] In order to investigate the removal effect of the organic matter remover in the multi-stage treatment method of coal chemical industry wastewater in each example and comparative example on the organic matter in coal chemical industry wastewater, taking a certain gas washing water as the treatment object, the gas washing water was first sedimented to remove solid particles to obtain sedimented wastewater; then the sedimented wastewater and the organic matter remover were stirred and mixed at a mass ratio of 3:1 and left to stand for stratification, and the organic phase was removed to obtain deoiled wastewater; during the experiment, the contents of volatile phenol, thiophene, pyridine, quinoline, carbazole, indole, furan, pyrrole, naphthalene, anthracene, and phenanthrene in the sedimented wastewater and the deoiled wastewater treated with different organic matter removers were respectively tested, and the removal rates of volatile phenol, thiophene, pyridine, quinoline, carbazole, indole, furan, pyrrole, naphthalene, anthracene, and phenanthrene were calculated. The results are shown in Table 1.

[0090] Among them, the contents of volatile phenol, thiophene, pyridine, quinoline, carbazole, indole, furan, pyrrole, naphthalene, anthracene, and phenanthrene in the sedimented wastewater were 8694 mg / L, 231 mg / L, 418 mg / L, 369 mg / L, 432 mg / L, 264 mg / L, 195 mg / L, 372 mg / L, 85 mg / L, 91 mg / L, and 103 mg / L respectively; the pH of the sedimented wastewater was 10.2; finally, in order to investigate the removal effect of the organic matter remover on the organic matter in coal chemical industry wastewater under different conditions, hydrochloric acid was used to adjust the pH of the sedimented wastewater to 7.2 and 5.2, and then the sedimented wastewater with pH of 7.2 and 5.2 and the organic matter remover were stirred and mixed at a mass ratio of 3:1 and left to stand for stratification, and the organic phase was removed to obtain deoiled wastewater, and then tested and analyzed to calculate the removal rates of volatile phenol, thiophene, pyridine, quinoline, carbazole, indole, furan, pyrrole, naphthalene, anthracene, and phenanthrene corresponding to different organic matter removers under different conditions. The results are shown in Tables 2-3.

[0091] During the experiment, the content of volatile phenol was tested according to the regulations in Standard GB / T 7490-1987 "Determination of Volatile Phenols in Water - Spectrophotometric Method with 4-Aminoantipyrine after Distillation"; the contents of thiophene, pyridine, quinoline, carbazole, indole, furan, pyrrole, naphthalene, anthracene, and phenanthrene were determined by liquid chromatography. Each sample was measured 3 times, and the average value of the 3 results was used as the final experimental result. Removal rate = (Content of organic matter in sedimented wastewater - Content of organic matter in deoiled wastewater) / Content of organic matter in sedimented wastewater × 100%.

[0092] Table 1 Removal Rates (%) of Organic Matter in Sedimented Wastewater with pH of 10.2 by Organic Matter Removers in the Multi-stage Treatment Methods of Coal Chemical Industry Wastewater in Each Example and Comparative Example

[0093]

[0094] Removal rate (%) of organic matter in the settling sewage with pH 7.2 by the organic matter remover in the multi-stage treatment method of coal chemical sewage in each example and comparative example

[0095]

[0096]

[0097] Table 3 Removal rate (%) of organic matter in the settling sewage with pH 5.2 by the organic matter remover in the multi-stage treatment method of coal chemical sewage in each example and comparative example

[0098]

[0099]

[0100] As can be seen from Tables 1-3, the organic matter remover in the multi-stage treatment method of coal chemical sewage in Examples 1-3 and Examples 4-6 of the present invention has good removal effects on various organic matters (including lipophilic organic matters such as volatile phenol, thiophene, pyridine, quinoline, furan, naphthalene, anthracene, phenanthrene, and hydrophilic organic matters such as carbazole, indole, and pyrrole) in coal chemical sewage with pH 5.2, 7.2, and 10.2. However, the organic matter remover in the multi-stage treatment method of coal chemical sewage in Comparative Examples 1-6 only has a good removal rate for lipophilic substances (such as volatile phenol, thiophene, pyridine, quinoline, furan, naphthalene, anthracene, phenanthrene) in the wastewater at a lower pH, but still has a poor removal rate for hydrophilic organic matters such as carbazole, indole, and pyrrole. The above results show that the organic matter remover in the multi-stage treatment method of coal chemical sewage of the present invention is not sensitive to the pH of the wastewater, has a wide applicability, can treat wastewater with various different pH values, omits the pretreatment step, and reduces the treatment cost.

[0101] As can be seen from the test results of Example 1 and Examples 4-5, the carbon chain length of the diamide group in the molecular chain of amidoxime substances (ketoglutaric acid diamide dipropylamidoxime, ketosuccinic acid diamide dipropylamidoxime, and ketoheptanediamide dipropylamidoxime) in the organic matter remover will affect the removal effect of organic matter. As the carbon chain length of the diamide group increases, the removal effect of organic matter shows a trend of first increasing and then decreasing, which may be related to the hydrophilic-lipophilic property of amidoxime substances.

[0102] As can be seen from Example 1 and Example 6, compared with the ketoglutaric acid diamide diethylamidoxime prepared with iminodiacetonitrile, the organic matter remover compounded with ketoglutaric acid diamide dipropylamidoxime prepared with β,β'-iminodipropionitrile has a higher removal rate of organic matter.

[0103] It can be seen from Example 1, Comparative Examples 1-2, Comparative Examples 3-4 and Comparative Example 6 that when the amidoxime substances in the organic matter remover are replaced with dimethylglyoxime or salicylaldoxime, or when the dimethyl carbonate in the organic matter remover is replaced with diethyl carbonate or ethyl acetate, or only dimethyl carbonate is used, the removal effect of the organic matter remover on coal chemical wastewater with different pH values becomes worse. This shows that dimethyl carbonate and ketoglutaric acid diamide dipropionamide oxime, ketosuccinic acid diamide dipropionamide oxime, and ketoheptanediamide dipropionamide oxime have a synergistic cooperation effect. When used together, they can play a synergistic cooperation effect and improve the removal rate of organic matter.

Claims

1. A multi-stage treatment method for coal chemical industry wastewater, characterized in that, The method includes the following steps: Subject the coal chemical industry wastewater to sedimentation treatment to obtain sedimentation wastewater; then mix the sedimentation wastewater and the organic matter removing agent at a mass ratio of 3-4:1, let it stand for layering, remove the organic phase to obtain oil-removed wastewater; finally, remove the metal cations in the oil-removed wastewater to obtain purified water; the organic matter removing agent is composed of dimethyl carbonate and amidoxime substances at a mass ratio of 6-9:1-3, and the structure of the amidoxime substances is as follows: Wherein, R1 is methylene or ethylene, and R2 is a unit shown in Formula 1, Formula 2 or Formula 3; 2. The multi-stage treatment method for coal chemical industry wastewater according to claim 1, characterized in that, The preparation method of the amidoxime substances is as follows: React keto-diacid with thionyl chloride to obtain keto-diacyl chloride; react keto-diacyl chloride with iminodiacetonitrile to obtain a keto-diamide dinitrile compound; finally, react the keto-diamide dinitrile compound with hydroxylamine hydrochloride to obtain amidoxime substances; the keto-diacid is α-ketoglutaric acid, 2-ketosuccinic acid or 4-ketoheptanoic acid; the iminodiacetonitrile is iminodiacetonitrile or β,β'-iminodipropionitrile.

3. The multi-stage treatment method for coal chemical industry wastewater according to claim 2, wherein, The reaction temperature of the keto-diacid and thionyl chloride is 65-75°C, and the time is 8-10 h.

4. The multi-stage treatment method for coal chemical industry sewage according to claim 2, characterized in that, The molar ratio of the keto-diacid and thionyl chloride is 1:4-5.

5. The multi-stage treatment method for coal chemical industry wastewater according to claim 2, wherein, The molar ratio of the keto-diacyl chloride and iminodiacetonitrile is 1:

2.

6. The multi-stage treatment method for coal chemical wastewater according to claim 2, wherein, The reaction temperature of the keto-diacyl chloride and iminodiacetonitrile is -5-2°C, and the time is 5-7 h.

7. The multi-stage treatment method for coal chemical industry wastewater according to claim 2, characterized in that, The reaction method of the keto-diamide dinitrile compound and hydroxylamine hydrochloride is as follows: Adjust the pH of the hydroxylamine hydrochloride methanol solution to 7.5-8.5, then add the keto-diamide dinitrile compound, and then carry out a mixing reaction at 80-85°C for 2-3 h, and obtain the amidoxime substances after impurity removal.

8. The multi-stage treatment method for coal chemical industry wastewater according to claim 7, characterized in that The molar ratio of the keto-diamide dinitrile compound and hydroxylamine hydrochloride is 1:4.2-4.

5.

9. The multi-stage treatment method for coal chemical industry wastewater according to any one of claims 1-8, characterized in that, The coal chemical industry wastewater contains volatile phenols, thiophene, pyridine, quinoline, carbazole, indole, furan, pyrrole, naphthalene, anthracene, phenanthrene.

10. The multi-stage treatment method for coal chemical industry sewage according to any one of claims 1-8, characterized in that, The pH of the sedimentation wastewater is 5-10.5.

Images