A dephenolized extractant and a method for extracting and recovering phenol from phenol-containing wastewater

Abstract

The present application belongs to the technical field of semi-coke wastewater pretreatment, and particularly relates to a dephenol extractant and a method for extracting and recovering phenol from wastewater containing phenol. The dephenol extractant provided by the present application comprises: N, N-di(1-methyl-heptyl)acetamide 40-60%, di(2,4,4-trimethylpentyl) hypophosphorous acid 30-55%, and an organic dispersing agent 1-10%. The dephenol extractant is used for multi-stage countercurrent extraction of wastewater containing phenol, and organic phase containing phenol and raffinate water phase are obtained. The dephenol extractant provided by the present application has high extraction efficiency, low water solubility, high stability, reliable recovery efficiency, and long service life. The dephenol extractant provided by the present application can be used to extract and recover phenol from semi-coke wastewater at low cost, high recovery efficiency, and high convenience, and can significantly reduce the concentration of phenols in wastewater, fully meeting the water inlet requirements of the subsequent biochemical treatment system for further treatment of semi-coke wastewater.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of low-temperature coal (Lan-tan) wastewater pretreatment, and particularly relates to a dephenol extractant and a method for extracting and recovering phenol from phenol-containing wastewater. BACKGROUND

[0002] Lan-tan, as a new type of carbon material, can be widely used in chemical industry, smelting and other industries instead of coke. However, a large amount of Lan-tan wastewater will be discharged in the production process of Lan-tan. This kind of wastewater contains a large amount of pollutants such as benzene series, phenols, polycyclic aromatic hydrocarbons, nitrogen-oxygen heterocyclic compounds and the like, and is a typical high-pollution and high-toxicity industrial wastewater. After pretreatment such as dust removal and oil removal, the concentration of phenolic substances in the wastewater is still as high as several thousand to several ten thousand milligrams per liter. This kind of phenol-containing wastewater is listed as one of the harmful wastewaters that need to be solved in water pollution control in China. The phenolic substances in the wastewater pose a serious threat to human health and the ecological environment due to their high concentration, high toxicity and difficult degradation, and these substances also have the value of recycling. Therefore, the Lan-tan wastewater needs to be pretreated by efficient dephenolization before entering the biochemical system, and the treatment effect will directly affect the stability of the subsequent system and the final treatment effect.

[0003] At present, the common dephenolization method for high-concentration phenol-containing Lan-tan wastewater is to recover phenol by solvent extraction. The key of solvent extraction method is the selection of extractant and the optimization of extraction process, and the quality of extractant determines the energy consumption, material consumption and efficiency of the extraction process. At present, the dephenolization extractants that are more mature in commercial application are methyl isobutyl ketone (MIBK) and diisopropyl ether (DIPE). Chinese patents CN201611191625.6 and CN202111021158.3 respectively propose a combined extractant. The former uses n-propyl propionate and anisole as the extractant, and the extraction rate of phenols is improved, but n-propyl propionate has problems such as hydrolysis under hot acid conditions, which not only causes the problems of reduced extraction rate and service life, but also leads to increased COD of wastewater, increasing the pressure of subsequent biochemical degradation. The latter introduces basic amine and neutral phosphorus-containing extractant components, and the extraction efficiency can be increased to 73.4%, but the concentration of phenols in the effluent still remains at several hundred milligrams per liter. Although increasing the amount of extractant can effectively improve the efficiency, it will also cause the problem of increased cost. Therefore, an economic and efficient phenol extractant without secondary pollution needs to be developed. SUMMARY

[0004] The present application provides a dephenol extractant and a method for extracting and recovering phenol from phenol-containing wastewater. The present application provides a low-cost, high-recovery-efficiency and easy-to-use extractant for extracting and recovering phenol from Lan-tan wastewater, which can significantly reduce the concentration of phenols in the wastewater after extraction and separation of the dephenol extractant for high-phenol-content Lan-tan wastewater, and fully meet the influent requirements of the subsequent biochemical treatment system for further treatment of Lan-tan wastewater.

[0005] To achieve the above object, the present application provides the following technical solutions.

[0006] The present application provides a dephenolization extractant, comprising the following components in volume percentage: N,N-di(1-methyl-heptyl)acetamide 40-60%, di(2,4,4-trimethylpentyl) hypophosphorous acid 30-55%, and an organic dispersant 1-10%.

[0007] Preferably, the organic dispersant comprises kerosene and / or cumene.

[0008] The present application provides a method for extracting and recovering phenol from phenol-containing wastewater, comprising the following steps:

[0009] The dephenolization extractant described in the above technical solution is used for multi-stage countercurrent extraction of the phenol-containing wastewater, to obtain a phenol-containing organic phase and a raffinate water phase.

[0010] Preferably, the number of extraction stages of the multi-stage countercurrent extraction is 2-8; the temperature of each stage of extraction is 30-55℃, the time of each stage of extraction is 10-30 min, and the operating pressure of each stage of extraction is 105-130 kPa.

[0011] Preferably, the number of extraction stages of the multi-stage countercurrent extraction is 3; the method for 3-stage countercurrent extraction comprises the following steps:

[0012] The first-stage countercurrent extraction of the phenol-containing wastewater is performed using a first extractant, to obtain a first-stage extraction phase and a first-stage raffinate phase;

[0013] The second-stage countercurrent extraction of the first-stage raffinate phase is performed using a second extractant, to obtain a second-stage extraction phase and a second-stage raffinate phase; the first-stage extraction phase and the second-stage extraction phase are the phenol-containing organic phase;

[0014] The third-stage countercurrent extraction of the second-stage raffinate phase is performed using a third extractant, to obtain a third-stage extraction phase and a third-stage raffinate phase; after obtaining the third-stage extraction phase, the third-stage extraction phase is used to replace part of the second extractant; the third-stage raffinate phase is the raffinate water phase.

[0015] Preferably, after obtaining the phenol-containing organic phase, the following step is further included: the back extraction of the phenol-containing organic phase is performed using a back extraction agent, to obtain a phenate aqueous solution and a recovered extractant; the back extraction agent is an inorganic alkali aqueous solution, and the volume ratio of the back extraction agent to the phenol-containing organic phase is 1:1.8-1:2.3;

[0016] After obtaining the recovered extractant, the following step is further included: the recovered extractant is reused in at least one of the first-stage countercurrent extraction, the second-stage countercurrent extraction, and the third-stage countercurrent extraction.

[0017] Preferably, when the recovered extractant is reused to the first stage countercurrent extraction, the recovered extractant replaces part of the first extractant, and the volume ratio of the remaining first extractant to the recovered extractant used in the first stage countercurrent extraction is 1-2:8-9.

[0018] Preferably, when the recovered extractant is reused to the first stage countercurrent extraction, the recovered extractant replaces part of the first extractant, and the volume ratio of the remaining first extractant to the recovered extractant used in the first stage countercurrent extraction is 1-2:8-9.

[0019] Preferably, when the recovered extractant is reused to the first stage countercurrent extraction, the recovered extractant replaces part of the first extractant, and the volume ratio of the remaining first extractant to the recovered extractant used in the first stage countercurrent extraction is 1-2:8-9.

[0020] Preferably, when the recovered extractant is reused to the second stage countercurrent extraction, the recovered extractant replaces the remaining second extractant, and the volume ratio of the recovered extractant to the third extractant phase used in the second stage countercurrent extraction is 1-2:2-4.

[0021] Preferably, when the recovered extractant is reused to the second stage countercurrent extraction, the recovered extractant replaces the remaining second extractant, and the volume ratio of the recovered extractant to the third extractant phase used in the second stage countercurrent extraction is 1-2:2-4.

[0022] Preferably, when the recovered extractant is reused to the third stage countercurrent extraction, the recovered extractant replaces part of the third extractant, and the volume ratio of the remaining third extractant to the recovered extractant used in the third stage countercurrent extraction is 2-3:1-3.

[0023] Preferably, when the recovered extractant is reused to the third stage countercurrent extraction, the recovered extractant replaces part of the third extractant, and the volume ratio of the remaining third extractant to the recovered extractant used in the third stage countercurrent extraction is 2-3:1-3.

[0024] Preferably, after obtaining the aqueous phenolate solution, the method further comprises: introducing CO2 into the aqueous phenolate solution to obtain a crude phenol product.

[0025] After obtaining the raffinate aqueous phase, the method further comprises: adsorbing the raffinate aqueous phase with an adsorption material to obtain low-phenol wastewater, the adsorption material comprising one or more of gasified slag, coal ash slag, and fly ash; and the total phenol content in the low-phenol wastewater after adsorption is ≤10 mg / L.

[0026] The present application provides a phenol removal extractant, comprising the following components in volume percentage: N, N-di (1-methyl-heptyl) acetamide 40-60%, di (2, 4, 4-trimethylpentyl) hypophosphorous acid 30-55%, and organic dispersant 1-10%. In the phenol removal extractant provided by the present application, the lone pair electrons in the two components of N, N-di (1-methyl-heptyl) acetamide and di (2, 4, 4-trimethylpentyl) hypophosphorous acid form an electrically neutral ligand with the phenoxy negative ions, acid ions (i.e. some acid ions remaining after deacidification treatment) and hydrogen ions in the phenol-containing wastewater, and a complex is formed by coordination, so that the phenols are extracted into the organic phase. The phenol removal extractant provided by the present application has good extraction effect in an environment with a salt concentration (the salt concentration refers to the concentration of dissolved organic solids (TDS), which is a water quality index value) of 0-2000 mg / L and a pH of 5-9. The phenol removal extractant provided by the present application is used for treating phenol-containing semi-coke wastewater, and compared with other commonly used phenol extractants, in addition to high extraction efficiency, it also has low water solubility (12.6±0.3 mg / L), high stability, reliable recovery efficiency and long service life. Therefore, the phenol removal extractant provided by the present application can be used to extract and recover phenols from semi-coke wastewater at low cost, high recovery efficiency and convenience, and can significantly reduce the concentration of phenols in wastewater, fully meeting the water inlet requirements of the subsequent biochemical treatment system for further treatment of semi-coke wastewater.

[0027] The present application provides a method for extracting and recovering phenols from phenol-containing wastewater, comprising the following steps: using the phenol removal extractant described in the above technical solution for multi-stage countercurrent extraction of the phenol-containing wastewater to obtain phenol-containing organic phase and raffinate water phase. The phenol removal extractant described in the above technical solution can be used to extract and recover phenols from semi-coke wastewater at low cost, high recovery efficiency and convenience, and can significantly reduce the concentration of phenols in wastewater, fully meeting the water inlet requirements of the subsequent biochemical treatment system for further treatment of semi-coke wastewater.

[0028] Further, in the present application, the extraction number of the multi-stage countercurrent extraction is 3; the method of 3-stage countercurrent extraction comprises the following steps: first-stage countercurrent extraction of the phenol-containing wastewater by using a first extractant to obtain a first-stage extraction phase and a first-stage raffinate phase; second-stage countercurrent extraction of the first-stage raffinate phase by using a second extractant to obtain a second-stage extraction phase and a second-stage raffinate phase; the first-stage extraction phase and the second-stage extraction phase are the phenol-containing organic phase; third-stage countercurrent extraction of the second-stage raffinate phase by using a third extractant to obtain a third-stage extraction phase and a third-stage raffinate phase; after obtaining the third-stage extraction phase, further comprising replacing part of the second extractant with the third-stage extraction phase; the third-stage raffinate phase is the raffinate water phase. The present application adopts three-stage countercurrent extraction, and the extraction phase of the third-stage extraction unit is 100% refluxed to the second-stage extraction to meet the purposes of high-efficiency phenol removal and reagent saving. The three extraction units in the present application are connected in series, each being countercurrent extraction, and the extraction phase is completely refluxed in between, which can achieve high-efficiency extraction separation effect to the maximum extent while saving the amount of reagent used, and achieve economic progress. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 A typical process flow diagram for recovering phenol from semicoke wastewater by using a phenol removal extractant in the embodiments of the present application is shown in the figure.

[0030] Figure 1 In the figure: I - multi-stage countercurrent extraction unit, II - adsorption unit, III - extractant recovery (stripping) unit, IV - phenate collection unit, 11 - first-stage countercurrent extraction column, 12 - second-stage countercurrent extraction column, 13 - third-stage countercurrent extraction column, 21 - spraying device, 22 - adsorption material, 31 - stripping tank, 32 - extractant tank, 41 - phenate aqueous solution tank. DETAILED DESCRIPTION

[0031] The present application provides a phenol removal extractant comprising the following components in volume percentage: N,N-di(1-methyl-heptyl)acetamide 40-60%, di(2,4,4-trimethylpentyl)hypophosphorous acid 30-55%, and organic dispersant 1-10%.

[0032] In the present application, all the raw materials / components are commercially available products well known to those skilled in the art unless otherwise specified.

[0033] The phenol removal extractant provided by the present application comprises N,N-di(1-methyl-heptyl)acetamide (DMHAA) 40-60% in volume percentage, preferably 40-55%, more preferably 40-50%, and specifically preferably 40%, 50% or 43%. In the present application, the molecular formula of the DMHAA is C 18 H 37NO, molecular weight 283.5, boiling point 324.4±10.0℃, density 0.857g / cm 3 , appearance is colorless oily liquid, water solubility 60mg / L, essentially non-toxic, good stability to acid, base, light and heat. Bis (2, 4, 4-trimethyl pentyl) hypophosphorous acid molecular formula is C 16 H 35 O2P, molecular weight 290.42, density 0.916g / cm 3 , water solubility 12.6±0.3mg / L, weak acid, non-toxic, good stability.

[0034] The dephenolizing extractant provided by the present application includes 30-55% of bis (2, 4, 4-trimethyl pentyl) hypophosphorous acid, preferably 35-53%, and specifically preferably 50%, 52% or 40% in terms of volume percentage.

[0035] The dephenolizing extractant provided by the present application includes 1-10% of organic dispersant, preferably 5-10%, and specifically preferably 5% or 10% in terms of volume percentage. In the present application, the organic dispersant preferably includes kerosene and / or cumene, and specifically preferably kerosene.

[0036] As one or more embodiments of the present application, the volume ratio of DMHAA, bis (2, 4, 4-trimethyl pentyl) hypophosphorous acid and organic dispersant in the dephenolizing extractant is preferably 4:5:1.

[0037] The present application provides a preparation method of the dephenolizing extractant described in the above technical solution, including the following steps:

[0038] The DMHAA and bis (2, 4, 4-trimethyl pentyl) hypophosphorous acid are mixed uniformly and then mixed with the organic dispersant.

[0039] The dephenolizing extractant provided by the present application uses DMHAA and bis (2, 4, 4-trimethyl pentyl) hypophosphorous acid as extractant, and cooperates with a certain range of volume content of organic dispersant, which can realize low-cost and high-recovery-efficiency recovery of phenol from semi-coke wastewater, so that the concentration of phenol in the wastewater is reduced to below 10mg / L, fully meeting the water inlet requirements of the subsequent biochemical treatment system for further processing of semi-coke wastewater.

[0040] The present application provides a method for extracting and recovering phenol from wastewater containing phenol, including the following steps:

[0041] The dephenolizing extractant described in the above technical solution is used for multi-stage countercurrent extraction of wastewater containing phenol, to obtain phenol-containing organic phase and raffinate water phase.

[0042] In the present application, the phenol-containing wastewater is preferably semi-coke wastewater, and particularly high-phenol semi-coke wastewater after deoiling and deacidification. The total phenol content of the semi-coke wastewater is preferably 5000-50000 mg / L, more preferably 9000-40000 mg / L, further preferably 9500-35000 mg / L, and particularly preferably 10500 mg / L, 9800 mg / L, 13000 mg / L, 11060 mg / L or 22100 mg / L.

[0043] In the present application, the number of extraction stages of the multi-stage countercurrent extraction is preferably 2-8, more preferably 3-6, and particularly preferably 3. The temperature of each stage of extraction is preferably 30-55°C, more preferably 40-50°C. The time of each stage of extraction is preferably 10-30 min, more preferably 20-30 min. The operating pressure of each stage of extraction is preferably 105-130 kPa.

[0044] In the present application, the number of extraction stages of the multi-stage countercurrent extraction is preferably 3. The method of 3-stage countercurrent extraction preferably comprises the following steps:

[0045] The first-stage countercurrent extraction of the phenol-containing wastewater is performed using a first extractant to obtain a first-stage extraction phase and a first-stage raffinate phase.

[0046] The second-stage countercurrent extraction of the first-stage raffinate phase is performed using a second extractant to obtain a second-stage extraction phase and a second-stage raffinate phase. The first-stage extraction phase and the second-stage extraction phase are the phenol-containing organic phase.

[0047] The third-stage countercurrent extraction of the second-stage raffinate phase is performed using a third extractant to obtain a third-stage extraction phase and a third-stage raffinate phase. After obtaining the third-stage extraction phase, the method further comprises replacing part of the second extractant with the third-stage extraction phase. The third-stage raffinate phase is the raffinate water phase.

[0048] The first-stage countercurrent extraction of the phenol-containing wastewater is performed using a first extractant to obtain a first-stage extraction phase and a first-stage raffinate phase. In the present application, after obtaining the recovered extractant, the present application preferably further comprises recycling the recovered extractant to the first-stage countercurrent extraction. When the recovered extractant is recycled to the first-stage countercurrent extraction, the recovered extractant replaces part of the first extractant, and the volume ratio of the remaining first extractant to the recovered extractant used in the first-stage countercurrent extraction is 1-2:8-9, more preferably 1:9 or 2:8. The volume ratio of the first extractant to the phenol-containing wastewater is preferably 1-1.5:3-5, and more preferably 1:4.

[0049] After the first stage raffinate phase is obtained, the second stage countercurrent extraction is performed on the first stage raffinate phase by using a second extractant to obtain a second stage extraction phase and a second stage raffinate phase; the first stage extraction phase and the second stage extraction phase are the phenolic organic phase. In the present application, after the recycled extractant is obtained, the present application preferably further comprises: recycling the recycled extractant to the second stage countercurrent extraction. The recycled extractant replaces the remaining second extractant. The volume ratio of the recycled extractant used in the second stage countercurrent extraction and the third stage extraction phase is 1-2:2-4, more preferably 1:1, 1:3. The volume ratio of the second extractant and the first extractant is 1:1.

[0050] After the second stage raffinate phase is obtained, the third stage countercurrent extraction is performed on the second stage raffinate phase by using a third extractant to obtain a third stage extraction phase and a third stage raffinate phase; after the third stage extraction phase is obtained, it further comprises replacing part of the second extractant with the third stage extraction phase; the third stage raffinate phase is the raffinate aqueous phase. In the present application, after the recycled extractant is obtained, the present application preferably further comprises: recycling the recycled extractant to the third stage countercurrent extraction. When the recycled extractant is recycled to the third stage countercurrent extraction, the recycled extractant replaces part of the third extractant, and the volume ratio of the remaining third extractant and the recycled extractant used in the third stage countercurrent extraction is 2-3:1-3, more preferably 3:2. The volume ratio of the third extractant and the first extractant is preferably 1:1-3, more preferably 1:2.

[0051] In specific embodiments of the present application, the volume ratio of the remaining third extractant and the first extractant is preferably 1-3:5-10, and more preferably 3:10, 1:5 or 1:10. The volume ratio of the recycled extractant used in the third stage countercurrent extraction and the first extractant is preferably 1-3:5-10, and more preferably 1:5, 3:10 or 2:5.

[0052] In the present application, after the multi-stage countercurrent extraction is performed, the removal rate of phenolic pollutants in the phenolic wastewater is ≥95%, i.e. in the present application, the total phenol content of the semi-coke wastewater is 5000-50000 mg / L, and after three-stage extraction, the total phenol content in the raffinate phase is between 100-250 mg / L.

[0053] In the present application, after obtaining the phenol-containing organic phase, the present application preferably further comprises: using a stripping agent to strip the phenol-containing organic phase to obtain a phenolate aqueous solution and recover the extractant. In the present application, the stripping agent is preferably an aqueous inorganic base, more preferably at least one of an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous sodium carbonate solution, an aqueous potassium carbonate solution, an aqueous sodium bicarbonate solution, an aqueous potassium bicarbonate solution, ammonia water, and an aqueous magnesium hydroxide solution, and most preferably an aqueous sodium hydroxide solution. The mass percentage of inorganic base in the stripping agent is preferably 5-15%, and more preferably 10%. The volume ratio of the stripping agent to the phenol-containing organic phase is preferably 1:1.8-1:2.3, and more preferably 1:2. In the present application, the extract phases obtained by the first-stage extraction unit and the second-stage extraction unit enter the extractant recovery tank, react with the stripping agent, generate an aqueous sodium phenolate solution, enter the phenol collection unit, and the recovery rate of the extractant is ≥90%.

[0054] In the present application, in the multi-stage countercurrent extraction process, the present application preferably adopts a three-stage continuous countercurrent extraction process, and at the same time, the recovered extractant is reused in at least one of the first-stage countercurrent extraction, the second-stage countercurrent extraction, and the third-stage countercurrent extraction, and preferably is reused in the first-stage countercurrent extraction, the second-stage countercurrent extraction, and the third-stage countercurrent extraction. Among them, 100% of the extract phase of the third-stage extraction unit is refluxed to the second-stage extraction, and the second extractant is the recovered extractant used by the third-stage extraction phase and the second-stage countercurrent extraction. No new extractant is added in the second-stage extraction unit to meet the purposes of efficient phenol removal and reagent saving. The three extraction units (three-stage extraction) are connected in series, and each stage is countercurrent extraction. The extractants of the first-stage extraction unit, the second-stage extraction unit, and the third-stage extraction unit are all part of the recovered extractant recovered by the stripping unit. And the extract phase of the third-stage extraction unit is refluxed to the second-stage extraction unit as the extractant at the same time, and the reflux ratio is 100%.

[0055] In the multi-stage countercurrent extraction process, the extractants of the three extraction steps are preferably introduced by a dosing pump.

[0056] In the present application, after obtaining the phenolate aqueous solution, the present application preferably further comprises: introducing CO2 into the phenolate aqueous solution to obtain a crude phenol product. In the present application, the generated crude phenol product is recycled and reused, and excess CO2 overflows from the phenolate aqueous solution tank.

[0057] In the present application, after the raffinate aqueous phase is obtained, the present application preferably further comprises: adsorbing the raffinate aqueous phase by using an adsorption material to obtain low-phenol wastewater. In the present application, the adsorption material preferably comprises one or more of gasification slag, coal ash slag and fly ash, more preferably at least two of gasification slag, coal ash slag and fly ash, and particularly preferably gasification slag and fly ash, or fly ash and coal ash slag, or gasification slag and coal ash slag. When the adsorption material preferably comprises two of the above-mentioned substances, the mass ratio of any two of the above-mentioned substances is preferably (1-2):1, and particularly preferably 1:1 or 2:1.

[0058] In the present application, the specific surface area of the gasification slag used in the adsorption is preferably 120-140 m 2 / g, the pore volume is preferably 0.228 m 3 / g, the average pore size is preferably 45.5 nm, and the static water absorption rate is preferably ≥22%, and the bulk density is preferably ≥650 kg / m 3 In the present application, the thickness of the adsorption filling layer obtained by the adsorption material is preferably 1-3 m, and particularly preferably 1.5 m or 1.6 m; the bulk density of the adsorption filling layer is preferably 600-700 kg / m 3 , and particularly preferably 700 kg / m 3 or 650 kg / m 3 .

[0059] In the present application, the gasification slag is a pretreated gasification slag, and the pretreatment is particularly preferably flotation. The present application does not have special requirements for the specific implementation of the pretreatment. In the present application, the total phenol content in the low-phenol wastewater after adsorption is ≤10 mg / L. The adsorption is preferably carried out in an adsorption tower, and the raffinate aqueous phase is preferably sprayed from top to bottom through the packing layer in the adsorption tower in a co-current manner for liquid-solid adsorption. The packing layer in the adsorption tower is filled with adsorption material. In the present application, after the raffinate aqueous phase is adsorbed, the residual total phenol content in the obtained wastewater is below 10 mg / L, which meets the water inlet requirements of the subsequent biochemical treatment system for further treatment of the semi-coke wastewater.

[0060] The method for extracting and recovering phenol from phenol-containing wastewater provided by the application mainly comprises a multistage countercurrent extraction unit, an extractant recovery unit, an adsorption unit and a phenol collection unit. The application provides a phenol removal extractant for phenol-containing semi-coke wastewater. Compared with other commonly used phenolic extractants, the extractant has high extraction efficiency, low water solubility (12.6±0.3 mg / L), high stability, reliable recovery efficiency, and a long service life. The application adopts three-stage countercurrent extraction, and the extraction phase is completely refluxed in the middle, so that the high-efficiency extraction and separation effect can be achieved to the maximum extent, the amount of reagent used is saved, and economic progress is achieved. For high-concentration phenol-containing wastewater with a phenol content of 5000-50000 mg / L, the application adopts adsorption measures to perform re-adsorption treatment on the residual phenolic substances in the raffinate in the subsequent extraction process, so that the residual phenolic substances in the water can be greatly removed. After the method provided by the application is used, the phenol concentration can be reduced to 10 mg / L, which meets the influent requirements of subsequent semi-coke wastewater biochemical treatment.

[0061] In order to further illustrate the application, the technical solutions provided by the application are described in detail below in combination with examples, but they should not be understood as limiting the scope of the application.

[0062] Example 1

[0063] The phenol removal extractant used in this example is: mixing 40 vol% of DMHAA, 50 vol% of di(2,4,4-trimethylpentyl) hypophosphorous acid and 10 vol% of kerosene to obtain extractant A.

[0064] The high-phenol-containing coking wastewater B from a certain enterprise after deoiling and deacidification was used as raw water, and the initial concentration of total phenol was 10500 mg / L. Under the condition of 50℃, the wastewater was introduced into the first-stage extraction unit and mixed with the extractant A and the reflux extractant F. The volume ratio of the extractant A and the reflux extractant F in the first-stage extraction was 1:9, and the volume ratio of the total extractant (A and F) to the wastewater B was 1:4. After the first-stage countercurrent extraction, the first-stage extraction phase H was collected into the back-extraction unit (i.e. the extractant recovery unit), and the first-stage raffinate phase I entered the second-stage extraction unit. The water inlet mode of the second-stage extraction unit was the same as that of the first-stage extraction unit. The volume ratio of the reflux extractant F and the third-stage extraction reflux phase J in the second-stage extraction unit was 1:1, and the total extractant amount (F and J) in the second-stage extraction was the same as the total extractant amount (A and F) in the first-stage extraction. After the second-stage countercurrent extraction, the extraction phase K of the final second-stage extraction unit was collected into the back-extraction unit (i.e. the extractant recovery unit), and the raffinate phase L entered the third-stage extraction unit. The water inlet mode of the third-stage extraction unit was the same as that of the second-stage extraction unit. The volume ratio of the extractant A added in the third-stage extraction to the total extractant amount (A and F) in the first-stage extraction was 3:10, the volume ratio of the reflux extractant F added in the third-stage extraction to the total extractant amount (A and F) in the first-stage extraction was 1:5, and the total volume of the extractant A and the reflux extractant F in the third-stage extraction to the total extractant amount (A and F) in the first-stage extraction was 1:2. Each stage of extraction was separated under the condition of 105 KPa for 30 min. After the third-stage extraction, the extraction phase J was completely refluxed into the second-stage extraction unit, and the raffinate phase was the raffinate wastewater D. The total phenol content in the obtained raffinate phase (raffinate wastewater D) was 100.5 mg / L, and the extraction rate of the extractant for phenols was 79.6%.

[0065] The total phenol content in the dephenolized wastewater obtained after the final adsorption treatment of the raffinate was 8.5 mg / L. The raffinate was treated in the adsorption unit. The raffinate was sprayed from top to bottom in the countercurrent flow through the filler layer in the adsorption tower for liquid-solid adsorption. The adsorption material used in the filler layer was a mixture of gasification slag and coal ash slag at a ratio of 1:1, which was laid with a thickness of about 1.5 m and a bulk density of about 650 kg / m 3 After the adsorption of the raffinate wastewater D, the residual total phenol content in the wastewater was 8.5 mg / L, which was below 10 mg / L, meeting the water inlet requirements of the subsequent biochemical treatment system for the coking wastewater.

[0066] In the extractant recovery unit, the back-extraction agent was selected from a 10wt% NaOH aqueous solution, and the volume ratio of the back-extraction agent to the extraction phase was 1:2. The extraction phases of the first-stage and second-stage extraction units entered the extractant recovery tank, reacted with the back-extraction agent, generated phenyl sodium aqueous solution, entered the phenol collection unit, and the extractant recovery rate was about 90.5%.

[0067] In the phenol collection unit, CO2 is reacted with sodium phenolate aqueous solution to generate crude phenol for recycling and reuse, and excess CO2 overflows from the sodium phenolate tank.

[0068] Example 2

[0069] The dephenolization extractant used in this example is: mixing DMHAA 40 vol%, di(2,4,4-trimethylpentyl) phosphinic acid 50 vol% and kerosene 10 vol% to obtain extractant A.

[0070] Take the high-phenol-containing lignite wastewater B after deoiling and deacidification of a certain enterprise as raw water, wherein the initial concentration of total phenol is 9800 mg / L. Under the condition of 50°C, the deoiled and deacidified phenol-containing lignite wastewater B is introduced into the first-stage extraction by a three-stage countercurrent extraction unit: the first-stage extraction uses extractant A mixed with reflux extractant F, wherein the volume mixing ratio of extractant A and reflux extractant F in the first-stage extraction is 2:8, and the volume ratio of the total extractant amount (A and F) to the phenol-containing lignite wastewater B is 1:4; after the first-stage countercurrent extraction, the first-stage extraction phase H is collected to the back-extraction unit (i.e. extractant recovery unit), and the first-stage extraction residue phase I enters the second-stage extraction unit; the water inlet mode of the second-stage extraction unit is the same as that of the first-stage extraction unit, the volume ratio of the reflux extractant F and the third-stage extraction reflux phase J in the second-stage extraction unit is 1:3, and the total extractant amount (F and J) in the second-stage extraction is the same as the total extractant amount (A and F) in the first-stage extraction; after the second-stage countercurrent extraction, the extraction phase K of the final second-stage extraction unit is collected to the back-extraction unit (i.e. extractant recovery unit), and the extraction residue phase L enters the third-stage extraction unit; the water inlet mode of the third-stage extraction unit is the same as that of the second-stage extraction unit, the volume ratio of the extractant A added in the third-stage extraction to the total extractant amount (A and F) in the first-stage extraction is 1:5, the volume ratio of the reflux extractant F added in the third-stage extraction to the total extractant amount (A and F) in the first-stage extraction is 3:10, and the total volume of the extractant A and the reflux extractant F in the third-stage extraction to the total extractant amount (A and F) in the first-stage extraction is 1:2; after each stage of extraction and separation for 30 min, the third-stage extraction phase J is completely refluxed to the second-stage extraction unit after the third-stage extraction is completed, and the extraction residue phase is the extraction residue wastewater D; the total phenol content in the obtained extraction residue phase (extraction residue wastewater D) is 160.8 mg / L, and the extraction rate of the extractant for phenols is 76.2%.

[0071] The total phenol content in the dephenolized wastewater obtained after the final adsorption treatment of the raffinate is 9.1 mg / L. The raffinate is treated in the adsorption unit, the raffinate is sprayed from top to bottom in the countercurrent mode and flows through the filler layer in the adsorption tower for liquid-solid adsorption. The adsorption material used in the filler layer is a mixture of gasification slag and coal ash slag at a ratio of 1:1, with a laying thickness of about 1.6 m and a bulk density of about 700 kg / m 3The total phenol content in the waste water D after adsorption is 9.1 mg / L, which is below 10 mg / L, meeting the requirement of the subsequent biochemical treatment system for the coke waste water.

[0072] In the extractant recovery unit, the back-extractant is selected from a 10wt% NaOH aqueous solution, and the back-extractant is 1:2 compared with the extract. The first and second stage extraction units enter the extractant recovery tank, react with the back-extractant, generate phenol sodium aqueous solution, enter the phenol collection unit, and the extractant recovery rate is about 90%.

[0073] In the phenol collection unit, CO2 is used to react with the phenol sodium aqueous solution to generate crude phenol for recycling and reuse, and the excess CO2 overflows from the phenol sodium tank.

[0074] Example 3

[0075] The dephenolization extractant used in this example is: mixing DMHAA 50vol%, di(2,4,4-trimethylpentyl) phosphinic acid 40vol% and kerosene 10vol% to obtain extractant A.

[0076] The high-phenol-containing coking wastewater B from a certain enterprise after deoiling and deacidification was used as raw water, and the initial concentration of total phenol was 13000 mg / L. Under the condition of 40℃, the wastewater was introduced into the first-stage extraction unit and mixed with the extractant A and the reflux extractant F. The volume ratio of the extractant A and the reflux extractant F in the first-stage extraction was 1:9, and the volume ratio of the total extractant (A and F) to the wastewater B was 1:4. After the first-stage countercurrent extraction, the first-stage extraction phase H was collected into the back-extraction unit (i.e. the extractant recovery unit), and the first-stage raffinate phase I entered the second-stage extraction unit. The water inlet mode of the second-stage extraction unit was the same as that of the first-stage extraction unit. The volume ratio of the reflux extractant F and the third-stage extraction reflux phase J in the second-stage extraction unit was 1:1, and the total extractant amount (F and J) in the second-stage extraction was the same as that (A and F) in the first-stage extraction. After the second-stage countercurrent extraction, the final second-stage extraction phase K was collected into the back-extraction unit (i.e. the extractant recovery unit), and the raffinate phase L entered the third-stage extraction unit. The water inlet mode of the third-stage extraction unit was the same as that of the second-stage extraction unit. The volume ratio of the extractant A added in the third-stage extraction to the total extractant amount (A and F) in the first-stage extraction was 3:10, the volume ratio of the reflux extractant F added in the third-stage extraction to the total extractant amount (A and F) in the first-stage extraction was 1:5, and the total volume of the extractant A and the reflux extractant F in the third-stage extraction to the total extractant amount (A and F) in the first-stage extraction was 1:2. After 30 min of extraction separation in each stage, the third-stage extraction phase J was completely refluxed into the second-stage extraction unit, and the raffinate phase was the raffinate wastewater D. The total phenol content in the obtained raffinate phase (raffinate wastewater D) was 200.5 mg / L, and the extraction rate of the extractant for phenols was 65.2%.

[0077] The total phenol content in the dephenolized wastewater obtained after the raffinate liquid was finally treated by adsorption was 9.5 mg / L. The raffinate liquid was treated in the adsorption unit. The raffinate liquid flowed from top to bottom in the countercurrent mode and flowed through the filler layer in the adsorption tower for liquid-solid adsorption. The adsorption material in the filler layer was a mixture of gasification slag and coal ash slag at a ratio of 1:1, with a laying thickness of about 1.5 m and a bulk density of about 700 kg / m 3 After the adsorption of the raffinate wastewater D, the residual total phenol content in the wastewater was 9.5 mg / L, which was below 10 mg / L, meeting the water inlet requirements of the subsequent biochemical treatment system for the coking wastewater.

[0078] In the extractant recovery unit, the back-extraction agent was selected from a 10wt% NaOH aqueous solution, and the volume ratio of the back-extraction agent to the extraction phase was 1:2. The extraction phases of the first-stage and second-stage extraction units entered the extractant recovery tank, reacted with the back-extraction agent, generated phenyl sodium aqueous solution, entered the phenol collection unit, and the extractant recovery rate was about 90%.

[0079] In the phenol collection unit, CO2 reacts with sodium phenolate aqueous solution to generate crude phenol for recycling and reuse, and excess CO2 overflows from the sodium phenolate tank.

[0080] Example 4

[0081] The dephenolization extractant used in this example is: mixing 43 vol% of DMHAA, 52 vol% of bis(2,4,4-trimethylpentyl) phosphinic acid and 5 vol% of kerosene to obtain extractant A.

[0082] Take the high-phenol-containing lignite coal wastewater B after deoiling and deacidification of a certain enterprise as raw water, wherein the initial concentration of total phenol is 11060 mg / L. Under the condition of 40℃, the deoiled and deacidified phenol-containing lignite coal wastewater B is introduced into the first-stage extraction by a three-stage countercurrent extraction unit: the first-stage extraction uses extractant A mixed with reflux extractant F, wherein the volume mixing ratio of extractant A and reflux extractant F in the first-stage extraction is 1:9, and the volume ratio of the total extractant amount (A and F) to the phenol-containing lignite coal wastewater B is 1:4; after the first-stage countercurrent extraction, the first-stage extraction phase H is collected to the back-extraction unit (i.e. extractant recovery unit), and the first-stage extraction residue phase I enters the second-stage extraction unit; the water inlet mode of the second-stage extraction unit is the same as that of the first-stage extraction unit, the volume ratio of the reflux extractant F and the third-stage extraction reflux phase J in the second-stage extraction unit is 1:1, and the total extractant amount (F and J) in the second-stage extraction is the same as the total extractant amount (A and F) in the first-stage extraction; after the second-stage countercurrent extraction, the extraction phase K of the final second-stage extraction unit is collected to the back-extraction unit (i.e. extractant recovery unit), and the extraction residue phase L enters the third-stage extraction unit; the water inlet mode of the third-stage extraction unit is the same as that of the second-stage extraction unit, the volume ratio of the extractant A added in the third-stage extraction to the total extractant amount (A and F) in the first-stage extraction is 3:10, the volume ratio of the reflux extractant F added in the third-stage extraction to the total extractant amount (A and F) in the first-stage extraction is 1:5, and the total volume of the extractant A and the reflux extractant F in the third-stage extraction to the total extractant amount (A and F) in the first-stage extraction is 1:2; after each stage of extraction is separated for 20 min, the third-stage extraction phase J is completely refluxed to the second-stage extraction unit after the third-stage extraction is completed, and the extraction residue phase is the extraction residue wastewater D; the total phenol content in the obtained extraction residue phase (extraction residue wastewater D) is 220.7 mg / L, and the extraction rate of the extractant for phenols is 68.2%.

[0083] The total phenol content in the dephenolized wastewater obtained after the extraction residue is finally treated by adsorption is 10.6 mg / L. The extraction residue is treated in the adsorption unit, the extraction residue is sprayed from top to bottom in the countercurrent mode and flows through the filler layer in the adsorption tower for liquid-solid adsorption. The adsorption material used in the filler layer is a mixture of fly ash and coal ash residue in a ratio of 2:1, which is laid with a thickness of about 1.5 m and a bulk density of about 650 kg / m 3The total phenol content in the waste water D after adsorption is 10.6 mg / L, which is below 10 mg / L, meeting the requirement of the subsequent biochemical treatment system for the coke waste water.

[0084] In the extractant recovery unit, the back-extractant is selected from a 10wt% NaOH aqueous solution, and the back-extractant is 1:2 compared with the extract. The first and second stage extraction units enter the extractant recovery tank, react with the back-extractant, generate phenol sodium aqueous solution, enter the phenol collection unit, and the extractant recovery rate is about 90%.

[0085] In the phenol collection unit, CO2 is used to react with the phenol sodium aqueous solution to generate crude phenol for recycling, and the excess CO2 overflows from the phenol sodium tank.

[0086] Example 5

[0087] The dephenolization extractant used in this example is: mixing DMHAA 40vol%, di(2,4,4-trimethylpentyl) phosphinic acid 50vol% and kerosene 10vol% to obtain extractant A.

[0088] The high-phenol-containing coking wastewater B from a certain enterprise after deoiling and deacidification was used as raw water, and the initial concentration of total phenol was 22100 mg / L. Under the condition of 40℃, the wastewater was introduced into the first-stage extraction unit and mixed with the extractant A and the reflux extractant F. The volume ratio of the extractant A and the reflux extractant F in the first-stage extraction was 2:8, and the volume ratio of the total extractant (A and F) to the wastewater B was 1:3. After the first-stage countercurrent extraction, the first-stage extraction phase H was collected into the back-extraction unit (i.e. the extractant recovery unit), and the first-stage raffinate phase I entered the second-stage extraction unit. The water inlet mode of the second-stage extraction unit was the same as that of the first-stage extraction unit. The volume ratio of the reflux extractant F and the third-stage extraction reflux phase J in the second-stage extraction unit was 1:1, and the total extractant amount (F and J) in the second-stage extraction was the same as that (A and F) in the first-stage extraction. After the second-stage countercurrent extraction, the final second-stage extraction phase K was collected into the back-extraction unit (i.e. the extractant recovery unit), and the raffinate phase L entered the third-stage extraction unit. The water inlet mode of the third-stage extraction unit was the same as that of the second-stage extraction unit. The volume ratio of the extractant A added in the third-stage extraction to the total extractant amount (A and F) in the first-stage extraction was 1:10, the volume ratio of the reflux extractant F added in the third-stage extraction to the total extractant amount (A and F) in the first-stage extraction was 2:5, and the total volume of the extractant A and the reflux extractant F in the third-stage extraction to the total extractant amount (A and F) in the first-stage extraction was 1:2. After 20 min of extraction separation in each stage, the third-stage extraction phase J was completely refluxed into the second-stage extraction unit, and the raffinate phase was the raffinate wastewater D. The total phenol content in the obtained raffinate phase (raffinate wastewater D) was 240.5 mg / L, and the extraction rate of the extractant for phenols was 60.4%.

[0089] The total phenol content in the dephenolized wastewater obtained after the final adsorption treatment of the raffinate was 12.7 mg / L. The raffinate was treated in the adsorption unit. The raffinate was sprayed from top to bottom in the flow direction and flowed through the filler layer in the adsorption tower for liquid-solid adsorption. The adsorption material in the filler layer was a mixture of gasification slag and fly ash at a ratio of 2:1, with a laying thickness of about 1.5 m and a bulk density of about 700 kg / m 3 After the adsorption of the raffinate wastewater D, the residual total phenol content in the wastewater was 12.7 mg / L, which was below 10 mg / L, meeting the water inlet requirements of the subsequent biochemical treatment system for the coking wastewater.

[0090] In the extractant recovery unit, the back-extraction agent was selected from a 10wt% NaOH aqueous solution, and the volume ratio of the back-extraction agent to the extraction phase was 1:2. The extraction phases of the first-stage and second-stage extraction units entered the extractant recovery tank, reacted with the back-extraction agent, generated phenolate sodium aqueous solution, and entered the phenol collection unit. The extractant recovery rate was about 90%.

[0091] In the phenol collection unit, CO2 reacts with sodium phenolate aqueous solution to generate crude phenol for recycling and reuse, and excess CO2 overflows from the sodium phenolate tank.

[0092] Comparative Example 1

[0093] The method is basically the same as that of Example 1, except that the extractant used in the present comparative example is DMHAA, i.e. the present comparative example uses the same amount of DMHAA as Example 1. By calculation, the extraction rate of the extractant for phenols is 60.5%, and the total phenol content in the dephenolized wastewater after treatment is 220.6 mg / L.

[0094] Comparative Example 2

[0095] The method is basically the same as that of Example 2, except that the extractant used in the present comparative example is a mixture of DMHAA 40 vol% and di(2,4,4-trimethylpentyl) hypophosphorous acid 60 vol% to obtain extractant A. By calculation, the extraction rate of the extractant for phenols is 50.6%, and the total phenol content in the dephenolized wastewater after treatment is 121.9 mg / L.

[0096] Comparative Example 3

[0097] The method is basically the same as that of Example 2, except that the extractant used in the present comparative example is a mixture of DMHAA 40 vol% and di(2,4,4-trimethylpentyl) hypophosphorous acid 60 vol% to obtain extractant A. By calculation, the extraction rate of the extractant for phenols is 50.6%, and the total phenol content in the dephenolized wastewater after treatment is 121.9 mg / L.

[0098] In the present example, the mixed extractant prepared according to the preferred scheme is used for three-stage countercurrent extraction of high-phenol lignite wastewater, which can effectively improve the extraction efficiency of phenols. Compared with the comparative analysis, the extraction rate of the above-mentioned mixed extractant is significantly improved, which can reach up to 79.2%, and at the same time, the emission of water-soluble by-products can be reduced, and the subsequent biochemical treatment load can be reduced. The above-mentioned mixed extractant is used for high-phenol lignite wastewater extraction according to the extraction method provided by the present application, which can achieve a higher phenol extraction rate.

[0099] Although the above examples have made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained under the premise of no creativity according to the present embodiments, which all belong to the protection scope of the present application.

Claims

1. A method for recovering phenol from phenol-containing wastewater by extraction, characterized by, The method comprises the following steps: The phenol-containing wastewater is subjected to multi-stage countercurrent extraction with a dephenolizing extractant to obtain a phenol-containing organic phase and a raffinate water phase; the phenol-containing wastewater is semi-coke wastewater, and the total phenol content of the semi-coke wastewater is 5000-50000 mg / L; the dephenolizing extractant comprises the following components in volume percentage: N,N-di(1-methyl-heptyl)acetamide 40-60%, di(2,4,4-trimethylpentyl) hypophosphorous acid 30-55%, and an organic dispersant 1-10%; the organic dispersant comprises kerosene and / or cumene; the extraction stage number of the multi-stage countercurrent extraction is 3; the temperature of each stage of extraction is 30-55 ℃, the time of each stage of extraction is 10-30 min, and the operating pressure of each stage of extraction is 105-130 kPa; The method for 3-stage countercurrent extraction comprises the following steps: The phenol-containing wastewater is subjected to first-stage countercurrent extraction with a first extractant to obtain a first-stage extraction phase and a first-stage raffinate phase; The first-stage raffinate phase is subjected to second-stage countercurrent extraction with a second extractant to obtain a second-stage extraction phase and a second-stage raffinate phase; the first-stage extraction phase and the second-stage extraction phase are the phenol-containing organic phase; The second-stage raffinate phase is subjected to third-stage countercurrent extraction with a third extractant to obtain a third-stage extraction phase and a third-stage raffinate phase; after the third-stage extraction phase is obtained, the third-stage extraction phase is further used to replace part of the second extractant; the third-stage raffinate phase is the raffinate water phase; The phenol-containing organic phase is subjected to back extraction with a back extraction agent to obtain a phenolate aqueous solution and recovered extractant; the back extraction agent is an inorganic alkali aqueous solution, and the volume ratio of the back extraction agent to the phenol-containing organic phase is 1:1.8-1:2.3; the recovered extractant is reused in at least one of the first-stage countercurrent extraction, the second-stage countercurrent extraction and the third-stage countercurrent extraction; CO2 is introduced into the phenolate aqueous solution to obtain a crude phenol product; the raffinate water phase is subjected to adsorption with an adsorption material to obtain low-phenol wastewater, and the adsorption material comprises one or more of gasified slag, coal ash slag and fly ash; the total phenol content in the low-phenol wastewater after adsorption is ≤10 mg / L.

2. The method of claim 1, wherein, When the recovered extractant is reused in the first-stage countercurrent extraction, the recovered extractant replaces part of the first extractant, and the volume ratio of the remaining first extractant to the recovered extractant used in the first-stage countercurrent extraction is 1-2:8-9; the volume ratio of the first extractant to the phenol-containing wastewater is 1-1.5:3-5.

3. The method according to claim 1 or 2, characterized in that, When the recovered extractant is reused in the second-stage countercurrent extraction, the recovered extractant replaces the remaining second extractant, and the volume ratio of the recovered extractant used in the second-stage countercurrent extraction to the third-stage extraction phase is 1-2:2-4; the volume ratio of the second extractant to the first extractant is 1:

1.

4. The method according to claim 1 or 2, characterized in that, When the recovered extractant is reused in the third-stage countercurrent extraction, the recovered extractant replaces part of the third extractant, and the volume ratio of the remaining third extractant to the recovered extractant used in the third-stage countercurrent extraction is 2-3:1-3; the volume ratio of the third extractant to the first extractant is 1:1-3.

Images