High-phenol and high-salt industrial wastewater treatment process

Abstract

The invention belongs to the technical field of wastewater treatment, and particularly relates to a high-phenol high-salt industrial wastewater treatment process which comprises the following steps: S1, preparing a composite extracting agent, S2, extracting phenol, S3, regenerating the extracting agent, S4, pretreating a dephenolized water phase, and S5, evaporating and desalting. Compared with the prior art, the invention has the following beneficial effects: through compounding of tributyl phosphate and kerosene, the addition of kerosene can enhance hydrophobicity by reducing viscosity, dispersing tributyl phosphate molecules and retaining tributyl phosphate at the same time, the extraction efficiency of phenol is greatly improved, the extraction efficiency is high, the maximum extraction rate of phenol is high, and the method is suitable for industrial production. The phenol extraction rate can reach 95.5% after extraction is carried out for 1.5 hours, and the maximum phenol extraction rate is stabilized at 97.2% after extraction is carried out for 2 hours.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, in particular to a high-phenol and high-salt industrial wastewater treatment process. BACKGROUND

[0002] High-phenol and high-salt industrial wastewater is a common type of difficult-to-treat wastewater in industrial production. Phenol has high toxicity and strong corrosivity, and is chemically stable. If it is directly discharged, it will seriously pollute the water environment and harm the ecological system and human health. At the same time, high concentrations of salts such as sodium chloride and sodium sulfate in the wastewater will inhibit microbial activity, making it difficult to directly apply traditional biochemical treatment processes.

[0003] In existing treatment technologies, the methods for removing phenol mainly include distillation, adsorption, and extraction. Distillation separates phenol from water by taking advantage of their different boiling points. However, phenol and water have azeotropic behavior, with azeotropic temperature of 99.95℃ and azeotropic ratio of about 47.4%. This results in high energy consumption for distillation, and the distillate still contains a large amount of phenol, which is not completely treated. Adsorption often uses activated carbon, resin, and other adsorbents, but the adsorbent capacity is limited, and the adsorbent needs to be regenerated frequently, which is costly and can generate secondary solid waste. Traditional extraction methods often use a single extractant, which has low extraction efficiency, is difficult to regenerate, and has high solvent loss.

[0004] For the high-salt characteristics, existing technologies often use evaporation desalination. However, if phenol is not completely removed from the wastewater, due to the azeotropic behavior of phenol and water, phenol will enter the subsequent treatment system with the evaporation distillate, causing the biochemical treatment unit to be poisoned and fail to achieve standard discharge. Therefore, developing a treatment process that can simultaneously achieve efficient recovery of phenol and effective separation of salts, while also considering economic efficiency and environmental protection, has become a technical problem that needs to be solved urgently. SUMMARY

[0005] The purpose of the present application is to provide a high-phenol and high-salt industrial wastewater treatment process to solve the problems raised in the background.

[0006] A high-phenol and high-salt industrial wastewater treatment process, the steps are as follows: S1, composite extractant configuration, The composite extractant is prepared by uniformly mixing tributyl phosphate and kerosene at a volume ratio of 2.5-3.5:7 at room temperature; S2, phenol extraction, The composite extractant is mixed with industrial wastewater at a volume ratio of 1-1.5:1, and stirred and extracted at room temperature. After standing and layering, an organic phase containing phenol and a dephenolized water phase are obtained; S3, extractant regeneration, Mixing reaction of the organic phase with 20%-30% mass fraction of sodium hydroxide solution, converting phenol in the organic phase into sodium phenolate into the sodium hydroxide solution, after standing and layering, the upper layer is regenerated composite extractant, the regenerated composite extractant is recycled and applied in S2, and the lower layer is the alkaline solution phase containing sodium phenolate; S4, pretreatment of the phenol-removed aqueous phase, Adding flaky sodium hydroxide into the phenol-removed aqueous phase, converting residual phenol in the aqueous phase into sodium phenolate, obtaining a pretreated aqueous phase; S5, evaporation and desalination, Sending the pretreated aqueous phase into a three-effect evaporation system for evaporation and concentration, sending the distillate generated in the evaporation into a biochemical treatment system, and centrally disposing the solid salt evaporated.

[0007] As a preferred embodiment of the above technical solution, the kerosene in S1 comprises the following components in mass fraction: cycloalkane 30%-40%, n-alkane 50%-60% and aromatic hydrocarbon 0-1%.

[0008] As a preferred embodiment of the above technical solution, the normal temperature in S1 is 20-25℃.

[0009] As a preferred embodiment of the above technical solution, in the phenol extraction in S2, the composite extractant is mixed with industrial wastewater at a volume ratio of 1:1, stirring extraction is carried out at normal temperature for 2h, and standing and layering are carried out to obtain an organic phase containing phenol and a phenol-removed aqueous phase.

[0010] As a preferred embodiment of the above technical solution, the normal temperature in S2 is 20-25℃, and the stirring rate is 150-200r / min.

[0011] As a preferred embodiment of the above technical solution, the reaction time of the organic phase with the sodium hydroxide solution in S3 is 30-45min, and the reaction temperature is controlled to be 30-40℃.

[0012] As a preferred embodiment of the above technical solution, the flaky sodium hydroxide is added in S4 in a batch manner and stirring, and the pH value of the system is adjusted to be above 12.

[0013] As a preferred embodiment of the above technical solution, the alkaline solution phase in S3 is used for recovering phenol, and the process is as follows: converting sodium phenolate into phenol through acidification and reduction.

[0014] As a preferred embodiment of the above technical solution, the acidification and reduction is carried out by adopting a process of passing in CO2 to acidify and reduce sodium phenolate into phenol.

[0015] As a preferred embodiment of the above technical solution, the alkaline solution phase in S3 is used as a raw material for synthesizing phenolic resin.

[0016] Compared with the prior art, the present application has the following beneficial effects: 1、The present application greatly improves the extraction efficiency of phenol by compounding tributyl phosphate with kerosene, and the addition of kerosene can reduce the viscosity, disperse tributyl phosphate molecules, enhance hydrophobicity, and retain tributyl phosphate, thereby greatly improving the extraction efficiency of phenol, and the maximum extraction rate of phenol is high, and the phenol extraction rate can reach 95.5% after 1.5 hours of extraction, and the maximum phenol extraction rate is stable at 97.2% after 2 hours of extraction.

[0017] 2、The present application adopts a composite extraction agent, and the transfer rate of sodium chloride in industrial wastewater is less than 6.6% during a long extraction process, which greatly reduces the difficulty of subsequent resource processing.

[0018] 3、The boiling point of phenol is 182℃, and the boiling point of phenol is 181.8℃ at standard atmospheric pressure (101.325 kPa), and the temperature of the azeotrope with water is 99.95℃, and the azeotrope ratio is about 47.4%, so phenol will enter the fraction; phenol sodium and water are not azeotropic, and will not enter the fraction; phenol sodium is a salt generated by the reaction of phenol and sodium hydroxide, in which the hydroxyl group in phenol and the hydroxyl ion in sodium hydroxide undergo a substitution reaction to form an ionic bond between the phenol sodium cation and the sodium hydroxide anion, thereby forming a new compound, phenol sodium. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The process flow chart of the present application. DETAILED DESCRIPTION

[0020] The technical solutions of the present application will be described below in combination with the embodiments of the present application.

[0021] Example 1: A high-phenol high-salt industrial wastewater treatment process, the steps are as follows: S1, composite extraction agent configuration, The composite extraction agent is prepared by uniformly mixing 300mL of tributyl phosphate and 700mL of kerosene at a temperature of 20-25℃; S2, phenol extraction, Mix 1000mL of the composite extraction agent with 1000mL of industrial wastewater, stir at 150r / min at a temperature of 20℃ for 2h, and separate the organic phase containing phenol and the dephenolized water phase after standing; S3, extraction agent regeneration, Mix the organic phase with a 20% mass fraction of sodium hydroxide solution at 30℃ for 30min, so that the phenol in the organic phase is converted into sodium phenolate into the sodium hydroxide solution, and after standing and separating, the upper layer is the regenerated composite extraction agent, which is returned to S2 for recycling, and the lower layer is the alkali phase containing sodium phenolate; S4, dephenolized water phase pretreatment, The flaky sodium hydroxide is added into the dephenolated water phase in batches and stirred to adjust the pH value of the system to above 12, so that the residual phenol in the water phase is converted into sodium phenolate, and a pretreated water phase is obtained; S5, evaporation desalination, The pretreated water phase is sent into a three-effect evaporation system for evaporation concentration, the distillate generated by evaporation is sent into a biochemical treatment system, and the solid salt evaporated is disposed.

[0022] Example 2: A high-phenol and high-salt industrial wastewater treatment process, the steps are as follows: S1, composite extractant configuration, The composite extractant is prepared by uniformly mixing tributyl phosphate 250 mL and kerosene 700 mL at 22°C; S2, phenol extraction, The composite extractant 950 mL is mixed with industrial wastewater 1140 mL, stirred at 180 r / min at 22°C for 2 h, and then separated to obtain an organic phase containing phenol and a dephenolated water phase; S3, extractant regeneration, The organic phase is mixed with a 25% mass fraction sodium hydroxide solution at 35°C for 40 min, so that the phenol in the organic phase is converted into sodium phenolate and enters the sodium hydroxide solution, and after standing and separating, the upper layer is the regenerated composite extractant, which is recycled and used in S2, and the lower layer is the alkaline phase containing sodium phenolate; S4, dephenolated water phase pretreatment, The flaky sodium hydroxide is added into the dephenolated water phase in batches and stirred to adjust the pH value of the system to above 12, so that the residual phenol in the water phase is converted into sodium phenolate, and a pretreated water phase is obtained; S5, evaporation desalination, The pretreated water phase is sent into a three-effect evaporation system for evaporation concentration, the distillate generated by evaporation is sent into a biochemical treatment system, and the solid salt evaporated is disposed.

[0023] Example 3: A high-phenol and high-salt industrial wastewater treatment process, the steps are as follows: S1, composite extractant configuration, The composite extractant is prepared by uniformly mixing tributyl phosphate 350 mL and kerosene 700 mL at 25°C; S2, phenol extraction, The composite extractant 1050 mL is mixed with industrial wastewater 1575 mL, stirred at 200 r / min at 25°C for 2 h, and then separated to obtain an organic phase containing phenol and a dephenolated water phase; S3, extractant regeneration, The organic phase is mixed with a 30% mass fraction sodium hydroxide solution at 40°C for 45 min, so that the phenol in the organic phase is converted into sodium phenolate into the sodium hydroxide solution, after standing and layering, the upper layer is the regenerated composite extractant, the regenerated composite extractant is returned to S2 for recycling, and the lower layer is the alkaline phase containing sodium phenolate; S4, phenol removal water phase pretreatment, Flaky sodium hydroxide is added to the phenol removal water phase in batches and stirred to adjust the pH value of the system to above 12, so that the residual phenol in the water phase is converted into sodium phenolate, and a pretreated water phase is obtained; S5, evaporation desalination, The pretreated water phase is sent to a three-effect evaporation system for evaporation and concentration, the fraction produced by evaporation is sent to a biochemical treatment system, and the solid salt evaporated is disposed of.

[0024] Comparative Example 1: Compared with Example 1, the difference is that n-butanol is used as the extractant, 1000 mL of n-butanol is mixed with 1000 mL of industrial wastewater, and the mixture is extracted at 20°C and 150 r / min, and then the organic phase containing phenol and the phenol removal water phase are obtained by standing and layering.

[0025] Comparative Example 2: Compared with Example 1, the difference is that cyclohexanone is used as the extractant, 1000 mL of cyclohexanone is mixed with 1000 mL of industrial wastewater, and the mixture is extracted at 20°C and 150 r / min, and then the organic phase containing phenol and the phenol removal water phase are obtained by standing and layering.

[0026] Comparative Example 3: Compared with Example 1, the difference is that ethyl acetate is used as the extractant, 1000 mL of ethyl acetate is mixed with 1000 mL of industrial wastewater, and the mixture is extracted at 20°C and 150 r / min, and then the organic phase containing phenol and the phenol removal water phase are obtained by standing and layering.

[0027] Comparative Example 4: Compared with Example 1, the difference is that toluene is used as the extractant, 1000 mL of toluene is mixed with 1000 mL of industrial wastewater, and the mixture is extracted at 20°C and 150 r / min, and then the organic phase containing phenol and the phenol removal water phase are obtained by standing and layering.

[0028] Comparative Example 5: Compared with Example 1, the difference is that tributyl phosphate is used as the extractant, 1000 mL of tributyl phosphate is mixed with 1000 mL of industrial wastewater, and the mixture is extracted at 20°C and 150 r / min, and then the organic phase containing phenol and the phenol removal water phase are obtained by standing and layering.

[0029] The industrial wastewater with a phenol concentration of 8000 mg / L, a salt content of 12.3 g of sodium chloride, and a pH value of 6.5 was used as the extraction object, and the phenol extraction of the industrial wastewater was carried out by using the eight extraction schemes provided in Examples 1-3 and Comparative Examples 1-5. The results of the phenol extraction rate (%) of different extractants with time are shown in Table 1, and the results of the sodium chloride transfer amount (mg) of different extractants with time are shown in Table 2: Table 1: Phenol extraction rate (%) of different extractants with time ; As shown in Table 1, the composite extractant used in Examples 1-3 can greatly improve the extraction efficiency of phenol by compounding tributyl phosphate and kerosene. The addition of kerosene can reduce the viscosity, disperse tributyl phosphate molecules, and enhance the hydrophobicity while retaining tributyl phosphate. The maximum extraction rate of phenol is high, and the phenol extraction rate can reach 95.5% after 1.5 hours of extraction and stabilize at 97.2% after 2 hours of extraction.

[0030] In Comparative Example 1, n-butanol is used as the extractant. As a commonly used alcohol extractant, n-butanol has moderate extraction efficiency and low maximum extraction rate of phenol. The maximum extraction rate of phenol stabilizes at 67% after 3.5 hours of extraction. In addition, alcohol extractants need to be distilled for regeneration, which is energy-consuming. Therefore, alcohol extractants are generally not regenerated, resulting in a large amount of alcohol extractant used and high cost.

[0031] In Comparative Example 2, cyclohexanone is used as the extractant. As a commonly used ketone extractant, cyclohexanone has high extraction efficiency and high maximum extraction rate of phenol. The phenol extraction rate can reach 83.4% after 2.5 hours of extraction and stabilize at 84.3% after 3 hours of extraction. However, single ketone extractants have similar disadvantages as alcohol extractants, i.e., difficult regeneration, resulting in a large amount of ketone extractant used and high cost.

[0032] In Comparative Example 3, ethyl acetate is used as the extractant. As a commonly used ester extractant, ethyl acetate has high extraction efficiency, but the maximum extraction rate of phenol is generally low. The phenol extraction rate can reach 65.2% after 2 hours of extraction and stabilize at 70.1% after 3.5 hours of extraction. However, ester extractants have general hydrophobicity and are easy to back-extract sodium chloride in the dephenolized water phase, making subsequent resource processing difficult.

[0033] In Comparative Example 4, toluene is used as the extractant. As a commonly used single aromatic hydrocarbon extractant, toluene has the advantage of low price, but has low extraction efficiency and low maximum extraction rate of phenol. In addition, aromatic hydrocarbons and phenol compete for extraction sites, which can lead to secondary pollution of the dephenolized water phase and increase the difficulty of subsequent processing.

[0034] The tributyl phosphate is used as the extractant in the comparative example 5, the viscosity of the tributyl phosphate is about 3.5-4.0 mPa・s at normal temperature, the high viscosity leads to that the tributyl phosphate is difficult to disperse into small droplets when mixing with the industrial wastewater, the two-phase contact area is greatly reduced, the mass transfer resistance is significantly increased, and the experimental results show that the extraction rate of phenol is only 71.2% after 4 hours of extraction, and the extraction time needs to be further prolonged, which leads to that the extraction time is far more than 4 hours, and the economic benefit is low.

[0035] Table 2: sodium chloride transfer amount (mg) in different extractants changes with time ; It can be known from the above table 2 that the composite extractant used in the embodiment 1 to the embodiment 3 has a sodium chloride transfer amount of only 810 mg in the industrial wastewater in a long-time extraction process, and the transfer rate is less than 6.6%, which greatly reduces the difficulty of subsequent resource processing.

[0036] The cyclohexanone is used as the extractant in the comparative example 2, although the extraction rate is high and the extraction speed is fast, but in a long-time extraction process, the sodium chloride transfer amount in the industrial wastewater also increases with the extraction time, and the sodium chloride transfer amount is as high as 3630 mg when the maximum phenol extraction rate is reached after 3 hours of extraction, and the transfer rate is as high as 29.5%, which obviously causes that the subsequent resource processing difficulty is greatly increased.

[0037] In summary, the single extractant used in the comparative example 1, the comparative example 3, the comparative example 4 and the comparative example 5 has the problems of low phenol extraction rate, low extraction speed, high cost of recycling and reusing, high sodium chloride transfer rate in the industrial wastewater in a long-time extraction process, and high cost of subsequent resource processing; the cyclohexanone is used as the extractant in the comparative example 2, although the extraction rate is high and the extraction speed is fast, but the sodium chloride transfer rate is as high as 29.5% in a long-time extraction process, which also has the problem of high cost of subsequent resource processing.

[0038] Application examples 1-8 The application examples 1-8 are compared with the embodiment 1, the mass fractions of the naphthenes, the normal alkanes and the aromatics in the kerosene are changed, and the specific examples are as follows in the following table 3: Table 3: mass fractions of naphthenes, normal alkanes and aromatics in kerosene ; The kerosene in the application examples 1-8 is selected, and the process in the embodiment 1 is used to treat the industrial wastewater, and the results of the phenol extraction rate (%) changing with time are as follows in the following table 4: Table 4: results of phenol extraction rate (%) changing with time in different kerosenes ; From Table 4 above, it can be inferred that the content of aromatic hydrocarbons can affect the extraction rate of kerosene to phenol, the higher the content of aromatic hydrocarbons, the longer the time for the extractant to reach the maximum extraction amount of phenol; and the ratio of naphthenes and n-alkanes can affect the maximum extraction rate of the extractant to phenol.

[0039] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are only by way of example and that changes, modifications, substitutions and alterations can be made thereto without departing from the spirit and scope of the application as defined in the following claims, in which:

Claims

1. A process for treating high-phenol, high-salt industrial wastewater, characterized in that, The steps are as follows: S1, Preparation of compound extractant The composite extractant is prepared by uniformly mixing tributyl phosphate and kerosene at a volume ratio of 2.5-3.5:7 at room temperature; S2, phenol extraction The composite extractant was mixed with industrial wastewater at a volume ratio of 1-1.5:1, and the mixture was stirred and extracted at room temperature. After standing and separating, an organic phase containing phenol and a dephenolized aqueous phase were obtained. S3, Extractant Regeneration The organic phase is mixed with a 20%-30% mass fraction sodium hydroxide solution to react, so that the phenol in the organic phase is converted into sodium phenolate and enters the sodium hydroxide solution. After standing and separating into layers, the upper layer is the regenerated composite extractant, which is returned to S2 for recycling, and the lower layer is the alkaline liquid phase containing sodium phenolate. S4. Pretreatment of the aqueous phase for phenol removal Add flake sodium hydroxide to the dephenolized aqueous phase to convert the residual phenol in the aqueous phase into sodium phenolate, thus obtaining a pretreated aqueous phase; S5, Evaporation and Desalination The pretreated aqueous phase is fed into a triple-effect evaporation system for evaporation and concentration. The distillate produced by evaporation enters a biochemical treatment system, and the evaporated solid salt is centrally disposed of.

2. The high-phenol, high-salt industrial wastewater treatment process according to claim 1, characterized in that: The kerosene described in S1 contains the following components by mass fraction: 30%-40% cycloalkanes, 50%-60% n-alkanes, and 0-1% aromatics.

3. The high-phenol, high-salt industrial wastewater treatment process according to claim 2, characterized in that: The ambient temperature mentioned in S1 is 20-25℃.

4. The high-phenol, high-salt industrial wastewater treatment process according to claim 2, characterized in that: Phenol extraction in S2 involves mixing the composite extractant with industrial wastewater at a volume ratio of 1:1, stirring and extracting at room temperature for 2 hours, and allowing the mixture to stand and separate into layers to obtain an organic phase containing phenol and a dephenolized aqueous phase.

5. The high-phenol, high-salt industrial wastewater treatment process according to claim 2 or 4, characterized in that: The ambient temperature described in S2 is 20-25℃, and the stirring rate is 150-200r / min.

6. The high-phenol, high-salt industrial wastewater treatment process according to claim 2, characterized in that: The reaction time between the organic phase and the sodium hydroxide solution in S3 is 30-45 min, and the reaction temperature is controlled at 30-40℃.

7. The high-phenol, high-salt industrial wastewater treatment process according to claim 2, characterized in that: The flake sodium hydroxide in S4 is added in batches with stirring, and the pH of the system is adjusted to above 12.

8. The high-phenol, high-salt industrial wastewater treatment process according to claim 2, characterized in that, The alkaline phase described in S3 is used to recover phenol, and the process is as follows: sodium phenolate in it is converted into phenol by acidification and reduction.

9. The high-phenol, high-salt industrial wastewater treatment process according to claim 8, characterized in that: The acidification and reduction process involves using CO2 to acidify and reduce sodium phenolate to phenol.

10. The high-phenol, high-salt industrial wastewater treatment process according to claim 2, characterized in that: The alkaline phase described in S3 is used as a raw material for the synthesis of phenolic resin.

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