A phenolic wastewater treatment process and system

Abstract

The application provides a phenol-containing wastewater treatment process and a treatment system. The treatment process comprises the following steps: (1) evaporating the phenol-containing wastewater to obtain a first gas phase stream and a first liquid phase stream; (2) introducing the first liquid phase stream into a first electrochemical advanced oxidation treatment unit to perform electrolysis treatment, and obtaining a second liquid phase stream; (3) introducing the second liquid phase stream into a second electrochemical advanced oxidation treatment unit to perform electrolysis treatment, and obtaining a clear liquid after solid-liquid separation, which can be discharged. The treatment system comprises an evaporation concentration unit, a first electrochemical advanced oxidation treatment unit, a second electrochemical advanced oxidation treatment unit and a solid-liquid separation unit. The process method combining evaporation concentration and two-stage electrochemical advanced oxidation treatment greatly simplifies the treatment process of high-concentration phenol-containing wastewater, and the treated wastewater can be discharged.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and specifically relates to a treatment process and system for phenol-containing wastewater. Background Technology

[0002] The large quantities of high-concentration phenol-containing wastewater generated during oil refining, coking, coal chemical, papermaking, pharmaceutical, and furfural production processes represent one of the most pressing wastewater problems. This type of wastewater typically has a concentration exceeding 1000 mg / L, a complex composition, and contains large amounts of highly toxic and recalcitrant phenolic organic compounds, exhibiting poor biodegradability. Discharge of untreated phenol-containing wastewater poses a serious threat to human health and the Earth's ecosystem. Therefore, the efficient treatment of high-concentration phenol-containing wastewater is of great significance for environmental protection and is currently a hot research topic.

[0003] Currently, the main methods for treating phenol-containing wastewater include physical methods such as adsorption, extraction, and membrane separation; biodegradation methods; and chemical oxidation methods such as ozone oxidation, wet oxidation, photocatalytic oxidation, and electrocatalytic oxidation. High-concentration phenol-containing wastewater, due to its high pollutant content and complex composition, typically requires a combination of two or more processes for the resource recovery of phenols or the oxidative degradation of all organic pollutants. However, the resource recovery of phenols is complex, lengthy, and costly, with limited economic value. Therefore, oxidative degradation is the best treatment method. Among various oxidative degradation methods, electrochemical advanced oxidation processes (EAOPs) offer advantages such as mild reaction conditions, high safety, simple equipment, convenient operation, and the elimination of the need for additional reagents, reducing secondary pollution. These advantages make EAOPs one of the most promising technologies for treating phenol-containing wastewater. EAOPs refer to the process where, under the influence of electrical energy, organic pollutants are reacted with strong oxidizing substances such as ·OH and SO42- generated on the anode surface. ·- Oxygen ions (O3), hydrogen ions (H2O2), and other organic compounds are oxidized to ultimately produce CO2 and H2O. The electrical energy consumed can come from renewable energy sources.

[0004] Currently, existing technologies mainly employ a combination of electro-Fenton electrochemical processes (EAOPs) and other processes to treat phenol-containing wastewater. CN201811416474.9 discloses a synergistic electro-Fenton and biological treatment method for phenol-containing wastewater. First, the phenol-containing wastewater, after pH and electrolyte concentration adjustment, undergoes an electro-Fenton reaction. Then, after filtration, it is sequentially passed through anaerobic and aerobic reactors for biodegradation. This method improves the biodegradability of the wastewater and the efficiency of subsequent biological treatment. CN202110204063.9 discloses a device and method for the combined treatment of high-concentration phenol-containing wastewater using centrifugal extraction and electrocatalysis. First, multiple centrifugal extractors connected in series efficiently remove phenol to obtain low-concentration phenol-containing wastewater; then, electrolytic treatment using electrocatalysis technology is performed to bring the phenol content up to emission standards. However, existing combined processes involving EAOPs are generally long and complex, leading to problems such as high energy consumption, poor device stability, short electrode material lifespan, and high treatment costs. Therefore, there is an urgent need to develop a new electrolysis technology with a simple treatment process to efficiently treat high-concentration phenol-containing wastewater. Summary of the Invention

[0005] To address the problems of existing technologies, this invention provides a phenol-containing wastewater treatment process and system. It employs a combined process of evaporation concentration and two-stage electrochemical advanced oxidation treatment, greatly simplifying the treatment flow for high-concentration phenol-containing wastewater. Simultaneously, by adjusting the type of boron-doped diamond (BDD) electrode matrix material and corresponding process parameters according to water quality conditions, it ensures compatibility with the wastewater treatment system, solving the problems of low current efficiency and poor electrochemical stability caused by poor compatibility between electrode materials and the wastewater system. Ultimately, this effectively reduces the COD value and phenol content of the wastewater, enabling the treated wastewater to meet discharge standards.

[0006] The technical solution of the present invention is as follows:

[0007] The first aspect of this invention provides a process for treating phenol-containing wastewater, comprising the following steps:

[0008] (1) The phenol-containing wastewater is evaporated to obtain the first gas phase stream and the first liquid phase stream;

[0009] (2) The first liquid phase stream obtained in step (1) enters the first electrochemical advanced oxidation treatment unit for electrolysis treatment, and the second liquid phase stream is obtained after treatment.

[0010] (3) The second liquid phase stream obtained in step (2) enters the second electrochemical advanced oxidation treatment unit for electrolysis treatment, and the third liquid phase stream is obtained after treatment.

[0011] (4) The third liquid phase material obtained in step (3) is separated into solid and liquid phases, and the resulting clear liquid is discharged in compliance with standards.

[0012] Furthermore, in the above-mentioned phenol-containing wastewater treatment process, the phenol-containing wastewater mentioned in step (1) is high-concentration phenol-containing wastewater, wherein the COD is 10,000 to 100,000 mg / L, preferably 30,000 to 60,000 mg / L; the phenol content is 1,000 to 8,000 mg / L, preferably 2,000 to 5,000 mg / L; and the conductivity is preferably not less than 3,000 μS / cm.

[0013] Furthermore, in the above-mentioned phenol-containing wastewater treatment process, the phenol-containing wastewater in step (1) can optionally undergo oil removal treatment, especially when the oil content in the phenol-containing wastewater is greater than or equal to 20 mg / L, it is preferable to first perform oil removal treatment. The oil removal treatment can be any one of gravity sedimentation oil removal, air flotation oil removal, ceramic membrane oil removal, oleophobic membrane oil removal, activated carbon adsorption, etc. Gravity sedimentation oil removal is preferred. The phenol-containing wastewater is sent to a gravity oil removal tank and, after settling, the oil-removed wastewater is obtained. The specific settling time is 12 to 72 hours; a further preferred settling time is 24 to 48 hours.

[0014] Furthermore, in the above-mentioned phenol-containing wastewater treatment process, the evaporation temperature in step (1) is 100-300℃, preferably 150-200℃, and the evaporation time is 2-10h; preferably 3-6h; the evaporation treatment is preferably carried out in a multi-effect evaporator.

[0015] Furthermore, in the above-mentioned phenol-containing wastewater treatment process, the COD of the first liquid phase stream in step (1) is 1.2 to 5.0 times that of the phenol-containing wastewater, and the phenol content of the first liquid phase stream is 1.0 to 3.0 times that of the phenol-containing wastewater; more specifically, the COD of the first liquid phase stream is 50,000 to 120,000 mg / L, and the phenol content is 3,000 to 8,000 mg / L.

[0016] Furthermore, in the above-mentioned phenol-containing wastewater treatment process, the first electrochemical advanced oxidation treatment unit in step (2) includes a first electrode module, wherein the anode and cathode of the first electrode module are composed of multiple sets of parallel circular, triangular, square, hexagonal or other regular or irregular flat plate electrodes.

[0017] Furthermore, in the aforementioned phenol-containing wastewater treatment process, the anode of the first electrode module consists of a substrate and a BDD film disposed on the surface of the substrate. The substrate material can be an inorganic non-metallic material, specifically selected from Si, SiC, AlC, B4C, WC, Cr7C3, BN, TiN, Si3N4, Al2O3, ZrO2, etc.; a further preferred substrate material is one of Si, BN, or Al2O3; the cathode material of the first electrode module is one of graphite, titanium, or stainless steel.

[0018] Furthermore, in the above-mentioned phenol-containing wastewater treatment process, the thickness of the BDD membrane is 10-25 μm, and the mass fraction of boron in the BDD membrane is 5%-8%.

[0019] Furthermore, in the above-mentioned phenol-containing wastewater treatment process, the number of anode plates in the first electrode module is 5 to 15, the number of cathode plates is 6 to 16, and the distance between two adjacent anode plates and cathode plates is 2 to 5 mm; in a further preferred embodiment, the number of anode plates is 8 to 10, the number of cathode plates is 9 to 11, and the distance between two adjacent anode plates and cathode plates is 2.5 to 3.5 mm.

[0020] Furthermore, in the above-mentioned phenol-containing wastewater treatment process, the current density in step (2) is controlled at 50–120 mA / cm². 2 The reaction temperature is controlled between 30 and 60°C. Liquid circulation is achieved via a circulating water pump, with a flow rate set at 50–300 mL / min, and the treatment time is controlled between 5 and 12 hours. In a further preferred embodiment, the current density is controlled between 65 and 80 mA / cm². 2 The reaction temperature was controlled at 40–50℃, the liquid flow rate was set at 80–120 mL / min, and the treatment time was controlled at 7–8 h.

[0021] Furthermore, in the above-mentioned phenol-containing wastewater treatment process, the COD of the second liquid phase stream obtained in step (2) is 0.04 to 0.8 times that of the phenol-containing wastewater, and the phenol content of the second liquid phase stream is 0.025 to 0.6 times that of the phenol-containing wastewater; more specifically, the COD of the second liquid phase stream is 4000 to 8000 mg / L, and the phenol content is 200 to 600 mg / L.

[0022] Furthermore, in the above-mentioned phenol-containing wastewater treatment process, the second electrochemical advanced oxidation treatment unit in step (3) includes a second electrode module, wherein the anode and cathode of the second electrode module are composed of multiple sets of parallel circular, triangular, square, hexagonal or other regular or irregular flat plate electrodes.

[0023] Furthermore, in the aforementioned phenol-containing wastewater treatment process, the anode of the second electrode module consists of a substrate and a BDD film disposed on the surface of the substrate. The substrate material can be a metallic material, specifically selected from titanium, niobium, tantalum, zirconium, tungsten, iron, cobalt, nickel, copper, chromium, etc.; a more preferred substrate material is titanium, niobium, or tungsten. The cathode material of the second electrode module is graphite, metallic titanium, or stainless steel.

[0024] Furthermore, in the above-mentioned phenol-containing wastewater treatment process, the thickness of the BDD membrane is 10-15 μm, and the mass fraction of boron in the BDD membrane is 2%-5%.

[0025] Furthermore, in the above-mentioned phenol-containing wastewater treatment process, the number of anode plates in the second electrode module is 5 to 10, the number of cathode plates is 6 to 11, and the distance between two adjacent anode plates and cathode plates is 1 to 3 mm; in a further preferred embodiment, the number of anode plates is 6 to 8, the number of cathode plates is 7 to 9, and the distance between two adjacent anode plates and cathode plates is 1.5 to 2 mm.

[0026] Furthermore, in the above-mentioned phenol-containing wastewater treatment process, the first gaseous stream obtained in step (1) can be cooled and then enter the second electrochemical advanced oxidation treatment unit to be electrolyzed together with the second liquid stream obtained in step (2), and the third liquid stream is obtained after treatment.

[0027] Furthermore, in the above-mentioned phenol-containing wastewater treatment process, the current density in step (3) is controlled at 20–60 mA / cm². -2 The reaction temperature is controlled at 25–45℃, the liquid flow rate is set at 50–200 mL / min, and the treatment time is controlled at 2–8 h; in a further preferred embodiment, the current density is controlled at 30–45 mA / cm². -2 The reaction temperature was controlled at 30–40℃, the liquid flow rate was set at 60–100 mL / min, and the treatment time was controlled at 3–5 h.

[0028] Furthermore, in the above-mentioned phenol-containing wastewater treatment process, the solid-liquid separation in step (4) is carried out in a sedimentation device, and the sedimentation time is generally controlled to be 8 to 24 hours, with a more preferred sedimentation time of 10 to 15 hours.

[0029] Furthermore, in the above-mentioned phenol-containing wastewater treatment process, the COD of the clear liquid obtained in step (4) is less than 200 mg / L and the phenol content is less than 0.5 mg / L, which meets the emission standards.

[0030] A second aspect of the present invention provides a phenol-containing wastewater treatment system, the treatment system comprising:

[0031] An evaporation and concentration unit is used to treat phenol-containing wastewater by evaporation, resulting in a first gas phase stream and a first liquid phase stream.

[0032] The first electrochemical advanced oxidation treatment unit is used to receive and electrolyze the first liquid phase stream obtained from the evaporation and concentration unit to obtain the second liquid phase stream.

[0033] The second electrochemical advanced oxidation treatment unit is used to receive and electrolyze the second liquid phase stream obtained from the first electrochemical advanced oxidation treatment unit to obtain the third liquid phase stream.

[0034] The solid-liquid separation unit is used to receive the third liquid phase stream obtained after treatment by the second electrochemical advanced oxidation treatment unit, and the clear liquid obtained after solid-liquid separation is discharged in compliance with standards.

[0035] Furthermore, in the above-mentioned phenol-containing wastewater treatment system, when the oil content of the phenol-containing wastewater is greater than or equal to 20 mg / L, the treatment system includes an oil removal unit for removing oil from the phenol-containing wastewater. The oil removal unit can employ any one of the following methods: gravity sedimentation oil removal, air flotation oil removal, ceramic membrane oil removal, oleophobic membrane oil removal, activated carbon adsorption, etc. Gravity sedimentation oil removal is preferred. The phenol-containing wastewater is sent to a gravity oil removal tank and allowed to settle to obtain oil-removed wastewater. The specific settling time is 12–72 h; a more preferred settling time is 24–48 h.

[0036] Furthermore, in the above-mentioned phenol-containing wastewater treatment system, the evaporation and concentration unit adopts a multi-effect evaporator, specifically one of forced circulation, natural circulation, slurry film, rising film, or plate evaporator.

[0037] Furthermore, in the aforementioned phenol-containing wastewater treatment system, the first electrochemical advanced oxidation treatment unit includes a first electrode module, wherein the anode and cathode of the first electrode module are composed of multiple sets of parallel circular, triangular, square, hexagonal or other regular or irregular flat plate electrodes.

[0038] Furthermore, in the aforementioned phenol-containing wastewater treatment system, the anode of the first electrode module consists of a substrate and a BDD film disposed on the surface of the substrate. The substrate material can be an inorganic non-metallic material, specifically selected from Si, SiC, AlC, B4C, WC, Cr7C3, BN, TiN, Si3N4, Al2O3, ZrO2, etc.; more preferably, the substrate material is one of Si, BN, or Al2O3. The cathode material of the first electrode module is one of graphite, titanium, or stainless steel. Even further, the thickness of the BDD film is 10–25 μm, and the mass fraction of boron in the BDD film is 5%–8%.

[0039] Furthermore, in the above-mentioned phenol-containing wastewater treatment system, the number of anode plates in the first electrode module is 5 to 15, the number of cathode plates is 6 to 16, and the distance between two adjacent anode plates and cathode plates is 2 to 5 mm; in a further preferred embodiment, the number of anode plates is 8 to 10, the number of cathode plates is 9 to 11, and the distance between two adjacent anode plates and cathode plates is 2.5 to 3.5 mm.

[0040] Furthermore, in the aforementioned phenol-containing wastewater treatment system, the second electrochemical advanced oxidation treatment unit includes a second electrode module, wherein the anode and cathode of the second electrode module are composed of multiple sets of parallel circular, triangular, square, hexagonal or other regular or irregular flat plate electrodes.

[0041] Furthermore, in the aforementioned phenol-containing wastewater treatment system, the anode of the second electrode module consists of a substrate and a BDD film disposed on the surface of the substrate. The substrate material is a metallic material, specifically one selected from titanium, niobium, tantalum, zirconium, tungsten, iron, cobalt, nickel, copper, and chromium; more preferably, the substrate material is one selected from titanium, niobium, and tungsten. The cathode material of the second electrode module is one selected from graphite, metallic titanium, or stainless steel. Even further, the thickness of the BDD film is 10–15 μm, and the mass fraction of boron in the BDD film is 2%–5%.

[0042] Furthermore, in the above-mentioned phenol-containing wastewater treatment system, the number of anode plates in the second electrode module is 5 to 10, the number of cathode plates is 6 to 11, and the distance between two adjacent anode plates and cathode plates is 1 to 3 mm; in a further preferred embodiment, the number of anode plates is 6 to 8, the number of cathode plates is 7 to 9, and the distance between two adjacent anode plates and cathode plates is 1.5 to 2 mm.

[0043] Furthermore, in the above-mentioned phenol-containing wastewater treatment system, the first gaseous stream obtained after treatment by the evaporation and concentration unit is cooled and then connected to the second electrochemical advanced oxidation treatment unit via pipeline. The cooled first gaseous stream and the second liquid stream are electrolyzed together to obtain the third liquid stream.

[0044] Furthermore, in the aforementioned phenol-containing wastewater treatment system, the solid-liquid separation unit can be any of the existing technologies capable of achieving solid-liquid two-phase separation, such as specifically, it can be carried out in a sedimentation device.

[0045] Compared with the prior art, the phenol-containing wastewater treatment process and system provided by the present invention have one or more of the following beneficial effects:

[0046] (1) The phenol-containing wastewater treatment process provided by this invention combines evaporation concentration and a two-stage electrochemical advanced oxidation treatment unit, which greatly simplifies the current treatment process for high-concentration phenol-containing wastewater. By setting up evaporation concentration at the front end of the first-stage electrochemical advanced oxidation treatment unit, the wastewater treatment volume can be reduced, fully utilizing the advantages of the electrochemical advanced oxidation unit in treating high-concentration COD wastewater and improving the wastewater treatment efficiency per unit time. This invention's treatment process is simple, efficient, and has a wide treatment range. The electrolysis treatment unit does not require the addition of other reagents or pH adjustment; only the action of the two-stage BDD electrodes and the control of process parameters are needed to achieve a significant reduction in COD and phenol content, enabling the wastewater to meet discharge standards.

[0047] (2) In the phenol-containing wastewater treatment process provided by this invention, both stages of electrochemical advanced oxidation treatment units use BDD thin-film electrodes as anodes, which have a much wider electrochemical window (~3.4V vs. SHE) and an extremely high oxygen evolution potential (2.2~2.6V vs. SHE) than other conventional electrodes. The strong oxidizing substances (·OH, SO42-) generated by electrolysis are effectively absorbed. ·- It can oxidize almost all organic pollutants, with high current efficiency and low competition for reaction. Furthermore, it requires no additional oxidant, thus avoiding secondary pollution.

[0048] (3) In the phenol-containing wastewater treatment process provided by the present invention, by adjusting the BDD electrode substrate material and corresponding process parameters in the two-stage electrochemical advanced oxidation treatment unit to adapt it to the wastewater system, the wastewater treatment efficiency can be greatly improved and energy consumption reduced. Among them, the BDD electrode made of inorganic non-metallic substrate materials such as silicon exhibits excellent electrocatalytic activity, and at the same time, it has high bonding strength with the BDD membrane and good electrochemical stability. It is suitable for high-concentration phenol-containing wastewater after evaporation and concentration, so that it can withstand long-term, high-current-density electrolytic treatment. On the other hand, the metal-based BDD electrode has good conductivity and low contact resistance with the wire. Combined with a low current density, it is suitable for treating lower-concentration phenol-containing wastewater, so that it can meet the discharge standards.

[0049] (4) The phenol-containing wastewater treatment process provided by this invention has strong controllability. The electrolysis reaction is carried out at normal temperature and pressure, and the only parameters that need to be controlled are current and voltage, which are easy to observe and regulate. At the same time, this invention also optimizes the electrolysis process. By adjusting the current density, liquid flow rate, treatment time, etc., the electrodes are made suitable for different concentrations, especially ultra-high concentrations of recalcitrant phenol-containing wastewater, thereby improving the treatment efficiency of high-concentration phenol-containing wastewater.

[0050] (5) This invention is simple to operate and low in cost. The electrodes have good stability, long lifespan, and are easy to clean and maintain. Through reasonable system structure design and integration with renewable energy, it has good application prospects. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the phenol-containing wastewater treatment process of the present invention. Detailed Implementation

[0052] To better illustrate the present invention and facilitate understanding of its technical solutions, the present invention will be further described in detail below through embodiments. Obviously, the embodiments described herein are merely some embodiments of the present invention, and the scope of protection of the present invention is not limited thereto.

[0053] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprising" shall be understood to include the stated elements or components without excluding other elements or other components.

[0054] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0055] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0056] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0057] In the context of this invention, all numerical values ​​of parameters (e.g., quantity or condition) should be understood to be modified by the term “about” in all cases, regardless of whether “about” actually appears before the numerical value.

[0058] In the context of this invention, "substantially" means that deviations that are acceptable or reasonable to those skilled in the art are permitted, such as deviations within ±5%, ±2%, ±1%, ±0.5%, or ±0.1%.

[0059] Unless otherwise specified, all percentages, parts, ratios, etc., mentioned in this instruction manual are based on weight, and pressures are gauge pressures. Room temperature mentioned in this instruction manual refers to 25°C.

[0060] In the context of this invention, any two or more embodiments or aspects of this invention can be arbitrarily combined, and the resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of this invention.

[0061] In the context of this specification, the chemical oxygen demand (COD) of phenol-containing wastewater is determined using the potassium dichromate method (GB11914-1989). An excess of potassium dichromate standard solution is accurately added to the water sample to be tested, and the mixture is heated under reflux until the reaction is complete. Unreacted potassium dichromate is titrated back with ferrous ammonium sulfate standard solution, and the COD value is calculated based on the amount of potassium dichromate standard solution consumed. The calculation formula is as follows:

[0062]

[0063] Where C is the concentration of ferrous ammonium sulfate standard solution (mol / L); V0 is the volume of ferrous ammonium sulfate standard solution consumed by the blank sample (mL); V1 is the volume of ferrous ammonium sulfate standard solution consumed by the water sample to be tested (mL); and V is the volume of the water sample to be tested (mL).

[0064] In the context of this specification, the phenol content in phenol-containing wastewater was determined using the 4-aminoantipyrine spectrophotometric method (HJ503-2009). In a medium of pH 10 and in the presence of potassium ferricyanide, phenol reacts with 4-aminoantipyrine to produce a colorimetric reaction. The absorbance at a wavelength of 510 nm was measured using a spectrophotometer, and the corresponding phenol content was obtained from a standard curve plotted using phenol standard solutions.

[0065] In the context of this specification, the oil content of phenol-containing wastewater was determined by infrared spectrophotometry (HJ 637-2018). The water sample was extracted with tetrachloroethylene at pH ≤ 2, and wavenumbers were measured at 2930, 2960, and 3030 cm⁻¹. -1 The absorbance was measured, and the oil content was obtained based on the correction factor.

[0066] In the context of this specification, the conductivity of phenol-containing wastewater was measured using an HK-307 benchtop conductivity meter, with specific methods referring to GB / T 6908-2008.

[0067] like Figure 1 As shown, the specific process of the phenol-containing wastewater treatment process of the present invention is as follows: High-concentration phenol-containing wastewater can be optionally sent to the deoiling unit for oil recovery treatment as needed. After deoiling treatment, the phenol-containing wastewater enters the evaporation and concentration unit for evaporation treatment, and steam (first gas phase stream) and residual liquid (first liquid phase stream) are obtained after treatment. The steam can also enter the second electrochemical advanced oxidation treatment unit for electrolysis treatment after cooling. The obtained residual liquid enters the first electrochemical advanced oxidation treatment unit for electrolysis treatment, and product I (second liquid phase stream) is obtained after treatment. Product I enters the second electrochemical advanced oxidation treatment unit for electrolysis treatment, and product II (third liquid phase stream) is obtained after treatment. Product II enters the solid-liquid separation unit. After solid-liquid separation, the obtained supernatant meets the discharge standards, and the solid waste is collected and treated separately.

[0068] Example 1

[0069] The properties of the phenol-containing wastewater to be treated are as follows: COD is 35400 mg / L, phenol content is 2170 mg / L, conductivity is 4350 μS / cm, and oil content is 124 mg / L.

[0070] The specific processing procedure is as follows:

[0071] (1) The high-concentration phenol-containing wastewater is first subjected to gravity sedimentation to remove oil. After standing for 12 hours, the oil-removed wastewater is transported to the evaporation and concentration unit for evaporation treatment. After treatment, the first liquid phase material flow and the first gas phase material flow are obtained. The evaporation and concentration unit adopts a natural circulation multi-effect evaporator, and the evaporation temperature is set at 200℃ and the evaporation time is 10 hours.

[0072] (2) The first liquid phase stream obtained in step (1) is fed into the first electrochemical advanced oxidation treatment unit for electrolytic treatment, and a second liquid phase stream is obtained after treatment. The anode substrate material of the first electrode module is Si, the BDD film thickness is 10 μm, and the boron mass fraction of the BDD film is 5%. The cathode material of the first electrode module is stainless steel. The first electrode module has 7 anode plates and 8 cathode plates, with a distance of 3 mm between adjacent plates; the current density is set to 70 mA / cm². 2 The reaction temperature was 45℃, the liquid flow rate was 100mL / min, and the treatment time was 7h.

[0073] (3) The second liquid phase stream obtained in step (2) and the cooled first gas phase stream obtained in step (1) are fed into the second electrochemical advanced oxidation treatment unit for electrolytic treatment to obtain the third liquid phase stream. The anode substrate material of the second electrode module is titanium, the BDD film thickness is 12 μm, and the boron mass fraction of the BDD film is 4%. The cathode material of the second electrode module is metallic titanium. The second electrode module has 6 anode plates and 7 cathode plates, with a distance of 1.5 mm between adjacent plates. The current density is set to 20 mA / cm². 2 The reaction temperature was 30℃, the liquid flow rate was 70mL / min, and the treatment time was 4h.

[0074] (4) The third liquid phase stream obtained in step (3) is subjected to solid-liquid separation. The COD of the supernatant is 174 mg / L and the phenol content is 0.4 mg / L, which meets the emission standards.

[0075] Example 2

[0076] The properties of the phenol-containing wastewater to be treated are as follows: COD is 86800 mg / L, phenol content is 7230 mg / L, conductivity is 5865 μS / cm, and oil content is 640 mg / L.

[0077] The specific processing procedure is as follows:

[0078] (1) High-concentration phenol-containing wastewater is first subjected to gravity sedimentation for oil removal. After standing for 72 hours, the oil-removed wastewater is transported to the evaporation and concentration unit for evaporation treatment. After treatment, the first liquid phase flow and the first gas phase flow are obtained. The evaporation and concentration unit adopts a plate multi-effect evaporator. The evaporation temperature is set at 100℃ and the evaporation time is 5 hours.

[0079] (2) The first liquid phase stream obtained in step (1) is fed into the first electrochemical advanced oxidation treatment unit for electrolytic treatment, and a second liquid phase stream is obtained after treatment. The anode substrate material of the first electrode module is SiC, the BDD film thickness is 25 μm, and the boron mass fraction of the BDD film is 8%. The cathode material of the first electrode module is titanium. The first electrode module has 15 anode plates and 16 cathode plates, with a distance of 2 mm between adjacent plates; the current density is set to 80 mA / cm². 2 The reaction temperature was 30℃, the liquid flow rate was 300mL / min, and the treatment time was 12h.

[0080] (3) The second liquid phase stream obtained in step (2) and the cooled first gas phase stream obtained in step (1) are fed into the second electrochemical advanced oxidation treatment unit for electrolytic treatment to obtain the third liquid phase stream. The anode substrate material of the second electrode module is niobium, the BDD film thickness is 15 μm, and the boron mass fraction of the BDD film is 2%. The cathode material of the second electrode module is stainless steel. The second electrode module has 10 anode plates and 11 cathode plates, with a distance of 1 mm between adjacent plates. The current density is set to 30 mA / cm². 2 The reaction temperature was 40℃, the liquid flow rate was 200mL / min, and the treatment time was 8h.

[0081] (4) The third liquid phase stream obtained in step (3) is subjected to solid-liquid separation. The COD of the supernatant is 152 mg / L and the phenol content is 0.3 mg / L, which meets the emission standards.

[0082] Example 3

[0083] The properties of the phenol-containing wastewater to be treated are as follows: COD is 53160 mg / L, phenol content is 3800 mg / L, conductivity is 3570 μS / cm, and oil content is 13 mg / L.

[0084] The specific processing procedure is as follows:

[0085] (1) High-concentration phenol-containing wastewater is directly fed into the evaporation and concentration unit for evaporation treatment, and after treatment, a first liquid phase stream and a first gas phase stream are obtained; the first gas phase stream is cooled and reused industrially; the evaporation and concentration unit adopts a plate-type multi-effect evaporator. The evaporation temperature is set at 150℃ and the evaporation time is 8h.

[0086] (2) The first liquid phase stream obtained in step (1) is fed into the first electrochemical advanced oxidation treatment unit for electrolytic treatment, and a second liquid phase stream is obtained after treatment. The anode substrate material of the first electrode module is Al2O3, the BDD film thickness is 15μm, and the boron mass fraction of the BDD film is 6%. The cathode material of the first electrode module is titanium. The first electrode module has 5 anode plates and 6 cathode plates, with a distance of 3mm between adjacent plates; the current density is set to 120mA / cm². 2 The reaction temperature was 50℃, the liquid flow rate was 120mL / min, and the treatment time was 5h. The COD of the first liquid phase stream was 5500-5700mg / L, and the phenol content was 480-500mg / L.

[0087] (3) The second liquid phase stream obtained in step (2) is fed into the second electrochemical advanced oxidation treatment unit for electrolytic treatment, and a third liquid phase stream is obtained after treatment. The anode substrate material of the second electrode module is niobium, the BDD film thickness is 13 μm, and the boron mass fraction of the BDD film is 5%. The cathode material of the second electrode module is titanium. The second electrode module has 7 anode plates and 8 cathode plates, with a distance of 3 mm between adjacent plates; the current density is set to 60 mA / cm². 2 The reaction temperature was 60℃, the liquid flow rate was 50mL / min, and the treatment time was 2h.

[0088] (4) The third liquid phase stream obtained in step (3) is subjected to solid-liquid separation. The COD of the supernatant is 148 mg / L and the phenol content is 0.4 mg / L, which meets the emission standards.

[0089] Example 4

[0090] The properties of the phenol-containing wastewater to be treated are as follows: COD is 61750 mg / L, phenol content is 2880 mg / L, conductivity is 4430 μS / cm, and oil content is 10 mg / L.

[0091] The specific processing procedure is as follows:

[0092] (1) High-concentration phenol-containing wastewater is directly fed into the evaporation and concentration unit for evaporation treatment, and after treatment, a first liquid phase stream and a first gas phase stream are obtained; the evaporation and concentration unit adopts a forced circulation multi-effect evaporator. The evaporation temperature is set at 300℃ and the evaporation time is 2h.

[0093] (2) The first liquid phase stream obtained in step (1) is fed into the first electrochemical advanced oxidation treatment unit for electrolytic treatment, and a second liquid phase stream is obtained after treatment. The anode substrate material of the first electrode module is BN, the BDD film thickness is 20 μm, and the boron mass fraction of the BDD film is 7%. The cathode material of the first electrode module is graphite. The first electrode module has 10 anode plates and 11 cathode plates, with a distance of 5 mm between adjacent plates; the current density is set to 50 mA / cm². 2 The reaction temperature was 60℃, the liquid flow rate was 50mL / min, and the treatment time was 8h.

[0094] (3) The second liquid phase stream obtained in step (2) and the cooled first gas phase stream obtained in step (1) are fed into the second electrochemical advanced oxidation treatment unit for electrolytic treatment to obtain the third liquid phase stream. The anode substrate material of the second electrode module is tungsten, the BDD film thickness is 10 μm, and the boron mass fraction of the BDD film is 3%. The cathode material of the second electrode module is graphite. The second electrode module has 5 anode plates and 6 cathode plates, with a distance of 2 mm between adjacent plates. The current density is set to 50 mA / cm². 2 The reaction temperature was 25℃, the liquid flow rate was 80mL / min, and the treatment time was 6h.

[0095] (4) The third liquid phase stream obtained in step (3) is subjected to solid-liquid separation. The COD of the supernatant is 166 mg / L and the phenol content is 0.4 mg / L, which meets the emission standards.

[0096] Comparative Example 1

[0097] Compared to Example 1, the difference is that only the first electrode module is provided for the treatment of high-concentration phenol-containing wastewater, and the parameters are the same as in Example 1. The treated wastewater has a COD of 7825 mg / L and a phenol content of 437 mg / L.

[0098] Comparative Example 2

[0099] Compared to Example 1, the difference is that only the second electrode module is provided for the treatment of high-concentration phenol-containing wastewater, and the parameters are the same as in Example 1. The treated wastewater has a COD of 14700 mg / L and a phenol content of 1075 mg / L.

[0100] Comparative Example 3

[0101] Compared to Example 1, the difference lies in that the substrate material of the first and second electrode modules is the same, both using silicon. The treated wastewater had a COD of 1870 mg / L and a phenol content of 120 mg / L.

[0102] Comparative Example 4

[0103] Compared to Example 1, the difference lies in that the base material of the first and second electrode modules is the same, both using titanium. The treated wastewater had a COD of 920 mg / L and a phenol content of 68 mg / L.

[0104] Comparative Example 5

[0105] Compared to Example 1, the difference lies in the absence of evaporation and concentration treatment. The treated wastewater had a COD of 1440 mg / L and a phenol content of 90 mg / L.

Claims

1. A process for treating phenol-containing wastewater, comprising the following steps: (1) The phenol-containing wastewater is evaporated to obtain the first gas phase stream and the first liquid phase stream; (2) The first liquid phase stream obtained in step (1) enters the first electrochemical advanced oxidation treatment unit for electrolysis treatment, and the second liquid phase stream is obtained after treatment; (3) The second liquid phase stream obtained in step (2) enters the second electrochemical advanced oxidation treatment unit for electrolysis treatment, and the third liquid phase stream is obtained after treatment; (4) The third liquid phase material obtained in step (3) is separated into solid and liquid phases, and the resulting clear liquid is discharged in compliance with standards.

2. The phenol-containing wastewater treatment process according to claim 1, wherein, The COD of the phenol-containing wastewater in step (1) is 10,000 to 100,000 mg / L, preferably 30,000 to 60,000 mg / L; the phenol content is 1,000 to 8,000 mg / L, preferably 2,000 to 5,000 mg / L; and the conductivity is not less than 3,000 μS / cm.

3. The phenol-containing wastewater treatment process according to claim 1, wherein, In step (1), the phenol-containing wastewater may be selectively treated for oil removal. When the oil content in the phenol-containing wastewater is greater than or equal to 20 mg / L, oil removal treatment shall be performed first. The oil removal treatment shall be performed by any one of gravity sedimentation oil removal, air flotation oil removal, ceramic membrane oil removal, oleophobic membrane oil removal, or activated carbon adsorption. Gravity sedimentation oil removal is preferred.

4. The phenol-containing wastewater treatment process according to claim 1, wherein, The evaporation temperature in step (1) is 100-300℃, preferably 150-200℃.

5. The phenol-containing wastewater treatment process according to claim 1, wherein, In step (2), the first electrochemical advanced oxidation treatment unit includes a first electrode module, wherein the anode and cathode of the first electrode module are composed of multiple sets of parallel circular, triangular, square, hexagonal or other regular or irregular plate electrodes.

6. The phenol-containing wastewater treatment process according to claim 5, wherein, The anode of the first electrode module consists of a substrate and a BDD film disposed on the surface of the substrate; wherein, the substrate material is an inorganic non-metallic material selected from one of Si, SiC, AlC, B4C, WC, Cr7C3, BN, TiN, Si3N4, Al2O3, and ZrO2; the preferred substrate material is one of Si, BN, and Al2O3; the cathode material of the first electrode module is one of graphite, titanium, and stainless steel.

7. The phenol-containing wastewater treatment process according to claim 6, wherein, The thickness of the BDD film is 10–25 μm, and the mass fraction of boron in the BDD film is 5%–8%.

8. The phenol-containing wastewater treatment process according to claim 5, wherein, In the first electrode module, the number of anode plates is 5 to 15, the number of cathode plates is 6 to 16, and the distance between two adjacent anode plates and cathode plates is 2 to 5 mm; preferably, the number of anode plates is 8 to 10, the number of cathode plates is 9 to 11, and the distance between two adjacent anode plates and cathode plates is 2.5 to 3.5 mm.

9. The phenol-containing wastewater treatment process according to claim 1, wherein, The current density in step (2) is 50–120 mA / cm². 2 The reaction temperature is controlled between 30 and 60°C. The preferred current density is 65–80 mA / cm². 2 The reaction temperature is controlled at 40-50℃.

10. The phenol-containing wastewater treatment process according to claim 1, wherein, In step (3), the second electrochemical advanced oxidation treatment unit includes a second electrode module, wherein the anode and cathode of the second electrode module are composed of multiple sets of parallel circular, triangular, square, hexagonal or other regular or irregular plate electrodes.

11. The phenol-containing wastewater treatment process according to claim 10, wherein, The anode of the second electrode module consists of a substrate and a BDD film disposed on the surface of the substrate; wherein, the substrate material is a metallic material selected from one of titanium, niobium, tantalum, zirconium, tungsten, iron, cobalt, nickel, copper, and chromium; the preferred substrate material is one of titanium, niobium, and tungsten; the cathode material of the second electrode module is one of graphite, metallic titanium, or stainless steel.

12. The phenol-containing wastewater treatment process according to claim 11, wherein, The thickness of the BDD film is 10-15 μm, and the mass fraction of boron in the BDD film is preferably 2%-5%.

13. The phenol-containing wastewater treatment process according to claim 10, wherein, In the second electrode module, the number of anode plates is 5 to 10, the number of cathode plates is 6 to 11, and the distance between two adjacent anode plates and cathode plates is 1 to 3 mm; in a further preferred embodiment, the number of anode plates is 6 to 8, the number of cathode plates is 7 to 9, and the distance between two adjacent anode plates and cathode plates is 1.5 to 2 mm.

14. The phenol-containing wastewater treatment process according to claim 1, wherein, After cooling, the first gaseous stream obtained in step (1) enters the second electrochemical advanced oxidation treatment unit and is electrolyzed together with the second liquid stream obtained in step (2).

15. The phenol-containing wastewater treatment process according to claim 1, wherein, The current density in step (3) is 20–60 mA / cm². -2 The preferred current density is 30–45 mA / cm². -2 The reaction temperature is 25–45℃, preferably 30–40℃.

16. A phenol-containing wastewater treatment system, the treatment system comprising: An evaporation and concentration unit is used to treat phenol-containing wastewater by evaporation, resulting in a first gas phase stream and a first liquid phase stream. The first electrochemical advanced oxidation treatment unit is used to receive and electrolyze the first liquid phase stream obtained from the evaporation and concentration unit to obtain the second liquid phase stream. The second electrochemical advanced oxidation treatment unit is used to receive and electrolyze the second liquid phase stream obtained from the first electrochemical advanced oxidation treatment unit to obtain the third liquid phase stream. The solid-liquid separation unit is used to receive the third liquid phase stream obtained after treatment by the second electrochemical advanced oxidation treatment unit, and the clear liquid obtained after solid-liquid separation is discharged in compliance with standards.

17. The phenol-containing wastewater treatment system according to claim 16, wherein, The treatment system includes an oil removal unit for treating phenol-containing wastewater. The oil removal unit employs any one of the following methods: gravity sedimentation oil removal, air flotation oil removal, ceramic membrane oil removal, oleophobic membrane oil removal, and activated carbon adsorption, with gravity sedimentation oil removal being the preferred method.

18. The phenol-containing wastewater treatment system according to claim 16, wherein, The evaporation and concentration unit uses a multi-effect evaporator, employing one of the following: forced circulation, natural circulation, slurry film, rising film, or plate evaporator.

19. The phenol-containing wastewater treatment system according to claim 16, wherein, The first electrochemical advanced oxidation treatment unit includes a first electrode module, wherein the anode and cathode of the first electrode module are composed of multiple sets of parallel circular, triangular, square, hexagonal or other regular or irregular plate electrodes.

20. The phenol-containing wastewater treatment system according to claim 19, wherein, The anode of the first electrode module consists of a substrate and a BDD film disposed on the surface of the substrate; wherein, the substrate material is an inorganic non-metallic material selected from Si, SiC, AlC, B4C, WC, Cr7C3, BN, TiN, Si3N4, Al2O3, and ZrO2; a further preferred substrate material is one of Si, BN, and Al2O3; the cathode material of the first electrode module is one of graphite, titanium, or stainless steel; the thickness of the BDD film is 10-25 μm, and the mass fraction of boron in the BDD film is 5%-8%.

21. The phenol-containing wastewater treatment system according to claim 19, wherein, In the first electrode module, the number of anode plates is 5 to 15, the number of cathode plates is 6 to 16, and the distance between two adjacent anode plates and cathode plates is 2 to 5 mm; in a further preferred embodiment, the number of anode plates is 8 to 10, the number of cathode plates is 9 to 11, and the distance between two adjacent anode plates and cathode plates is 2.5 to 3.5 mm.

22. The phenol-containing wastewater treatment system according to claim 16, wherein, The first gaseous stream obtained after processing by the evaporation and concentration unit is cooled and then connected to the second electrochemical advanced oxidation treatment unit via pipeline.

23. The phenol-containing wastewater treatment system according to claim 16, wherein, The second electrochemical advanced oxidation treatment unit includes a second electrode module, wherein the anode and cathode of the second electrode module are composed of multiple sets of parallel circular, triangular, square, hexagonal or other regular or irregular plate electrodes.

24. The phenol-containing wastewater treatment system according to claim 23, wherein, The anode of the second electrode module consists of a substrate and a BDD film disposed on the surface of the substrate; wherein, the substrate material is a metallic material selected from titanium, niobium, tantalum, zirconium, tungsten, iron, cobalt, nickel, copper, and chromium; a further preferred substrate material is titanium, niobium, or tungsten; the cathode material of the second electrode module is graphite, metallic titanium, or stainless steel; the thickness of the BDD film is 10–15 μm, and the mass fraction of boron in the BDD film is 2%–5%.

25. The phenol-containing wastewater treatment system according to claim 23, wherein, In the second electrode module, the number of anode plates is 5 to 10, the number of cathode plates is 6 to 11, and the distance between two adjacent anode plates and cathode plates is 1 to 3 mm; in a further preferred embodiment, the number of anode plates is 6 to 8, the number of cathode plates is 7 to 9, and the distance between two adjacent anode plates and cathode plates is 1.5 to 2 mm.

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