Method and system for deeply treating petrochemical wastewater based on graded adsorption coupling membrane process

Abstract

The invention relates to the technical field of industrial wastewater treatment, in particular to a method and a system for deeply treating petrochemical wastewater based on a graded adsorption coupling membrane process. The method comprises the following steps: filtering the petrochemical wastewater to obtain pretreated petrochemical wastewater; the pretreated petrochemical wastewater is subjected to first-stage adsorption treatment, first-stage adsorption effluent is obtained, and an adsorbent used in the first-stage adsorption treatment is activated carbon; the first-stage adsorption effluent is subjected to second-stage adsorption treatment, second-stage adsorption effluent is obtained, and an adsorbent used in the second-stage adsorption treatment is silica gel; and enabling the secondary adsorption effluent to pass through a nanofiltration membrane, and carrying out membrane separation to obtain effluent. According to the method, pollutants in the petrochemical wastewater can be deeply removed, the separation of main pollutants in the petrochemical wastewater is realized, and the effluent quality is stable. The method is simple and convenient, the treatment process can be regulated and controlled, and the TOC content of effluent obtained after treatment is 1t; and 20 ppm.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial wastewater treatment, and in particular to a method and system for deep treatment of petrochemical wastewater based on a graded adsorption coupled membrane process. Background Art

[0002] Petrochemical wastewater refers to wastewater generated in industrial production processes such as petrochemicals, oil refining, and coal chemical industry, which contains a large amount of particulate matter, hydrophilic / hydrophobic organic matter, heavy metals, salts and other pollutants. The high content of toxic pollutants and surfactants in petrochemical wastewater leads to low efficiency of conventional treatment and difficulty in meeting emission requirements. At present, flotation oil removal and coagulation sedimentation have been widely used in the early treatment of petrochemical wastewater, but the above processes can only remove some large-sized pollutants that are difficult to dissolve in water, such as emulsified oil, surface floating oil and volatile organic matter, and the removal rate of dissolved pollutants is still low. Advanced oxidation technologies such as Fenton, ozone, electrochemistry or catalysis can significantly improve the biodegradability of petrochemical wastewater by oxidizing organic pollutants, but the high cost and toxic sludge disposal problems limit their application. Biological treatments such as anaerobic or acid oxidation can have a strong removal effect on highly toxic pollutants in petrochemical wastewater, but their operating conditions are strict and the overall time is long.

[0003] Adsorption is an efficient technology for rapidly removing pollutants from wastewater, and it has shown strong adaptability in removing dissolved organic matter and particulate matter at the same time. Adsorption materials such as activated carbon or silica gel can effectively enrich and separate hydrophobic or hydrophilic pollutants in wastewater, respectively, and the above materials have the advantages of low cost and easy regulation. There are many types of dissolved organic matter in petrochemical wastewater, which leads to widespread adsorption competition or adsorption promotion between pollutants. Limited by hydrophilicity and pore size, it is difficult for a single adsorbent to effectively remove various types of pollutants in petrochemical wastewater, and the removal of residual pollutants in adsorbed water remains a technical challenge. Nanofiltration membrane method is a membrane separation method between ultrafiltration and reverse osmosis, which is suitable for removing pollutants with a relative molecular weight of more than 100. Nanofiltration membrane method can effectively separate large-particle hydrophobic organic matter and salt, so it is widely used in the field of petrochemical wastewater treatment. However, nanofiltration membrane method has high requirements for the initial water quality. Turbidity, suspended matter, oil droplets, silicates and other nano-particles in water are very easy to block the membrane pores or form a fouling layer on the membrane surface, affecting the overall operation. Therefore, how to provide an efficient and stable method and system for deep treatment of petrochemical wastewater remains a problem to be solved urgently in this field. Summary of the invention

[0004] The object of the present invention is to provide a method and system for deep treatment of petrochemical wastewater based on a graded adsorption coupled membrane process, so as to efficiently remove pollutants in the petrochemical wastewater.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for deep treatment of petrochemical wastewater based on a graded adsorption coupled membrane process, comprising the following steps:

[0007] 1) filtering the petrochemical wastewater to obtain pretreated petrochemical wastewater;

[0008] 2) subjecting the pretreated petrochemical wastewater to primary adsorption treatment to obtain primary adsorption effluent, wherein the adsorbent used in the primary adsorption treatment is activated carbon;

[0009] 3) subjecting the primary adsorption effluent to secondary adsorption treatment to obtain secondary adsorption effluent, wherein the adsorbent used in the secondary adsorption treatment is silica gel;

[0010] 4) Passing the secondary adsorption effluent through a nanofiltration membrane for membrane separation to obtain effluent.

[0011] Optionally, the filtering material is a glass fiber filter membrane, and the pore size of the glass fiber filter membrane is 0.45 μm.

[0012] Optionally, the temperature of the primary adsorption treatment is 15 to 60° C., and the time is 5 to 30 minutes.

[0013] Optionally, the activated carbon accounts for 0.1-10% of the mass of the pretreated petrochemical wastewater.

[0014] Optionally, the temperature of the secondary adsorption treatment is 15 to 60° C. and the time is 5 to 30 minutes.

[0015] Optionally, the silica gel accounts for 0.1-20% of the mass of the first-stage adsorption water.

[0016] Optionally, the nanofiltration membrane is a polyamide nanofiltration membrane, and the pore size of the nanofiltration membrane is 0.2 to 1 nm; the pressure of the membrane separation is 0.08 to 1.2 MPa.

[0017] Optionally, the method further comprises:

[0018] The activated carbon and silica gel after adsorption saturation are regenerated and used for primary adsorption treatment and secondary adsorption treatment respectively, wherein the regeneration temperature of the activated carbon is 300-600°C, and the regeneration temperature of the silica gel is 80-220°C.

[0019] Optionally, the method further comprises:

[0020] The concentrated water intercepted by membrane separation is used as petrochemical wastewater and steps 1) to 4) are performed again; and

[0021] When the water obtained by membrane separation does not meet the discharge requirements, steps 1) to 4) are repeated.

[0022] The present invention also provides a system for deep treatment of petrochemical wastewater based on graded adsorption coupled membrane process, which is used to implement the above method, including a filtration unit, a primary adsorption unit, a secondary adsorption unit, a nanofiltration unit, a water outlet tank, a water quality detection unit, an activated carbon regeneration unit and a silica gel regeneration unit.

[0023] The filtering unit is used to filter petrochemical wastewater, and its input end is connected to the petrochemical wastewater inlet end;

[0024] The input end of the primary adsorption unit is connected to the output end of the filtration unit, the primary adsorption unit is filled with activated carbon, and the primary adsorption unit is provided with a primary water outlet and a primary adsorbent output end;

[0025] The input end of the secondary adsorption unit is connected to the primary water outlet end of the primary adsorption unit, silica gel is installed in the secondary adsorption unit, and the secondary adsorption unit is provided with a secondary water outlet end and a secondary adsorbent output end;

[0026] The input end of the nanofiltration unit is connected to the secondary water outlet end of the secondary adsorption unit. The nanofiltration unit is equipped with a membrane assembly of a nanofiltration membrane. The nanofiltration unit is provided with a first output end and a second output end. The first output end is connected to the input end of the filtration unit and is used to transport the retained concentrated water to the filtration unit. The second output end is used to output the purified water after nanofiltration.

[0027] The input end of the water outlet tank is connected to the second output end of the nanofiltration unit and is used to store purified water after nanofiltration. The water outlet tank is provided with a circulating water outlet and a drainage end, and the circulating water outlet is connected to the input end of the filtration unit.

[0028] The water quality detection unit is arranged in the water outlet tank and is used to detect the water quality of the purified water;

[0029] The input end of the activated carbon regeneration unit is connected to the primary adsorbent output end of the primary adsorption unit, and the output end of the activated carbon regeneration unit is connected to the input end of the primary adsorption unit;

[0030] The input end of the silica gel regeneration unit is connected to the secondary adsorbent output end of the secondary adsorption unit, and the output end of the silica gel regeneration unit is connected to the input end of the secondary adsorption unit.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention provides a method and system for deep treatment of petrochemical wastewater based on a graded adsorption coupled membrane process. The method deeply treats petrochemical wastewater based on an pore size-controlled adsorption coupled membrane process. The petrochemical wastewater is filtered to remove some solid matter and suspended particles in the wastewater. The first-level adsorption removes hydrophobic organic matter, and the second-level adsorption removes hydrophilic organic matter. By matching different adsorbents and controlling the adsorption selectivity of the adsorbents, the main pollutants and membrane contamination components in the wastewater are removed step by step in a targeted manner as a treatment before nanofiltration membrane separation. Subsequent nanofiltration deeply removes the residual macromolecular pollutants, realizes the separation of the main pollutants in the petrochemical wastewater, and the effluent water quality is stable. In addition, the system for implementing the method is simple to operate, the equipment is easy to maintain, the footprint is small, the treatment process is controllable, and the TOC content in the effluent obtained after treatment is <20ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a process flow chart for deep treatment of petrochemical wastewater in an embodiment of the present invention.

[0034] Figure 2 This is a graph showing the change in TOC content in petrochemical wastewater over treatment time in Example 1.

[0035] Figure 3 This is a graph showing the change in TOC content in petrochemical wastewater during the treatment process of Example 1 of the present invention.

[0036] Figure 4 This is a graph showing the change in TOC content in petrochemical wastewater during the treatment process of Example 2 of the present invention.

[0037] Figure 5 This is a graph showing the change in TOC content in petrochemical wastewater during the treatment process of Example 3 of the present invention.

[0038] Figure 6 This is a graph showing the change in TOC content in petrochemical wastewater during the treatment process of Example 4 of the present invention.

[0039] Figure 7 This is a graph showing changes in TOC content during the five-cycle treatment of petrochemical wastewater in the present invention.

[0040] Figure 8 This is a graph showing the change in TOC content in petrochemical wastewater during the treatment process of Comparative Example 1 of the present invention.

[0041] Fig. 9 This is a graph showing the change in TOC content in petrochemical wastewater during the treatment process of Comparative Example 2 of the present invention.

[0042] Fig.10 This is a graph showing the change in TOC content in petrochemical wastewater during the treatment process of Comparative Example 3 of the present invention.

[0043] Fig.11This is a graph showing the change in TOC content in petrochemical wastewater during the treatment process of Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0044] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0045] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0046] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0047] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0048] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0049] The raw materials used in the present invention can be obtained from the market or prepared by the existing technology.

[0050] The "room temperature" mentioned in the present invention is 25±2°C unless otherwise specified.

[0051] The present invention provides a method for deep treatment of petrochemical wastewater based on a graded adsorption coupled membrane process, comprising the following steps:

[0052] 1) filtering the petrochemical wastewater to obtain pretreated petrochemical wastewater;

[0053] 2) subjecting the pretreated petrochemical wastewater to primary adsorption treatment to obtain primary adsorption effluent, wherein the adsorbent used in the primary adsorption treatment is activated carbon;

[0054] 3) subjecting the primary adsorption effluent to secondary adsorption treatment to obtain secondary adsorption effluent, wherein the adsorbent used in the secondary adsorption treatment is silica gel;

[0055] 4) Passing the secondary adsorption effluent through a nanofiltration membrane for membrane separation to obtain effluent.

[0056] The present invention first filters petrochemical wastewater to obtain pretreated petrochemical wastewater.

[0057] In the embodiment of the present invention, the filtering material is a glass fiber filter membrane with a pore size of 0.45 μm. The present invention filters petrochemical wastewater through the filtering material to remove some solid matter and suspended particles in the wastewater.

[0058] After obtaining the pretreated petrochemical wastewater, the pretreated petrochemical wastewater is subjected to primary adsorption treatment to obtain primary adsorption effluent, wherein the adsorbent used in the primary adsorption treatment is activated carbon.

[0059] In the embodiment of the present invention, the activated carbon is bituminous coal activated carbon from Datong, Shanxi Province, and the pore size distribution range of the activated carbon is 0.5-150 nm, the average pore size is 2.12 nm, and the pore volume of the macropore (>50 nm) is 0.09 cm 3 / g. In the present invention, the activated carbon containing macropores can better adsorb and remove hydrophobic organic matter in petrochemical wastewater.

[0060] In some embodiments of the present invention, the temperature of the primary adsorption treatment is 15-60°C, preferably 20-50°C, and more preferably 30-40°C, and the time is 5-30 min, preferably 10-25 min, and more preferably 15-20 min.

[0061] In the present invention, after the primary adsorption treatment is completed, solid-liquid separation is performed. The present invention does not limit the method of solid-liquid separation. In the embodiment of the present invention, the primary adsorption effluent and activated carbon are separated by filtering.

[0062] In some embodiments of the present invention, the activated carbon accounts for 0.1-10% of the mass of the pretreated petrochemical wastewater, preferably 0.8-8%, and more preferably 1.2-2%.

[0063] After obtaining the primary adsorption effluent, the primary adsorption effluent is subjected to secondary adsorption treatment to obtain secondary adsorption effluent, wherein the adsorbent used for the secondary adsorption treatment is silica gel.

[0064] In the embodiment of the present invention, the silica gel is industrial grade silica gel, the specific CAS model is 112926-00-8, the pore size distribution range of the silica gel is 0.5-50 nm, the average pore size is 2.51 nm, and the mesopore (2-50 nm) pore volume is 0.37 cm 3 / g. In the present invention, silica gel can adsorb and remove hydrophilic organic matter in petrochemical wastewater.

[0065] In some embodiments of the present invention, the temperature of the secondary adsorption treatment is 15-60°C, preferably 20-50°C, and more preferably 30-40°C, and the time is 5-30 min, preferably 10-25 min, and more preferably 15-20 min.

[0066] In the present invention, after the secondary adsorption treatment is completed, solid-liquid separation is performed. The present invention does not limit the method of solid-liquid separation. In the embodiment of the present invention, the secondary adsorption effluent and silica gel are separated by filtering.

[0067] In some embodiments of the present invention, the silica gel accounts for 0.1-20% of the mass of the first-stage adsorption water, preferably 1.2-10%, and more preferably 2-5%.

[0068] In some embodiments of the present invention, the activated carbon and silica gel after adsorption saturation are regenerated and used for primary adsorption treatment and secondary adsorption treatment respectively, wherein the regeneration temperature of the activated carbon is 300-600°C, preferably 400-500°C, and the time is 1 hour; the regeneration temperature of the silica gel is 80-220°C, preferably 100-150°C, further preferably 120-130°C, and the time is 4 hours.

[0069] After obtaining the secondary adsorption effluent, the secondary adsorption effluent is passed through a nanofiltration membrane for membrane separation to obtain effluent.

[0070] The present invention has no special limitation on the type of nanofiltration membrane, as long as it can deeply remove the residual macromolecular pollutants in petrochemical wastewater. In some embodiments of the present invention, the nanofiltration membrane is a polyamide nanofiltration membrane, and the pore size of the nanofiltration membrane is 0.2 to 1 nm, preferably 0.2 to 0.6 nm, and more preferably 0.2 to 0.45 nm.

[0071] In some embodiments of the present invention, the pressure of membrane separation is 0.08 to 1.2 MPa, preferably 0.2 to 1 MPa, and more preferably 0.4 to 0.8 MPa.

[0072] In some embodiments of the present invention, the concentrated water obtained by membrane separation is used as petrochemical wastewater and steps 1) to 4) are performed again; and

[0073] When the water obtained by membrane separation does not meet the discharge requirements, steps 1) to 4) are repeated.

[0074] The present invention also provides a system for deep treatment of petrochemical wastewater based on graded adsorption coupled membrane process, which is used to implement the above method, including a filtration unit, a primary adsorption unit, a secondary adsorption unit, a nanofiltration unit, a water storage tank, a water quality detection unit, an activated carbon regeneration unit and a silica gel regeneration unit.

[0075] The filtering unit is used to filter petrochemical wastewater, and its input end is connected to the petrochemical wastewater inlet end;

[0076] The input end of the primary adsorption unit is connected to the output end of the filtration unit, the primary adsorption unit is filled with activated carbon, and the primary adsorption unit is provided with a primary water outlet and a primary adsorbent output end;

[0077] The input end of the secondary adsorption unit is connected to the primary water outlet end of the primary adsorption unit, silica gel is installed in the secondary adsorption unit, and the secondary adsorption unit is provided with a secondary water outlet end and a secondary adsorbent output end;

[0078] The input end of the nanofiltration unit is connected to the secondary water outlet end of the secondary adsorption unit. The nanofiltration unit is equipped with a membrane assembly of a nanofiltration membrane. The nanofiltration unit is provided with a first output end and a second output end. The first output end is connected to the input end of the filtration unit and is used to transport the retained concentrated water to the filtration unit. The second output end is used to output the purified water after nanofiltration.

[0079] The input end of the water outlet tank is connected to the second output end of the nanofiltration unit and is used to store purified water after nanofiltration. The water outlet tank is provided with a circulating water outlet and a drainage end, and the circulating water outlet is connected to the input end of the filtration unit.

[0080] The water quality detection unit is arranged in the water outlet tank and is used to detect the water quality of the purified water;

[0081] The input end of the activated carbon regeneration unit is connected to the primary adsorbent output end of the primary adsorption unit, and the output end of the activated carbon regeneration unit is connected to the input end of the primary adsorption unit;

[0082] The input end of the silica gel regeneration unit is connected to the secondary adsorbent output end of the secondary adsorption unit, and the output end of the silica gel regeneration unit is connected to the input end of the secondary adsorption unit.

[0083] In an embodiment of the present invention, a water quality detector is used to perform water quality detection. The water quality detection is that the water quality detector detects the TOC of the sewage. If it is qualified, the effluent is discharged. If it is unqualified, the primary adsorption treatment is performed again, and the subsequent treatment method is repeated.

[0084] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0085] The following embodiments all adopt Figure 1 The system shown in the figure performs deep treatment on petrochemical wastewater. Specifically, the system includes a filtration unit, a primary adsorption unit, a secondary adsorption unit, a nanofiltration unit, a water outlet tank, a water quality detection unit, an activated carbon regeneration unit and a silica gel regeneration unit.

[0086] A filtering unit, used for filtering petrochemical wastewater, wherein an input end thereof is connected to a petrochemical wastewater inlet end;

[0087] A primary adsorption unit, wherein the input end of the primary adsorption unit is connected to the output end of the filtration unit, the primary adsorption unit is filled with activated carbon, and the primary adsorption unit is provided with a primary water outlet and a primary adsorbent output end;

[0088] A secondary adsorption unit, wherein the input end of the secondary adsorption unit is connected to the primary water outlet end of the primary adsorption unit, silica gel is installed in the secondary adsorption unit, and the secondary adsorption unit is provided with a secondary water outlet end and a secondary adsorbent output end;

[0089] A nanofiltration unit, wherein the input end of the nanofiltration unit is connected to the secondary water outlet end of the secondary adsorption unit, a membrane assembly of a nanofiltration membrane is installed in the nanofiltration unit, and the nanofiltration unit is provided with a first output end and a second output end, the first output end is connected to the input end of the filtration unit, and is used to transport the retained concentrated water to the filtration unit, and the second output end is used to output the purified water after nanofiltration;

[0090] The input end of the water outlet tank is connected to the second output end of the nanofiltration unit and is used to store the purified water after nanofiltration. The water outlet tank is provided with a circulating water outlet end and a drainage end, and the circulating water outlet end is connected to the input end of the filtration unit;

[0091] The water quality detection unit is arranged in the water outlet tank and is used to detect the water quality of the purified water;

[0092] The input end of the activated carbon regeneration unit is connected to the primary adsorbent output end of the primary adsorption unit, and is used to transport the saturated activated carbon in the primary adsorption unit to the activated carbon regeneration unit. The output end of the activated carbon regeneration unit is connected to the input end of the primary adsorption unit, and is used to transport the regenerated activated carbon to the primary adsorption unit for recycling.

[0093] The input end of the silica gel regeneration unit is connected to the secondary adsorbent output end of the secondary adsorption unit, and is used to transport the saturated silica gel in the secondary adsorption unit to the silica gel regeneration unit. The output end of the silica gel regeneration unit is connected to the input end of the secondary adsorption unit, and is used to transport the regenerated silica gel to the secondary adsorption unit for recycling.

[0094] Example 1

[0095] according to Figure 1 The process shown in the figure deeply treats petrochemical wastewater. At 25°C and pH 7, the TOC content in petrochemical wastewater is 175ppm:

[0096] 1) The petrochemical wastewater is filtered through a glass fiber filter membrane with a pore size of 0.45 μm to obtain pretreated petrochemical wastewater. The TOC content of the pretreated petrochemical wastewater effluent is 150 ppm.

[0097] 2) The pretreated petrochemical wastewater is transported to a container with an average pore size of 2.12 nm and a large pore volume of 0.09 cm 3 / g of bituminous coal activated carbon in the primary adsorption unit, the bituminous coal activated carbon accounts for 1.2% of the mass of the pretreated petrochemical wastewater, and adsorption is carried out at 25°C for 0.5h to complete the primary adsorption treatment, and then the bituminous coal activated carbon after the primary adsorption treatment and the primary adsorption effluent are filtered and separated to obtain the primary adsorption effluent and the adsorption saturated bituminous coal activated carbon.

[0098] 3) The first-stage adsorption effluent is transported to a container with an average pore size of 2.51 nm, a mesopore (2-50 nm) and a pore volume of 0.37 cm 3 / g, CAS model 112926-00-8, in the secondary adsorption unit of silica gel, silica gel accounts for 2% of the mass of the primary adsorption effluent, and adsorption is carried out at 25°C for 0.5h to complete the secondary adsorption treatment, and then the silica gel after the secondary adsorption treatment and the secondary adsorption effluent are filtered and separated to obtain the secondary adsorption effluent and adsorption-saturated silica gel.

[0099] 4) The secondary adsorption effluent is passed through a polyamide nanofiltration membrane with a pore size of 0.45 nm and membrane separation is performed at a pressure of 0.8 MPa. After membrane separation, nanofiltration effluent and concentrated water are obtained. The nanofiltration effluent is transported to a water outlet tank, and the concentrated water is transported to a pretreatment tank;

[0100] The TOC content of the water discharged from the water tank was detected by a water quality detector and was 18ppm, which was in line with the "Petrochemical Industry Pollutant Emission Standard" (GB 31571-2015, including the 2024 amendment), and was discharged from the water outlet by a drainage pump.

[0101] Figure 2 This is a graph showing the change in TOC content in petrochemical wastewater versus treatment time in Example 1. It can be seen that the petrochemical wastewater can reach primary adsorption equilibrium after 10 to 30 minutes, secondary adsorption equilibrium after 30 minutes, and the nanofiltration treatment efficiency remains stable after 4 hours.

[0102] Figure 3The TOC content change diagram of the petrochemical wastewater treatment process in Example 1 shows that the petrochemical wastewater undergoes pretreatment, primary adsorption, secondary adsorption and nanofiltration treatment. The water permeation flux of the polyamide nanofiltration membrane is 13.48 L·m -2 ·h -1 bar -1 The TOC content of petrochemical wastewater is reduced from the initial 175ppm to 18ppm, which can remove pollutants in petrochemical wastewater and achieve deep treatment of petrochemical wastewater.

[0103] Example 2

[0104] At 25°C and pH 3, the TOC content in petrochemical wastewater is 173ppm:

[0105] 1) The petrochemical wastewater is filtered through a glass fiber filter membrane with a pore size of 0.45 μm to obtain pretreated petrochemical wastewater. The TOC content of the pretreated petrochemical wastewater effluent is 141 ppm.

[0106] 2) The pretreated petrochemical wastewater is transported to a container with an average pore size of 2.12 nm and a large pore volume of 0.09 cm 3 / g of bituminous coal activated carbon in the primary adsorption unit, the bituminous coal activated carbon accounts for 1.2% of the mass of the pretreated petrochemical wastewater, and adsorbs at 25°C for 0.5h to complete the primary adsorption treatment, and then the bituminous coal activated carbon after the primary adsorption treatment and the primary adsorption effluent are filtered and separated to obtain the primary adsorption effluent.

[0107] 3) The first-stage adsorption effluent is transported to a container with an average pore size of 2.51 nm, a mesopore (2-50 nm) and a pore volume of 0.37 cm 3 / g, in the secondary adsorption unit of silica gel with CAS model 112926-00-8, silica gel accounts for 2% of the mass of the primary adsorption effluent. After the silica gel is saturated with adsorption, it is adsorbed at 25°C for 0.5h to complete the secondary adsorption treatment. Then, the silica gel treated with the secondary adsorption and the secondary adsorption effluent are filtered and separated to obtain the secondary adsorption effluent and the adsorption-saturated silica gel.

[0108] 4) The secondary adsorption effluent is passed through a polyamide nanofiltration membrane with a pore size of 0.2 nm, and membrane separation is performed at a pressure of 0.8 MPa. After membrane separation, nanofiltration effluent and concentrated water are obtained. The nanofiltration effluent is transported to a water outlet tank, and the concentrated water is transported to a pretreatment tank;

[0109] The TOC content of the water discharged from the water tank was detected by a water quality detector and was 7ppm, which was in line with the "Petrochemical Industry Pollutant Emission Standard" (GB 31571-2015, including the 2024 amendment), and was discharged from the water outlet by a drainage pump.

[0110] Figure 4The TOC content change diagram of the petrochemical wastewater treatment process in Example 2 shows that the petrochemical wastewater undergoes pretreatment, primary adsorption, secondary adsorption and nanofiltration treatment. The water permeation flux of the polyamide nanofiltration membrane is 2.76 L·m -2 ·h -1 bar -1 The TOC content of petrochemical wastewater is reduced from the initial 173ppm to 7ppm, which can remove pollutants in petrochemical wastewater and achieve deep treatment of petrochemical wastewater.

[0111] Example 3

[0112] At 15°C and pH 3, the TOC content in petrochemical wastewater is 178ppm;

[0113] 1) The petrochemical wastewater is filtered through a glass fiber filter membrane with a pore size of 0.45 μm to obtain pretreated petrochemical wastewater. The TOC content of the pretreated petrochemical wastewater effluent is 150 ppm.

[0114] 2) The pretreated petrochemical wastewater is transported to a container with an average pore size of 2.12 nm and a large pore volume of 0.09 cm 3 / g of bituminous coal activated carbon in the primary adsorption unit, the bituminous coal activated carbon accounts for 1.2% of the mass of the pretreated petrochemical wastewater, and adsorbs at 15°C for 0.5h to complete the primary adsorption treatment, and then the activated carbon after the primary adsorption treatment and the primary adsorption effluent are filtered and separated to obtain the primary adsorption effluent.

[0115] 3) The first-stage adsorption effluent is transported to a container with an average pore size of 2.51 nm, a mesopore (2-50 nm) and a pore volume of 0.37 cm 3 / g, CAS model 112926-00-8, in the secondary adsorption unit of silica gel, silica gel accounts for 2% of the mass of the primary adsorption effluent, and adsorption is carried out at 15°C for 0.5h to complete the secondary adsorption treatment, and then the silica gel after the secondary adsorption treatment and the secondary adsorption effluent are filtered and separated to obtain the secondary adsorption effluent.

[0116] 4) The secondary adsorption effluent is passed through a polyamide nanofiltration membrane with a pore size of 0.25 nm, and membrane separation is performed at a pressure of 0.8 MPa. After membrane separation, nanofiltration effluent and concentrated water are obtained. The nanofiltration effluent is transported to a water outlet tank, and the concentrated water is transported to a pretreatment tank;

[0117] The TOC content of the water discharged from the water tank was detected by a water quality detector and was 12ppm, which was in line with the "Petrochemical Industry Pollutant Emission Standard" (GB 31571-2015, including the 2024 amendment), and was discharged from the water outlet by a drainage pump.

[0118] Figure 5The TOC content change diagram of the petrochemical wastewater treatment process in Example 3 shows that the petrochemical wastewater undergoes pretreatment, primary adsorption, secondary adsorption and nanofiltration treatment. The water permeation flux of the polyamide nanofiltration membrane is 3.54 L·m -2 ·h -1 bar -1 The TOC content of petrochemical wastewater is reduced from the initial 178ppm to 12ppm, which can remove pollutants in petrochemical wastewater and achieve deep treatment of petrochemical wastewater.

[0119] Example 4

[0120] At 25°C and pH 7, the TOC content in petrochemical wastewater is 105ppm;

[0121] 1) The petrochemical wastewater is filtered through a glass fiber filter membrane with a pore size of 0.45 μm to obtain pretreated petrochemical wastewater. The TOC content of the pretreated petrochemical wastewater effluent is 101 ppm.

[0122] 2) The pretreated petrochemical wastewater is transported to a container with an average pore size of 2.12 nm and a large pore volume of 0.09 cm 3 In the primary adsorption unit mixed with bituminous coal activated carbon of 200 g / kg, the bituminous coal activated carbon accounts for 0.8% of the mass of the pretreated petrochemical wastewater. The adsorption is carried out at 25°C for 0.5 h to complete the primary adsorption treatment. Then, the bituminous coal activated carbon after the primary adsorption treatment and the primary adsorption effluent are filtered and separated to obtain the primary adsorption effluent.

[0123] 3) The first-stage adsorption effluent is transported to a container with an average pore size of 2.51 nm, a mesopore (2-50 nm) and a pore volume of 0.37 cm 3 / g, CAS model 112926-00-8, in the secondary adsorption unit of silica gel, silica gel accounts for 1.2% of the mass of the primary adsorption effluent, and adsorption is carried out at 25°C for 0.5h to complete the silica secondary adsorption treatment, and then the silica gel after the secondary adsorption treatment and the secondary adsorption effluent are filtered and separated to obtain the secondary adsorption effluent.

[0124] 4) The secondary adsorption effluent is passed through a polyamide nanofiltration membrane with a pore size of 0.22 nm and membrane separation is performed at a pressure of 0.8 MPa. After membrane separation, nanofiltration effluent and concentrated water are obtained. The nanofiltration effluent is transported to a water outlet tank, and the concentrated water is transported to a pretreatment tank.

[0125] The TOC content of the water discharged from the water tank is detected by a water quality detector and is 10ppm, which is in line with the "Petrochemical Industry Pollutant Emission Standard" (GB 31571-2015, including the 2024 amendment), and is discharged from the water outlet by a drainage pump.

[0126] Figure 6The TOC content change diagram of the petrochemical wastewater treatment process in Example 4 shows that the petrochemical wastewater undergoes pretreatment, primary adsorption, secondary adsorption and nanofiltration treatment. The water permeation flux of the polyamide nanofiltration membrane is 3.02 L·m -2 ·h -1 bar -1 The TOC content of petrochemical wastewater is reduced from the initial 105ppm to 10ppm, which can remove pollutants in petrochemical wastewater and achieve deep treatment of petrochemical wastewater.

[0127] Example 5

[0128] The adsorption saturated bituminous coal activated carbon in Example 1 was transported to an activated carbon regeneration unit, and regenerated at 600° C. for 1 hour to obtain regenerated bituminous coal activated carbon, and the regenerated bituminous coal activated carbon was transported to a primary adsorption unit.

[0129] The saturated silica gel in Example 1 was transported to a silica gel regeneration unit, and regenerated at 120° C. for 4 hours to obtain regenerated silica gel, which was then transported to a secondary adsorption unit.

[0130] The used nanofiltration membrane in Example 1 was inverted, and backwashed with effluent water at 25° C. for 1 h to obtain a regenerated nanofiltration membrane, which was then placed in a nanofiltration unit.

[0131] Example 6

[0132] The only difference from Example 1 is that the primary adsorption unit is equipped with the regenerated bituminous coal activated carbon of Example 5; the secondary adsorption unit is equipped with the regenerated silica gel of Example 5; and the nanofiltration unit is equipped with the regenerated nanofiltration membrane of Example 5.

[0133] After the petrochemical wastewater treatment in Example 6 is completed, the adsorption saturated regenerated bituminous coal activated carbon, regenerated silica gel and regenerated nanofiltration membrane are continued to be regenerated. After the regeneration treatment is completed, they are returned to the primary adsorption unit, the secondary adsorption unit and the nanofiltration unit respectively, and the petrochemical wastewater is treated according to the steps of Example 1, and the cycle is continued for 3 times based on Example 6.

[0134] Figure 7 This is a graph showing the change in TOC content during the five-cycle treatment of petrochemical wastewater. It can be seen that after the pretreatment of material regeneration, primary adsorption, secondary adsorption and nanofiltration treatment, the TOC content of the petrochemical wastewater can still be reduced from the initial 175ppm to below 20ppm, which can remove pollutants in the petrochemical wastewater and achieve deep treatment of petrochemical wastewater, in line with the "Petrochemical Industry Pollutant Emission Standard" (GB 31571-2015, including the 2024 amendment).

[0135] The present invention tests the TOC content of the primary adsorption effluent obtained after the bituminous coal activated carbon is saturated with adsorption and the TOC content of the primary adsorption effluent obtained after the regenerated bituminous coal activated carbon is saturated with adsorption. It is calculated through the calculation formula of adsorption capacity that the initial adsorption capacity of the bituminous coal activated carbon is 5.6 mg / g. After 5 cycles of regeneration, its adsorption capacity is still stable at 5.3 mg / g, indicating that the activated carbon in the scheme of the present invention is regenerable and can be recycled.

[0136] The present invention tests the TOC content of the secondary adsorption effluent obtained after the silica gel is saturated with adsorption and the TOC content of the secondary adsorption effluent obtained after the regenerated silica gel is saturated with adsorption. The calculation formula of the adsorption capacity shows that the initial adsorption capacity of the silica gel is 2.6 mg / g. After 5 cycles of regeneration, the adsorption capacity is still stable at 2.4 mg / g, indicating that the silica gel in the scheme of the present invention is regenerable and can be recycled.

[0137] The present invention tests the TOC content of nanofiltration effluent obtained after nanofiltration membrane separation and the TOC content of nanofiltration effluent obtained after regenerated nanofiltration membrane separation. After calculation, the initial separation efficiency of the nanofiltration membrane is 39.3%. After 5 cycles of regeneration, the separation efficiency is still stable at 37.1%, indicating that the nanofiltration membrane of the present invention is regenerative and can be recycled.

[0138] Comparative Example 1

[0139] At 15°C and pH 3, the TOC content in petrochemical wastewater is 175ppm;

[0140] 1) The petrochemical wastewater is filtered through a glass fiber filter membrane with a pore size of 0.45 μm to obtain pretreated petrochemical wastewater. The TOC content of the pretreated petrochemical wastewater effluent is 148 ppm.

[0141] 2) The pretreated petrochemical wastewater is transported to a container with an average pore size of 2.12 nm and a large pore volume of 0.09 cm 3 / g of bituminous coal activated carbon in the primary adsorption unit, the bituminous coal activated carbon accounts for 0.8% of the mass of the pretreated petrochemical wastewater, and adsorbs for 0.5h at 25°C to complete the primary adsorption treatment, and then the bituminous coal activated carbon after the primary adsorption treatment and the primary adsorption effluent are filtered and separated to obtain the primary adsorption effluent.

[0142] 3) The first-stage adsorption effluent is transported to a container with an average pore size of 2.51 nm, a mesopore (2-50 nm) and a pore volume of 0.37 cm 3 / g, CAS model 112926-00-8, silica gel accounts for 1.2% of the mass of the first-stage adsorption effluent, adsorbs at 25°C for 0.5h, completes the second-stage adsorption treatment, and then filters and separates the silica gel after the second-stage adsorption treatment and the second-stage adsorption effluent to obtain the second-stage adsorption effluent. The TOC content of the second-stage adsorption effluent is 29ppm when detected by a water quality detector.

[0143] Figure 8 This is a graph showing the change in TOC content during the treatment of petrochemical wastewater in Example 1. It can be seen that after pretreatment, primary adsorption and secondary adsorption, the TOC content of the petrochemical wastewater is reduced from the initial 175ppm to 29ppm, which does not meet the "Petrochemical Industry Pollutant Emission Standards" (GB 31571-2015, including the 2024 amendment).

[0144] Comparative Example 2

[0145] At 15°C and pH 3, the TOC content in petrochemical wastewater is 175ppm;

[0146] 1) The petrochemical wastewater is filtered through a glass fiber filter membrane with a pore size of 0.45 μm to obtain pretreated petrochemical wastewater. The TOC content of the pretreated petrochemical wastewater effluent is 148 ppm.

[0147] 2) The pretreated petrochemical wastewater is transported to a container with an average pore size of 2.12 nm and a large pore volume of 0.09 cm 3 / g bituminous coal activated carbon adsorption unit, the bituminous coal activated carbon accounts for 0.8% of the mass of the pretreated petrochemical wastewater, and adsorption is completed at 25°C for 0.5h, and then the bituminous coal activated carbon after adsorption treatment and the adsorption effluent are filtered and separated to obtain the primary adsorption effluent.

[0148] 3) The adsorbed water is passed through a polyamide nanofiltration membrane with a pore size of 0.2 nm and membrane separation is performed at a pressure of 0.8 MPa. After membrane separation, nanofiltration effluent and concentrated water are obtained. The nanofiltration effluent is transported to a water outlet tank, and the concentrated water is transported to a pretreatment tank.

[0149] The TOC content of the nanofiltration effluent was detected by a water quality detector and was 25ppm.

[0150] Fig. 9 The TOC content change diagram of petrochemical wastewater treatment in Example 2 shows that the petrochemical wastewater is treated by pretreatment, primary adsorption and nanofiltration. The water permeation flux of the polyamide nanofiltration membrane is 1.54 L·m -2 ·h -1 bar -1The TOC content of petrochemical wastewater dropped from the initial 175ppm to 25ppm, which did not meet the "Petrochemical Industry Pollutant Emission Standards" (GB31571-2015, including the 2024 amendment).

[0151] Comparative Example 3

[0152] At 15°C and pH 3, the TOC content in petrochemical wastewater is 175ppm;

[0153] 1) The petrochemical wastewater is filtered through a glass fiber filter membrane with a pore size of 0.45 μm to obtain pretreated petrochemical wastewater. The TOC content of the pretreated petrochemical wastewater effluent is 148 ppm.

[0154] 2) The pretreated petrochemical wastewater is transported to a container with an average pore size of 2.51 nm, a mesopore (2-50 nm) and a pore volume of 0.37 cm 3 / g, in the adsorption unit of silica gel with CAS model 112926-00-8, silica gel accounts for 1.2% of the mass of the pretreated petrochemical wastewater, and the adsorption treatment is completed at 25°C for 0.5h, and then the silica gel after adsorption treatment and the adsorbed water are filtered and separated to obtain the adsorbed water.

[0155] 3) The adsorbed water is passed through a polyamide nanofiltration membrane with a pore size of 0.2 nm and membrane separation is performed at a pressure of 0.8 MPa. After membrane separation, nanofiltration effluent and concentrated water are obtained. The nanofiltration effluent is transported to a water outlet tank, and the concentrated water is transported to a pretreatment tank.

[0156] The TOC content of the nanofiltration effluent was detected by a water quality detector and was 21 ppm.

[0157] Fig.10 The TOC content change diagram of petrochemical wastewater treatment in Example 3 shows that the petrochemical wastewater is treated by pretreatment, secondary adsorption and nanofiltration. The water permeation flux of the polyamide nanofiltration membrane is 2.58 L·m -2 ·h -1 bar -1 The TOC content of petrochemical wastewater dropped from the initial 175ppm to 21ppm, which did not meet the "Petrochemical Industry Pollutant Emission Standards" (GB31571-2015, including the 2024 amendment).

[0158] Comparative Example 4

[0159] At 15°C and pH 3, the TOC content in petrochemical wastewater is 175ppm;

[0160] 1) The petrochemical wastewater is filtered through a glass fiber filter membrane with a pore size of 0.45 μm to obtain pretreated petrochemical wastewater. The TOC content of the pretreated petrochemical wastewater effluent is 148 ppm.

[0161] 2) The pretreated petrochemical wastewater was passed through a polyamide nanofiltration membrane with a pore size of 0.2 nm and membrane separation was performed at a pressure of 0.8 MPa. Nanofiltration effluent and concentrated water were obtained after membrane separation. The nanofiltration effluent was transported to a water outlet tank. The TOC content of the nanofiltration effluent was detected by a water quality detector and was 42 ppm.

[0162] Fig.11 The TOC content change diagram of petrochemical wastewater treatment in Example 4 shows that the petrochemical wastewater was treated by pretreatment and nanofiltration, and the water permeation flux of the polyamide nanofiltration membrane was 0.98 L·m -2 ·h -1 bar -1 The TOC content of petrochemical wastewater dropped from the initial 175ppm to 42ppm, which did not meet the "Petrochemical Industry Pollutant Emission Standard" (GB 31571-2015, including the 2024 amendment).

[0163] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for deep treatment of petrochemical wastewater based on graded adsorption coupled membrane process, characterized in that: The following steps are involved: 1) filtering the petrochemical wastewater to obtain pretreated petrochemical wastewater; 2) subjecting the pretreated petrochemical wastewater to primary adsorption treatment to obtain primary adsorption effluent, wherein the adsorbent used in the primary adsorption treatment is activated carbon; 3) subjecting the primary adsorption effluent to secondary adsorption treatment to obtain secondary adsorption effluent, wherein the adsorbent used in the secondary adsorption treatment is silica gel; 4) Passing the secondary adsorption effluent through a nanofiltration membrane for membrane separation to obtain effluent.

2. The method according to claim 1, characterized in that The filtering material is a glass fiber filter membrane, and the pore size of the glass fiber filter membrane is 0.45 μm.

3. The method according to claim 1, characterized in that The temperature of the first-stage adsorption treatment is 15-60° C. and the time is 5-30 minutes.

4. The method according to claim 3, characterized in that The activated carbon accounts for 0.1-10% of the mass of the pre-treated petrochemical wastewater.

5. The method according to claim 1, characterized in that The temperature of the secondary adsorption treatment is 15-60° C. and the time is 5-30 minutes.

6. The method according to claim 5, characterized in that The silica gel accounts for 0.1-20% of the mass of the first-stage adsorption water.

7. The method according to claim 1, characterized in that The nanofiltration membrane is a polyamide nanofiltration membrane, and the pore size of the nanofiltration membrane is 0.2-1 nm; the pressure of the membrane separation is 0.08-1.2 MPa.

8. The method according to any one of claims 1 and 3 to 6, characterized in that: The method further comprises: The activated carbon and silica gel after adsorption saturation are regenerated and used for primary adsorption treatment and secondary adsorption treatment respectively, wherein the regeneration temperature of the activated carbon is 300-600°C, and the regeneration temperature of the silica gel is 80-220°C.

9. The method according to claim 1, characterized in that: The method further comprises: The concentrated water intercepted by membrane separation is used as petrochemical wastewater and steps 1) to 4) are performed again; and When the water obtained by membrane separation does not meet the discharge requirements, steps 1) to 4) are repeated.

10. A system for deep treatment of petrochemical wastewater based on graded adsorption coupled membrane process, used for implementing the method of claims 1 to 9, characterized in that: It includes a filtration unit, a primary adsorption unit, a secondary adsorption unit, a nanofiltration unit, a water outlet tank, a water quality detection unit, an activated carbon regeneration unit and a silica gel regeneration unit. The filtering unit is used to filter petrochemical wastewater, and its input end is connected to the petrochemical wastewater inlet end; The input end of the primary adsorption unit is connected to the output end of the filtration unit, the primary adsorption unit is filled with activated carbon, and the primary adsorption unit is provided with a primary water outlet and a primary adsorbent output end; The input end of the secondary adsorption unit is connected to the primary water outlet end of the primary adsorption unit, silica gel is installed in the secondary adsorption unit, and the secondary adsorption unit is provided with a secondary water outlet end and a secondary adsorbent output end; The input end of the nanofiltration unit is connected to the secondary water outlet end of the secondary adsorption unit. The nanofiltration unit is equipped with a membrane assembly of a nanofiltration membrane. The nanofiltration unit is provided with a first output end and a second output end. The first output end is connected to the input end of the filtration unit and is used to transport the retained concentrated water to the filtration unit. The second output end is used to output the purified water after nanofiltration. The input end of the water outlet tank is connected to the second output end of the nanofiltration unit and is used to store purified water after nanofiltration. The water outlet tank is provided with a circulating water outlet and a drainage end, and the circulating water outlet is connected to the input end of the filtration unit. The water quality detection unit is arranged in the water outlet tank and is used to detect the water quality of the purified water; The input end of the activated carbon regeneration unit is connected to the primary adsorbent output end of the primary adsorption unit, and the output end of the activated carbon regeneration unit is connected to the input end of the primary adsorption unit; The input end of the silica gel regeneration unit is connected to the secondary adsorbent output end of the secondary adsorption unit, and the output end of the silica gel regeneration unit is connected to the input end of the secondary adsorption unit.

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