A coking wastewater treatment process

Abstract

The present invention relates to the field of wastewater treatment technology, and in particular to a coking wastewater treatment process, comprising the following steps: S1, preliminarily adjusting the collected coking wastewater, passing it through a sedimentation tank, and then through an air flotation tank to obtain pretreated coking wastewater; S2, passing the pretreated coking wastewater into an electrochemical reaction cell, setting current density and voltage parameters; S3, adding a coking wastewater treatment agent to the electrochemical reaction cell, stirring evenly, turning on a light source, and irradiating the electrochemical reaction cell to obtain treated water; S4, passing the treated water through a secondary sedimentation tank and then through a flocculation tank to obtain clean water. Wherein, the coking wastewater treatment agent refers to a γ-Bi2MoO6 / graphene-loaded acrylic acid grafted polythiophene complex. In the present invention, electrochemical treatment is first carried out in the electrochemical reaction cell, and after adding the coking wastewater treatment agent, rapid and efficient deep treatment is carried out under irradiation of a light source, and the coking wastewater treatment agent can be recycled.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, in particular to a coking wastewater treatment process. Background Art

[0002] Coking wastewater is a major challenge for the coal chemical industry. This wastewater contains a large number of toxic and hazardous substances, such as phenols, cyanide, benzene, and ammonia nitrogen, causing serious environmental pollution. Due to overcapacity and product diversification in the coking industry, underutilized resources have led to increasingly prominent environmental issues, with the discharge and treatment of coking wastewater becoming a pressing issue. Amidst water shortages in my country, wastewater volumes from the coal chemical industry are increasing annually. Coking wastewater from the coking industry is particularly high in pollutants, making its treatment extremely challenging. Coking wastewater has a complex composition, including residual ammonia, tar plant wastewater, gas intercooler drainage, benzene recovery wastewater, indirect cooling water, and dust removal wash water. Among these, organic pollutants such as phenols and polycyclic aromatic hydrocarbons (PAHs) are found in high concentrations, particularly volatile phenols and CODcr values, making it one of the most challenging wastewaters to treat industrially. Traditional coking wastewater treatment methods, including pretreatment, biochemical treatment, and advanced treatment, are not always effective and can lead to secondary pollution. Therefore, in order to solve this problem, we need to seek more efficient and environmentally friendly treatment technologies to ensure that coking wastewater can be properly treated and protect our water resources and environment.

[0003] In the prior art, conventional coking wastewater is usually treated biochemically and deeply by adding a composite flocculant or a microbial agent. After searching, the invention patent with Chinese patent publication number CN103922453A discloses a coking wastewater flocculant and its preparation method and application. The coking wastewater flocculant is composed of magnesium salt, aluminum salt, ferrous salt, lime and starch. After reacting with pollutants in the wastewater, it can effectively aggregate and precipitate pollutants. However, the coking wastewater flocculant forms a stable precipitate after the reaction and cannot be converted into an effective flocculant again. Therefore, a new coking wastewater flocculant needs to be added for each treatment. The invention patent with Chinese patent publication number CN104528951A discloses a coking wastewater treatment microbial agent and its application. The microbial agent can enhance the removal rate of refractory organic matter, but it takes 24h-48h to complete the degradation of refractory organic matter in the coking wastewater. If there are more refractory organic matter, it will take longer. Summary of the Invention

[0004] The object of the present invention is to provide a coking wastewater treatment process, which can efficiently treat coking wastewater through pretreatment, electrochemical treatment, addition of coking wastewater treatment agent and post-treatment.

[0005] The technical problems to be solved by the present invention are: the composite flocculant cannot be reused and the microbial agent takes a long time to treat coking wastewater.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A coking wastewater treatment process comprises the following steps:

[0008] S1. Preliminary conditioning of the collected coking wastewater is performed by passing it through a sedimentation tank for 15-20 minutes, and then passing it through an air flotation tank for 10-15 minutes to obtain pretreated coking wastewater;

[0009] S2. Pass the pretreated coking wastewater into the electrochemical reaction cell, set the current density and voltage parameters, and perform electrochemical treatment for 5 min-15 min;

[0010] S3. Adding a coking wastewater treatment agent to the electrochemical reaction cell, stirring evenly, turning on a light source, and irradiating the cell for 30-60 minutes to obtain treated water, wherein the coking wastewater treatment agent is a γ-Bi2MoO6 / graphene-loaded acrylic acid-grafted polythiophene composite;

[0011] S4. The treated water is passed through a secondary sedimentation tank for sedimentation for 5-10 minutes, and then passed through a flocculation tank for flocculation for 5-10 minutes to obtain purified water.

[0012] The current density in step S2 is 50 mA / cm 2 -100mA / cm 2 And voltage 10V-20V.

[0013] The light source in step S3 includes one or more of ultraviolet light, visible light and sunlight.

[0014] Furthermore, the coking wastewater treatment agent in step S3 is prepared by the following steps:

[0015] A1. Add polythiophene to a 0.5 mol / L acetone solution, place in a stainless steel polytetrafluoroethylene-lined reactor, add ammonium persulfate and N,N-dimethylformamide, and then add acrylic acid. Under nitrogen protection, stir and heat to 80°C-90°C, react for 1-3 hours, and distill under reduced pressure for purification to obtain an acrylic acid-grafted polythiophene solution;

[0016] A2. Ultrasonic dispersion of the γ-Bi2MoO6 / graphene suspension in the acrylic acid grafted polythiophene solution, controlling the temperature at 60°C-70°C, magnetic stirring for 30 min-40 min, cooling to room temperature, filtering, discarding the filtrate, washing with deionized water and ethanol, and drying to obtain a γ-Bi2MoO6 / graphene-loaded acrylic acid grafted polythiophene composite, i.e., a coking wastewater treatment agent.

[0017] In the step A1, the mass ratio of polythiophene, ammonium persulfate, N,N-dimethylformamide and acrylic acid is (10-15): (1-3): (0.5-0.7): (20-30).

[0018] In step A2, the volume ratio of the γ-Bi2MoO6 / graphene suspension and the acrylic acid grafted polythiophene solution is (2-3): (3-4).

[0019] Furthermore, the γ-Bi2MoO6 / graphene suspension in step A2 is prepared by the following steps:

[0020] Bismuth nitrate and sodium molybdate were added to deionized water, stirred for 15 min-30 min, the pH value was adjusted to 11-12, and the mixture was transferred to a stainless steel polytetrafluoroethylene-lined high-temperature reactor, the temperature was controlled at 180°C-200°C, the reaction was carried out for 12h-18h, and the mixture was taken out and placed in a constant temperature oscillator, the temperature was adjusted at 50°C and the vibration frequency was at 250rpm-300rpm. The graphene powder was ultrasonically dispersed in the solution, oscillated for 4h-6h, and cooled to room temperature to obtain a γ-Bi2MoO6 / graphene suspension.

[0021] The mass ratio of the bismuth nitrate, sodium molybdate and graphene powder is (20-25): (15-20): (18-22).

[0022] Beneficial effects of the present invention:

[0023] 1. In the technical solution of this invention, acrylic acid is grafted onto polythiophene in the coking wastewater treatment agent and then uniformly dispersed on the γ-Bi2MoO6 / graphene surface. This further increases the number of catalytically active sites and promotes the separation and migration of photogenerated electrons and holes, thereby improving the efficiency of photocatalytic degradation of coking wastewater. Graphene, as a two-dimensional sheet substrate, provides a large specific surface area. γ-Bi2MoO6 nanoparticles are loaded and dispersed on the graphene through electrostatic physical adsorption. The acrylic acid grafted polythiophene, supported by the γ-Bi2MoO6 / graphene surface, improves electron transfer efficiency and enhances the stability and durability of the composite.

[0024] 2. In the technical solution of the present invention, when the composite is irradiated with light having an energy greater than or equal to the band gap energy of γ-Bi2MoO6, electrons in the valence band of γ-Bi2MoO6 are excited and transition to the conduction band, forming photogenerated electrons and holes. Due to the high electrical conductivity of graphene and polythiophene, the photogenerated electrons quickly migrate to the surfaces of graphene and polythiophene, suppressing the recombination of electrons and holes. The electrons transferred to graphene and polythiophene can be transferred to other electron acceptors through an external circuit (electrochemical reaction cell), or react with oxygen molecules in the water to generate superoxide radicals, which oxidize and decompose organic matter. On the other hand, the holes remaining in the valence band of γ-Bi2MoO6 react with adsorbed water molecules or hydroxyl ions to generate hydroxyl radicals, which oxidize and decompose organic matter in coking wastewater. In this process, the acrylic acid-grafted polythiophene provides contact area and more active sites, enhancing the composite's adsorption of pollutants while suppressing the aggregation of γ-Bi2MoO6 nanoparticles and improving the stability of the catalyst.

[0025] 3. In the technical solution of the present invention, an electrochemical treatment is first performed in the electrochemical reaction cell, i.e., power is applied for 5-15 minutes to accelerate the directional movement of particles in the coking wastewater and pre-treat organic matter. After the addition of a coking wastewater treatment agent, the coking wastewater is rapidly and efficiently treated under light. The light source can be a commonly used lighting, UV lamp, or sunlight, making it easily accessible. Furthermore, the coking wastewater treatment agent can be recycled after post-processing such as washing and drying, avoiding the single-use limitation of traditional flocculants. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] Example 1

[0028] The γ-Bi2MoO6 / graphene suspension is prepared by the following steps:

[0029] Add 20g of bismuth nitrate and 15g of sodium molybdate to deionized water, stir for 20min, adjust the pH value to 11, transfer to a stainless steel polytetrafluoroethylene-lined high-temperature reactor, control the temperature at 190°C, react for 16h, take out and place in a constant temperature oscillator, adjust the temperature at 50°C and the vibration frequency at 250rpm, ultrasonically disperse 18g of graphene powder in the solution, oscillate for 5h, and cool to room temperature to obtain a γ-Bi2MoO6 / graphene suspension.

[0030] Example 2

[0031] The γ-Bi2MoO6 / graphene suspension is prepared by the following steps:

[0032] Add 22.5 g of bismuth nitrate and 17.5 g of sodium molybdate to deionized water, stir for 20 min, adjust the pH value to 11, transfer to a stainless steel polytetrafluoroethylene-lined high-temperature reactor, control the temperature at 190 ° C, react for 16 h, take out and place in a constant temperature oscillator, adjust the temperature at 50 ° C, the vibration frequency at 250 rpm, ultrasonically disperse 20 g of graphene powder in the solution, oscillate for 5 h, and cool to room temperature to obtain a γ-Bi2MoO6 / graphene suspension.

[0033] Example 3

[0034] The γ-Bi2MoO6 / graphene suspension is prepared by the following steps:

[0035] Add 25g of bismuth nitrate and 20g of sodium molybdate to deionized water, stir for 20min, adjust the pH value to 11, transfer to a stainless steel polytetrafluoroethylene-lined high-temperature reactor, control the temperature at 190°C, react for 16h, take out and place in a constant temperature oscillator, adjust the temperature at 50°C and the vibration frequency at 250rpm, ultrasonically disperse 22g of graphene powder in the solution, oscillate for 5h, and cool to room temperature to obtain a γ-Bi2MoO6 / graphene suspension.

[0036] Example 4

[0037] The coking wastewater treatment agent comprises the following steps:

[0038] A1. Add 10 g of polythiophene to a 0.5 mol / L acetone solution, place in a stainless steel polytetrafluoroethylene-lined reactor, add 1 g of ammonium persulfate and 0.5 g of N,N-dimethylformamide, and then add 20 g of acrylic acid. Under nitrogen protection, stir and heat to 80°C, react for 1 hour, and distill under reduced pressure for purification to obtain an acrylic acid-grafted polythiophene solution;

[0039] A2. Ultrasonic dispersion of 20 mL of the γ-Bi2MoO6 / graphene suspension prepared in Example 1 in 30 mL of the acrylic acid-grafted polythiophene solution was performed, the temperature was controlled at 60°C, magnetic stirring was performed for 30 min, the mixture was cooled to room temperature, filtered, the filtrate was discarded, the mixture was washed with deionized water and ethanol, and dried to obtain a γ-Bi2MoO6 / graphene-supported acrylic acid-grafted polythiophene composite, i.e., a coking wastewater treatment agent.

[0040] Example 5

[0041] The coking wastewater treatment agent comprises the following steps:

[0042] A1. Add 12.5 g of polythiophene to a 0.5 mol / L acetone solution, place in a stainless steel polytetrafluoroethylene-lined reactor, add 2 g of ammonium persulfate and 0.6 g of N,N-dimethylformamide, and then add 25 g of acrylic acid. Under nitrogen protection, stir and heat to 80°C, react for 1 hour, and distill under reduced pressure for purification to obtain an acrylic acid-grafted polythiophene solution;

[0043] A2. Ultrasonic dispersion of 25 mL of the γ-Bi2MoO6 / graphene suspension prepared in Example 2 in 35 mL of the acrylic acid-grafted polythiophene solution was performed, the temperature was controlled at 60°C, magnetic stirring was performed for 30 min, the mixture was cooled to room temperature, filtered, the filtrate was discarded, the mixture was washed with deionized water and ethanol, and dried to obtain a γ-Bi2MoO6 / graphene-supported acrylic acid-grafted polythiophene composite, i.e., a coking wastewater treatment agent.

[0044] Example 6

[0045] The coking wastewater treatment agent comprises the following steps to prepare:

[0046] A1. Add 15 g of polythiophene to a 0.5 mol / L acetone solution, place in a stainless steel polytetrafluoroethylene-lined reactor, add 3 g of ammonium persulfate and 0.7 g of N,N-dimethylformamide, and then add 30 g of acrylic acid. Under nitrogen protection, stir and heat to 80°C, react for 1 hour, and distill under reduced pressure for purification to obtain an acrylic acid-grafted polythiophene solution;

[0047] A2. Ultrasonic dispersion of 30 mL of the γ-Bi2MoO6 / graphene suspension prepared in Example 3 in 40 mL of the acrylic acid-grafted polythiophene solution was performed, the temperature was controlled at 60°C, magnetic stirring was performed for 30 min, the mixture was cooled to room temperature, filtered, the filtrate was discarded, the mixture was washed with deionized water and ethanol, and dried to obtain a γ-Bi2MoO6 / graphene-supported acrylic acid-grafted polythiophene composite, i.e., a coking wastewater treatment agent.

[0048] Example 7

[0049] A coking wastewater treatment process comprises the following steps:

[0050] S1. Preliminary conditioning of the collected coking wastewater is performed by passing it through a sedimentation tank for 15 minutes and then through an air flotation tank for 10 minutes to obtain pretreated coking wastewater;

[0051] S2: The pretreated coking wastewater is passed into the electrochemical reaction cell and the current density is set to 75 mA / cm 2 and voltage 15 V, electrochemical treatment 10 min;

[0052] S3. Add the coking wastewater treatment agent prepared in Example 4 to the electrochemical reaction cell, stir evenly, turn on the light source, and illuminate for 45 minutes to obtain treated water;

[0053] S4. The treated water is passed through a secondary sedimentation tank for 10 minutes, and then passed through a flocculation tank for 10 minutes to obtain purified water.

[0054] Example 8

[0055] A coking wastewater treatment process comprises the following steps:

[0056] S1. Preliminary conditioning of the collected coking wastewater is performed by passing it through a sedimentation tank for 15 minutes and then through an air flotation tank for 10 minutes to obtain pretreated coking wastewater;

[0057] S2: The pretreated coking wastewater is passed into the electrochemical reaction cell and the current density is set to 75 mA / cm 2 and voltage 15 V, electrochemical treatment 10 min;

[0058] S3. Add the coking wastewater treatment agent prepared in Example 5 to the electrochemical reaction cell, stir evenly, turn on the light source, and illuminate for 45 minutes to obtain treated water;

[0059] S4. The treated water is passed through a secondary sedimentation tank for 10 minutes, and then passed through a flocculation tank for 10 minutes to obtain purified water.

[0060] Example 9

[0061] A coking wastewater treatment process comprises the following steps:

[0062] S1. Preliminary conditioning of the collected coking wastewater is performed by passing it through a sedimentation tank for 15 minutes and then through an air flotation tank for 10 minutes to obtain pretreated coking wastewater;

[0063] S2: The pretreated coking wastewater is passed into the electrochemical reaction cell and the current density is set to 75 mA / cm 2 and voltage 15 V, electrochemical treatment 10 min;

[0064] S3. Add the coking wastewater treatment agent prepared in Example 6 to the electrochemical reaction cell, stir evenly, turn on the light source, and illuminate for 45 minutes to obtain treated water;

[0065] S4. The treated water is passed through a secondary sedimentation tank for 10 minutes, and then passed through a flocculation tank for 10 minutes to obtain purified water.

[0066] Comparative Example 1

[0067] A coking wastewater treatment process comprises the following steps:

[0068] S1. Preliminary conditioning of the collected coking wastewater is performed by passing it through a sedimentation tank for 15 minutes and then through an air flotation tank for 10 minutes to obtain pretreated coking wastewater;

[0069] S2: The pretreated coking wastewater is passed into the electrochemical reaction cell and the current density is set to 75 mA / cm 2 and voltage 15 V, electrochemical treatment 10 min;

[0070] S3. Add a commercially available composite flocculant (including magnesium salt, aluminum salt, ferrous salt, lime and starch) to the electrochemical reaction cell, stir evenly, turn on the light source, and illuminate for 45 minutes to obtain treated water;

[0071] S4. The treated water is passed through a secondary sedimentation tank for 10 minutes, and then passed through a flocculation tank for 10 minutes to obtain purified water.

[0072] Comparative Example 2

[0073] A coking wastewater treatment process comprises the following steps:

[0074] S1. Preliminary conditioning of the collected coking wastewater is performed by passing it through a sedimentation tank for 15 minutes and then through an air flotation tank for 10 minutes to obtain pretreated coking wastewater;

[0075] S2: The pretreated coking wastewater is passed into the electrochemical reaction cell and the current density is set to 75 mA / cm 2 and voltage 15 V, electrochemical treatment 10 min;

[0076] S3, without adding any reagents, turn on the light source, illuminate for 45 minutes, and obtain treated water;

[0077] S4. Pass the treated water through the secondary sedimentation tank for 10 minutes, and then pass it through the flocculation tank for 10 minutes.

[0078] According to GB 16171-2012 "Pollutant Emission Standard for Coking Chemical Industry", a coking wastewater was treated using the methods of Examples 7-9 and Comparative Examples 1-2, and a blank control group was set up. The results are shown in Table 1:

[0079] Table 1. Concentration of each indicator after treatment (unit: mg / L, except pH value)

[0080]

[0081]

[0082] Table 2. Removal rate of some indicators after treatment in Examples 7-9 (unit: %)

[0083] project Example 7 Example 8 Example 9 Removal rate of biochemical oxygen demand in five days 97.49 97.21 97.21 Chemical oxygen demand removal rate 97.57 97.73 97.41 Ammonia nitrogen removal rate 94.20 94.20 95.65

[0084] As shown in Tables 1 and 2, all indicators in Examples 7-9 meet the direct pollutant emission limits for newly built enterprises, while Comparative Example 1 only partially meets these limits. The average five-day biochemical oxygen demand removal rates for Examples 7-9 are 97.30%, the average chemical oxygen demand removal rate is 97.57%, and the average ammonia nitrogen removal rate is 94.68%. This demonstrates that pretreatment, electrochemical treatment, addition of a coking wastewater treatment agent, and post-treatment can effectively treat coking wastewater.

[0085] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0086] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A coking wastewater treatment process, characterized in that: The following steps are involved: S1. Preliminary conditioning of the collected coking wastewater is performed by passing it through a sedimentation tank for 15-20 minutes, and then passing it through an air flotation tank for 10-15 minutes to obtain pretreated coking wastewater; S2. Pass the pretreated coking wastewater into the electrochemical reaction cell, set the current density and voltage parameters, and perform electrochemical treatment for 5 min-15 min; S3. Adding a coking wastewater treatment agent to the electrochemical reaction cell, stirring evenly, turning on a light source, and irradiating the cell for 30-60 minutes to obtain treated water, wherein the coking wastewater treatment agent is a γ-Bi2MoO6 / graphene-loaded acrylic acid-grafted polythiophene composite; S4, passing the treated water through a secondary sedimentation tank for 5-10 minutes, and then passing it through a flocculation tank for 5-10 minutes to obtain purified water; The coking wastewater treatment agent in step S3 is prepared by the following steps: A1. Add polythiophene to a 0.5 mol / L acetone solution, place in a stainless steel polytetrafluoroethylene-lined reactor, add ammonium persulfate and N,N-dimethylformamide, and then add acrylic acid. Under nitrogen protection, stir and heat to 80°C-90°C, react for 1-3 hours, and distill under reduced pressure for purification to obtain an acrylic acid-grafted polythiophene solution; A2. Ultrasonic dispersion of the γ-Bi2MoO6 / graphene suspension in the acrylic acid grafted polythiophene solution, controlling the temperature at 60°C-70°C, magnetic stirring for 30 min-40 min, cooling to room temperature, filtering, discarding the filtrate, washing with deionized water and ethanol, and drying to obtain a γ-Bi2MoO6 / graphene-supported acrylic acid grafted polythiophene composite, i.e., a coking wastewater treatment agent; In step A1, the mass ratio of polythiophene, ammonium persulfate, N,N-dimethylformamide and acrylic acid is (10-15): (1-3): (0.5-0.7): (20-30); In step A2, the volume ratio of the γ-Bi2MoO6 / graphene suspension and the acrylic acid grafted polythiophene solution is (2-3): (3-4); The γ-Bi2MoO6 / graphene suspension in step A2 is prepared by the following steps: Add bismuth nitrate and sodium molybdate to deionized water, stir for 15-30 minutes, adjust the pH value to 11-12, transfer to a stainless steel polytetrafluoroethylene-lined high-temperature reactor, control the temperature at 180-200°C, react for 12-18 hours, take out and place in a constant temperature oscillator, adjust the temperature at 50°C and the vibration frequency at 250-300 rpm, ultrasonically disperse the graphene powder in the solution, oscillate for 4-6 hours, and cool to room temperature to obtain a γ-Bi2MoO6 / graphene suspension; The mass ratio of bismuth nitrate, sodium molybdate and graphene powder is (20-25): (15-20): (18-22).

2. A coking wastewater treatment process according to claim 1, characterized in that, In step S2, the current density is 50 mA / cm²-100 mA / cm² and the voltage is 10 V-20 V.

3. A coking wastewater treatment process according to claim 1, characterized in that: In step S3, the light source includes one or more of ultraviolet light, visible light and sunlight.

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