Coal coking wastewater resourceful treatment process of coupling hydrogen production by electrocatalytic degradation

Abstract

The application discloses a coal coking wastewater resource treatment process of electrocatalytic degradation coupling hydrogen production, relates to the technical field of water treatment, and the method mixes the coal coking wastewater with other wastewater after preliminary biochemical treatment, carries out alkali flocculation treatment, two-stage membrane filtration treatment, reverse osmosis concentrated water electrolysis treatment and alkali liquor recycling treatment, compared with traditional Fenton oxidation, electrochemical oxidation, resin or activated carbon adsorption and other methods, no secondary pollution is caused, the separation cost is low, the degradation of organic pollutants and electrolytic hydrogen production are effectively realized, the resource utilization and full-quantitative treatment of the coal coking wastewater are realized, and the method has a wide application prospect in the field of high-salt organic wastewater treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a resource-based treatment process for coal coking wastewater by electrocatalytic degradation coupled with hydrogen production. Background Art

[0002] Coal chemical companies, which use coal as their primary raw material, generate large quantities of coking wastewater during processes such as coal gasification, direct coal liquefaction, and coking. This wastewater is primarily composed of pollutants such as phenolic organic compounds and inorganic salts, exhibiting poor biodegradability and high biotoxicity. Improper discharge can have serious environmental impacts. Existing treatment methods for coal chemical wastewater include sequentially employing physicochemical pretreatment, biochemical treatment, and advanced treatment to reduce organic matter. The biochemical effluent is then reused through reverse osmosis to reduce salinity. Due to the high concentrations of pollutants such as organic matter and inorganic salts in coal chemical wastewater, the concentrations of inorganic salts and recalcitrant organic matter in the reverse osmosis concentrate obtained after the reverse osmosis process increase exponentially, resulting in high levels of dissolved solids, high chemical oxygen demand, and high color. Current treatment methods primarily involve disposal through methods such as surface water discharge, deep well injection, evaporation ponds, and traditional crystallizers. These treatment processes not only pose challenges such as secondary pollution and low efficiency, but also fail to achieve effective carbon sequestration and resource utilization.

[0003] Chinese patent document CN102674634A discloses a coal chemical wastewater treatment process. The invention process includes primary wastewater treatment and secondary wastewater treatment. The primary wastewater treatment steps are: after the wastewater undergoes primary pH adjustment, it undergoes a primary electro-Fenton micro-electrolysis catalytic reaction treatment, a primary neutralization aeration oxidation treatment, and after precipitation, it undergoes biodegradation treatment; the secondary wastewater treatment steps are: the water after the primary wastewater treatment is subjected to secondary pH adjustment and a secondary electro-Fenton micro-electrolysis catalytic reaction treatment, followed by secondary neutralization aeration oxidation treatment, sludge precipitation, electrocatalytic oxidation treatment, flocculation treatment, multiphase flow electro-flotation treatment, and then filtration through an ultrafiltration membrane and reverse osmosis desalination to achieve reuse after discharge. This invention combines electrochemical, biological treatment, and membrane treatment technologies. Although there is no secondary pollution and the treatment effect is stable, the process steps are relatively cumbersome.

[0004] Chinese patent publication CN116425347A discloses a method, apparatus, system, and method for preparing a supported metal oxide catalyst for treating coal chemical wastewater. The method comprises: adding a flocculant and magnetic powder to the coal chemical wastewater to be treated, allowing the flocculant and magnetic powder to combine with suspended pollutants in the coal chemical wastewater to form a sediment; removing the sediment to obtain wastewater free of suspended pollutants; and then contacting the wastewater with ozone in the presence of a catalyst in a countercurrent manner to carry out a catalytic reaction, thereby obtaining treated water free of impurities. Although this method for treating coal chemical wastewater accelerates the sedimentation of suspended pollutants in the coal chemical wastewater through a magnetic coagulation and precipitation process, it does not concentrate and reduce the wastewater, which results in a large-scale catalytic system with significant investment costs and energy consumption. Furthermore, the flocs formed by the flocculation of suspended pollutants with the flocculant and magnetic powder require separate disposal.

[0005] Chinese patent publication CN113582410A discloses a method for treating coal chemical wastewater. The method involves reacting the coal chemical wastewater with sodium hydroxide to obtain magnesium hydroxide and a first filtrate after separation. The first filtrate is then reacted with a soluble carbonate to obtain calcium carbonate and a second filtrate after separation. The second filtrate is then subjected to nanofiltration to obtain nanofiltration concentrate and nanofiltration product water. The nanofiltration product water is further subjected to high-pressure reverse osmosis treatment to obtain reverse osmosis concentrate and reverse osmosis product water. Finally, the reverse osmosis concentrate is subjected to diaphragm electrolysis to obtain low-concentration brine, sodium hydroxide, and chlorine. Although this inventive method can produce high-purity chlorine and sodium hydroxide byproducts, and the sodium hydroxide can be used to recover magnesium hydroxide, the technology does not treat organic matter in the coal chemical wastewater. The diaphragm electrolysis consumes a lot of energy, and the low-concentration brine after discharge is not treated.

[0006] Therefore, it is necessary to improve the existing coal coking wastewater treatment process in order to achieve resource utilization and full-scale treatment of coal coking wastewater and avoid secondary pollution. Summary of the Invention

[0007] In response to the shortcomings of the existing technology, the present invention provides a resource-based treatment process for coal coking wastewater by electrocatalytic degradation coupled with hydrogen production. The process can not only degrade organic pollutants in coal coking wastewater, but also couple with electrolysis to produce hydrogen, thereby improving treatment energy efficiency while reducing carbon emissions, thereby realizing resource utilization of coal coking wastewater. The process has broad application prospects in the field of high-salt organic wastewater treatment.

[0008] The specific technical solutions adopted are as follows:

[0009] A process for resource-based treatment of coal coking wastewater by electrocatalytic degradation coupled with hydrogen production, comprising:

[0010] (1) Coal coking wastewater is mixed with other wastewater that has undergone preliminary biochemical treatment, and then transferred to a regulating tank for flocculation with alkali. At the same time, the water quality and water volume of the wastewater are homogenized and adjusted. The treated wastewater is then transferred to a sedimentation tank to recover and purify the precipitate;

[0011] (2) the wastewater treated in step (1) is filtered through two-stage membranes, wherein the first stage of membrane filtration is ceramic microfiltration membrane filtration, and the second stage of membrane filtration is reverse osmosis membrane filtration, and the reverse osmosis concentrated water is collected and the reverse osmosis fresh water is reused;

[0012] (3) transferring the reverse osmosis concentrated water collected in step (2) to an electrolytic cell for electrolytic treatment, wherein an oxidation reaction occurs at the anode of the electrolytic cell to degrade organic pollutants, and a hydrogen evolution reaction occurs at the cathode of the electrolytic cell to generate hydrogen; separating the gas-water mixture generated by the electrolytic treatment, removing impurities and purifying the gas to obtain high-purity hydrogen, and reusing the liquid as the alkali solution required for the alkali flocculation process in step (1);

[0013] The anode includes an anode substrate and an anode catalyst layer, and the cathode includes a cathode substrate and a cathode catalyst layer. Both the anode substrate and the cathode substrate are nickel foam, the anode catalyst is a nickel-iron-based layered double hydroxide catalyst, and the cathode catalyst is a nickel-molybdenum alloy catalyst.

[0014] The method of the present invention includes an alkaline flocculation process, a two-stage membrane filtration process, a reverse osmosis concentrated water electrolysis process, and an alkaline liquor reuse process. Alkaline flocculation precipitates calcium, magnesium, silicates, and other metals in the wastewater, achieving resource recovery of soluble metal components. A two-stage filtration system using ceramic membranes and reverse osmosis membranes effectively reduces the amount of liquid processed during the electrolysis process, while the filtered reverse osmosis fresh water is reused in the coal coking production process, reducing operating costs. A specific catalyst is used to electrocatalyze organic matter oxidation and hydrogen evolution reactions, degrading organic pollutants in the wastewater while simultaneously coupling electrolytic hydrogen production. The produced hydrogen is sprayed with alkaline liquor to remove impurities, producing high-purity hydrogen with a purity greater than 99.999%. The waste liquid after electrolysis is reused in the regulating tank as the alkaline liquor required for the alkaline flocculation process, achieving resource utilization and fully quantitative treatment of coal coking wastewater.

[0015] Optionally, other wastewater includes domestic wastewater, washing wastewater, circulating water sewage or desalting water station drainage, etc. After being collected, other wastewater is subjected to preliminary biochemical treatment in a biochemical reaction tank, and denitrifying bacteria are used to oxidize ammonia nitrogen into nitrate in an environment with sufficient oxygen supply. After the biochemical reaction, other wastewater is mixed with coal coking wastewater to participate in subsequent processes.

[0016] Preferably, the regulating tank is provided with a microporous aerator, and air is introduced from the microporous aerator to aerate the wastewater, and the wastewater is evenly mixed by gas movement; the pH of the wastewater system is maintained at ≥12 after homogenization adjustment; on the one hand, aeration can increase the dissolved oxygen content in the wastewater, prevent the precipitation of solid insoluble matter produced after alkali flocculation, and accelerate the volatilization of volatile components in the wastewater and the oxidation of iron salts; on the other hand, the pH of the wastewater system is ≥12, which can convert soluble calcium, magnesium, silicates and other components in the wastewater into insoluble solid precipitates.

[0017] Preferably, the alkali solution used in the alkali flocculation process is the liquid obtained by gas-liquid separation after electrolysis in step (3), or a mixed liquid of the liquid obtained by gas-liquid separation after electrolysis in step (3) and the alkali solution recycled after gas impurity removal, and the main component is potassium hydroxide.

[0018] Preferably, the sedimentation tank is provided with a baffle, which can reduce the flow rate and fluid pulsation, so that the solid insoluble matter in the wastewater is precipitated, and the precipitate is discharged through the sewage outlet at the bottom of the sedimentation tank, and the clear liquid is discharged through the outlet of the sedimentation tank for two-stage membrane filtration.

[0019] Preferably, in step (2), a ceramic microfiltration membrane system is used for filtration, and the ceramic microfiltration membrane system maintains aeration to flush the surface of the ceramic membrane, thereby extending the service life of the ceramic membrane and improving the filtration efficiency.

[0020] The working principle of reverse osmosis membrane is that water molecules will spontaneously permeate from the side of low osmotic pressure through the semipermeable membrane to the side of high osmotic pressure, while the ionic components, organic matter and other solutes in the water will be intercepted by the semipermeable membrane. When the pressure applied to the feed side is greater than the osmotic pressure difference across the membrane, the water molecules will flow in the opposite direction, from the high concentration side to the low concentration side, thereby achieving the enrichment of solutes in the wastewater.

[0021] The reverse osmosis fresh water is returned to the coal coking production process for use, while the reverse osmosis concentrated water is enriched with organic matter, inorganic salts in the raw coal coking wastewater and alkali solution used in the flocculation process. The pH of the reverse osmosis concentrated water is ≥14. Preferably, in the reverse osmosis concentrated water, the chloride ion concentration is ≥0.3 mol / L, the sulfate ion concentration is ≥0.1 mol / L, the nitrate ion concentration is ≥0.1 mol / L, the chemical oxygen demand COD is ≥1000 mg / L, and the component <1 kDa in the total organic carbon TOC accounts for 50-70%.

[0022] Reverse osmosis concentrate has the following three characteristics: (1) high salinity, with chloride ion concentration ≥0.3 mol / L, sulfate ion concentration ≥0.1 mol / L, and nitrate ion concentration ≥0.1 mol / L; (2) high organic matter concentration, with chemical oxygen demand (COD) ≥1000 mg / L, and components <1 kDa in the total organic carbon (TOC) accounting for 50-70%, and organic matter (including phenols, polycyclic aromatic hydrocarbons, and nitrogen-containing heterocyclic compounds) in the raw coal coking wastewater is enriched; (3) strong alkalinity, with the pH of reverse osmosis concentrate ≥14.

[0023] Preferably, in step (3), the normal operating temperature in the electrolytic cell is controlled at 70-90°C, the temperature can be raised from room temperature to 90°C, and the operating pressure is 0.4-0.8 MPa.

[0024] Preferably, the method for preparing the anode is as follows: preparing a catalyst deposition solution containing nickel nitrate and ferric nitrate as components, using the catalyst deposition solution as an electrolyte, assembling a three-electrode system, using two titanium plates plated with ruthenium-iridium alloy as counter electrodes, and using the cleaned nickel foam as a working electrode, applying a voltage of -0.8--1.0V vs. SCE for 4000-6000s to prepare a nickel foam with a nickel-iron-based layered double hydroxide catalyst deposited thereon, which is used as the anode in the electrolysis treatment of step (3).

[0025] Further preferably, in the catalyst deposition liquid, the concentration of nickel nitrate is 16-20 mmol / L, and the concentration of ferric nitrate is 4-10 mmol / L.

[0026] Preferably, the cathode preparation method is as follows: preparing a catalyst plating solution containing nickel sulfate, sodium citrate, potassium chloride, ammonium molybdate, potassium hydroxide, and ammonia water, using the catalyst plating solution as an electrolyte, assembling a three-electrode system, using two titanium plates plated with ruthenium-iridium alloy as counter electrodes, and cleaned nickel foam as a working electrode, applying 100-200 mA / cm 2 The current density is maintained for 2000-4000s to prepare a nickel foam plated with a dense nickel-molybdenum alloy catalyst, which is used as a cathode in the electrolysis treatment of step (3).

[0027] Further preferably, in the catalyst electroplating solution, the concentration of nickel sulfate is 30-50 mmol / L, the concentration of sodium citrate is 0.2-0.35 mol / L, the concentration of potassium chloride is 0.2-0.35 mol / L, the concentration of ammonium molybdate is 20-30 mmol / L, the concentration of potassium hydroxide is 0.2-0.4 mol / L, and the concentration of ammonia water is 0.05-0.08 wt%.

[0028] During the electrolysis treatment process, the reaction can be divided into the active electrode organic matter oxidation half-reaction on the anode side and the hydrogen evolution reaction half-reaction on the cathode side. The two half-reactions respectively realize the electrocatalytic degradation of organic matter in the wastewater and the electrolytic hydrogen production. During the entire reaction process, OH in the reverse osmosis concentrated water - Not consumed.

[0029] In an alkaline environment, hydroxyl radicals (·OH) adsorbed on the active sites (M) on the surface of the anode catalyst react to produce high oxides (MO) or superoxides, which act as redox pairs for organic pollutants (R) during the electrocatalytic oxidation process. The specific reaction process is as follows:

[0030] 2M+4OH - →2M(·OH)+O2+2H2O+O2

[0031] M(·OH)+OH - →MO+H2O+e -

[0032] MO+R→M+RO

[0033] MO→M+0.5O2

[0034] During the electrolysis process, the organic pollutants in the introduced reverse osmosis concentrated water are oxidized by active oxygen to achieve degradation of the organic pollutants. The electrocatalytic oxidation process generates products such as short-chain organic matter, carbon dioxide and oxygen.

[0035] At the same time, under alkaline conditions, the active sites (M) on the surface of the cathode catalyst adsorb water molecules to undergo a hydrogen evolution reaction, decomposing water to generate hydrogen. The reaction process of the half reaction is as follows:

[0036] M+H2O+e - →MH*+OH -

[0037] MH*+H2O+e - →M+OH - +H2

[0038] During the electrolytic treatment process, the electrolytic cell system is closed, there is no risk of toxic gas leakage, and it is environmentally friendly. The gases produced by the anode organic matter oxidation half-reaction and the cathode hydrogen evolution half-reaction will not mix. After leaving the electrolytic cell system, the gas and water will be separated separately, and the hydrogen produced at the cathode will be purified for use.

[0039] The gas-water mixture produced at the anode and cathode in the electrolytic cell is discharged and collected separately. After the gas and water are separated, the gas produced at the anode is discharged into the atmosphere after passing through a dust filter, and the gas produced at the cathode is sprayed with alkaline solution to remove organic matter. It is further deoxidized by catalytic thermal catalysis and dried to obtain high-purity hydrogen.

[0040] Furthermore, high-purity hydrogen is hydrogen with a purity of ≥99.999%.

[0041] The liquid obtained by gas-water separation after electrolytic treatment in step (3) has strong alkalinity, low organic matter concentration, and HPLC peak area reduced by more than 50%, and can be used as alkali liquid in the alkali flocculation process; the recycled alkali liquid after the gas alkali liquid generated at the cathode is sprayed to remove impurities can also be used in the alkali flocculation process, thereby reducing the alkali consumption of the process.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) Compared with traditional Fenton oxidation, electrochemical oxidation, resin or activated carbon adsorption methods, the method of the present invention does not cause secondary pollution, has low separation costs, and effectively achieves the degradation of organic pollutants and electrolytic hydrogen production.

[0044] (2) The method of the present invention not only reduces the cost and process oxygen consumption, but also realizes the resource utilization of soluble metal components such as calcium, magnesium, and silicate in coal coking wastewater by reusing the liquid obtained by gas-liquid separation after electrolysis treatment (high-concentration alkali-containing wastewater) and the liquid after gas impurity removal alkali liquid spraying treatment in the alkali flocculation process.

[0045] (3) The method of the present invention adopts a two-stage membrane filtration process of ceramic microfiltration membrane filtration and reverse osmosis membrane filtration, which not only realizes the reuse of the obtained reverse osmosis fresh water in the coal coking production process, but also effectively reduces the treatment volume of the concentrated liquid (reverse osmosis concentrated water) in the final electrolysis process, thereby reducing operating costs;

[0046] (4) The present invention is based on a specific nickel-based catalyst and an electrolytic treatment process. It removes difficult-to-degrade organic pollutants in reverse osmosis concentrated water through electrolytic treatment, and simultaneously produces high-purity hydrogen, thereby realizing the resource utilization and full-scale treatment of coal coking wastewater, and avoiding the secondary pollution to the environment caused by the evaporation and landfill treatment of conventional reverse osmosis concentrated liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic flow chart of the process for resource-based treatment of coal coking wastewater by electrocatalytic degradation coupled with hydrogen production in the present invention. DETAILED DESCRIPTION

[0048] The present invention will be further described below with reference to the following examples and accompanying drawings. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0049] The nickel foam substrate used in the examples was purchased from Suzhou Shengernuo Technology Co., Ltd.

[0050] The anode was prepared by the following method:

[0051] (1) Anode substrate pretreatment: The nickel foam substrate was cut into 100 mm*100 mm size, immersed in acetone, and ultrasonically treated at 50 W for 3 min; the nickel foam was removed and rinsed with deionized water; the nickel foam washed with acetone was immersed in 3 mol / L hydrochloric acid and ultrasonically treated at 50 W for 3 min; the nickel foam was removed and rinsed with deionized water; the nickel foam washed with hydrochloric acid was immersed in deionized water again and ultrasonically treated at 50 W for 3 min; the nickel foam was removed and immersed in ethanol and ultrasonically treated at 50 W for 3 min; the washed nickel foam was removed and dried at 60°C;

[0052] (2) Weigh 2.61 g of nickel nitrate hexahydrate and 1.21 g of ferric nitrate nonahydrate, and prepare 500 mL of anode catalyst deposition liquid using deionized water; use the catalyst deposition liquid as the electrolyte to assemble a three-electrode system, using two titanium plates plated with ruthenium-iridium alloy as the counter electrode, a nickel plate as the guide electrode frame, and cleaned nickel foam as the working electrode. The nickel foam substrate is immersed in the catalyst deposition liquid as the working electrode, and a surface voltage of -0.9 V vs. SCE is applied for 4500 s; after completion, a nickel foam with a nickel-iron-based double hydroxide catalyst deposited thereon is prepared, which is the anode.

[0053] The cathode was prepared by the following method:

[0054] (1) Cathode substrate pretreatment: The nickel foam substrate was cut into a size of 100 mm*100 mm, immersed in acetone, and ultrasonically treated at 50 W for 3 min; the nickel foam was removed and rinsed with deionized water; the nickel foam washed with acetone was immersed in 3 mol / L hydrochloric acid and ultrasonically treated at 50 W for 3 min; the nickel foam was removed and rinsed with deionized water; the nickel foam washed with hydrochloric acid was immersed in deionized water again and ultrasonically treated at 50 W for 3 min; the nickel foam was removed and immersed in ethanol and ultrasonically treated at 50 W for 3 min; the washed nickel foam was removed and dried at 60°C;

[0055] (2) Weigh 5.257 g of nickel nitrate hexahydrate, 35.292 g of sodium citrate, 8.946 g of potassium chloride, 14.138 g of ammonium molybdate tetrahydrate, and 6.785 g of potassium hydroxide, and measure 1.2 mL of 25% ammonia water. Use deionized water to prepare 500 mL of cathode catalyst plating solution. Use the catalyst plating solution as the electrolyte to assemble a three-electrode system, using two titanium plates plated with ruthenium-iridium alloy as the counter electrode, a nickel plate as the guide electrode frame, and cleaned nickel foam as the working electrode. Immerse the nickel foam substrate as the working electrode in the catalyst plating solution and apply 150 mA / cm 2 The current density was maintained for 3600s; after completion, a nickel foam plated with a dense nickel-molybdenum alloy was prepared, which was the cathode.

[0056] Example 1

[0057] In this embodiment, the process for resource utilization of coal coking wastewater by electrocatalytic degradation coupled with hydrogen production is as follows: Figure 1 As shown; specifically including the following steps:

[0058] (1) Coal coking wastewater (wastewater generated by coal gasification, direct coal liquefaction, coking and other processes) from a certain factory is mixed with domestic wastewater from the factory that has undergone preliminary biochemical treatment. The domestic wastewater from the factory is collected and then subjected to preliminary biochemical treatment in a biochemical reaction tank. Denitrifying bacteria are used to oxidize ammonia nitrogen into nitrate in an environment with sufficient oxygen supply. The wastewater is then transferred to a regulating tank and flocculated with alkali (a mixed liquid of liquid obtained by gas-liquid separation after electrolysis and alkali solution recycled after gas impurity removal, the main component of which is potassium hydroxide). At the same time, the water quality and water quantity of the wastewater are homogenized to control the pH of the wastewater system to be ≥12. The regulating tank is provided with a microporous aerator, and air is introduced from the microporous aerator to aerate the wastewater, and the wastewater is evenly mixed by gas movement. The treated wastewater is then transferred to a sedimentation tank, which is provided with a baffle. The precipitate is discharged through the sewage outlet at the bottom of the sedimentation tank, and the clear liquid is discharged through the water outlet of the sedimentation tank. The purified precipitate is recovered to realize the resource utilization of metal salts.

[0059] (2) The wastewater treated in the above steps is introduced into a ceramic microfiltration membrane filtration system for ceramic microfiltration membrane filtration. The ceramic microfiltration membrane filtration system maintains aeration to flush the surface of the ceramic membrane, thereby extending the service life of the ceramic membrane, improving the filtration efficiency, removing suspended particulate matter, and avoiding pollution to subsequent treatment devices; the wastewater after ceramic microfiltration membrane filtration enters a reverse osmosis membrane filtration system for reverse osmosis membrane filtration to achieve enrichment of solutes in the wastewater, obtain reverse osmosis concentrated water and collect it, and the reverse osmosis fresh water is reused in the coal coking production process. The test results show that the pH value of the reverse osmosis concentrated water is 14.3, the potassium hydroxide concentration is 2 mol / L, the chloride ion concentration is 0.381 mol / L, the sulfate ion concentration is 0.143 mol / L, the nitrate ion concentration is 0.124 mol / L, the chemical oxygen demand (COD) is 2600 mg / L, and the <1 kDa component in the total organic carbon (TOC) accounts for about 65%;

[0060] (3) The reverse osmosis concentrated water (containing alkaline concentrated organic waste liquid) is pressurized to 0.8 MPa and enters the alkaline wastewater electrocatalytic degradation coupled hydrogen production electrolytic cell. The normal operating temperature in the electrolytic cell is controlled at 80°C (temperature control is achieved by controlling the flow rate of wastewater flowing into the electrolytic cell). A nickel foam deposited with a nickel-iron-based layered double hydroxide catalyst is used as the anode, and a nickel foam deposited with a nickel-molybdenum alloy is used as the cathode. The anode in the electrolytic cell undergoes an oxidation reaction to achieve degradation of organic pollutants, and the cathode in the electrolytic cell undergoes a hydrogen evolution reaction to generate hydrogen gas; the degradation of organic pollutants (R) is coupled with electrolytic hydrogen production, wherein the half reaction occurring at the anode can be expressed as R+2OH- →RO+H2O; the half reaction at the cathode can be expressed as 2H2O→2OH - +H2;

[0061] After the electrolysis is completed, the gas-water mixture produced at the anode and cathode in the electrolytic cell is discharged and collected separately. The gas-water mixture rotates in a cylindrical cyclone gas-water separator, and the gas-liquid separation is achieved by utilizing the difference in centrifugal force between the gas and liquid. The gas produced at the anode passes through a dust filter and is discharged into the atmosphere. The gas produced at the cathode is sprayed with potassium hydroxide solution for adsorption to remove impurities such as chlorine and organic vapor. After catalytic thermal deoxidation and drying, the purified hydrogen with a purity greater than 99.999% is produced. The liquid obtained from the gas-liquid separation after electrolysis is highly alkaline with an organic matter concentration of less than 300 mg / L, and is reused as the alkaline solution required for the alkaline flocculation process. The liquid produced at the cathode after the alkaline solution spray treatment can also be used in the alkaline flocculation process, thereby reducing the process alkali consumption.

[0062] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A process for resource utilization of coal coking wastewater by electrocatalytic degradation coupled with hydrogen production, characterized in that: include: (1) Coal coking wastewater is mixed with other wastewater that has undergone preliminary biochemical treatment, and then transferred to a regulating tank, where alkali is added for flocculation. At the same time, the water quality and water volume of the wastewater are homogenized and adjusted. After homogenization, the pH of the wastewater system is maintained at ≥12. The treated wastewater is then transferred to a sedimentation tank to recover and purify the precipitate. (2) The wastewater treated in step (1) is filtered through two-stage membranes, wherein the first stage of membrane filtration is ceramic microfiltration membrane filtration, and the second stage of membrane filtration is reverse osmosis membrane filtration, and reverse osmosis concentrated water is collected and the reverse osmosis fresh water is reused; the pH of the reverse osmosis concentrated water is ≥14, the chloride ion concentration is ≥0.3 mol / L, the sulfate ion concentration is ≥0.1 mol / L, the nitrate ion concentration is ≥0.1 mol / L, the chemical oxygen demand COD is ≥1000 mg / L, and the total organic carbon TOC has a component of <1 kDa accounting for 50-70%; (3) transferring the reverse osmosis concentrated water collected in step (2) to an electrolytic cell for electrolysis treatment, wherein an oxidation reaction occurs at the anode of the electrolytic cell to degrade organic pollutants, and a hydrogen evolution reaction occurs at the cathode of the electrolytic cell to generate hydrogen; The normal operating temperature in the electrolytic cell is controlled at 70-90°C and the operating pressure is 0.4-0.8 MPa; the gas-water mixture produced by the electrolytic treatment is separated, the gas is purified to obtain high-purity hydrogen, and the liquid is recycled as the alkali solution required for the alkali flocculation process in step (1); In step (3), the anode includes an anode substrate and an anode catalyst layer, the cathode includes a cathode substrate and a cathode catalyst layer, the anode substrate and the cathode substrate are both nickel foam, the anode catalyst is a nickel-iron-based layered double hydroxide catalyst, and the cathode catalyst is a nickel-molybdenum alloy catalyst; The anode preparation method comprises: preparing a catalyst deposition solution containing nickel nitrate and ferric nitrate, using the catalyst deposition solution as an electrolyte, assembling a three-electrode system, using two titanium plates plated with ruthenium-iridium alloy as counter electrodes, and cleaned nickel foam as a working electrode, applying a voltage of -0.8 to -1.0 V vs. SCE for 1800 to 6000 seconds, to prepare a nickel foam with a nickel-iron-based layered double hydroxide catalyst deposited thereon, which is the anode; The cathode preparation method is as follows: preparing a catalyst plating solution containing nickel sulfate, sodium citrate, potassium chloride, ammonium molybdate, potassium hydroxide, and ammonia water, using the catalyst plating solution as an electrolyte, assembling a three-electrode system, using two titanium plates plated with ruthenium-iridium alloy as counter electrodes, and cleaned nickel foam as a working electrode, applying 100-200 mA / cm 2 A current of a current density of 1000-1500 nm was applied for 2000-4000 s to prepare a nickel foam plated with a nickel-molybdenum alloy catalyst, which was the cathode.

2. The process for resource utilization of coal coking wastewater by electrocatalytic degradation coupled with hydrogen production according to claim 1, characterized in that: The regulating tank is provided with a microporous aerator, through which air is introduced to aerate the wastewater, and the wastewater is evenly mixed through the movement of gas.

3. The process for resource utilization of coal coking wastewater by electrocatalytic degradation coupled with hydrogen production according to claim 1, characterized in that: The sedimentation tank is provided with a baffle, and the sediment is discharged through the sewage outlet at the bottom of the sedimentation tank, and the clear liquid is led out through the water outlet of the sedimentation tank.

4. The process for resource utilization of coal coking wastewater by electrocatalytic degradation coupled with hydrogen production according to claim 1, characterized in that: In the catalyst deposition liquid, the concentration of nickel nitrate is 16-20 mmol / L, and the concentration of ferric nitrate is 4-10 mmol / L.

5. The process for resource utilization of coal coking wastewater by electrocatalytic degradation coupled with hydrogen production according to claim 1, characterized in that: In the catalyst electroplating solution, the concentration of nickel sulfate is 30-50 mmol / L, the concentration of sodium citrate is 0.2-0.35 mol / L, the concentration of potassium chloride is 0.2-0.35 mol / L, the concentration of ammonium molybdate is 20-30 mmol / L, the concentration of potassium hydroxide is 0.2-0.4 mol / L, and the concentration of ammonia water is 0.05-0.08wt%.

6. The process for resource utilization of coal coking wastewater by electrocatalytic degradation coupled with hydrogen production according to claim 1, characterized in that: The gas-water mixture produced at the anode and cathode in the electrolytic cell is discharged and collected separately. After the gas and water are separated, the gas produced at the anode is discharged into the atmosphere after passing through a dust filter, and the gas produced at the cathode is sprayed with alkaline solution to remove organic matter. After further catalytic thermal deoxidation and drying, high-purity hydrogen is obtained. High-purity hydrogen is hydrogen with a purity of ≥99.999%.

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