COD degradation device and use method, catalyst and its preparation method and application

Abstract

The present invention provides a device for degrading COD, a method for using the device, a catalyst, and a preparation method and application thereof, to solve the problems in current practical projects such as the large footprint of COD removal devices, poor COD removal effect under high-salt conditions, and excessively long reaction time. The present invention combines multifunctional adsorption catalytic reaction and multi-stage advanced oxidation technology through a multi-stage "adsorption + catalytic in-situ degradation". The catalyst utilizes coal gangue and / or gasified slag to carry out an in-situ redox reaction with the carbon and iron oxide inherent in fly ash to prepare multivalent and multi-scale catalyst materials without the need for external catalyst raw materials and complex preparation processes. The device for degrading COD includes an advanced oxidation in-situ reaction unit, an ozone aeration dosing unit, an oxidizing agent and acid-base dosing unit, a mixing unit, a water production recovery unit, and a control unit.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial wastewater treatment, and in particular relates to a device for degrading COD, a method for using the device, a catalyst, and a preparation method and application thereof. Background Art

[0002] Mine brine is the concentrated brine produced by the mine water produced during coal mining after desalination and reverse osmosis treatment. In 2019, the amount of mine water produced in my country was about 7.1 billion m3. 3 , and among them Na + , Ca 2+ 、Cl - 、SO4 2- Plasma concentrations can reach as high as 1,000mg / L to 4,000mg / L, with some cases exceeding 40,000mg / L. Direct discharge can harm the ecological environment through surface water pollution (increased salinity), soil salinization, loss of surface vegetation, and contamination of shallow groundwater. Furthermore, over 70% of my country's coal resources are located in water-scarce provinces such as Shanxi, Shaanxi, Xinjiang, and Inner Mongolia. If the large amount of mine water generated by coal mining activities is not promptly treated and recycled, it will further exacerbate the water shortages in these regions.

[0003] The mine water treatment process currently implemented in the Inner Mongolia-Shaanxi region primarily consists of three steps: desalination, secondary concentration, and evaporation and crystallization. The core process for desalination and secondary concentration utilizes reverse osmosis concentration technology, while auxiliary processes include pretreatment procedures such as hardness and impurity removal to meet reverse osmosis feedwater requirements. During actual project operation, the brine after two-stage reverse osmosis concentration of mine water contains high levels of impurities and chemical oxygen demand (COD), which in turn affects the stability of the subsequent evaporation and crystallization process and the quality of the crystallized salt. Therefore, effective measures are required to partially remove the COD from the brine after reverse osmosis concentration before evaporation and crystallization.

[0004] Advanced Oxidation Process (AOP) is currently commonly used in industry to degrade COD in high-salt wastewater. However, the traditional Fenton advanced oxidation process not only generates iron sludge during COD degradation, which is detrimental to the subsequent operation of evaporation equipment and the quality of crystallized salt, but also suffers from the problem of poor COD removal due to the short half-life and low redox potential of oxygen-active species such as hydroxyl radicals during the reaction process.

[0005] Chinese patent CN110342740B discloses a method and system for purifying saline organic wastewater. The pre-treatment process involves membrane separation and concentration of wastewater to produce concentrated product water and recyclable reuse water. The concentrated product water undergoes organic separation treatment to produce separated wastewater. The separated wastewater is pH-adjusted to an acidic pH and then subjected to Fenton oxidation to produce pre-oxidized product water. After further pH adjustment, the pre-oxidized product water undergoes biochemical oxidation to produce biochemical product water, which is then mixed with the saline organic wastewater for recycling. However, in actual engineering applications, the concentrated solution after membrane separation and concentration has a high salt content, resulting in unsatisfactory treatment results.

[0006] Chinese patent application CN113562903A discloses a multi-cycle oxidation device and treatment process for treating high-salinity, refractory COD wastewater. The process involves adding a catalyst and hydrogen peroxide to the wastewater, which then flows into reaction tanks. The wastewater then remains in the first reaction tank for 10 minutes to 1.5 hours, then in the second reaction tank for another 10 minutes to 1.5 hours. Finally, the wastewater is neutralized in a neutralization tank, adjusted for pH, and then flows into a sedimentation tank. However, in actual engineering applications, this process involves multiple tanks, complex processes, high investment, and poor treatment results.

[0007] Chinese patent CN107500456B discloses a device and method for treating high-COD wastewater using a composite advanced oxidation process. The device includes a hydrogen peroxide catalytic treatment unit, an ozone catalytic oxidation treatment unit, an ozone generator, and an exhaust gas treatment unit. The UV lamps used have a short lifespan and poor light transmittance in the wastewater, impacting the system's operating efficiency and stability. The UV lamps generate significant heat, and the added temperature control system increases the complexity and energy consumption of the device. Furthermore, the numerous process units involved can lead to unstable operation.

[0008] In actual industrial wastewater zero-discharge projects, after secondary reverse osmosis concentration, the TDS (total dissolved solids) is greater than 50g / L. Ozone + hydrogen peroxide or ozone + metal catalysts are often used for COD degradation treatment. The COD removal device occupies a large area and the reaction time is too long. In the actual treatment process, the cost of metal catalysts is relatively high, and the catalysts are mostly fixed at the bottom of the reaction device, resulting in particulate matter in the wastewater and catalytic reaction products being deposited on the catalyst surface, affecting the effect of the catalyst in degrading COD. The COD degradation rate does not exceed 50%. Summary of the Invention

[0009] The purpose of the present invention is to solve the problems of high catalyst cost, large COD removal device footprint, poor COD removal effect under high salt conditions, and long reaction time in current practical projects, and to provide a COD degradation device and use method, a catalyst, and its preparation method and application.

[0010] To achieve the above objectives, the technical solutions provided by the present invention are:

[0011] A method for preparing a multifunctional adsorption catalyst is characterized in that it comprises the following steps:

[0012] 1) Preprocessing

[0013] The dried and cooled raw material 1 is ground to a particle size between 0.3 mm and 3 mm for later use (the raw material 1 is placed in a dryer for later use. Considering the adsorption performance and performance, the raw material 1 with a particle size between 0.3 mm and 3 mm is selected); the raw material 1 is one or a mixture of coal gangue and gasified slag; wherein the raw material 1 has a mass fraction of 1% to 10% of iron oxide, a mass fraction of 10% to 40% of aluminum oxide, a mass fraction of 30% to 50% of silicon dioxide, a mass fraction of 3% to 20% of carbon, and the remainder is doped inorganic elements such as K, P, Ba, and S;

[0014] Dry fly ash with a particle size between 10 μm and 50 μm for later use (put into a dryer for later use); wherein the fly ash has a mass fraction of 3%-10% iron oxide, 10%-30% aluminum oxide, 30%-50% silicon dioxide, 1%-10% unburned carbon, and the remainder is doped inorganic elements such as K, P, Ba, and S; the fly ash can be fluidized bed fly ash collected from power plants and sieved through a 500-mesh sieve;

[0015] Only by using the raw materials of the above specifications and fly ash can the multifunctional adsorption catalyst required by the present invention be prepared;

[0016] 2) Activation

[0017] 2.1) Weigh the fly ash pretreated in step 1) and raw material 1 in a mass ratio of 1:1-3:1, add water and stir evenly to form a first slurry of 10wt%-60wt%;

[0018] 2.2) adding oxalic acid to the first slurry prepared in step 2.1), followed by heating and stirring to react, and after the reaction is complete, drying the product by spray drying to obtain a first composite material;

[0019] In step 2), the product is dried by spray drying, which allows the ferrous oxalate to be dispersed and fully contacted with the carrier, laying the foundation for the subsequent formation of nano-scale catalytic materials;

[0020] 3) Alkali leaching

[0021] The first composite material obtained in step 2) is mixed with water to prepare a second slurry with a concentration of 10 wt% to 60 wt%, and an inorganic alkali solution (such as sodium hydroxide) is added to the second slurry to adjust the pH of the second slurry to 10-12, followed by heating and stirring to react. After the reaction is completed, the product is dried by spray drying to obtain a second composite material;

[0022] Similarly, in step 3), the product is dried by spray drying, which can fully expose the iron oxide and provide sites, further laying the foundation for the subsequent formation of nano-scale catalytic materials;

[0023] 4) Sintering

[0024] The second composite material obtained in step 3) is placed in a circulating inert atmosphere and subjected to rotary sintering to obtain a multifunctional adsorption catalyst. The sintering process is specifically as follows:

[0025] The first stage: sintering temperature is 600℃-800℃, sintering time is 1h-2h, and mixed particles are obtained;

[0026] The second stage: the sintering temperature is 1100℃-1300℃, and the sintering time is 1h-2h to make the mixed particles bonded.

[0027] The purpose of rotary sintering is to prevent the material from agglomerating or compacting during sintering, which would affect product quality. In the first stage of the sintering process, raw material 1 and residual carbon in fly ash are used as reducing agents for a thermal reduction reaction. In the second stage of sintering, silicates and aluminates in raw material 1 and fly ash are used as binders to prepare a composite material with a planetary structure, which is a multifunctional adsorption catalyst containing nano-iron and multivalent states of iron oxide and ferrous oxide. It needs to be cooled and stored in a dryer for future use.

[0028] Furthermore, in step 1), the drying temperature of the raw material 1 is 80°C-120°C, the drying time is 0.5h-2h, and the raw material 1 is placed in a high-energy ball mill for grinding, the speed of the high-energy ball mill is 500r / min-1000r / min, and the ball milling time is 0.5h-2h;

[0029] The drying temperature of fly ash is 80℃-120℃, and the drying time is 0.5h-2h;

[0030] In step 2.2), after oxalic acid is added to the first slurry, its molar concentration is 0.1 mol / L-1 mol / L (i.e., the molar concentration of oxalic acid in the first slurry after addition); the reaction temperature is 60°C-80°C, the reaction time is 0.5 h-2 h, and the stirring speed is 500 r / min-2000 r / min. The amount of oxalic acid required is intended to remove calcium carbonate and react with iron oxide to form ferrous oxalate, which lays the foundation for subsequent reduction to elemental iron;

[0031] The product is dried by spray drying at a temperature of 150°C-300°C and a pressure of 0.1Mpa-1Mpa;

[0032] In step 3), after the inorganic alkali solution is added to the second slurry, its molar concentration is 0.1 mol / L-3 mol / L (i.e., the molar concentration of the inorganic alkali solution in the second slurry after addition); the reaction temperature is 60°C-80°C, the reaction time is 0.5h-2h, and the stirring speed is 500r / min-2000r / min;

[0033] The product is dried by spray drying at a temperature of 150°C-300°C and a pressure of 0.1Mpa-1Mpa;

[0034] In step 4), the second composite material obtained in step 3) is placed in a high-temperature tube furnace and sintered in a nitrogen atmosphere with a circulation flow rate of 10L / min-30L / min, which can achieve the effect of uniform heating and dispersed sintering; wherein the rotation speed of the high-temperature tube furnace is 50r / min-200r / min, and the heating rate is 5°C / min-15°C / min.

[0035] The preparation mechanism of the above multifunctional adsorbent catalyst is:

[0036] First, large-particle raw material (coal gangue and / or gasified slag) and small-particle fly ash powder are obtained by grinding and screening in a high-energy ball mill, and fly ash + raw material mixture is prepared according to a specific mass ratio;

[0037] Second, oxalic acid is used to activate the mixture. The oxalic acid soaking removes calcium carbonate in the mixture, dredges the pores, and reacts with iron oxide to form ferrous oxalate.

[0038] Third, use alkaline solution to leach silicon dioxide and aluminum oxide, dredge the pores, improve the adsorption performance of fly ash and raw material one, and expose the iron oxide contained in the mixture to provide sites for subsequent reduction modification;

[0039] Fourth, a high-temperature in-situ reduction reaction is carried out under the protection of an inert gas. First, the residual carbon in the raw material 1 and the fly ash is used to reduce the ferrous oxide produced by the decomposition of ferrous oxalate. At the same time, the iron oxide exposed on the surface of the solid particles is reduced to generate nano-iron, which is directly adsorbed in situ on the surface of the fly ash and the raw material 1. By controlling the sintering reaction time, reaction temperature and other conditions, the amount of iron oxide and ferrous oxide reduced to nano-iron is controlled. Secondly, at a certain rotation speed and after high-temperature sintering, the raw material 1 and the fly ash, under the action of their own silicates and aluminates, adhere to each other to form a catalyst composite material with a planetary structure of a certain particle size.

[0040] The multifunctional adsorption catalyst prepared by the above preparation method is a carbon-based multifunctional catalytic material doped with inorganic elements, which has a planetary structure and includes a carrier part and a catalytic part;

[0041] The carrier part is a spherical, sheet-like or irregularly shaped porous structure with a size of 1mm-50mm, a pore diameter of 1nm-1000nm, and a porosity of 10%-80%;

[0042] The catalytic part is attached to the surface or pores of the carrier part, and has a particle size of 1nm-100nm.

[0043] Furthermore, the catalytic part is nano-iron, iron oxide and ferrous oxide.

[0044] At the same time, the present invention also provides the use of the multifunctional adsorption catalyst prepared by the above preparation method in degrading COD in concentrated brine in mines.

[0045] Based on the application of the multifunctional adsorption catalyst, the present invention provides a COD degradation device, which is special in that it includes an advanced oxidation in-situ reaction unit, an ozone aeration dosing unit, an oxidizing agent and acid and alkali dosing unit, a mixing unit, a water recovery unit and a control unit;

[0046] The advanced oxidation in-situ reaction unit includes a plurality of reaction tanks connected in series along the water flow direction. The number of reaction tanks can be adjusted according to the specification requirements of the COD degradation device, such as 2-5, and generally 3 are set. They are sequentially called: primary reaction tank, secondary reaction tank and tertiary reaction tank along the water flow direction;

[0047] The tank body of each reaction tank is a double-layer hollow structure, the outer layer is the outer shell of the reaction tank, and the inner layer is a water-permeable shell, and the cavity between the outer layer and the inner layer is filled with the multifunctional adsorption catalyst prepared by the above-mentioned preparation method; a number of water-permeable holes are evenly arranged on the water-permeable shell; a water inlet pipe and a water outlet pipe are respectively provided at both ends of the tank body; wherein the water inlet pipe is coaxially arranged with the tank body, and its pipe diameter is smaller than the hole diameter of the water-permeable shell, and the water outlet pipe is arranged at the end of the tank body corresponding to the cavity between the outer layer and the inner layer, and the water inlet flow rate is greater than the water outlet flow rate, ensuring that the incoming water can enter the cavity through the water-permeable holes and stay there, fully contacting with the multifunctional adsorption catalyst, and improving the catalytic efficiency; the reaction tanks are arranged in series, the water inlet pipes of the odd-numbered reaction tanks are located at the top of the tank body, and the water inlet pipes of the even-numbered reaction tanks are located at the bottom of the tank body;

[0048] The ozone aeration dosing unit adds ozone to the first reaction tank (i.e., the primary reaction tank) of the advanced oxidation in-situ reaction unit; the oxidant and acid-base dosing unit adds the oxidant and acid-base to the mixing unit, which are fully and evenly mixed with the wastewater to be degraded entering the mixing unit before entering the advanced oxidation in-situ reaction unit;

[0049] The wastewater to be degraded is degraded in the advanced oxidation in-situ reaction unit and then enters the water recovery unit;

[0050] The control unit is a conventional control unit, which is used to control the normal operation and coordination of each unit.

[0051] Furthermore, the oxidizing agent and acid-base dosing unit includes a storage tank and a metering pump;

[0052] The mixing unit includes a pipeline mixer and a water inlet pump;

[0053] The oxidizing agent and acid and alkali in the storage tank are pumped into the pipeline mixer through the metering pump, and the wastewater to be degraded is pumped into the pipeline mixer through the inlet pump;

[0054] The ozone aeration and dosing unit includes an ozone generator and a multiphase flow pump; the ozone generated by the ozone generator is pumped into the first reaction tank of the advanced oxidation in-situ reaction unit through the multiphase flow pump;

[0055] The produced water recovery unit includes a produced water tank and a tail gas destruction component; the degraded wastewater is collected in the produced water tank; and the unreacted ozone is processed and discharged through the tail gas destruction component.

[0056] Furthermore, the diameter of the water permeable holes on the water permeable shell is 0.01mm-1mm, and the porosity is 10%-50%;

[0057] The multiphase flow pump pumps ozone into the first reaction tank of the advanced oxidation in-situ reaction unit, maintaining its flow rate within the range of 10 L / min-300 L / min, ensuring that the multifunctional adsorption catalyst in the first reaction tank is in a suspended fluidized state and fully contacts with the wastewater to be degraded;

[0058] The oxidizing agent is hypochlorite, permanganate, perchlorate, persulfate, percarbonate or potassium ferrate, and the dosage thereof is 10 mg / L-1000 mg / L;

[0059] The base in the acid and base is sodium hydroxide, and the acid is hydrochloric acid or sulfuric acid. After pH adjustment, the pH in the reaction tank is between 3-10, preferably between 3-7;

[0060] The filling amount of the multifunctional adsorption catalyst is 30%-70% of the volume of the cavity between the outer layer and the inner layer of the tank.

[0061] Furthermore, the wastewater to be degraded has a COD of 200 mg / L-1500 mg / L, a TDS of 50 g / L-200 g / L, and a pH of 7-10;

[0062] The method for using the above-mentioned COD degradation device is special in that it comprises the following steps:

[0063] S1. The wastewater to be degraded enters the pipeline mixer through the water inlet pump. The oxidizing agent and acid and alkali are pumped from the storage tank into the pipeline mixer by a metering pump and mixed thoroughly and evenly with the wastewater to be degraded. The oxidizing agent and acid and alkali are then fed into the first reactor tank of the advanced oxidation in-situ reaction unit through the water inlet pipe.

[0064] S2. After the wastewater to be degraded, which is mixed with an oxidizing agent and an acid and base, enters the first reaction tank through the permeable holes in the permeable shell and enters the cavity between the outer and inner layers of the tank. Simultaneously, ozone generated by the ozone generator is pumped into the bottom of the first reaction tank via a multiphase flow pump and enters the cavity between the outer and inner layers of the tank, causing the multifunctional adsorption catalyst to be suspended and fluidized. The wastewater to be degraded fully contacts the multifunctional adsorption catalyst and ozone, undergoing in-situ degradation. The wastewater treated in the first reaction tank (including any residual ozone therein) is then sequentially degraded in subsequent reaction tanks. The reaction time in the advanced oxidation in-situ reaction unit is 10-60 minutes.

[0065] S3. After the degradation is completed, the degradation water enters the water production tank through the outlet pipe of the last reaction tank, and the unreacted ozone is degraded by the tail gas destruction component and then discharged.

[0066] Concept and principle of the present invention:

[0067] In view of the current situation in which the COD degradation efficiency of mine brine is low, the catalyst cost is high, and the investment and floor space of the degradation equipment are large in the existing technology, the present invention combines multifunctional adsorption catalytic reaction and multi-stage advanced oxidation technology through a multi-stage "adsorption + catalytic in situ degradation". Among them, the multifunctional adsorption catalytic reaction can efficiently adsorb COD substances, prolong the time of multifunctional advanced oxidation catalytic degradation of COD, reduce the footprint of the entire degradation device, and reduce engineering investment costs; an oxidizing agent is added to the treated influent through a pipeline mixer to fully mix the influent and the oxidizing agent, and ozone is introduced into the bottom of the reaction tank through a multiphase flow pump. The wastewater enters the cavity of the reaction tank filled with a multifunctional adsorption catalyst, and the COD in the wastewater is adsorbed by the multifunctional adsorption catalyst. The adsorbed COD is catalytically degraded in situ by the oxidizing agent and ozone. The treated wastewater enters the subsequent multiple reaction tanks in turn to re-adsorb and degrade the undegraded small molecule COD, thereby ensuring the degradation efficiency of COD. At the same time, the multifunctional adsorption catalyst used uses coal gangue, gasification slag, and fly ash solid waste as raw materials, which reduces the cost of catalyst preparation. The entire device uses cylindrical tubular reaction tanks in series, which greatly reduces the footprint and investment of the entire reaction device.

[0068] Advantages of the present invention:

[0069] 1. The raw materials for the multifunctional adsorption catalyst prepared by the present invention are coal gangue, gasification slag and fly ash, all of which are solid wastes. No external chemical reagents and raw materials are added, which is innovative in resource recycling. In addition, the multifunctional adsorption catalyst prepared by the present invention has the functions of both adsorption and catalytic degradation of COD. The porous adsorption and aluminate adsorption properties of coal gangue, gasification slag and fly ash are utilized to increase the specific surface area and porosity of the coal gangue, gasification slag and fly ash through simple grinding and acid-base pretreatment, thereby improving the adsorption performance. The carbon and iron oxide inherent in the coal gangue, gasification slag and fly ash are used to carry out in situ redox reactions to prepare multivalent and multi-scale catalyst materials without the need for external catalyst raw materials and complex preparation processes.

[0070] 2. Nano-iron, ferric oxide and ferrous oxide exist on the surface and in the pores of the multifunctional adsorption catalyst prepared by the present invention, which releases ferrous ions to in-situ catalyze the oxidation agent and ozone degradation of organic matter. Coal gangue, gasified slag and fly ash serve as ferrous ion catalyst carriers and have a complexing effect. They can continuously release a certain amount of ferrous ions, maintain catalytic degradation activity, prevent a large amount of iron ions from consuming the oxidant, and reduce the output of iron sludge.

[0071] 3. The COD degradation device of the present invention comprises an advanced oxidation in-situ reaction unit, an ozone aeration dosing unit, an oxidant and acid / base dosing unit, a mixing unit, a water recovery unit, and a control unit. After the COD components are fully mixed with the oxidant, they enter the reaction tank and are adsorbed by a multifunctional adsorption catalyst. On the multifunctional adsorption catalyst, OH· and SO4 generated by the oxidant and ozone catalysis are .- The multifunctional adsorption catalyst has the functions of adsorption and catalytic oxidation. Nano-iron, iron ions, ozone, and oxidizing agents (such as persulfate) catalyze multifunctional catalytic reactions on the surface of the catalyst material. At the same time, nano-iron has the characteristics of high catalytic activity, many active sites and large contact area, and can efficiently and fully degrade the adsorbed COD. The adsorption and oxidation processes are carried out simultaneously. The entire process has the advantages of long COD residence time, high degradation efficiency, and multi-stage oxidation. It is suitable for high-salinity wastewater and ordinary wastewater, with high treatment rate and good effect, and is suitable for promotion and use.

[0072] 4. The COD degradation device of the present invention adopts a pre-oxidation-multi-stage series deep oxidation design, and degrades COD through a pre-oxidation-multi-stage series in-situ reaction. The oxidant is fully mixed with the influent water through a pipeline mixer at the water inlet end. Ozone is only added at the bottom of the first reaction tank of the advanced oxidation in-situ reaction unit. In the subsequent reaction tanks, the unreacted ozone and oxidant can be fully utilized. A cylindrical tubular reaction tank is used. When the ozone gas is introduced, the ozone flow rate is adjusted according to the filling amount of the multifunctional adsorption catalyst, so that the entire multifunctional adsorption catalyst is in a suspended fluidized state in the tank body, so that the solid, liquid and gas three phases are fully contacted, the oxidation efficiency is improved, and the occurrence of catalyst fouling is reduced. The entire device has the characteristics of uniform water output, no dead angle in the oxidation reaction, sufficient oxidation reaction, compact equipment, small footprint, small catalyst loss, simple replacement of consumables, small amount of ozone and oxidant addition, and high utilization efficiency.

[0073] 5. The present invention couples a nano-adsorption process (specifically the catalytic portion of a multifunctional adsorption catalyst) in situ with a multifunctional advanced oxidation process. The multifunctional adsorption catalyst has the advantages of a large specific surface area, good adsorption effect, no need for frequent regeneration, a long service life, and easy replacement. Adsorption, ozone catalysis, and oxidant catalysis occur in situ on the surface of the catalyst material, resulting in high adsorption efficiency, long oxidation time, high oxidation efficiency, and multifunctional oxidation. The multifunctional adsorption catalyst has the advantages of strong chemical corrosion resistance, multiple reaction sites, high catalytic activity, no need for external energy, low cost, strong durability, and good effect. Catalyst loss is low, no residual metal ions are produced in the water, and the impact on subsequent treatment processes is minimal.

[0074] 6. The multifunctional adsorption catalyst prepared by the present invention utilizes solid waste (gangue, gasification slag, fly ash) as raw materials, not only fully reusing the solid waste but also utilizing the inherent iron oxides in the solid waste to generate the catalytic component in situ. The multifunctional adsorption catalyst preparation process first involves soaking the raw materials in oxalic acid to remove calcium carbonate, unblocking pores, and reacting with the iron oxides to form ferrous oxalate. Then, an inorganic alkaline solution is used to leach silica and aluminum oxide, unblocking pores and improving the adsorption properties of the solid waste. This also exposes the iron oxide contained in the raw materials, providing sites for subsequent reduction and modification. Finally, a high-temperature in-situ reduction reaction is carried out under the protection of an inert gas. The residual carbon in the raw materials is used to further reduce the ferrous oxide produced by the decomposition of the ferrous oxalate and the iron oxide exposed on the raw material surface, generating nano-iron. This nano-iron is then adsorbed on the raw material surface in situ, where it collaborates with the unreduced iron oxide and ferrous oxide to provide catalytic function. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 This is a SEM image of the multifunctional adsorption catalyst prepared in Example 2;

[0076] Figure 2 The schematic diagram of the COD degradation device of the present invention is shown in FIG.

[0077] 1-water inlet pump, 2-pipeline mixer, 3-storage tank, 4-metering pump, 5-water inlet pipe, 6-water permeable shell, 7-outer shell, 8-ozone generator, 9-multiphase flow pump, 10-water outlet pipe, 11-multifunctional adsorption catalyst, 12-exhaust gas destruction component, 13-water production tank;

[0078] Figure 3 A comparison chart of the catalytic effects of different catalyst combinations. DETAILED DESCRIPTION

[0079] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments:

[0080] 1. Multifunctional adsorption catalyst

[0081] The multifunctional adsorption catalyst includes a carrier part and a catalytic part, and the overall structure is planetary. The carrier part is a spherical, flaky or irregularly shaped porous structure with a size of 1mm-50mm, a pore size of 1nm-1000nm, and a porosity of 10%-80%. The catalytic part is attached to the surface or pore size of the carrier part, and the particle size is 1nm-100nm.

[0082] The preparation method for the multifunctional adsorption catalyst involves first activating the carrier with acid to remove impurities, then neutralizing it with alkali. The catalytic component (derived from coal gangue, gasified slag, and fly ash) is then attached to the carrier surface and pores through oxygen-free sintering. The multifunctional adsorption catalyst simultaneously activates ozone and oxidizing agents, improving the efficiency of COD removal through oxidation. Specifically, the following steps are involved:

[0083] 1) Preprocessing

[0084] The dried and cooled coal gangue and / or gasified slag are ground to a particle size of 0.3 mm to 3 mm and placed in a dryer for later use; wherein the mass fraction of iron oxide in the coal gangue and the gasified slag is 1% to 10%, the mass fraction of aluminum oxide is 10% to 40%, the mass fraction of silicon dioxide is 30% to 50%, the mass fraction of carbon is 3% to 20%, and the remainder is doped inorganic elements such as K, P, Ba, and S; the drying temperature is 80° C. to 120° C., the drying time is 0.5 h to 2 h, and the coal gangue and / or gasified slag is placed in a high-energy ball mill for grinding, the high-energy ball mill speed is 500 r / min to 1000 r / min, and the ball milling time is 0.5 h to 2 h;

[0085] Fly ash with a dried particle size of 10 μm to 50 μm is placed in a dryer for later use; the fly ash contains 3% to 10% by mass of iron oxide, 10% to 30% by mass of aluminum oxide, 30% to 50% by mass of silicon dioxide, 1% to 10% by mass of unburned carbon, and the remainder is doped inorganic elements such as K, P, Ba, and S; the fly ash is dried at a temperature of 80°C to 120°C for a drying time of 0.5h to 2h; the fly ash can be fluidized bed fly ash collected from power plants;

[0086] 2) Activation

[0087] 2.1) The fly ash pretreated in step 1) and coal gangue / or gasified slag are weighed in a mass ratio of 1:1-3:1, and water is added and stirred to form a first slurry of 10 wt%-60 wt%;

[0088] 2.2) adding oxalic acid to the first slurry prepared in step 2.1), followed by heating and stirring to react, and spray drying the product after completion of the reaction to obtain a first composite material; wherein the molar concentration of oxalic acid after being added to the first slurry is 0.1 mol / L-1 mol / L; the reaction temperature is 60°C-80°C, the reaction time is 0.5 h-2 h, the stirring speed is 500 r / min-2000 r / min; the drying temperature is 150°C-300°C, and the pressure is 0.1 MPa-1 MPa;

[0089] 3) Alkali leaching

[0090] The first composite material obtained in step 2) is mixed with water to form a second slurry with a concentration of 10 wt% to 60 wt%, and a sodium hydroxide solution is added to the second slurry to adjust the pH of the second slurry to 10-12, followed by heating and stirring to react, and after the reaction is completed, the product is spray-dried to obtain a second composite material; wherein, after the addition of the second slurry, the molar concentration of sodium hydroxide is 0.1 mol / L to 3 mol / L; the reaction temperature is 60° C. to 80° C., the reaction time is 0.5 h to 2 h, the stirring speed is 500 r / min to 2000 r / min; the drying temperature is 150° C. to 300° C., and the pressure is 0.1 MPa to 1 MPa;

[0091] 4) Sintering

[0092] The second composite material obtained in step 3) is placed in a high-temperature tube furnace and sintered in a nitrogen atmosphere with a circulation flow rate of 10 L / min-30 L / min to obtain a multifunctional adsorption catalyst. The sintering process includes:

[0093] The first stage: the temperature is 600℃-800℃, the time is 1h-2h, and mixed particles are obtained;

[0094] The second stage: the temperature is 1100℃-1300℃, the time is 1h-2h, so that the mixed particles are bonded;

[0095] The rotation speed of the above-mentioned high-temperature tube furnace is 50r / min-200r / min, and the heating rate is 5℃ / min-15℃ / min; the first stage of sintering is to use coal gangue, gasification slag and residual carbon in fly ash as reducing agents for thermal reduction reaction; the second stage of sintering is to use silicates and aluminates in coal gangue, gasification slag and fly ash as binders to prepare a multifunctional adsorption catalyst with a certain particle size (the carrier part size is 1mm-50mm, and the catalytic part particle size is 1nm-100nm) with a planetary structure, wherein the pore size of the carrier part is 1nm-1000nm and the porosity is 10%-80%; the multifunctional adsorption catalyst is a composite material containing nano-iron and multivalent states of iron oxide and ferrous oxide, which is stored in a dryer after cooling for future use.

[0096] Example 1

[0097] 1) Preprocessing

[0098] The dried and cooled coal gangue is ground to a particle size of 0.3 mm and placed in a dryer for later use; wherein the mass fraction of iron oxide in the coal gangue is 1%, the mass fraction of aluminum oxide is 40%, the mass fraction of silicon dioxide is 30%, the mass fraction of carbon is 20%, and the balance is doped inorganic elements such as K, P, Ba, and S; the drying temperature is 80°C, the drying time is 0.5 h, and the coal gangue is placed in a high-energy ball mill for grinding, the high-energy ball mill speed is 500 r / min, and the ball milling time is 0.5 h;

[0099] Dried fly ash with a particle size of 10 μm is placed in a dryer for later use; the fly ash contains 3% by mass of iron oxide, 30% by mass of aluminum oxide, 30% by mass of silicon dioxide, 10% by mass of unburned carbon, and the remainder is doped inorganic elements such as K, P, Ba, and S; the fly ash is dried at a temperature of 80°C for 0.5 h; the fly ash can be fluidized bed fly ash collected from power plants;

[0100] 2) Activation

[0101] 2.1) The fly ash and coal gangue pretreated in step 1) were weighed in a mass ratio of 1:1, and water was added and stirred to form a 10 wt% first slurry;

[0102] 2.2) adding oxalic acid to the first slurry prepared in step 2.1), followed by heating and stirring to react, and spray drying the product after completion of the reaction to obtain a first composite material; wherein the oxalic acid has a molar concentration of 0.1 mol / L after being added to the first slurry; the reaction temperature is 60°C, the reaction time is 0.5 h, the stirring speed is 500 r / min, and the drying temperature is 150°C, and the pressure is 0.1 MPa;

[0103] 3) Alkali leaching

[0104] The first composite material obtained in step 2) is mixed with water to form a 10wt% second slurry, and a sodium hydroxide solution is added to the second slurry, and the pH of the second slurry is adjusted to 10, followed by heating and stirring to react. After the reaction is completed, the product is spray-dried to obtain a second composite material; wherein, after the second slurry is added, the molar concentration of sodium hydroxide is 0.1 mol / L; the reaction temperature is 60°C, the reaction time is 0.5 h, the stirring speed is 500 r / min; the drying temperature is 150°C, and the pressure is 0.1 MPa;

[0105] 4) Sintering

[0106] The second composite material obtained in step 3) is placed in a high-temperature tube furnace and sintered in a nitrogen atmosphere with a circulation flow rate of 10 L / min to obtain a multifunctional adsorption catalyst. The sintering process includes:

[0107] The first stage: temperature is 600℃, time is 1h, and mixed particles are obtained;

[0108] The second stage: the temperature is 1100℃ and the time is 1h to make the mixed particles bond;

[0109] The rotation speed of the high-temperature tubular furnace is 50 r / min, and the heating rate is 5°C / min; the first stage of sintering is to use the residual carbon in coal gangue and fly ash as a reducing agent for a thermal reduction reaction; the second stage of sintering is to use the silicates and aluminates in the coal gangue and fly ash as binders to prepare a multifunctional adsorption catalyst with a certain particle size (the carrier part size is 1 mm, and the catalytic part particle size is 1 nm) with a planetary structure; the multifunctional adsorption catalyst is a composite material containing nano-iron and multivalent states of iron oxide and ferrous oxide, and is stored in a dryer after cooling for future use.

[0110] Example 2

[0111] 1) Preprocessing

[0112] The dried and cooled coal gangue is ground to a particle size of 3 mm and placed in a dryer for later use; the mass fraction of iron oxide in the coal gangue is 10%, the mass fraction of aluminum oxide is 10%, the mass fraction of silicon dioxide is 50%, the mass fraction of carbon is 3%, and the balance is doped inorganic elements such as K, P, Ba, and S; the drying temperature is 120°C, the drying time is 2 hours, and the coal gangue is placed in a high-energy ball mill for grinding at a high-energy ball mill speed of 1000 r / min and the ball milling time is 2 hours;

[0113] Dried fly ash with a particle size of 50 μm is placed in a dryer for later use; the fly ash contains 10% by mass of iron oxide, 10% by mass of aluminum oxide, 50% by mass of silicon dioxide, 1% by mass of unburned carbon, and the remainder is doped inorganic elements such as K, P, Ba, and S; the fly ash is dried at a temperature of 120°C for 2 hours; the fly ash can be fluidized bed fly ash collected from power plants;

[0114] 2) Activation

[0115] 2.1) Weigh the fly ash pretreated in step 1) and raw material 1 in a mass ratio of 1:1, add water and stir evenly to form a 60 wt% first slurry;

[0116] 2.2) Adding oxalic acid to the first slurry prepared in step 2.1), followed by heating and stirring to react, and spray drying the product after completion of the reaction to obtain a first composite material; wherein, after the addition of oxalic acid, the concentration of oxalic acid in the slurry is 1 mol / L; the reaction temperature is 80°C, the reaction time is 2 h, the stirring speed is 1000 rpm, and the drying temperature is 300°C, and the pressure is 1 MPa;

[0117] 3) Alkali leaching

[0118] The first composite material obtained in step 2) is mixed with water to form a 60wt% second slurry, and a sodium hydroxide solution is added to the second slurry, and the pH of the second slurry is adjusted to 12, followed by heating and stirring to react. After the reaction is completed, the product is spray-dried to obtain a second composite material; wherein, after the addition of the second slurry, the molar concentration of sodium hydroxide is 3 mol / L; the reaction temperature is 80°C, the reaction time is 2 h, the stirring speed is 2000 r / min; the drying temperature is 300°C, and the pressure is 1 MPa;

[0119] 4) Sintering

[0120] The second composite material obtained in step 3) is placed in a high-temperature tube furnace and sintered in a nitrogen atmosphere with a circulation flow rate of 30 L / min to obtain a multifunctional adsorption catalyst. The sintering process includes:

[0121] The first stage: temperature is 800℃, time is 2h, and mixed particles are obtained;

[0122] The second stage: the temperature is 1300℃ and the time is 2h to make the mixed particles bond;

[0123] The rotation speed of the high-temperature tube furnace is 200 r / min, and the heating rate is 15°C / min; the first stage of sintering is to use the residual carbon in coal gangue and fly ash as a reducing agent for a thermal reduction reaction; the second stage of sintering is to use the silicates and aluminates in the coal gangue and fly ash as binders to prepare a multifunctional adsorption catalyst with a certain particle size (the carrier part size is 3 mm, and the catalytic part particle size is 100 nm) with a planetary structure; the multifunctional adsorption catalyst is a composite material containing nano-iron and multivalent states of iron oxide and ferrous oxide, which is stored in a dryer after cooling for future use.

[0124] Example 3

[0125] 1) Preprocessing

[0126] The dried and cooled raw material 1 (a mixture of coal gangue and gasified slag) was ground to a particle size of 2 mm and placed in a desiccator for later use; the raw material 1 had a mass fraction of 5% iron oxide, 20% aluminum oxide, 40% silicon dioxide, and 8% carbon, with the remainder being doped inorganic elements such as K, P, Ba, and S; the drying temperature was 100°C, the drying time was 1.5 hours, and the raw material 1 was placed in a high-energy ball mill for grinding at a speed of 800 r / min and a ball milling time of 1.5 hours;

[0127] Dried fly ash with a particle size of 30 μm is placed in a dryer for later use; the fly ash contains 5% by mass of iron oxide, 20% by mass of aluminum oxide, 40% by mass of silicon dioxide, 3% by mass of unburned carbon, and the remainder is doped inorganic elements such as K, P, Ba, and S; the fly ash is dried at a temperature of 100°C for 1.5 hours; the fly ash can be fluidized bed fly ash collected from power plants;

[0128] 2) Activation

[0129] 2.1) The fly ash pretreated in step 1) and raw material 1 were weighed in a mass ratio of 2:1, and water was added and stirred to form a 50 wt% first slurry;

[0130] 2.2) Adding oxalic acid to the first slurry prepared in step 2.1), followed by heating and stirring to react, and spray drying the product after completion of the reaction to obtain a first composite material; wherein the molar concentration of oxalic acid after being added to the first slurry is 0.6 mol / L; the reaction temperature is 70°C, the reaction time is 1.5 hours, the stirring speed is 1500 r / min, and the drying temperature is 200°C, and the pressure is 0.6 MPa;

[0131] 3) Alkali leaching

[0132] The first composite material obtained in step 2) is mixed with water to form a 30wt% second slurry, and a sodium hydroxide solution is added to the second slurry, and the pH of the second slurry is adjusted to 11.5, followed by heating and stirring to react. After the reaction is completed, the product is spray-dried to obtain a second composite material; wherein, after the addition of the second slurry, the molar concentration of sodium hydroxide is 2.5 mol / L; the reaction temperature is 70°C, the reaction time is 1.5 h, the stirring speed is 1000 r / min; the drying temperature is 200°C, and the pressure is 0.6 MPa;

[0133] 4) Sintering

[0134] The second composite material obtained in step 3) is placed in a high-temperature tube furnace and sintered in a nitrogen atmosphere with a circulation flow rate of 20 L / min to obtain a multifunctional adsorption catalyst. The sintering process includes:

[0135] The first stage: temperature is 700℃, time is 1.5h, and mixed particles are obtained;

[0136] The second stage: the temperature is 1200℃ and the time is 1.5h to make the mixed particles bond;

[0137] The high-temperature tube furnace rotates at a speed of 150 r / min and a heating rate of 10°C / min. The first-stage sintering utilizes raw material 1 and residual carbon in fly ash as reducing agents for a thermal reduction reaction. The second-stage sintering utilizes raw material 1 and silicates and aluminates in fly ash as binders to prepare a multifunctional adsorption catalyst having a planetary structure and a certain particle size (the carrier part size is 2.6 mm, and the catalytic part particle size is 10 nm). The multifunctional adsorption catalyst is a composite material comprising nano-iron and multivalent states of iron oxide and ferrous oxide, and is stored in a dryer after cooling for future use.

[0138] Figure 1This is a SEM photograph of the multifunctional adsorption catalyst prepared in Example 2. As can be seen from the figure, the multifunctional adsorption catalyst primarily comprises a support portion and a catalytic portion. The support portion is spherical with a millimeter-scale particle size, and the nanoscale catalytic portion is well supported on the surface and within the pores of the support portion. Table 1 shows the XRF characterization analysis of the gangue-fly ash support material used in Example 2 (not sintered in step 4) and the resulting multifunctional adsorption catalyst. As can be seen from the table, compared to the gangue-fly ash support material, the multifunctional adsorption catalyst prepared using the above method of the present invention has a significantly increased content of the catalytic element Fe. This is primarily due to the exposure of the iron contained in the mixture after acid-base treatment and reduction, forming iron oxide, ferrous oxide, and nano-iron, which increases the proportion of iron and, in turn, the number of catalyst active sites.

[0139] Table 1 XRF analysis of multifunctional adsorption catalyst materials

[0140]

[0141] 2. Device for efficient degradation of COD in mine brine

[0142] like Figure 2 As shown, the device includes an advanced oxidation in-situ reaction unit, an ozone aeration dosing unit, an oxidizing agent and acid and alkali dosing unit, a mixing unit, a water production recovery unit and a control unit.

[0143] In this embodiment, the advanced oxidation in-situ reaction unit includes three reaction tanks connected in series along the water flow direction, namely the primary reaction tank, the secondary reaction tank and the tertiary reaction tank. The tank body of each reaction tank is a cylindrical double-layer hollow structure; the outer layer has a diameter of 100mm-1000mm and a thickness of 1mm-100mm, which is the shell of the reaction tank; the inner layer has a diameter of 50mm- 500mm, thickness 1mm-10mm, which is a water-permeable shell; the cavity between the outer layer and the inner layer is filled with the multifunctional adsorption catalyst developed by the present invention, and the filling amount is 30%-70% of the volume of the cavity between the outer layer and the inner layer of the tank; a number of water-permeable holes are evenly arranged on the water-permeable shell, the aperture of the water-permeable hole is 0.01mm-1mm, and the porosity is 10%-50%; both ends of the reaction tank body are closed, and a water inlet pipe and a water outlet pipe are coaxially arranged respectively, wherein the water inlet pipe is coaxially arranged with the tank body, and its pipe diameter is smaller than the aperture of the water-permeable shell, and the water outlet pipe is arranged at the end of the tank body corresponding to the cavity between the outer layer and the inner layer, and when in use, the water inlet flow rate is greater than the water outlet flow rate, ensuring that the incoming water can enter the cavity through the water-permeable hole and stay, fully contact with the multifunctional adsorption catalyst, and improve the catalytic efficiency; the reaction tank is made of 2205 duplex stainless steel as a whole, of course, polymer materials can also be used. The three reaction tanks are arranged in series, the water outlet pipe of the primary reaction tank is connected to the water inlet pipe of the secondary reaction tank, and the water outlet pipe of the secondary reaction tank is connected to the water inlet pipe of the tertiary reaction tank. The water inlet pipes of the primary reaction tank and the tertiary reaction tank are located at the top of the tank body, and the water inlet tank of the secondary reaction tank is located at the bottom of the tank body. In this way, even if the COD is not degraded in the primary reaction tank, it can be fully degraded in the secondary reaction tank.

[0144] The oxidant and acid and alkali dosing unit includes a storage tank, a metering pump, and related valves and pipes. The storage tank (can also be a box) is used to store a certain amount of oxidant and acid and alkali, and is made of plastic materials such as PP, PVC, PE, etc., with a volume of 1m 3 -5m 3 The metering pump is a diaphragm metering pump made of UPVC with a flow rate of 10L / h-200L / h. The dosage is adjusted according to the influent water quality and COD content, and the oxidizing agent and acid and alkali are added through the relevant valves and pipelines. The oxidizing agent is hypochlorite, permanganate, perchlorate, persulfate, percarbonate, or potassium ferrate, and the dosage is 10mg / L-1000mg / L. The alkali in the acid and alkali is sodium hydroxide, and the acid is hydrochloric acid or sulfuric acid. After pH adjustment, the pH in the reaction tank is between 3-10, preferably between 3-7.

[0145] The mixing unit includes a pipeline mixer and an inlet pump. The pipeline mixer is a three-way pipeline mixer that allows the incoming water to be evenly mixed with the oxidant and acid and alkali. It is made of carbon steel, lined with rubber, and has a diameter of 50 mm to 500 mm. Incoming water is introduced into the pipeline mixer through the inlet pump, where it is thoroughly and uniformly mixed with the oxidant and acid and alkali. It then enters the primary reaction tank through the inlet pipe. The water flows through the permeable holes of the inner permeable shell into the cavity between the outer and inner layers. The COD components in the water are adsorbed by the multifunctional adsorption catalyst and catalytically oxidized and degraded. The produced water then enters the secondary and tertiary reaction tanks in sequence, and after further oxidation, enters the produced water recovery unit.

[0146] The ozone aeration unit includes an ozone generator, a multiphase flow pump, and a gas-liquid stabilization tank. Ozone is generated by the ozone generator and then introduced into the bottom of the primary reaction tank via the multiphase flow pump, where it enters the reaction tank to participate in the oxidation reaction. The ozone generator produces 10kg / h-50kg / h of ozone at a concentration of 100mg / L-210mg / L. The multiphase flow pump is made of duplex steel and has a flow rate of 10L / min-300L / min. The ozone flow rate can be adjusted to keep the multifunctional adsorption catalyst in the reaction tank in a suspended and fluidized state.

[0147] The water recovery unit includes a water tank and a tail gas destruction component. The water produced after being treated by the advanced oxidation in-situ reaction unit enters the water tank, and the unreacted ozone contained in the water is degraded and discharged through the tail gas destruction component. The water tank has a capacity of 1m 3 -100m 3 The water tank is made of PP, PVC, PE or FRP; the exhaust gas destruction components include demister, demister, destruction tower, catalyst, induced draft fan, etc., which are existing equipment.

[0148] The control unit is used to control the normal operation and coordination of each unit.

[0149] The method for using the above-mentioned device for efficiently degrading COD in mine brine is as follows:

[0150] S1. The wastewater to be degraded enters the pipeline mixer through the water inlet pump, and the oxidizing agent and acid and alkali are pumped from the storage tank into the pipeline mixer through the metering pump to be fully and homogeneously mixed with the wastewater to be degraded, and then enter the reaction tank through the water inlet pipe of the advanced oxidation in situ reaction unit primary reaction tank;

[0151] S2. The wastewater to be degraded, mixed with oxidizing agents and acid and alkali, enters the primary reaction tank and enters the cavity between the outer and inner layers of the tank through the permeable holes on the permeable shell. At the same time, ozone generated by the ozone generator is pumped into the bottom of the primary reaction tank through a multiphase flow pump and enters the cavity between the outer and inner layers of the tank, placing the multifunctional adsorption catalyst in a suspended fluidized state. The wastewater to be degraded fully contacts the multifunctional adsorption catalyst and ozone, undergoing in-situ degradation (in this process, the COD components in the wastewater are adsorbed by the multifunctional adsorption catalyst, and the adsorbed COD components are catalyzed by the oxidizing agents and ozone to generate hydroxyl radicals OH· and sulfate radicals SO4 ·- The wastewater treated in the primary reactor is then further degraded in the secondary and tertiary reactors (the unremoved COD is further adsorbed by the multifunctional adsorption catalyst in the secondary and tertiary reactors, and the unreacted oxidant and ozone degrade the COD components). The entire reaction time is 10-60 minutes.

[0152] S3. After the degradation is completed, the degradation water enters the water production tank through the outlet pipe of the tertiary reaction tank. The unreacted ozone is degraded by the tail gas destruction component and then discharged, which will not damage the atmospheric environment.

[0153] Example 4

[0154] 100L of secondary reverse osmosis brine with TDS of 52618mg / L and COD of 456mg / L from mine water is pumped into pipeline mixer 2 through inlet pump 1. 5mmol / L Na2S2O8 solution is added into pipeline mixer 2 through metering pump 4 at a dosage of 50L / h. In pipeline mixer 2, Na2S2O8 solution is fully mixed with influent water. The mixed solution enters the primary reaction tank through inlet pipe 5. The COD component in the influent water is adsorbed by the multifunctional adsorption catalyst. The influent water passes through the permeable The permeable holes in shell 6 lead into the cavity between the outer and inner layers. 148 mg / L of ozone is generated by ozone generator 8 and then introduced into the bottom of the primary reaction tank via multiphase flow pump 9. The ozone then enters the tank to participate in the oxidation reaction. The adsorbed COD components are catalytically oxidized by ozone and the oxidizing agent before entering the subsequent reaction tanks through the primary reaction tank outlet pipe 10. After three stages of reaction (a total of 10 minutes), the produced water enters the produced water tank 13. The remaining exhaust gas is treated by the exhaust gas destruction component 12 and then discharged. Testing showed that the COD content in the produced water was 113 mg / L, with a COD removal rate of 75.2%.

[0155] Example 5

[0156] 100 L of secondary reverse osmosis brine from mine water with a TDS of 53176 mg / L and a COD of 528 mg / L was pumped into pipeline mixer 2 via inlet pump 1. A 6 mmol / L NaClO₄ solution was added to pipeline mixer 2 at a dosage of 80 L / h via metering pump 4. In pipeline mixer 2, the NaClO₄ solution and influent were thoroughly mixed. The mixed solution then entered the primary reaction tank via inlet pipe 5. The COD component in the influent was adsorbed by a multifunctional adsorption catalyst. The influent then entered the cavity between the outer and inner layers through the permeable holes of permeable shell 6. 130 mg / L of ozone was generated by ozone generator 8 and then introduced into the bottom of the primary reaction tank via multiphase flow pump 9. The ozone then entered the reaction tank to participate in the oxidation reaction. After catalytic oxidation by ozone and the oxidizing agent, the ozone was transported to the subsequent reaction tank via outlet pipe 10 of the primary reaction tank. After the tertiary reaction (a total of 30 minutes), the produced water entered the produced water tank 13. The remaining exhaust gas was treated by exhaust gas destruction component 12 and discharged. Through testing, the COD in the produced water was 127.5 mg / L and the removal rate was 75.9%.

[0157] Example 6

[0158] 100L Secondary reverse osmosis brine from mine water with a TDS of 61,689 mg / L and a COD of 696 mg / L is pumped into pipeline mixer 2 via inlet pump 1. A 10 mmol / L KMnO₄ solution is added to pipeline mixer 2 at a dosage of 52 L / h via metering pump 4. In pipeline mixer 2, the KMnO₄ solution and influent are thoroughly mixed. The mixed solution then enters the primary reaction tank via inlet pipe 5. The COD component in the influent is adsorbed by a multifunctional adsorption catalyst. The influent enters the cavity between the outer and inner layers through the permeable holes of permeable shell 6. 151 mg / L of ozone is generated by ozone generator 8 and then introduced into the bottom of the primary reaction tank via multiphase flow pump 9. The ozone enters the reaction tank and participates in the oxidation reaction. After catalytic oxidation by ozone and the oxidizing agent, the ozone enters the subsequent reaction tank via outlet pipe 10 of the primary reaction tank. After the tertiary reaction (a total of 60 minutes), the produced water enters the produced water tank 13. The remaining exhaust gas is treated by exhaust gas destruction component 12 and discharged. Through testing, the COD in the produced water is 139.2 mg / L, and the removal rate is 80%.

[0159] Example 7

[0160] 100L of secondary reverse osmosis brine with a TDS of 52618 mg / L and a COD of 820 mg / L from mine water was pumped into the pipeline mixer 2 through the inlet pump 1. 7 mmol / L Na2S2O8 solution was added to the pipeline mixer 2 at a dosage of 50L / h through the metering pump 4. In the pipeline mixer 2, the Na2S2O8 solution was fully mixed with the influent. The mixed solution entered the primary reaction tank through the inlet pipe 5. The COD component in the influent was adsorbed by the multifunctional adsorption catalyst. The influent entered the cavity between the outer layer and the inner layer through the permeable holes of the permeable shell 6. 150 Ozone at a concentration of 100 mg / L is generated by ozone generator 8 and then introduced into the bottom of the primary reaction tank via multiphase pump 9. The ozone then enters the tank to participate in the oxidation reaction. The adsorbed COD components undergo catalytic oxidation by ozone and oxidizing agents before entering the subsequent reaction tanks through the primary reaction tank outlet pipe 10. The effluent then re-enters the front-end water inlet for recycling. After 60 minutes of reaction, the produced water enters the produced water tank 13. The remaining exhaust gas is treated by exhaust gas destruction component 12 and then discharged. After 60 minutes, the produced water passed testing, with a COD content of 185 mg / L and a removal rate of 77.4%.

[0161] In order to verify the degradation effect of the present invention, the present invention and the existing process are also compared:

[0162] Comparative Example 1: Degradation was carried out using an ozone oxidation process, with other conditions being the same as those in Example 6.

[0163] Comparative Example 2: Degradation was carried out using a persulfate oxidation process, with other conditions being the same as those in Example 6.

[0164] Comparative Example 3: Degradation was carried out using an ozone + persulfate oxidation process, with other conditions being the same as those in Example 6.

[0165] The results are as follows Figure 3 As shown in the figure, it can be seen that after 60 minutes of reaction (in actual engineering and experiments, the reaction control time is about 60 minutes), the overall COD degradation tends to be stable. Compared with comparative examples 1-3, the COD degradation efficiency of Example 6 of the present invention can be as high as 80%.

[0166] In summary, the multifunctional adsorption catalyst, COD degradation device and method of the present invention can efficiently remove COD in a short time and have good application prospects.

[0167] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present invention, and these modifications or replacements should all be included in the scope of protection of the present invention.

Claims

1. A method for preparing a multifunctional adsorption catalyst, characterized in that: The following steps are involved: 1) Preprocessing Grinding the dried and cooled raw material 1 to a particle size of 0.3 mm to 3 mm for later use; the raw material 1 is one or a mixture of coal gangue and gasified slag; wherein the raw material 1 has a mass fraction of 1% to 10% of iron oxide, a mass fraction of 10% to 40% of aluminum oxide, a mass fraction of 30% to 50% of silicon dioxide, and a mass fraction of 3% to 20% of carbon; Fly ash with a dried particle size of 10 μm to 50 μm is reserved; wherein the mass fraction of iron oxide in the fly ash is 3% to 10%, the mass fraction of aluminum oxide is 10% to 30%, the mass fraction of silicon dioxide is 30% to 50%, and the mass fraction of unburned carbon is 1% to 10%; 2) Activation 2.1) Weigh the fly ash pretreated in step 1) and raw material 1 in a mass ratio of 1:1-3:1, add water and stir evenly to form a first slurry of 10wt%-60wt%; 2.2) adding oxalic acid to the first slurry prepared in step 2.1), followed by heating and stirring to react with the oxalic acid and iron oxides in the first raw material and the fly ash to produce ferrous oxalate. After the reaction is complete, the product is dried by spray drying to obtain a first composite material; 3) Alkali leaching The first composite material obtained in step 2) is mixed with water to form a second slurry with a concentration of 10 wt% to 60 wt%, and an inorganic alkali solution is added to the second slurry to adjust the pH value of the second slurry to 10-12. The slurry is then heated and stirred to react, thereby exposing the iron oxide contained in the raw material 1 and the fly ash to provide sites for subsequent reduction modification. After the reaction is completed, the product is dried by spray drying to obtain a second composite material. 4) Sintering The second composite material obtained in step 3) is placed in a circulating inert atmosphere and subjected to rotary sintering. The residual carbon in the raw material 1 and the fly ash is used to reduce the ferrous oxide produced by the decomposition of ferrous oxalate. At the same time, the exposed iron oxide is reduced to generate nano-iron that is directly adsorbed in situ on the surface of the fly ash and the raw material 1, thereby obtaining a multifunctional adsorption catalyst. The sintering process is specifically as follows: The first stage: sintering temperature is 600℃-800℃, and sintering time is 1h-2h; The second stage: the sintering temperature is 1100℃-1300℃, and the sintering time is 1h-2h.

2. The method for preparing the multifunctional adsorption catalyst according to claim 1, characterized in that: In step 1), the drying temperature of raw material 1 is 80°C-120°C, the drying time is 0.5h-2h, and raw material 1 is placed in a high-energy ball mill for grinding, the speed of the high-energy ball mill is 500r / min-1000r / min, and the ball milling time is 0.5h-2h; The drying temperature of fly ash is 80℃-120℃, and the drying time is 0.5h-2h; In step 2.2), after oxalic acid is added to the first slurry, its molar concentration is 0.1 mol / L-1 mol / L; the reaction temperature is 60°C-80°C, the reaction time is 0.5 h-2 h, and the stirring speed is 500 r / min-2000 r / min; the product is dried by spray drying at a temperature of 150°C-300°C and a pressure of 0.1 MPa-1 MPa; In step 3), after the inorganic alkali solution is added to the second slurry, its molar concentration is 0.1 mol / L-3 mol / L; the reaction temperature is 60°C-80°C, the reaction time is 0.5h-2h, and the stirring speed is 500r / min-2000r / min; the product is dried by spray drying at a temperature of 150°C-300°C and a pressure of 0.1Mpa-1Mpa; In step 4), the second composite material obtained in step 3) is placed in a high-temperature tube furnace and sintered in a nitrogen atmosphere with a circulation flow rate of 10 L / min-30 L / min; wherein the rotation speed of the high-temperature tube furnace is 50 r / min-200 r / min, and the heating rate is 5°C / min-15°C / min.

3. A multifunctional adsorption catalyst, characterized in that: Prepared by the preparation method according to any one of claims 1-2, comprising a carrier part and a catalytic part; The carrier part is a porous structure with a pore size of 1nm-1000nm; The catalytic part is attached to the surface or pores of the carrier part, and has a particle size of 1nm-100nm.

4. The multifunctional adsorption catalyst according to claim 3, characterized in that: The catalytic part is nano-iron, iron oxide and ferrous oxide.

5. Use of the multifunctional adsorption catalyst prepared by the preparation method according to any one of claims 1-2 in degrading COD in concentrated brine in mines.

6. A device for degrading COD, characterized by: It includes an advanced oxidation in-situ reaction unit, an ozone aeration dosing unit, an oxidant and acid-base dosing unit, a mixing unit, a water production recovery unit and a control unit; The advanced oxidation in-situ reaction unit includes a plurality of reaction tanks connected in series along the water flow direction; Each reaction tank has a double-layer hollow structure, wherein the outer layer is the outer shell of the reaction tank and the inner layer is a water-permeable shell. The cavity between the outer layer and the inner layer is filled with the multifunctional adsorption catalyst prepared by the preparation method according to any one of claims 1-2; the water-permeable shell is evenly provided with a plurality of water-permeable holes; and a water inlet pipe and a water outlet pipe are respectively provided at both ends of the tank body. The ozone aeration dosing unit adds ozone to the first reaction tank of the advanced oxidation in-situ reaction unit; the oxidant and acid-base dosing unit adds the oxidant and acid-base to the mixing unit, which are fully and evenly mixed with the wastewater to be degraded entering the mixing unit before entering the advanced oxidation in-situ reaction unit; The wastewater to be degraded is degraded in the advanced oxidation in-situ reaction unit and then enters the water recovery unit.

7. The device for degrading COD according to claim 6, characterized in that: The oxidizing agent and acid-base dosing unit includes a storage tank and a metering pump; The mixing unit includes a pipeline mixer and a water inlet pump; The oxidizing agent and acid and alkali in the storage tank are pumped into the pipeline mixer through the metering pump, and the wastewater to be degraded is pumped into the pipeline mixer through the water inlet pump; The ozone aeration and dosing unit includes an ozone generator and a multiphase flow pump; the ozone generated by the ozone generator is pumped into the first reaction tank of the advanced oxidation in-situ reaction unit through the multiphase flow pump; The produced water recovery unit includes a produced water tank and a tail gas destruction component; the degraded wastewater is collected in the produced water tank; and the unreacted ozone is processed and discharged through the tail gas destruction component.

8. The device for degrading COD according to claim 7, characterized in that: The diameter of the water permeable holes on the water permeable shell is 0.01mm-1mm, and the porosity is 10%-50%; The multiphase flow pump pumps ozone into the first reaction tank of the advanced oxidation in-situ reaction unit, maintaining its flow rate within the range of 10 L / min-300 L / min; The oxidizing agent is hypochlorite, permanganate, perchlorate, persulfate, percarbonate or potassium ferrate, and the dosage thereof is 10 mg / L-1000 mg / L; The base in the acid and base is sodium hydroxide, and the acid is hydrochloric acid or sulfuric acid. After pH adjustment, the pH in the reaction tank is between 3 and 10; The filling amount of the multifunctional adsorption catalyst is 30%-70% of the volume of the cavity between the outer layer and the inner layer of the tank.

9. The device for degrading COD according to claim 8, characterized in that: The COD of the wastewater to be degraded is 200mg / L-1500mg / L, TDS is 50g / L-200g / L, and pH is 7-10.

10. The method for using the COD degradation device according to claim 9, characterized in that: The following steps are involved: S1. The wastewater to be degraded enters the pipeline mixer through the water inlet pump. The oxidizing agent and acid and alkali are pumped from the storage tank into the pipeline mixer through the metering pump to be fully and evenly mixed with the wastewater to be degraded. The oxidizing agent and acid and alkali are then fed into the first reactor tank of the advanced oxidation in-situ reaction unit through the water inlet pipe. S2. The wastewater to be degraded, mixed with an oxidizing agent and an acid and base, enters the first reactor and flows through the permeable holes in the permeable shell into the cavity between the outer and inner layers of the reactor. Simultaneously, ozone generated by an ozone generator is pumped into the bottom of the first reactor by a multiphase flow pump and into the cavity between the outer and inner layers of the reactor, causing the multifunctional adsorption catalyst to be suspended and fluidized. The wastewater to be degraded fully contacts the multifunctional adsorption catalyst and ozone, undergoing in-situ degradation. The wastewater treated in the first reactor is then sequentially degraded in subsequent reactors. S3. After the degradation is completed, the degradation water enters the water production tank through the outlet pipe of the last reaction tank, and the unreacted ozone is degraded by the tail gas destruction component and then discharged.

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