A catalytic oxidation purification device and method for high-chlorine refractory wastewater

Abstract

The present invention belongs to the technical field of wastewater purification, and specifically relates to a catalytic oxidation purification device and method for high-chlorine refractory wastewater. The device includes a pH adjustment zone, a main reaction zone, a catalyst storage tank, a catalyst replenishing pipe, a pH correction flocculation zone, a catalyst recovery tank, and a catalyst reflux pipeline; the treatment method includes: in the pH adjustment zone, the water to be treated is acidic, hydrogen peroxide is added, the catalyst is mixed with the added hydrogen peroxide to react, the water quality is adjusted to be alkaline, the catalyst self-flocculates and recovers, the catalyst is separated from the treated water, and refluxed to the pH adjustment zone for reuse. The present invention effectively realizes the treatment of high-chlorine refractory wastewater, has the advantages of high removal efficiency, low operating cost, convenient management, etc., and has broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater purification, and specifically relates to a catalytic oxidation purification device and method for high-chlorine refractory wastewater, and more particularly to a catalytic oxidation purification method for pyridines (chloropyridine, pyridinic acid), nitroaromatics, halogenated organic pollutants, and anthraquinones under high chloride ion conditions. Background Art

[0002] Fenton oxidation technology is an important technology in the treatment of difficult-to-degrade industrial wastewater. It is generally believed that Fenton technology mainly removes difficult-to-degrade organic matter by catalyzing the production of hydroxyl radicals (·OH) to oxidize and mineralize it. When Fenton technology is used to treat high-chlorine difficult-to-degrade wastewater, due to the presence of chloride ions, most of the ·OH is converted into ·Cl, and ·Cl is then converted into dichloro anion radicals (·Cl 2 - ), ·Cl and ·Cl 2 - The oxidation capacity is lower than that of ·OH, which leads to the obstruction of the Fenton oxidation process and the difficulty of the oxidation mineralization process of organic matter. Through Fenton-like or other catalytic oxidation processes, increasing the pH of the reaction process or conducting the Fenton reaction process under neutral conditions is expected to reduce the amount of ·Cl generated, but the problem is that the oxidation capacity of ·OH is related to pH. The higher the pH, the lower the oxidation capacity of ·OH, resulting in unsatisfactory or even basically ineffective oxidation mineralization capacity for difficult-to-degrade organic matter. The inability to achieve good treatment of wastewater or the high cost of treatment directly restricts the improvement of enterprise production capacity and affects economic development. This requires us to find a method to increase the proportion of ·OH under acidic conditions during the treatment of high-chlorine wastewater.

[0003] OH+Cl - → ClOH - k = 4.2 × 10 9

[0004] ·ClOH - → OH+Cl - k = 6.0 × 10 9

[0005] ·ClOH - +H + → Cl+H 2 O k=2.4×10 10

[0006] ·Cl+Fe 2+ →Cl - +Fe 3+ k = 5.9 × 10 9

[0007] ·Cl+Cl -→ Cl 2 - k = 7.9 × 10 9

[0008] ·Cl 2 - +HO 2 →2Cl - +H + +O 2 k = 3.1 × 10 9

[0009] In addition, in the treatment of difficult-to-degrade organic matter, such as pyridine and nitrobenzene pollutants, the attraction of nitrogen to the electron cloud of the pyridine ring leads to a low electron cloud density at other positions on the pyridine ring, making it easy to reduce but difficult to oxidize. At the same time, there is the accumulation of intermediates such as hydroxypyridine in the Fenton oxidation mineralization process, which results in slow ring opening, high consumption of hydrogen peroxide, and high cost, and even inability to achieve good mineralization degradation. In the actual treatment process, incineration or even diluted emissions are often used to meet regulatory requirements, which has too high a treatment cost and high risks. This requires the organic coupling of oxidation and reduction processes in the Fenton oxidation process.

[0010] In addition, the use of Fenton technology also has problems such as large consumption of reagents, difficulty in separating effluent water, and difficulty in treating and disposing iron mud. First, when Fenton technology is used alone to directly oxidize and promote the mineralization of difficult-to-degrade pollutants, there are often problems such as excessive use of oxidants and catalysts and high reagent costs; at the same time, the use of Fenton technology in the treatment of aromatic and other organic matter has problems such as self-polymerization of organic pollutants, dark effluent color, and inability to separate mud and water; in addition, the traditional Fenton process often requires a large amount of iron mud to be discharged. The iron mud discharged after Fenton treatment of difficult-to-degrade wastewater contains a large number of incompletely oxidized intermediate metabolites, which leads to the need to treat iron mud as hazardous waste. The cost of treating iron mud hazardous waste is as high as 2,800 to 8,000 yuan / t, which is too expensive. The utilization efficiency of divalent iron in the Fenton oxidation process is extremely low, and the reduction of iron ions becomes the rate-limiting step for the generation of hydroxyl radicals. The recycling of catalysts reduces the generation of iron mud and reduces costs. Summary of the invention

[0011] Through the above analysis and discussion, the present invention proposes a catalytic oxidation purification technology for high chloride ion difficult to degrade wastewater, in order to provide a new approach to solving the above technical problems.

[0012] In order to achieve the above object, as one aspect of the present invention, a method for catalytic oxidation purification of high-chlorine refractory wastewater is provided, comprising the following steps:

[0013] (1) adding nitric acid or sulfuric acid to adjust the pH of the water to be treated to make it acidic, and adding a certain amount of catalyst to obtain water quality 1;

[0014] (2) water quality 1 is introduced into the main reaction zone for reaction, hydrogen peroxide is added, the catalyst is mixed with the added hydrogen peroxide to react to generate hydroxyl radicals, and the reaction process is aerated to enhance the reaction, thereby obtaining water quality 2;

[0015] (3) adding sodium hydroxide to water quality 2 to adjust the pH to make water quality 2 alkaline, and the catalyst self-flocculates to obtain water quality 3;

[0016] (4) The water flows into the catalyst recovery pool, the catalyst is separated from the treated water, the clear liquid is discharged, the catalyst is recycled, and a small amount is discharged.

[0017] Preferably, step (1) is carried out in the pH adjustment zone, and the catalyst is preferably recovered through the catalyst recovery pool and refluxed. At the same time, a certain amount of catalyst is appropriately added from the catalyst storage tank according to different water qualities to maintain the catalyst concentration at a certain value, and then water quality one is obtained.

[0018] As a preferred technical solution of the present invention, the chloride ion concentration of the influent is controlled below 9600 mg / L;

[0019] When the water is directly discharged after catalytic oxidation or the total nitrogen is controlled, sulfuric acid is used in step (1) to adjust the pH of the water to be treated; when the water is biochemically treated after catalytic oxidation or the total nitrogen is not controlled, nitric acid is used in step (1) to adjust the pH of the water to be treated;

[0020] Depending on the water quality, the preferred step (1) is to adjust the pH of the water to be treated to 3.2-6.0;

[0021] Depending on the water quality and treatment requirements, preferably, the catalyst particle size in step (1) is between 120-800 mesh;

[0022] Depending on the water quality and treatment requirements, the catalyst concentration in the solution in step (1) is preferably 3-20 g / L.

[0023] As a preferred technical solution of the present invention, according to different water qualities, the volume ratio of the oxygen introduced in step (2) (standard conditions) to the volume of the water quality 2 is (3-6):1;

[0024] Depending on the water quality, the hydraulic retention time of the reaction process in step (2) is 1-8h;

[0025] According to different water quality and subsequent treatment requirements, after adding hydrogen peroxide in step (2), the total organic carbon (TOC) of the reaction process is: 2 O 2=1: (1-4), or control the amount of hydrogen peroxide added according to the TOC removal rate, control the TOC removal rate below 50% when the reactor is connected to the biochemical treatment section, and control the amount of addition according to the effluent water quality when there is a effluent COD requirement;

[0026] As a preferred technical solution of the present invention, according to different water qualities, NaOH is added in step (3) to adjust the pH to 6.9-7.8.

[0027] As a preferred technical solution of the present invention, according to different water qualities, 94% to 100% of the catalyst in step (4) is refluxed, and 0% to 6% is discharged.

[0028] Depending on the ratio of water quality to catalyst, the surface load during the catalyst separation process in step (4) is 0.7 to 2.0 m / h.

[0029] The present invention further provides a catalytic oxidation purification device for high-chlorine refractory wastewater, the device is used in the above-mentioned purification method, the device comprises: the device comprises a pH adjustment zone, a main reaction zone, a catalyst storage tank, a catalyst replenishment pipe, a pH adjustment flocculation zone, and a catalyst recovery tank;

[0030] The wastewater to be treated enters the pH adjustment zone through the water inlet, nitric acid and / or sulfuric acid are added, the catalyst is added to the catalyst storage tank through the catalyst replenishment pipe, and then enters the main reaction zone, hydrogen peroxide is added, and then enters the pH callback flocculation zone, alkali is added, and then the catalyst is recovered through the catalyst recovery tank, and the treated water is discharged through the water outlet.

[0031] As a preferred technical solution of the present invention, the catalyst recovered by the catalyst recovery pool enters the pH adjustment zone through the catalyst reflux pipeline to achieve catalyst recovery and reuse.

[0032] As a preferred technical solution of the present invention, a gas supply system is provided at the bottom of the main reaction zone to adjust the gas supply.

[0033] As a preferred technical solution of the present invention, the pH adjustment flocculation zone is provided with a stirring device, and catalyst flocculation is achieved through stirring.

[0034] Based on the above technical solutions and background technology, it can be seen that the catalytic oxidation purification device and method of high-chlorine refractory wastewater of the present invention has at least one of the following advantages over the prior art:

[0035] 1. In the treatment process of high-chlorine refractory wastewater, within a certain concentration range, the influence of chloride ions can be basically eliminated, achieving a target pollutant removal rate of more than 97% and a TOC removal rate of more than 90%;

[0036] 2. Due to the catalytic enhancement of the generation of hydroxyl free radicals and oxygen-assisted oxidation, the amount of hydrogen peroxide used is reduced by more than 15%;

[0037] 3. Due to the catalytic enhancement of the generation of hydroxyl free radicals and oxygen-assisted oxidation, the amount of hydrogen peroxide used is reduced by more than 15%;

[0038] 4. As the catalyst consumes hydrogen ions, the acid consumption in the catalytic oxidation process is reduced by more than 30%;

[0039] 3. Thanks to the recycling of catalyst, the iron sludge production is reduced by more than 60%;

[0040] 4. Thanks to the reduction in hydrogen peroxide usage, the decrease in iron sludge production, and the reduction in acid consumption, the overall operating cost is reduced by more than 40%.

[0041] 5. The operation is stable and convenient, and the problems such as floating sludge in Fenton sedimentation tank are avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a flow chart of a catalytic oxidation purification device for high-chlorine refractory wastewater according to the present invention;

[0043] Figure 2 These are two main combination modes of the novel catalytic oxidation stage and the biochemical treatment process described in the present invention;

[0044] Figure 3 The COD effect of influent and effluent during the traditional Fenton treatment of a high-chlorine chloropyridine wastewater.

[0045] Figure 4 The COD effect of the inlet and outlet water in the traditional Fenton treatment process of a certain high-chlorine chloropyridine wastewater using the novel catalytic oxidation technology described in the present invention;

[0046] Figure 5 The comparison of the removal effect of the novel catalytic oxidation technology of the present invention and the traditional Fenton technology on TOC of a high-chlorine chloropyridine wastewater is shown;

[0047] Figure 6 It is the content of heavy metals, sulfides, etc. in the effluent from the new catalytic oxidation technology described in the present invention.

[0048] Among them, 1-water inlet; 2.-pH adjustment area; 3-main reaction area; 4-catalyst storage tank; 5-catalyst replenishment pipe; 6-gas supply system; 7-cobalt phosphide; 8-magnetite; 9-iron sulfide powder; 10-iron oxide powder; 11-pH correction flocculation area; 12-catalyst reflux pipeline; 13-catalyst recovery tank; 14-water outlet. DETAILED DESCRIPTION

[0049] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0050] (1) The pH adjustment zone is equipped with an agitator to allow the acid to react with the influent water, and to fully mix the catalyst refluxed from the catalyst recovery tank and the newly added catalyst with the influent water. More importantly, the flocculated catalyst refluxed from the recovery tank is fully stirred to be dispersed again. Figure 1 ;

[0051] The catalyst is composed of cobalt phosphide, magnetite, pyrite powder and iron oxide powder in the ratio of (0-0.05): (0-0.25): (0.35-1): (0-0.35). Cobalt phosphide, magnetite and pyrite powder mainly provide cobalt ions and divalent iron ions, while iron oxide powder provides a certain amount of trivalent iron ions, so that the catalyst is easy to self-flocculate under alkaline conditions and realize the separation of the catalyst and water. The cost ratio of the catalyst varies according to the water quality.

[0052] During the preparation of the catalyst, the particle size of the catalyst is set to between 120-800 meshes, taking into account both the catalytic activity and the stability of the catalyst.

[0053] Depending on the water quality and the amount of hydrogen peroxide added, the catalyst consumption will also be different. Depending on the catalyst consumption, the catalyst needs to be replenished in real time to keep it at a stable reaction level.

[0054] (2) Add hydrogen peroxide appropriately to the main reaction zone to make the catalyst react well with hydrogen peroxide to produce sufficient hydroxyl radicals. Figure 2 ) stage and effluent water quality. When the reactor is connected to the biochemical treatment stage, the TOC removal rate is controlled below 50%. When there is a effluent COD requirement, the amount of hydrogen peroxide added is controlled according to the effluent water quality. The cost can be further reduced by optimizing the amount of hydrogen peroxide added.

[0055] In order to ensure sufficient stirring and reduce the amount of hydrogen peroxide used during the reaction in the main reaction zone, aeration stirring is adopted. Figure 1 .

[0056] (3) pH adjustment to the flocculation zone allows the added alkali to mix fully with water. On the other hand, under alkaline conditions, divalent iron is converted into trivalent iron, which produces a flocculation effect and separates the catalyst from the water. Figure 1 ;

[0057] (4) In the catalyst recovery tank, the catalyst is precipitated to the bottom of the tank by gravity, the clear liquid is discharged, and the catalyst precipitated to the bottom of the tank is further returned to the pH adjustment area for recycling;

[0058] There is still a certain amount of catalyst failure during the use of the catalyst. By properly eliminating this part of the catalyst, the reaction process can proceed smoothly. Figure 1 .

[0059] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. The technical solution of the present invention is not limited to the specific embodiments listed below:

[0060] Example 1

[0061] The influent of a sewage treatment plant in an industrial park in Hunan is mainly composed of pyridine and chloropyridine compounds, with chloride ions of 3000-5000mg / L, COD between 200-300mg / L, TOC between 100-170mg / L, ammonia nitrogen of 20mg / L, and total nitrogen of about 25mg / L. The original Fenton-hydrolysis acidification-oxidation ditch coupling process was used for treatment. During the treatment process, due to the interference of chloride ions on the Fenton process, there was basically no significant change in COD and TOC before and after the Fenton effluent. Increasing the amount of hydrogen peroxide still could not achieve good removal of COD ( Figure 3 ), since chloropyridines cannot be removed by Fenton technology and have a strong inhibitory effect on nitrifying bacteria, the ammonia oxidation process in the biochemical stage is blocked and the denitrification process is limited. At the same time, pyridines that cannot be well opened contain organic nitrogen, which also affects the TN removal effect of the effluent, and there is pressure to meet the total nitrogen and COD standards of the original treated effluent from the sewage plant.

[0062] After using heterogeneous catalytic oxidation technology, COD can be well removed (COD: H 2 O 2 =1.3, there is basically no removal by traditional Fenton, and ~50% by heterogeneous catalysis)( Figure 4 ). The TOC removal effect is good, while the traditional Fenton removal effect is not obvious ( Figure 5 ), the catalytic oxidation technology of the present invention can achieve good removal of this.

[0063] After adopting this technology, according to TOC: H 2 O 2= 2.0 catalyst, catalyst cobalt phosphide, magnetite, pyrite powder and iron oxide powder = 0.03: 0.15: 0.62: 0.2 ratio, particle size according to 100 mesh, 600 mesh, 800 mesh, 800 mesh ratio, catalyst dosage at 3g / L, catalyst recovery rate 98%, main reaction zone residence time 4h conditions, achieved COD removal rate 60%, TOC removal rate 50%, target pollutant removal rate 90%, iron sludge production decreased by 80%, comprehensive treatment cost decreased by 50%. Good removal of target pollutants laid a good foundation for subsequent biochemical treatment, COD and total nitrogen achieved stable compliance, total effluent COD less than 40mg / L, total nitrogen less than 12mg / L.

[0064] Example 2

[0065] The influent of a sewage treatment station of a pesticide enterprise in Jiangsu is high-chlorine and difficult-to-degrade wastewater. The influent contains chlorinated organics such as oxazolidinone, imidacloprid, thiazolone, pyridine, and thiazole organics. The influent COD is 8000-15000mg / L, and the chloride ion is 4000-6000mg / L. The sewage treatment station mainly uses Fenton pretreatment-anaerobic-aerobic process for treatment. Due to the interference of chloride ions, the Fenton treatment effect is not obvious. At the same time, the output of iron sludge is large, and the cost of disposal as hazardous waste is high. In order to temporarily ensure the normal operation of some production processes, some chlorinated organics and pyridine organics are incinerated, but the cost is too high, and the company's production capacity is restricted by the treatment of high-salinity difficult-to-degrade wastewater.

[0066] After the catalytic oxidation technology of the present invention is used as the pretreatment technology, the amount of hydrogen peroxide added is based on COD: H 2 O 2 =1.0, catalyst cobalt phosphide, magnetite, pyrite powder and iron oxide powder = 0.08:0.26:0.46:0.2 ratio, particle size of 300 mesh, 800 mesh, 800 mesh, 600 mesh ratio, catalyst dosage of 4g / L, catalyst recovery rate of 93%, main reaction zone residence time of 3h, COD removal rate of 40%, TOC removal rate of 20%, target pollutant removal rate of 85%, iron sludge production decreased by 70%, comprehensive treatment cost decreased by 65%, effluent heavy metal content was lower than the emission standard, the catalyst was safe and effective ( Figure 6 ).

[0067] After the high-chlorine difficult-to-degrade wastewater was properly treated, the factory's production capacity was steadily improved and its market share increased steadily.

[0068] Example 3

[0069] The drainage of a pigment production enterprise in Liaoning mainly contains polycyclic aromatic hydrocarbons such as perylene, with influent COD ~3000mg / L, chloride ion ~2000mg / L, total nitrogen ~200mg / L, and ammonia nitrogen ~150mg / L. It is mainly treated by Fenton and chlorination at the breakpoint. The consumption of hydrogen peroxide in the Fenton treatment process is too large, and the cost is too high. The cost of water treatment agent is 40 yuan / t. The output of iron sludge is large, and the cost of treating it as hazardous waste is too high, which is too heavy for enterprises.

[0070] After adopting the catalytic oxidation treatment of the present invention as the deep treatment technology, the amount of hydrogen peroxide added is based on COD: H 2 O 2 =0.5, catalyst cobalt phosphide, magnetite, pyrite powder and iron oxide powder = 0.02:0.45:0.33:0.2 ratio, particle size is 600 mesh, 500 mesh, 800 mesh, 800 mesh ratio, catalyst dosage is 3g / L, catalyst recovery rate is 90%, main reaction zone residence time is 3h, COD removal rate is 50%, TOC removal rate is 30%, target pollutant removal rate is 85%, iron sludge production is reduced by 68%, and comprehensive treatment cost is reduced by 50%. It saves costs for enterprises.

[0071] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for catalytic oxidation purification of high-chlorine refractory wastewater, characterized in that: The steps include: Purification is performed using the following device, which includes a pH adjustment zone, a main reaction zone, a catalyst storage tank, a catalyst replenishment pipe, a pH adjustment flocculation zone, and a catalyst recovery tank; The wastewater to be treated enters the pH adjustment zone through the water inlet, nitric acid and / or sulfuric acid are added, the catalyst is added to the catalyst storage tank through the catalyst replenishing pipe, and then enters the main reaction zone, hydrogen peroxide is added, and then enters the pH adjustment flocculation zone, alkali is added, and then the catalyst is recovered through the catalyst recovery tank, and the treated water is discharged through the water outlet; (1) adding nitric acid or sulfuric acid to adjust the pH of the water to be treated to make it acidic, and adding a certain amount of catalyst to obtain water quality 1; (2) water quality 1 is introduced into the main reaction zone for reaction, hydrogen peroxide is added, the catalyst is mixed with the added hydrogen peroxide to react to generate hydroxyl radicals, and the reaction process is aerated to enhance the reaction, thereby obtaining water quality 2; (3) adding sodium hydroxide to water quality 2 to adjust the pH to make water quality 2 alkaline, and the catalyst self-flocculates to obtain water quality 3; (4) The water flows into the catalyst recovery pool, the catalyst is separated from the treated water, the clear liquid is discharged, the catalyst is recycled, and a small amount is discharged; Wherein, the chloride ion concentration of the influent in step (1) is below 13000 mg / L; The pH in step (1) is 3.2-6.0; The catalyst described in step (1) is composed of cobalt phosphide, magnetite, ferrous sulfide powder and iron oxide powder in a ratio of (0-0.05): (0-0.25): (0.35-1): (0-0.35), and each component is not 0; The catalyst described in step (1) is produced in a factory by processing one of its raw materials, pyrite powder, which is discharged after deactivation during the desulfurization process by an iron oxide desulfurizer, with pyrite powder as an appropriate supplement, the iron oxide powder comes from iron oxide waste in the metal processing industry, and limonite powder as an appropriate supplement; The catalyst particle size in step (1) is between 120 and 800 meshes; The catalyst concentration in the solution in step (1) is 3-20 g / L.

2. The purification method according to claim 1, characterized in that: The catalyst is added by reflux from the catalyst recovered in the catalyst recovery tank.

3. The purification method according to claim 1, characterized in that: In step (2), the volume ratio of the oxygen introduced (standard condition) to the volume ratio of the water quality 2 is (3-6):1; The hydraulic retention time of the reaction process in step (2) is 1-8h; After adding hydrogen peroxide in step (2), the total organic carbon (TOC) of the reaction process: H2O2=1:(1-4).

4. The purification method according to claim 1, characterized in that: In step (3), NaOH is added to adjust the pH to 6.9-7.

8.

5. The purification method according to claim 1, characterized in that: In step (4), 94% to 100% of the catalyst is refluxed, and 0% to 6% is discharged; and the surface load during the catalyst separation process in step (4) is 0.7 to 2.0 m / h.

6. The purification method according to claim 1, characterized in that: The catalyst recovered by the catalyst recovery pool enters the pH adjustment zone through the catalyst reflux pipeline to achieve catalyst addition.

7. The purification method according to claim 1, characterized in that: A gas supply system is provided at the bottom of the main reaction zone to regulate the gas supply.

8. The purification method according to claim 1, characterized in that: The pH adjustment flocculation zone is provided with a stirring device, and the catalyst flocculation is achieved through stirring.

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