Process for the preparation of an ozone oxidation catalyst and use thereof

Abstract

The application discloses a preparation method and application of an ozone oxidation catalyst. 2+ The preparation method of the ozone oxidation catalyst comprises the following steps: adding a sandstone carrier, Fe, H2O2, an iron source material and wastewater into a fluidized bed reactor to obtain initial reaction liquid with pH of 4-5; swelling the sandstone carrier in the initial reaction liquid; and obtaining the sandstone carrier loaded with hydroxyl iron oxide crystals after reaction of the initial reaction liquid. The catalyst prepared by the application has a nano structure, high active component, and can realize degradation of a large category of wastewater such as coal chemical industry, coking and acrylic fiber by catalyzing ozone. The catalyst is simple and economical to prepare, has less active catalytic species dissolved in the running process, has a large pH range for degradation of the wastewater, and has the advantages of easy preparation, high efficiency, stability and low economic cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, in particular to a preparation method and application of an ozone oxidation catalyst. BACKGROUND

[0002] Advanced oxidation technology is widely used in the advanced treatment of refractory wastewater, and ozone oxidation technology and catalytic ozone oxidation technology can utilize ozone molecules or generate strong oxidizing hydroxyl radicals (·OH) in the presence of catalysts due to the reduction potential of ozone being 2.07V, which is a common advanced oxidation process for the oxidation treatment of pollutants. In particular, ozone is a strong selective oxidizer with strong oxidation capacity for the positions with high electron density on unsaturated bonds and benzene rings. However, the application of ozone oxidation in water treatment is limited by the following aspects: the low solubility of ozone in water results in low utilization rate, serious loss and waste in the ozone treatment process; the direct oxidation of ozone molecules has a certain selectivity and cannot completely degrade or mineralize the refractory organic matter in the water body; and so on. Catalytic ozone oxidation technology is a new type of advanced oxidation technology developed in recent years, which refers to the promotion of the decomposition of ozone molecules by metal ions in the solution, metal oxides or metal oxides supported on carriers, and the like to strengthen the ozone oxidation performance. Studies have shown that catalytic ozonation can improve the utilization rate of ozone and promote the generation of more active radicals.

[0003] Catalytic ozone oxidation technology is divided into homogeneous catalytic ozone oxidation and heterogeneous catalytic ozone oxidation. Among them, homogeneous catalytic ozone oxidation refers to the catalytic oxidation effect of promoting the decomposition of ozone by metal ions in the solution; heterogeneous catalytic ozone oxidation refers to the catalytic effect of metal oxides or catalysts supported on carriers. The homogeneous catalytic ozonation introduces metal ions into the system, and the catalyst is easy to lose, difficult to recycle, and the effluent has the problem of secondary pollution; and in the heterogeneous catalytic system, the catalyst can be better recovered from the reaction medium, and due to its high efficiency, low cost and easy recovery, it has attracted more and more attention in recent years.

[0004] The ideal catalysts for catalytic ozone oxidation mainly include metals (Fe, Mn, etc.) and metal oxides (TiO2, Al2O3, MnO2), hydroxyl oxides (AlOOH, FeOOH), etc. The introduction of carriers can increase the specific surface area in contact with the reactants, save the amount of catalyst to a certain extent, reduce the cost, and increase the utilization rate of ozone. Common carriers include activated carbon, lead oxide, ceramic, silicon dioxide, etc. The type and structure of the carrier affect the catalytic activity and surface properties of the catalyst, and further affect the catalytic ozonation performance. Therefore, it is crucial to select a carrier with good stability and environmental friendliness for the catalytic ozone oxidation performance.

[0005] At present, most of the catalysts used in the metal catalytic oxidation process are still in the use of nanometer catalysts. Although these catalysts have high catalytic activity, they are difficult to popularize due to the problems of solid-liquid separation difficulty and different degrees of metal elution. Although the supported catalysts solve the problem of solid-liquid separation, the catalysts have the problems of low catalytic activity, complex preparation process and high cost. Therefore, selecting an efficient, stable, easy-to-separate with water and economical and practical catalyst preparation process is the premise for the popularization of the catalytic oxidation process.

[0006] In view of this, the present application is proposed. SUMMARY

[0007] The present application aims to provide a preparation method and application of an ozone oxidation catalyst, and provide an economical and practical catalyst preparation method.

[0008] The present application is implemented as follows:

[0009] In a first aspect, the present application provides a preparation method of an ozone oxidation catalyst, comprising the preparation of hydroxyl iron oxide crystals: adding sandstone carriers, Fe 2+ , H2O2, iron source materials and wastewater with a pH of 4-5 into a fluidized bed reactor to obtain an initial reaction solution, swelling the sandstone carriers in the initial reaction solution, and obtaining sandstone carriers loaded with hydroxyl iron oxide crystals after the reaction of the initial reaction solution.

[0010] In an optional embodiment, the liquid in the fluidized bed reactor is discharged after the reaction of the initial reaction solution, and Fe 2+ , H2O2, iron source materials and wastewater with a pH of 4-5 are added into the fluidized bed reactor again to obtain an initial reaction solution, and the preparation step of the hydroxyl iron oxide crystals is repeated.

[0011] In an optional embodiment, the reaction time in the preparation step of the hydroxyl iron oxide crystals is 7-9h;

[0012] Preferably, the sandstone carriers participate in the preparation step of the hydroxyl iron oxide crystals for 3-4 times to obtain the ozone oxidation catalyst.

[0013] In an optional embodiment, the initial reaction solution meets at least one of the following ①-④:

[0014] ① The COD of the initial reaction solution is 200-500mg / L;

[0015] ② The sandstone carrier concentration in the initial reaction solution is 300-500g / L;

[0016] ③ The Fe 2+ added amount and COD ratio is 2-3:1;

[0017] IV. the ratio of the amount of H2O2 added to the initial reaction solution to COD is 2-3:1.

[0018] In an optional embodiment, the iron source material is at least one of pig iron powder, zero-valent iron, ferric nitrate and iron oxide.

[0019] Preferably, the iron source material comprises pig iron powder or zero-valent iron, ferric nitrate and iron oxide.

[0020] More preferably, the amount of pig iron powder or zero-valent iron added to the initial reaction solution is 0.8-1.5 g / L; and the amount of ferric nitrate and iron oxide added is 1.5-3 g / L.

[0021] In an optional embodiment, the sandstone carrier is at least one of sea sand, river sand or quartz sand.

[0022] And / or, the wastewater is at least one of coal chemical wastewater, petrochemical wastewater and dyeing wastewater.

[0023] In an optional embodiment, the sandstone carrier is soaked in an acid solution with a pH of 1-2 for 20-28 h, and then washed until the pH of the effluent is neutral, and then used for the preparation of hydroxyl iron oxide crystals.

[0024] Preferably, the acid solution is a hydrochloric acid solution.

[0025] In an optional embodiment, the surface of the ozone oxidation catalyst is nanostructured.

[0026] In a second aspect, the present application provides a water treatment method, wherein a mixture of ozone and wastewater to be treated is contacted with the ozone oxidation catalyst according to any one of the preceding embodiments for 4 min or more.

[0027] In an optional embodiment, at least one of the following ⑤-⑧ is satisfied:

[0028] V. the pH of the wastewater to be treated is 6-9;

[0029] VI. the COD of the wastewater to be treated is 100-400 mg / L;

[0030] VII. the ratio of the concentration of ozone to the COD of the wastewater to be treated is (0.5-10):1.

[0031] VIII. the ozone oxidation catalyst is filled in a fixed bed catalytic oxidation reactor, and the water treatment is carried out in the fixed bed catalytic oxidation reactor.

[0032] The present application has the following beneficial effects:

[0033] The catalyst prepared by the application has a nano structure, high active ingredients and can realize degradation of a large class of wastewater such as coal chemical industry, coking and acrylic fiber by catalyzing ozone.

[0034] The catalyst is simple and economical to prepare, and has less active catalytic species dissolved during operation, so it has the advantages of easy preparation, high efficiency, stability and low economic cost compared with the catalysts on the market.

[0035] The application can degrade wastewater in a larger pH range. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiments will be briefly introduced below, and it should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0037] Figure 1 XRD characterization diagram of high-efficiency active catalyst 1 and original carrier;

[0038] Figure 2 SEM-EDS characterization diagram of high-efficiency active catalyst 1 and ordinary carrier;

[0039] Figure 3 Degradation effect of active catalyst 1, active catalyst 2 and commercial catalyst on caprolactam wastewater under different O3 / COD conditions;

[0040] Figure 4 Removal effect of active catalyst 1, active catalyst 2 and commercial catalyst on acrylic fiber wastewater and coking wastewater;

[0041] Figure 5 Degradation effect of active catalyst 1, active catalyst 2 and commercial catalyst on caprolactam wastewater under different pH conditions. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of the application more clear, the technical solutions in the embodiments of the application will be clearly and completely described below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0043] The application provides a preparation method of an ozone oxidation catalyst, which comprises preparation of hydroxyl iron oxide crystals: adding a sand carrier, Fe 2+wastewater, a hydrogen peroxide source, a ferrous source, and wastewater with pH of 4-5 to obtain an initial reaction solution, swelling the sandstone carrier in the initial reaction solution, and obtaining a sandstone carrier loaded with iron oxyhydroxide crystals after the initial reaction solution is reacted.

[0044] The embodiment uses a fluidized bed metastable crystallization technology to form iron oxide crystal catalysts with high catalytic activity. Specifically, wastewater, a ferrous source, hydrogen peroxide, and a carrier are fully swelled and contacted in a fluidized bed bed layer. As the reaction proceeds, the Fe ions in the system will undergo hydrolysis. After swelling, the reaction solution will drop to pH 3-4. The catalyst is formed in this metastable pH range. On the one hand, iron is more likely to crystallize on the surface of the carrier, and the loading of iron oxyhydroxide is relatively large. On the other hand, the obtained iron oxyhydroxide is also more stable. Characterization analysis shows that the catalyst surface has abundant iron oxyhydroxide and nano structures.

[0045] In an alternative embodiment, the liquid in the fluidized bed reactor is discharged after the initial reaction solution is reacted, and a ferrous source 2+ wastewater, a hydrogen peroxide source, a ferrous source, and wastewater with pH of 4-5 to obtain an initial reaction solution, swelling the sandstone carrier in the initial reaction solution, and obtaining a sandstone carrier loaded with iron oxyhydroxide crystals after the initial reaction solution is reacted.

[0046] Although a continuous flow mode can also load iron oxyhydroxide on the sandstone carrier, the loss of raw materials is large, especially the loss of Fe 2+ , H2O2, and other soluble components. The loss of raw materials increases the cost, so the fluidized bed reactor in this embodiment is operated intermittently.

[0047] In this embodiment, when the preparation step of the iron oxyhydroxide crystals is repeated, the liquid in the fluidized bed reactor is discharged, the sandstone carrier is retained in the fluidized bed reactor, and the generated iron oxyhydroxide continues to be loaded on the sandstone carrier, thereby increasing the loading of iron oxyhydroxide.

[0048] In an alternative embodiment, the reaction time in the preparation step of the iron oxyhydroxide crystals is 7-9h. If the reaction time is too long, the concentration of the reactants decreases, the generation rate of iron oxyhydroxide decreases, and the efficiency is not improved.

[0049] In a preferred embodiment, the sandstone carrier participates in the preparation step of the iron oxyhydroxide crystals at least 3 times. Preferably, the sandstone carrier participates in the preparation step of the iron oxyhydroxide crystals 3-4 times to obtain an ozone oxidation catalyst.

[0050] The more times the sandstone carrier participates in the preparation step of the iron oxyhydroxide crystals, the more iron oxyhydroxide is loaded, but the catalytic efficiency of the catalyst is not only related to the loading amount of iron oxyhydroxide, but also related to the surface area of the contact with the wastewater and the number of active sites on the surface of the catalyst. Under the preparation conditions, too much iron oxyhydroxide may cause the accumulation and agglomeration of the crystals, which may in turn reduce the surface area of the contact with the wastewater and the number of active sites that can play a catalytic role. Therefore, the number of preparation steps of the iron oxyhydroxide crystals should not be too high.

[0051] In an optional embodiment, the concentration of the sandstone carrier in the initial reaction solution is 300-500 g / L, and specifically can be 300 g / L, 350 g / L, 400 g / L, 450 g / L, 500 g / L, or any value between 300 g / L and 500 g / L. The sandstone carrier needs to be constantly impacted between particles or reactants in the fluidized bed reactor, and the sandstone carrier needs to be constantly impacted, reacted, crystallized, dissolved, and recrystallized. If the concentration of the sandstone carrier is too low, the reaction efficiency will be reduced, and if the concentration of the sandstone carrier is too high, the swelling will be difficult.

[0052] In an optional embodiment, the COD of the initial reaction solution is 200-500 mg / L, and specifically can be 200 mg / L, 300 mg / L, 400 mg / L, 500 mg / L, or any value between 200 mg / L and 500 mg / L.

[0053] In an optional embodiment, the Fe 2+ The ratio of the amount of H2O2 added to the COD is 2-3:1, and specifically can be 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, or any value between 2:1 and 3:1.

[0054] In an optional embodiment, the ratio of the amount of H2O2 added to the COD in the initial reaction solution is 2-3:1, and specifically can be 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, or any value between 2:1 and 3:1.

[0055] The COD of the initial reaction solution and the amount of H2O2 added are optimized through experiments, and within the above range, the catalytic efficiency and stability of the ozone oxidation catalyst obtained are better. 2+

[0056] In an optional embodiment, the iron source material is at least one of pig iron powder, zero-valent iron, ferric nitrate, and iron oxide. The iron source material can promote the crystallization of iron oxyhydroxide, improve the reaction efficiency, and shorten the preparation time. The zero-valent iron is also known as reduced iron powder, and the pig iron powder is also known as iron filings.

[0057] ​In a preferred embodiment, the iron source material comprises pig iron powder or zero-valent iron, ferric nitrate and ferric oxide.

[0058] The iron source material in the present application can be any one of pig iron powder, zero-valent iron, ferric nitrate and ferric oxide, or a combination of two or more thereof, but the applicant has verified through experiments that the combination of pig iron powder, ferric nitrate and ferric oxide, or the combination of zero-valent iron, ferric nitrate and ferric oxide has better catalytic effect.

[0059] In a more preferred embodiment, the pig iron powder or zero-valent iron is added in an amount of 0.8-1.5 g / L in the initial reaction solution, and specifically can be 0.8 g / L, 1.0 g / L, 1.2 g / L, 1.4 g / L, 1.5 g / L or any value between 0.8-1.5 g / L; the ferric nitrate and ferric oxide are each added in an amount of 1.5-3 g / L, and specifically can be 1.5 g / L, 2.0 g / L, 2.5 g / L, 3 g / L or any value between 1.5-3 g / L.

[0060] In an optional embodiment, the sandstone carrier is at least one of sea sand, river sand or quartz sand.

[0061] In an optional embodiment, the wastewater is at least one of coal chemical wastewater, petrochemical wastewater and dyeing wastewater, and in general, other wastewaters containing reducing substances can also be used.

[0062] In an optional embodiment, the sandstone carrier is soaked in an acid solution with a pH of 1-2 for 20-28 h, and then washed until the pH of the effluent is neutral, and then used for the preparation of hydroxyl ferric oxide crystals. Before loading the hydroxyl ferric oxide, the sandstone carrier is cleaned with a strong acid to remove impurities in the surface or internal pores, so as to avoid the influence of impurities on the loading of hydroxyl ferric oxide.

[0063] In a preferred embodiment, the acid solution is a hydrochloric acid solution, which can more effectively remove liposoluble impurities in the internal pores of the sandstone carrier.

[0064] In an optional embodiment, the surface of the ozone oxidation catalyst is nanostructured. Compared with other structures, the nanostructured surface has a larger specific surface area, more sites for loading hydroxyl ferric oxide, a larger contact area with the liquid phase during catalytic ozone oxidation reaction, more active sites and higher catalytic efficiency.

[0065] The present application provides a water treatment method, wherein the mixture of ozone and wastewater to be treated is contacted with the ozone oxidation catalyst according to any one of the preceding embodiments for more than 4 min, and the treatment of the wastewater to be treated can be completed in about 4 min, and the treatment efficiency is relatively high.

[0066] After the preparation of the ozone oxidation catalyst, it can be simply washed with pure water until the pH is neutral, and then used for wastewater treatment. In some cases, if the wastewater to be treated does not exceed the allowable range of pH after washing, it can also be directly used for water treatment.

[0067] In an optional embodiment, the pH of the wastewater to be treated is 6-9, and specifically can be 6, 7, 8, 9 or any value between 6-9. For the degradation of wastewater, there is a larger pH range, and the type of wastewater to be treated is more suitable and has better universality.

[0068] In an optional embodiment, the COD of the wastewater to be treated is 100-400 mg / L, and specifically can be 100 mg / L, 200 mg / L, 300 mg / L, 400 mg / L or any value between 100-400 mg / L.

[0069] In an optional embodiment, the ratio of the concentration of ozone to the COD of the wastewater to be treated is (0.5-10):1, and specifically can be 0.5:1, 1:1, 2:1, 4:1, 6:1, 8:1, 10:1 or any value between (0.5-10):1.

[0070] In an optional embodiment, the ozone oxidation catalyst is filled in a fixed bed catalytic oxidation reactor, and the water treatment is carried out in the fixed bed catalytic oxidation reactor.

[0071] The features and properties of the present application are further described in detail below in combination with examples.

[0072] Example 1

[0073] After the sea sand is soaked in hydrochloric acid with pH=1 for 24h, it is washed until the pH of the effluent is neutral and is put into a fluidized bed reactor. Then Fe 2+ , H2O2, iron source material and coal chemical wastewater are added into the fluidized bed reactor, wherein the coal chemical wastewater has pH=4.5 and COD=400 mg / L; the sea sand content is 300 g / L; the addition amounts of ferric nitrate, iron oxide and zero-valent iron as the iron source material are 2.4 g / L, 1.6 g / L and 0.8 g / L respectively, and the addition amount of Fe 2+ satisfies Fe 2+ :COD=2:1, and the addition amount of H2O2 satisfies H2O2:COD=2:1. The fluidized bed is operated in an intermittent mode, and after each continuous operation for 8h, the wastewater is poured out, and after repeating for 3 times, the active catalyst 1 is prepared. The active catalyst 1 and the original carrier after hydrochloric acid soaking are characterized, and the results are as follows: Figure 1 and Figure 2 , Figure 1 It can be seen that the active catalyst obtained by the method generates hydroxyl iron oxide on the surface.Figure 2 The active catalyst 1 has a nanostructure on the surface, and the iron content on the surface is greatly increased compared to the original carrier. The surface iron content is more than 14wt% by quantitative analysis of the surface iron oxide hydroxyl.

[0074] The active catalyst 1 and the original carrier were compared in terms of the ability to catalyze ozone degradation of pollutants. The ozone oxidation catalyst was filled in a fixed bed catalytic oxidation reactor, and the effect on the COD = 142 mg / L, pH = 8.07, and non-biodegradable caprolactam wastewater was investigated in a continuous flow mode. The ozone concentration was designed by controlling the gas phase ozone concentration and changing the flow rate of the influent, with a constant ozone addition rate. The COD concentration was 4:1, the wastewater residence time on the catalyst was 4 min, and the effluent pH was 8.02. The effluent COD results are shown in Table 1. The removal effect of the active catalyst 1 was significantly higher than that of the original carrier, proving that the active catalyst has excellent catalytic potential.

[0075] Table 1 Removal effect of active catalyst 1 and original carrier on wastewater COD catalyzed by ozone

[0076] Catalytically active body Active catalyst 1 Original support Effluent COD (mg / L) 89 134 COD removal rate (%) 37.3％ 5.6％

[0077] The active catalyst 1 obtained in this example was used to treat caprolactam wastewater under the above operating conditions. After 120 min of continuous operation, the effluent COD could still reach 80-90 mg / L, and the COD removal rate could reach more than 36%, showing good stability under the experimental conditions.

[0078] In addition, the active catalyst 1 obtained in this example was used to treat caprolactam wastewater under the above operating conditions. The COD removal effect was improved when the residence time of the wastewater on the catalyst was extended, but the improvement was slow. When the residence time was extended to 20 min, the effluent COD did not decrease significantly and stabilized at 80 mg / L, and the COD removal rate could reach 44%.

[0079] Example 2

[0080] The sea sand was soaked in hydrochloric acid with pH = 1 for 24 h, then washed to neutral pH and put into a fluidized bed reactor. Fe 2+ , H2O2, iron source material and coal chemical wastewater were added to the fluidized bed reactor, wherein the coal chemical wastewater had pH = 4.5 and COD = 400 mg / L; the sea sand content was 300 g / L; the addition amounts of ferric nitrate, iron oxide and pig iron powder as the iron source material were 2.4 g / L, 1.6 g / L and 0.8 g / L, respectively, and the addition amount of Fe 2+ met the requirement of Fe 2+:COD=2:1, the dosage of H2O2 meets H2O2:COD=2:1. The fluidized bed is operated in an intermittent mode, and the wastewater is poured out after 8h of continuous operation each time. After repeating for 3 times, the active catalyst 2 is prepared, which is compared with the active catalyst 1 in Example 1 and the alumina catalyst in terms of the ability of catalyzing the degradation of pollutants. The ozone oxidation catalyst is filled in a fixed bed catalytic oxidation reactor, and the influence on the degradation of the non-biodegradable wastewater with COD=200mg / L and pH=8.07 is explored in a continuous flow mode. The ozone concentration / COD concentration is designed to be 0.5:1, 1:1, 2:1 and 5:1 respectively by controlling the gas-phase ozone concentration and the ozone addition rate, which correspond to the residence time of the wastewater of 1min, 2min, 4min and 10min respectively. The results are shown in Table 2. Figure 3 The effect of the active catalyst 2 is better than that of the active catalyst 1 and the commercial catalyst (alumina catalyst), especially when the ozone concentration / COD concentration is 0.5:1-1:1. The degradation effect of the wastewater presents active catalyst 2>active catalyst 1>commercial catalyst, and the specific data are shown in Table 2.

[0081] Table 2

[0082] Residence time (min) Commercial catalyst COD (mg / L) Active catalyst 1 COD (mg / L) Active catalyst 2 COD (mg / L) 10.00 144 152 140 4.00 156 158 152 2.00 176 168 166 1 190 182 176

[0083] Example 3

[0084] The active catalyst 1 and the active catalyst 2 prepared in Example 1 and Example 2 are compared with the commercial catalyst (alumina catalyst) to explore the degradation effect on the acrylonitrile wastewater and the coking wastewater of a certain project.

[0085] The COD of the acrylonitrile wastewater is 185mg / L, and the pH is 7.0. The pH of the wastewater is adjusted to 9. The COD of the coking wastewater is 157mg / L, and the pH is 8.06. The pH is not adjusted. The ozone oxidation catalyst is filled in a fixed bed catalytic oxidation reactor, and the degradation effect of the wastewater is obtained by controlling the gas-phase ozone concentration and the ozone addition rate and designing the water flow rate to make the ozone concentration in the system 1100mg / L. At this time, the residence time of the wastewater in the catalyst is 4min, and the results are shown in Table 3. Figure 4 The active catalyst 1 and the active catalyst 2 show more excellent potential for degrading the COD of the two kinds of wastewater than the alumina catalyst, and the degradation potential of the pollutants presents active catalyst 1>active catalyst 2>alumina catalyst.

[0086] Example 4

[0087] The active catalyst 1 and the active catalyst 2 prepared in the examples 1 and 2 were compared with the commercial catalyst (alumina catalyst) to explore the effect of pH on the degradation of caprolactam wastewater. The ozone oxidation catalysts were filled in a fixed bed catalytic oxidation reactor, and the effect on the caprolactam of the wastewater with COD = 200 mg / L was explored in a continuous flow mode. By fixing the ozone addition rate and the flow rate of the influent, the gaseous ozone addition concentration was controlled to be 583 mg / L, the wastewater residence time was 4 min, the pH of the wastewater was adjusted to be 6, 7, 8 and 9, and the catalytic oxidation potential of the three catalysts was compared. The results are shown in Table 3. Figure 5 The three types of catalysts have certain catalytic oxidation potential under different pH conditions, as shown in Table 3. Under the condition of pH = 9, the catalytic performance of the commercial catalyst is the best, but under the condition of pH = 6-8, the catalytic oxidation performance of the active catalyst 2 is the best, and the catalytic performance of the commercial catalyst and the active catalyst 1 is close. The suitable pH of the conventional catalytic ozone catalyst is 7-9, while the catalyst cultured in the metastable state of the present application also has certain catalytic oxidation effect under the condition of near acidity to neutrality, which widens the pH.

[0088] Table 3

[0089] Residence time (min) Commercial catalyst COD (mg / L) Active catalyst 1 COD (mg / L) Active catalyst 2 COD (mg / L) 6 140 140 126 7 138 140 136 8 142 142 142 9 138 150 144

[0090] Example 5

[0091] The sea sand was soaked in hydrochloric acid with pH = 1.5 for 20 h, then washed to neutral pH and put into a fluidized bed reactor, and then Fe 2+ , H2O2, catalyst and coal chemical wastewater were added into the fluidized bed reactor, wherein the pH of the coal chemical wastewater was 4, the COD was 400 mg / L, the content of the sea sand was 400 g / L, the addition amount of the catalysts of ferric nitrate, iron oxide and zero-valent iron was 2 g / L, 3 g / L and 1.2 g / L respectively, the addition amount of Fe 2+ met the Fe 2+ : COD = 3: 1, and the addition amount of H2O2 met H2O2: COD = 3: 1. The fluidized bed was operated in an intermittent mode, and after 8 h of continuous operation each time, the wastewater was poured out, and after repeating for 3 times, the active catalyst was prepared. The ozone oxidation catalyst was filled in a fixed bed catalytic oxidation reactor, and the effect on the caprolactam of the wastewater with COD = 200 mg / L and pH = 8.07 was explored in a continuous flow mode. By controlling the gaseous ozone addition concentration and the ozone addition rate unchanged, the ozone addition concentration was designed to be COD concentration of 4: 1, and the wastewater residence time on the catalyst was 4 min. The effluent COD and COD removal rate were better than those of the original carrier.

[0092] Example 6

[0093] After the sea sand is soaked in hydrochloric acid with pH=2 for 28 hours, it is washed to neutral pH and put into a fluidized bed reactor, and Fe 2+ , H2O2, a catalyst and coal chemical wastewater are added into the fluidized bed reactor, wherein the coal chemical wastewater has pH=5 and COD=100 mg / L; the sea sand has a content of 500 g / L; the iron nitrate, iron oxide and zero-valent iron as the catalyst are added in amounts of 3 g / L, 2 g / L and 1.5 g / L respectively, and the dosing amount of Fe 2+ satisfies Fe 2+ :COD=2.5:1, and the dosing amount of H2O2 satisfies H2O2:COD=2.5:1. The fluidized bed is operated in an intermittent mode, the wastewater is poured out after 8 hours of continuous operation each time, and the active catalyst is prepared after repeating three times. The ozone oxidation catalyst is filled in a fixed bed catalytic oxidation reactor, and the influence on the non-degradable wastewater caprolactam with COD=200 mg / L and pH=8.07 is explored in a continuous flow mode. By controlling the gas-phase ozone dosing concentration and the ozone dosing rate unchanged, the ozone dosing concentration is changed by changing the flow rate of the influent, the COD concentration is 4:1, the residence time of the wastewater on the catalyst is 4 min, and the effluent COD and COD removal rate are better than those of the original carrier.

[0094] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of water treatment, characterized by, The mixture of ozone and the wastewater to be treated is contacted with an ozone oxidation catalyst for more than 4 minutes, the ozone oxidation catalyst is prepared by a method comprising the preparation of iron oxyhydroxide crystals: adding a sandstone carrier, Fe 2+ , H2O2, an iron source material and wastewater with a pH of 4-5 into a fluidized bed reactor to obtain an initial reaction solution, swelling the sandstone carrier in the initial reaction solution, and obtaining a sandstone carrier loaded with iron oxyhydroxide crystals after the reaction of the initial reaction solution. The iron source material is pig iron powder, ferric nitrate and ferric oxide, the pig iron powder is added in the initial reaction solution in an amount of 0.8-1.5 g / L; the ferric nitrate and the ferric oxide are both added in an amount of 1.5-3 g / L.

2. The water treatment method according to claim 1, characterized by, After the initial reaction solution is reacted, the liquid in the fluidized bed reactor is discharged, and Fe 2+ , H2O2, an iron source material, and wastewater having a pH of 4-5 are added again to the fluidized bed reactor to obtain an initial reaction solution, and the preparation step of the ferric oxyhydroxide crystal is repeated.

3. The water treatment method of claim 1, wherein, In the preparation step of the ferric oxyhydroxide crystal, the reaction time is 7-9 h.

4. The water treatment method according to claim 2, characterized by, The sandstone carrier is used in the preparation step of the ferric oxyhydroxide crystal for 3-4 times to obtain an ozone oxidation catalyst.

5. The water treatment method of claim 1, wherein, The COD of the initial reaction solution is 200-500 mg / L. And / or, the sandstone carrier concentration in the initial reaction solution is 300-500 g / L.

6. The water treatment method of claim 1, wherein, The sandstone carrier is at least one of sea sand, river sand or quartz sand. And / or, the wastewater in the preparation process of the ozone oxidation catalyst is at least one of coal chemical industry wastewater, petrochemical wastewater and printing and dyeing wastewater.

7. The water treatment method of claim 1, wherein, The sandstone carrier is soaked in an acid solution with a pH of 1-2 for 20-28 h, then washed until the pH of the effluent is neutral, and then used for the preparation of ferric oxyhydroxide crystal.

8. The water treatment method according to claim 7, characterized in that, The acid solution is a hydrochloric acid solution.

9. The water treatment method of claim 1, wherein, The ozone oxidation catalyst is filled in a fixed bed catalytic oxidation reactor, and the water treatment is carried out in the fixed bed catalytic oxidation reactor. The pH of the wastewater to be treated is 6-9; and / or, the COD of the wastewater to be treated is 100-400 mg / L.

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