Catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater and preparation method thereof

Abstract

The application relates to the technical field of pharmaceutical wastewater treatment, and discloses a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater and a preparation method thereof, and aims to solve the problems of easy failure of active sites, low ozone utilization rate and difficulty in complete mineralization of pollutants in the prior art. Specifically, the catalyst is based on a composite carrier composed of gamma-Al2O3 and modified sludge carbon, and manganese nitrate and cerium nitrate are loaded on the carrier; zirconium oxide stabilizer is matched to inhibit the dissolution of active components; hydroxyapatite and KH-550 composite coating are coated to block the coordination of pollutants and active sites; potassium titanium oxalate is doped to promote the decomposition of peroxide intermediates and the regeneration of oxygen vacancies; sodium carboxymethyl cellulose is added to optimize the molding and pore structure; the catalyst is prepared through composite carrier pretreatment, active component loading, composite coating, regeneration aid doping, roll granulation and stage calcination, and has significant progress in catalytic efficiency, structural stability and long-term operation effect.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of pharmaceutical wastewater treatment, in particular to a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater and a preparation method thereof. BACKGROUND

[0002] Pharmaceutical wastewater contains antibiotics, chelating agents and heterocyclic organic matters, has the characteristics of high pollutant concentration, strong toxicity and poor biodegradability, and it is difficult to achieve standard discharge by using conventional biochemical treatment processes; as one of the core means of deep treatment of pharmaceutical wastewater, the ozone catalytic oxidation technology promotes the decomposition of ozone to generate hydroxyl radicals through the synergistic effect of catalyst and ozone, and strengthens the oxidation and degradation capacity of refractory pollutants; among them, the catalyst is the core component of the technology, which needs to meet the needs of adsorbing pollutants, activating ozone and tolerating complex working conditions of wastewater, and the performance of the catalyst directly affects the treatment efficiency and operation cost, therefore, optimizing the catalyst has become the main research direction in the field.

[0003] Nikoletta Tsiarta team once published "Heterogeneous Catalytic Ozonation of Pharmaceuticals: Optimization of the Process by Response Surface Methodology" in Nanomaterials, aiming to regulate the oxygen vacancy concentration by constructing Mn-Ce bimetallic sites, and reveal the electron transfer mechanism to improve the catalytic stability; a catalyst for ozone catalytic oxidation treatment of refractory wastewater, its preparation method and use with the publication number CN109647431B, by using activated alumina as the carrier, Fe-Mn-Cu three-metal active components are loaded by impregnation-hydrothermal method, and spinel-type composite oxides are formed by regulating the calcination temperature, which realizes the improvement of ozone utilization rate and COD removal rate of refractory organic matter; a hydrophobically modified ozone catalytic oxidation catalyst and its preparation method with the publication number CN115025768A, by grafting fluorosilane hydrophobic groups on the surface of the carrier and loading active components, the effect of reducing excessive adsorption of wastewater and reducing the risk of pore blockage is realized.

[0004] However, due to the complex composition of pharmaceutical wastewater, chelating agents, humus and antibiotic degradation intermediates can easily form stable coordination compounds with catalyst active metal components, occupy Lewis acid active sites and oxygen vacancies, and humus and antibiotic degradation intermediates can accelerate the deposition of peroxide intermediates on the surface of the active site, hinder the regeneration cycle of the oxygen vacancy, and the existing catalyst lacks dynamic protection and regeneration regulation mechanism for the active site, resulting in continuous reduction of the number of active sites and gradual decline of activity during long-term operation, which cannot maintain stable catalytic efficiency. Further, the proportion of effective active sites is insufficient and unevenly distributed, not only causing ozone molecules to be difficult to be efficiently adsorbed and activated into hydroxyl radicals, resulting in low ozone utilization rate, but also weakening the contact probability of ozone, pollutants and active sites due to pore blockage, so that tetracycline and cephalosporin pollutants can only be partially oxidized and cannot be completely mineralized, which seriously restricts the deep treatment effect of pharmaceutical wastewater. SUMMARY

[0005] The technical problem to be solved by the present application is that the prior art has the disadvantage of insufficient catalytic efficiency. To solve this problem, the present application provides a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater and a preparation method thereof.

[0006] To achieve the above-mentioned purpose, the following technical scheme is adopted in the present application: A preparation method of a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater, comprising the following steps: S1: subjecting a composite carrier composed of γ-Al2O3 and modified sludge carbon to acid immersion, drying and calcination treatment to obtain a pretreated carrier; S2: dissolving active component materials in a solvent to prepare a mixed active liquid, adding the pretreated carrier, and then dispersing and drying to obtain an intermediate loaded with active components; S3: dissolving a composite coating material in a solvent to prepare a composite coating liquid, adding the intermediate loaded with active components, and then dispersing and drying to obtain an intermediate coated with a composite coating; S4: mixing a regeneration aid with the intermediate coated with a composite coating, and then adsorbing and drying to obtain an intermediate doped with a regeneration aid; and S5: adding a binder to the intermediate doped with a regeneration aid, and then shaping, pre-burning and three-stage calcination treatment, and then naturally cooling to room temperature to obtain a finished product.

[0007] Preferably, the weight ratio of γ-Al2O3 to modified sludge carbon in the composite carrier in S1 is 6:4-8:2, and the modified sludge carbon is sludge carbon activated by calcination at 500 DEG C and then crushed to 100 mesh.

[0008] Preferably, the active component materials in S2 include 8-10 parts by weight of manganese nitrate, 2-4 parts by weight of cerium nitrate and 0.3-0.7 parts by weight of zirconium oxide.

[0009] Preferably, the concentration of the mixed active liquid in S2 is 0.8 mol / L, and the solid-liquid ratio of the mixed active liquid to the pretreated carrier is 1:8.

[0010] Preferably, the composite coating material in S3 comprises 2-4 parts of hydroxyapatite and 0.3-0.7 parts of silane coupling agent KH-550 by weight.

[0011] Preferably, the pH of the composite coating solution in S3 is 5.5-6.0, and the solid-liquid ratio of the composite coating solution to the intermediate loaded with active components is 1:15.

[0012] Preferably, the regenerative aid in S4 is titanium potassium oxalate, and in the adsorption treatment, the titanium potassium oxalate is first dissolved in a 5% dilute nitric acid solution to prepare a 0.1 mol / L titanium potassium oxalate solution, and then the titanium potassium oxalate solution is mixed with the intermediate coated with the composite coating at a solid-liquid ratio of 1:10.

[0013] Preferably, the three-stage calcination in S5 comprises: the first stage is to heat to 280-320℃ at a rate of 2-3℃ / min, and keep the temperature for 1.5-2.5h; the second stage is to heat to 480-520℃ at a rate of 3-4℃ / min, and keep the temperature for 2.5-3.5h; the third stage is to heat to 630-670℃ at a rate of 4-6℃ / min, and keep the temperature for 4-6h.

[0014] Preferably, the specific surface area of the intermediate loaded with active components is greater than 180m 2 / g and the pore volume is greater than 0.6cm 3 / g, the uniformity variation coefficient of the hydroxyapatite covering of the intermediate coated with the composite coating is less than 10%, and the particle strength of the particles after the forming treatment is greater than 10MPa.

[0015] A catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater is prepared by the preparation method of the catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater.

[0016] The technical effects and advantages of the present application are as follows:

[0017] In the present application, an active site dynamic protection system of hydroxyapatite and KH-550 composite coating is constructed, which is different from the design in the prior art that lacks active site protection or the coating has weak bonding force with the carrier. Through the electrostatic repulsion effect and the layered physical barrier of hydroxyapatite, the coordination combination of pollutants and Mn-Ce active components is blocked, and at the same time, the interface bonding between the coating and the carrier is strengthened by the chemical bond bridging of KH-550, which effectively avoids the occupation of active sites by chelating agents and humic substances, solves the problem of catalytic efficiency decline caused by site failure of existing catalysts, improves the ozone activation efficiency and pollutant degradation rate, and ensures that the catalyst can still maintain stable activity under complex pharmaceutical wastewater working conditions.

[0018] In the present application, TiO2 converted by titanium potassium oxalate forms a synergistic active center with Mn-Ce, and through the Ti 4+ / Ti 3+The redox cycle efficiently decomposes peroxide intermediates, replenishes electrons to the Mn-Ce active center to promote oxygen vacancy regeneration, solves the problem that the existing catalyst oxygen vacancy regeneration is blocked, prolongs the active site cycle life, makes the catalyst continuously run while still maintaining a low activity decay rate, and improves the ozone utilization rate and pollutant mineralization rate, overcoming the problem of insufficient long-term operation performance of the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0019] The disclosure of the present application will be described with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of the present application. In the drawings, the same reference numerals are used to refer to the same parts:

[0020] Figure 1 The flowchart for preparing the catalyst of the present application is shown.

[0021] Figure 2 The long-term operation activity decay test chart of the catalyst of the present application is shown. DETAILED DESCRIPTION

[0022] It is easy to understand that, according to the technical solution of the present application, those skilled in the art can propose a plurality of structures and implementation modes which can be replaced with each other without changing the essential spirit of the present application. Therefore, the following specific embodiments and drawings are only exemplary descriptions of the technical solution of the present application, and should not be considered as the whole or as a limitation or restriction on the technical solution of the present application.

[0023] The present application provides a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater, the composition and ratio of which are shown in Table 1.

[0024]

[0025] Table 1

[0026] It should be noted that the composite carrier is composed of γ-Al2O3 and modified sludge carbon in a weight ratio of 6:4-8:2, wherein γ-Al2O3 is used as a basic carrier with a specific surface area of 200-250m 2 / g, a mesopore size of 20-50nm, and a developed mesoporous structure, which can provide sufficient active component loading sites and ensure uniform dispersion of Mn and Ce.

[0027] The modified sludge carbon is introduced after being activated by calcination at 500℃ and then crushed to 100 mesh. The main reason is that, on the one hand, the microporous structure of the modified sludge carbon can selectively adsorb antibiotic intermediates and chelating agents in the pharmaceutical wastewater, thereby improving the enrichment concentration of the pollutants on the surface of the catalyst; on the other hand, the cost of the modified sludge carbon is only one fifth of that of γ-Al2O3, which can reduce the total cost of the carrier while ensuring performance.

[0028] Manganese nitrate as the main active component is converted into MnO2 after calcination. MnO2 has a large number of Lewis acid active sites and oxygen vacancies on the surface, which can efficiently adsorb and activate ozone molecules, promote the decomposition of ozone to generate hydroxyl radicals (·OH), and at the same time, MnO2 has good catalytic oxidation activity to nitrogen-containing and sulfur-containing pollutants in pharmaceutical wastewater, which can promote the ring-opening and cleavage of heterocyclic structures.

[0029] Cerium nitrate as an auxiliary active component is converted into CeO2 after calcination. CeO2 has Ce 4+ / Ce 3+ redox cycle, which can stabilize the oxygen vacancies on the surface of MnO2 through electron transfer. Specifically, Ce 4+ can oxidize pollutants and intermediates in pharmaceutical wastewater and simultaneously assist in the activation of ozone to generate hydroxyl radicals (·OH). In this process, Ce 4+ is reduced to Ce 3+ . When the oxygen vacancies on the surface of MnO2 are consumed due to catalytic reaction, Ce 3+ supplies electrons to the defect sites of MnO2 through electron transfer, promoting the regeneration of oxygen vacancies, and at the same time, Ce 3+ is oxidized back to Ce 4+ .

[0030] Zirconia is introduced as an active stabilizer. On the one hand, zirconia can form a solid solution structure with Mn and Ce, inhibiting the dissolution of Mn 2+ and Ce 3+ through lattice stabilization effect. On the other hand, the high melting point of zirconia can improve the thermal stability of the active components, avoiding sintering and agglomeration of the active components during calcination or long-term operation, and ensuring the long-term dispersibility of the active sites.

[0031] Hydroxyapatite (HAP) is used as a coating material, and its core function is to block the coordination of pollutants and active components. HAP is rich in Ca 2+ and PO4 3- on the surface, which can inhibit the migration of carboxyl and amino-containing pollutants such as EDTA and humic substances in pharmaceutical wastewater to Mn and Ce active sites through electrostatic repulsion effect, and the layered structure of HAP can form a physical barrier on the surface of the catalyst to reduce the direct contact of pollutants with active sites.

[0032] To solve the problem of weak bonding force between hydroxyapatite coating and carrier, silane coupling agent KH-550 is introduced as a bridging agent. The siloxane group at one end of the silane coupling agent KH-550 molecule reacts with the hydroxyl group on the surface of γ-Al2O3 to form Si-O-Al covalent bond, and the amino group at the other end forms hydrogen bond with the hydroxyl group on the surface of hydroxyapatite, which improves the interfacial bonding force between the coating and the carrier through double action.

[0033] Peroxide intermediates such as hydroxyl peroxide radicals (·OOH) are easily generated in the process of ozone catalytic oxidation of pharmaceutical wastewater, which are prone to deposit on the surface of active sites to hinder the regeneration of oxygen vacancies. If this problem is not solved, introduce potassium titanium oxalate as a regeneration aid, which is converted into TiO2 by calcination. TiO2 has a redox cycle of Ti 4+ / Ti 3+ , which can quickly decompose peroxide intermediates, specifically as follows: Ti 4+ accepts the electrons of peroxide intermediates, which are efficiently decomposed into H2O and O2. In this process, Ti 4+ is reduced to Ti 3+ ; when the oxygen vacancies of the MnO2-CeO2 composite active center are consumed due to continuous activation of ozone and degradation of pollutants, Ti 3+ supplies electrons to the oxygen vacancy defects through interfacial electron transfer, promotes the regeneration of oxygen vacancies to maintain catalytic activity, and at the same time, Ti 3+ is oxidized back to Ti 4+ by ozone or hydroxyl radicals (·OH) in the reaction system; in addition, Ti elements can form synergistic sites with Mn-Ce active centers to further promote the activation of ozone.

[0034] The main reason for choosing sodium carboxymethyl cellulose (CMC) with a molecular weight of 800-1200 as an aid is that on the one hand, the adhesion of CMC can improve the mechanical strength of catalyst particles, and on the other hand, CMC can be completely decomposed during calcination, and the decomposition products have no impurity residues, and at the same time, its molecular chain can form through channels inside the catalyst to avoid the collapse of the channels during calcination.

[0035] The application also provides a preparation method of a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater.

[0036] In example 1, as shown in the reference Figure 1 , the application provides a preparation method of a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater, which specifically comprises the following steps:

[0037] S1: pretreatment of composite carrier

[0038] Take 72 parts by weight of the composite carrier, add 0.2 mol / L of nitric acid solution, the solid-liquid ratio of the composite carrier to the nitric acid solution is 1:10, stir and soak at room temperature for 4h, filter the filter cake and dry it in a blast oven at 110℃ for 12h, then transfer it to a muffle furnace, heat it to 550℃ at a rate of 5℃ / min, and keep it at this temperature for 4h, then naturally cool it to room temperature to obtain the pretreated carrier.

[0039] It should be noted that if the concentration of nitric acid solution is too low, the residual metal oxides and organic impurities on the surface of the carrier cannot be completely removed, which will affect the subsequent loading of active components; if the concentration is too high, it will corrode the mesoporous framework of γ-Al2O3, resulting in a decrease in specific surface area.

[0040] It has been verified by experiments that if the temperature is lower than 500℃ during calcination, the volatile components remaining in the modified peat will not be completely removed, which will block the pores; if the temperature is higher than 600℃, the mesoporous structure of γ-Al2O3 will collapse.

[0041] S2: Active component loading

[0042] 9 parts of manganese nitrate, 3 parts of cerium nitrate and 0.5 parts of zirconium oxide were weighed and dissolved in deionized water to prepare a 0.8 mol / L mixed active solution. The pretreated carrier was added with a solid-liquid ratio of 1:8, and placed in a constant temperature water bath at 50℃. Ultrasonic assisted impregnation was carried out at a power of 200W for 30min, and then stirring was continued for 1h. The sample was moved to a rotary evaporator and rotary evaporated at 80℃ under a vacuum degree of 0.08MPa until dryness. The intermediate loaded with active components was obtained, and the specific surface area of the intermediate was 210m 2 / g, and the pore volume was 0.75cm 3 / g.

[0043] It should be noted that if the concentration of the mixed active solution is higher than 1.0mol / L, Mn2+ and Ce3+ will agglomerate on the surface of the carrier, forming particles with a particle size of more than 100nm, which will reduce the utilization rate of active sites; if the concentration is lower than 0.6mol / L, the catalytic activity will be low.

[0044] After loading the active components, the specific surface area and pore volume of the intermediate were detected by liquid nitrogen adsorption-desorption method (BET), wherein the specific surface area was greater than 180m 2 / g, and the pore volume was greater than 0.6cm 3 / g, to ensure that the active components do not block the carrier pores.

[0045] S3: Preparation of composite coating

[0046] 3 parts of hydroxyapatite and 0.5 parts of KH-550 were weighed and dissolved in deionized water. The pH of the system was adjusted to 5.8 with 0.1mol / L phosphoric acid solution to prepare a composite coating solution. The intermediate loaded with active components was added to the composite coating solution with a solid-liquid ratio of 1:15. The sample was placed in a constant temperature water bath at 30℃ and treated with ultrasonic at a power of 150W for 1h. Stirring was continued for 3h. After filtration, the filter cake was dried in a 105℃ oven for 6h to obtain the intermediate coated with composite coating. The uniformity variation coefficient of hydroxyapatite coverage was 7.2%.

[0047] It should be noted that the pH of the composite coating solution is controlled at 5.5-6.0, within this range, HAP is in a stable colloidal state, and is not easy to precipitate, if the pH is lower than 5, HAP will react with phosphoric acid to form soluble calcium salt, lose the coating function; if the pH is higher than 6.5, it will lead to HAP colloid aggregation, coating thickness is not uniform.

[0048] After preparing the composite coating, it is necessary to use X-ray energy spectrometer (EDS) to analyze the surface of the intermediate, detect the uniformity of Ca element distribution, and the variation coefficient is required to be less than 10%, to ensure that the coating has no local missing or over-thickness.

[0049] S4: doping regeneration aid

[0050] 1.5 parts of titanium potassium oxalate were weighed and dissolved in 5% dilute nitric acid solution to prepare a 0.1 mol / L titanium potassium oxalate solution, the intermediate was coated in the solution, the solid-liquid ratio was 1:10, and the stirring was carried out at 30℃ for 2h, so that the titanium potassium oxalate was fully adsorbed on the surface and in the pores of the intermediate, after stirring, the filter cake was dried at 105℃ for 4h, and the intermediate doped with regeneration aid was obtained.

[0051] It should be noted that too low concentration of dilute nitric acid will result in insufficient solubility of titanium potassium oxalate, which cannot form a uniform solution; too high concentration will corrode the HAP coating.

[0052] S5: forming and calcination activation

[0053] 2% deionized water was added to the intermediate doped with regeneration aid, and after mixing uniformly, it was transferred into a rolling granulator, the rotating speed of the granulator was adjusted to 30r / min, the granules with a particle size of 2-3mm were prepared, and the granules were precalcined in a 120℃ oven for 3h to remove residual water and small molecular organic matter, and then the precalcined granules were transferred into a muffle furnace for three-stage calcination, the first stage was to increase the temperature from room temperature to 300℃ at a rate of 2℃ / min, and the temperature was kept for 2h; the second stage was to increase the temperature from 300℃ to 500℃ at a rate of 3℃ / min, and the temperature was kept for 3h; the third stage was to increase the temperature from 500℃ to 650℃ at a rate of 5℃ / min, and the temperature was kept for 5h; after the calcination was completed, the catalyst was naturally cooled to room temperature, and the target catalyst was obtained, and the compressive strength of the catalyst granules was 12.5MPa.

[0054] It should be noted that in the three-stage calcination, the first stage is to keep the temperature at 300℃ for 2h, which aims to remove organic matter such as CMC and KH550, to avoid rapid heating which may cause the organic matter to decompose violently and produce gas, resulting in cracks in the granules; the second stage is to keep the temperature at 500℃ for 3h, which aims to promote the preliminary crystallization of Mn and Ce active components to form stable oxide phase; the third stage is to keep the temperature at 650℃ for 5h, which makes the HAP coating and the carrier form a firm combination, and at the same time ensures that the titanium potassium oxalate is converted into TiO2, and forms a synergistic active center with Mn-Ce.

[0055] After molding, the particle strength tester is needed to detect the compressive strength of the particles, and the compressive strength is required to be greater than 10MPa, to ensure that the catalyst is not easy to break in the reactor backwash in use.

[0056] Embodiment 2 provides a preparation method of a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater, which is different from that of embodiment 1 in that:

[0057] In the active component loading in S2, the specific surface area of the intermediate for loading the active component is 192m 2 / g, and the pore volume is 0.66cm 3 / g.

[0058] In the preparation of the composite coating in S3, the amount of HAP is reduced to 2 parts, and the variation coefficient of the uniformity of hydroxyapatite coverage is 9.5%;

[0059] In the molding and calcination activation in S5, the compressive strength of the catalyst particles is 11.8MPa.

[0060] This embodiment aims to verify the influence of the uniformity of the composite coating and the loading effect of the active component on the mechanical strength of the catalyst under the condition of low-dose HAP.

[0061] Embodiment 3 provides a preparation method of a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater, which is different from that of embodiment 1 in that:

[0062] In the active component loading in S2, the specific surface area of the intermediate for loading the active component is 188m 2 / g, and the pore volume is 0.64cm 3 / g.

[0063] In the preparation of the composite coating in S3, the amount of HAP is increased to 4 parts, and the variation coefficient of the uniformity of hydroxyapatite coverage is 8.8%;

[0064] In the molding and calcination activation in S5, the compressive strength of the catalyst particles is 12.2MPa.

[0065] This embodiment aims to verify whether there is a problem of excessive coating leading to blockage of the carrier pores under the condition of high-dose HAP, and to evaluate the influence of high HAP dosage on the mechanical strength of the catalyst and the exposure of active sites.

[0066] Embodiment 4 provides a preparation method of a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater, which is different from that of embodiment 1 in that:

[0067] In the active component loading in S2, the specific surface area of the intermediate for loading the active component is 194m 2 / g, and the pore volume is 0.67cm 3 / g.

[0068] In S3, the amount of HAP is still 3 parts, and the uniformity coefficient of hydroxyapatite coverage is 7.3%;

[0069] In S4, the amount of titanium potassium oxalate is reduced to 1 part; in S5, the compressive strength of the catalyst particles is 12.3 MPa.

[0070] This example aims to verify whether the minimum effective doping amount of the regenerative additive can meet the decomposition requirements of peroxide intermediates under the condition of low-dose titanium potassium oxalate.

[0071] Example 5 provides a preparation method of a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater, which is different from example 1 in that:

[0072] In S2, the specific surface area of the intermediate loaded with active components is 193 m 2 / g, and the pore volume is 0.65 cm 3 / g;

[0073] In S3, the uniformity coefficient of hydroxyapatite coverage is 7.1%;

[0074] In S4, the amount of titanium potassium oxalate is increased to 2 parts;

[0075] In S5, the compressive strength of the catalyst particles is 12.4 MPa.

[0076] This example aims to verify whether the over-doping of the regenerative additive leads to the agglomeration of active components under the condition of high-dose titanium potassium oxalate, and to evaluate the influence of high dosage on the structural stability of the catalyst.

[0077] Example 6 provides a preparation method of a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater, which is different from example 1 in that:

[0078] In S1, the total weight of the composite carrier is reduced to 70 parts, and γ-Al2O3 and modified peat are mixed in a weight ratio of 6:4;

[0079] In S2, the specific surface area of the intermediate loaded with active components is 182 m 2 / g, and the pore volume is 0.62 cm 3 / g;

[0080] In S3, the uniformity coefficient of hydroxyapatite coverage is 7.9%;

[0081] In the shaping and calcination activation in S5, the compressive strength of the catalyst particles is 11.2 MPa.

[0082] This embodiment aims to verify whether the active component loading demand, coating uniformity and mechanical strength requirements can still be met when the total amount of the carrier is reduced and the proportion of the sludge carbon is increased.

[0083] Example 7, the embodiment provides a preparation method of a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater, which is different from example 1 in that:

[0084] In the S1 pretreatment of the composite carrier, the total weight of the composite carrier is increased to 75 parts, and the γ-Al2O3 and the modified sludge carbon are mixed in a weight ratio of 8:2;

[0085] In the S2 active component loading, the specific surface area of the intermediate loaded with the active component is 202 m 2 / g, and the pore volume is 0.72 cm 3 / g;

[0086] In the S3 preparation of the composite coating, the uniformity variation coefficient of the hydroxyapatite coverage is 6.8%;

[0087] In the shaping and calcination activation in S5, the compressive strength of the catalyst particles is 13.0 MPa.

[0088] This embodiment aims to verify the promotion effect of the carrier specific surface area, active component loading efficiency and mechanical strength when the total amount of the carrier is increased and the proportion of γ-Al2O3 is increased.

[0089] Comparative Example 1, this comparative example selects a commercially available catalyst, the main component of which is γ-Al2O3 loaded with Mn-Ce composite oxide, and the weight ratio of Mn to Ce is about 4:1.

[0090] Comparative Example 2, the embodiment provides a preparation method of a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater, which is different from example 1 in that:

[0091] The operation of S3 is omitted, that is, HAP and KH-550 are not added, and the intermediate loaded with the active component prepared in S2 is directly transferred to S4.

[0092] Comparative Example 3, the embodiment provides a preparation method of a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater, which is different from example 1 in that:

[0093] In S4, 1.5 parts of titanium potassium oxalate are replaced by the same weight parts of niobium oxalate.

[0094] Comparative Example 4, the embodiment provides a preparation method of a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater, which is different from example 1 in that:

[0095] In S5, the intermediate doped with the regeneration aid was directly added into 2% deionized water, mixed uniformly, and then dry-pressed into a shape under a pressure of 15 MPa. After shaping, no pre-burning at 120 DEG C was performed. The shaped product was heated from room temperature to 300 DEG C at a heating rate of 5 DEG C / min, and then directly heated to 650 DEG C at a heating rate of 5 DEG C / min. After 5 h of heat preservation at 650 DEG C, the product was naturally cooled to room temperature, and a target catalyst was obtained.

[0096] To verify the performance effect of the catalyst for pharmaceutical wastewater ozone catalytic oxidation treatment provided by the application, the catalysts prepared by the preparation methods of Examples 1-7 and Comparative Examples 1-4 were taken as test objects to carry out systematic tests on catalytic efficiency, structural stability and long-term operation effect. The following is a specific test scheme.

[0097] In Test Example 1, the removal rate of chemical oxygen demand (COD) (unit: %) was determined according to the standard in GB / T11914-1989 "Determination of Chemical Oxygen Demand in Water - Potassium Dichromate Method"; the ozone concentration in the outlet of the ozone generator and the tail gas of the reactor was detected respectively according to HJ504-2009 "Determination of Ozone in Water", and the ozone utilization rate (unit: %) was calculated; the TOC value of the wastewater before and after the reaction was measured according to HJ501-2009 "Determination of Total Organic Carbon in Water", and the pollutant mineralization rate (unit: %) was calculated. The specific test results are shown in Table 2.

[0098]

[0099] Table 2

[0100] As shown in Table 2, the COD removal rate, ozone utilization rate and pollutant mineralization rate of Examples 1-7 are all better than those of Comparative Examples 1-4. In Example 1, the HAP-KH550 composite coating blocks the positioning of EDTA and humus with the M-Ce active component through electrostatic repulsion, and at the same time, the Ti 4+ / Ti 3+ redox cycle efficiently decomposes the hydroxyl peroxide radical (・OOH) intermediate, and cooperates with the Mn-Ce-Ti to activate ozone, thereby realizing efficient catalysis. In Example 7, the proportion of γ-Al2O3 is increased, the specific surface area reaches 220 m 2 / g, and the exposure amount of active sites is increased, so the efficiency is optimal. In Example 6, the proportion of modified peat is too high, the specific surface area of the carrier is reduced to 195 m 2 / g, and the active component is insufficiently loaded, so the efficiency is the lowest. In Comparative Example 2, the active component is directly exposed and the positioning occupancy rate is increased by more than 50%, so the COD removal rate is only 72.1%; in Comparative Example 3, the Nb 5+ / Nb 4+ redox cycle rate is lower than that of Ti 4+ / Ti 3+, the intermediate decomposition efficiency decreased by 30%, and the mineralization rate was only 50.2%; the active component of Comparative Example 4 was agglomerated due to particle cracking, the contact probability of ozone with active sites decreased by 40%, and the efficiency was the worst.

[0101] In Test Example 2, the specific surface area of fresh catalyst and catalyst after 200 hours of continuous operation was tested by liquid nitrogen adsorption-desorption method, and the specific surface area change rate (unit: %) was calculated; according to HJ700-2014 "Determination of 65 elements in water quality", the reaction effluent after 200 hours of continuous operation was collected, acidified and then tested for Mn and Ce concentrations by ICP-MS, and the catalyst leaching amount per unit mass (unit: mg / g) was calculated; according to GB / T31862-2015 "Particle catalyst mechanical strength test method", 10 catalyst particles were randomly selected, the single particle crushing resistance was tested by a particle strength tester, and the average value was taken as the particle crushing strength (unit: MPa). The specific test results are shown in Table 3.

[0102]

[0103] Table 3

[0104] The data show that the structural stability of Examples 1-7 is better than that of Comparative Examples, ZrO2 forms a solid solution structure with Mn-Ce to inhibit the leaching of active components; HAP-KH550 composite coating forms a physical barrier to reduce the erosion of hydroxyl radicals (·OH) on the carrier skeleton, so the specific surface area change rate is less than 14%; rolling granulation combined with three-stage calcination avoids stress concentration in the particles and ensures that the crushing strength is always greater than 11 MPa; Example 7 has the lowest Mn leaching amount and the highest crushing strength because the proportion of γ-Al2O3 is high and the mechanical support of the carrier is strong; the Mn leaching amount of Example 6 increases to 0.15 mg / g because the proportion of modified sludge carbon is high and the compactness of the carrier structure decreases; the Mn leaching amount of Comparative Example 2 increases to 0.31 mg / g because the active component is exposed to a strong oxidative environment; the Ce leaching amount of Comparative Example 3 reaches 0.18 mg / g because Nb and Mn-Ce solid solution have poor stability; the specific surface area change rate of Comparative Example 4 reaches 25.3% and the crushing strength is only 8.2 MPa because dry pressing causes internal cracks in the particles and the active component sintering during calcination.

[0105] In Test Example 3, pharmaceutical wastewater was continuously fed and operated for 200 hours, and the COD removal rate was tested every 20 hours during the operation, and the long-term operation activity decay rate (unit: %) was calculated based on the test results. The specific test results are shown in Table 4 and Figure 2 .

[0106]

[0107] Table 4

[0108] Table 4 and Figure 2Data shows that the activity decay rate of Examples 1, 5, and 7 was only 7.1%-7.5% because the HAP coating continuously blocked pollutant coordination and potassium titanium oxalate continuously decomposed intermediates, ensuring oxygen vacancy regeneration cycle. In Example 6, the initial number of active sites was insufficient, and the pollutants adsorbed by sludge were easily released slowly to occupy sites, so the decay rate increased to 13.3%. In Comparative Example 2, because the active components were continuously coordinated and occupied and there was no barrier protection, the number of active sites decreased by 55% after 200 hours, with a decay rate of 21.1%. In Comparative Example 3, because the decomposition efficiency of Nb intermediates decreased with operation, oxygen vacancy regeneration was hindered, and the decay rate was 19.3%. In Comparative Example 4, because particle cracks caused the active components to continuously dissolve, the decay rate reached 23.5%.

[0109] In summary, compared with the prior art, the present invention has made significant progress in catalytic efficiency, structural stability and long-term operation.

[0110] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A method for preparing a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater, characterized in that, Includes the following steps: S1: The composite carrier composed of γ-Al2O3 and modified sludge carbon is subjected to acid leaching, drying and calcination to obtain a pretreated carrier; S2: Manganese nitrate, cerium nitrate and zirconium oxide are dissolved in a solvent to prepare a mixed active solution. A pretreated carrier is added, and after dispersion and drying, an intermediate loaded with active components is obtained. S3: Dissolve hydroxyapatite and silane coupling agent KH-550 in a solvent to prepare a composite coating liquid, add an intermediate loaded with active components, and obtain an intermediate coated with a composite coating after dispersion and drying. S4: Potassium titanium oxalate is mixed with an intermediate coated with a composite coating, and after adsorption and drying, an intermediate doped with potassium titanium oxalate is obtained. S5: Add a binder to the intermediate doped with potassium titanium oxalate, and after molding, pre-firing and three-stage calcination, naturally cool to room temperature to obtain the finished product.

2. The method for preparing a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater according to claim 1, characterized in that: The weight ratio of γ-Al2O3 to modified sludge carbon in the composite carrier described in S1 is 6:4-8:

2. The modified sludge carbon is sludge carbon that has been activated by calcination at 500℃ and then pulverized to 100 mesh.

3. The method for preparing a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater according to claim 1, characterized in that: The amounts of manganese nitrate, cerium nitrate, and zirconium oxide mentioned in S2, by weight, are 8-10 parts manganese nitrate, 2-4 parts cerium nitrate, and 0.3-0.7 parts zirconium oxide.

4. The method for preparing a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater according to claim 1, characterized in that: The concentration of the mixed active liquid in S2 is 0.8 mol / L, and the mass-to-volume ratio of the pretreated carrier to the mixed active liquid is 1 g: 8 mL.

5. The method for preparing a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater according to claim 1, characterized in that: The hydroxyapatite and silane coupling agent KH-550 mentioned in S3 are used in the following amounts by weight: 2-4 parts hydroxyapatite and 0.3-0.7 parts silane coupling agent KH-550.

6. The method for preparing a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater according to claim 1, characterized in that: The pH of the composite coating liquid in S3 is 5.5-6.0, and the mass-to-volume ratio of the intermediate loaded with active components to the composite coating liquid is 1g:15mL.

7. The method for preparing a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater according to claim 1, characterized in that: In the S4 adsorption process, potassium titanium oxalate is first dissolved in 5% dilute nitric acid solution to prepare a 0.1 mol / L potassium titanium oxalate solution. Then, the intermediate coated with the composite coating is mixed with the potassium titanium oxalate solution at a mass-to-volume ratio of 1 g: 10 mL.

8. The method for preparing a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater according to claim 1, characterized in that: The three-stage roasting described in S5 includes: the first stage of heating to 280-320℃ at 2-3℃ / min and holding for 1.5-2.5h; the second stage of heating to 480-520℃ at 3-4℃ / min and holding for 2.5-3.5h; and the third stage of heating to 630-670℃ at 4-6℃ / min and holding for 4-6h.

9. The method for preparing a catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater according to claim 1, characterized in that: The specific surface area of ​​the intermediate supporting the active component must be greater than 180 m². 2 / g and pore volume greater than 0.6cm 3 / g, the coefficient of variation of uniformity of hydroxyapatite intermediate for coating composite coating should be less than 10%, and the particle strength after molding treatment should be greater than 10MPa.

10. A catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater, characterized in that, It is prepared by the method for preparing the catalyst for ozone catalytic oxidation treatment of pharmaceutical wastewater according to any one of claims 1-9.

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