Supported two-component metal oxide catalyst for advanced treatment of petrochemical wastewater and method for preparing same

Abstract

A method for preparing a supported two-component metal oxide ozone catalytic oxidation catalyst for an advanced treatment of a petrochemical wastewater is provided. The supported two-component metal-oxide ozone catalytic oxidation catalyst is prepared from commercially-available active alumina balls by the steps of carrier activation, impregnating liquid preparation, carrier impregnation, catalyst roasting, and catalyst cleaning. The supported two-component metal oxide ozone catalytic oxidation catalyst has product stability, is reusable, and is of significance in application of ozone catalytic oxidation technologies as well as energy conservation and consumption reduction for petrochemical wastewater treatment plants.

Claims

1. A method for preparing a supported two-component metal oxide ozone catalytic oxidation catalyst, comprising the following steps: (a) carrier activation: cleaning active alumina balls with deionized water to neutrality to obtain cleaned active alumina balls, then activating the cleaned active alumina balls with a hydrochloric acid solution to obtain activated active alumina balls, then rinsing the activated active alumina balls to neutrality with the deionized water again to obtain rinsed active alumina balls, and drying the rinsed active alumina balls to obtain an activated alumina carrier particle, wherein the active alumina balls have a particle size of 2-5 mm; (b) impregnating liquid preparation: preparing a mixed solution of copper nitrate and manganese nitrate in concentration, adding EDTA-2Na to the mixed solution to obtain a resulting solution, and evenly stirring the resulting solution to obtain an impregnating liquid; (c) carrier impregnation: impregnating the activated alumina carrier particle in the impregnating liquid, airing the activated alumina carrier particle after an impregnation, and then further heating and drying the activated alumina carrier particle to obtain an impregnated and dried catalyst; (d) catalyst roasting: roasting the impregnated and dried catalyst to obtain a roasted product; and (e) catalyst cleaning: washing the roasted product with the deionized water and drying to obtain the supported two-component metal oxide ozone catalytic oxidation catalyst.

2. The method according to claim 1, wherein the hydrochloric acid solution in step (a) has a concentration of 0.1 mol/L, and an activating time is 2 hours.

3. The method according to claim 1, wherein the activated alumina carrier particle in step (a) has a particle size of 2-5 mm.

4. The method for to claim 1, wherein in step (b), the mixed solution is prepared by formulating a copper nitrate solution with a concentration of 0.10-0.16 mol/L and a manganese nitrate solution with a concentration of 0.02-0.04 mol/L and mixing the copper nitrate solution and the manganese nitrate solution at 1:1.

5. The method according to claim 1, wherein the EDTA-2Na in the impregnating liquid obtained in step (b) has a concentration of 0.1 mol/L.

6. The method according to claim 1, wherein a molar ratio of copper ions to manganese ions in the impregnating liquid obtained in step (b) is 4:1.

7. The method according to claim 1, wherein in step (c), the activated alumina carrier particle is impregnated in the impregnating liquid for 24 hours at an impregnation temperature of 40° C.

8. The method according to claim 1, wherein in step (c), 100 mL of the impregnating liquid is required per 100 g of the activated alumina carrier particle.

9. The method according to claim 1, wherein in step (d), the impregnated and dried catalyst is roasted in a muffle furnace at 350-400° C. for 2 hours to obtain the roasted product.

10. A catalyst prepared by the method for preparing the supported two-component metal oxide ozone catalytic oxidation catalyst according to of claim 1.

11. The catalyst according to claim 10, wherein the hydrochloric acid solution in step (a) has a concentration of 0.1 mol/L, and an activating time is 2 hours.

12. The catalyst according to claim 10, wherein the activated alumina carrier particle in step (a) has a particle size of 2-5 mm.

13. The catalyst according to claim 10, wherein in step (b), the mixed solution is prepared by formulating a copper nitrate solution with a concentration of 0.10-0.16 mol/L and a manganese nitrate solution with a concentration of 0.02-0.04 mol/L and mixing the copper nitrate solution and the manganese nitrate solution at 1:1.

14. The catalyst according to claim 10, wherein the EDTA-2Na in the impregnating liquid obtained in step (b) has a concentration of 0.1 mol/L.

15. The catalyst according to claim 10, wherein a molar ratio of copper ions to manganese ions in the impregnating liquid obtained in step (b) is 4:1.

16. The catalyst according to claim 10, wherein in step (c), the activated alumina carrier particle is impregnated in the impregnating liquid for 24 hours at an impregnation temperature of 40° C.

17. The catalyst according to claim 10, wherein in step (c), 100 mL of the impregnating liquid is required per 100 g of the activated alumina carrier particle.

18. The catalyst according to claim 10, wherein in step (d), the impregnated and dried catalyst is roasted in a muffle furnace at 350-400° C. for 2 hours to obtain the roasted product.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows influences of different molar ratios of active components on TOC removal rates of secondary petrochemical effluent via ozone catalytic oxidation.

(2) FIG. 2 shows comparison of TOC removal effects of the catalyst prepared according to the present invention and the general commercially-available ozone catalytic oxidizing agent for treatment of secondary petrochemical effluent on secondary petrochemical effluent.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(3) In the present invention, different metal active components are selected to prepare the catalysts according to different molar ratios. Specifically, the method is as follows:

(4) Step (1): with commercially-available active alumina balls as a carrier having a particle size of 3 mm, the active alumina balls were cleaned with deionized water to neutrality, then activated with a 0.1 mol/L hydrochloric acid solution for 2 h, then rinsed to neutrality with deionized water again, and dried at 105° C. for 12 h for later use.

(5) Step (2): impregnating liquids were prepared with a combination of Mn.sup.2+ ions and Cu.sup.2+ ions, a combination of Cu.sup.2+ ions and Fe.sup.3+ ions, and a combination of Zn.sup.2+ ions and Cu.sup.2+ ions as active components of the catalyst respectively. In the above ion combinations, the sum of molar weights of the two ions in each of the combination of Mn.sup.2+ ions and Cu.sup.2+ ions, the combination of Cu.sup.2+ ions and Fe.sup.3+ ions, and the combination of Zn.sup.2+ ions and Cu.sup.2+ ions was 0.2 mol. Mn(NO.sub.3).sub.2, Cu(NO.sub.3).sub.2, Fe(NO.sub.3).sub.3, and Zn(NO.sub.3).sub.2 were weighed in corresponding weights according to the molar ratios of the corresponding compound ions being 1:0, 0.9:0.1, 0.8:0.2, 0.7:0.3, 0.6:0.4, 0.5:0.5, 0.4:0.6, 0.3:0.7, 0.2:0.8, 0.1:0.9 and 0:1. Salts weighed at the above ratios were added into corresponding containers, Na.sub.2EDTA was further added, and water was added till 1 L for dilution to obtain the impregnating liquids. The addition amount of Na.sub.2EDTA was 33.6 g.

(6) Step (3): 1 kg of γ-Al.sub.2O.sub.3 carrier activated in Step (1) of the present invention was slowly added to the above prepared various ion impregnating liquids to be impregnated for 24 h, and then the impregnated particles were taken out, aired for 24 h, dried for 12 h at 105° C., and then roasted in a muffle furnace at 350-400° C. for 2 h to prepare different two-component supported catalysts.

(7) The above various catalysts were used in an ozone-catalyzed degradation test of petrochemical wastewater. The above ozone-catalyzed degradation test was carried out in a glass reactor. The dosage of ozone was controlled by an ozone concentration detector and a flow meter, wherein the dosage of ozone was 0.5 mg/min and the dosage of the catalyst was 100 g/L. An effluent from a secondary sedimentation tank of a comprehensive wastewater plant in a petrochemical industrial part was taken as a treatment object. Samples were taken after 60 min of reaction to measure TOC values. The influences of molar ratios between the active components of the catalysts on TOC removal rate and removal amount of the catalysts against the secondary petrochemical effluent are shown in FIG. 1.

(8) It can be seen from FIG. 1 that different multi-metal active components have different influences on TOC removal rate of wastewater via ozone catalytic oxidation under the condition of different molar ratios. When a molar ratio of Cu:Mn is 4:1, the TOC removal rate of wastewater via ozone catalytic oxidation is the highest, which is up to 35%. Therefore, this study finally determines that the active components of the catalyst are Cu and Mn in a molar ratio of 4:1.

(9) Further, different commercially-available ozone catalytic oxidizing agents for the treatment of secondary petrochemical effluent were selected. The above catalysts were purchased from four provinces across China and named Shandong 1 #, Shandong 2 #, Jiangsu 1 #, Jiangxi 1 #, and Guangdong 1 #. Evaluation of catalyst performance with ozone-catalyzed degradation test: the test was carried out in a glass reactor, the dosage of ozone was controlled through an ozone concentration detector and a flow meter, and the loading level of the catalyst was 25 g/L; and an effluent from a secondary sedimentation tank of a comprehensive wastewater plant in a petrochemical industrial part was taken as a treatment object. The results are as shown in FIG. 2. Based on the results in FIG. 2, it is shown that the catalyst of the present invention is significantly superior than the general commercially-available catalysts used for secondary petrochemical effluent treatment.

(10) The wastewater used in the present application was taken from the effluent of the second sedimentation tank, i.e., the secondary effluent of the petrochemical wastewater, of a wastewater treatment plant with a treatment scale of 2600 m.sup.3/h in a petrochemical industrial park in China. The industrial influent of this comprehensive wastewater treatment plant was primarily treated industrial wastewater emitted from more than 70 sets of production facilities in oil refineries, pesticide plants, acrylonitrile plants, calcium carbide plants, fertilizer plants, synthetic resin plants and other plates subordinate to petrochemical companies, with a volume of about 2100 m.sup.3/h. The secondary biological treatment process of this wastewater plant was hydrolysis acidification-AO. The secondary biochemically-treated effluent was complex, and each water quality index has a wide range of fluctuation, with a relative standard deviation of 0.4-25.1% (n=60). The properties of the effluent are shown in Table 1. As can be known from the table, the secondary effluent of the petrochemical wastewater is weakly alkaline, with an average COD concentration of about 80 mg/L, a BOD.sub.5 concentration of 10 mg/L, a B/C value of less than 0.3, and extremely low biodegradability. Moreover, chloride ions and sulfate radicals are high in concentration, and are both quenchers for free radicals in the ozone oxidation system, which greatly limit the improvement of the catalytic oxidation effect of ozone.

(11) The characteristic organic matters such as refractory organic matters in the biochemically-treated effluent of the petrochemical wastewater are complex, and their properties are shown in Table 2. As can be known from the table, the organic matters in the wastewater mainly include benzenes, alkanes, heterocycles, alcohols, esters, ketones, acids, nitriles, organic amines and other organic matters. Among them, three types of organic matters, including benzenes, hydrocarbons and heterocycles, are difficult to microbiologically degrade, contain 10-50 characteristic organic matters and have an average concentration which is at a high level of 100-600 μg/L. These organic matters in the biochemically-treated effluent of the petrochemical wastewater have stable chemical structures and are organic pollutants that are difficult to biodegrade.

(12) TABLE-US-00001 TABLE 1 Partial conventional water quality indexes for secondary effluent of a petrochemical wastewater plant Parameter Concentration Unit Parameter Concentration Unit pH 7.3 ± 0.4 TN 9.3 ± 4.0 mg/L Chroma 55 ± 5  Degree TP 0.7 ± 0.5 mg/L SS 27.6 ± 4.9  mg/L NO.sub.3.sup.−-N 15.0 ± 2.8  mg/L COD.sub.Cr 85.7 ± 25.5 mg/L DO 5.0 ± 0.6 mg/L BOD.sub.5 4.12 ± 1.98 mg/L Cl.sup.− 379.5 ± 80.0  mg/L TOC 23.5 ± 5.3  mg/L PO.sub.4.sup.2− 0.4 ± 0.2 mg/L NH.sub.4.sup.+-N 3.5 ± 6.8 mg/L SO.sub.4.sup.2− 938 ± 28  mg/L

(13) TABLE-US-00002 TABLE 2 Analysis results of types and concentrations of characteristic organic matters of biochemically-treated effluent of petrochemical wastewater Type of organic matter Quantity (of types) Average concentration (pg/L) Benzenes 47 598.22 Hydrocarbons 10 123.33 Heterocycles 18 111.70 Alcohols 8 50.00 Esters 5 21.24 Ketones 7 44.89 Acids 2 3.34 Nitriles 3 23.38 Organic amines 9 59.44 Miscellaneous 7 297.24

(14) The embodiments described above merely describe the preferred embodiments of the present invention, but are not intended to limit the scope of the present invention. Various variations and improvements made to the technical solutions of the present invention by those of ordinary skills in the art without departing from the design and spirit of the present invention shall fall within the protection scope defined by the claims of the present invention.