Targeted fenton degradation method for high organic matter and refractory petroleum refining wastewater and application

Abstract

The application discloses a targeted Fenton degradation method for high-organic-content and hard-to-degrade petroleum refining wastewater and application, and comprises the following steps: introducing the wastewater into a flocculation sedimentation tank, adding 100-500 ppm of a polyaluminum chloride water solution through a first water inlet, adding 1-10 ppm of a polyacrylamide water solution through a second water inlet, and removing most of the suspended matters in the form of sludge after sedimentation; introducing supernatant after the flocculation sedimentation tank treatment into a targeted Fenton reaction kettle, adding an oxidant and a perovskite catalyst for reaction, and the reaction temperature is 80-200 DEG C, and the reaction time is 30-120 min. The targeted Fenton degradation technology is used to treat the high-organic-content and hard-to-degrade petroleum refining wastewater, the removal rates of COD, suspended solids SS, turbidity, color and the like in the high-organic-content and hard-to-degrade petroleum refining wastewater are effectively improved while high efficiency and greenness are ensured.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, and in particular to a targeted Fenton degradation method and its application for petroleum refining wastewater with high organic content and difficult degradation. Background Technology

[0002] The petroleum industry and refineries play a crucial role in rapid economic growth. This requires the refining of petroleum to obtain corresponding petrochemical products, which generates a series of petroleum refining wastewaters. These wastewaters include not only wastewater from petroleum refining and production processes (including the reprocessing of organic matter using petroleum as raw material through cracking, refining, fractionation, etc.), but also process condensate and other water used in the refinery area (including flushing water, domestic sewage, etc.). This type of wastewater exhibits significant variations in volume and quality, complex composition, and high concentrations of organic pollutants, many of which are highly toxic and difficult to degrade. These include petroleum hydrocarbons (including saturated acyclic hydrocarbons, cyclic hydrocarbons, olefins, aromatics, and non-hydrocarbons), phenols (such as cresol, bisphenol A, etc.), sulfides, cyanides, nitrogen-containing organic matter, heavy metals (such as chromium, iron, nickel, copper, molybdenum, etc.), and suspended solids. Petroleum refining wastewater often contains many highly toxic polycyclic aromatic hydrocarbons (PAHs), which are more persistent in the environment and difficult to completely degrade. Toxic and harmful substances in petroleum refining wastewater enter the soil and cause direct or indirect harm to human health and the environment through bioaccumulation in the ecosystem.

[0003] Currently, the main methods for treating petroleum refining wastewater include biological methods and physicochemical treatment methods.

[0004] Biological treatment utilizes microorganisms to complete the degradation process, which is thorough and does not produce secondary pollution. Typical processes include oxidation ditch processes, anoxic / aerobic processes, sequencing batch reactors (SBRs), and aerated biological filters. Although biological treatment processes can achieve COD removal rates of 60% to 90%, they also have drawbacks such as long start-up times, susceptibility to sludge bulking, weak system resistance to shock loads, and sludge loss.

[0005] Physicochemical treatment methods are often used as pretreatment or advanced treatment units for petroleum refining wastewater. Commonly used physicochemical treatment methods include flocculation, advanced oxidation technologies (traditional Fenton oxidation, ozone catalytic oxidation, wet oxidation, etc.), air flotation, electrochemical processes, and membrane separation technologies.

[0006] Advanced oxidation processes (AOPs) are widely used to treat petroleum refining wastewater due to their strong oxidizing power, good treatment effect, thorough oxidation, and fast reaction speed. However, AOPs still have some drawbacks. For example, traditional Fenton technology has harsh reaction conditions, produces a large amount of sludge, and is prone to equipment corrosion; ozone catalytic oxidation has a long reaction time, high cost, and is difficult to operate and maintain; wet oxidation technology has a high reaction temperature and high oxygen partial pressure, and is also difficult to operate and maintain.

[0007] In summary, there is currently a lack of efficient, green, and energy-saving treatment methods for petroleum refining wastewater with high organic content and poor degradation. Summary of the Invention

[0008] To address the technical problems existing in the prior art, this invention provides a targeted Fenton degradation method for petroleum refining wastewater with high organic matter content and difficult degradation, thereby solving the problem of difficult treatment of such wastewater in the prior art. The method includes the following steps:

[0009] Wastewater is introduced into a flocculation sedimentation tank. 100-500 ppm of polyaluminum chloride aqueous solution is added through the first inlet tank, and 1-10 ppm of polyacrylamide aqueous solution is added through the second inlet tank. After the reaction, most of the suspended solids are removed as bottom sludge by sedimentation.

[0010] The supernatant after flocculation sedimentation tank treatment is introduced into a targeted Fenton reactor, and an oxidant and a perovskite catalyst are added for reaction. The reaction temperature is 80-200℃ and the reaction time is 30-120 min.

[0011] Furthermore, the catalyst is a perovskite-type catalyst ABO3, specifically a metal oxide, wherein the A-site is either La or Sr, and the B-site is either Cu, Fe, or Mo, as detailed below. Figure 1 .

[0012] Furthermore, the catalyst is a doped perovskite catalyst AlA2BO3 or AB1B2O3, wherein the A1 and A2 sites are one of La or Sr, and the B1 and B2 sites are one of Cu, Fe or Mo. The A and B sites are not doped simultaneously.

[0013] Furthermore, the catalyst is supported on SiO2, Al2O3, or activated carbon.

[0014] Furthermore, the oxidant is hydrogen peroxide or persulfate oxide.

[0015] Furthermore, the dosage of the perovskite catalyst is 5–15 g / L.

[0016] Furthermore, the dosage of the oxidant needs to be theoretically calculated based on the COD value of petroleum refining wastewater with high organic matter content and difficult degradation.

[0017] Furthermore, the preparation method of the undoped and unloaded catalyst is as follows: citric acid and EDTA are added sequentially to deionized water, and ammonia is added until the solution becomes clear; substances containing A-site elements and substances containing B-site elements are added sequentially to the solution, stirred to dissolve, and then ammonia is added to adjust the pH to between 8.5 and 8.8; the mixture is stirred at a constant temperature of 70-80℃ until it reaches a gel state, and then dried, calcined, and ground to obtain the catalyst; the molar ratio of citric acid, EDTA, substances containing A-site elements, and substances containing B-site elements is 15-20:8-12:5:5.

[0018] Further, the preparation method of the doped perovskite catalyst is as follows: citric acid and EDTA are added sequentially to deionized water, and ammonia is added until the solution becomes clear; substances containing A1 / A2 / B site elements or substances containing A / B1 / B2 site elements are added sequentially to the solution, stirred to dissolve, and then ammonia is added to adjust the pH to between 8.5 and 8.8; the mixture is stirred at a constant temperature of 70-80℃ until it reaches a gel state, and then dried, calcined, and ground to obtain the catalyst; the molar ratio of citric acid, EDTA, substances containing A or A1 / A2 site elements, and substances containing B or B1 / B2 site elements is 15-20:8-12:5:5.

[0019] This invention also discloses the application of the above-mentioned targeted Fenton degradation method for the recalcitrant petroleum refining wastewater with high organic matter content. The recalcitrant petroleum refining wastewater treated by this method contains aromatic and heterocyclic organic compounds, with a COD of 3800-4500 mg / L, a TOC of 1200-1300 mg / L, a suspended solids (SS) of 100-200 mg / L, a turbidity of 200-250 NTU, and a pH of 7.5-8.5.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This invention provides a targeted Fenton degradation technology for petroleum refining wastewater with high organic content and poor degradation resistance. Compared with traditional Fenton, wet air oxidation (WAO), and catalytic wet air oxidation (CWAO) technologies, targeted Fenton degradation technology can efficiently remove high concentrations of recalcitrant organic matter from petroleum refining wastewater and reduce the biotoxicity of the effluent within a lower temperature range. It is particularly effective for the ring-opening or chain-breaking of polycyclic aromatic hydrocarbons or other heterocyclic macromolecular organics. Specifically, during the reaction, oxygen vacancies or multiple active catalytic centers are formed on the catalyst surface, promoting the efficient generation of more oxidizing active species (such as hydroxyl radicals ·OH and superoxide radicals O2) from hydrogen peroxide. ·— This technology (etc.) causes polycyclic aromatic hydrocarbons or other heterocyclic macromolecular organics to undergo ring-opening or chain breaking, thereby being oxidized into small molecule organics or even directly mineralized; at the same time, the targeted Fenton degradation reaction produces clear water with almost zero suspended solids (SS), color, and turbidity.

[0022] Compared to homogeneous catalysts, the self-made ABO3 perovskite catalyst has better catalytic effect, stable structure, and can be recycled and reused. Even after multiple cycles, it still has a good effect on treating petroleum refining wastewater with high organic matter content and difficult degradation.

[0023] This invention can achieve the standard discharge of petroleum refining wastewater with high organic matter content and poor degradation, and has the advantages of high efficiency and energy saving, low operating cost and simple process. Attached Figure Description

[0024] Figure 1 A schematic diagram of the structure of the perovskite-type catalyst ABO3;

[0025] Figure 2 A flowchart of a targeted Fenton degradation method for petroleum refining wastewater with high organic content and difficult degradation. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0027] This invention provides a targeted Fenton degradation method for petroleum refining wastewater with high organic content and poor degradation resistance, comprising the following steps:

[0028] Wastewater is introduced into a flocculation sedimentation tank. 100-500 ppm of polyaluminum chloride aqueous solution is added through the first inlet tank, and 1-10 ppm of polyacrylamide aqueous solution is added through the second inlet tank. After the reaction, most of the suspended solids are removed as bottom sludge by sedimentation.

[0029] The supernatant after flocculation and sedimentation is introduced into a targeted Fenton reactor, where an oxidant and a perovskite catalyst are added for reaction. The reaction temperature is 80–200℃, and the reaction time is 30–120 min. The catalyst is a perovskite-type catalyst ABO3, specifically a metal oxide, wherein the A-site is either La or Sr, and the B-site is either Cu, Fe, or Mo. The catalyst can be supported on SiO2, Al2O3, or activated carbon; the oxidant is hydrogen peroxide or persulfate oxide; the perovskite catalyst dosage is 5–15 g / L; the oxidant dosage needs to be theoretically calculated based on the COD value of the high-organic-content, recalcitrant petroleum refining wastewater.

[0030] The preparation method of the undoped and unloaded catalyst is as follows: citric acid and EDTA are added to deionized water one after another, and ammonia is added until the solution becomes clear; substances containing A-site elements and substances containing B-site elements are added to the solution one after another, stirred and dissolved, and then ammonia is added to adjust the pH to between 8.5 and 8.8; the solution is stirred at a constant temperature of 70 to 80°C until it reaches a gel state, and then dried, calcined and ground to obtain the catalyst; the molar ratio of citric acid, EDTA, substances containing A-site elements and substances containing B-site elements is 15 to 20: 8 to 12: 5: 5.

[0031] Optionally, the catalyst is a doped perovskite catalyst AlA2BO3 or AB1B2O3, wherein the A1 and A2 sites are composed of La or Sr, and the B1 and B2 sites are composed of Cu, Fe, or Mo. The preparation method of the doped perovskite catalyst is as follows: citric acid and EDTA are added sequentially to deionized water, and ammonia is added until the solution becomes clear; substances containing A1 / A2 / B site elements or substances containing A / B1 / B2 site elements are added sequentially to the solution, stirred to dissolve, and then ammonia is added to adjust the pH to between 8.5 and 8.8; the mixture is stirred at a constant temperature of 70–80℃ until it reaches a gel state, and then dried, calcined, and ground to obtain the catalyst; the molar ratio of citric acid, EDTA, substances containing A or A1 / A2 site elements, and substances containing B or B1 / B2 site elements is 15–20:8–12:5:5.

[0032] The method treats recalcitrant petroleum refining wastewater containing aromatic and heterocyclic organic compounds. The wastewater has a COD of 3800–4500 mg / L, a TOC of 1200–1300 mg / L, a suspended solids (SS) of 100–200 mg / L, a turbidity of 200–250 NTU, and a pH of 7.5–8.5.

[0033] The targeted Fenton degradation method of this invention achieves compliant discharge of petroleum refining wastewater with high organic matter content and poor degradation resistance. It solves problems in existing technologies such as harsh reaction conditions, high catalyst metal ion dissolution rates, highly toxic intermediate products, incomplete treatment, and high effluent color. It can treat petroleum refining wastewater with organic matter concentrations around 4100 mg / L, containing polycyclic aromatic hydrocarbons (PAHs) or other heterocyclic macromolecular organics that are difficult to degrade. In the targeted Fenton degradation system, the catalyst forms multiple active catalytic centers in situ, mediating the efficient generation of highly oxidizing active species from hydrogen peroxide. This causes PAHs or other heterocyclic macromolecular organics to undergo ring-opening or chain breaking, thereby being oxidized into smaller, less toxic organic molecules or directly mineralized. Specifically, as the reaction proceeds, oxygen vacancies or multiple active catalytic centers are formed on the catalyst surface, promoting the efficient generation of even more oxidizing active species from hydrogen peroxide, such as hydroxyl radicals (·OH) and superoxide radicals (O2). ·— wait.

[0034] The wastewater used in Examples 1-4 of this invention, after GC-MS analysis, mainly contained 21 kinds of organic compounds, including aromatic and other heterocyclic organic compounds, among which the main functional groups were carbonyl, hydroxyl, amide, ether bond, etc.; specifically cyclopentanone, cyclohexanone, 3,4-dimethyl-2-cyclopenten-1-one, D-limonene, 2-ethyl-1-hexanol, benzocyclopropene, acetophenone, 5-norbornene-2-methanol, naphthalene, 9-oxatetracyclo[5] [3.1.02,6.08,10] Undec-3-ene, 1-hydroxydicyclopentadiene, lactone-3a,4,7,7a-tetrahydro-4,7-methylindanone, 3-methylfuran, hydantoin, 2-methyl-2,4-pentanediol, 3-methyl-2-cyclopenten-1-one, aniline, phenol, sulfolane, α-hydroxy-α-methylbenzylphenyl ketone, etc. (Some recalcitrant organic compounds may be present in the raw water but are difficult to extract).

[0035] Example 1

[0036] This embodiment uses an undoped and unsupported ABO3 catalyst.

[0037] Wastewater is introduced into a flocculation sedimentation tank. 300 ppm of polyaluminum chloride aqueous solution is added through the first inlet tank, and 4 ppm of polyacrylamide aqueous solution is added through the second inlet tank. After the reaction, most of the suspended solids are removed.

[0038] The supernatant after flocculation and sedimentation was introduced into a targeted Fenton reactor, and 2.14 mol / L of oxidant H2O2 and 5 g / L of catalyst La were added. 0.9 CuO3 was reacted at a temperature of 180℃ for 60 minutes.

[0039] La 0.9 The synthesis method of CuO3: First, 3.36 g of citric acid and 2.92 g of EDTA were added sequentially to 80 mL of deionized water, followed by the addition of ammonia until the solution became clear. Next, 2.05 g of lanthanum nitrate hexahydrate and 1.27 g of copper nitrate trihydrate were added sequentially to the solution, stirred until dissolved, and then ammonia was added to adjust the pH to 8.5. The beaker containing this mixed solution was then transferred to an oil bath and stirred at a constant temperature of 70 °C until a gel state was reached. The solution was then transferred to an evaporating dish and dried in a forced-air drying oven for 24 h. After drying, the solution was transferred to a muffle furnace and calcined at 700 °C for 7 h. Finally, the catalyst La was obtained by grinding. 0.9 CuO3.

[0040] Example 2

[0041] The catalyst La from Example 1 0.9 CuO3 was supported on SiO2 to obtain the supported ABO3 catalyst used in this embodiment.

[0042] Wastewater is introduced into a flocculation sedimentation tank. 300 ppm of polyaluminum chloride aqueous solution is added through the first inlet tank, and 4 ppm of polyacrylamide aqueous solution is added through the second inlet tank. After the reaction with SiO2, most of the suspended solids are removed.

[0043] The supernatant after flocculation and sedimentation was introduced into a targeted Fenton reactor, and 2.14 mol / L of oxidant H2O2 and 15 g / L of catalyst La were added. 0.9 The reaction was carried out using CuO3 / SiO2 at a temperature of 100℃ for 30 minutes.

[0044] La 0.9 The synthesis method of CuO3 / SiO2: First, add 3.36g of citric acid and 2.92g of EDTA to 80mL of deionized water, then add ammonia until the solution becomes clear; then add 2.05g of lanthanum nitrate hexahydrate and 1.27g of copper nitrate trihydrate to the solution, stir to dissolve, and then add ammonia to adjust the pH to 8.5.

[0045] Finally, 1.5 g of silica was added to the solution. The beaker containing this mixture was then transferred to an oil bath and stirred at 80°C until a gel state was reached. It was then transferred to an evaporating dish and dried in a forced-air drying oven for 24 hours. After drying, it was transferred to a muffle furnace and calcined at 700°C for 7 hours. Finally, the catalyst La was obtained by grinding. 0.9 CuO3 / SiO2.

[0046] The test results showed that, using the method described in Example 1, the raw water (COD of 4100 mg / L, suspended solids (SS) of 110 mg / L, turbidity of 223 NTU, pH of 8.30) after being treated in a flocculation sedimentation tank and a targeted Fenton reactor, had an effluent COD of 405 mg / L (removal rate of 90.12%), 0 suspended solids (SS), 0 turbidity, and a pH of 7.23. The effluent was clear and colorless.

[0047] Example 3

[0048] This embodiment uses an ABO3 type catalyst with Sr doped at the A site.

[0049] Wastewater is introduced into a flocculation sedimentation tank. 300 ppm of polyaluminum chloride aqueous solution is added through the first inlet tank, and 4 ppm of polyacrylamide aqueous solution is added through the second inlet tank. After the reaction, most of the suspended solids are removed.

[0050] The supernatant after flocculation sedimentation was introduced into a targeted Fenton reactor, and 2.14 mol / L of oxidant H2O2 and 10 g / L of catalyst LaSrCuO3 were added to carry out the reaction at 140℃ for 30 min.

[0051] Synthesis method of LaSrCuO3: First, 3.36 g of citric acid and 2.92 g of EDTA were added sequentially to 80 mL of deionized water, followed by the addition of ammonia until the solution became clear. Next, 1.08 g of lanthanum nitrate hexahydrate, 0.53 g of strontium nitrate, and 1.21 g of copper nitrate trihydrate were added sequentially to the solution, stirred until dissolved, and then ammonia was added to adjust the pH to 8.5. The beaker containing this mixed solution was then transferred to an oil bath and stirred at a constant temperature of 80 °C until a gel state was reached. The solution was then transferred to an evaporating dish and dried in a forced-air drying oven for 24 h. After drying, the solution was transferred to a muffle furnace and calcined at 700 °C for 7 h. Finally, the catalyst LaSrCuO3 was obtained by grinding.

[0052] The test results showed that, using the method described in Example 2, the raw water (COD of 4100 mg / L, suspended solids (SS) of 110 mg / L, turbidity of 223 NTU, pH of 8.30) after being treated in a flocculation sedimentation tank and a targeted Fenton reactor, had an effluent COD of 430 mg / L (removal rate of 89.51%), 0 SS, 0 turbidity, and a pH of 7.56. The effluent was clear and colorless.

[0053] Example 4

[0054] This embodiment uses an ABO3-type catalyst with Mo doped at the B site.

[0055] Wastewater is introduced into a flocculation sedimentation tank. 400 ppm of polyaluminum chloride aqueous solution is added through the first inlet tank, and 2 ppm of polyacrylamide aqueous solution is added through the second inlet tank. After the reaction, most of the suspended solids are removed.

[0056] The supernatant after flocculation sedimentation was introduced into a targeted Fenton reactor, and 1.55 mol / L of oxidant H2O2 and 10 g / L of catalyst LaCuMoO3 were added to carry out the reaction at 140℃ for 60 min.

[0057] Synthesis method of LaCuMoO3: First, 3.36 g of citric acid and 2.92 g of EDTA were added sequentially to 80 mL of deionized water, followed by the addition of ammonia until the solution became clear. Next, 2.17 g of lanthanum nitrate hexahydrate, 0.61 g of copper nitrate trihydrate, and 3.09 g of ammonium molybdate tetrahydrate were added sequentially to the solution, stirred until dissolved, and then ammonia was added to adjust the pH to 8.5. The beaker containing this mixed solution was then transferred to an oil bath and stirred at a constant temperature of 80 °C until a gel state was reached. The solution was then transferred to an evaporating dish and dried in a forced-air drying oven for 24 h. After drying, the solution was transferred to a muffle furnace and calcined at 700 °C for 7 h. Finally, the catalyst LaCuMoO3 was obtained by grinding.

[0058] The test results showed that, using the method described in Example 3, the raw water (COD of 4100 mg / L, suspended solids (SS) of 110 mg / L, turbidity of 223 NTU, pH of 8.30) after being treated in a flocculation sedimentation tank and a targeted Fenton reactor, had an effluent COD of 475 mg / L (removal rate of 88.41%), 0 SS, 0 turbidity, and a pH of 7.75. The effluent was clear and colorless.

[0059] GC-MS analysis showed that the toxicity of the products from targeted Fenton degradation technology was significantly lower than that of the raw water and water from wet oxidation (WAO) technology, and the product structure was also relatively simpler. ECOSAR software prediction analysis indicated that the biotoxicity of the effluent from targeted Fenton degradation technology was significantly lower than that of the raw water and water from wet oxidation (WAO) technology.

[0060] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A targeted Fenton degradation method for petroleum refining wastewater with high organic content and difficult degradation, characterized in that, The method described above treats petroleum refining wastewater containing aromatic and heterocyclic organic compounds. Using the method described above, raw water with a COD of 4100 mg / L, suspended solids (SS) of 110 mg / L, turbidity of 223 NTU, and pH of 8.30 was treated sequentially in a flocculation sedimentation tank and a targeted Fenton reactor. The resulting effluent had a COD of 405 mg / L, a removal rate of 90.12%, SS of 0, turbidity of 0, pH of 7.23, and was clear, colorless, and transparent. The method includes the following steps: Wastewater is introduced into a flocculation sedimentation tank. 300 ppm of polyaluminum chloride aqueous solution is added through the first inlet tank, and 4 ppm of polyacrylamide aqueous solution is added through the second inlet tank. After the reaction, most of the suspended solids are removed. The supernatant after flocculation and sedimentation was introduced into a targeted Fenton reactor, and 2.14 mol / L of oxidant H2O2 and 15 g / L of catalyst La were added. 0.9 The reaction was carried out using CuO3 / SiO2 at a temperature of 100℃ for 30 minutes. La 0.9 The synthesis method of CuO3 / SiO2: First, 3.36 g of citric acid and 2.92 g of EDTA were added sequentially to 80 mL of deionized water, followed by the addition of ammonia until the solution became clear. Then, 2.05 g of lanthanum nitrate hexahydrate and 1.27 g of copper nitrate trihydrate were added sequentially to the solution, stirred until dissolved, and then ammonia was added to adjust the pH to 8.

5. Finally, 1.5 g of silica was added to the solution, and the beaker containing the mixed solution was transferred to an oil bath and stirred at a constant temperature of 80 °C until a gel state was reached. The solution was then transferred to an evaporating dish and dried in a forced-air drying oven for 24 h. After drying, the solution was transferred to a muffle furnace and calcined at 700 °C for 7 h. Finally, the catalyst La was obtained by grinding. 0.9 CuO3 / SiO2.

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