Oily scum comprehensive treatment process and system based on ultrasonic scum dehydration

Abstract

The invention discloses an oil-containing scum comprehensive treatment process based on ultrasonic scum dehydration. The oil-containing scum comprehensive treatment process comprises the following steps: 1) alkalizing oil-containing scum; 2) ultrasonic demulsification: adding a demulsifier into the alkalized oil-containing scum, stirring, and then applying ultrasonic waves for treatment; 3) dehydration of oil-containing scum: standing after ultrasonic demulsification, settling and layering, separating a lower-layer water phase as scum wastewater, and separating an upper-layer oil phase as dehydrated oil-containing scum; according to the technology, resourceful treatment of the oil-containing scum can be achieved, environmental pollution can be reduced, useful resources can be recycled, and obvious economic benefits and environmental protection benefits are formed.

Description

Technical Field

[0001] The invention relates to the technical field of oily scum and wastewater treatment, and in particular to a comprehensive treatment process for oily scum based on ultrasonic scum dehydration. Background Art

[0002] Refinery oily scum refers to the oily sludge produced when oil droplets and solid particles in the water are attached to tiny air bubbles and carried to the water surface after flocculants are added in the flotation section of the wastewater treatment process of petrochemical enterprises (aluminum-based inorganic coagulants are commonly used at this stage). It is mainly composed of negatively charged hydrophilic colloidal particles, with complex composition and difficult to dehydrate. As the quality of crude oil deteriorates, the amount of scum will increase significantly (Han Pingfang, Zhou Yinfei, Lv Xiaoping. Research on flocculation and dehydration of oily scum in refineries [J]. Environmental Science and Technology, 2006, 29 (11): 91-95.). At present, enterprises generally mix scum with other oil sludge and add flocculants. After mechanical separation and dehydration, the water content is reduced to about 85% and then landfilled as hazardous waste. Due to the serious emulsification of scum, the dehydration effect of existing processes is limited, and crude oil recovery is difficult, which not only increases the burden of hazardous waste treatment for enterprises, but also wastes crude oil resources.

[0003] There are three main methods for demulsification of scum, namely physical method, chemical method and biological method. Among them, the physical method mainly includes gravity sedimentation method, centrifugal separation method, filtration method, electric field method, microwave radiation method, ultrasonic method and membrane demulsification method, etc.; the chemical method mainly includes demulsifier addition method.

[0004] The ultrasonic method is to radiate ultrasonic energy into the crude oil emulsion to produce a series of ultrasonic effects, such as stirring, collision, aggregation, cavitation, heating, negative pressure, etc., so as to destroy the oil-water interface film. It can still play the role of demulsification, desalination and dehydration without or with a small amount of demulsifier. Since ultrasound has good conductivity in both oil and water, this method is suitable for various types of emulsions. For water-in-oil emulsified crude oil produced by tertiary oil recovery, wastewater recovery oil, aged oil, etc., due to the complexity of their chemical composition and emulsion structure, it is difficult to use conventional methods to demulsify, desalinate and dehydrate. The sonochemical method can be used for the desalination and dehydration of such oils, and has good results (Li Shuqin, Cheng Yongqing, Zhang Xumin. Study on the sonochemical method for demulsification and dehydration of water-containing crude oil [J]. Tianjin Chemical Industry, 1997, 4: 22-24.).

[0005] Adding demulsifier is a chemical dehydration method, which mainly utilizes the displacement effect of demulsifier. After the demulsifier is added, it diffuses toward the oil-water interface. Since the interfacial activity of the demulsifier is higher than that of the film-forming substances in the crude oil, it can adsorb or partially replace the natural emulsifier adsorbed on the oil-water interface, and form a mixed film with the film-forming substances in the crude oil with a lower interfacial film strength than the original interfacial film, resulting in the destruction of the interfacial film, releasing the water encapsulated in the film, and the water droplets gather together to form large water droplets that settle to the bottom, and the oil and water phases separate, achieving the purpose of demulsification (Kotsaridou. Demulsifyingwater-in-oil emulsions through chemical addition [J]. Erdoel Erdgas Kohle, 1996, 112(2): 72-79.).

[0006] The electro-Fenton reaction is an advanced oxidation technology that combines electrochemistry and the Fenton reaction. It is mainly used to degrade organic pollutants in water. The core of the electro-Fenton reaction is to use the electrolysis process to produce hydrogen peroxide (H2O2) and ferrous ions (Fe²⁺). Then, under acidic conditions, these substances interact to generate hydroxyl radicals (·OH) with strong oxidizing properties. Hydroxyl radicals can quickly attack organic molecules and decompose them into small molecules, thereby achieving the purpose of degrading pollutants.

[0007] At present, the treatment process of oily slag generally has problems such as poor demulsification effect in the early stage and reduced COD removal efficiency in the later stage, which makes it difficult to meet application requirements.

[0008] Therefore, it is necessary to improve the existing technology to provide a reliable solution. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a comprehensive treatment process for oil-containing scum based on ultrasonic scum dehydration in view of the deficiencies in the above-mentioned prior art.

[0010] In order to solve the above technical problems, the technical solution adopted by the present invention is: the present invention provides a comprehensive treatment process for oil-containing scum based on ultrasonic scum dehydration, comprising the following steps: 1) Alkalization of oily scum: add alkali to the oily scum containing aluminum salt flocculant to adjust the pH; 2) Ultrasonic demulsification: add demulsifier to the oily scum after alkalization treatment, stir, and then apply ultrasonic waves for treatment; 3) Dehydration of oily scum: After ultrasonic demulsification, let it stand for sedimentation and stratification, separate the lower water phase as scum wastewater, and separate the upper oil phase as dehydrated oily scum; 4) Post-treatment of scum wastewater: Combine ultrasound and electro-Fenton method to oxidatively degrade COD in scum wastewater; 5) Post-treatment of oily scum after dehydration: distill the oily scum after dehydration to separate the oil phase, water phase and final residue; 6) Aluminum salt recovery: The final residue is acidified to obtain a regenerated aluminum salt solution.

[0011] Preferably, step 1) specifically comprises: adding Na2CO3 to the oily scum containing the aluminum salt flocculant and stirring evenly, adjusting the pH value of the oily scum to 7-9, and obtaining the oily scum after alkalization treatment.

[0012] Preferably, step 2) is specifically: The oily scum after alkalization treatment is injected into a container, a demulsifier with a mass concentration of 0.1-2% is added, and the mixture is stirred at 300-1500 rpm for 15-45 minutes, and then heated to 55-75°C, and ultrasonic standing waves are applied with a frequency of 10-50 kHz and an ultrasonic power of 100-400 W, and the ultrasonic treatment time is 2-15 minutes; Preferably, step 4) is specifically: The scum wastewater was introduced into the electrolytic cell, and Na2SO4 with a concentration of 0.01-0.05 mol / L was added, and then H2O2 solution was added in batches, and the final amount of H2O2 added was controlled to be 0.5-2.1 mmol / L. The electro-Fenton reaction was carried out at 28-32°C and a stirring speed of 40-160r / min. The electro-Fenton reaction time was 50-90min, and the current density was controlled to be 5-20mA / cm 2 , after the electro-Fenton reaction has been carried out for a set time, ultrasonic standing waves are applied simultaneously until the electro-Fenton reaction is completed, and the demulsifier is recovered by magnetic absorption; Among them, the frequency of ultrasound is 25-60kHz and the ultrasonic power is 200-400W.

[0013] Preferably, step 5) is specifically: The dehydrated oil-containing scum is distilled into a stirred reactor and distilled under reduced pressure under heating and stirring to separate the water phase and the oil phase. The product at the bottom of the reactor is the final residue.

[0014] Preferably, step 6) is specifically: 5-20 mg / L hydrochloric acid is added to the final residue after distillation for acidification treatment, and the final residue is neutralized until the alkalinity B value reaches the set value to obtain a regenerated aluminum salt solution.

[0015] Preferably, the comprehensive treatment process for oily scum based on ultrasonic scum dehydration comprises the following steps: 1) Alkalization of oily scum: Adding a 20% Na2CO3 aqueous solution to the oily scum containing the aluminum salt flocculant, stirring evenly, adjusting the pH value of the oily scum to 7.25, and obtaining an alkalized oily scum; 2) Ultrasonic demulsification: The oily scum after alkalization treatment was injected into a container, and a demulsifier with a mass concentration of 0.6% was added, stirred at 1000 rpm for 10 min, and then heated to 60°C, and ultrasonic standing waves were applied with a frequency of 20 kHz and an ultrasonic power of 300 W. The ultrasonic treatment time was 6 min. 3) Dehydration of oily scum: After ultrasonic demulsification, the mixture is allowed to stand for sedimentation and stratification, and the lower water phase is separated as scum wastewater, and the upper oil phase is separated as oily scum after dehydration; 4) Post-treatment of scum wastewater: The scum wastewater was introduced into the electrolytic cell, and Na2SO4 with a concentration of 0.02 mol / L was added. Then H2O2 solution was added in batches, and the final amount of H2O2 added was controlled to be 1.05 mmol / L. The electro-Fenton reaction was carried out at 30°C and a stirring speed of 80 r / min. The electro-Fenton reaction time was 75 min, and the current density was controlled to be 10.2 mA / cm 2 After the electro-Fenton reaction has been carried out for 60 minutes, an ultrasonic standing wave is applied until the electro-Fenton reaction is completed, and the demulsifier is recovered by magnetic absorption; Among them, the frequency of the ultrasonic wave is 45kHz and the ultrasonic power is 350W; 5) Post-treatment of oily scum after dehydration: The dehydrated oily scum is distilled and added into a stirred reactor, and stirred at a speed of 150 rpm while heating, and distilled under reduced pressure to separate the water phase and the oil phase. The product at the bottom of the reactor is the final residue; 6) Aluminum salt recovery: Add 10 mg / L hydrochloric acid to the final residue after distillation for acidification, neutralize the final residue to an alkalinity B value of 1.2, and obtain a regenerated aluminum salt solution.

[0016] Preferably, the demulsifier is prepared by the following method: 2-1) Preparation of nickel-doped porous ferroferric oxide: 0.5-2g FeCl3·6H2O, 0.15-0.7g NiCl2·6H2O, 25-100mL ethanol, 20-90mL cyclohexane are added to 100-300mL ethylene glycol, ultrasonically dispersed for 15-60min, then 1.6-6.4g urotropine is added, stirred for 5-30min, the resulting mixed solution is transferred to a polytetrafluoroethylene-lined reactor, reacted at 150-175°C for 4-8h, cooled to room temperature after the reaction, filtered, the solid product is washed with ethanol and deionized water in turn, dried at 60-90°C for 3-10h, then calcined at 450-600°C in a nitrogen atmosphere for 2-6h, cooled to room temperature, and nickel-doped porous ferrosoferric oxide is obtained, which is recorded as Ni-Fe3O4; 2-2) Loading ruthenium-doped carbon dots on nickel-doped porous ferroferric oxide: 2-2-1) Add 291-1164 mg of aminoacridine yellow, 384-1536 mg of citric acid, 120-480 mg of acetic acid, 45-180 mg of ethylenediamine, and 52-208 mg of RuCl3·3H2O to a mixed solution consisting of 50-200 mL of ethanol and 25-100 mL of deionized water, and disperse by ultrasonication for 3-20 min to obtain a precursor solution 1; 2-2-2) Take 0.6-2.4g of nickel-doped porous ferroferric oxide and add it to 50-200mL of deionized water, and ultrasonically disperse it for 10-30min to obtain precursor solution 2; 2-2-3) Precursor solution 1 is added to precursor solution 2 under stirring, and stirred at 500-2500 rpm for 15-60 min. The resulting mixture is transferred to a polytetrafluoroethylene-lined reactor and reacted at 170-210° C. for 6-24 h. After the reaction is completed, it is cooled to room temperature and filtered. The solid product is washed with deionized water and vacuum dried at 70-110° C. for 6-24 h to obtain the demulsifier, which is recorded as Ni-Fe3O4@Ru-CDs.

[0017] Preferably, the demulsifier is prepared by the following method: 2-1) Preparation of nickel-doped porous ferroferric oxide: 1 g FeCl3·6H2O, 0.35 g NiCl2·6H2O, 50 mL ethanol, and 45 mL cyclohexane were added to 150 mL ethylene glycol, and ultrasonically dispersed for 30 min. Then, 3.2 g urotropine was added and stirred for 10 min. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 165 ° C for 6 h. After the reaction was completed, it was cooled to room temperature and filtered. The solid product was washed with ethanol and deionized water in turn, dried at 70 ° C for 6 h, and then calcined at 550 ° C in a nitrogen atmosphere for 4 h. It was cooled to room temperature to obtain nickel-doped porous ferrosoferric oxide, which was recorded as Ni-Fe3O4. 2-2) Loading ruthenium-doped carbon dots on nickel-doped porous ferroferric oxide: 2-2-1) 582 mg of aminoacridine yellow, 768 mg of citric acid, 240 mg of acetic acid, 90 mg of ethylenediamine, and 104 mg of RuCl3·3H2O were added to a mixed solution consisting of 100 mL of ethanol and 50 mL of deionized water, and ultrasonically dispersed for 5 minutes to obtain a precursor solution 1; 2-2-2) Take 1.2g of nickel-doped porous ferroferric oxide and add it to 100mL of deionized water, and disperse it by ultrasonic for 15min to obtain precursor solution 2; 2-2-3) Precursor solution 1 was added to precursor solution 2 under stirring, and the mixture was stirred at 1000 rpm for 30 min. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 180° C. for 12 h. After the reaction was completed, the mixture was cooled to room temperature and filtered. The solid product was washed with deionized water and vacuum dried at 90° C. for 12 to obtain the demulsifier, which was recorded as Ni-Fe3O4@Ru-CDs.

[0018] The present invention also provides an oil-containing scum comprehensive treatment system based on ultrasonic scum dehydration, which uses the process as described above to treat the oil-containing scum.

[0019] The beneficial effects of the present invention are: In the comprehensive treatment process of oil-containing scum provided by the present invention, the scum is firstly alkalized, and then demulsified by a demulsifier combined with ultrasound, and the oil-water stratification is achieved by gravity sedimentation, the lower layer is the scum wastewater containing the demulsifier, and the upper oil phase is the preliminary dehydrated oil-containing scum; the scum wastewater containing the demulsifier is further subjected to a process combined with the electro-Fenton method and ultrasound, and the organic components in the water are efficiently degraded by strong oxidation to remove COD; the preliminary dehydrated oil-containing scum is separated by distillation to achieve the separation of the water phase, the oil phase, and the final residue, the oil phase is recovered as a by-product, the water phase recovery can be further processed, and the final residue is acidified by hydrochloric acid to achieve the recovery of regenerated aluminum salt. The process of the present invention can realize the resource treatment of oil-containing scum, which can not only reduce environmental pollution, but also recover useful resources, forming obvious economic and environmental benefits.

[0020] The demulsifier of the present invention is obtained by in-situ loading of ruthenium-doped carbon dots on nickel-doped porous ferroferric oxide. With the help of the sonic sensitivity of the ruthenium-doped carbon dots, it can efficiently generate active oxygen under the action of ultrasound, showing excellent oxidation ability, and can achieve efficient demulsification in the early dehydration operation stage, and further in the later scum wastewater treatment stage, it can achieve efficient removal of COD; at the same time, since the demulsifier has a porous structure, it can also provide physical adsorption at the same time.

[0021] In the scum wastewater treatment stage of the present invention, COD removal can be achieved through the strong oxidizing effect of ·OH produced by the electro-Fenton reaction. After combining it with ultrasound, on the one hand, the mass transfer rate of the homogeneous and heterogeneous systems can be enhanced, so that the ·OH in the reaction system can react with the organic pollutant molecules in the wastewater in time; on the other hand, under the action of ultrasound, the demulsifier in the scum wastewater can also efficiently produce active oxygen, thereby further enhancing the COD removal effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The test results of the moisture content of the initial dehydrated oily scum in the processes of Examples 1-3 and Comparative Examples 1-4; Figure 2 The test results of COD removal rate in the processes of Examples 1-3 and Comparative Examples 1-4 are as follows; Figure 3 The test results of oil recovery rate in the processes of Examples 1-3 and Comparative Examples 1-4 are as follows; Figure 4 The test results of the aluminum salt recovery rate in the processes of Examples 1-3 and Comparative Examples 1-4 are as follows; Figure 5 The test results of the effect of ultrasonic action time on the water content in the initial dehydrated oily scum; Figure 6 The test results of the effect of ultrasonic power on the water content in the initial dehydrated oily scum; Figure 7 The test results of the influence of ultrasonic demulsification temperature on the water content in the initial dehydrated oily scum; Figure 8 is the XRD pattern of the demulsifier prepared in Example 1; Fig. 9 These are the test results of the active oxygen generation performance test of the demulsifiers prepared in Example 1, Comparative Example 2, and Comparative Example 3. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with embodiments so that those skilled in the art can implement the invention with reference to the description.

[0024] It should be understood that the terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0025] The test methods used in the following examples are conventional methods unless otherwise specified. The materials and reagents used in the following examples are all commercially available unless otherwise specified. In the following examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturer is not specified, are all conventional products that can be purchased commercially.

[0026] The first aspect of the present invention provides a comprehensive treatment process for oil-containing scum based on ultrasonic scum dehydration, comprising the following steps: 1) Alkalization of oily scum: Na2CO3 is added to the oily scum containing the aluminum salt flocculant and stirred evenly, and the pH value of the oily scum is adjusted to 7-9 to obtain the oily scum after alkalization treatment.

[0027] 2) Ultrasonic demulsification: The oily scum after alkalization treatment is injected into a container, a demulsifier with a mass concentration of 0.1-2% is added, stirred at 300-1500rpm for 15-45min, then heated to 55-75℃, ultrasonic standing wave is applied, the frequency is 10-50kHz, the ultrasonic power is 100-400W, and the ultrasonic treatment time is 2-15min.

[0028] 3) Dehydration of oily scum: After ultrasonic demulsification, the mixture is allowed to stand for sedimentation and stratification, and the lower water phase is separated as scum wastewater, and the upper oil phase is separated as oily scum after dehydration; 4) Post-treatment of scum wastewater: The scum wastewater was introduced into the electrolytic cell, and Na2SO4 with a concentration of 0.01-0.05 mol / L was added, and then H2O2 solution was added in batches, and the final amount of H2O2 added was controlled to be 0.5-2.1 mmol / L. The electro-Fenton reaction was carried out at 28-32°C and a stirring speed of 40-160r / min. The electro-Fenton reaction time was 50-90min, and the current density was controlled to be 5-20mA / cm 2 After the electro-Fenton reaction has been going on for a set time, ultrasonic standing waves are applied simultaneously until the electro-Fenton reaction is finished, and the demulsifier is recovered by magnetic absorption; the remaining water can be further filtered and then subjected to subsequent biochemical treatment; Among them, the frequency of ultrasound is 25-60kHz and the ultrasonic power is 200-400W.

[0029] 5) Post-treatment of oily scum after dehydration: The dehydrated oil-containing scum is distilled into a stirred reactor and distilled under reduced pressure under heating and stirring to separate the water phase and the oil phase. The product at the bottom of the reactor is the final residue.

[0030] 6) Aluminum salt recovery: 5-20 mg / L hydrochloric acid is added to the final residue after distillation for acidification treatment, and the final residue is neutralized until the alkalinity B value reaches the set value to obtain a regenerated aluminum salt solution.

[0031] In a preferred embodiment, the demulsifier is prepared by the following method: 2-1) Preparation of nickel-doped porous ferroferric oxide: 0.5-2g FeCl3·6H2O, 0.15-0.7g NiCl2·6H2O, 25-100mL ethanol, 20-90mL cyclohexane are added to 100-300mL ethylene glycol, ultrasonically dispersed for 15-60min, then 1.6-6.4g urotropine is added, stirred for 5-30min, the resulting mixed solution is transferred to a polytetrafluoroethylene-lined reactor, reacted at 150-175°C for 4-8h, cooled to room temperature after the reaction, filtered, the solid product is washed with ethanol and deionized water in turn, dried at 60-90°C for 3-10h, then calcined at 450-600°C in a nitrogen atmosphere for 2-6h, cooled to room temperature, and nickel-doped porous ferrosoferric oxide is obtained, which is recorded as Ni-Fe3O4; 2-2) Loading ruthenium-doped carbon dots on nickel-doped porous ferroferric oxide: 2-2-1) Add 291-1164 mg of aminoacridine yellow, 384-1536 mg of citric acid, 120-480 mg of acetic acid, 45-180 mg of ethylenediamine, and 52-208 mg of RuCl3·3H2O to a mixed solution consisting of 50-200 mL of ethanol and 25-100 mL of deionized water, and disperse by ultrasonication for 3-20 min to obtain a precursor solution 1; 2-2-2) Take 0.6-2.4g of nickel-doped porous ferroferric oxide and add it to 50-200mL of deionized water, and ultrasonically disperse it for 10-30min to obtain precursor solution 2; 2-2-3) Precursor solution 1 is added to precursor solution 2 under stirring, and the mixture is stirred at 500-2500 rpm for 15-60 min. The resulting mixture is transferred to a polytetrafluoroethylene-lined reactor and reacted at 170-210° C. for 6-24 h. After the reaction is completed, the mixture is cooled to room temperature and filtered. The solid product is washed with deionized water and vacuum dried at 70-110° C. for 6-24 h to obtain a demulsifier, which is recorded as Ni-Fe3O4@Ru-CDs.

[0032] The second aspect of the present invention provides a comprehensive treatment system for oil-containing scum based on ultrasonic scum dehydration, which uses the above process to treat the oil-containing scum.

[0033] In the comprehensive treatment process of oil-containing scum provided by the present invention, the scum is firstly subjected to alkalization treatment, and then demulsification is carried out by combining a demulsifier with ultrasound, and oil-water separation is achieved by gravity sedimentation, the lower layer is scum wastewater containing the demulsifier, and the upper oil phase is the preliminary dehydrated oil-containing scum; The scum wastewater containing demulsifier is further subjected to a process combining electro-Fenton method and ultrasound to achieve efficient degradation of organic components in the water and remove COD through strong oxidation; The initial dehydrated oily scum is separated into a water phase, an oil phase and a final residue by distillation, the oil phase is recovered as a byproduct, the recovered water phase can be further processed, and the final residue is acidified by hydrochloric acid to recover the regenerated aluminum salt. The process of the invention can realize the resource treatment of the oily scum, which can not only reduce environmental pollution, but also recover useful resources, forming obvious economic and environmental benefits.

[0034] The demulsifier of the present invention is obtained by in-situ loading of ruthenium-doped carbon dots on nickel-doped porous ferroferric oxide. With the help of the sonic sensitivity of ruthenium-doped carbon dots, it can efficiently generate active oxygen under ultrasound, showing excellent oxidation ability, and can achieve efficient demulsification in the early dehydration operation stage, and further in the later scum wastewater treatment stage. Efficient removal of COD; at the same time, since the demulsifier has a porous structure, it can also provide physical adsorption at the same time. The preparation method and mechanism of action are described in detail below to facilitate the understanding of the present invention.

[0035] The present invention firstly combines conventional hydrothermal reaction with calcination to prepare nickel-doped porous ferroferric oxide with a rich pore structure; the nickel-doped porous ferroferric oxide has certain oxidizability and good magnetism, and nickel doping can improve its high temperature resistance and magnetism, improve the stability of the pore structure, and reduce the collapse of pores during the calcination process, thereby facilitating the increase of specific surface area and enhancing adsorption performance.

[0036] Then, using aminoacridine yellow, citric acid, acetic acid, and ethylenediamine as the main raw materials and RuCl3·3H2O as the doping component, a demulsifier was obtained by in situ grafting ruthenium-doped carbon dots onto nickel-doped porous ferroferric oxide through a one-pot hydrothermal method.

[0037] In the demulsifier of the present invention, the ruthenium-doped carbon dots have inherited the sonic thermal properties of aminoacridine yellow and can efficiently generate active oxygen under the action of ultrasound; the doped ruthenium will generate ruthenium oxide (RuO2) during the reaction process, which itself has high oxidizing properties. At the same time, since the doping of Ru changes the electronic structure, new surface energy can be formed, the active sites are increased, the sonic sensitive effect of the carbon dots is enhanced, and the generation efficiency of active oxygen is enhanced, thereby significantly improving the oxidizing property of the demulsifier.

[0038] The demulsifier in the present invention is mainly based on the oxidative demulsification mechanism. The working principle of oxidative demulsification is mainly to destroy the emulsifier in the emulsion through oxidation reaction; in the emulsion, the emulsifier reduces the oil-water interfacial tension so that the oil and water can form a stable mixture; and the oxidative demulsifier can undergo redox reaction with the emulsifier, making the emulsifier inactive, thereby reducing the stability of the emulsion. The demulsifier in the present invention exhibits strong oxidizing properties under the assistance of ultrasound, which can oxidize and degrade the dirty oil coated on the water surface, destroy the stable mixture formed by oil and water, and thus promote oil-water separation; and in the demulsification process, the stirring, collision, aggregation, cavitation, heating, negative pressure and other effects generated by ultrasound can also destroy the oil-water interface film and achieve demulsification. Therefore, in the present invention, the ultrasound in the demulsification operation link can achieve demulsification mainly through physical effects on the one hand, and on the other hand, it can assist ruthenium-doped carbon points to achieve chemical demulsification through strong oxidation. The combination of the two aspects can significantly improve the demulsification effect.

[0039] Furthermore, the strong oxidizing property of the demulsifier can cooperate with the electro-Fenton reaction in the subsequent scum wastewater treatment stage to achieve efficient COD degradation. Therefore, in addition to playing a role in oxidative degradation of oil film in the demulsification operation section, the demulsifier can also play a role in oxidative degradation of COD in the subsequent scum wastewater treatment process.

[0040] The degradation of pollutants by the electro-Fenton reaction mainly relies on the strong oxidizing effect of ·OH. When combined with ultrasound, the cavitation bubbles generated under the action of ultrasound are accompanied by strong impact and micro-jets when they break and collapse, causing local violent turbulence, thereby enhancing the mass transfer rate of the homogeneous and heterogeneous systems, so that the ·OH in the reaction system can react with the organic pollutant molecules in the wastewater in time, improving the reaction effect; in the final collapse stage of the cavitation bubbles, local high temperature and high pressure will occur, forming a local hot spot effect, accompanied by strong shock waves, high-speed micro-jets, and the generation of free radicals, which can decompose the organic pollutants in the wastewater into small molecules. The above factors have increased the COD removal rate in a relatively short time. Furthermore, under the action of ultrasound, the demulsifier in the scum wastewater can also efficiently produce active oxygen, thereby further enhancing the COD removal effect.

[0041] The above is the overall concept of the present invention, and detailed embodiments and comparative examples are provided below on the basis of the overall concept of the present invention to further illustrate the present invention.

[0042] Example 1 A comprehensive treatment process for oily scum based on ultrasonic scum dehydration, comprising the following steps: 1) Alkalization of oily scum: Adding a 20% Na2CO3 aqueous solution to the oily scum containing the aluminum salt flocculant, stirring evenly, adjusting the pH value of the oily scum to 7.25, and obtaining an alkalized oily scum; 2) Ultrasonic demulsification: The oily scum after alkalization treatment was injected into a container, and a demulsifier with a mass concentration of 0.6% was added, stirred at 1000 rpm for 10 min, and then heated to 60°C, and ultrasonic standing waves were applied with a frequency of 20 kHz and an ultrasonic power of 300 W. The ultrasonic treatment time was 6 min. 3) Dehydration of oily scum: After ultrasonic demulsification, the mixture is allowed to stand for sedimentation and stratification, and the lower water phase is separated as scum wastewater, and the upper oil phase is separated as oily scum after dehydration; 4) Post-treatment of scum wastewater: The scum wastewater was introduced into the electrolytic cell, and Na2SO4 with a concentration of 0.02 mol / L was added. Then H2O2 solution was added in batches, and the final amount of H2O2 added was controlled to be 1.05 mmol / L. The electro-Fenton reaction was carried out at 30°C and a stirring speed of 80 r / min. The electro-Fenton reaction time was 75 min, and the current density was controlled to be 10.2 mA / cm 2 After the electro-Fenton reaction has been going on for 60 minutes, an ultrasonic standing wave (duration 15 minutes) is applied simultaneously until the electro-Fenton reaction is finished, and the demulsifier is recovered by magnetic absorption; Among them, the frequency of the ultrasonic wave is 45kHz and the ultrasonic power is 350W; 5) Post-treatment of oily scum after dehydration: The dehydrated oily scum is distilled and added into a stirred reactor, and stirred at a speed of 150 rpm while heating, and distilled under reduced pressure to separate the water phase and the oil phase. The product at the bottom of the reactor is the final residue; 6) Aluminum salt recovery: 10 mg / L hydrochloric acid was added to the final residue after distillation for acidification, and the final residue was neutralized to an alkalinity B value (i.e., basicity B value) of 1.2 to obtain a regenerated aluminum salt solution.

[0043] The demulsifier was prepared by the following method: 2-1) Preparation of nickel-doped porous ferroferric oxide: Take 1g FeCl3·6H2O, 0.35g NiCl2·6H2O, 50mL ethanol, and 45mL cyclohexane and add them to 150mL ethylene glycol, ultrasonically disperse for 30min, then add 3.2g urotropine (hexamethylenetetramine), stir for 10min, transfer the resulting mixture to a polytetrafluoroethylene-lined reactor, react at 165°C for 6h, cool to room temperature after the reaction, filter, wash the solid product with ethanol and deionized water in turn, dry at 70°C for 6h, then calcine at 550°C in a nitrogen atmosphere for 4h, and cool to room temperature to obtain nickel-doped porous ferrosoferric oxide, recorded as Ni-Fe3O4; 2-2) Loading ruthenium-doped carbon dots on nickel-doped porous ferroferric oxide: 2-2-1) 582 mg of aminoacridine yellow, 768 mg of citric acid, 240 mg of acetic acid, 90 mg of ethylenediamine, and 104 mg of RuCl3·3H2O were added to a mixed solution consisting of 100 mL of ethanol and 50 mL of deionized water, and ultrasonically dispersed for 5 minutes to obtain a precursor solution 1; 2-2-2) Take 1.2g of nickel-doped porous ferroferric oxide and add it to 100mL of deionized water, and disperse it by ultrasonic for 15min to obtain precursor solution 2; 2-2-3) Precursor solution 1 was added to precursor solution 2 under stirring, and the mixture was stirred at 1000 rpm for 30 min. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 180°C for 12 h. After the reaction was completed, the mixture was cooled to room temperature and filtered. The solid product was washed with deionized water and vacuum dried at 90°C for 12 to obtain a demulsifier, which was recorded as Ni-Fe3O4@Ru-CDs.

[0044] Example 2 A comprehensive treatment process for oily scum based on ultrasonic scum dehydration, comprising the following steps: 1) Alkalization of oily scum: Adding a 20% Na2CO3 aqueous solution to the oily scum containing the aluminum salt flocculant, stirring evenly, adjusting the pH value of the oily scum to 7.25, and obtaining an alkalized oily scum; 2) Ultrasonic demulsification: The oily scum after alkalization treatment was injected into a container, and a demulsifier with a mass concentration of 0.5% was added, stirred at 1000 rpm for 10 min, and then heated to 60°C, and ultrasonic standing waves were applied with a frequency of 20 kHz and an ultrasonic power of 300 W. The ultrasonic treatment time was 6 min. 3) Dehydration of oily scum: After ultrasonic demulsification, the mixture is allowed to stand for sedimentation and stratification, and the lower water phase is separated as scum wastewater, and the upper oil phase is separated as oily scum after dehydration; 4) Post-treatment of scum wastewater: The scum wastewater was introduced into the electrolytic cell, and Na2SO4 with a concentration of 0.015 mol / L was added. Then H2O2 solution was added in batches, and the final amount of H2O2 added was controlled to be 1.2 mmol / L. The electro-Fenton reaction was carried out at 30°C and a stirring speed of 80 r / min. The electro-Fenton reaction time was 75 min, and the current density was controlled to be 10.2 mA / cm 2 After the electro-Fenton reaction has been carried out for 60 minutes, an ultrasonic standing wave is applied until the electro-Fenton reaction is completed, and the demulsifier is recovered by magnetic absorption; Among them, the frequency of the ultrasound is 45kHz and the ultrasonic power is 350W.

[0045] 5) Post-treatment of oily scum after dehydration: The dehydrated oily scum is distilled and added into a stirred reactor, and stirred at a speed of 150 rpm while heating, and distilled under reduced pressure to separate the water phase and the oil phase. The product at the bottom of the reactor is the final residue; 6) Aluminum salt recovery: Add 10 mg / L hydrochloric acid to the final residue after distillation for acidification, neutralize the final residue to an alkalinity B value of 1.2, and obtain a regenerated aluminum salt solution.

[0046] The demulsifier was prepared by the following method: 2-1) Preparation of nickel-doped porous ferroferric oxide: 1 g FeCl3·6H2O, 0.35 g NiCl2·6H2O, 50 mL ethanol, and 45 mL cyclohexane were added to 150 mL ethylene glycol, and ultrasonically dispersed for 30 min. Then, 3.2 g urotropine was added and stirred for 10 min. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 165 ° C for 6 h. After the reaction was completed, it was cooled to room temperature and filtered. The solid product was washed with ethanol and deionized water in turn, dried at 70 ° C for 6 h, and then calcined at 550 ° C in a nitrogen atmosphere for 4 h. It was cooled to room temperature to obtain nickel-doped porous ferrosoferric oxide, which was recorded as Ni-Fe3O4. 2-2) Loading ruthenium-doped carbon dots on nickel-doped porous ferroferric oxide: 2-2-1) 582 mg of aminoacridine yellow, 768 mg of citric acid, 240 mg of acetic acid, 90 mg of ethylenediamine, and 104 mg of RuCl3·3H2O were added to a mixed solution consisting of 100 mL of ethanol and 50 mL of deionized water, and ultrasonically dispersed for 5 minutes to obtain a precursor solution 1; 2-2-2) Take 1.5g of nickel-doped porous ferroferric oxide and add it to 100mL of deionized water, and disperse it by ultrasonic for 15min to obtain precursor solution 2; 2-2-3) Precursor solution 1 was added to precursor solution 2 under stirring, and the mixture was stirred at 1000 rpm for 30 min. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 180°C for 12 h. After the reaction was completed, the mixture was cooled to room temperature and filtered. The solid product was washed with deionized water and vacuum dried at 90°C for 12 to obtain a demulsifier, which was recorded as Ni-Fe3O4@Ru-CDs.

[0047] Example 3 A comprehensive treatment process for oily scum based on ultrasonic scum dehydration, comprising the following steps: 1) Alkalization of oily scum: Adding a 20% Na2CO3 aqueous solution to the oily scum containing the aluminum salt flocculant, stirring evenly, adjusting the pH value of the oily scum to 7.25, and obtaining an alkalized oily scum; 2) Ultrasonic demulsification: The oily scum after alkalization treatment was injected into a container, and a demulsifier with a mass concentration of 0.7% was added, stirred at 1000 rpm for 10 min, and then heated to 60°C, and ultrasonic standing waves were applied with a frequency of 20 kHz and an ultrasonic power of 300 W. The ultrasonic treatment time was 6 min. 3) Dehydration of oily scum: After ultrasonic demulsification, the mixture is allowed to stand for sedimentation and stratification, and the lower water phase is separated as scum wastewater, and the upper oil phase is separated as oily scum after dehydration; 4) Post-treatment of scum wastewater: The scum wastewater was introduced into the electrolytic cell, and Na2SO4 with a concentration of 0.02 mol / L was added. Then H2O2 solution was added in batches, and the final amount of H2O2 added was controlled to be 0.8 mmol / L. The electro-Fenton reaction was carried out at 30°C and a stirring speed of 80 r / min. The electro-Fenton reaction time was 75 min, and the current density was controlled to be 8.5 mA / cm 2 After the electro-Fenton reaction has been carried out for 60 minutes, an ultrasonic standing wave is applied until the electro-Fenton reaction is completed, and the demulsifier is recovered by magnetic absorption; Among them, the frequency of the ultrasound is 45kHz and the ultrasonic power is 350W.

[0048] 5) Post-treatment of oily scum after dehydration: The dehydrated oily scum is distilled and added into a stirred reactor, and stirred at a speed of 150 rpm while heating, and distilled under reduced pressure to separate the water phase and the oil phase. The product at the bottom of the reactor is the final residue; 6) Aluminum salt recovery: Add 10 mg / L hydrochloric acid to the final residue after distillation for acidification, neutralize the final residue to an alkalinity B value of 1.2, and obtain a regenerated aluminum salt solution.

[0049] The demulsifier was prepared by the following method: 2-1) Preparation of nickel-doped porous ferroferric oxide: 1 g FeCl3·6H2O, 0.35 g NiCl2·6H2O, 50 mL ethanol, and 45 mL cyclohexane were added to 150 mL ethylene glycol, and ultrasonically dispersed for 30 min. Then, 3.2 g urotropine was added and stirred for 10 min. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 165 ° C for 6 h. After the reaction was completed, it was cooled to room temperature and filtered. The solid product was washed with ethanol and deionized water in turn, dried at 70 ° C for 6 h, and then calcined at 550 ° C in a nitrogen atmosphere for 4 h. It was cooled to room temperature to obtain nickel-doped porous ferrosoferric oxide, which was recorded as Ni-Fe3O4. 2-2) Loading ruthenium-doped carbon dots on nickel-doped porous ferroferric oxide: 2-2-1) 582 mg of aminoacridine yellow, 768 mg of citric acid, 240 mg of acetic acid, 90 mg of ethylenediamine, and 104 mg of RuCl3·3H2O were added to a mixed solution consisting of 100 mL of ethanol and 50 mL of deionized water, and ultrasonically dispersed for 5 minutes to obtain a precursor solution 1; 2-2-2) Take 1.4 g of nickel-doped porous ferroferric oxide and add it to 100 mL of deionized water, and disperse it by ultrasonic for 15 minutes to obtain precursor solution 2; 2-2-3) Precursor solution 1 was added to precursor solution 2 under stirring, and the mixture was stirred at 1000 rpm for 30 min. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 180°C for 12 h. After the reaction was completed, the mixture was cooled to room temperature and filtered. The solid product was washed with deionized water and vacuum dried at 90°C for 12 to obtain a demulsifier, which was recorded as Ni-Fe3O4@Ru-CDs.

[0050] Comparative Example 1 The only difference between this example and Example 1 is that in step 2), no demulsifier is added.

[0051] Comparative Example 2 The only difference between this example and Example 1 is that during the electro-Fenton reaction in step 4), no ultrasonic wave is applied.

[0052] Comparative Example 3 The difference between this example and Example 1 is that: The demulsifier in this example was prepared by the following method: 2-1) Preparation of porous ferroferric oxide: 1 g of FeCl3·6H2O, 50 mL of ethanol, and 45 mL of cyclohexane were added to 150 mL of ethylene glycol, and ultrasonically dispersed for 30 min. Then, 3.2 g of urotropine was added and stirred for 10 min. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 165 ° C for 6 h. After the reaction was completed, it was cooled to room temperature and filtered. The solid product was washed with ethanol and deionized water in turn, dried at 70 ° C for 6 h, and then calcined at 550 ° C in a nitrogen atmosphere for 4 h, and cooled to room temperature to obtain porous ferrosoferric oxide. 2-2) Loading ruthenium-doped carbon dots on porous ferroferric oxide: 2-2-1) 582 mg of aminoacridine yellow, 768 mg of citric acid, 240 mg of acetic acid, 90 mg of ethylenediamine, and 104 mg of RuCl3·3H2O were added to a mixed solution consisting of 100 mL of ethanol and 50 mL of deionized water, and ultrasonically dispersed for 5 minutes to obtain a precursor solution 1; 2-2-2) Take 1.2g of nickel-doped porous ferroferric oxide and add it to 100mL of deionized water, and disperse it by ultrasonic for 15min to obtain precursor solution 2; 2-2-3) Precursor solution 1 was added to precursor solution 2 under stirring, and the mixture was stirred at 1000 rpm for 30 min. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 180°C for 12 h. After the reaction was completed, the mixture was cooled to room temperature and filtered. The solid product was washed with deionized water and vacuum dried at 90°C for 12 to obtain a demulsifier, which was recorded as Fe3O4@Ru-CDs.

[0053] Comparative Example 4 The difference between this example and Example 1 is that: The demulsifier in this example was prepared by the following method: 2-1) preparing nickel-doped porous ferroferric oxide, the specific steps are the same as those in Example 1; 2-2) Loading carbon dots on nickel-doped porous ferroferric oxide: 2-2-1) 582 mg of aminoacridine yellow, 768 mg of citric acid, 240 mg of acetic acid, and 90 mg of ethylenediamine were added to a mixed solution consisting of 100 mL of ethanol and 50 mL of deionized water, and ultrasonically dispersed for 5 minutes to obtain a precursor solution 1; 2-2-2) Take 1.2g of nickel-doped porous ferroferric oxide and add it to 100mL of deionized water, and disperse it by ultrasonic for 15min to obtain precursor solution 2; 2-2-3) Precursor solution 1 was added to precursor solution 2 under stirring, and the mixture was stirred at 1000 rpm for 30 min. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 180°C for 12 h. After the reaction was completed, the mixture was cooled to room temperature and filtered. The solid product was washed with deionized water and vacuum dried at 90°C for 12 to obtain a demulsifier, which was recorded as Ni-Fe3O4@CDs.

[0054] 1. Process treatment effect test The oily scum from the flotation section of Yangzhou Petrochemical Co., Ltd. was used as the test object, and the process of the above embodiment and comparative example was used for treatment. The flocculant added in the flotation section was a mixture of PAM (polyacrylamide) and PAC (polyaluminium chloride), and the amount of PAM added was 2 mg / L and the amount of PAC added was 5 mg / L. The main shape of the oily scum was: the scum water content was 97%, the oil content was 5‰, the scum volume average particle size was 28.3 μm, and the specific surface area was 0.62 m 2 ·g -1 .

[0055] Test items include: 1. The water content ηw of the preliminary dehydrated oily scum obtained in step 3); 2. Detect the COD content of the scum wastewater before treatment and the COD content of the treated wastewater obtained after treatment in step 4), and calculate the COD removal rate; 3. Recovery rate of oil phase product in step 5) γ O ; 4. Recovery rate of aluminum salt in step 6) γ Al ; The determination of water content refers to GB / T 260-2016 "Determination of water content of petroleum products - Distillation method".

[0056] Determination of oil content: The solution in the distillation flask is filtered through pre-weighed filter paper and collected in a 100 mL beaker. The distillation flask and the filter paper are placed in an oven and dried at 105 °C to constant weight. The weight difference before and after is the solid phase weight. The oil content of the scum is obtained by the differential weight method.

[0057] Determination of COD: Determine the COD of wastewater according to “Water Quality-Determination of Chemical Oxygen Demand-Sealed Catalytic Digestion Method” (HZ-HJ-SZ-0108).

[0058] The test results are shown in Table 1 and Figure 1-4 As shown: Table 1 From the test results, it can be seen that From the test results in Table 1, it can be seen that in the processes of Examples 1-3, efficient demulsification can be achieved, the COD removal rate is high, and the recovery rate of oil phase byproducts and aluminum salts is high; in Comparative Example 1, no demulsifier is added, which seriously affects the dehydration rate in its front-end ultrasonic demulsification process and the COD removal rate in the subsequent water treatment process; in Comparative Example 2, ultrasound is not applied in the post-treatment of the scum wastewater, which adversely affects the COD removal effect; the results of Comparative Examples 3 and 4 show that the doping of nickel in the ferroferric oxide of the demulsifier can improve the performance of the demulsifier, and the doping of ruthenium in the carbon dots has a significant enhancement effect on improving COD removal.

[0059] 2. Parameter Optimization Experiment 1. According to Example 1, the ultrasonic action time was changed to test the water content in the preliminary dehydrated oily scum.

[0060] The test results are as follows Figure 5 As shown in the figure, it can be seen that within a certain range (0-6min), as the ultrasonic time increases, the water content gradually decreases, but as the ultrasonic radiation time further increases, the water content of the scum will gradually increase, and the dehydration effect will deteriorate. This is because the scum contains a large amount of solid particles and dirty oil. The mechanical vibration of the ultrasound changes the surface structure of the particles, reduces the adsorption capacity of the particles to oil, and makes it easier to peel off from the particle surface; the oil droplets collide and aggregate with each other to form oil droplets with larger particle size, which are easy to separate from water. As the ultrasonic time increases, the total energy input into the system continues to increase, which in turn breaks up the aggregated oil droplets and re-integrates them into water, promoting the emulsification of the oil droplets, resulting in a deterioration of the dehydration effect (Wang Hongping. Research on droplet motion and coalescence characteristics under ultrasonic action [D]. Beijing: China University of Petroleum (Beijing), 2014.). Too short or too long ultrasonic time is not conducive to the dehydration of scum. The relative optimal ultrasonic time is determined to be 6 min.

[0061] 2. According to Example 1, the ultrasonic power was changed to test the water content in the preliminary dehydrated oily scum to study the effects of ultrasonic action time and ultrasonic power on demulsification and dehydration.

[0062] The test results are as follows Figure 6 As shown in the figure, it can be seen that with the increase of acoustic power, the water content of the scum after treatment first decreases and then increases. There is an optimal value of ultrasonic power in the process of ultrasonic dehydration. This is because with the increase of acoustic power, the corresponding ultrasonic sound intensity is also increasing. When the ultrasonic sound intensity exceeds the cavitation threshold, cavitation will occur, forming a new emulsification of the waste oil, which increases the difficulty of dehydrating the waste oil.

[0063] 3. According to Example 1, the temperature of the ultrasonic demulsification process was changed, and the water content in the preliminary dehydrated oily scum was tested respectively.

[0064] The test results are as follows Figure 7As shown in the figure, it can be seen that with the increase of ultrasonic treatment temperature, the moisture content of the sludge first decreases and then increases; the scum dehydration rate reaches the lowest at 60 ℃, which is mainly because: with the increase of ultrasonic temperature, the viscosity of the scum decreases, and under the action of ultrasonic mechanical vibration, the movement of oil droplets intensifies, the number of collisions and aggregations between oil droplets increases, and large oil droplets are quickly formed, which improves the dehydration effect. At the same time, the increase in temperature will lead to a decrease in the film stability and mechanical strength of the oil-water interface, making it easier to achieve the aggregation of oil droplets. The scum dehydration rate gradually decreases at high temperatures, because at low temperatures, the ultrasonic cavitation effect increases with the increase of temperature, and the dehydration effect is improved; after exceeding the critical temperature point of the sample, the sound intensity and cavitation of the ultrasonic wave will gradually weaken, making the dehydration effect worse.

[0065] 3. Demulsifier performance characterization 1. Reference Figure 8 , is the XRD pattern of the demulsifier prepared in Example 1, which illustrates the successful preparation of the demulsifier.

[0066] 2. Active oxygen generation performance test: The demulsifiers prepared in Example 1, Comparative Example 2 and Comparative Example 3 were tested for their ability to generate active oxygen according to the following method: The demulsifier was added to deionized water and ultrasonically dispersed to prepare a dispersion with a concentration of 0.2 mg / mL. Ultrasonic standing waves were applied at a frequency of 45 kHz and an ultrasonic power of 350 W. The reactive oxygen species fluorescent probe (ROS Brite 570, Ex (nm) 554Em (nm) 568, Xi'an Baiying Biotechnology Co., Ltd.) was used to measure the reactive oxygen species content at different treatment times. The higher the fluorescence intensity, the higher the reactive oxygen species content.

[0067] The test results are as follows Fig. 9 As shown, it can be seen that the demulsifier of Example 1 can efficiently generate active oxygen under ultrasound. The reason for the decrease in the efficiency of active oxygen generation in Comparative Example 1 is that the porous ferroferric oxide is not doped with nickel, which affects the stability and porosity of the porous structure of the demulsifier, affects the loading of the carbon dots, and reduces the number of active sites. The decrease in the efficiency of active oxygen generation in Comparative Example 2 shows that the doping of ruthenium in the carbon dots can improve the ability of the demulsifier to generate active oxygen under ultrasound.

[0068] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A comprehensive treatment process for oily scum based on ultrasonic scum dehydration, characterized in that: The following steps are involved: 1) Alkalization of oily scum: add alkali to the oily scum containing aluminum salt flocculant to adjust the pH; 2) Ultrasonic demulsification: add demulsifier to the oily scum after alkalization treatment, stir, and then apply ultrasonic waves for treatment; 3) Dehydration of oily scum: After ultrasonic demulsification, let it stand for sedimentation and stratification, separate the lower water phase as scum wastewater, and separate the upper oil phase as dehydrated oily scum; 4) Post-treatment of scum wastewater: Combine ultrasound and electro-Fenton method to oxidatively degrade COD in scum wastewater; 5) Post-treatment of oily scum after dehydration: distill the oily scum after dehydration to separate the oil phase, water phase and final residue; 6) Aluminum salt recovery: The final residue is acidified to obtain a regenerated aluminum salt solution.

2. The comprehensive treatment process for oily scum based on ultrasonic scum dehydration according to claim 1 is characterized in that: Step 1) is specifically as follows: Na2CO3 is added to the oily scum containing the aluminum salt flocculant and stirred evenly, and the pH value of the oily scum is adjusted to 7-9 to obtain the oily scum after alkalization treatment.

3. The comprehensive treatment process for oily scum based on ultrasonic scum dehydration according to claim 1 is characterized in that: Step 2) is as follows: The oily scum after alkalization treatment is injected into a container, a demulsifier with a mass concentration of 0.1-2% is added, stirred at 300-1500rpm for 15-45min, then heated to 55-75℃, ultrasonic standing wave is applied, the frequency is 10-50kHz, the ultrasonic power is 100-400W, and the ultrasonic treatment time is 2-15min.

4. The comprehensive treatment process for oil-containing scum based on ultrasonic scum dehydration according to claim 1 is characterized in that: Step 4) is as follows: The scum wastewater was introduced into the electrolytic cell, and Na2SO4 with a concentration of 0.01-0.05 mol / L was added, and then H2O2 solution was added in batches, and the final amount of H2O2 added was controlled to be 0.5-2.1 mmol / L. The electro-Fenton reaction was carried out at 28-32°C and a stirring speed of 40-160r / min. The electro-Fenton reaction time was 50-90min, and the current density was controlled to be 5-20mA / cm 2 , after the electro-Fenton reaction has been carried out for a set time, an ultrasonic standing wave is applied simultaneously until the electro-Fenton reaction is completed, and the demulsifier is recovered by magnetic absorption; Among them, the frequency of ultrasound is 25-60kHz and the ultrasonic power is 200-400W.

5. The comprehensive treatment process for oily scum based on ultrasonic scum dehydration according to claim 1 is characterized in that: Step 5) is as follows: The dehydrated oil-containing scum is distilled into a stirred reactor, and distilled under reduced pressure under heating and stirring to separate the water phase and the oil phase. The product at the bottom of the reactor is the final residue.

6. The comprehensive treatment process for oil-containing scum based on ultrasonic scum dehydration according to claim 1 is characterized in that: Step 6) is as follows: Add 5-20 mg / L hydrochloric acid to the final residue after distillation for acidification treatment, neutralize the final residue until the alkalinity B value reaches the set value, and obtain a regenerated aluminum salt solution.

7. The comprehensive treatment process for oil-containing scum based on ultrasonic scum dehydration according to any one of claims 1 to 6, characterized in that: The following steps are involved: 1) Alkalization of oily scum: Adding a 20% Na2CO3 aqueous solution to the oily scum containing the aluminum salt flocculant, stirring evenly, adjusting the pH value of the oily scum to 7.25, and obtaining an alkalized oily scum; 2) Ultrasonic demulsification: The oily scum after alkalization treatment was injected into a container, and a demulsifier with a mass concentration of 0.6% was added, stirred at 1000 rpm for 10 min, and then heated to 60°C, and ultrasonic standing waves were applied with a frequency of 20 kHz and an ultrasonic power of 300 W. The ultrasonic treatment time was 6 min. 3) Dehydration of oily scum: After ultrasonic demulsification, the mixture is allowed to stand for sedimentation and stratification, and the lower water phase is separated as scum wastewater, and the upper oil phase is separated as oily scum after dehydration; 4) Post-treatment of scum wastewater: The scum wastewater was introduced into the electrolytic cell, and Na2SO4 with a concentration of 0.02 mol / L was added. Then H2O2 solution was added in batches, and the final amount of H2O2 added was controlled to be 1.05 mmol / L. The electro-Fenton reaction was carried out at 30°C and a stirring speed of 80 r / min. The electro-Fenton reaction time was 75 min, and the current density was controlled to be 10.2 mA / cm 2 After the electro-Fenton reaction has been carried out for 60 minutes, an ultrasonic standing wave is applied simultaneously until the electro-Fenton reaction is completed, and the demulsifier is recovered by magnetic absorption; the demulsifier is recovered by magnetic absorption; Among them, the frequency of the ultrasonic wave is 45kHz and the ultrasonic power is 350W; 5) Post-treatment of oily scum after dehydration: The dehydrated oily scum is distilled and added into a stirred reactor, and stirred at a speed of 150 rpm while heating, and distilled under reduced pressure to separate the water phase and the oil phase. The product at the bottom of the reactor is the final residue; 6) Aluminum salt recovery: Add 10 mg / L hydrochloric acid to the final residue after distillation for acidification, neutralize the final residue to an alkalinity B value of 1.2, and obtain a regenerated aluminum salt solution.

8. The comprehensive treatment process for oily scum based on ultrasonic scum dehydration according to claim 1 is characterized in that: The demulsifier is prepared by the following method: 2-1) Preparation of nickel-doped porous ferroferric oxide: 0.5-2g FeCl3·6H2O, 0.15-0.7g NiCl2·6H2O, 25-100mL ethanol, 20-90mL cyclohexane are added to 100-300mL ethylene glycol, ultrasonically dispersed for 15-60min, then 1.6-6.4g urotropine is added, stirred for 5-30min, the resulting mixed solution is transferred to a polytetrafluoroethylene-lined reactor, reacted at 150-175°C for 4-8h, cooled to room temperature after the reaction, filtered, the solid product is washed with ethanol and deionized water in turn, dried at 60-90°C for 3-10h, then calcined at 450-600°C in a nitrogen atmosphere for 2-6h, cooled to room temperature, and nickel-doped porous ferrosoferric oxide is obtained, which is recorded as Ni-Fe3O4; 2-2) Loading ruthenium-doped carbon dots on nickel-doped porous ferroferric oxide: 2-2-1) Add 291-1164 mg of aminoacridine yellow, 384-1536 mg of citric acid, 120-480 mg of acetic acid, 45-180 mg of ethylenediamine, and 52-208 mg of RuCl3·3H2O to a mixed solution consisting of 50-200 mL of ethanol and 25-100 mL of deionized water, and disperse by ultrasonication for 3-20 min to obtain a precursor solution 1; 2-2-2) Take 0.6-2.4g of nickel-doped porous ferroferric oxide and add it to 50-200mL of deionized water, and ultrasonically disperse it for 10-30min to obtain precursor solution 2; 2-2-3) Precursor solution 1 is added to precursor solution 2 under stirring, and stirred at 500-2500 rpm for 15-60 min. The resulting mixture is transferred to a polytetrafluoroethylene-lined reactor and reacted at 170-210° C. for 6-24 h. After the reaction is completed, it is cooled to room temperature and filtered. The solid product is washed with deionized water and vacuum dried at 70-110° C. for 6-24 h to obtain the demulsifier, which is recorded as Ni-Fe3O4@Ru-CDs.

9. The comprehensive treatment process for oil-containing scum based on ultrasonic scum dehydration according to claim 2 is characterized in that: The demulsifier is prepared by the following method: 2-1) Preparation of nickel-doped porous ferroferric oxide: 1 g FeCl3·6H2O, 0.35 g NiCl2·6H2O, 50 mL ethanol, and 45 mL cyclohexane were added to 150 mL ethylene glycol, and ultrasonically dispersed for 30 min. Then, 3.2 g urotropine was added and stirred for 10 min. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 165 ° C for 6 h. After the reaction was completed, it was cooled to room temperature and filtered. The solid product was washed with ethanol and deionized water in turn, dried at 70 ° C for 6 h, and then calcined at 550 ° C in a nitrogen atmosphere for 4 h. It was cooled to room temperature to obtain nickel-doped porous ferrosoferric oxide, which was recorded as Ni-Fe3O4. 2-2) Loading ruthenium-doped carbon dots on nickel-doped porous ferroferric oxide: 2-2-1) 582 mg of aminoacridine yellow, 768 mg of citric acid, 240 mg of acetic acid, 90 mg of ethylenediamine, and 104 mg of RuCl3·3H2O were added to a mixed solution consisting of 100 mL of ethanol and 50 mL of deionized water, and ultrasonically dispersed for 5 minutes to obtain a precursor solution 1; 2-2-2) Take 1.2g of nickel-doped porous ferroferric oxide and add it to 100mL of deionized water, and disperse it by ultrasonic for 15min to obtain precursor solution 2; 2-2-3) Precursor solution 1 was added to precursor solution 2 under stirring, and the mixture was stirred at 1000 rpm for 30 min. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 180° C. for 12 h. After the reaction was completed, the mixture was cooled to room temperature and filtered. The solid product was washed with deionized water and vacuum dried at 90° C. for 12 to obtain the demulsifier, which was recorded as Ni-Fe3O4@Ru-CDs.

10. A comprehensive treatment system for oily scum based on ultrasonic scum dehydration, which uses the process as described in any one of claims 1 to 9 to treat the oily scum.

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