An oil-containing dross comprehensive treatment process and system based on ultrasonic dross dewatering

Abstract

This invention discloses a comprehensive treatment process for oily scum based on ultrasonic dewatering, comprising the following steps: 1) alkalization of the oily scum; 2) ultrasonic demulsification: adding a demulsifier to the alkalized oily scum, stirring, and then applying ultrasound for treatment; 3) dewatering of the oily scum: after ultrasonic demulsification, allowing it to settle and separate into layers, separating the lower aqueous phase as scum wastewater, and separating the upper oil phase as dewatered oily scum; 4) post-treatment of the scum wastewater; 5) post-treatment of the dewatered oily scum; and 6) aluminum salt recovery. This invention's process enables the resource-based treatment of oily scum, reducing environmental pollution and recovering useful resources, resulting in significant economic and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of oily scum and wastewater treatment technology, and particularly to a comprehensive treatment process for oily scum based on ultrasonic scum dewatering. Background Technology

[0002] Refinery oily sludge refers to the oily sludge produced when flocculants (currently aluminum-based inorganic coagulants are commonly used) are added to the flotation section of wastewater treatment in petrochemical enterprises. Oil droplets and solid particles in the water adhere to tiny air bubbles and are carried to the surface. It is mainly composed of negatively charged hydrophilic colloidal particles, has a complex composition, is difficult to dehydrate, and the amount of sludge increases significantly as the quality of crude oil deteriorates (Han Pingfang, Zhou Yinfei, Lü Xiaoping. Research on flocculation and dewatering of oily sludge from refineries [J]. Environmental Science and Technology, 2006, 29(11): 91-95). Currently, enterprises generally mix the sludge with other oily sludge, add flocculants, and then mechanically separate and dehydrate it until the water content drops to about 85%, before landfilling it as hazardous waste. Due to severe emulsification of the sludge, the existing dewatering process has limited effectiveness, and crude oil recovery is difficult, which increases the burden of hazardous waste treatment for enterprises and wastes crude oil resources.

[0003] Methods for demulsifying scum can be broadly categorized into three types: physical, chemical, and biological. Physical methods primarily include gravity sedimentation, centrifugation, filtration, electric field methods, microwave radiation, ultrasonic methods, and membrane demulsification. Chemical methods mainly involve adding demulsifiers.

[0004] The ultrasonic method involves radiating ultrasonic energy into crude oil emulsions, causing a series of ultrasonic effects such as stirring, collision, aggregation, cavitation, heating, and negative pressure, thereby disrupting the oil-water interface film. This method can achieve demulsification, desalting, and dehydration with little or no demulsifier. Because ultrasound has good conductivity in both oil and water, this method is suitable for various types of emulsions. For oil-in-water emulsions, wastewater recovery oil, and aged oils produced by tertiary oil recovery, the complexity of their chemical composition and emulsion structure makes conventional methods difficult for demulsification, desalting, and dehydration. Sonochemical methods can be used for desalting and dehydration of such oils with good results (Li Shuqin, Cheng Yongqing, Zhang Xumin. Study on Sonochemical Method for Demulsification and Dehydration of Water-Bearing Crude Oil [J]. Tianjin Chemical Industry, 1997, 4: 22-24.).

[0005] The demulsifying agent method is a chemical dehydration method that mainly utilizes the displacement effect of the demulsifier. After the demulsifier is added, it diffuses towards the oil-water interface. Because 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 at the oil-water interface. It also forms a mixed film with the film-forming substances in the crude oil with a lower interfacial film strength than the original interfacial film, which leads to the destruction of the interfacial film and releases the water trapped inside the film. The water droplets aggregate to form large water droplets and settle to the bottom, and the oil and water phases separate, thus achieving the purpose of demulsification (Kotsaridou. Demulsifying water-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 combining electrochemistry and the Fenton reaction. It is primarily used for the degradation of organic pollutants in water. The core of the electro-Fenton reaction lies in the electrolysis process that generates hydrogen peroxide (H₂O₂) and ferrous ions (Fe²⁺). Under acidic conditions, these substances interact to generate highly oxidizing hydroxyl radicals (·OH). These hydroxyl radicals can rapidly attack organic molecules, breaking them down into smaller molecules, thereby achieving the goal of pollutant degradation.

[0007] Currently, the treatment processes for oily scum generally suffer from problems such as poor demulsification in the early stage and reduced COD removal efficiency in the later stage, making it difficult to meet application requirements.

[0008] Therefore, it is now necessary to improve existing technologies to provide reliable solutions. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a comprehensive treatment process for oily scum based on ultrasonic scum dewatering, which addresses the shortcomings of the prior art.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: The present invention provides a comprehensive treatment process for oily scum based on ultrasonic scum dewatering, comprising the following steps:

[0011] 1) Alkalization of oily scum: Add alkali to the oily scum containing aluminum salt flocculants to adjust the pH;

[0012] 2) Ultrasonic demulsification: Add demulsifier to the oily sludge after alkalization treatment, stir, and then apply ultrasound for treatment;

[0013] 3) Dewatering of oily scum: After ultrasonic demulsification, the mixture is allowed to stand, settle and separate into layers. The lower aqueous phase is separated as scum wastewater, and the upper oil phase is separated as dewatered oily scum.

[0014] 4) Post-treatment of scum wastewater: Combining ultrasonic and electro-Fenton methods to oxidize and degrade COD in scum wastewater;

[0015] 5) Post-treatment of oily scum after dehydration: Distill the oily scum after dehydration to separate the oil phase, water phase and final residue;

[0016] 6) Aluminum salt recovery: The final residue is acidified to obtain a recycled aluminum salt solution.

[0017] Preferably, step 1) specifically involves: adding Na2CO3 to the oily scum containing aluminum salt flocculant and stirring evenly, adjusting the pH value of the oily scum to 7-9, and obtaining the alkalized oily scum.

[0018] Preferably, step 2) specifically includes:

[0019] The oily scum after alkalization is injected into a container, and a demulsifier with a mass concentration of 0.1-2% is added. The mixture is stirred at 300-1500 rpm for 15-45 min, then heated to 55-75℃, and ultrasonic standing wave is applied with a frequency of 10-50 kHz and an ultrasonic power of 100-400W for 2-15 min.

[0020] Preferably, step 4) specifically includes:

[0021] The scum wastewater is introduced into an electrolytic cell, and Na2SO4 with a concentration of 0.01-0.05 mol / L is added. Then, H2O2 solution is added in portions, controlling the final amount of H2O2 added to be 0.5-2.1 mmol / L. The electro-Fenton reaction is carried out at 28-32℃ and a stirring speed of 40-160 r / min for 50-90 min, with the current density controlled at 5-20 mA / cm². 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 ends, and the demulsifier is magnetically collected.

[0022] The ultrasonic frequency is 25-60kHz and the ultrasonic power is 200-400W.

[0023] Preferably, step 5) specifically includes:

[0024] The dehydrated oily scum is distilled into a stirred reactor and then distilled under reduced pressure with heating and stirring to separate the aqueous and oil phases. The product at the bottom of the reactor is the final residue.

[0025] Preferably, step 6) specifically includes:

[0026] Add 5-20 mg / L of 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 the regenerated aluminum salt solution.

[0027] Preferably, the comprehensive treatment process for oily scum based on ultrasonic scum dewatering includes the following steps:

[0028] 1) Alkalization of oily scum:

[0029] Add a 20% Na2CO3 aqueous solution to the oily scum containing aluminum salt flocculant, stir evenly, and adjust the pH value of the oily scum to 7.25 to obtain the alkalized oily scum.

[0030] 2) Ultrasonic demulsification:

[0031] The oily scum after alkalization was injected into a container, a demulsifier with a mass concentration of 0.6% was added, and the mixture was stirred at 1000 rpm for 10 min. Then it was heated to 60°C, and ultrasonic standing wave was applied with a frequency of 20 kHz and an ultrasonic power of 300 W for 6 min.

[0032] 3) Dewatering of oily scum:

[0033] After ultrasonic demulsification, the mixture is allowed to stand, settle and separate into layers. The lower aqueous phase is separated as scum wastewater, and the upper oil phase is separated as oily scum after dehydration.

[0034] 4) Post-treatment of scum wastewater:

[0035] The scum wastewater was introduced into an electrolytic cell, and 0.02 mol / L Na2SO4 was added. Then, H2O2 solution was added in portions, with the final H2O2 addition controlled at 1.05 mmol / L. An electro-Fenton reaction was carried out at 30℃ and a stirring speed of 80 r / min for 75 min, with the current density controlled at 10.2 mA / cm². 2 After the electro-Fenton reaction has been going on for 60 minutes, an ultrasonic standing wave is applied until the electro-Fenton reaction ends, and the demulsifier is magnetically recovered.

[0036] Among them, the ultrasonic frequency is 45kHz and the ultrasonic power is 350W;

[0037] 5) Post-treatment of oily scum after dehydration:

[0038] The dehydrated oily scum was distilled into a stirred reactor and stirred at 150 rpm while being heated. The aqueous phase and oil phase were separated by vacuum distillation and the product at the bottom of the reactor was the final residue.

[0039] 6) Aluminum salt recovery: Add 10 mg / L hydrochloric acid to the final residue after distillation for acidification treatment, neutralize the final residue to the alkalinity B value of 1.2, and obtain a regenerated aluminum salt solution.

[0040] Preferably, the demulsifier is prepared by the following method:

[0041] 2-1) Preparation of nickel-doped porous iron(III) oxide:

[0042] Take 0.5-2g FeCl3·6H2O, 0.15-0.7g NiCl2·6H2O, 25-100mL ethanol, and 20-90mL cyclohexane and add them to 100-300mL ethylene glycol. Disperse the mixture by sonication for 15-60min. Then add 1.6-6.4g hexamethylenetetramine and stir for 5-30min. Transfer the resulting mixture to a polytetrafluoroethylene-lined reactor and react at 150-175℃ for 4-8h. After the reaction is complete, cool to room temperature, filter, and wash the solid product with ethanol and deionized water in sequence. Dry at 60-90℃ for 3-10h, and then calcine at 450-600℃ under a nitrogen atmosphere for 2-6h. Cool to room temperature to obtain nickel-doped porous iron(III) oxide, denoted as Ni-Fe3O4.

[0043] 2-2) Loading ruthenium-doped carbon dots onto nickel-doped porous iron oxide:

[0044] 2-2-1) Take 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 and add them to a mixed solution consisting of 50-200 mL of ethanol and 25-100 mL of deionized water. Disperse the mixture by sonication for 3-20 min to obtain precursor solution 1.

[0045] 2-2-2) Take 0.6-2.4g of nickel-doped porous iron(III) oxide and add it to 50-200mL of deionized water. Disperse it by ultrasonication for 10-30min to obtain precursor solution 2.

[0046] 2-2-3) Add precursor liquid 1 to precursor liquid 2 under stirring, stir at 500-2500 rpm for 15-60 min, transfer the resulting mixture to a polytetrafluoroethylene-lined reactor, react at 170-210℃ for 6-24 h, cool to room temperature after the reaction, filter, wash the solid product with deionized water, and vacuum dry at 70-110℃ for 6-24 h to obtain the demulsifier, denoted as Ni-Fe3O4@Ru-CDs.

[0047] Preferably, the demulsifier is prepared by the following method:

[0048] 2-1) Preparation of nickel-doped porous iron(III) oxide:

[0049] Take 1g FeCl3·6H2O, 0.35g NiCl2·6H2O, 50mL ethanol, and 45mL cyclohexane and add them to 150mL ethylene glycol. Disperse the mixture by sonication for 30min. Then add 3.2g hexamethylenetetramine and stir for 10min. Transfer the resulting mixture to a polytetrafluoroethylene-lined reactor and react at 165℃ for 6h. After the reaction is complete, cool to room temperature, filter, wash the solid product with ethanol and deionized water in sequence, dry at 70℃ for 6h, and then calcine at 550℃ under a nitrogen atmosphere for 4h. Cool to room temperature to obtain nickel-doped porous iron(III) oxide, denoted as Ni-Fe3O4.

[0050] 2-2) Loading ruthenium-doped carbon dots onto nickel-doped porous iron oxide:

[0051] 2-2-1) Take 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 and add them to a mixed solution consisting of 100 mL of ethanol and 50 mL of deionized water. Disperse the mixture by sonication for 5 min to obtain precursor solution 1.

[0052] 2-2-2) Take 1.2g of nickel-doped porous iron oxide and add it to 100mL of deionized water. Disperse it by ultrasonication for 15min to obtain precursor solution 2.

[0053] 2-2-3) Add precursor liquid 1 to precursor liquid 2 under stirring, stir at 1000 rpm for 30 min, transfer the resulting mixture to a polytetrafluoroethylene-lined reactor, react at 180 °C for 12 h, cool to room temperature after the reaction, filter, wash the solid product with deionized water, and vacuum dry at 90 °C for 12 h to obtain the demulsifier, denoted as Ni-Fe3O4@Ru-CDs.

[0054] The present invention also provides a comprehensive treatment system for oily scum based on ultrasonic scum dewatering, which uses the process described above to treat oily scum.

[0055] The beneficial effects of this invention are:

[0056] The comprehensive treatment process for oily scum provided by this invention first alkalizes the scum, then demulsifies it using a combination of demulsifier and ultrasound, followed by gravity sedimentation to achieve oil-water stratification. The lower layer is scum wastewater containing demulsifier, and the upper oil phase is preliminarily dehydrated oily scum. The scum wastewater containing demulsifier is further treated using a combination of electro-Fenton process and ultrasound, achieving efficient degradation of organic components in the water through strong oxidation and removing COD. The preliminarily dehydrated oily scum is then separated into aqueous phase, oil phase, and final residue through distillation. The oil phase is recovered as a byproduct, the aqueous phase can be further processed, and the final residue is acidified with hydrochloric acid to recover recycled aluminum salts. This process enables the resource-based treatment of oily scum, reducing environmental pollution and recovering useful resources, resulting in significant economic and environmental benefits.

[0057] The demulsifier of this invention is obtained by in-situ loading ruthenium-doped carbon dots onto nickel-doped porous iron oxide. Utilizing the acoustic sensitivity of the ruthenium-doped carbon dots, it can efficiently generate active oxygen under ultrasonic action, exhibiting excellent oxidation capacity. It can achieve efficient demulsification in the early dewatering stage and further achieve efficient COD removal in the later scum wastewater treatment stage. At the same time, due to its porous structure, the demulsifier can also provide physical adsorption.

[0058] In the scum wastewater treatment stage of this invention, COD removal is achieved through the strong oxidizing effect of ·OH generated by the electro-Fenton reaction. When combined with ultrasound, on the one hand, the mass transfer rate of homogeneous and heterogeneous systems can be enhanced, allowing ·OH in the reaction system to react with organic pollutant molecules in the wastewater in a timely manner. On the other hand, under the action of ultrasound, the demulsifier in the scum wastewater can also efficiently generate active oxygen, thereby further enhancing the COD removal effect. Attached Figure Description

[0059] Figure 1 The results are the test results of the water content of the preliminary dehydrated oily scum in the processes of Examples 1-3 and Comparative Examples 1-4;

[0060] Figure 2 The results are the test results of COD removal rate in the processes of Examples 1-3 and Comparative Examples 1-4;

[0061] Figure 3 The results are the test results of oil recovery rate in the processes of Examples 1-3 and Comparative Examples 1-4;

[0062] Figure 4 The results are the test results of aluminum salt recovery rates in the processes of Examples 1-3 and Comparative Examples 1-4;

[0063] Figure 5 The test results show the effect of ultrasonic treatment time on the water content in the initially dehydrated oily scum.

[0064] Figure 6 The test results show the effect of ultrasonic power on the water content in the initially dehydrated oily scum.

[0065] Figure 7 The test results show the effect of ultrasonic demulsification temperature on the water content in the initially dehydrated oily scum.

[0066] Figure 8 The XRD pattern of the demulsifier prepared in Example 1;

[0067] Figure 9 The test results are for the reactive oxygen generation performance of the demulsifiers prepared in Example 1, Comparative Example 2, and Comparative Example 3. Detailed Implementation

[0068] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0069] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0070] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. For examples where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments whose manufacturers are not specified, they are all commercially available products.

[0071] In a first aspect, the present invention provides a comprehensive treatment process for oily scum based on ultrasonic scum dewatering, comprising the following steps:

[0072] 1) Alkalization of oily scum:

[0073] Add Na2CO3 to the oily scum containing aluminum salt flocculant and stir evenly to adjust the pH value of the oily scum to 7-9, thus obtaining the alkalized oily scum.

[0074] 2) Ultrasonic demulsification:

[0075] The oily scum after alkalization is injected into a container, and a demulsifier with a mass concentration of 0.1-2% is added. The mixture is stirred at 300-1500 rpm for 15-45 minutes, then heated to 55-75℃, and ultrasonic standing wave is applied at a frequency of 10-50 kHz and an ultrasonic power of 100-400W for 2-15 minutes.

[0076] 3) Dewatering of oily scum:

[0077] After ultrasonic demulsification, the mixture is allowed to stand, settle and separate into layers. The lower aqueous phase is separated as scum wastewater, and the upper oil phase is separated as oily scum after dehydration.

[0078] 4) Post-treatment of scum wastewater:

[0079] The scum wastewater is introduced into an electrolytic cell, and Na2SO4 with a concentration of 0.01-0.05 mol / L is added. Then, H2O2 solution is added in portions, controlling the final amount of H2O2 added to be 0.5-2.1 mmol / L. The electro-Fenton reaction is carried out at 28-32℃ and a stirring speed of 40-160 r / min for 50-90 min, with the current density controlled at 5-20 mA / cm². 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 ends, and the demulsifier is magnetically collected; the remaining water can be further filtered and then subjected to subsequent biochemical treatment.

[0080] The ultrasonic frequency is 25-60kHz and the ultrasonic power is 200-400W.

[0081] 5) Post-treatment of oily scum after dehydration:

[0082] The dehydrated oily scum is distilled into a stirred reactor and then distilled under reduced pressure with heating and stirring to separate the aqueous and oil phases. The product at the bottom of the reactor is the final residue.

[0083] 6) Aluminum salt recovery:

[0084] Add 5-20 mg / L of 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 the regenerated aluminum salt solution.

[0085] In a preferred embodiment, the demulsifier is prepared by the following method:

[0086] 2-1) Preparation of nickel-doped porous iron(III) oxide:

[0087] Take 0.5-2g FeCl3·6H2O, 0.15-0.7g NiCl2·6H2O, 25-100mL ethanol, and 20-90mL cyclohexane and add them to 100-300mL ethylene glycol. Disperse the mixture by sonication for 15-60min. Then add 1.6-6.4g hexamethylenetetramine and stir for 5-30min. Transfer the resulting mixture to a polytetrafluoroethylene-lined reactor and react at 150-175℃ for 4-8h. After the reaction is complete, cool to room temperature, filter, and wash the solid product with ethanol and deionized water in sequence. Dry at 60-90℃ for 3-10h, and then calcine at 450-600℃ under a nitrogen atmosphere for 2-6h. Cool to room temperature to obtain nickel-doped porous iron(III) oxide, denoted as Ni-Fe3O4.

[0088] 2-2) Loading ruthenium-doped carbon dots onto nickel-doped porous iron oxide:

[0089] 2-2-1) Take 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 and add them to a mixed solution consisting of 50-200 mL of ethanol and 25-100 mL of deionized water. Disperse the mixture by sonication for 3-20 min to obtain precursor solution 1.

[0090] 2-2-2) Take 0.6-2.4g of nickel-doped porous iron(III) oxide and add it to 50-200mL of deionized water. Disperse it by ultrasonication for 10-30min to obtain precursor solution 2.

[0091] 2-2-3) Add precursor solution 1 to precursor solution 2 under stirring, stir at 500-2500 rpm for 15-60 min, transfer the resulting mixture to a polytetrafluoroethylene-lined reactor, react at 170-210℃ for 6-24 h, cool to room temperature after the reaction, filter, wash the solid product with deionized water, and vacuum dry at 70-110℃ for 6-24 h to obtain the demulsifier, denoted as Ni-Fe3O4@Ru-CDs.

[0092] In a second aspect, the present invention provides a comprehensive treatment system for oily scum based on ultrasonic scum dewatering, which uses the above-described process to treat oily scum.

[0093] In the comprehensive treatment process for oily scum provided by the present invention, the scum is first alkalized, then demulsified by a combination of demulsifier and ultrasound, and oil-water separation is achieved by gravity sedimentation. The lower layer is scum wastewater containing demulsifier, and the upper oil phase is preliminarily dehydrated oily scum.

[0094] Scum wastewater containing demulsifiers is further treated with a process combining electro-Fenton method and ultrasound, which achieves efficient degradation of organic components in the water through strong oxidation and removes COD.

[0095] The initial dehydrated oily scum is separated into aqueous phase, oil phase, and final residue through distillation. The oil phase is recovered as a byproduct, the recovered aqueous phase can be further processed, and the final residue is acidified with hydrochloric acid to recover recycled aluminum salts. This invention enables the resource-based treatment of oily scum, reducing environmental pollution while recovering useful resources, resulting in significant economic and environmental benefits.

[0096] The demulsifier of this invention is obtained by in-situ loading ruthenium-doped carbon dots onto nickel-doped porous iron oxide. Utilizing the acoustic sensitivity of the ruthenium-doped carbon dots, it can efficiently generate active oxygen under ultrasonic action, exhibiting excellent oxidation capacity. It can achieve efficient demulsification in the initial dewatering stage and further achieve efficient COD removal in the later stage of scum wastewater treatment. Simultaneously, due to its porous structure, the demulsifier can also provide physical adsorption. The preparation method and mechanism of action are described in detail below to facilitate understanding of this invention.

[0097] This invention first prepares nickel-doped porous iron(III) oxide with a rich pore structure by combining conventional hydrothermal reaction with calcination. The nickel-doped porous iron(III) oxide has certain oxidizing properties and good magnetic properties. Nickel doping can improve its high temperature resistance and magnetic properties, improve the stability of the pore structure, and reduce the collapse of pores during calcination, thereby helping to increase the specific surface area and enhance the adsorption performance.

[0098] Then, using aminoacridine yellow, citric acid, acetic acid, and ethylenediamine as the main raw materials, and RuCl3·3H2O as the dopant component, ruthenium-doped carbon dots were grafted in situ onto nickel-doped porous iron oxide using a one-pot hydrothermal method to obtain a demulsifier.

[0099] In the demulsifier of the present invention, the ruthenium-doped carbon dots inherit the acoustic and thermal properties of aminoacridine yellow, and can efficiently generate active oxygen under ultrasonic action; wherein the doped ruthenium generates ruthenium oxide (RuO2) during the reaction, which itself has high oxidizing power. At the same time, due to the change in electronic structure caused by Ru doping, new surface energy can be formed, increasing active sites and enhancing the acoustic effect of carbon dots, thereby enhancing the efficiency of active oxygen generation and significantly improving the oxidizing power of the demulsifier.

[0100] The demulsifier in this invention is primarily based on an oxidative demulsification mechanism. The working principle of oxidative demulsification is mainly to destroy the emulsifier in the emulsion through an oxidation reaction. In an emulsion, the emulsifier reduces the interfacial tension between oil and water, allowing them to form a stable mixture. The oxidative demulsifier, however, can undergo a redox reaction with the emulsifier, causing it to lose its activity and thus reducing the stability of the emulsion. Under ultrasonic assistance, the demulsifier in this invention exhibits strong oxidizing properties, capable of oxidizing and degrading the oily residue coated on the water surface, disrupting the stable oil-water mixture, and thus promoting oil-water separation. Furthermore, during the demulsification process, the stirring, collision, aggregation, cavitation, heating, and negative pressure effects generated by ultrasound can also destroy the oil-water interfacial film, achieving demulsification. Therefore, in this invention, the ultrasound in the demulsification process primarily achieves demulsification through physical effects, while also assisting ruthenium-doped carbon dots in achieving chemical demulsification through strong oxidation. The combination of these two aspects significantly improves the demulsification effect.

[0101] Furthermore, the strong oxidizing properties of this demulsifier can work in conjunction with the electro-Fenton reaction to achieve efficient COD degradation in the subsequent scum wastewater treatment stage. Therefore, in addition to playing a role in oxidizing and degrading the oil film in the demulsification operation stage, the demulsifier can also play a role in oxidizing and degrading COD in the subsequent scum wastewater treatment process.

[0102] The electro-Fenton reaction degrades pollutants primarily through the strong oxidizing effect of ·OH radicals. When combined with ultrasound, the cavitation bubbles generated under ultrasonic action collapse with intense impacts and microjets, creating localized and intense turbulence. This enhances the mass transfer rate between homogeneous and heterogeneous systems, allowing ·OH radicals in the reaction system to react promptly with organic pollutant molecules in the wastewater, thus improving the reaction efficiency. During the final collapse stage of the cavitation bubbles, localized high temperatures and pressures are generated, creating localized hotspot effects, accompanied by powerful shock waves, high-speed microjets, and the generation of free radicals. These free radicals can decompose organic pollutants in the wastewater into smaller molecules. All these factors contribute to a relatively rapid increase in COD removal rate. Furthermore, under ultrasonic action, demulsifiers in scum wastewater can efficiently generate active oxygen, further enhancing the COD removal effect.

[0103] The above is the general concept of the present invention. Based on this, detailed embodiments and comparative examples are provided below to further illustrate the present invention.

[0104] Example 1

[0105] A comprehensive treatment process for oily scum based on ultrasonic scum dewatering includes the following steps:

[0106] 1) Alkalization of oily scum:

[0107] Add a 20% Na2CO3 aqueous solution to the oily scum containing aluminum salt flocculant, stir evenly, and adjust the pH value of the oily scum to 7.25 to obtain the alkalized oily scum.

[0108] 2) Ultrasonic demulsification:

[0109] The oily scum after alkalization was injected into a container, a demulsifier with a mass concentration of 0.6% was added, and the mixture was stirred at 1000 rpm for 10 min. Then it was heated to 60°C, and ultrasonic standing wave was applied with a frequency of 20 kHz and an ultrasonic power of 300 W for 6 min.

[0110] 3) Dewatering of oily scum:

[0111] After ultrasonic demulsification, the mixture is allowed to stand, settle and separate into layers. The lower aqueous phase is separated as scum wastewater, and the upper oil phase is separated as oily scum after dehydration.

[0112] 4) Post-treatment of scum wastewater:

[0113] The scum wastewater was introduced into an electrolytic cell, and 0.02 mol / L Na2SO4 was added. Then, H2O2 solution was added in portions, with the final H2O2 addition controlled at 1.05 mmol / L. An electro-Fenton reaction was carried out at 30℃ and a stirring speed of 80 r / min for 75 min, with the current density controlled at 10.2 mA / cm². 2 After the electro-Fenton reaction has been going on for 60 minutes, an ultrasonic standing wave (lasting for 15 minutes) is applied simultaneously until the electro-Fenton reaction ends, and the demulsifier is magnetically collected.

[0114] Among them, the ultrasonic frequency is 45kHz and the ultrasonic power is 350W;

[0115] 5) Post-treatment of oily scum after dehydration:

[0116] The dehydrated oily scum was distilled into a stirred reactor and stirred at 150 rpm while being heated. The aqueous phase and oil phase were separated by vacuum distillation and the product at the bottom of the reactor was the final residue.

[0117] 6) Aluminum salt recovery:

[0118] Add 10 mg / L hydrochloric acid to the final residue after distillation for acidification treatment, and neutralize the final residue until the basicity B value (i.e., the basicity B value) is 1.2 to obtain a regenerated aluminum salt solution.

[0119] The demulsifier is prepared by the following method:

[0120] 2-1) Preparation of nickel-doped porous iron(III) oxide:

[0121] Take 1g FeCl3·6H2O, 0.35g NiCl2·6H2O, 50mL ethanol, and 45mL cyclohexane and add them to 150mL ethylene glycol. Disperse by sonication for 30min, then add 3.2g hexamethylenetetramine (HXMT), stir for 10min, and transfer the resulting mixture to a polytetrafluoroethylene-lined reactor. React at 165℃ for 6h. After the reaction is complete, cool to room temperature, filter, wash the solid product with ethanol and deionized water in sequence, dry at 70℃ for 6h, and then calcine at 550℃ under nitrogen atmosphere for 4h. Cool to room temperature to obtain nickel-doped porous iron(III) oxide, denoted as Ni-Fe3O4.

[0122] 2-2) Loading ruthenium-doped carbon dots onto nickel-doped porous iron oxide:

[0123] 2-2-1) Take 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 and add them to a mixed solution consisting of 100 mL of ethanol and 50 mL of deionized water. Disperse the mixture by sonication for 5 min to obtain precursor solution 1.

[0124] 2-2-2) Take 1.2g of nickel-doped porous iron oxide and add it to 100mL of deionized water. Disperse it by ultrasonication for 15min to obtain precursor solution 2.

[0125] 2-2-3) Add precursor solution 1 to precursor solution 2 under stirring, stir at 1000 rpm for 30 min, transfer the resulting mixture to a polytetrafluoroethylene-lined reactor, react at 180 °C for 12 h, cool to room temperature after the reaction, filter, wash the solid product with deionized water, and vacuum dry at 90 °C for 12 h to obtain the demulsifier, denoted as Ni-Fe3O4@Ru-CDs.

[0126] Example 2

[0127] A comprehensive treatment process for oily scum based on ultrasonic scum dewatering includes the following steps:

[0128] 1) Alkalization of oily scum:

[0129] Add a 20% Na2CO3 aqueous solution to the oily scum containing aluminum salt flocculant, stir evenly, and adjust the pH value of the oily scum to 7.25 to obtain the alkalized oily scum.

[0130] 2) Ultrasonic demulsification:

[0131] The alkalized oily scum was injected into a container, and a demulsifier with a mass concentration of 0.5% was added. The mixture was stirred at 1000 rpm for 10 min, then heated to 60°C, and ultrasonic standing wave was applied at a frequency of 20 kHz and an ultrasonic power of 300 W for 6 min.

[0132] 3) Dewatering of oily scum:

[0133] After ultrasonic demulsification, the mixture is allowed to stand, settle and separate into layers. The lower aqueous phase is separated as scum wastewater, and the upper oil phase is separated as oily scum after dehydration.

[0134] 4) Post-treatment of scum wastewater:

[0135] The scum wastewater was introduced into an electrolytic cell, and 0.015 mol / L Na2SO4 was added. Then, H2O2 solution was added in portions, with the final H2O2 concentration controlled at 1.2 mmol / L. An electro-Fenton reaction was carried out at 30℃ and a stirring speed of 80 r / min for 75 min, with the current density controlled at 10.2 mA / cm².2 After the electro-Fenton reaction has been going on for 60 minutes, an ultrasonic standing wave is applied until the electro-Fenton reaction ends, and the demulsifier is magnetically recovered.

[0136] The ultrasonic frequency is 45kHz and the ultrasonic power is 350W.

[0137] 5) Post-treatment of oily scum after dehydration:

[0138] The dehydrated oily scum was distilled into a stirred reactor and stirred at 150 rpm while being heated. The aqueous phase and oil phase were separated by vacuum distillation and the product at the bottom of the reactor was the final residue.

[0139] 6) Aluminum salt recovery: Add 10 mg / L hydrochloric acid to the final residue after distillation for acidification treatment, neutralize the final residue to the alkalinity B value of 1.2, and obtain a regenerated aluminum salt solution.

[0140] The demulsifier is prepared by the following method:

[0141] 2-1) Preparation of nickel-doped porous iron(III) oxide:

[0142] Take 1g FeCl3·6H2O, 0.35g NiCl2·6H2O, 50mL ethanol, and 45mL cyclohexane and add them to 150mL ethylene glycol. Disperse the mixture by sonication for 30min. Then add 3.2g hexamethylenetetramine and stir for 10min. Transfer the resulting mixture to a polytetrafluoroethylene-lined reactor and react at 165℃ for 6h. After the reaction is complete, cool to room temperature, filter, wash the solid product with ethanol and deionized water in sequence, dry at 70℃ for 6h, and then calcine at 550℃ under a nitrogen atmosphere for 4h. Cool to room temperature to obtain nickel-doped porous iron(III) oxide, denoted as Ni-Fe3O4.

[0143] 2-2) Loading ruthenium-doped carbon dots onto nickel-doped porous iron oxide:

[0144] 2-2-1) Take 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 and add them to a mixed solution consisting of 100 mL of ethanol and 50 mL of deionized water. Disperse the mixture by sonication for 5 min to obtain precursor solution 1.

[0145] 2-2-2) Take 1.5g of nickel-doped porous iron oxide and add it to 100mL of deionized water. Disperse it by ultrasonication for 15min to obtain precursor solution 2.

[0146] 2-2-3) Add precursor solution 1 to precursor solution 2 under stirring, stir at 1000 rpm for 30 min, transfer the resulting mixture to a polytetrafluoroethylene-lined reactor, react at 180 °C for 12 h, cool to room temperature after the reaction, filter, wash the solid product with deionized water, and vacuum dry at 90 °C for 12 h to obtain the demulsifier, denoted as Ni-Fe3O4@Ru-CDs.

[0147] Example 3

[0148] A comprehensive treatment process for oily scum based on ultrasonic scum dewatering includes the following steps:

[0149] 1) Alkalization of oily scum:

[0150] Add a 20% Na2CO3 aqueous solution to the oily scum containing aluminum salt flocculant, stir evenly, and adjust the pH value of the oily scum to 7.25 to obtain the alkalized oily scum.

[0151] 2) Ultrasonic demulsification:

[0152] The oily scum after alkalization was injected into a container, a demulsifier with a mass concentration of 0.7% was added, and the mixture was stirred at 1000 rpm for 10 min. Then it was heated to 60°C, and ultrasonic standing waves were applied at a frequency of 20 kHz and an ultrasonic power of 300 W for 6 min.

[0153] 3) Dewatering of oily scum:

[0154] After ultrasonic demulsification, the mixture is allowed to stand, settle and separate into layers. The lower aqueous phase is separated as scum wastewater, and the upper oil phase is separated as oily scum after dehydration.

[0155] 4) Post-treatment of scum wastewater:

[0156] The scum wastewater was introduced into an electrolytic cell, and 0.02 mol / L Na2SO4 was added. Then, H2O2 solution was added in portions, with the final H2O2 addition controlled at 0.8 mmol / L. An electro-Fenton reaction was carried out at 30℃ and a stirring speed of 80 r / min for 75 min, with the current density controlled at 8.5 mA / cm². 2 After the electro-Fenton reaction has been going on for 60 minutes, an ultrasonic standing wave is applied until the electro-Fenton reaction ends, and the demulsifier is magnetically recovered.

[0157] The ultrasonic frequency is 45kHz and the ultrasonic power is 350W.

[0158] 5) Post-treatment of oily scum after dehydration:

[0159] The dehydrated oily scum was distilled into a stirred reactor and stirred at 150 rpm while being heated. The aqueous phase and oil phase were separated by vacuum distillation and the product at the bottom of the reactor was the final residue.

[0160] 6) Aluminum salt recovery: Add 10 mg / L hydrochloric acid to the final residue after distillation for acidification treatment, neutralize the final residue to the alkalinity B value of 1.2, and obtain a regenerated aluminum salt solution.

[0161] The demulsifier is prepared by the following method:

[0162] 2-1) Preparation of nickel-doped porous iron(III) oxide:

[0163] Take 1g FeCl3·6H2O, 0.35g NiCl2·6H2O, 50mL ethanol, and 45mL cyclohexane and add them to 150mL ethylene glycol. Disperse the mixture by sonication for 30min. Then add 3.2g hexamethylenetetramine and stir for 10min. Transfer the resulting mixture to a polytetrafluoroethylene-lined reactor and react at 165℃ for 6h. After the reaction is complete, cool to room temperature, filter, wash the solid product with ethanol and deionized water in sequence, dry at 70℃ for 6h, and then calcine at 550℃ under a nitrogen atmosphere for 4h. Cool to room temperature to obtain nickel-doped porous iron(III) oxide, denoted as Ni-Fe3O4.

[0164] 2-2) Loading ruthenium-doped carbon dots onto nickel-doped porous iron oxide:

[0165] 2-2-1) Take 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 and add them to a mixed solution consisting of 100 mL of ethanol and 50 mL of deionized water. Disperse the mixture by sonication for 5 min to obtain precursor solution 1.

[0166] 2-2-2) Take 1.4g of nickel-doped porous iron oxide and add it to 100mL of deionized water. Disperse it by ultrasonication for 15min to obtain precursor solution 2.

[0167] 2-2-3) Add precursor solution 1 to precursor solution 2 under stirring, stir at 1000 rpm for 30 min, transfer the resulting mixture to a polytetrafluoroethylene-lined reactor, react at 180 °C for 12 h, cool to room temperature after the reaction, filter, wash the solid product with deionized water, and vacuum dry at 90 °C for 12 h to obtain the demulsifier, denoted as Ni-Fe3O4@Ru-CDs.

[0168] Comparative Example 1

[0169] The only difference between this example and Example 1 is that no demulsifier is added in step 2).

[0170] Comparative Example 2

[0171] The only difference between this example and Example 1 is that ultrasound is not applied during the electro-Fenton reaction in step 4).

[0172] Comparative Example 3

[0173] The only difference between this example and Example 1 is:

[0174] The demulsifier in this example was prepared by the following method:

[0175] 2-1) Preparation of porous iron(III) oxide:

[0176] Take 1g FeCl3·6H2O, 50mL ethanol, and 45mL cyclohexane and add them to 150mL ethylene glycol. Disperse by ultrasonication for 30min, then add 3.2g hexamethylenetetramine and stir for 10min. Transfer the resulting mixture to a reaction vessel lined with polytetrafluoroethylene and react at 165℃ for 6h. After the reaction is completed, cool to room temperature, filter, wash the solid product with ethanol and deionized water in sequence, dry at 70℃ for 6h, and then calcine at 550℃ under nitrogen atmosphere for 4h. Cool to room temperature to obtain porous iron(III) oxide.

[0177] 2-2) Loading ruthenium-doped carbon dots onto porous iron oxide:

[0178] 2-2-1) Take 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 and add them to a mixed solution consisting of 100 mL of ethanol and 50 mL of deionized water. Disperse the mixture by sonication for 5 min to obtain precursor solution 1.

[0179] 2-2-2) Take 1.2g of nickel-doped porous iron oxide and add it to 100mL of deionized water. Disperse it by ultrasonication for 15min to obtain precursor solution 2.

[0180] 2-2-3) Add precursor liquid 1 to precursor liquid 2 under stirring, stir at 1000 rpm for 30 min, transfer the resulting mixture to a polytetrafluoroethylene-lined reactor, react at 180 °C for 12 h, cool to room temperature after the reaction, filter, wash the solid product with deionized water, and vacuum dry at 90 °C for 12 h to obtain the demulsifier, denoted as Fe3O4@Ru-CDs.

[0181] Comparative Example 4

[0182] The only difference between this example and Example 1 is:

[0183] The demulsifier in this example was prepared by the following method:

[0184] 2-1) The preparation of nickel-doped porous iron oxide follows the same steps as in Example 1;

[0185] 2-2) Loading carbon dots onto nickel-doped porous iron oxide:

[0186] 2-2-1) Take 582 mg of aminoacridine yellow, 768 mg of citric acid, 240 mg of acetic acid, and 90 mg of ethylenediamine and add them to a mixed solution consisting of 100 mL of ethanol and 50 mL of deionized water. Disperse the mixture by sonication for 5 min to obtain precursor solution 1.

[0187] 2-2-2) Take 1.2g of nickel-doped porous iron oxide and add it to 100mL of deionized water. Disperse it by ultrasonication for 15min to obtain precursor solution 2.

[0188] 2-2-3) Add precursor liquid 1 to precursor liquid 2 under stirring, stir at 1000 rpm for 30 min, transfer the resulting mixture to a polytetrafluoroethylene-lined reactor, react at 180 °C for 12 h, cool to room temperature after the reaction, filter, wash the solid product with deionized water, and vacuum dry at 90 °C for 12 h to obtain the demulsifier, denoted as Ni-Fe3O4@CDs.

[0189] I. Processing Effect Test

[0190] Oily scum from the flotation section of Yangzhou Petrochemical Co., Ltd. was used as the test object. The processes described in the above examples and comparative examples were employed. The flocculant added in this flotation section was a mixture of PAM (polyacrylamide) and PAC (polyaluminum chloride), with PAM added at 2 mg / L and PAC added at 5 mg / L. The main characteristics of the oily scum were: water content 97%, oil content 5‰, average volumetric particle size 28.3 μm, and specific surface area 0.62 m². 2 ·g -1 .

[0191] The test items include:

[0192] 1. The water content ηw in the preliminary dehydrated oily scum obtained in step 3);

[0193] 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;

[0194] 3. Recovery rate γ of the oil phase product in step 5) O ;

[0195] 4. Recovery rate γ of aluminum salt in step 6) Al ;

[0196] The determination of water content shall be in accordance with GB / T 260—2016 "Determination of water content in petroleum products by distillation method".

[0197] Determination of oil content: After filtering the solution in the distillation flask through pre-weighed filter paper, it is collected in a 100 mL beaker. The distillation flask and the filtered filter paper are placed together in an oven and dried at 105 °C to constant weight. The weight is weighed and recorded. The difference in weight before and after drying is the weight of the solid phase. The oil content of the scum is obtained by the differential gravimetric method.

[0198] COD determination: The COD of wastewater was determined according to the standard "Water Quality - Determination of Chemical Oxygen Demand - Sealed Catalytic Digestion Method" (HZ-HJ-SZ-0108).

[0199] The test results are shown in Table 1 below. Figure 1-4 As shown:

[0200] Table 1

[0201]

[0202] The test results show that

[0203] As can be seen from the test results in Table 1, the processes in Examples 1-3 can achieve efficient demulsification, high COD removal rate, and high recovery rate of oil phase by-products and aluminum salts. In Comparative Example 1, no demulsifier was added, which seriously affected the dehydration rate in the front-end ultrasonic demulsification process and the COD removal rate in the subsequent water treatment process. In Comparative Example 2, no ultrasound was applied in the post-treatment of scum wastewater, which adversely affected the COD removal effect. The results of Comparative Examples 3 and 4 show that the doping of nickel in the iron(III) oxide of the demulsifier can improve the performance of the demulsifier, and the doping of ruthenium in the carbon dots has a significant enhancing effect on improving COD removal.

[0204] II. Parameter Optimization Experiment

[0205] 1. Following Example 1, the ultrasonic treatment time was changed, and the water content in the preliminarily dehydrated oily scum was tested.

[0206] Test results are as follows Figure 5As shown, within a certain range (0-6 min), the water content gradually decreases with increasing ultrasonic time. However, with further extension of ultrasonic radiation time, the water content of the scum gradually increases, resulting in a worse dewatering effect. This is because the scum contains a large number of solid particles and oil. The mechanical vibration of ultrasound changes the surface structure of the particles, reducing their adsorption capacity for oil and making them easier to peel off from the particle surface. Oil droplets collide and aggregate, forming larger droplets that are easier to separate from water. As the ultrasonic time increases, the total energy input to the system continuously increases, which breaks up the aggregated oil droplets, causing them to re-integrate into the water and promoting emulsification, leading to a worse dewatering effect (Wang Hongping. Study on the motion and aggregation characteristics of droplets under ultrasonic action [D]. Beijing: China University of Petroleum (Beijing), 2014). Both excessively short and excessively long ultrasonic times are detrimental to scum dewatering. The relatively optimal ultrasonic time was determined to be 6 min.

[0207] 2. Following Example 1, the ultrasonic power was varied, and the water content in the initially dehydrated oily scum was tested to study the effects of ultrasonic treatment time and ultrasonic power on demulsification and dehydration.

[0208] Test results are as follows Figure 6 As shown, it can be seen that with the increase of acoustic power, the water content of the treated scum first decreases and then increases, indicating that there is an optimal value for ultrasonic power during ultrasonic dehydration. This is because as acoustic power increases, the corresponding ultrasonic intensity also increases. When the ultrasonic intensity exceeds the cavitation threshold, cavitation occurs, forming a new emulsion on the sludge and increasing the difficulty of dehydrating the sludge.

[0209] 3. Following Example 1, the temperature of the ultrasonic demulsification process was changed, and the water content in the initially dehydrated oily scum was tested.

[0210] Test results are as follows Figure 7 As shown, the water content of the sediment first decreases and then increases with increasing ultrasonic treatment temperature; the dewatering rate of the scum reaches its lowest point at 60 ℃. This is mainly because: as the ultrasonic temperature increases, 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, improving the dewatering effect. At the same time, the increase in temperature leads to a decrease in the film stability and mechanical strength of the oil-water interface, making it easier for oil droplets to coalesce. The dewatering rate of the scum gradually decreases again at high temperatures. This is because at low temperatures, ultrasonic cavitation increases with increasing temperature, improving the dewatering effect; however, after exceeding the critical temperature point of the sample, the sound intensity and cavitation of the ultrasound gradually weaken, resulting in a worse dewatering effect.

[0211] III. Characterization of Demulsifier Performance

[0212] 1. Reference Figure 8The image shows the XRD pattern of the demulsifier prepared in Example 1, illustrating the successful preparation of the demulsifier.

[0213] 2. Reactive oxygen species generation performance test:

[0214] The demulsifiers prepared in Example 1, Comparative Example 2, and Comparative Example 3 were tested for their ability to generate reactive oxygen species according to the following method:

[0215] The demulsifier was added to deionized water and ultrasonically dispersed to prepare a dispersion with a concentration of 0.2 mg / mL. An ultrasonic standing wave was applied at a frequency of 45 kHz and an ultrasonic power of 350 W. The reactive oxygen species (ROS) fluorescent probe (ROS Brite 570, Ex (nm) 554Em (nm) 568, Xi'an Baiying Biotechnology Co., Ltd.) was used to determine the reactive oxygen species content at different treatment times. The higher the fluorescence intensity, the higher the reactive oxygen species content.

[0216] Test results are as follows Figure 9 As shown, the demulsifier in Example 1 can efficiently generate active oxygen under ultrasonic treatment. The reason for the decreased active oxygen generation efficiency in Comparative Example 1 is that the porous iron(III) oxide was not doped with nickel, which affected the stability and porosity of the porous structure of the demulsifier, thus affecting the loading of carbon dots and reducing the number of active sites. The decreased active oxygen generation efficiency in Comparative Example 2 indicates that ruthenium doping in the carbon dots can improve the ability of the demulsifier to generate active oxygen under ultrasonic treatment.

[0217] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A comprehensive treatment process for oily scum based on ultrasonic scum dewatering, characterized in that, Includes the following steps: 1) Alkalization of oily scum: Add alkali to the oily scum containing aluminum salt flocculants to adjust the pH; 2) Ultrasonic demulsification: Add demulsifier to the oily sludge after alkalization treatment, stir, and then apply ultrasound for treatment; 3) Dewatering of oily scum: After ultrasonic demulsification, the mixture is allowed to stand, settle and separate into layers. The lower aqueous phase is separated as scum wastewater, and the upper oil phase is separated as dewatered oily scum. 4) Post-treatment of scum wastewater: Combining ultrasonic and electro-Fenton methods to oxidize and 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 recycled aluminum salt solution; The demulsifier is prepared by the following method: 2-1) Preparation of nickel-doped porous iron(III) oxide: Take 0.5-2g FeCl3·6H2O, 0.15-0.7g NiCl2·6H2O, 25-100mL ethanol, and 20-90mL cyclohexane and add them to 100-300mL ethylene glycol. Disperse the mixture by sonication for 15-60min. Then add 1.6-6.4g hexamethylenetetramine and stir for 5-30min. Transfer the resulting mixture to a polytetrafluoroethylene-lined reactor and react at 150-175℃ for 4-8h. After the reaction is complete, cool to room temperature, filter, and wash the solid product with ethanol and deionized water in sequence. Dry at 60-90℃ for 3-10h, and then calcine at 450-600℃ under a nitrogen atmosphere for 2-6h. Cool to room temperature to obtain nickel-doped porous iron(III) oxide, denoted as Ni-Fe3O4. 2-2) Loading ruthenium-doped carbon dots onto nickel-doped porous iron oxide: 2-2-1) Take 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 and add them to a mixed solution consisting of 50-200 mL of ethanol and 25-100 mL of deionized water. Disperse the mixture by sonication for 3-20 min to obtain precursor solution 1. 2-2-2) Take 0.6-2.4g of nickel-doped porous iron(III) oxide and add it to 50-200mL of deionized water. Disperse it by ultrasonication for 10-30min to obtain precursor solution 2. 2-2-3) Add precursor liquid 1 to precursor liquid 2 under stirring, stir at 500-2500 rpm for 15-60 min, transfer the resulting mixture to a polytetrafluoroethylene-lined reactor, react at 170-210℃ for 6-24 h, cool to room temperature after the reaction, filter, wash the solid product with deionized water, and vacuum dry at 70-110℃ for 6-24 h to obtain the demulsifier, denoted as Ni-Fe3O4@Ru-CDs.

2. The comprehensive treatment process for oily scum based on ultrasonic scum dewatering according to claim 1, characterized in that, Step 1) Specifically: Add Na2CO3 to the oily scum containing aluminum salt flocculant and stir evenly. Adjust the pH value of the oily scum to 7-9 to obtain the alkalized oily scum.

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

4. The comprehensive treatment process for oily scum based on ultrasonic scum dewatering according to claim 1, characterized in that, Step 4) specifically involves: The scum wastewater is introduced into an electrolytic cell, and Na2SO4 with a concentration of 0.01-0.05 mol / L is added. Then, H2O2 solution is added in portions, controlling the final amount of H2O2 added to be 0.5-2.1 mmol / L. The electro-Fenton reaction is carried out at 28-32℃ and a stirring speed of 40-160 r / min for 50-90 min, with the current density controlled at 5-20 mA / cm². 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 ends, and the demulsifier is magnetically collected. The ultrasonic frequency is 25-60kHz and the ultrasonic power is 200-400W.

5. The comprehensive treatment process for oily scum based on ultrasonic scum dewatering according to claim 1, characterized in that, Step 5) specifically involves: The dehydrated oily scum is distilled into a stirred reactor and then distilled under reduced pressure with heating and stirring to separate the aqueous and oil phases. The product at the bottom of the reactor is the final residue.

6. The comprehensive treatment process for oily scum based on ultrasonic scum dewatering according to claim 1, characterized in that, Step 6) specifically involves: Add 5-20 mg / L of 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 the regenerated aluminum salt solution.

7. The comprehensive treatment process for oily scum based on ultrasonic scum dewatering according to any one of claims 1-6, characterized in that: 1) Alkalization of oily scum: Add a 20% Na2CO3 aqueous solution to the oily scum containing aluminum salt flocculant, stir evenly, and adjust the pH value of the oily scum to 7.25 to obtain the alkalized oily scum. 2) Ultrasonic demulsification: The oily scum after alkalization was injected into a container, a demulsifier with a mass concentration of 0.6% was added, and the mixture was stirred at 1000 rpm for 10 min. Then it was heated to 60°C, and an ultrasonic standing wave was applied with a frequency of 20 kHz and an ultrasonic power of 300 W for 6 min. 3) Dewatering of oily scum: After ultrasonic demulsification, the mixture is allowed to stand, settle and separate into layers. The lower aqueous 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 an electrolytic cell, and 0.02 mol / L Na2SO4 was added. Then, H2O2 solution was added in portions, with the final H2O2 addition controlled at 1.05 mmol / L. An electro-Fenton reaction was carried out at 30℃ and a stirring speed of 80 r / min for 75 min, with the current density controlled at 10.2 mA / cm². 2 After the electro-Fenton reaction has been going on for 60 minutes, an ultrasonic standing wave is applied until the electro-Fenton reaction ends, and the demulsifier is magnetically recovered. Among them, the ultrasonic frequency is 45kHz and the ultrasonic power is 350W; 5) Post-treatment of oily scum after dehydration: The dehydrated oily scum was distilled into a stirred reactor and stirred at 150 rpm while being heated. The aqueous phase and oil phase were separated by vacuum distillation and the product at the bottom of the reactor was the final residue. 6) Aluminum salt recovery: Add 10 mg / L hydrochloric acid to the final residue after distillation for acidification treatment, neutralize the final residue to the alkalinity B value of 1.2, and obtain a regenerated aluminum salt solution.

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