Glucose zinc oxide attapulgite composite photocatalytic adsorbent and preparation method thereof

Abstract

The invention discloses a glucose zinc oxide attapulgite composite photocatalytic adsorbent and a preparation method thereof. The composite photocatalytic adsorbent comprises attapulgite, glucose, zinc oxide, an isopropanol solution, cobalt nitrate, potassium hydrogen phthalate, potassium hydroxide and sodium hydroxide. The preparation method comprises the following steps: adding acid-washed attapulgite and glucose into deionized water to form a suspension; transferring the suspension into a hydrothermal reaction kettle for reaction to obtain a solid product; the preparation method comprises the following steps: preparing a glucose carbon-attapulgite composite material, drying by a drying oven to obtain the glucose carbon-attapulgite composite material, loading a zinc oxide precursor solution on the glucose carbon-attapulgite composite material by an impregnation method, and calcining to obtain a final product. The method provided by the invention can effectively remove aldehyde ketone oxidation products, corrosive sulfides and metal ion compounds which cause color change of the oil product, enables the dark waste oil to recover to a colorless and transparent state, and also can efficiently remove acidic substances, significantly reduce the acid value of the oil product and improve the chemical stability of the oil product.

Description

TECHNICAL FIELD

[0001] The application relates to a composite photocatalytic adsorbent, in particular a glucose-zinc oxide-attapulgite composite photocatalytic adsorbent and a preparation method thereof, and belongs to the technical field of research on regeneration of retired transformer oil. BACKGROUND

[0002] Transformers are widely used in power grid systems, and transformer oil is the key to the normal operation of transformers. However, the use of transformers will inevitably produce a large amount of retired transformer oil. Generally, the adsorption method is used to remove harmful components in waste oil, including water, aged additives, oxides and the like, through an adsorption process. The adsorption method can effectively improve the color of the retired transformer oil and restore the electrical properties of the waste oil. Compared with other regeneration methods, the adsorption method has unique characteristics such as high efficiency, easy operation and low cost, and stands out among many methods.

[0003] Attapulgite material belongs to natural clay material, and has good adsorption performance for organic macromolecules, metal ions and the like and various modification methods. Composite materials prepared from attapulgite and similar materials are used to adsorb heavy metals, organic matter and dyes. According to GB / T 7595-2017 “Quality of Running Transformer Oil”, there are corresponding requirements for the colority of transformer oil. The traditional adsorbent uses materials such as white clay, aluminum oxide and silica gel for adsorption and decolorization, and the effect is not good. The use of attapulgite material can effectively reduce the dielectric loss of transformer oil on the basis of better decolorization effect. However, the adsorption capacity of natural attapulgite for some specific impurities in transformer oil (such as antioxidant degradation products, corrosive sulfur, metal complexes and the like) is still insufficient, and the pores are easy to be blocked, and the regeneration performance is poor. In order to improve the adsorption performance, researchers often activate attapulgite by methods such as acid, heat and organic modification, or composite it with other functional materials to build a synergistic adsorption system. For example, carbon materials are compounded with attapulgite, which can utilize the high specific surface area and rich functional groups of carbon materials to enhance the adsorption of organic impurities; the introduction of metal oxides (such as zinc oxide) can provide photocatalytic activity to degrade the adsorbed organic matter under light, realizing the integration of adsorption and catalysis, and prolonging the service life of the adsorbent. Although many composite materials have been explored for oil treatment, there are still problems such as complex preparation process, low photocatalytic efficiency, weak adsorption selectivity and poor cycle stability.

[0004] In the prior art, a method for preparing attapulgite / zinc oxide nanocomposite material is disclosed in CN101444717A. The method prepares a nanometer attapulgite dispersion liquid by purifying and dispersing attapulgite in an aqueous phase, then adds a zinc salt and a carbonate solution to the dispersion liquid at 30-100 DEG C, maintains the pH value at 6.0-8.0, filters, washes, dries and calcines at 300-600 DEG C for 1-10 hours after the reaction, and finally obtains the attapulgite / zinc oxide nanocomposite material. The material prepared by the method has the characteristics of uniform loading, good dispersibility, strong adsorption capacity and photocatalytic degradation performance, and the method is simple, low in energy consumption and high in safety. However, the method still needs a high-temperature calcination step, the energy consumption is relatively high, and it is not specifically optimized for the adsorption of color-causing impurities and acidic substances in the regeneration of transformer oil, and the adsorption selectivity and recycling performance still have room for improvement. In addition, a glucose attapulgite / zinc oxide composite material is prepared in the research of "Application Research of Glucose Zinc Oxide Photocatalyst for Transformer Waste Oil Decolorization" in the June 2025 issue of "Contemporary Chemical Research", which is used for transformer waste oil decolorization. Under certain conditions (such as APT / GLU mass ratio 5:1, adsorption temperature 90 DEG C, adsorption time 1h, etc.), the decolorization rate of retired transformer oil can reach 87.3%, the acid value can be reduced to 0.0102 mgKOH / g, and after "acid washing-alcohol washing" regeneration, the 5-time cycle adsorption performance can still be maintained at more than 90%, but the research focuses on the application effect of the glucose / zinc oxide composite material, and there is still room for improvement in the pretreatment of attapulgite in the composite material, the loading mode of zinc oxide and the in-depth study of the synergistic mechanism of photocatalysis and adsorption. Moreover, the efficiency of the photocatalytic performance in the transformer oil matrix may be limited by the light transmittance of the oil. SUMMARY

[0005] The purpose of the present application is to provide a glucose zinc oxide attapulgite composite photocatalytic adsorbent and a preparation method thereof to solve at least one of the above technical problems. The acid-activated attapulgite is used as a carrier, and a new composite photocatalytic adsorbent of glucose-derived carbon and zinc oxide is loaded by a hydrothermal method to solve the technical problems of low adsorption capacity, insufficient catalytic activity and poor recycling performance of existing adsorbents in the regeneration process of transformer oil.

[0006] The present application realizes the above-mentioned purpose through the following technical scheme: a glucose zinc oxide attapulgite composite photocatalytic adsorbent, which comprises a composite photocatalytic adsorbent, and the preparation raw materials of the composite photocatalytic adsorbent comprise attapulgite, glucose, zinc oxide, isopropyl alcohol solution, cobalt nitrate, hydrogen potassium phthalate, potassium hydroxide and sodium hydroxide. The composite photocatalytic adsorbent takes the palygorskite after acid washing treatment as a carrier, and glucose as a carbon source is loaded on the surface and pores of the carrier by a hydrothermal synthesis method to form a composite material with a porous structure and photocatalytic activity; the composite photocatalytic adsorbent has a high specific surface area, and the composite photocatalytic adsorbent has the functions of adsorption and photocatalysis for removing color-causing impurities, acidic substances and metal ions in transformer oil.

[0007] As a further scheme of the application: the palygorskite is first subjected to acid washing treatment with a sulfuric acid solution to remove impurities and activate the surface thereof, then mixed with glucose at a mass ratio of 5:2, dissolved in deionized water, and subjected to hydrothermal reaction to form a carbon-based composite skeleton; zinc oxide is used as a cobalt nitrate precursor, precipitated under alkaline conditions, and loaded on the surface of the composite material to finally form a composite photocatalytic adsorbent with visible light response.

[0008] A preparation method of a glucose-zinc oxide-palygorskite composite photocatalytic adsorbent, the preparation method comprising the following steps: The palygorskite after acid washing and glucose are added to deionized water in a certain proportion, and stirred to form a uniform suspension; The suspension is transferred to a hydrothermal reaction kettle, and reacted at 160 DEG C for 12 hours; after the reaction is completed, the reaction kettle is cooled to room temperature, and the solid product is obtained by centrifugal separation; the solid product is washed with ethanol and deionized water alternately for multiple times to remove unreacted substances; Finally, the product is dried in an oven at 60 DEG C to obtain a glucose carbon-palygorskite composite material; then, a zinc oxide precursor solution is loaded on the glucose carbon-palygorskite composite material by an immersion method, and the final product is obtained after calcination treatment.

[0009] A method for treating decommissioned transformer oil by using a composite photocatalytic adsorbent, the method comprising the following steps: The composite photocatalytic adsorbent is mixed with the decommissioned transformer oil at a mass ratio in the range of 1:2 to 1:16, and placed in a constant-temperature stirring device for adsorption treatment; the reaction is carried out at a temperature in the range of 30 DEG C to 120 DEG C for 0.5 to 8 hours; and ultraviolet light irradiation can be combined during the reaction to enhance the photocatalytic degradation effect; After the reaction is completed, centrifugal separation is carried out, and the supernatant is filtered to obtain regenerated oil; The regenerated oil is subjected to adsorption index determination, and the adsorption index includes but is not limited to decolorization rate and acid value.

[0010] As a further scheme of the application: the preferred process for treating decommissioned transformer oil by using the composite photocatalytic adsorbent is as follows: the mass ratio of the composite photocatalytic adsorbent to the decommissioned transformer oil is 1:2, the adsorption temperature is 90 DEG C, and the adsorption time is 1 hour.

[0011] As a further scheme of the present application: the determination of the decolorization rate adopts ultraviolet spectrophotometry to determine the absorbance of the retired transformer oil and the regenerated oil; the absorbance of the oil product is determined at a wavelength of 480 nm with deionized water as a reference; and the calculation formula of the decolorization rate is: A=(E-X) / E100% In the formula, A (%) is the decolorization rate, E is the absorbance of the retired oil, and X is the absorbance of the regenerated oil. The determination of the acid value adopts colorimetric titration to determine the acid value of the transformer oil, wherein the determination standard of the colorimetric titration is the determination of the acid value of the insulating liquid in the national standard GB / T41633.2-2022.

[0012] As a further scheme of the present application: the adsorption treatment can be carried out in a photocatalytic reactor, the photocatalytic reactor is equipped with a 405 nm wavelength, 500 W power ultraviolet light source, and the reaction container is made of a light-transmitting material to ensure that light can effectively penetrate and activate the photocatalytic components on the surface of the adsorbent, promoting the degradation of organic impurities.

[0013] As a further scheme of the present application: the composite photocatalytic adsorbent is collected after use, 1 mol / L sulfuric acid solution and 50% ethanol solution are used as eluent, and the adsorbent is cleaned for 15 minutes under ultrasonic assistance to desorb the impurities adsorbed on the surface and in the pores; the adsorbent after cleaning is subjected to centrifugal separation and drying treatment, and can be repeatedly used for adsorption treatment of transformer oil, and can be recycled for at least 5 times while maintaining more than 90% of the initial adsorption performance.

[0014] As a further scheme of the present application: before the composite photocatalytic adsorbent is used for adsorption treatment of the retired transformer oil, the retired transformer oil is subjected to dehydration treatment with a hydrophobic membrane, and then the dehydrated retired transformer oil is subjected to preliminary dielectric loss reduction and decolorization treatment with XDZ-20 adsorption paper.

[0015] As a further scheme of the present application: the composite photocatalytic adsorbent has selective adsorption capacity for corrosive sulfur, metal ions and oxidation-generated color-causing impurities in the transformer oil, the composite photocatalytic adsorbent preferentially adsorbs polar impurities and aromatic compounds through the synergistic effect of the surface functional groups and the pore structure, and can further degrade the adsorbed organic matter under light conditions, realizing the adsorption and degradation synergistic purification mechanism.

[0016] The present application has the following advantages: 1) The present application adopts a glucose zinc oxide attapulgite composite photocatalytic adsorbent with stronger transformer oil decolorization effect. The composite material successfully combines the adsorption characteristics of attapulgite, the porous structure of glucose carbon source, and the photocatalytic activity of zinc oxide through a unique formula design and preparation process, forming a synergistic purification system, which exhibits excellent comprehensive performance when applied to the regeneration treatment of retired transformer oil; it not only shows extremely high adsorption capacity and selectivity to the coloring impurities in the oil, can effectively remove the aldehyde and ketone oxidation products, corrosive sulfides and metal ion complexes that cause oil discoloration, and restore dark waste oil to colorless and transparent state, but also can efficiently remove acidic substances, significantly reduce the acid value of the oil, and improve the chemical stability of the oil; 2) Under light irradiation conditions, the loaded zinc oxide component can be activated to produce strong oxidizing active species, which can deeply degrade the adsorbed organic impurities, avoiding the accumulation of impurities on the surface of the adsorbent. This adsorption-photocatalysis synergistic mechanism not only greatly improves the purification efficiency, but also significantly enhances the anti-pollution ability and regeneration cycle stability of the material, achieving excellent adsorption performance even after long-term repeated use. The electrical performance of the regenerated oil treated by the adsorbent is fully restored, the dielectric loss value is significantly reduced, and the breakdown voltage is significantly improved, fully meeting the strict standards of operating transformer oil. The whole treatment process has mild conditions, simple operation and low energy consumption, without the need for complex equipment. The adsorbent used is low in raw material cost and environmentally friendly, and the regeneration and elution process is simple and efficient, effectively reducing the comprehensive cost of transformer oil regeneration. It provides an efficient, economical and green sustainable technical solution for large-scale treatment of retired transformer oil, and has broad industrial application prospects and important environmental protection value. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 FESEM images of the APT and its three composite materials of the present application; Figure 2 XRD images of the APT and its composite materials of the present application; Figure 3 FT-IR images of the APT and its composite materials of the present application; Figure 4 Raman spectra of the APT and its composite materials of the present application; Figure 5 N2 adsorption-desorption isotherms of the APT and its composite materials of the present application; Figure 6 Decolorization rate and acid value of waste oil treated by different adsorbents of the present application; Figure 7 Effect of different adsorption temperatures on adsorption performance of the present application; Figure 8 Effect of adsorbent dosage on adsorption performance of the present application; Figure 9 A schematic diagram of the effect of different adsorption times on the adsorption performance of waste oil according to the present application; Figure 10 A schematic diagram of the GLU-APT continuous adsorption-desorption cycle experiment according to the present application; Figure 11 A photograph comparison diagram of waste oil before and after adsorption treatment according to the present application. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0019] In embodiment one, a glucose-zinc oxide-attapulgite composite photocatalytic adsorbent is provided, which comprises a composite photocatalytic adsorbent. The preparation raw materials of the composite photocatalytic adsorbent include attapulgite, glucose, zinc oxide, isopropyl alcohol solution, cobalt nitrate, potassium hydrogen phthalate, potassium hydroxide and sodium hydroxide. The composite photocatalytic adsorbent takes the attapulgite after acid pickling treatment as a carrier, and glucose as a carbon source is loaded on the surface and pores of the carrier by a hydrothermal synthesis method to form a composite material with a porous structure and photocatalytic activity. The composite photocatalytic adsorbent has a high specific surface area, and the composite photocatalytic adsorbent has adsorption and photocatalytic functions of removing color-causing impurities, acidic substances and metal ions in transformer oil.

[0020] The attapulgite is first subjected to acid pickling treatment with a sulfuric acid solution to remove impurities and activate the surface thereof, and then mixed with glucose at a mass ratio of 5:2, dissolved in deionized water, and subjected to hydrothermal reaction to form a carbon-based composite framework. The zinc oxide takes cobalt nitrate as a precursor, is precipitated under alkaline conditions, and is loaded on the surface of the composite material to finally form a composite photocatalytic adsorbent with visible light response.

[0021] In embodiment two, the preparation method of a glucose-zinc oxide-attapulgite composite photocatalytic adsorbent is based on the preparation method of embodiment one, and the preparation method comprises the following steps: The attapulgite after acid pickling and glucose are added to deionized water in proportion, and stirred to form a uniform suspension; The suspension is transferred to a hydrothermal reaction kettle, and reacted at 160℃ for 12 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the solid product is obtained by centrifugal separation. The solid product is washed with ethanol and deionized water alternately for multiple times to remove unreacted substances; Finally, after drying in a 60℃ oven overnight, a glucose-carbon-attapulgite composite material is obtained; then a zinc oxide precursor solution is loaded on the composite material by the impregnation method, and after calcination treatment, the final product is obtained.

[0022] In Example Three, the method of treating decommissioned transformer oil by the composite photocatalytic adsorbent of Example One includes the following steps: The composite photocatalytic adsorbent is mixed with the decommissioned transformer oil at a mass ratio in the range of 1:2 to 1:16, and placed in a constant temperature stirring device for adsorption treatment, and the reaction is carried out at a temperature in the range of 30℃ to 120℃ for 0.5 to 8 hours. Ultraviolet light irradiation can be combined during the reaction process to enhance the photocatalytic degradation effect. After the reaction is completed, centrifugal separation is carried out, and the supernatant is filtered to obtain the regenerated oil; The adsorption index of the regenerated oil obtained is determined, including but not limited to the decolorization rate and the acid value.

[0023] Further, the preferred process for treating decommissioned transformer oil with the composite photocatalytic adsorbent is as follows: the mass ratio of the composite photocatalytic adsorbent to the decommissioned transformer oil is 1:2, the adsorption temperature is 90℃, and the adsorption time is 1 hour.

[0024] Further, the decolorization rate is determined by measuring the absorbance of the decommissioned transformer oil and the regenerated oil using a UV spectrophotometer; deionized water is used as a reference, and the absorbance of the oil is measured at a wavelength of 480nm; the calculation formula for the decolorization rate is: A=(E-X) / E100% In the formula, A (%) is the decolorization rate, E is the absorbance of the decommissioned oil, and X is the absorbance of the regenerated oil. The acid value is determined by colorimetric titration method to determine the acid value of the transformer oil, wherein the determination standard of the colorimetric titration method is GB / T41633.2-2022 Insulating Liquids - Determination of Acid Number.

[0025] Further, the adsorption treatment can be carried out in a photocatalytic reactor equipped with a 405nm wavelength, 500W power ultraviolet light source, and the reaction container is made of light-transmitting material to ensure that light can effectively penetrate and activate the photocatalytic components on the surface of the adsorbent, promoting the degradation of organic impurities.

[0026] Further, after use, the composite photocatalytic adsorbent is collected, washed with 1mol / L sulfuric acid solution and 50% ethanol solution as eluent, and cleaned for 15 minutes under ultrasonic assistance to desorb the impurities adsorbed on the surface and in the pores of the adsorbent; after centrifugal separation and drying treatment, the cleaned adsorbent can be repeatedly used for adsorption treatment of transformer oil, and at least can be recycled for 5 times while maintaining more than 90% of the initial adsorption performance.

[0027] Furthermore, before the composite photocatalytic adsorbent is used to adsorb the decommissioned transformer oil, the decommissioned transformer oil is first dehydrated using a hydrophobic membrane, and then the dehydrated decommissioned transformer oil is preliminarily treated with XDZ-20 adsorption paper to reduce dielectric loss and decolorize it.

[0028] Furthermore, the composite photocatalytic adsorbent has selective adsorption capacity for corrosive sulfur, metal ions and color-causing impurities generated by oxidation in transformer oil. Through the synergistic effect of surface functional groups and pore structure, the composite photocatalytic adsorbent preferentially adsorbs polar impurities and aromatic compounds, and can further degrade the adsorbed organic matter under light conditions, thus realizing a synergistic purification mechanism of adsorption and degradation.

[0029] Example 4: A method for preparing a glucose-zinc oxide-attapulgite composite photocatalytic adsorbent, comprising a composite photocatalytic adsorbent, such as... Figure 1 As shown, APT exhibits a sheet-like structure with irregular edges. When glucose is used as a carbon source to form a composite material with APT, the surface of the sheet-like structure becomes smoother, the sheets become more compact, and it exhibits a more regular microstructure.

[0030] X-ray diffraction was used to identify the structure of APT and its three composite materials. Figure 2 As shown, the main diffraction peaks of the APT composite material are basically consistent with those of APT, and its main diffraction characteristic peaks correspond to substances commonly found in clay minerals. For example, the characteristic peaks at 21.7° and 35.7° correspond to diffraction peaks of silica, and the characteristic peak at 19.7° corresponds to diffraction peaks of magnesium aluminosilicate. Furthermore, the positions of the diffraction peaks of the APT composite material and APT did not change significantly, indicating that the introduction of different carbon sources did not significantly affect the original structure of APT.

[0031] The molecular structural characteristics of APT and APT composites were analyzed using FT-IR. For example... Figure 3The infrared peaks at 3625 and 3424 cm-1 correspond to the stretching vibration peaks of Al-OH and Mg-OH, respectively, and the infrared peak at 1641 cm-1 corresponds to the stretching vibration peak of zeolite water. Secondly, the four materials all have obvious infrared peaks at 1087 to 1041 cm-1, which correspond to the stretching vibration peaks of Si-O bonds, indicating that the APT composite material has Si-O bonds like APT. In addition, the infrared peak at 792 cm-1 corresponds to the stretching vibration peak of C-H, indicating that the introduction of carbon sources into the APT composite material does not change the main structure. The peak of APT material at about 1500 cm-1 is the stretching vibration of carbonate, and this peak disappears during the material compounding process, which means that the carbonate in the channel of the APT material in the three composite materials prepared disappears, which corresponds to the BET test results. The peak of the four materials at 518 cm-1 is the stretching vibration of Si-O-Si bond, indicating that the material compounding process does not change the structure of APT.

[0032] The carbon structure of the APT composite material was further studied by Raman spectroscopy, and the structural characteristics of different carbon sources in the composite material were compared. As shown in Figure 4 The D band and G band of GLU-APT were observed at 1381 and 1570 cm-1, respectively, and the D band corresponds to the disordered carbon in the composite material, and the G band corresponds to the graphite carbon in the composite material. While APT does not contain carbon materials and cannot exhibit characteristic bands, which also proves the successful synthesis of GLU-APT. According to literature reports, the peak area ratio (ID / IG) of D band and G band can represent the disorder degree of carbon in the composite material, and the larger the ID / IG, the greater the disorder degree of carbon in the composite material. Through fitting comparison, it is found that the disorder degree of carbon in GLU-APT (ID / IG = 1.41) is greater than that in PDA-APT (ID / IG = 1.39) and AL-APT (ID / IG = 1.03). This indicates that the difference in carbon sources and the way of adding carbon sources in the preparation process of the composite material will change the ratio of disordered carbon and graphite carbon in the composite material. At the same time, due to the higher proportion of disordered carbon in GLU-APT, its adsorption performance will be more excellent.

[0033] The specific surface area and pore size distribution of the material were obtained by testing the N2 adsorption-desorption isotherm of different composite materials. As shown in Figure 5 By comparing the four materials, it is not difficult to find that the introduction of glucose significantly improves the specific surface area and pore size of the composite material. This is mainly due to the attachment of amorphous carbon on the surface of APT material. Among the four materials, the BET specific surface area of GLU-APT material is 71.006 m2 / g, which is significantly higher than that of the other three materials. At the same time, the pore size of GLU-APT material is also the largest, which is 13.66 nm.

[0034] The absorbance of waste oil and regenerated oil at a wavelength of 480 nm was measured by ultraviolet spectrophotometer, and the decolorization effect of APT and its composite adsorbent on the retired transformer oil was calculated. Secondly, common adsorbents such as activated clay and activated carbon were also selected for comparative analysis. As shown in Figure 6 The decolorization rate of GLU-APT on the retired transformer oil reached 87.0%, which was significantly improved compared with the decolorization rate of 5.8% of APT, showing excellent adsorption and impurity removal effect. The decolorization rates of regenerated oil treated by AL-APT, PDA-APT, activated clay or activated carbon were 51.8%, 11.0%, 8.2% or 16.5%, respectively, which were significantly lower than that of GLU-APT, indicating that the adsorption and decolorization effect was closely related to the structure characteristics and intrinsic activity of different APT composite materials, and also depended on the adsorption relationship between the adsorbent and the color-causing substance. The specific adsorption process could be divided into the diffusion of color-causing substance on the material surface, the interaction between color-causing substance and adsorbent, and the attachment on the surface or inside of the adsorbent. On the other hand, the initial acid value of the retired transformer oil was 0.0559 mgKOH / g, and the acid value of the regenerated oil treated by APT was 0.0499 mgKOH / g, with a small decrease in acid value. When treated by PDA-APT, AL-APT, activated clay or activated carbon, the acid value of the regenerated oil was 0.0492, 0.0267, 0.0493 or 0.0451 mgKOH / g, respectively. After treatment by GLU-APT, the acid value of the regenerated oil could be reduced to 0.010 mgKOH / g, with a reduction degree of 82.1%, showing excellent acid value reduction ability, and the acid value of the regenerated oil basically met the acid value requirement of 0.01 mgKOH / g in national standard GB2536-2011. Therefore, GLU-APT was used as a composite adsorbent, and the effect of different adsorption operation conditions on the decolorization and acid value reduction of retired transformer oil was further studied to optimize the process conditions.

[0035] Further, the optimization of adsorption operation conditions: The adsorption temperature was optimized by selecting different adsorption temperatures (30℃, 60℃, 90℃, 120℃) as factors, and the adsorption process was studied under the conditions of GLU-APT composite adsorbent and waste oil mass ratio of 1:8 and adsorption time of 4h. Each adsorption temperature condition was carried out for 3 times, and the experimental results were averaged.

[0036] From Figure 7It can be seen that with the adsorption temperature rising from 30℃ to 90℃, the adsorption effect is getting better and better. When the adsorption temperature reaches 90℃, the decolorization rate of the regenerated oil rises to 82.7%, and the acid value drops to 0.0125mgKOH / g, indicating that increasing the temperature is beneficial to improving the activity of the adsorbent and enhancing the removal capacity of the color-causing impurities. When the adsorption temperature continues to rise to 120℃, the decolorization rate of the regenerated oil decreases slightly, and the acid value also increases slightly. The main reason may be that when the temperature reaches 120℃, high temperature accelerates the aging of the retired transformer oil, which increases the content of color-causing impurities in the waste oil, resulting in a decrease in the decolorization rate and an increase in the acid value of the oil. In order to explore the significance of the influence of adsorption temperature on the regeneration effect of retired transformer oil, one-way ANOVA F test was performed on the decolorization rate and acid value data, respectively. The analysis results show that the P-value of the two sets of experimental results is much less than 0.01, indicating that the adsorption temperature has a very significant effect on the decolorization and acid value reduction of the retired transformer oil.

[0037] The optimization of the adsorbent dosage was carried out by selecting different mass ratios of adsorbent to waste oil as the research factor to explore the influence of adsorbent dosage on the adsorption performance. Specifically, under the conditions of adsorption temperature of 90℃ and adsorption time of 4h, adsorption experiments were carried out with the mass ratio of adsorbent to waste oil being 1:2, 1:4, 1:8 and 1:16, respectively. Each adsorbent dosage condition was tested for 3 times, and the results are shown in Table 2. Figure 8 As the adsorbent dosage decreases, the adsorption performance of the material gradually decreases. For example, when the mass ratio of adsorbent to waste oil is 1:2, the decolorization rate of the regenerated oil is 87.1%, and the acid value is 0.0103mgKOH / g. However, when the mass ratio of adsorbent to waste oil decreases to 1:16, the decolorization rate of the regenerated oil decreases to 56.1%, and the acid value increases to 0.0263mgKOH / g. The main reason is that the increase of the adsorbent dosage in the waste oil can significantly improve the contact frequency of organic matter, metal ions and other impurities with the adsorbent, strengthen the mass transfer efficiency between the liquid-solid interface, and enhance the adsorption and impurity removal effect of GLU-APT composite material on the transformer waste oil. The P-value of the decolorization rate and acid value data is also less than 0.01 when one-way ANOVA is performed, indicating that the adsorbent dosage has a very significant effect on the adsorption and impurity removal effect of the retired transformer oil.

[0038] The optimization of the adsorption time was carried out to study the influence of different adsorption times on the adsorption effect. Under the conditions of adsorption temperature of 90℃ and adsorbent to waste oil mass ratio of 1:2, the decolorization rate and acid value of the oil were measured after adsorption for 0.5, 1, 4, 6 and 8h, respectively. Each adsorption time condition was tested for 3 times, and the results are shown in Table 3. Figure 9As shown in Fig. 6, the adsorption effect of the composite adsorbent is the best when the adsorption time is 1 h, the decolorization rate is 88.2%, and the acid value is reduced to 0.010 mgKOH / g. With the increase of time, the decolorization rate slowly decreases, and the acid value slowly increases. It is shown that the adsorption performance cannot be improved after the adsorption time is prolonged, which may be because the transformer oil will be further deteriorated at a high temperature of 90°C, and new oxidation impurities are generated, so that the adsorption effect is poor. Therefore, the adsorption time is controlled at 1 h, so that the adsorption process can achieve the best adsorption effect. After the single-factor variance analysis of the decolorization rate and acid value data by using the F test method, the P-value values are both less than 0.01, which indicates that the adsorption time also has a very significant influence on the adsorption and impurity removal effect.

[0039] The optimization of the adsorption-desorption cycle experiment is carried out by using 1 mol / L sulfuric acid solution and 50% volume fraction of ethanol solution as the eluent, and the elution is carried out for 15 min under ultrasonic assistance. After centrifugal separation, the desorbed material is obtained. Subsequently, under the conditions of adsorption temperature 90°C, adsorption time 1 h, and adsorption solid-oil ratio 1:2, the transformer waste oil is subjected to continuous 5 times of adsorption-desorption cycle experiment, as shown in Fig. 7. Figure 10 As shown in Fig. 7, the decolorization rate of the regenerated oil after the first adsorption treatment is 86.6%, and the acid value is 0.0105 mgKOH / g. When the adsorbent after the first elution is used again to treat the waste oil, the decolorization rate of the regenerated oil is 93.1%, and the acid value is 0.0074 mgKOH / g, and the improvement of the adsorption performance index is mainly because the impurities in the pore structure of the composite material are deeply eluted after acid washing, so that more adsorption sites are exposed, and the adsorption performance is improved. With the increase of the cycle number, the adsorption performance gradually decreases. After 5 times of continuous cycle, the decolorization rate of the adsorbent to the regenerated oil is reduced to 77.3%, and the acid value reaches 0.0153 mgKOH / g. Although the adsorption performance is still maintained at about 90% of the initial decolorization rate, it is shown that the adsorption stability of GLU-APT is good, and the reusability is good.

[0040] Because the antioxidant 2,6-di-tert-butyl phenol is often added to the transformer oil, it is easy to become yellow under high temperature conditions. Secondly, the waste oil also contains a lot of corrosive sulfur and metal ions, and the existence of these impurities can also make the oil become yellow or even dark brown. Figure 11As shown, when the GLU-APT composite material is used to adsorb and treat waste oil under optimal conditions, due to the porous structure of both glucose carbon and APT, the colored impurities in the waste oil can be removed through the physical adsorption process under the action of van der Waals force, making the oil color change from dark yellow to colorless and transparent state without precipitate and suspended matter, which meets the quality indicators of transformer oil. As shown in Table 1, the decolorization rate of the regenerated oil reaches 87.3%, the acid value is reduced by 82.1%, the dielectric loss value is reduced by 97.8%, and the breakdown voltage is increased by 40.6%, so the composite adsorbent material can realize the regeneration of transformer waste oil, and the physicochemical properties and electrical performance are improved, as shown in Table 1.

[0041]

[0042] As can be seen from the above, three kinds of APT composite adsorbent materials with different carbon sources are prepared by taking APT as the substrate for the regeneration and refining of retired transformer oil. Through structural characterization and adsorption performance determination, it is found that the adsorption performance of GLU-APT is the best among the three composite materials, which is mainly due to its more regular surface morphology, larger specific surface area and more active sites. On this basis, GLU-APT is used as the research object, and through optimization of the adsorption process conditions, it is determined that when the adsorption temperature is 90℃, the adsorption time is 1h, and the adsorbent dosage is half of the mass of the waste oil, the best regeneration effect can be obtained, the decolorization rate of the regenerated oil can reach 88.2%, the acid value is reduced to 0.010mg / gKOH, and after 5 times of adsorption-desorption cycles, it can still maintain 90% of the adsorption performance. At the same time, the dielectric loss value of the regenerated oil is reduced to 0.025%, the breakdown voltage is increased to 41.2kV, and the electrical performance is improved. Therefore, this study provides a potential regeneration method for reducing the discharge of transformer waste oil and realizing the recycling of waste oil. In the future, suitable functional groups can be introduced into the adsorbent to improve its chemical adsorption capacity, or new composite adsorbent materials suitable for low-temperature adsorption can be designed and developed to avoid the problem of high adsorption temperature, further promoting the development of adsorption technology in the field of transformer waste oil regeneration.

[0043] The antioxidant di-tert-butyl phenyl is often added to transformer oil, which can easily become yellow at high temperatures. Secondly, waste oil also contains more corrosive sulfur and metal ions, which can also make the oil become yellow or even dark brown. When the waste oil is treated by the glucose zinc oxide attapulgite composite photocatalytic adsorbent under the best conditions, the color of the oil can be changed from dark yellow to colorless and transparent state, and there is no precipitate and suspended matter, which meets the quality indicators of transformer oil. The decolorization of the regenerated oil, the acid value and the dielectric loss value are reduced, and the breakdown voltage is increased. The composite adsorbent can regenerate the waste transformer oil, and improve its physical and chemical properties and electrical performance.

[0044] With the decrease of the adsorbent dosage, the adsorption performance of the material gradually decreases. For example, when the mass ratio of adsorbent to waste oil is 1:2, the decolorization rate of the regenerated oil is 87.1%, and the acid value is 0.0103 mgKOH / g. However, when the mass ratio of adsorbent to waste oil is reduced to 1:16, the decolorization rate of the regenerated oil is reduced to 56.1%, and the acid value is increased to 0.0263 mgKOH / g. The main reason is that the increase of the adsorbent dosage in waste oil can significantly improve the contact frequency of organic matter, metal ions and other impurities with the adsorbent, strengthen the mass transfer efficiency between the liquid-solid interface, and enhance the adsorption and impurity removal effect of GLU-APT composite material on waste transformer oil. When the decolorization rate and acid value data are subjected to single factor variance analysis, the P-value is less than 0.01, indicating that the adsorbent dosage has a very significant effect on the adsorption and impurity removal effect of the retired transformer oil.

[0045] With the increase of the adsorption temperature from 30℃ to 90℃, the adsorption effect is better and better. When the adsorption temperature reaches 90℃, the decolorization rate of the regenerated oil is increased to 82.7%, and the acid value is reduced to 0.0125 mgKOH / g, indicating that increasing the temperature is beneficial to improving the activity of the adsorbent and the removal capacity of the color-causing impurities. When the adsorption temperature continues to rise to 120℃, the decolorization rate of the regenerated oil is slightly reduced, and the acid value is slightly increased. The main reason may be that when the temperature reaches 120℃, the high temperature accelerates the aging of the retired transformer oil, which increases the content of color-causing impurities in the waste oil, resulting in the decrease of the decolorization rate and the increase of the acid value of the oil. In order to explore the significant influence of the adsorption temperature on the regeneration effect of the retired transformer oil.

[0046] With the increase of time, the decolorization rate slowly decreased, and the acid value slowly increased. It showed that the adsorption time was extended, and the adsorption performance could not be improved. It may be because the transformer oil will further deteriorate at high temperature of 90°C, and new oxidation impurities will be generated, which will make the adsorption effect worse. Therefore, the adsorption time is controlled within 1 h, which can make the adsorption process reach the best effect. When the F test method is used for single factor variance analysis of the decolorization rate and acid value data, the P-value is less than 0.01, which shows that the adsorption time also has a very significant effect on the adsorption and impurity removal effect.

[0047] The improvement of the adsorption performance index is mainly because the impurities in the pore structure of the composite material are deeply eluted after acid washing, and more adsorption sites are exposed, which improves the adsorption performance. With the increase of the cycle number, the adsorption performance gradually decreases. After 5 times of continuous circulation, the decolorization rate of the adsorbent for the regenerated oil is reduced to 77.3%, and the acid value is 0.0153 mgKOH / g. Although the adsorption performance still maintains about 90% of the initial decolorization rate, it shows that the adsorption stability of GLU-APT is good, and it has good reusability.

[0048] By light irradiation and under the action of photocatalyst, a large number of active oxidants can be generated by photon energy to promote the degradation of organic impurities and achieve the purpose of decolorization of transformer waste oil. This method not only solves the problem of organic impurity treatment completely, but also does not introduce new separation medium, does not cause secondary pollution, and does not cause problems such as adsorbent regeneration and recovery, which can greatly reduce the cost of practical application and obtain good economic benefits. The invention of photocatalytic reaction tester can further strengthen the decolorization effect of transformer oil.

[0049] In example four, a glucose zinc oxide attapulgite composite photocatalytic adsorbent is used in the "glucose-zinc oxide catalytic light irradiation adsorption treatment oil" method, which is applied to the customer of Xiaogan Light Source Electric Power Test Branch- Yunmeng waste transformer high-fault area oil decolorization. From April to July 2024, 80 kg of Yunmeng retired transformer oil was used for adsorption treatment.

[0050] Firstly, the water is removed by hydrophobic membrane, then 20 pieces of XDZ-20 adsorption paper are used to preliminarily reduce dielectric loss and decolorize, and finally light irradiation adsorption is used for further refining. In terms of photocatalytic adsorption, 2.5 kg of dried glucose attapulgite / zinc oxide composite material is weighed in a 100 L special transparent tube, then 80 kg of transformer waste oil is added, and the oil is irradiated for 24 h under the conditions of stirring and three ultraviolet lights (Shenzhen Ruishangl 405 nm 500 W) at an oil temperature of 40°C. The transformer regenerated oil is obtained by vacuum separation, and the decolorization rate and acid value of the oil are tested. The decolorization rate of the transformer regenerated oil in this example is 80%, and the acid value is 0.0168 mgKOH / g, as shown in Table 2.

[0051]

[0052] In summary, the illumination adsorption can meet the requirements of GB7595-2017, and the decolorization effect is less than 2. The provincial waste mineral oil recovery management center of our company will popularize this technology. The State Grid Company has about 100,000 tons of retired transformer oil per year, and needs 1 billion yuan for new purchase. Otherwise, if it is sold, it will produce CO2 231.2 million tons by burning, which is equivalent to planting 3.12 million trees to compensate. Therefore, our company also plans to popularize it to the State Grid system to achieve greater economic and environmental benefits.

[0053] Working process: the acid-washed activated attapulgite is used as a carrier skeleton, which has good adsorption performance and rich pore structure to provide a basis for loading other functional components; the glucose is carbonized and uniformly loaded on the surface and pores of the attapulgite by a hydrothermal method to form a carbon layer, which not only increases the specific surface area and adsorption sites of the material, but also effectively captures the organic pigment macromolecules and polar substances in the oil through physical adsorption and chemical forces; the further loaded zinc oxide nanoparticles can be excited to produce photo-generated electrons and holes under visible light or ultraviolet light irradiation, which can strongly oxidize and degrade the organic impurities adsorbed on the surface of the material to small molecules or harmless substances, thereby realizing the synergistic purification process of adsorption and photocatalytic degradation; the photocatalytic effect not only directly degrades the pollutants, but also regenerates the adsorption sites to some extent, prolongs the service life of the adsorbent, and deeply removes the corrosive sulfide metal ions and acidic compounds generated by oxidation in the transformer oil through the selective adsorption of the surface rich functional groups and the controllable pore structure and the photocatalytic degradation effect; the whole purification process realizes efficient removal of pollutants through the synergistic effect of adsorption concentration and photocatalytic degradation, and avoids secondary pollution, so that the color, acid value and electrical performance of the oil are significantly restored.

[0054] It is apparent to those skilled in the art that the application is not limited to the details of the foregoing exemplary embodiments, and that the application can be implemented in other particular forms without departing from the spirit or essential characteristics of the application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, and the scope of the application should be defined by the appended claims rather than by the foregoing description, and it is intended to include all changes that come within the meaning and range of equivalents of the claims. Any reference signs in the claims should not be considered as limiting the claims involved.

[0055] Furthermore, it should be understood that although the specification is described in terms of embodiments, not every embodiment includes every feature described. The specification can include implicit combinations of explicitly mentioned features and / or explicit combinations of implicitely mentioned features. Each embodiment depends on the explicit combinations of features and / or the implicit combinations of features made specifically within that embodiment, and each such embodiment can be combined with every other such embodiment to create further embodiments.

Claims

1. A glucose zinc oxide attapulgite composite photocatalytic adsorbent comprising a composite photocatalytic adsorbent, characterized in that: The preparation raw materials of the composite photocatalytic adsorbent include: attapulgite, glucose, zinc oxide, isopropyl alcohol solution, cobalt nitrate, potassium hydrogen phthalate, potassium hydroxide and sodium hydroxide; The composite photocatalytic adsorbent takes the attapulgite after acid washing treatment as the carrier, and glucose and zinc oxide as the carbon source are loaded on the surface and pores of the attapulgite by a hydrothermal synthesis method to form a composite material with a porous structure and photocatalytic activity.

2. The glucose zinc oxide attapulgite composite photocatalytic adsorbent according to claim 1, characterized in that: The attapulgite is first subjected to acid washing treatment with a sulfuric acid solution to remove impurities and activate the surface, and then mixed with glucose at a mass ratio of 5:2, dissolved in deionized water, and subjected to hydrothermal reaction to form a carbon-based composite framework; zinc oxide takes cobalt nitrate as a precursor, is precipitated under alkaline conditions, and is loaded on the surface of the composite material, finally forming a composite photocatalytic adsorbent with visible light response.

3. A method for preparing a glucose zinc oxide attapulgite composite photocatalytic adsorbent, comprising any of the composite photocatalytic adsorbents according to claims 1-2, characterized in that, The preparation method comprises the following steps: The attapulgite after acid washing and glucose are added to deionized water in a certain proportion, and stirred to form a uniform suspension; The suspension is transferred to a hydrothermal reaction kettle for reaction, and after the reaction is completed, the solid product is obtained by centrifugal separation, and washed with ethanol and deionized water alternately for multiple times to remove unreacted substances; The product is dried in an oven to obtain a glucose carbon-attapulgite composite material, and then a zinc oxide precursor solution is loaded on the glucose carbon-attapulgite composite material by an immersion method, and the final product is obtained after calcination.

4. A method of treating decommissioned transformer oil using the composite photocatalytic adsorbent of any one of claims 1-2, characterized in that, The method comprises: The composite photocatalytic adsorbent is mixed with the retired transformer oil at a mass ratio in the range of 1:2 to 1:16, and placed in a constant temperature stirring device for adsorption treatment, and the reaction is carried out at a temperature in the range of 30-120℃ for 0.5-8 hours, and ultraviolet light irradiation can be combined during the reaction to enhance the photocatalytic degradation effect; After the reaction is completed, centrifugal separation is carried out, and the supernatant is filtered to obtain regenerated oil; The adsorption index of the regenerated oil is determined, including but not limited to decolorization rate and acid value.

5. The method of claim 4, wherein: The preferred process for treating retired transformer oil with the composite photocatalytic adsorbent is: the mass ratio of the composite photocatalytic adsorbent to the retired transformer oil is 1:2, the adsorption temperature is 90℃, and the adsorption time is 1 hour.

6. The method of claim 4, wherein: The decolorization rate is determined by measuring the absorbance of the retired transformer oil and the regenerated oil with a UV spectrophotometer; deionized water is used as a reference, and the absorbance of the oil is measured at a wavelength of 480nm; the calculation formula of the decolorization rate is: A=(E-X) / E100%; In the formula, A(%) is the decolorization rate, E is the absorbance of the retired oil, and X is the absorbance of the regenerated oil; The acid value is determined by colorimetric titration method to determine the acid value of the transformer oil, wherein the determination standard of the colorimetric titration method is GB / T41633.2-2022 Insulating Liquids-Determination of Acid Number.

7. The method of claim 4, wherein: The adsorption treatment can be carried out in a photocatalytic reactor equipped with a 405nm wavelength, 500W power ultraviolet light source, and the reaction container is made of light-transmitting material.

8. The method of claim 4, wherein: The composite photocatalytic adsorbent is collected after use, cleaned for 15 minutes under ultrasonic assistance with 1 mol / L sulfuric acid solution and 50% ethanol solution as eluent to desorb the impurities adsorbed on the surface and in the pores of the adsorbent; the cleaned adsorbent is centrifuged and dried, and can be repeatedly used for adsorption treatment of transformer oil.

9. The method of claim 4, wherein: Before the composite photocatalytic adsorbent is used for adsorption treatment of the retired transformer oil, the retired transformer oil is dehydrated by using a hydrophobic membrane, and the dehydrated retired transformer oil is preliminarily reduced in dielectric loss and decolorized by using XDZ-20 adsorption paper.

10. The method of claim 4, wherein: The composite photocatalytic adsorbent has selective adsorption capacity for corrosive sulfur, metal ions and oxidized color-causing impurities in the transformer oil; the composite photocatalytic adsorbent preferentially adsorbs polar impurities and aromatic compounds through the synergistic effect of surface functional groups and pore structures, and can further degrade the adsorbed organic matters under light conditions, so that the adsorption and degradation synergistic purification mechanism is realized.

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