A method of synchronously adsorbing transformer oil and heavy metals in an accident oil pool

Abstract

The present application belongs to the technical field of wastewater treatment, and relates to treatment of oil-containing wastewater in a transformer accident oil pool in a transformer substation, in particular to a method for simultaneously adsorbing transformer oil and heavy metals in a transformer accident oil pool. A magnesium-aluminum hydrotalcite calcination oxide is added to oil-containing wastewater in the accident oil pool as an adsorbent for treatment; the magnesium-aluminum hydrotalcite calcination oxide is prepared by single titration of a mixed solution of magnesium salt and aluminum salt with an alkali solution containing alkali metal hydroxide and alkali metal carbonate to form magnesium-aluminum hydrotalcite-like, and then the magnesium-aluminum hydrotalcite-like is calcined to obtain the magnesium-aluminum hydrotalcite calcination oxide. The method provided by the present application can not only greatly reduce the COD of oil-containing wastewater in the transformer accident oil pool, but also effectively adsorb various heavy metal ions such as iron, chromium, arsenic and selenium at the same time, so as to realize treatment of the oil-containing wastewater in the transformer accident oil pool.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wastewater treatment, and relates to treatment of oil-containing wastewater in a transformer accident oil pool in a transformer substation, in particular to a method for simultaneously adsorbing transformer oil and heavy metals in a transformer accident oil pool. BACKGROUND

[0002] The information disclosed in this Background section is only for the purpose of increasing an understanding of the general background of the application and does not necessarily constitute an admission by the patent applicant or the patent owner that this information forms prior art.

[0003] Currently, oil-immersed transformers used in transformer substation systems use transformer oil as the insulation medium of the equipment. When the transformer has an oil spewing accident, a large amount of transformer oil will be spewed out of the oil tank. In addition, transformer component failure or aging of the sealing element will also cause a small amount of transformer oil to leak. The oil-containing wastewater in the transformer accident oil pool is mainly composed of transformer waste oil and stored rainwater, and the oil accumulation increases with the lengthening of the operation time. The oil-containing wastewater in the transformer accident oil pool has a high oil content compared to other industrial wastewater, and the test shows that the chemical oxygen demand (COD) is high, and it also contains various heavy metal ions such as iron, chromium, arsenic, and selenium. If the oil-containing wastewater is not strictly treated before being discharged into the environment outside the station, it will cause serious environmental pollution to the soil and water bodies.

[0004] The inventors have found that the existing adsorbent materials are difficult to simultaneously effectively adsorb the transformer oil and the iron, chromium, arsenic, and selenium in the oil-containing wastewater, thereby making it extremely difficult to treat the transformer oil and the heavy metals in the transformer accident oil pool. SUMMARY

[0005] In order to solve the problems of the prior art, the purpose of the present application is to provide a method for simultaneously adsorbing transformer oil and heavy metals in a transformer accident oil pool. The method provided by the present application can not only greatly reduce the COD of the oil-containing wastewater in the transformer accident oil pool, but also effectively adsorb various heavy metal ions such as iron, chromium, arsenic, and selenium at the same time, thereby achieving treatment of the oil-containing wastewater in the transformer accident oil pool.

[0006] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0007] On the one hand, an application of an adsorbent in simultaneously adsorbing transformer oil and heavy metals in a transformer accident oil pool, the heavy metals including iron, chromium, arsenic, and selenium, and the heavy metals being ions, the adsorbent being magnesium-aluminum hydrotalcite calcined oxides (MgAl-LDOs);

[0008] The preparation method of the magnesium-aluminum hydrotalcite calcined oxides is as follows: MgAl-LDHs (magnesium-aluminum hydrotalcite-like) is prepared by single titration of a mixed solution of magnesium salt and aluminum salt with an alkali solution containing alkali metal hydroxide and alkali metal carbonate, and then the MgAl-LDHs is calcined to obtain the magnesium-aluminum hydrotalcite calcined oxides.

[0009] The hydrotalcite-like compound is an anionic layered nanomaterial, has good structural stability, ion exchange, memory effect and acid-base double function, and can be used as an adsorbent and a catalytic material for environmental governance.

[0010] The MgAl-LDHs is further calcined to obtain MgAl-LDOs; compared with the MgAl-LDHs, the MgAl-LDOs has a larger specific surface area and a more stable structure, and is beneficial to improve the adsorption efficiency.

[0011] The preparation method of the MgAl-LDHs includes a coprecipitation method, an ion exchange method, a calcination and restoration method, a hydrothermal synthesis method, an induced hydrolysis method and a nucleation-crystallization method; the coprecipitation method can prepare the MgAl-LDHs with high purity and high crystallinity, and the MgAl-LDOs prepared by the method can further improve the specific surface area and the structural stability; therefore, the coprecipitation method is adopted in the present application. The coprecipitation method is divided into a single titration method and a double titration method according to operation steps; in the single titration method, the mixed metal salt solution is added drop by drop into the alkaline solution under continuous stirring, and the pH value of the solution is adjusted during the titration process to keep it within the range of metal ion precipitation; in the double titration method, the mixed salt solution and the alkaline solution are simultaneously added into an aqueous solution with a certain pH value, and then crystallization, washing and drying are performed to obtain the hydrotalcite. However, the present application finds that in the double titration method, nucleation and crystallization are simultaneously performed, so that the particle size distribution of the product is wide, and the MgAl-LDOs formed after calcination has poor adsorption capacity for iron, chromium, arsenic, selenium and other heavy metals; the MgAl-LDHs prepared by the single titration method has a larger specific surface area, a larger pore volume and a smaller average pore size after further calcination, and has the properties of simultaneously adsorbing iron, chromium, arsenic, selenium and other heavy metals and higher adsorption performance, and has excellent COD removal efficiency in the oily wastewater, so that the treatment of the oily wastewater in the accident oil pool can be realized.

[0012] On the other hand, a method for simultaneously adsorbing transformer oil and heavy metals in an accident oil pool, the magnesium aluminum hydrotalcite calcined oxide is used as an adsorbent to be added into the oily wastewater in the accident oil pool for treatment.

[0013] The preparation method of the magnesium aluminum hydrotalcite calcined oxide is as follows: the magnesium aluminum hydrotalcite-like compound is prepared by the single titration method of the mixed solution of magnesium salt and aluminum salt and the alkaline solution containing alkali metal hydroxide and alkali metal carbonate, and the magnesium aluminum hydrotalcite-like compound is calcined to obtain the magnesium aluminum hydrotalcite calcined oxide.

[0014] The present application has the following beneficial effects:

[0015] 1. The MgAl-LDOs prepared by calcining the MgAl-LDHs prepared by the single titration method have larger specific surface area, larger pore volume and smaller average pore size, and the structure is stable, which is beneficial to increase the COD removal efficiency of the oil-containing wastewater in the accident oil pool, and simultaneously adsorb multiple heavy metals such as iron, chromium, arsenic and selenium, so as to realize the treatment of the oil-containing wastewater in the accident oil pool.

[0016] 2. In the simulated oil-containing wastewater COD degradation experiment, the MgAl-LDOs prepared by the present application are used as adsorbents, and the COD degradation of the wastewater containing 0.02% oil can reach 100%; the simulated oil-containing wastewater of the accident oil pool of a transformer substation is simulated by using 1% oil-containing wastewater, and the COD degradation rate is 81.78%, and after the adsorption treatment, the COD value meets the wastewater discharge standard; when the adsorbent concentration is 1g / L, the pH is 7, and the reaction temperature is 45℃, the maximum adsorption amount of the adsorbent for degrading COD can reach 382.34mg / g.

[0017] 3. The experiment shows that the MgAl-LDOs provided by the present application can simultaneously remove the heavy metal ions such as Fe, Cr, Se and As in the oil-containing wastewater, and the adsorption capacity is more than 158.49mg / g, 149.94mg / g, 33.10mg / g and 33.91mg / g respectively, and the simulated oil-containing wastewater of the accident oil pool can realize the standard discharge of COD and heavy metals. BRIEF DESCRIPTION OF DRAWINGS

[0018] The drawings accompanying the specification of the present application form a part of the present application and serve to further understand the present application, and the illustrative embodiments of the present application and the description thereof serve to explain the present application, and do not constitute an improper limitation on the present application.

[0019] Figure 1 The XRD patterns of the MgAl-LDHs and MgAl-LDOs prepared in Example 1 of the present application;

[0020] Figure 2 The SEM images of the MgAl-LDHs and MgAl-LDOs prepared in Example 1 of the present application, (a) is the MgAl-LDHs, and (b) is the MgAl-LDOs;

[0021] Figure 3 The N2 adsorption-desorption curve and pore size distribution graph of the MgAl-LDHs and MgAl-LDOs prepared in Example 1 of the present application;

[0022] Figure 4 The FTIR spectrum of the MgAl-LDHs and MgAl-LDOs prepared in Example 1 of the present application;

[0023] Figure 5The figure is the COD degradation rate and adsorption amount of different oil content simulated wastewater by MgAl-LDOs of the embodiment 1 of the present application as adsorbent;

[0024] Figure 6 The figure is the removal rate of heavy metals with time by MgAl-LDOs of the embodiment 1 of the present application as adsorbent;

[0025] Figure 7 The figure is the influence of temperature on the removal rate of Se and As by MgAl-LDOs of the embodiment 1 of the present application as adsorbent;

[0026] Figure 8 The figure is the influence of adsorbent concentration on the removal rate and adsorption amount of Se and As by MgAl-LDOs of the embodiment 1 of the present application as adsorbent;

[0027] Figure 9 The figure is the influence of initial concentration of Fe and Cr on the removal rate and adsorption amount by MgAl-LDOs of the embodiment 1 of the present application as adsorbent. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0029] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0030] In view of the high oil content in the transformer accident oil pool, and the presence of iron, chromium, arsenic, selenium and other heavy metal ions, the existing treatment method is difficult to treat the oil and the heavy metal ions in the transformer accident oil pool at the same time, therefore, the present application provides a method for simultaneously adsorbing transformer oil and heavy metals in the accident oil pool.

[0031] In a typical embodiment of the present application, there is provided an application of an adsorbent in simultaneously adsorbing transformer oil and heavy metals in the accident oil pool, wherein the heavy metals include iron, chromium, arsenic and selenium, the heavy metals are ions, and the adsorbent is a magnesium aluminum hydrotalcite calcined oxide;

[0032] The preparation method of the magnesium-aluminum hydrotalcite calcination oxide is as follows: a mixed solution of magnesium salt and aluminum salt is prepared by single titration method of a mixed solution of magnesium salt and aluminum salt and an alkali solution containing alkali hydroxide and alkali carbonate, and then the magnesium-aluminum hydrotalcite-like is calcined to obtain the magnesium-aluminum hydrotalcite calcination oxide.

[0033] The magnesium salt is a compound with magnesium cation, which can be an inorganic salt such as magnesium chloride, magnesium nitrate, magnesium sulfate, magnesium phosphate, etc., or an organic salt such as magnesium acetate, magnesium p-toluenesulfonate, etc. In some embodiments, the magnesium salt is magnesium chloride, magnesium nitrate or magnesium sulfate. The use of the above magnesium salt is more conducive to the crystallization of MgAl-LDHs.

[0034] The aluminum salt is a compound with aluminum cation, such as aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum phosphate, alum, etc. In some embodiments, the aluminum salt is aluminum chloride, aluminum nitrate or aluminum sulfate. The use of the above aluminum salt is more conducive to the preparation of MgAl-LDHs.

[0035] In some embodiments, the molar ratio of magnesium ions in the magnesium salt to aluminum ions in the aluminum salt is 2.9-3.1:1. The addition of magnesium ions and aluminum ions according to the stoichiometric ratio can avoid waste of chemical reagents.

[0036] The alkali hydroxide can be sodium hydroxide or potassium hydroxide.

[0037] The alkali carbonate can be sodium carbonate or potassium carbonate.

[0038] In some embodiments, the molar ratio of alkali hydroxide to alkali carbonate in the alkali solution is 3.9-4.1:1.

[0039] In some embodiments, the pH of the solution after the addition of the mixed solution of magnesium salt and aluminum salt is stabilized at 9.8-10.2 during the single titration process. This can better ensure the formation of magnesium-aluminum hydrotalcite calcination oxide.

[0040] In some embodiments, the temperature for the preparation of magnesium-aluminum hydrotalcite-like by single titration method is 50-70℃. The crystallization effect under this condition is better.

[0041] In some embodiments, the temperature for the preparation of the mixed solution by adding magnesium salt and aluminum salt into water is 50-70℃. The efficiency under this condition is higher.

[0042] In some embodiments, the process of the single titration method is as follows: under heating conditions, the mixed solution of magnesium salt and aluminum salt is added to the alkali solution containing alkali hydroxide and alkali carbonate, the pH of the solution after the addition is 9.8-10.2, and then the solution is incubated and stirred for reaction. The incubation and stirring reaction is generally performed for 20-30 hours. The incubation and stirring reaction is subjected to solid-liquid separation, washing and drying to obtain the magnesium-aluminum hydrotalcite-like.

[0043] In some embodiments, the temperature of the calcination is 450-550℃. The calcination time is 3-5h. The temperature rising process of the calcination is preferably programmed rising, which can better ensure the structural stability. The temperature rising rate of the programmed rising is preferably 2-10min / ℃.

[0044] Another embodiment of the present application provides a method for synchronously adsorbing the transformer oil and heavy metals in an accident oil pool, which comprises adding the calcined magnesium-aluminum hydrotalcite oxide as an adsorbent into the oil-containing wastewater in the accident oil pool for treatment.

[0045] The preparation method of the calcined magnesium-aluminum hydrotalcite oxide comprises: preparing a magnesium-aluminum hydrotalcite-like substance by single titration of a mixed solution of magnesium salt and aluminum salt with an alkali solution containing alkali metal hydroxide and alkali metal carbonate, and calcining the magnesium-aluminum hydrotalcite-like substance to obtain the calcined magnesium-aluminum hydrotalcite oxide.

[0046] In some embodiments, the temperature in the treatment is 25-50℃. Studies have shown that under this condition, the adsorption of the transformer oil and heavy metals in the accident oil pool can be achieved. When the treatment temperature is 40-50℃, the removal rate of heavy metal ions, especially Se and As, is higher.

[0047] In some embodiments, the adding concentration of the adsorbent in the treatment is 0.2-1.6g / L. Studies have shown that under this condition, the adsorption of the transformer oil and heavy metals in the accident oil pool can be achieved. When the adding concentration of the adsorbent is 0.1-1.1g / L, the removal rate of heavy metal ions, especially Se and As, is higher.

[0048] The magnesium salt is a compound with magnesium ions as cations, which can be an inorganic salt such as magnesium chloride, magnesium nitrate, magnesium sulfate, magnesium phosphate, etc., or an organic salt such as magnesium acetate, magnesium p-toluenesulfonate, etc. In some embodiments, the magnesium salt is magnesium chloride, magnesium nitrate or magnesium sulfate. The use of the above magnesium salt is more conducive to the crystallization of MgAl-LDHs.

[0049] The aluminum salt is a compound with aluminum ions as cations, such as aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum phosphate, alum, etc. In some embodiments, the aluminum salt is aluminum chloride, aluminum nitrate or aluminum sulfate. The use of the above aluminum salt is more conducive to the preparation of MgAl-LDHs.

[0050] In some embodiments, the molar ratio of magnesium ions in the magnesium salt to aluminum ions in the aluminum salt is 2.9-3.1:1. The addition of magnesium ions and aluminum ions according to the stoichiometric ratio can avoid the waste of chemical reagents.

[0051] The alkali metal hydroxide can be sodium hydroxide or potassium hydroxide.

[0052] The alkali metal carbonate can be sodium carbonate or potassium carbonate.

[0053] In some embodiments, the molar ratio of the alkali metal hydroxide and the alkali metal carbonate in the alkali solution is 3.9-4.1:1.

[0054] In some embodiments, the pH of the solution after the mixed solution of the magnesium salt and the aluminum salt is added dropwise in the single titration method is stabilized at 9.8-10.2. This can better ensure that the crystallization forms the magnesium-aluminum hydrotalcite calcined oxide.

[0055] In some embodiments, the temperature for preparing the magnesium-aluminum hydrotalcite-like material in the single titration method is 50-70℃. The crystallization effect is better under this condition.

[0056] In some embodiments, the temperature for preparing the mixed solution by adding the magnesium salt and the aluminum salt into water is 50-70℃. The efficiency is higher under this condition.

[0057] In some embodiments, the process of the single titration method is as follows: under heating, the mixed solution of the magnesium salt and the aluminum salt is added dropwise into an alkali solution containing an alkali metal hydroxide and an alkali metal carbonate, so that the pH of the solution after the addition is 9.8-10.2, and the reaction is carried out under heat preservation and stirring. The time for the reaction under heat preservation and stirring is generally 20-30 hours. The reaction under heat preservation and stirring is subjected to solid-liquid separation, washing, and drying, to obtain the magnesium-aluminum hydrotalcite-like material.

[0058] In some embodiments, the temperature for calcination is 450-550℃. The calcination time is 3-5 hours. The temperature rising process for calcination is preferably programmed temperature rising, which can better ensure the structural stability. The temperature rising rate for programmed temperature rising is preferably 2-10 min / ℃.

[0059] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in combination with specific examples and comparative examples.

[0060] The following examples use the single titration coprecipitation method to prepare hydrotalcite precursors, and under laboratory conditions, the hydrotalcite-like adsorption material is synthesized efficiently. The metal cation molar ratio in a certain range is more likely to form hydrotalcite with good crystallization and high purity, and the molecular formula of natural hydrotalcite is Mg6Al2(OH) 16 CO 3· 4H2O, wherein the metal ion n(M 2+ ):n(M 3+ )=3:1.

[0061] Example 1

[0062] Preparation of MgAI-LDHs and MgAI-LDOs:

[0063] n(M 2+ ):n(M 3+) = 3:1, at 60°C, n(Mg 2+ ) : n(Al 3+ ) = 3:1, 9.1485g MgCl2-6H2O (1 mol / L), 3.6214g AlCl3-6H2O were dissolved in 45ml deionized water to prepare solution A.

[0064] 3.24g NaOH, 2.1g Na2CO3 were dissolved in 180ml deionized water to prepare solution B.

[0065] Solution A was slowly added to solution B under stirring at 60°C by single drop method, the pH of solution was stabilized at 10, and the product was stirred for 24 hours to ensure the growth of hydrotalcite-like crystal, then the product was filtered and washed with deionized water until neutral, and dried in an electric heating drying oven at 80°C for 12 hours to obtain hydrotalcite-like hydroxide MgAl-LDHs.

[0066] MgAl-LDHs was placed in a muffle furnace and calcined at 500°C for 4h with a heating rate of 5°C / min to obtain composite metal oxide MgAl-LDOs.

[0067] Example 2

[0068] Preparation of MgAl-LDHs and MgAl-LDOs:

[0069] n(M 2+ ) : n(M 3+ ) = 3:1, 11.5384g Mg(NO3)2-6H2O (1 mol / L), 5.6269g Al(NO3)3-9H2O were dissolved in 45ml deionized water to prepare solution A. 2+ ) : n(Al 3+ ) = 3:1, 11.5384g Mg(NO3)2-6H2O (1 mol / L), 5.6269g Al(NO3)3-9H2O were dissolved in 45ml deionized water to prepare solution A.

[0070] 3.24g NaOH, 2.1g Na2CO3 were dissolved in 180ml deionized water to prepare solution B.

[0071] Solution A was slowly added to solution B under stirring at 60°C by single drop method, the pH of solution was stabilized at 10, and the product was stirred for 24 hours to ensure the growth of hydrotalcite-like crystal, then the product was filtered and washed with deionized water until neutral, and dried in an electric heating drying oven at 80°C for 12 hours to obtain hydrotalcite-like hydroxide MgAl-LDHs.

[0072] MgAl-LDHs was placed in a muffle furnace and calcined at 500°C for 4h with a heating rate of 5°C / min to obtain composite metal oxide MgAl-LDOs.

[0073] Example 3

[0074] Preparation of MgAI-LDHs, MgAI-LDOs:

[0075] The n(M 2+ ):n(M 3+ ) ratio was fixed at 3:1, and 11.0911 g of MgSO4·7H2O (1 mol / L) and 4.9962 g of Al2(SO4)3·6H2O were dissolved in 45 ml of deionized water to prepare solution A, with the molar ratio of n(Mg 2+ ):n(Al 3+ ) being 3:1.

[0076] Solution B was prepared by dissolving 3.24 g of NaOH and 2.1 g of Na2CO3 in 180 ml of deionized water.

[0077] Solution A was slowly added dropwise to solution B, which was stirred vigorously at 60°C, and the pH was stabilized at 10. The crystal growth of the hydrotalcite-like compound was ensured by constant temperature stirring for 24 hours. The product was filtered and washed with deionized water until neutral, and then dried in an electric heating air drying oven at 80°C for 12 hours to obtain the hydrotalcite-like compound MgAI-LDHs.

[0078] The MgAI-LDHs was placed in a muffle furnace and calcined at 500°C for 4 hours, with a heating rate of 5°C / min, to obtain the composite metal oxide MgAI-LDOs.

[0079] Example 4

[0080] Preparation of MgAI-LDHs, MgAI-LDOs:

[0081] The n(M 2+ ):n(M 3+ ) ratio was fixed at 3:1, and 9.1485 g of MgCl2·6H2O (1 mol / L) and 3.6214 g of AlCl3·6H2O were dissolved in 45 ml of deionized water to prepare solution A, with the molar ratio of n(Mg 2+ ):n(Al 3+ ) being 3:1.

[0082] Solution B was prepared by dissolving 4.54 g of KOH and 2.76 g of K2CO3 in 180 ml of deionized water.

[0083] The solution A was slowly added to the solution B under stirring at 60°C by single drop method, the pH of the solution was stabilized at 10, and the product was dried in an electric heating blast drying oven at 80°C for 12 hours after being filtered and washed with deionized water until neutralization, to obtain the hydrotalcite-like MgAl-LDHs.

[0084] The MgAl-LDHs was placed in a muffle furnace and calcined at 500°C for 4h with a heating rate of 5°C / min to obtain the composite metal oxide MgAl-LDOs.

[0085] Example 5

[0086] Preparation of MgAl-LDHs and MgAl-LDOs:

[0087] The n(Mg 2+ ):n(Al 3+ ) was fixed at 3:1, 11.5384g of Mg(NO3)2·6H2O (1mol / L) and 5.6269g of Al(NO3)3·9H2O were dissolved in 45ml of deionized water to prepare the solution A at a molar ratio of n(Mg 2+ ):n(Al 3+ ) = 3:1 at 60°C.

[0088] 4.54g of KOH and 2.76g of K2CO3 were dissolved in 180ml of deionized water to prepare the solution B.

[0089] The solution A was slowly added to the solution B under stirring at 60°C by single drop method, the pH of the solution was stabilized at 10, and the product was dried in an electric heating blast drying oven at 80°C for 12 hours after being filtered and washed with deionized water until neutralization, to obtain the hydrotalcite-like MgAl-LDHs.

[0090] The MgAl-LDHs was placed in a muffle furnace and calcined at 500°C for 4h with a heating rate of 5°C / min to obtain the composite metal oxide MgAl-LDOs.

[0091] Example 6

[0092] Preparation of MgAl-LDHs and MgAl-LDOs:

[0093] The n(Mg 2+ ):n(Al 3+ ) was fixed at 3:1, 11.5384g of Mg(NO3)2·6H2O (1mol / L) and 5.6269g of Al(NO3)3·9H2O were dissolved in 45ml of deionized water to prepare the solution A at a molar ratio of n(Mg 2+ ):n(Al 3+The ratio of MgSO4 to Al2(SO4)3 is 3:1. 11.0911g of MgSO4·7H2O (1mol / L) and 4.9962g of Al2(SO4)3·6H2O are dissolved in 45ml of deionized water to prepare solution A.

[0094] Dissolve 4.54g KOH and 2.76g K2CO3 in 180ml of deionized water to prepare solution B.

[0095] The solution A was slowly added dropwise to solution B, which was being vigorously stirred at 60°C, using a single-drop method. The pH of the solution was stabilized at 10, and the mixture was stirred at a constant temperature for 24 hours to ensure the growth of hydrotalcite-like crystals. The product was filtered with deionized water, washed until neutral, and then dried in an electric heating oven at 80°C for 12 hours to obtain hydrotalcite-like hydroxide MgAl-LDHs.

[0096] MgAl-LDHs were placed in a muffle furnace and calcined at 500℃ for 4 hours with a heating rate of 5℃ / min to obtain composite metal oxides MgAl-LDOs.

[0097] Example 7

[0098] Preparation of MgAl-LDHs and MgAl-LDOs:

[0099] Using n(M) 2+ ):n(M 3+ A fixed ratio of 3:1, at 50℃, with a molar ratio of n(Mg) 2+ ): n(Al 3+ The ratio of MgCl2 to AlCl3 is 3:1. 9.1485g of MgCl2·6H2O (1mol / L) and 3.6214g of AlCl3·6H2O are dissolved in 45ml of deionized water to prepare solution A.

[0100] Dissolve 3.24g NaOH and 2.1g Na2CO3 in 180ml of deionized water to prepare solution B.

[0101] The solution A was slowly added dropwise to solution B, which was being vigorously stirred at 50°C, using a single-drop method. The pH of the solution was stabilized at 10, and the mixture was stirred at a constant temperature for 24 hours to ensure the growth of hydrotalcite-like crystals. The product was filtered with deionized water, washed until neutral, and then dried in an electric heating oven at 80°C for 12 hours to obtain hydrotalcite-like hydroxide MgAl-LDHs.

[0102] MgAl-LDHs were placed in a muffle furnace and calcined at 500℃ for 4 hours with a heating rate of 5℃ / min to obtain composite metal oxides MgAl-LDOs.

[0103] Example 8

[0104] Preparation of MgAI-LDHs, MgAI-LDOs:

[0105] n(M 2+ ):n(M 3+ ) = 3:1, 9.1485g MgCl2-6H2O (1 mol / L) and 3.6214g AlCl3-6H2O were dissolved in 45ml deionized water to form solution A. 2+ 3+

[0106] 3.24g NaOH and 2.1g Na2CO3 were dissolved in 180ml deionized water to form solution B.

[0107] Solution A was slowly added to solution B under stirring at 70°C by single drop method. The pH of the solution was stabilized at 10. The temperature was kept constant for 24 hours to ensure the growth of hydrotalcite-like crystals. The product was filtered and washed with deionized water until neutral. The product was dried in an electric heating air drying oven at 80°C for 12 hours to obtain hydrotalcite-like compound MgAI-LDHs.

[0108] MgAI-LDHs was calcined in a muffle furnace at 500°C for 4h with a heating rate of 5°C / min to obtain composite metal oxide MgAI-LDOs.

[0109] Example 9

[0110] Preparation of MgAI-LDHs, MgAI-LDOs:

[0111] n(M 2+ ):n(M 3+ ) = 3:1, 9.1485g MgCl2-6H2O (1 mol / L) and 3.6214g AlCl3-6H2O were dissolved in 45ml deionized water to form solution A. 2+ 3+

[0112] 3.24g NaOH and 2.1g Na2CO3 were dissolved in 180ml deionized water to form solution B.

[0113] Solution A was slowly added to solution B under stirring at 60°C by single drop method. The pH of the solution was stabilized at 10. The temperature was kept constant for 24 hours to ensure the growth of hydrotalcite-like crystals. The product was filtered and washed with deionized water until neutral. The product was dried in an electric heating air drying oven at 60°C for 24 hours to obtain hydrotalcite-like compound MgAI-LDHs. ​​​​

[0114] MgAl-LDHs was placed in a muffle furnace and calcined at 500°C for 4h with a heating rate of 5°C / min to obtain the composite metal oxide MgAl-LDOs.

[0115] Example 10

[0116] Preparation of MgAl-LDHs and MgAl-LDOs:

[0117] A fixed ratio of n(Mg2+):n(Al3+) = 3:1 was adopted, 9.1485g of MgCl2·6H2O (1 mol / L) and 3.6214g of AlCl3·6H2O were dissolved in 45ml of deionized water to prepare solution A. 2+ ):n(M 3+ ) = 3:1. 2+ ):n(Al 3+ ) = 3:1.

[0118] 3.24g of NaOH and 2.1g of Na2CO3 were dissolved in 180ml of deionized water to prepare solution B.

[0119] Solution A was slowly added to solution B under stirring at 60°C by using the single drop method, the pH of the solution was stabilized at 10, and the temperature was kept constant for 24h to ensure the growth of hydrotalcite crystals. The product was filtered and washed with deionized water until neutral, and then dried in an electric heating air drying oven at 90°C for 12h to obtain hydrotalcite hydroxide MgAl-LDHs.

[0120] MgAl-LDHs was placed in a muffle furnace and calcined at 500°C for 4h with a heating rate of 5°C / min to obtain the composite metal oxide MgAl-LDOs.

[0121] Example 11

[0122] Preparation of MgAl-LDHs and MgAl-LDOs:

[0123] A fixed ratio of n(Mg2+):n(Al3+) = 3:1 was adopted, 9.1485g of MgCl2·6H2O (1 mol / L) and 3.6214g of AlCl3·6H2O were dissolved in 45ml of deionized water to prepare solution A. 2+ ):n(M 3+ ) = 3:1. 2+ ):n(Al 3+ ) = 3:1.

[0124] 3.24g of NaOH and 2.1g of Na2CO3 were dissolved in 180ml of deionized water to prepare solution B.

[0125] The solution A was slowly added to the solution B under stirring at 60°C by single drop method, the pH of the solution was kept at 10, and the crystal growth of the hydrotalcite-like MgAl-LDHs was ensured by constant temperature stirring for 24 hours. The product was filtered and washed with deionized water until neutral, and then dried in an electric heating drying oven at 80°C for 12 hours to obtain the hydrotalcite-like MgAl-LDHs.

[0126] The MgAl-LDHs was placed in a muffle furnace and calcined at 450°C for 5 hours with a heating rate of 5°C / min to obtain the composite metal oxide MgAl-LDOs.

[0127] Example 12

[0128] Preparation of MgAl-LDHs and MgAl-LDOs:

[0129] The n(Mg2+):n(Al3+) was fixed at 3:1, 9.1485g of MgCl2·6H2O (1 mol / L) and 3.6214g of AlCl3·6H2O were dissolved in 45ml of deionized water to prepare the solution A. 2+ ):n(M 3+ )=3:1. 2+ ):n(Al 3+ )=3:1.

[0130] 3.24g of NaOH and 2.1g of Na2CO3 were dissolved in 180ml of deionized water to prepare the solution B.

[0131] The solution A was slowly added to the solution B under stirring at 60°C by single drop method, the pH of the solution was kept at 10, and the crystal growth of the hydrotalcite-like MgAl-LDHs was ensured by constant temperature stirring for 24 hours. The product was filtered and washed with deionized water until neutral, and then dried in an electric heating drying oven at 80°C for 12 hours to obtain the hydrotalcite-like MgAl-LDHs.

[0132] The MgAl-LDHs was placed in a muffle furnace and calcined at 550°C for 3 hours with a heating rate of 5°C / min to obtain the composite metal oxide MgAl-LDOs.

[0133] Example 13

[0134] Preparation of MgAl-LDHs and MgAl-LDOs:

[0135] The n(Mg2+):n(Al3+) was fixed at 3:1, 9.1485g of MgCl2·6H2O (1 mol / L) and 3.6214g of AlCl3·6H2O were dissolved in 45ml of deionized water to prepare the solution A. 2+ ):n(M 3+ )=3:1. 2+ ):n(Al 3+The ratio of MgCl2 to AlCl3 is 3:1. 9.1485g of MgCl2·6H2O (1mol / L) and 3.6214g of AlCl3·6H2O are dissolved in 45ml of deionized water to prepare solution A.

[0136] Dissolve 3.24g NaOH and 2.1g Na2CO3 in 180ml of deionized water to prepare solution B.

[0137] The solution A was slowly added dropwise to solution B, which was being vigorously stirred at 60°C, using a single-drop method. The pH of the solution was stabilized at 10, and the mixture was stirred at a constant temperature for 24 hours to ensure the growth of hydrotalcite-like crystals. The product was filtered with deionized water, washed until neutral, and then dried in an electric heating oven at 80°C for 12 hours to obtain hydrotalcite-like hydroxide MgAl-LDHs.

[0138] MgAl-LDHs were placed in a muffle furnace and calcined at 500℃ for 4 hours with a heating rate of 2℃ / min to obtain composite metal oxides MgAl-LDOs.

[0139] Example 14

[0140] Preparation of MgAl-LDHs and MgAl-LDOs:

[0141] Using n(M) 2+ ):n(M 3+ A fixed ratio of 3:1, at 60℃, with a molar ratio of n(Mg) 2+ ): n(Al 3+ The ratio of MgCl2 to AlCl3 is 3:1. 9.1485g of MgCl2·6H2O (1mol / L) and 3.6214g of AlCl3·6H2O are dissolved in 45ml of deionized water to prepare solution A.

[0142] Dissolve 3.24g NaOH and 2.1g Na2CO3 in 180ml of deionized water to prepare solution B.

[0143] The solution A was slowly added dropwise to solution B, which was being vigorously stirred at 60°C, using a single-drop method. The pH of the solution was stabilized at 10, and the mixture was stirred at a constant temperature for 24 hours to ensure the growth of hydrotalcite-like crystals. The product was filtered with deionized water, washed until neutral, and then dried in an electric heating oven at 80°C for 12 hours to obtain hydrotalcite-like hydroxide MgAl-LDHs.

[0144] MgAl-LDHs were placed in a muffle furnace and calcined at 500℃ for 4 hours with a heating rate of 10℃ / min to obtain the composite metal oxide MgAl-LDOs.

[0145] The MgAl-LDHs and MgAl-LDOs prepared in Example 1 were subjected to structural and performance tests, as detailed below.

[0146] Analytical characterization method and performance detection method of structure:

[0147] 1. Analytical characterization of MgAI-LDHs, MgAI-LDOs:

[0148] 1.1 X-ray diffraction (XRD) detection:

[0149] A German Bruker D8-Advanced X-ray diffractometer was used, the instrument used Cu Kα ray, The scanning speed was 2° / min -1 , the scanning range was 5°-90°, the powder sample was ground to 320 mesh particle size, placed in the groove, and the sample was compacted flat with a clean glass sheet, the height was not more than 1 mm.

[0150] 1.2 Scanning electron microscope (SEM):

[0151] A German Zeiss Sigma500 SEM scanning electron microscope was used, the sample was fixed on the sample stage by conductive glue, and the sample was tested after gold spraying.

[0152] 1.3 Specific surface area detection:

[0153] A Quantachrome Quadrasorb evo specific surface area pore size analyzer was used, the specific surface area of the sample was calculated by BET equation, and the sample was pretreated at 150°C for 6h.

[0154] 1.4 Fourier infrared (FTIR) spectrum detection:

[0155] A Thermo Fisher Nicolet iZ10 Fourier infrared spectrometer was used, a small amount of sample was mixed with KBr, ground, and pressed into a tablet, and tested after infrared lamp baking.

[0156] 2. COD degradation:

[0157] After detection, the COD of transformer oil was higher than 10000mg / L, the transformer oil of a power plant No. 1 main substation in Jinan City, Shandong Province was used to configure oil-containing wastewater, and the wastewater of the accident oil pool under different oil-containing conditions was simulated. After digestion by the digestion instrument, the COD rapid detector was used to test the COD degradation before and after adsorption, and the COD removal rate and adsorption capacity were calculated, and the calculation formulas were as follows (1)-(2):

[0158] η=(C0-C e ) / C0*100% (1)

[0159] Q e =(C0-C e )V*10-3 η = (C0- C) / C0

[0160] η is the removal rate of the adsorbent to COD;

[0161] C0is the initial COD concentration of the oily wastewater (mg / L);

[0162] C is the COD concentration of the oily wastewater after adsorption (mg / L); e

[0163] Q is the volume of the oily wastewater (ml); e

[0164] η is the adsorption capacity of the adsorbent to COD (mg / g);

[0165] V is the volume of the oily wastewater (ml);

[0166] m is the mass of the adsorbent (g).

[0167] 3. Heavy metal adsorption:

[0168] Table 1 Heavy metal content of the wastewater sampled from the accident oil pool of No. 1 main transformer station of a power plant in Jinan, Shandong Province

[0169]

[0170] Reagent selection range and dosage range:

[0171] Reagents: magnesium chloride hexahydrate, aluminum chloride hexahydrate, sodium hydroxide, hydrochloric acid, sodium carbonate, sodium selenite, sodium chloride, sodium fluoride, sodium sulfite, sodium sulfate, ascorbic acid, thiourea, sodium borohydride, ferric nitrate nonahydrate, chromium trichloride hexahydrate, all materials are analytical pure; hydrochloric acid for atomic fluorescence instrument is superior pure; transformer oil; selenium standard solution is national standard sample GSB 04-1751-2004, arsenic standard solution is provided by National Non-ferrous Metal Analysis and Testing Center.

[0172] Simulation dosage range: ​​

[0173] The oil content of the simulated oil-containing wastewater (V 油 / V 水 ): 0.02%, 0.1%, 0.5%, 1%, 5%, 8%, 10%.

[0174] The Se content of the simulated wastewater: 1 mg / L, 10 mg / L.

[0175] The As content of the simulated wastewater: 1 mg / L, 10 mg / L.

[0176] The Fe content of the simulated wastewater: 10 mg / L, 20 mg / L, 50 mg / L, 100 mg / L, 200 mg / L.

[0177] The Cr content of the simulated wastewater: 10 mg / L, 20 mg / L, 50 mg / L, 100 mg / L, 200 mg / L.

[0178] The detection results are as follows:

[0179] 1. The analysis and characterization results of MgAl-LDHs and MgAl-LDOs prepared in Example 1 are as follows:

[0180] The XRD detection results of MgAl-LDHs and MgAl-LDOs prepared in Example 1 are as shown in Figure 1 , Figure 1 It is shown that the diffraction peaks of 003, 006, 012, 015, 018, 110 and 113 representing the specific layered structure of hydrotalcite appear in the spectrum of uncalcined MgAl-LDHs, and the peak type is sharp without other impurity peaks, indicating that the prepared hydrotalcite precursor has high purity, good crystallinity and complete structure. After calcination, the peaks of 003, 006 and 012 belonging to the layered structure of hydrotalcite still exist but are greatly weakened in the spectrum of MgAl-LDOs, and new diffraction peaks of 200 and 220 belonging to MgO appear, indicating that the layered structure of hydrotalcite collapses and forms a relatively stable metal oxide of hydrotalcite-like.

[0181] The SEM of MgAl-LDHs and MgAl-LDOs prepared in Example 1 is as shown in Figure 2 , Figure 2 It is shown that MgAl-LDHs is a cluster structure composed of many nanoparticles with uniform dispersion; after high-temperature calcination, the structure of MgAl-LDOs is more loose, the overall layered structure is unchanged, and local dehydration collapse of the layer plate occurs, which helps to expand the specific surface area of the material and promote the diffusion and transmission of the adsorbate in the interior of MgAl-LDOs material, thereby improving the adsorption performance.

[0182] The N2 adsorption-desorption curve and pore size distribution graph of MgAl-LDHs and MgAl-LDOs prepared in Example 1 are as shown inFigure 3 As shown, Figure 3 The results indicate that both MgAl-LDHs and MgAl-LDOs belong to the Type IV isotherm. When P / P0 > 0.6, a significant H3-type hysteresis loop is observed, indicating that the synthesized materials exhibit mesoporous characteristics both before and after calcination. The specific surface area of ​​MgAl-LDOs increased from 120.34 m² for MgAl-LDHs to 174.76 m² for MgAl-LDOs after calcination. 2 / g, this may be because the layered structure of hydrotalcite-like minerals collapses during calcination, releasing OH groups between the layers. - and CO3 2- They escape in the forms of H2O and CO2, respectively. Calcined MgAl-LDOs have a higher specific surface area than MgAl-LDHs, which helps to provide more adsorption active sites and improve adsorption performance.

[0183] The FTIR spectra of MgAl-LDHs and MgAl-LDOs prepared in Example 1 are as follows: Figure 4 As shown, Figure 4 This indicates that MgAl-LDHs are at 3454.61 cm⁻¹ -1 The broad peak at 1369.22 cm⁻¹ is attributed to the stretching vibration of OH groups in the hydrotalcite lamellae molecule. -1 The peak at that location belongs to the interlayer CO3 in the hydrotalcite layer. 2- The stretching vibration, 779.18cm -1 and 665.34cm -1 Representing interlayer CO3 2- Out-of-plane deformation CO stretching vibration and in-plane CO bending vibration.

[0184] In the FTIR spectra of MgAl-LDOs, OH and CO3 2- The corresponding peaks still exist but have weakened, indicating that high-temperature calcination caused some loss of interlayer water and CO3 between the layers. 2- It may be converted into CO2 and escape. The surface of calcined MgAl-LDOs still has abundant -OH groups, and in an aquatic environment, metal oxide surfaces can accumulate a large number of -OH groups, thereby achieving efficient adsorption of metal ions.

[0185] 2. The effect of MgAl-LDOs on COD degradation in oily wastewater:

[0186] Wastewater samples taken from the accident oil pool of the No. 1 main substation of a power plant in Jinan City, Shandong Province, were tested. The density was 1.0019 g / ml, and the pH was 6.58. Simulated wastewater with different oil contents was prepared using transformer oil. The adsorbent dosage was 1 g / L, the reaction temperature was controlled at 45℃, and the pH was adjusted to approximately 7. The COD degradation rate and adsorption capacity before and after the reaction are as follows: Figure 5 As shown.

[0187] With the increase of the volume fraction of transformer oil in the simulated wastewater containing oil, the adsorption capacity of the adsorbent for COD showed an upward trend, and the maximum adsorption capacity reached 382.34 mg / g. For the oil-containing wastewater with low oil content, the COD degradation rate could reach 100%. For the oil-containing wastewater with high oil content, the initial COD value before adsorption was higher, and when the oil content was 10%, the initial COD was 803.36 mg / L, and the degradation rate could still reach more than 45%. In the early stage, the COD content of the wastewater sampled from the No. 1 main transformer station accident oil pool of a power plant in Jinan, Shandong Province was tested. Under normal working conditions, the actual COD value of the accident oil pool wastewater was about 200 mg / L, which was similar to the initial COD value of the simulated wastewater with 1% oil content. The removal rate could reach 81.78%, and after adsorption, the wastewater could meet the wastewater discharge standard and could be discharged in accordance with the standard.

[0188] 3. Removal effect of MgAl-LDOs on heavy metal ions such as Fe, Cr, Se, and As in oil-containing wastewater:

[0189] In the simulated wastewater with 1% oil content, Fe, Cr, Se, and As heavy metal ions were added to explore the removal effect of the adsorbent on heavy metal ions in oil-containing wastewater. Combined with the detection of actual wastewater, the concentrations of Fe and Cr in the simulated wastewater were 10 mg / L, and the concentrations of Se and As were 1 mg / L. The adsorbent concentration was 1 g / L, the reaction temperature was 45°C, and samples were taken at 10, 20, 40, 60, 80, and 120 min. The content of various metal ions in the simulated wastewater was tested, and the removal rate of each heavy metal with time was as shown in Figure 6 .

[0190] Figure 6 It can be seen that after 120 min of adsorption reaction, the removal rates of Fe, Cr, Se, and As by the adsorbent all reached more than 98%, and the adsorbent had good removal effect on heavy metal ions in the actual accident oil pool wastewater. Among them, the adsorption of Cr and Se could quickly reach the ideal removal effect within 40 min of reaction, the adsorption of As basically reached adsorption equilibrium after 80 min, and the adsorption of Fe could reach the best adsorption effect after 120 min.

[0191] 4. Effect of temperature on adsorption effect of MgAl-LDOs on As and Se in oil-containing wastewater:

[0192] In the simulated wastewater with 1% oil content, the adsorbent had good adsorption effect on 1 ppm Se and As. In order to explore the effect of temperature on the removal rate, the removal effects of Se and As at 25, 30, 35, 40, and 50°C were compared. The adsorbent concentration was 1 g / L, pH was 7, and the reaction time was 120 min. The adsorption effect was as shown in Figure 7 .

[0193] From the above experiments, it can be seen that the adsorbent has good adsorption effect on COD, oil, and heavy metal ions in oil-containing wastewater.Figure 7 It can be seen that with the increase of temperature, the removal rate of Se and As by the adsorbent gradually increases. When the temperature is 40℃, the removal rate of 10ppm Se and As by the adsorbent can reach 86.79% and 95.65% respectively. This is because with the increase of temperature, the chemical reaction activity of hydrotalcite-like adsorbent is enhanced, which is beneficial to the combination of heavy metal ions with the active sites on the surface of the adsorbent, thereby promoting the adsorption and removal of heavy metal ions. It may also be that the increase of temperature accelerates the recovery of LDOs structure and accelerates the adsorption of heavy metal ions. With the continuous increase of temperature, the removal rate changes little, which may be because the adsorbent has reached the saturation state. In summary, in a wide temperature range, the adsorbent has good effect on the removal of heavy metal ions and can be applied to the removal of heavy metal ions in oil-containing wastewater in accident oil pool.

[0194] 5. Effect of adsorbent concentration on adsorption effect of MgAl-LDOs on As and Se in oil-containing wastewater:

[0195] In simulated wastewater with oil content of 1%, the effect of adsorbent concentration on the removal effect of 10ppm Se and As was investigated, and the adsorption capacity of the adsorbent for Se and As was calculated. The adsorbent dosage was adjusted to 0.25, 0.5, 0.75, 1 and 1.5g / L, the reaction temperature was 40℃, pH was 7, and the reaction time was 120min. The removal rate and adsorption capacity changed with the adsorbent concentration as shown in Figure 8

[0196] It can be seen from Figure 8 that with the increase of adsorbent dosage, the removal rates of Se and As increase, and when the adsorbent concentration exceeds 1g / L, the removal rate changes little, while the adsorption capacity decreases. This is because with the increase of adsorbent concentration, the total amount of active sites provided by the adsorbent in oil-containing wastewater increases, i.e. the total adsorption capacity can increase, but the amount of Se and As in wastewater is constant, so the adsorption capacity of unit mass of adsorbent for Se and As decreases. According to the experiment, the maximum adsorption capacity of the adsorbent for Se and As is 33.10mg / g and 33.91mg / g respectively. From the economic point of view, 1g / L of adsorbent can achieve good adsorption effect.

[0197] 6. Effect of initial concentration of reactants on adsorption effect of MgAl-LDOs on Fe and Cr in oil-containing wastewater:

[0198] In simulated wastewater with oil content of 1%, the effect of initial concentration of Fe and Cr on the adsorption effect was investigated, and the adsorption capacity of the adsorbent was calculated. The initial concentration of Fe and Cr in the simulated wastewater was 10, 20, 50, 100 and 200mg / L respectively, the adsorbent concentration was 1g / L, pH was 7, the reaction temperature was 40℃, and the adsorption time was 120min. The removal rate and adsorption capacity after the reaction are as follows​Figure 9 As shown.

[0199] Depend on Figure 9 It can be seen that the removal rate decreases with increasing initial concentrations of Fe and Cr, while the adsorption capacity increases rapidly. This is because the adsorption active sites on the adsorbent surface are fully utilized, and as the initial concentration of metal ions continues to increase, the adsorbent cannot provide more adsorption sites. Experiments have shown that the maximum adsorption capacities of the adsorbent for Fe and Cr are 158.49 mg / g and 149.94 mg / g, respectively, indicating ideal adsorption performance.

[0200] Comparative Example 1

[0201] MgAl-LDOs were prepared by a double titration method:

[0202] Using n(M) 2+ ):n(M 3+ A fixed ratio of 3:1, at 60℃, with a molar ratio of n(Mg) 2+ ): n(Al 3+ The ratio of MgCl2 to AlCl3 is 3:1. 9.1485g of MgCl2·6H2O (1mol / L) and 3.6214g of AlCl3·6H2O are dissolved in 45ml of deionized water to prepare solution A.

[0203] Dissolve 3.24g NaOH and 2.1g Na2CO3 in 80ml of deionized water to prepare solution B.

[0204] Using a double titration method, under stirring at 60℃, solutions A and B were added dropwise to 100ml of deionized water, maintaining the pH of the solution at 10. After the addition was complete, the solution was stirred at a constant temperature for 24 hours. The product was filtered with deionized water, washed until neutral, and then dried in an electric heating oven at 80℃ for 12 hours to obtain hydrotalcite-like hydroxide MgAl-LDHs.

[0205] MgAl-LDHs were placed in a muffle furnace and calcined at 500℃ for 4 hours with a heating rate of 5℃ / min to obtain composite metal oxides MgAl-LDOs.

[0206] Under the same adsorption conditions, the maximum adsorption capacities of the adsorbent for Se, As, Fe, and Cr were 30.12 mg / g, 31.65 mg / g, 137.56 mg / g, and 135.49 mg / g, respectively.

[0207] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. Use of an adsorbent in adsorbing both accident oil pool transformer oil and heavy metals, wherein the heavy metals include iron, chromium, arsenic and selenium, and the heavy metals are ions, and the adsorbent is a magnesium-aluminum hydrotalcite calcined oxide. The magnesium-aluminum hydrotalcite calcined oxide is prepared by a single titration method of a mixed solution of a magnesium salt and an aluminum salt with an alkali solution containing an alkali metal hydroxide and an alkali metal carbonate to prepare a magnesium-aluminum hydrotalcite-like substance, and calcining the magnesium-aluminum hydrotalcite-like substance. The single titration method comprises: under heating, adding the mixed solution of the magnesium salt and the aluminum salt to the alkali solution containing the alkali metal hydroxide and the alkali metal carbonate, and stirring and reacting.

2. Use of the adsorbent according to claim 1 for simultaneous adsorption of accident oil sump transformer oil and heavy metals, characterized in that, The magnesium salt is magnesium chloride, magnesium nitrate or magnesium sulfate. Alternatively, the aluminum salt is aluminum chloride, aluminum nitrate or aluminum sulfate.

3. Use of the adsorbent according to claim 1 for simultaneous adsorption of accident oil sump transformer oil and heavy metals, characterized in that, The molar ratio of magnesium ions in the magnesium salt to aluminum ions in the aluminum salt is 2.9-3.1:

1. Alternatively, the molar ratio of the alkali metal hydroxide to the alkali metal carbonate in the alkali solution is 3.9-4.1:

1. Alternatively, the pH of the solution after adding the mixed solution of the magnesium salt and the aluminum salt is stabilized at 9.8-10.

2.

4. Use of the adsorbent according to claim 1 for simultaneous adsorption of accident oil sump transformer oil and heavy metals, characterized in that, The temperature for preparing the magnesium-aluminum hydrotalcite-like substance by the single titration method is 50-70 ℃. Alternatively, the temperature for preparing the mixed solution by adding the magnesium salt and the aluminum salt into water is 50-70 ℃.

5. Use of the adsorbent according to claim 1 for simultaneous adsorption of accident oil sump transformer oil and heavy metals, characterized in that, Alternatively, the process of the single titration method further comprises: stabilizing the pH of the solution after adding the mixed solution of the magnesium salt and the aluminum salt at 9.8-10.

2. Alternatively, the calcination temperature is 450-550 ℃.

6. Use of the adsorbent according to claim 1 for simultaneous adsorption of accident oil sump transformer oil and heavy metals, characterized in that, The calcination time is 3-5 h.

7. Use of the adsorbent according to claim 1 for simultaneous adsorption of accident oil sump transformer oil and heavy metals, characterized in that, The temperature rising process of the calcination is programmed temperature rising, and the temperature rising rate of the programmed temperature rising is 2-10 min / ℃.

8. A method of synchronously adsorbing transformer oil and heavy metals in an accident oil sump, characterized by, The magnesium-aluminum hydrotalcite calcined oxide is used as an adsorbent to be added into oil-containing wastewater in an accident oil pool for treatment. The magnesium-aluminum hydrotalcite calcined oxide is prepared by a single titration method of a mixed solution of a magnesium salt and an aluminum salt with an alkali solution containing an alkali metal hydroxide and an alkali metal carbonate to prepare a magnesium-aluminum hydrotalcite-like substance, and calcining the magnesium-aluminum hydrotalcite-like substance. The heavy metals include iron, chromium, arsenic and selenium, and the heavy metals are ions.

9. The method of simultaneously adsorbing transformer oil and heavy metals in an oil spill accident according to claim 8, wherein, The temperature in the treatment is 25-50 ℃.

10. The method of synchronously adsorbing transformer oil and heavy metals in an accident oil sump according to claim 9, characterized in that, The temperature in the treatment is 40-50 ℃.

11. The method of simultaneously adsorbing transformer oil and heavy metals from an oil spill according to claim 8, wherein, The addition concentration of the adsorbent in the treatment is 0.2-1.6 g / L.

12. The method of simultaneously adsorbing transformer oil and heavy metals from an oil spill according to claim 11, wherein, The addition concentration of the adsorbent is 0.1-1.1 g / L.

13. The method of simultaneously adsorbing transformer oil and heavy metals from an oil spill according to claim 8, wherein, The magnesium salt is magnesium chloride, magnesium nitrate or magnesium sulfate. Alternatively, the aluminum salt is aluminum chloride, aluminum nitrate or aluminum sulfate. Alternatively, the molar ratio of magnesium ions in the magnesium salt to aluminum ions in the aluminum salt is 2.9-3.1:

1. Alternatively, the molar ratio of the alkali metal hydroxide to the alkali metal carbonate in the alkali solution is 3.9-4.1:

1.

14. The method of simultaneously adsorbing transformer oil and heavy metals from an oil spill according to claim 8, wherein, The pH of the solution after adding the mixed solution of the magnesium salt and the aluminum salt is stabilized at 9.8-10.

2. Alternatively, the temperature for preparing the magnesium-aluminum hydrotalcite-like substance by the single titration method is 50-70 ℃. Alternatively, the temperature for preparing the mixed solution by adding the magnesium salt and the aluminum salt into water is 50-70 ℃. Alternatively, the process of the single titration method comprises: under heating, adding the mixed solution of the magnesium salt and the aluminum salt to the alkali solution containing the alkali metal hydroxide and the alkali metal carbonate, and stabilizing the pH of the solution after adding the mixed solution at 9.8-10.2, and stirring and reacting. Or, the temperature of the calcination is 450~550 ℃.

15. The method of simultaneously adsorbing transformer oil and heavy metals from an oil spill according to claim 8, wherein, The calcination time is 3~5 h.

16. The method of claim 8, wherein the method further comprises, The temperature rising process of the calcination is programmed temperature rising; the temperature rising rate of the programmed temperature rising is 2~10 min / ℃.

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