Magnesium-aluminum composite oxide for desalting iron cultural relics as well as preparation method and application of magnesium-aluminum composite oxide

Abstract

The invention provides a magnesium-aluminum composite oxide for desalting iron cultural relics as well as a preparation method and application of the magnesium-aluminum composite oxide. According to the method, the anion adsorbent with excellent performance is combined with the to-be-desalted iron cultural relics, an alkaline environment is provided and removal of chloride ions in the iron cultural relics is promoted under the condition that the chloride ion level in the solution is relatively low, so that the desalting efficiency of the iron cultural relics is improved, and oxidation corrosion caused by long-term soaking in the desalting solution is reduced. The method has the advantages of high desalination efficiency, fast desalination rate, simple preparation and operation methods, low cost, environmental protection, and no influence on the morphology of cultural relics.

Description

Technical Field

[0001] The invention belongs to the field of iron cultural relics desalination, and relates to the application of magnesium-aluminum composite oxide in the desalination treatment of iron cultural relics and a preparation method of the magnesium-aluminum composite oxide. Background Art

[0002] Due to the active chemical properties of iron, iron cultural relics are very prone to corrosion. There are a large number of anions in the corrosion products on the surface of water-excavated and unearthed iron cultural relics. Under certain conditions, the release of anions causes further corrosion of the iron cultural relics, or even complete corrosion. The general steps for the protection of iron cultural relics include: desalination, rust removal, slow release, and sealing. Desalination is an important part of the protection of iron cultural relics, especially the removal of chloride ions, which is beneficial to reduce the corrosion rate of iron cultural relics and achieve the purpose of long-term and stable preservation of cultural relics. Commonly used desalination methods include alkaline solution immersion method, pulp desalination method, chemical reduction method, etc. The alkaline solution desalination method has good dechlorination effect, low cost and easy implementation, but the treatment cycle is long, and the iron cultural relics are prone to secondary corrosion during the treatment process. Therefore, it is necessary to explore a new, efficient and safe desalination method.

[0003] Chinese patent CN108456892A discloses a one-step desalination and corrosion inhibition method for rusty iron cultural relics. The method is to prepare a reverse microemulsion by mixing cyclohexane, a certain concentration of silver nitrate, ammonium molybdate solution, polyoxyethylene castor oil, Span-80 and a co-surfactant according to a volume ratio, and the aqueous phase formed by the silver nitrate and ammonium molybdate penetrates into the rust layer and combines with chloride ions to remove the chloride ions, and at the same time forms a protective film on the surface of the rust layer to achieve a certain corrosion inhibition effect.

[0004] Chinese patent CN106591848A discloses a method for desalting iron cultural relics, which mixes a certain concentration of sodium hydroxide solution, styrene-based ion exchange resin, acrylic acid strong absorbent resin and DP-105 to prepare a desalting solution, and places the desalting solution and iron cultural relics in a sealed container to desalt the iron cultural relics in a circulating pressurized manner. The method does not damage the surface of the iron cultural relics, and has a high desalting rate, ensuring the integrity of the cultural relics.

[0005] Chinese patent CN114737200A discloses a dechlorination and corrosion inhibition method for iron cultural relics, which comprises mixing cationized nanocellulose with an alkaline solution to prepare a dechlorinating agent, preparing a corrosion inhibitor from cationized nanocellulose and ethanol, and immersing the iron cultural relics in the prepared dechlorinating agent under heating conditions, replacing the dechlorinating agent after a certain interval until the chloride ion concentration in the dechlorinating agent is below a certain value, and placing the dechlorinated iron cultural relics in the corrosion inhibitor. The method removes chloride ions from iron cultural relics by electrostatic action, and performs corrosion inhibition after the dechlorination is completed, which can achieve a good dechlorination effect, and form a protective layer on the surface of the iron cultural relics to prevent further corrosion of the iron cultural relics.

[0006] The above invention technologies have certain effects on the desalination of iron cultural relics. However, the types and dosages of reagents used are relatively large, and the cost is high. The desalination solution needs to be replaced regularly during the desalination process, and auxiliary conditions such as heating and pressurization are required. The operation is relatively cumbersome and time-consuming.

[0007] The present invention aims to provide a method for desalting iron cultural relics. This method transfers the chloride ions in the rust layer of the iron cultural relics to the magnesium-aluminum composite oxide through the competitive adsorption of the magnesium-aluminum composite oxide and the chloride ions in the rust layer of the iron cultural relics, thereby reducing the chloride ion content in the rust layer of the iron cultural relics. This method is time-saving, easy to operate, and has no impact on the cultural relics themselves. Summary of the invention

[0008] The purpose of the present invention is to provide a dechlorination method for iron cultural relics in view of the shortcomings of the existing desalination methods for iron cultural relics.

[0009] The desalination method of iron cultural relics of the present invention comprises the following steps:

[0010] Step 1: prepare the desalination material. The desalination material is prepared by a hydrothermal method. Mg(NO3)2·6H2O and Al(NO3)3·9H2O are prepared into a solution in a molar ratio of 2:1-4:1, and the mixture is stirred at 100 ℃ for 2 hours. - ]=4 molar ratio of urea is added and dissolved, the solution is transferred to a hydrothermal reactor and reacted at 90°C for 24 hours, centrifuged to obtain a white precipitate, and dried at 60-70°C to obtain Mg / Al-LDH, and the obtained Mg / Al-LDH is calcined at 400-500°C for 2-4 hours to obtain magnesium aluminum composite oxide (Mg / Al-LDO) for desalination of iron cultural relics.

[0011] Step 2: Ultrasonicate the simulated iron artifact sample (50mm×25mm×5mm) for 20 minutes and rinse it. Place Mg / Al-LDO and the simulated iron artifact sample in a beaker and add NaOH solution with a pH of 8-12. Adjust the position of the simulated iron artifact sample to be immersed in the NaOH solution, add Mg / Al-LDO, stir for 24 hours, and ultrasonicate for 20-30 minutes to remove the Mg / Al-LDO attached to the surface.

[0012] The desalination effect of the present invention is mild. The magnesium-aluminum composite oxide (Mg / Al-LDO) restores the layer structure in the solution through the memory effect, thereby increasing the interaction with the chloride ions and improving the release rate of the chloride ions from the iron cultural relics. The magnesium-aluminum composite oxide (Mg / Al-LDO) does not react with the iron cultural relics and is basically harmless to the iron cultural relics. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1It is the Bode diagram of the EIS test of the simulated iron sheet in Example 1 and the comparative example under the conditions of 0.01 - 100000 Hz and an amplitude of 10 mV.

[0014] Figure 2 It is the polarization curve graph of the simulated iron sheet in Example 1 and the comparative example under the conditions of open circuit potential of ±0.3 V and a scanning rate of 0.01 V / s. Specific implementation manner

[0015] The following further elaborates on the present invention in conjunction with examples, so that those skilled in the art can modify or improve it with reference to the text of the specification. However, as long as it does not depart from the basic idea of the present invention, it belongs to the scope of the present invention.

[0016] Example 1

[0017] Step 1: Preparation of desalination material: Prepare a solution with a total metal ion concentration of 0.3 mol / L by mixing Mg(NO3)2·6H2O and Al(NO3)3·9H2O in a molar ratio of 2:1. Add urea and dissolve it according to the molar ratio of [urea]:[NO3 - = 4. Transfer the solution to a hydrothermal reaction kettle and react at 90°C for 24 hours. Centrifuge to obtain a white precipitate, dry it at 60°C to obtain Mg / Al-LDH. Calcinate the obtained Mg / Al-LDH at 450°C for 4 hours to obtain a magnesium-aluminum composite oxide (Mg / Al-LDO) for desalination of iron cultural relics.

[0018] Step 2: After ultrasonically treating the simulated iron cultural relic sample for 20 minutes, rinse it thoroughly with deionized water. Place the Mg / Al-LDO and the simulated iron cultural relic sample in a beaker, add 80 ml of deionized water, adjust the pH of the desalination solution to 9 with NaOH, adjust the position of the simulated iron cultural relic sample to be immersed in the desalination solution, stir for 24 hours, and ultrasonically treat for 30 minutes to remove the desalination reagent attached to the surface.

[0019] Example 2

[0020] Step 1: Preparation of desalination material: Prepare a solution with a total metal ion concentration of 0.3 mol / L by mixing Mg(NO3)2·6H2O and Al(NO3)3·9H2O in a molar ratio of 2:1. Add urea and dissolve it according to the molar ratio of [urea]:[NO3 - = 4. Transfer the solution to a hydrothermal reaction kettle and react at 90°C for 24 hours. Centrifuge to obtain a white precipitate, dry it at 60°C to obtain Mg / Al-LDH. Calcinate the obtained Mg / Al-LDH at 450°C for 4 hours to obtain a magnesium-aluminum composite oxide (Mg / Al-LDO) for desalination of iron cultural relics.

[0021] Step 2: After 20 minutes of ultrasonic treatment of the simulated iron cultural relics sample, rinse it thoroughly with deionized water. Place the Mg / Al-LDO and the simulated iron cultural relics sample in a beaker, add 80 ml of deionized water, adjust the pH of the desalination solution to 10 with NaOH, adjust the position of the simulated iron cultural relics sample to be immersed in the desalination solution, stir for 24 hours, and ultrasonically treat for 30 minutes to remove the desalination reagent attached to the surface.

[0022] Example 3

[0023] Step 1: Preparation of desalination material: Prepare a solution with a total metal ion concentration of 0.3 mol / L by mixing Mg(NO3)2·6H2O and Al(NO3)3·9H2O in a molar ratio of 2:1. Add urea and dissolve it according to the molar ratio of [urea]:[NO3 - = 4. Transfer the solution to a hydrothermal reaction kettle and react at 90 °C for 24 hours. Centrifuge to obtain a white precipitate and dry it at 60 °C to obtain Mg / Al-LDH. Calcinate the obtained Mg / Al-LDH at 450 °C for 4 hours to obtain a magnesium-aluminum composite oxide (Mg / Al-LDO) for desalination of iron cultural relics.

[0024] Step 2: After 20 minutes of ultrasonic treatment of the simulated iron cultural relics sample, rinse it thoroughly with deionized water. Place the Mg / Al-LDO and the simulated iron cultural relics sample in a beaker, add 80 ml of deionized water, adjust the pH of the desalination solution to 11 with NaOH, adjust the position of the simulated iron cultural relics sample to be immersed in the desalination solution, stir for 24 hours, and ultrasonically treat for 30 minutes to remove the desalination reagent attached to the surface.

[0025] Comparative example

[0026] After 20 minutes of ultrasonic treatment of the simulated iron cultural relics sample, rinse it thoroughly with deionized water. Place the simulated iron cultural relics sample in a beaker, add 80 ml of deionized water, adjust the position of the simulated iron cultural relics sample to be immersed in the deionized water, stir for 24 hours, and ultrasonically treat for 30 minutes.

[0027] Use a razor blade to scrape the rust layer on the surface of the simulated iron cultural relics sample, and detect the chlorine content of the simulated iron cultural relics sample before and after treatment by EDS. Table 1 shows the dechlorination experimental effects of Example 1 and the comparative example.

[0028] Table 1 Comparison of chlorine element content in the rust layer of simulated iron sheets in Example 1 and the comparative example

[0029]

[0030]

[0031] As can be seen from Table 1, after the method of the present invention is treated at room temperature for 24 hours, the atomic percentage of chlorine in the rust layer of the simulated iron cultural relic samples is reduced, and the Cl atomic fraction of the simulated iron sheet is reduced relative to the control example, reduced to 2.86% in Example 1, reduced to 2.92% in Example 2, and reduced to 2.93% in Example 3. The chlorine in the rust layer of the simulated iron sheet is effectively removed, which is beneficial to the long-term stable preservation of the cultural relic.

[0032] The EIS test was performed on the simulated iron sheet of Example 1 and the comparative example. The test results are shown in the attached Figure 1

[0033] As attached Figure 1 As shown, at a frequency of 0.01 Hz, the impedance modulus values ​​of Example 1 and the comparative example are 593Ω and 404Ω respectively. After being treated by the method in Example 1, the resistance of the simulated iron sheet sample increases and the corrosion resistance is enhanced.

[0034] Polarization curve tests were performed on the simulated iron sheet of Example 1 and the comparative example. The test results are shown in the attached Figure 2 and Table 2

[0035] Table 2 Electrochemical parameters of polarization curves of simulated samples

[0036]

[0037] like Figure 2 As shown, the two groups of polarization curves remain basically parallel. Compared with the simulated iron sheet of the comparative example, the polarization resistance of the simulated iron sheet of Example 1 is increased to 3 times of that of the comparative example group, and the self-corrosion current is reduced to 1 / 3 of that of the comparative example. At the same time, the self-corrosion potential of Example 1 is increased from -0.44V of the comparative example to -0.38V, indicating that after being treated by the method of the present invention, the corrosion resistance of the simulated sample is significantly improved.

[0038] In summary, the magnesium-aluminum composite oxide can be used as a desalination material for iron relics, and the use method is suitable for the desalination of iron relics.

Claims

1. A method for preparing a magnesium-aluminum composite oxide for desalination of iron cultural relics, characterized in that: The magnesium aluminum composite hydroxide and the iron cultural relics are placed in an alkaline solution and stirred for 24 hours; The above-mentioned magnesium-aluminum composite oxide, i.e., Mg / Al-LDO, is prepared by hydrothermal method followed by calcination. A solution is prepared with Mg(NO3)2·6H2O and Al(NO3)3·9H2O in a molar ratio of 2:1 - 4:

1. Urea is added and dissolved according to the molar ratio of [urea]:[NO3 - = 4. The solution is transferred to a hydrothermal reactor and reacted at 90 °C for 24 hours. A white precipitate is obtained by centrifugation and dried at 60 - 70 °C to obtain Mg / Al-LDH. The obtained Mg / Al-LDH is calcined at 400 - 500 °C for 2 - 4 hours to obtain the magnesium-aluminum composite oxide for desalination of iron cultural relics.

2. The method according to claim 1, characterized in that: The alkaline solution is sodium hydroxide solution.

3. The method according to claim 1 or 2, characterized in that: The metal ion concentration in the solution of Mg(NO3)2·6H2O and Al(NO3)3·9H2O in a molar ratio of 2:1-4:1 is 0.3 mol / L.

4. The magnesium-aluminum composite oxide obtained by the method according to any one of claims 1 to 3.

5. The magnesium-aluminum composite oxide according to claim 4 is used for desalination of iron cultural relics.

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