A preparation method of nano-MgO for paper deacidification

Abstract

The present invention discloses a method for preparing nano-MgO for paper deacidification, characterized by comprising the following steps: using a magnesium alloy sheet as an anode and graphite as a cathode material, adding a surfactant as a dispersant to a sodium chloride aqueous solution, electrolyzing to prepare a Mg(OH)2 precursor, and then calcining and thermally decomposing it to prepare nano-sized MgO particles. This method has a simple preparation process, and the surfactant is directly added during the electrolysis process, which reduces the preparation process, resulting in low cost, good uniformity, and energy conservation. The prepared nano-MgO material has a moderate particle size and can be well dispersed in an organic fluorocarbon solvent, providing sufficient contact surface area for the paper. As a paper deacidification nanoparticle, it has better dispersibility in the solution and can be more evenly dispersed in the paper, achieving a good deacidification effect.

Description

Technical Field

[0001] The invention relates to the technical field of ancient book and paper deacidification and cultural relic archive protection, in particular to a method for preparing nano-MgO for paper deacidification in an organic solvent system, and belongs to the technical field of new material preparation. Technical Background

[0002] Paper is a precious and valuable paper artifact preserved in my country, possessing inestimable historical and social value. However, the acidification of paper artifacts is becoming increasingly serious, a major factor contributing to their degradation, yellowing, and disintegration. Paper is primarily composed of cellulose, which is unstable to water due to the presence of glycosidic bonds. Cellulose readily hydrolyzes under acidic conditions, leading to chain breakage, a decrease in polymerization degree, and macromolecular degradation, resulting in reduced paper strength. Furthermore, acidic substances catalyze fiber hydrolysis, ultimately causing the paper to become brittle or even pulverize. This is the fundamental cause of paper acidification. Therefore, deacidification of paper is a crucial component of the conservation of documents such as books, ancient texts, calligraphy, and paintings.

[0003] Currently, deacidification technologies for paper documents primarily include vapor-phase and liquid-phase methods. Vapor-phase deacidification requires high temperatures, high equipment costs, and is difficult to operate. Liquid-phase deacidification uses aqueous solvents, which can cause wrinkling and deformation, as well as blurring of writing on the paper, causing some damage to the paper artifact. Therefore, using non-aqueous organic solvents as deacidification agents is advantageous because they resist wetting the paper, are easy to operate, offer high deacidification efficiency, and can handle a wide range of acidic substances. Commonly used organic solvents include perfluoroalkanes and alkanes, which are non-polar solvents that do not react with paper.

[0004] MgO has a moderate alkalinity. Due to its small size, nano-sized MgO can easily penetrate fibers and enter the interior of paper. It acts between the cellulose fibers of the paper to fully neutralize the acid in the paper, effectively removing acidic substances in the paper. It also exists in the paper for a long time, neutralizing the acid and extending the shelf life of the paper. Nano-MgO is an inorganic particle, and its dispersion problem when used in paper deacidification has always been a difficult problem. To address this problem, the present invention proposes a method for electrolytically preparing highly dispersible nano-MgO in an organic system.

[0005] Common preparation methods for nano-MgO include the sol-gel method, combustion method, and hydrothermal method. The sol-gel method is time-consuming, requiring a long mixing and solidification process, and is relatively expensive; the combustion method's products are easily affected by impurities and have a wide particle size distribution; the hydrothermal method requires the use of high-temperature and high-pressure reaction conditions, and the equipment cost is relatively high. Compared with other methods, the electrolytic method for preparing nano-MgO can obtain high-purity products because the electrolysis process can effectively remove impurities and other contaminants, ensuring that the resulting magnesium oxide has a high purity. The electrolysis method is a controllable preparation method, and the preparation process of magnesium oxide can be precisely controlled by adjusting factors such as the composition of the solution and the conditions of the electrolysis. Secondly, the electrolysis method can achieve the preparation of magnesium oxide at a lower energy consumption, has a higher energy utilization efficiency, and can reduce energy consumption and environmental impact.

[0006] In order to improve the dispersibility of MgO particles in organic solution systems, researchers have conducted a lot of research. For example, CN110318294 modified nano-magnesium oxide with molten alkyl ketene dimer, and CN110331621 prepared nano-magnesium oxide and water into a dispersion liquid, and sodium dodecylbenzenesulfonate and alcohol solvent into another dispersion liquid, and mixed and heated them to obtain modified nano-magnesium oxide. These two treatment methods are costly and complex. Summary of the Invention

[0007] The purpose of the present invention is to improve the deficiencies of the prior art and provide a method for preparing nano-MgO for paper deacidification. The method uses an electrolytic system containing a surfactant to provide a simple method for preparing magnesium oxide nanomaterials with good uniformity and strong dispersibility in organic systems.

[0008] The present invention provides a method for preparing nano-MgO for paper deacidification, comprising the following steps: using a magnesium alloy sheet as an anode and graphite as a cathode material, adding a surfactant as a dispersant to a sodium chloride aqueous solution, electrolyzing a Mg(OH)2 precursor, and then calcining and thermally decomposing the precursor to produce nano-sized MgO particles. The specific steps are as follows:

[0009] (1) Using magnesium alloy sheets as anode materials and graphite electrodes as cathode materials, surface impurities are removed by grinding and cleaning to obtain clean and smooth electrode materials;

[0010] (2) dissolving NaCl in water to prepare a NaCl aqueous solution, and ultrasonically dispersing a surfactant into the electrolyte to prepare an electrolyte;

[0011] (3) Connect the circuit, connect the cathode to the graphite electrode, and the anode to the magnesium alloy sheet. After the connections are completed, immerse them in the electrolyte and turn on the DC power supply to start the electrolysis reaction;

[0012] (4) filtering, washing, and drying the Mg(OH)2 suspension produced after electrolysis to obtain a white Mg(OH)2 powder;

[0013] (5) Calcine the white Mg(OH)2 powder at 400-500°C for 1-2 hours and keep it warm for 1.8-2..2 hours to obtain nano-MgO material.

[0014] Preferably, the NaCl concentration in the NaCl aqueous solution is 0.015 to 0.030 mol / L.

[0015] Preferably, the mass ratio of the surfactant added to the NaCl is 0.11-0.23:1.

[0016] Preferably, the surfactant is polyvinylpyrrolidone (PVP), sodium dodecylbenzenesulfonate (SDBS) or sodium dodecylbenzenesulfonate (SDS).

[0017] Preferably, the electrolysis current density is 0.15 to 0.6 A / cm 2 , the electrolysis temperature is 25-30℃, and the electrolysis time is 1-2h.

[0018] Preferably, the drying temperature in step (4) is 60-80° C. and the drying time is 12-24 h.

[0019] MgO has a moderate alkalinity. The surfactant remains in the nano-MgO after high-temperature calcination of the precursor prepared by electrolysis containing a surfactant system. This alkaline deacidified nano-MgO has good dispersibility in organic fluorocarbon solvents such as 1,2,3,4-tetrafluorobenzene, 1,1,2,2-tetrafluoroethane, and 1,2,4,6-tetrafluoropropane. It can easily penetrate the fibers and enter the interior of the paper. It can effectively remove acidic substances from paper during the deacidification of paper artifacts and remains in the paper for a long time, neutralizing the acid and extending the paper's shelf life. Treatment with magnesium oxide deacidifier significantly increases the pH value of the paper, slowing its acidification and, to a certain extent, enhancing its anti-aging ability.

[0020] Beneficial effects: The present invention can effectively reduce the attraction between particles and prevent particle agglomeration by directly adding a surfactant during the electrolysis process, and can reduce the macromolecular particle size of the alkaline substance so that it can be stably dispersed in the solvent; secondly, directly adding a surfactant during the electrolysis process can reduce costs, reduce processing steps, improve uniformity, make the prepared nano-MgO more easily penetrate into paper fibers, and can also serve as an alkaline deacidification agent to increase the specific surface area and increase the interaction between alkaline particles and H + The reaction rate can better deacidify aged and acidified paper.

[0021] The preparation equipment is simple, the reaction conditions are mild, the preparation process is controllable, and the direct addition of surfactants during electrolysis is beneficial to reducing costs and avoiding secondary modification of the prepared MgO. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Take the XRD pattern of Mg(OH)2 prepared in Example 1 as an example;

[0023] Figure 2 Take the XRD pattern of MgO prepared by the invention in Example 1 as an example;

[0024] Figure 3 For example, the infrared comparison diagram of MgO prepared by the invention in Example 1 and MgO prepared without adding surfactant is shown; the upper line in the figure is MgO prepared without adding surfactant;

[0025] Figure 4 The SEM image of MgO prepared in Example 2;

[0026] Figure 5 For example, the following is a comparison of the dispersibility of MgO prepared by the invention (1#), MgO prepared by electrolysis without adding a surfactant (2#), and MgO prepared by electrolysis without adding a surfactant and then adding a surfactant (3#) in a fluorocarbon solvent; from left to right are 1# MgO prepared by the present invention, 2# MgO prepared by electrolysis without adding a surfactant, and 3# MgO prepared by electrolysis without adding a surfactant and then adding a surfactant. DETAILED DESCRIPTION

[0027] The present invention is achieved through the following technical steps:

[0028] Example 1

[0029] Weigh 0.4388g of NaCl to prepare a 0.015mol / L aqueous solution, add 0.05g of PVP, and ultrasonically disperse to obtain an electrolyte. Polished and cleaned magnesium alloy sheets and graphite electrodes are used as anode and cathode materials, respectively. The current density is 0.15A / cm 2 , the electrolysis temperature is 27℃, and the electrolysis time is 2h. After the electrolysis is completed, a white suspension is obtained, and the white precipitate is filtered out. After drying in an oven at 60℃ for 24h, a Mg(OH)2 white powder precursor is obtained. The precursor powder is quickly heated to 400℃ and calcined for 2h, and kept warm for 1.8h to obtain nano-MgO material. The National Period paper is soaked in a 0.5% MgO-perfluoroheptane deacidification solution with a standing time of 15min for 15min, and the pH value of the paper increases from 4.36 to 7.65. Figure 1 It can be seen from the X-ray diffraction spectrum that the diffraction peak of the Mg(OH)2 precursor obtained by electrolysis is sharp and narrow, indicating that the crystal form is complete and the grains are large; Figure 2 As shown, MgO has good crystallization performance; Figure 3 It can be seen that after the precursor is calcined at high temperature, the surfactant still exists in MgO and is not easily decomposed at high temperature, and can play a dispersing role.

[0030] Example 2

[0031] Weigh 0.585g of NaCl to prepare a 0.020mol / L aqueous solution, add 0.10g of SDBS, and ultrasonically disperse to obtain an electrolyte. A magnesium alloy sheet and a graphite electrode were polished and cleaned as the anode and cathode materials, respectively. The current density was 0.30A / cm 2 , the electrolysis temperature is 28℃, and the electrolysis time is 1.5h. After the electrolysis is completed, a white suspension is obtained, and the white precipitate is filtered out. After drying in an oven at 70℃ for 18h, a Mg(OH)2 white powder precursor is obtained. The precursor powder is quickly heated to 450℃ and calcined for 1.5h, and kept warm for 2h to obtain nano-MgO material. The National Period paper is soaked in a 0.5% MgO-perfluoroheptane deacidification solution with a standing time of 30min for 15min, and the pH value of the paper increases from 4.36 to 7.83. Figure 4 It can be seen that the nano-MgO particles obtained by electrolysis are aggregated together in flakes.

[0032] Example 3

[0033] Weigh 0.8775g of NaCl to prepare a 0.030mol / L aqueous solution, add 0.20g of SDS, and ultrasonically disperse to obtain an electrolyte. A magnesium alloy sheet and a graphite electrode were polished and cleaned as the anode and cathode materials, respectively. The current density was 0.60A / cm 2 , electrolysis temperature is 30℃, electrolysis time is 1h. After electrolysis, a white suspension is obtained, the white precipitate is filtered out, and after drying in an oven at 80℃ for 12h, a Mg(OH)2 white powder precursor is obtained. The precursor powder is quickly heated to 500℃ and calcined for 1h, and kept warm for 2.2h to obtain nano-MgO material. The National Period paper is soaked in 0.5% MgO-perfluoroheptane deacidification solution with a standing time of 1h for 15min, and the pH value of the paper increases from 4.36 to 8.61. Figure 5 It can be seen intuitively that the nano-MgO prepared by adding a surfactant during electrolysis has better dispersion in a fluorocarbon solvent than the MgO prepared by electrolysis without adding a surfactant. Compared with preparing MgO by electrolysis without adding a surfactant and then adding a surfactant, it saves steps and saves costs.

Claims

1. A method for preparing nano-MgO for paper deacidification, characterized in that The method comprises the following steps: using a magnesium alloy sheet as an anode and graphite as a cathode material, adding a surfactant as a dispersant to a sodium chloride aqueous solution, electrolyzing and preparing a Mg(OH)2 precursor, and then calcining and thermally decomposing the precursor to prepare nano-sized MgO particles. The specific steps are as follows: (1) Using magnesium alloy sheets as anode materials and graphite electrodes as cathode materials, surface impurities are removed by grinding and cleaning to obtain clean and smooth electrode materials; (2) dissolving NaCl in water to prepare a NaCl aqueous solution, and ultrasonically dispersing a surfactant into the electrolyte to prepare an electrolyte; the ratio of the amount of the surfactant added to the mass of NaCl is 0.11-0.23:1; the surfactant is sodium dodecylbenzenesulfonate or sodium dodecylsulfonate; (3) Connect the circuit, connect the cathode to the graphite electrode, and the anode to the magnesium alloy sheet. After the connection is completed, immerse them in the electrolyte and turn on the DC power supply to perform the electrolysis reaction; the electrolysis current density is 0.15 to 0.6 A / cm 2 , the electrolysis temperature is 25-30°C, and the electrolysis time is 1-2h; (4) filtering, washing, and drying the Mg(OH)2 suspension produced after electrolysis to obtain a white Mg(OH)2 powder; (5) Calcine the white Mg(OH)2 powder at 400-500°C for 1-2 hours and keep it warm for 1.8-2..2 hours to obtain nano-MgO material.

2. The preparation method according to claim 1, wherein The NaCl concentration in the NaCl aqueous solution is 0.015-0.030 mol / L.

3. The preparation method according to claim 1, wherein The drying temperature in step (4) is 60-80° C., and the drying time is 12-24 hours.

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