Ionically modified nano-calcium hydroxide and synthetic and use methods

Abstract

The application relates to ion liquid modified nano calcium hydroxide and a synthesis method and use method thereof. An ion liquid is added into a precursor for preparing nano calcium hydroxide, and ion liquid modified nano calcium hydroxide (IL@NL) can be obtained by keeping warm at 60-90 DEG C for 30-60 minutes. The material preparation method is simple, in the material, the cation (1-butyl-3-methyl imidazole) of 1-butyl-3-methyl imidazole tetrafluoroborate is combined with the surface of nano calcium hydroxide to form a hydrogen bond. More importantly, the IL@NL can be dispersed in water to form a dispersion liquid, the stability is more than 800 minutes, in addition, test results show that the penetration depth of the IL@NL in stone cultural relics can reach 5-7 centimeters, which is more than twice the penetration depth of the currently reported nano calcium hydroxide in stone cultural relics. The material has good production prospect and can be further applied to the protection of murals and other cultural relics.

Description

Technical Field

[0001] This invention belongs to the field of cultural relic protection materials, and relates to an ionic liquid modified nano-calcium hydroxide, its synthesis method, and its application method. Background Technology

[0002] Since its introduction into cultural relic preservation in 2001, nano-calcium hydroxide has become a promising inorganic nanomaterial for the preservation of murals, stone artifacts, and other cultural relics. Generally, nano-calcium hydroxide needs to be dispersed in an alcohol solution (ethanol, isopropanol, etc.) before being applied to the surface of the artifact (J. Cult. Heritage 2016, 18, 242-249; Langmuir 2001, 17, 4251-4255). However, due to the high volatility of alcohol solutions, after application to the artifact surface, as the alcohol solution evaporates, the calcium hydroxide nanoparticles that have penetrated into the artifact are carried back to the surface, a phenomenon known as "regression." This phenomenon limits the penetration depth of nano-calcium hydroxide in the artifact, resulting in insufficient reinforcement strength (J. Cult. Heritage. 2021, 50, 25-42; Constr. Build. Mater. 2020, 230, 117112-117125). Dispersing nano-calcium hydroxide in water can prevent "re-migration." However, calcium hydroxide has extremely poor stability in water, precipitating rapidly and accumulating on the surface of cultural relics, causing serious damage. Improving the stability of nano-calcium hydroxide in water through chemical modification is currently a hot research topic. While current research can increase the stability of nano-calcium hydroxide in water to approximately 300 minutes, in practice, nano-calcium hydroxide modified with different materials still forms suspensions in water (Langmuir 2017, 33, 10936-10950), rather than dispersions. It is well known that dispersions are far more stable than suspensions. In other words, in applications for cultural relic preservation, nano-calcium hydroxide particles still rapidly agglomerate and flocculate, easily causing negative impacts on cultural relics. Summary of the Invention

[0003] Technical problems to be solved

[0004] To avoid the shortcomings of existing technologies, this invention proposes an ionic liquid-modified nano-calcium hydroxide, its synthesis method, and its application method.

[0005] Technical solution

[0006] An ionic liquid-modified nano-calcium hydroxide is characterized by the addition of an ionic liquid to the synthesis of nano-calcium hydroxide from calcium chloride and sodium hydroxide, thereby obtaining ionic liquid-modified nano-calcium hydroxide.

[0007] The amounts of each substance used in the synthesis are as follows: the molar ratio of calcium chloride to sodium hydroxide is 1:2, and the ionic liquid accounts for 10%-15% of the total mass of the system.

[0008] The ionic liquid includes, but is not limited to, 1-butyl-3-methylimidazolium tetrafluoroborate.

[0009] A method for synthesizing ionic liquid-modified nano-calcium hydroxide, characterized by the following steps:

[0010] Step 1: Add the ionic liquid to the calcium chloride solution and mix, heating the mixture to 60-90 degrees Celsius while stirring;

[0011] Step 2: After reaching the set temperature, add sodium hydroxide solution to it using a dropper. After the addition is complete, keep it warm and cool it to room temperature. Wash it with deionized water and then dry it to obtain IL@NL powder.

[0012] Dry in a vacuum drying oven at 105 degrees Celsius for 24-36 hours;

[0013] The molar ratio of calcium chloride to sodium hydroxide in the synthesis process is 1:2;

[0014] The mass ratio of the ionic liquid in the entire system is 10%-15%.

[0015] The mixture from step 1 is stirred on a magnetic stirrer.

[0016] After the addition in step 2 is complete, keep it warm for 30-60 minutes and then cool it to room temperature.

[0017] The drying in step 2 involves placing the powder in a vacuum drying oven at 105 degrees Celsius for 24-36 hours to obtain IL@NL powder.

[0018] A method for using the ionic liquid-modified nano-calcium hydroxide, characterized in that it is used for the protection of stone cultural relics.

[0019] The ionic liquid-modified nano-calcium hydroxide is added to deionized water to form a mixed solution. The solution is then applied to the surface of stone artifacts, penetrating to a depth more than twice the depth of the stone artifacts.

[0020] The mixed solution can penetrate to a depth of 5-7 cm in stone artifacts.

[0021] Beneficial effects

[0022] This invention proposes an ionic liquid-modified nano-calcium hydroxide, its synthesis method, and its application method. A commonly used ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) is added to the precursor for preparing nano-calcium hydroxide, and the mixture is kept at 60-90 degrees Celsius for 30-60 minutes to obtain 1-butyl-3-methylimidazolium-modified nano-calcium hydroxide (IL@NL). The preparation method is simple. In this material, the cation (1-butyl-3-methylimidazolium) of 1-butyl-3-methylimidazolium tetrafluoroborate forms hydrogen bonds with the surface of the nano-calcium hydroxide. More importantly, IL@NL disperses in water to form a dispersion with stability exceeding 800 minutes. Furthermore, test results show that IL@NL can penetrate 5-7 cm into stone artifacts, which is more than twice the reported penetration depth of nano-calcium hydroxide in stone artifacts. This material has good production prospects and can be further promoted for application in the protection of murals and other cultural relics. Attached Figure Description

[0023] Figure 1 This is a transmission electron microscope (TEM) image of IL@NL. The numbers in the image are scale bars. As can be seen from the image, the diameter of IL@NL is approximately 10-50 nanometers. Detailed Implementation

[0024] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

[0025] This invention provides an ionic liquid-modified nano-calcium hydroxide and its preparation method.

[0026] It is prepared mainly by the following steps:

[0027] 1-Butyl-3-methylimidazolium tetrafluoroborate was added to a calcium chloride solution and stirred on a magnetic stirrer. During stirring, the mixture was heated to 60-90°C. Once the set temperature was reached, sodium hydroxide solution was slowly added dropwise. After the addition was complete, the solution was kept at this temperature for 30-60 minutes and then cooled to room temperature. After washing with deionized water, the solution was dried in a vacuum drying oven at 105°C for 24-36 hours to obtain IL@NL powder. In the synthesis of this material, 1-Butyl-3-methylimidazolium tetrafluoroborate accounted for 10%-15% of the total mass of the system, and the molar ratio of calcium chloride to sodium hydroxide was 1:2.

[0028] Example 1:

[0029] 10% 1-butyl-3-methylimidazolium tetrafluoroborate was added to a calcium chloride solution and stirred on a magnetic stirrer. During stirring, the mixture was heated to 60°C. Once the set temperature was reached, sodium hydroxide solution was slowly added dropwise. After the addition was complete, the solution was kept at this temperature for 30 minutes and then cooled to room temperature. After washing with deionized water, the solution was dried in a vacuum drying oven at 105°C for 24 hours to obtain IL@NL powder. In the synthesis of this material, 1-butyl-3-methylimidazolium tetrafluoroborate accounted for 10% of the total mass of the system, and the molar ratio of calcium chloride to sodium hydroxide was 1:2.

[0030] Adding 5 grams of IL@NL powder to 1 liter of deionized water and sonicating for 5 minutes resulted in an IL@NL aqueous dispersion with a concentration of 5 mg / mL. UV-Vis spectrophotometry showed that this dispersion remained stable for 850 minutes, while pure nano-calcium hydroxide of the same concentration precipitated completely within 5 minutes. Applying this solution to the surface of a stone artifact and measuring the cut perpendicular to the surface revealed that IL@NL penetrated to a depth of 5 cm, while pure nano-calcium hydroxide penetrated to a depth of 1 mm.

[0031] Example 2:

[0032] 1-Butyl-3-methylimidazolium tetrafluoroborate was added to a calcium chloride solution and stirred on a magnetic stirrer. During stirring, the mixture was heated to 70°C. Once the set temperature was reached, sodium hydroxide solution was slowly added dropwise. After the addition was complete, the solution was kept at this temperature for 40 minutes and then cooled to room temperature. After washing with deionized water, the solution was dried in a vacuum drying oven at 105°C for 30 hours to obtain IL@NL powder. In the synthesis of this material, 1-Butyl-3-methylimidazolium tetrafluoroborate accounted for 12% of the total mass of the system, and the molar ratio of calcium chloride to sodium hydroxide was 1:2.

[0033] Five grams of IL@NL powder were added to one liter of deionized water and sonicated for five minutes to form an IL@NL aqueous dispersion with a concentration of 5 mg / mL. UV-Vis spectrophotometry showed that the dispersion remained stable for 820 minutes, while pure nano-calcium hydroxide of the same concentration precipitated completely within 6 minutes. When this solution was applied to the surface of a stone artifact and a section was cut perpendicular to the surface, the penetration depth of IL@NL into the stone artifact reached 6 cm. The penetration depth of pure nano-calcium hydroxide was 1.5 mm.

[0034] Example 3:

[0035] 1-Butyl-3-methylimidazolium tetrafluoroborate was added to a calcium chloride solution and stirred on a magnetic stirrer. During stirring, the mixture was heated to 80°C. Once the set temperature was reached, sodium hydroxide solution was slowly added dropwise. After the addition was complete, the solution was kept at this temperature for 50 minutes and then cooled to room temperature. The solution was washed with deionized water and then dried in a vacuum drying oven at 105°C for 32 hours to obtain IL@NL powder. In the synthesis of this material, 1-Butyl-3-methylimidazolium tetrafluoroborate accounted for 14% of the total mass of the system, and the molar ratio of calcium chloride to sodium hydroxide was 1:2.

[0036] Five grams of IL@NL powder were added to one liter of deionized water and sonicated for five minutes to form an IL@NL aqueous dispersion with a concentration of 5 mg / mL. UV-Vis spectrophotometry showed that the dispersion was stable for 870 minutes, while pure nano-calcium hydroxide of the same concentration completely precipitated within 5 minutes. When this solution was applied to the surface of a stone artifact and cut open, the penetration depth of IL@NL into the artifact reached 5.5 cm. The penetration depth of pure nano-calcium hydroxide was 1.3 mm.

[0037] Example 4:

[0038] 1-Butyl-3-methylimidazolium tetrafluoroborate was added to a calcium chloride solution and stirred on a magnetic stirrer. During stirring, the mixture was heated to 90°C. Once the set temperature was reached, sodium hydroxide solution was slowly added dropwise. After the addition was complete, the solution was kept at this temperature for 60 minutes and then cooled to room temperature. After washing with deionized water, the solution was dried in a vacuum drying oven at 105°C for 36 hours to obtain IL@NL powder. In the synthesis of this material, 1-Butyl-3-methylimidazolium tetrafluoroborate accounted for 15% of the total mass of the system, and the molar ratio of calcium chloride to sodium hydroxide was 1:2.

[0039] Five grams of IL@NL powder were added to one liter of deionized water and sonicated for five minutes to form an IL@NL aqueous dispersion with a concentration of 5 mg / mL. UV-Vis spectrophotometry showed that the dispersion remained stable for 830 minutes, while pure nano-calcium hydroxide of the same concentration precipitated completely within four minutes. When this solution was applied to the surface of a stone artifact and a section was cut perpendicular to the surface, the penetration depth of IL@NL into the stone artifact reached 7 cm. The penetration depth of pure nano-calcium hydroxide was 1.4 mm.

[0040] Table 1. Stability of IL@NL and pure nano-calcium hydroxide in water and penetration depth in stone artifacts.

[0041]

[0042] Note: A comparison of IL@NL and pure nano-calcium hydroxide aqueous solution of the same concentration revealed that IL@NL has a stability of over 800 minutes and a penetration depth of over 5 cm in stone artifacts; while pure nano-calcium hydroxide completely precipitates in water within 6 minutes and has a penetration depth of less than 2 mm in stone artifacts. The results indicate that IL@NL has excellent stability and penetration depth in aqueous solution.

[0043] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for synthesis of ion liquid modified nano calcium hydroxide, characterized in that The steps are as follows: Step 1: add the ionic liquid into the calcium chloride solution, and heat the mixed solution to 60-90 degrees Celsius during stirring; The ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate; Step 2: after reaching the set temperature, add the sodium hydroxide solution into the mixed solution by using a dropper, and keep the temperature for 30-60 minutes after the dropwise addition is completed, then cool to room temperature, and then wash with deionized water and dry to obtain IL@NL powder; The drying is drying in a vacuum drying oven at 105 degrees Celsius for 24-36 hours to obtain IL@NL powder; The molar ratio of calcium chloride to sodium hydroxide in the synthesis process is 1:2; The mass ratio of the ionic liquid to the whole system is 10%-15%.

2. The method of synthesis of claim 1, wherein: The mixing in step 1 is stirred on a magnetic stirrer.

3. An ionic liquid-modified nanocalcium hydroxide prepared by the synthetic method of claim 1 or 2, characterized in that In the synthesis of nano calcium hydroxide from calcium chloride and sodium hydroxide, an ionic liquid is added for modification to obtain ionic liquid modified nano calcium hydroxide.

4. A method of using the modified nano-calcium hydroxide of claim 3, wherein the method comprises: It is used for the protection of stone cultural relics.

5. The method of use of claim 4, wherein: The ionic liquid modified nano calcium hydroxide is added into deionized water to form a mixed solution, the mixed solution is brushed on the surface of the stone cultural relics, and the penetration depth of the mixed solution in the stone cultural relics reaches 5-7 centimeters.

Images