A crystallization modifier material and its application in the desalination of stone cultural relics

Abstract

The application discloses a crystallization modifier material and application thereof in desalination of stone cultural relics, and belongs to the field of material chemistry. The crystallization modifier material comprises an alkali metal sulfate modifier material or an alkali metal chloride salt modifier material. The chloride salt is modified by meso-tartaric acid ferrous and meso-tartaric acid iron, and the sulfate is modified by a low-molecular-weight polyepoxysuccinic acid, a low-molecular-weight polyaspartic acid, a diethylene triamine penta-methylene phosphonic acid and a polyepoxysuccinic acid compound. The tartaric acid salt is non-toxic, and the polyepoxysuccinic acid and the polyaspartic acid are green and environment-friendly and biodegradable; the compound reduces the dosage of the poor-degradability phosphonic acid salt. The modifier accelerates the evaporation and migration rate of the salt solution, and also changes the crystallization habit of the precipitated salt, so that the salt is changed from a compact block shell into a loose branch and a nanosheet, greatly reducing the salt crystallization pressure in micropores and the damage to pore walls. Compared with a traditional deionized water pulp pasting method, the method has obvious efficiency improvement, and the weathering amount is reduced by 1.5-4 times compared with the weathering amount of the traditional pasting method.

Description

TECHNICAL FIELD

[0001] The application relates to a crystallization modifier and application in desalination of stone cultural relics, and belongs to the technical field of inorganic materials. BACKGROUND

[0002] Soluble salts distributed in different pores are the most common factors causing weathering and damage of large immovable cultural relics such as stone ancient buildings, grotto temples and stone sculptures. Due to the changes of temperature and moisture in the environment of the stone porous material, the crystallization and dissolution of the soluble salt in the pores change, accompanied by repeated changes in volume expansion and contraction. Thus, the stone cultural relics appear to be powdery, cracked and brittle, resulting in the loss of cultural value. These weathering salts are mainly sulfates, chlorides and nitrates. Among them, the damage of alkali metal sulfates and chlorides is the most common.

[0003] When the salt crystallizes in the pores of the stone cultural relics, crystallization pressure is generated. Sulfate salts often have more crystallization water when crystallizing, such as mirabilite, which increases in volume by more than 3 times. This crystallization pressure often exceeds the tensile strength of the stone, causing the pore wall to crack and the pore structure of the stone cultural relics to be damaged. The volume of sulfate also expands when it hydrates, so the removal of soluble salts in immovable stone cultural relics has always been the focus of cultural heritage workers.

[0004] How to efficiently remove soluble salts in outdoor immovable stone cultural relics is a technical problem, because it is very difficult to completely eliminate water sources and salt sources for these cultural relics, and only periodic desalination can be performed. At present, the most commonly used desalination materials are paper pulp desalination, mortar desalination and paste desalination. This desalination method has low desalination efficiency and long time consumption (Zeng Xiangjiao, Laboratory evaluation of desalination material effect on sandstone stone cultural relics, Master thesis, 2019).

[0005] In recent years, ferrocyanide and diethylene triamine pentaformyl phosphonic acid have been used for desalination of stone cultural relics (a desalination method for stone and stone cultural relics using crystallization inhibitors, CN 101921135B). The desalination efficiency is high, but the ferrocyanide used is easy to oxidize and turn blue, which pollutes the surface of the stone cultural relics. The organic phosphonic acid compound has a high phosphorus content and poor degradation performance. Therefore, the development of a low-phosphorus, environmentally friendly and degradable salt crystallization modifier can solve the above problems. SUMMARY

[0006] In order to solve the above technical problems, the application provides a high desalination efficiency and low weathering amount of stone cultural relics desalination modifier material and application method. The crystallization modifier material includes alkali metal sulfate modifier material or alkali metal chloride salt modifier material. Among them: the chloride salt is modified by meso ferrous tartrate and meso ferric tartrate, and the sulfate is modified by low molecular weight polyepoxysuccinic acid, low molecular weight polyaspartic acid, diethylene triamine pentaformyl phosphonic acid and polyepoxysuccinic acid compound. The tartrate in the application is non-toxic, and the polyepoxysuccinic acid and polyaspartic acid are green and environmentally friendly and biodegradable; the compound reduces the poor degradability of phosphonic acid salt. The modifier accelerates the evaporation and migration rate of the salt solution, and also changes the crystallization habit of the precipitated salt, so that it changes from a compact block shell to a loose branched and nanosheet, greatly reducing the salt crystallization pressure in the micropore and the damage to the pore wall. The method has higher efficiency than the traditional deionized water paper pulp application method, and the weathering amount is 1.5-4 times lower than that of the traditional application method.

[0007] The crystallization modifier material provided by the application includes alkali metal sulfate material or alkali metal chloride salt material, wherein: the alkali metal sulfate is modified by low molecular weight polyepoxysuccinic acid, low molecular weight polyaspartic acid or diethylene triamine pentaformyl phosphonic acid and polyepoxysuccinic acid compound; and the alkali metal chloride salt is modified by meso ferrous tartrate or meso ferric tartrate.

[0008] Further, in the above technical solution, the concentrations of the polyepoxysuccinic acid and the polyaspartic acid are 0.1-0.5% (w / w) and 0.06-0.5% (w / w) respectively; the concentration of the diethylene triamine pentaformyl phosphonic acid and the polyepoxysuccinic acid compound is 0.1-0.6% (w / w); and the concentrations of the meso ferrous tartrate and the meso ferric tartrate are 0.05-0.1% (w / w) and 0.08-0.5% (w / w) respectively.

[0009] Further, in the above technical solution, the mass ratio of the diethylene triamine pentaformyl phosphonic acid and the polyepoxysuccinic acid compound is 1:2-3.

[0010] The application of the salt crystallization modifier material in the desalination of stone cultural relics includes the following specific steps:

[0011] (1) preparing an aqueous solution of the aforementioned crystallization modifier;

[0012] (2) wetting the surface of the sandstone, and wetting the paper pulp with the prepared aqueous solution of the crystallization modifier and applying it to the salt damage site;

[0013] (3) covering the paper pulp with a moisture-retaining film, and placing it for 4-6 hours to ensure the penetration depth of the modifier solution;

[0014] (4) removing the moisture-retaining film and the paper pulp.

[0015] Further, in the above technical solution, after the steps (1) to (4) are completed, deionized water or distilled water is used instead of the salt crystallization modifier aqueous solution to repeat the above steps (2) to (4).

[0016] Further, in the above technical solution, the pH value of the polyepoxysuccinic acid and polyaspartic acid modifier aqueous solution is adjusted to 7 by NaOH;

[0017] Further, in the above technical solution, the pH value of the diethylenetriamine pentamethylene phosphonic acid and polyepoxysuccinic acid compound aqueous solution is adjusted to 8 by NaOH.

[0018] Further, in the above technical solution, the pH values of the aqueous solutions of ferrous and ferric racemic tartaric acid are 4-5 and 5, respectively.

[0019] Further, in the above technical solution, the steps 2) to 4) can be repeated multiple times.

[0020] The present application has the following advantages:

[0021] 1. The efficiency of the present application is improved by 3 times compared with the traditional deionized water pulp application method, and the weathering amount is lower than that of the traditional application method. The alkali metal sulfate single modifier is green and biodegradable, and the compound modifier reduces the amount of phosphorus. Among them, the sulfate modifier reduces the content of poor degradability phosphonate, and biodegradable green materials are applied, and the chloride salt modifier does not change the color of stone cultural relics; the alkali metal chloride salt modifier does not change the surface color of stone cultural relics.

[0022] 2. The modifier in the present application accelerates the evaporation and migration rate of the salt solution, and changes the crystallization habit of the precipitated salt, making it change from a compact shell to a loose dendritic and nanosheet, which greatly reduces the salt crystallization expansion force and the damage to the pore wall. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The scanning electron microscope image of sodium sulfate; wherein: a, b, c are respectively added polyaspartic acid sodium, polyepoxysuccinic acid sodium and 0.4% compound modifier M-3:7;

[0024] Figure 2 The video microscope image of sodium sulfate; wherein: a, b are respectively added sodium chloride modifier ferrous and ferric racemic tartaric acid;

[0025] Figure 3 The desalination efficiency and weathering product diagram of adding sodium sulfate modifier;

[0026] Figure 4The desalination efficiency and weathering product map of the desalination efficiency of the addition of sodium chloride modifier. DETAILED DESCRIPTION

[0027] The application is described in detail below with reference to examples:

[0028] 1. Preparation of sandstone simulation test block

[0029] (1) Pretreatment of sandstone test block: Take Sichuan red sandstone as the laboratory sample, cut the Sichuan sandstone into a 5 cm x 5 cm x 5 cm cube, wash off the surface sand, soak the sandstone in distilled water for 24 h, measure the conductivity of the distilled water, repeat the operation of changing the water until the conductivity of the distilled water is reduced to the minimum value and remains unchanged, and then dry in a 60°C oven. After natural cooling, number and weigh.

[0030] (2) Vertical salt absorption: seal the cleaned and desalted sandstone with epoxy resin around the bedding direction, leaving only the upper and lower ends of the bedding, and record the weight after the resin is dry. Place a 1 cm thick nanometer sponge in the storage box, place the lower end of the sandstone on the sponge, and add saturated sodium sulfate or saturated sodium chloride solution to the contact surface between the sandstone and the sponge. Ensure that the soluble salt only undergoes capillary migration in the vertical direction. After the upper surface is completely wet, wipe off the hanging solution on the upper and lower surfaces, dry in a 60°C oven until the weight is constant, and then cool naturally and weigh.

[0031] (3) Bottom sealing: to ensure that the salt is only precipitated from the upper surface during desalination, the bottom of the salt-absorbed sandstone sample is wrapped with a removable adhesive tape.

[0032] 2. Desalination treatment of sandstone simulation test block

[0033] Step (1): prepare a crystalline modifier aqueous solution;

[0034] Step (2): wet the surface of the sandstone, wet the paper pulp with the prepared crystalline modifier aqueous solution, and apply it to the salt damage site;

[0035] Step (3): cover the paper pulp with a moisture-retaining film and place it for 4 h to ensure that the modifier solution penetrates to a certain depth;

[0036] Step (4) remove the moisture-retaining film and paper pulp.

[0037] After the above steps, deionized water or distilled water is used instead of the crystalline modifier aqueous solution, and steps (2) to (4) are repeated.

[0038] The steps (2) to (4) of the salt crystallization modifier aqueous solution desalination method can be repeated multiple times.

[0039] Deionized water is used instead of the crystalline modifier aqueous solution, and the steps can be repeated multiple times until the desired desalination effect is achieved.

[0040] The biggest difference between the above desalination method and the traditional deionized water paste desalination is that the salt crystal modifier is added to the stone cultural relics in the initial desalination process.

[0041] 3. Desalination effect

[0042]

[0043] Example 1

[0044] ①The concentration of the polyepoxysuccinic acid aqueous solution is 0.2% (w / w), and the pH value of the solution is adjusted to 7. ②The paper pulp is fully wetted with the solution and then pasted on the surface of the sandstone containing sodium sulfate; ③The paper pulp is covered with a plastic film, and small holes are opened on the film to facilitate water evaporation; ④The film and paper pulp are removed after 4 hours; ⑤The salt on the surface of the sandstone is swept away, and the paper pulp is placed in a beaker together with a certain amount of deionized water or distilled water to test the water conductivity. ⑥The paper pulp and water are separated, and the weathered sandstone particles are filtered out and dried at 105°C, and then weighed.

[0045] The salt crystal modifier compound solution is replaced with deionized water or distilled water, and steps ②-⑥ are repeated for five times of paste desalination cycles.

[0046] As a blank control, according to the above desalination process, deionized water or distilled water is used for desalination from the first cycle to the sixth cycle, and the desalination efficiency and weathering product curve (Fig. 2) are obtained. Figure 3 The desalination efficiency is 3 times that of the traditional deionized water paste method, and the total weathering amount of 6 times of paste is about 1.5 times lower than that of the traditional paste method.

[0047] The desalination efficiency of each cycle is represented by the size of the measured conductivity value.

[0048] Example 2

[0049] The operation is the same as in Example 1, except that polyaspartic acid is used for the first paste, with a solution concentration of 0.1% (w / w) and a solution pH value adjusted to 7. The desalination efficiency curve and weathering product curve are Figure 3 The desalination efficiency is 2-3 times that of the traditional deionized water paste method, and the total weathering amount of 6 times of paste is about 1.5 times lower than that of the traditional paste method.

[0050] Example 3

[0051] The operation is the same as in Example 1, except that a mass ratio of 1:3-1:2, a concentration of 0.3% (w / w) diethylene triamine pentaformyl phosphonic acid and polyepoxysuccinic acid salt crystal modifier compound aqueous solution is used for the first paste, and the solution pH value is adjusted to 8.

[0052] In Example 3, the desalination efficiency and weathering product of the compound are quantitatively represented by the optimal mass ratio of 3:7. The desalination efficiency and weathering product curve are shown in Figure 3 The desalination efficiency of the modifier compound is about 2 times of the deionized water, and the weathering amount of the modifier compound is far less than that of the traditional paste method, and the total weathering amount of 6 times of paste is about 4 times less than that of the traditional paste method.

[0053] Example 4

[0054] The same as example 1, except that the sandstone sample containing sodium sulfate is replaced by the sandstone sample containing sodium chloride, and the modifier is aqueous solution of meso-ferrous tartrate with a concentration of 0.05% (w / w) and a pH value of 4-5. The obtained desalination efficiency curve and weathering product curve are shown in Figure 4 The desalination efficiency of the modifier compound is about 2 times of the deionized water, and the weathering amount of the modifier compound is far less than that of the traditional paste method, and the total weathering amount of 6 times of paste is about 4 times less than that of the traditional paste method.

[0055] Example 5

[0056] The same as example 4, except that the modifier is meso-ferrous tartrate with a concentration of 0.1% (w / w) and a pH value of 5. The obtained desalination efficiency curve and weathering product curve are shown in Figure 4 The desalination efficiency of the modifier compound is about 2 times of the deionized water, and the weathering amount of the modifier compound is far less than that of the traditional paste method, and the total weathering amount of 6 times of paste is about 4 times less than that of the traditional paste method.

[0057] The above examples describe the basic principles, main features and advantages of the present application. It should be understood by those skilled in the art that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the principles of the present application, various changes and improvements can be made, and these changes and improvements all fall within the scope of the present application.

Claims

1. Application of a salt crystal modifier in desalination of stone cultural relics, characterized in that: The specific steps include: (1) preparing an aqueous solution of a salt crystal modifier; the salt crystal modifier is a mixture of diethylenetriamine penta (methylene phosphonic acid) and polyepoxysuccinic acid; wherein the mass ratio of diethylenetriamine penta (methylene phosphonic acid) to polyepoxysuccinic acid is 1:2-3; and the concentration of the aqueous solution of the mixture of diethylenetriamine penta (methylene phosphonic acid) and polyepoxysuccinic acid is 0.1-0.6% (w / w); (2) Wetting the sandstone surface containing sodium sulfate, fully moistening the pulp with the prepared aqueous solution of salt crystal modifier, and applying it to the salt-damaged area; (3) Cover the pulp with a moisturizing film and leave it for 4-6 hours to ensure the penetration depth of the modifier solution; (4) Remove the moisturizing film and pulp.

2. The use of the salt crystal modifier in the desalination of stone cultural relics according to claim 1, characterized in that: The pH value of the aqueous solution of the mixture of diethylenetriamine penta (methylene phosphonic acid) and polyepoxysuccinic acid was adjusted to 8 using NaOH.

3. The use of the salt crystal modifier in the desalination of stone cultural relics according to claim 1, characterized in that: Steps (2) to (4) are repeated multiple times.

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