A reusable acid-base indicating material and preparation method thereof

Abstract

The present invention discloses a reusable acid-base indicator material and a preparation method thereof. The acid-base indicator material comprises a base material and an acid-base indicator material, wherein the base material is formed by tightly winding micron-sized plant fibers, and the acid-base indicator material is attached to the surface of the plant fibers. The preparation method of the present invention comprises: treating the surface of the plant fibers with a chemical solution, and the surface of the plant fibers is in contact with and adsorbed by the indicator material during the treatment process; then washing with acid or water to remove chemical residues in the sample, and drying to obtain the material. The acid-base indicator material prepared by the present invention can be reused, and the preparation method thereof has the characteristics of a wide source of raw materials, low cost, simple preparation steps, etc., and has a wide range of applications.

Description

Technical Field

[0001] The invention relates to a reusable acid-base indicating material and a preparation method thereof, and belongs to the field of artificial microstructure materials. Background Art

[0002] In production, life and experiments, it is often necessary to quantitatively or qualitatively test the acidity and alkalinity of the solution. Quantitative testing generally uses a pH meter. However, in most scenarios, accuracy is not considered, and only qualitative testing of the acidity and alkalinity of the solution is required. In terms of accuracy, pH test paper generally does not meet the accuracy requirements, so it is often used for qualitative testing. pH test paper is also the most commonly used test material in experiments. However, the disadvantage of pH test paper is that it cannot be reused, which will undoubtedly cause a waste of resources.

[0003] Therefore, it is urgent to develop a reusable acid-base indicator material. This material must have abundant raw material sources and can be used for cyclic detection in acid-base solutions, that is, it must maintain its own structure under acid-base solution conditions. Natural cellulose is the most abundant natural polymer in nature, with the advantages of low cost, renewability, and environmental friendliness. Therefore, the use of cellulose to prepare new materials has great scientific value and social significance.

[0004] Plant fibers can maintain their own structure in acidic and alkaline solutions through microstructural regulation. In the process of microstructural regulation, materials with acid-base indication functions are introduced to combine with cellulose fibers, which can give the materials the ability to indicate acid-base, so that the acidity and alkalinity of the solution can be repeatedly detected. The material can be immersed in the solution to achieve real-time detection. However, there are no reports on the use of plant fiber materials for reusable acid-base detection of solutions. Summary of the invention

[0005] The purpose of the present invention is to provide a new material for real-time acid-base detection by using micron-sized plant fibers. Another purpose of the present invention is to provide a method for preparing the new material.

[0006] The technical solution adopted by the present invention is:

[0007] A reusable acid-base indicator material comprises a base material and an acid-base indicator material. The base material is formed by tightly winding micron-level plant fibers, and the acid-base indicator material is attached to the surface of the plant fibers.

[0008] Furthermore, the density of the matrix material is 1.4-1.6 g / cm 3 , the tensile strength is 80-90MPa.

[0009] The present invention provides a method for preparing a reusable acid-base indicating material, comprising the following steps:

[0010] (1) treating the plant fiber with treatment solution A for a certain period of time to increase the number of nanofibers on the surface of the plant fiber, so that the plant fiber is dispersed and fully combined with the acid-base indicator material in solution A;

[0011] (2) treating the plant fiber treated in step (1) at a low temperature for a certain period of time to harden the fiber into a block material;

[0012] (3) placing the fibers of the block material in the treatment solution B for a period of time, and then soaking them in acid or water to wash away the chemical residues;

[0013] (4) The fiber block obtained in step (3) is dried to obtain the reusable acid-base indicating material.

[0014] Furthermore, in step (1), the treatment solution A includes a strong alkaline solution, an alkali / urea mixed solution, a lithium chloride / dimethylacetamide solution, an ionic liquid, a cuprammonia solution or an N-methylmorpholine-N-oxide solution.

[0015] Furthermore, in step (1), the acid-base indicator material is a compound having an acid-base indicating effect, such as nitrophenol, phenolphthalein, sulfonated phenolphthalein or azo dye.

[0016] Furthermore, in step (2), the treatment time is specifically 2 hours to 12 hours.

[0017] Furthermore, in step (3), the treatment solution B is hydrochloric acid solution, acetic acid solution, sulfuric acid solution or water, or any safe combination of the above solutions.

[0018] Furthermore, in step (3), the treatment time is specifically 1 minute to 72 hours.

[0019] The present invention uses plant fibers (such as cotton fibers but not limited to cotton fibers) and acid-base indicating materials (such as litmus, phenolphthalein, etc.) as raw materials, and controls the morphology of the fibers to control the microstructure of the materials, thereby giving the materials new properties. The advantages of the present invention are:

[0020] (1) The obtained reusable acid-base indicator material is composed of plant fiber and trace indicator material, does not contain other foreign substances, and has acid and alkali resistance.

[0021] (2) The preparation process only requires placing the plant fiber in the treatment solution to partially dissolve and adsorb the indicator material, without involving other complex chemical processes, and the production process is simple. In addition, the plant fiber has a strong adsorption capacity for the indicator material, so that the indicator material will not desorb during use.

[0022] (3) The plant fibers and indicator materials used in the preparation of the materials are very abundant in source, which makes the preparation method of the present invention highly operable, low in production cost and short in time.

[0023] (4) The acid-base indicating material prepared by the present invention has a recyclable acid-base indicating function and can maintain its original structure in an acidic or alkaline solvent. It can be immersed in a solution to perform real-time detection of the acidity and alkalinity of the solution. It has broad application prospects in production, experiments and other fields in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a scanning electron microscope image of the surface morphology of the acid-base indicating material prepared in Example 1;

[0025] Figure 2 This is a physical picture of the acid-base indicating material prepared in Example 1;

[0026] Figure 3 This is a performance diagram of the acid-base indicating material prepared in Example 1 when recycled in an acid-base solution. DETAILED DESCRIPTION

[0027] Embodiment 1:

[0028] Mix 10g of cellulose fiber from cotton with 7% NaOH, 12% urea, and 0.05% Congo red dye (an azo indicator) aqueous solution and stir thoroughly. The required volume of sodium hydroxide, urea and dye aqueous solution is 100ml. The mixed solution was frozen at -18°C for 1 hour and then taken out. The shape of the fiber changed from straight to twisted, and the fiber surface was slightly dissolved, exposing a fresh surface and adsorbing the dye. After the fiber was taken out of the solution, it was immersed in water for 10 hours, and then washed with deionized water several times, and then the washed sample was dried. During the water loss process, the fiber actively shrank to form a dense structure, and finally the acid-base indicating material was obtained. The actual picture of this material is shown in Figure 2 As can be seen from the figure, the acid-base indicating material of this embodiment has the texture of a plastic plate, and is hard, high in strength, and has a density (about 1.2-1.6 g / cm 3 ) is close to the theoretical density of cellulose (about 1.6 g / cm 3 ). This material has an acid-base indicator function, half of it is red, and the other half turns blue when immersed in an acidic solution.

[0029] The scanning electron microscope image is as follows Figure 1 As shown in the figure, it can be seen that the material is composed of micron-sized plant fibers, which are bent, deformed and tightly entangled to form a very dense structure. Figure 3It shows that the prepared acid-base indicator material can be recycled in acid-base solution. This is because the fiber is dissolved and evenly dispersed in the solvent, which increases the contact area with the dye, increases the hydrogen bond density between the fiber and the dye, and strengthens the van der Waals force. The subsequent drying treatment then causes the material to shrink further, so that the dye is firmly fixed on the fiber and will not desorb.

[0030] Embodiment 2:

[0031] 8g of cellulose fiber from wood was mixed with 7% NaOH, 12% urea, and 0.05% Congo red dye aqueous solution and stirred thoroughly. The volume of the aqueous solution required was 100ml. The resulting mixed system was frozen at -13°C for 3 hours. The fiber morphology changed from straight to twisted, and the fiber surface was slightly dissolved, exposing a fresh surface and adsorbing the dye. After the fiber was taken out of the solution, it was immersed in dilute hydrochloric acid for 72 hours, then washed with deionized water, and then the washed sample was dried. During the dehydration process, the fiber actively shrank to form a dense structure, and finally an acid-base indicator material was obtained.

[0032] Embodiment 3:

[0033] 10g of cellulose fiber from cotton was mixed with 7% NaOH, 12% urea, and 0.05g of litmus powder aqueous solution, and stirred thoroughly. The required volume of sodium hydroxide, urea and litmus aqueous solution was 100ml. The mixed solution was frozen at -18℃ for 1 hour and then taken out. The fiber morphology changed from straight to twisted, and the fiber surface was slightly dissolved, exposing the fresh surface and adsorbing the dye. After the fiber was taken out of the solution, it was immersed in dilute sulfuric acid in water for 10 hours, and then washed with deionized water several times, and then the washed sample was dried. During the dehydration process, the fiber actively shrank to form a dense structure, and finally the acid-base indicator material was obtained.

[0034] Embodiment 4:

[0035] 20g of cellulose fiber from wheat straw was mixed with 7% NaOH, 12% urea aqueous solution and 5ml phenolphthalein solution, and stirred thoroughly. The volume of sodium hydroxide urea and phenolphthalein aqueous solution required was 160ml. The mixed solution was frozen at -15℃ for 2 hours and then taken out. During this process, the fiber swelled and spirally twisted, and the fiber surface was slightly dissolved, exposing the fresh surface and effectively adsorbing phenolphthalein. After the fiber was taken out of the solution, it was immersed in water for 48 hours, and then washed with deionized water several times, and then the washed sample was dried. During the drying process, the fiber actively shrank to form a dense structure, and finally the acid-base indicator material was obtained.

[0036] Embodiment 5:

[0037] 10g of cellulose fiber from cotton was mixed with an aqueous solution of 7% NaOH, 12% urea and 0.05g methyl orange powder, and stirred thoroughly. The volume of the aqueous solution of sodium hydroxide, urea and methyl orange required was 110ml. The mixed solution was frozen at -18℃ for 10min and then taken out. At this time, the fiber swelled and twisted, the fiber surface was slightly dissolved, the fresh surface was exposed, and the fiber adsorbed methyl orange. After the fiber was taken out of the solution, it was immersed in hydrochloric acid for 48 hours, and then washed with deionized water several times, and then the washed sample was dried. At this time, the sample actively shrank to form a dense structure, and finally the acid-base indicator material was obtained.

[0038] Embodiment 6:

[0039] 10g of cellulose fiber from rice straw was mixed with 8g of lithium chloride / DMAc: 100ml and 0.05g of Congo red solution, and reacted at 140℃ for 30min. The resulting mixed system was left to stand for 10 hours, and the cellulose surface was slightly dissolved, exposing a fresh surface, and the fiber evenly adsorbed the dye. After the fiber was taken out of the solution, the material was washed with deionized water several times, and then the washed sample was dried to obtain the acid-base indicator material.

[0040] Embodiment 7:

[0041] 100g of cellulose fiber from vine plants was mixed with 7% NaOH, 12% urea, and 0.05% Congo red dye aqueous solution and stirred thoroughly. The volume of the aqueous solution required was 1000ml. The mixed solution was frozen at -13°C for 24 hours. At this time, the fiber swelled and twisted, the fiber surface was slightly dissolved, the fresh surface was exposed, and the dye was tightly adsorbed on the fiber surface. After the fiber was taken out of the solution, it was immersed in acetic acid for 50 hours, and then washed with deionized water several times, and then the washed sample was dried. At this time, the sample actively shrank to form a dense structure, and finally the acid-base indicating material was obtained.

[0042] Embodiment 8:

[0043] 10 g of cellulose fiber from cotton was mixed with copper ammonia solution and stirred thoroughly. 0.05 g of Congo red dye was added. The Cu / NH 3 The molar ratio is 0.046 / 0.36, and 50 ml of copper ammonia solution is required. The obtained mixed system is treated for 1 hour, taken out and immersed in 10% NaOH solution for 10 hours. At this time, the fibers are twisted and entangled, the fiber surface is slightly dissolved, and the dye is adsorbed on the fiber surface. After that, it is washed with deionized water several times, and then the washed sample is dried. When drying, the sample actively shrinks to form a dense structure, and finally the acid-base indicating material is obtained.

Claims

1. A reusable acid-base indicating material, comprising a base material and an acid-base indicator material, characterized in that: The matrix material is composed of micron-sized plant fibers tightly wound together, and the acid-base indicator material is attached to the surface of the plant fibers by physical action; the acid-base indicator material is prepared by the following steps: (1) treating the plant fibers with treatment solution A so that the plant fibers are dissolved, the fibers are dispersed with each other and are fully combined with the acid-base indicator material in the treatment solution A; (2) freezing the plant fibers treated in step (1) for 2 to 12 hours to harden the fibers into blocks; (3) treating the fibers of the block material in treatment solution B for 1 minute to 72 hours, and then soaking them in acid or water to wash away chemical residues; (4) The fiber block obtained in step (3) is dried to obtain the reusable acid-base indicating material.

2. A reusable acid-base indicating material according to claim 1, characterized in that: The density of the matrix material is 1.4-1.6 g / cm 3 , the tensile strength is 80-90MPa.

3. A reusable acid-base indicating material according to claim 1, characterized in that: In step (1), the treatment solution A includes a strong alkaline solution, an alkali / urea mixed solution, a lithium chloride / dimethylacetamide solution, an ionic liquid, a cupric ammonia solution or an N-methylmorpholine-N-oxide solution.

4. A reusable acid-base indicating material according to claim 1, characterized in that: In step (1), the acid-base indicator material is a compound having an acid-base indicating effect such as nitrophenol, phenolphthalein, sulfonated phenolphthalein or azo dye.

5. The reusable acid-base indicating material according to claim 1, characterized in that: In step (3), the treatment solution B is hydrochloric acid solution, acetic acid solution, sulfuric acid solution or water, or any safe combination of the above solutions.

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