Preparation method of magnesium-containing soapstone colloid

Abstract

The invention discloses a preparation method of magnesium-containing soapstone colloid, which comprises the following steps: dissolving sodium citrate, sodium bicarbonate and sodium hydroxide in deionized water to prepare alkali liquor; the preparation method comprises the following steps: dissolving magnesium salt and aluminum salt in deionized water to prepare an aqueous solution containing magnesium and aluminum; the preparation method comprises the following steps: dropwise adding water glass into an alkali solution under stirring to obtain a silicon-containing solution, and dropwise adding an aqueous solution containing magnesium and aluminum into the silicon-containing solution to obtain a crystallization solution; adding the obtained crystallization liquid into a crystallization kettle for constant-temperature crystallization to obtain magnesium saponite; the magnesium saponite with the mass fraction of 0.1-2% is swelled, stripped and dispersed in deionized water to obtain stable colloid, the particle size distribution of dispersoid particles in the colloid is unimodal distribution, and the average particle size is smaller than 100 nm.

Description

Technical Field

[0001] The invention relates to a method for preparing a colloid containing magnesium saponite. Background Art

[0002] Magnesium soapstone is a silicate material with a layered structure that is rich in magnesium and contains a small amount of aluminum. Its structural unit layer is composed of two layers of silicon oxygen sheets, namely [SiO4] tetrahedral sheets, sandwiching a layer of magnesium oxygen sheets, namely [MgO6] octahedral sheets. Its structural unit contains rich structural hydroxyl groups Mg-O(OH), and the silicon oxygen sheets and magnesium oxygen sheets are stabilized by coplanar hydrogen bonds. Because some of the central atoms of silicon atoms in the silicon oxygen tetrahedron are replaced by aluminum atoms, the unit cell charge is unbalanced, making the sheets of magnesium soapstone have a permanent negative charge. Therefore, the interlayer (between the structural unit layers) requires positively charged cations such as Na + , K + Mg 2+ To achieve charge balance. + The ideal chemical formula of sodium magnesium soapstone to compensate for the charge balance is Na x [Mg6(Si 8-x Al x )] 20 (OH)4(0.2≤x<1.6). Magnesium soapstone can be widely used in chemical, textile, environment, medicine and other industries due to its small particle size, large specific surface area, interlayer cation exchangeability, excellent expansion and dispersibility.

[0003] Colloid is a dispersion system in which dispersed particles with a particle size between 1-100nm are dispersed in a continuous phase. The smaller the particle size of the dispersed particles of the colloid, the less likely it is that the particles will settle due to Brownian motion. The longer the particles remain in a dispersed and suspended state in the continuous phase, the higher the stability of the colloid. The magnesium soapstone layer has a low charge and is easy to swell and peel in water to form a suspension or colloid. Liu Jie (Synthesis and Rheological Properties of Soapstone, Master's thesis of Zhejiang University of Technology, 2016) synthesized magnesium soapstone according to theoretical layer charges of 0.31, 0.38, 0.50, and 0.73, and prepared a magnesium soapstone water suspension with a mass fraction of 0.2%. The particle size distribution of the dispersed particles in the suspension was measured to be a bimodal distribution. It was found that the magnesium soapstone water suspension contained both a large number of fine particles and relatively few coarse particles. The average particle sizes of the fine particles were 50.9nm, 62.8nm, 68.6nm, and 94.5nm, respectively, which were exfoliated magnesium soapstone flakes, while the average particle size of the coarse particles was 10μm. These coarse particles may be impurities such as magnesium carbonate or magnesium hydroxide. Similarly, the literature (Cunjun Li, Qiqi Wu, Sabine Petit, Will P. Gates, Huimin Yang, Weihua Yu, and Chunhui Zhou, Insights into the Rheological Behavior of Aqueous Dispersions of Synthetic Saponite: Effects of Saponite Composition and Sodium Polyacrylate, Langmuir 2019, 35, 13040-13052) uses a similar preparation method to synthesize magnesium saponite according to a theoretical layer charge of 0.31-0.73, and the average particle size of the particles in the magnesium saponite aqueous suspension with a mass fraction of 1.5% is measured to be 144-171nm. For magnesium saponite aqueous suspensions with dispersed material particles larger than 100nm, Brownian motion easily causes the particles to settle and cannot form a stable colloid.

[0004] Natural magnesium soapstone is not only scarce, but also has many impurities and is difficult to purify. It partially swells and dissolves in water, resulting in incomplete peeling of the soapstone lamellae. At the same time, due to the presence of impurities, the particle size distribution of the impurity particles and the peeled soapstone lamellae particles is uneven, and it is also difficult to obtain a stable colloid. Artificially synthesized magnesium soapstone contains more impurities such as magnesium carbonate and magnesium hydroxide. These impurities exist in amorphous or crystalline forms and cannot be removed by washing during the synthesis process, resulting in poor stability of the prepared colloid or suspension, and even less resistance to acids and electrolytes. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for preparing a colloid containing magnesium soapstone. The method involves organic sodium citrate and an inorganic alkaline buffer solution, and utilizes the oxygen ligand atoms in the citrate ions to form a magnesium citrate complex with a large solubility with magnesium ions, so that more free magnesium ions are gradually dissociated from the crystallization liquid, and the magnesium ions are promoted to enter the magnesium soapstone layer plate; due to the large solubility of the magnesium citrate complex, the excess magnesium ions that have not entered the soapstone layer plate and the interlayer can be removed in the water washing process, so that the magnesium soapstone product is easier to swell, dissolve, peel, and disperse in water to obtain a stable colloid.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a colloid containing magnesium saponite comprises the following steps:

[0008] (1) dissolving sodium citrate, sodium bicarbonate and sodium hydroxide in deionized water to prepare an alkaline solution;

[0009] Preferably, the mass ratio of sodium citrate, sodium bicarbonate, sodium hydroxide and deionized water is 1:2-6:1.8-3.8:24-54;

[0010] (2) mixing aluminum salt, magnesium salt and deionized water to prepare an aqueous solution containing magnesium and aluminum;

[0011] Preferably, the mass ratio of aluminum salt calculated as aluminum, magnesium salt calculated as magnesium, and deionized water is 1:7-18:160-512;

[0012] The aluminum salt is selected from aluminum chloride or aluminum nitrate;

[0013] The magnesium salt is selected from magnesium chloride or magnesium nitrate;

[0014] (3) under stirring, firstly drop water glass into the alkaline solution prepared in step (1) to obtain a silicon-containing liquid; then drop the magnesium and aluminum-containing aqueous solution prepared in step (2) into the silicon-containing liquid to obtain a crystallization liquid;

[0015] Preferably, the mass ratio of aluminum, magnesium and silicon in the obtained crystallization solution is 1:7-18:10-27;

[0016] (4) adding the crystallization solution obtained in step (3) to a crystallization kettle, crystallizing at a constant temperature of 100 to 200° C. for 6 to 24 hours, then cooling to room temperature (20 to 30° C.), centrifuging, washing with water, and drying (60 to 120° C., 6 to 24 hours) to obtain magnesium soapstone;

[0017] (5) adding the magnesium saponite obtained in step (4) to deionized water and stirring evenly to obtain the magnesium saponite-containing colloid;

[0018] In the obtained magnesium soapstone-containing colloid, the mass fraction of magnesium soapstone is 0.1-2%.

[0019] The colloid of magnesium-containing soapstone prepared by the invention has a dispersed substance with a single-peak particle size distribution and an average particle size of less than 100 nm.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The traditional synthesis technology of magnesium soapstone usually involves mixing magnesium ions, aluminum ions, silicon-containing substances, strongly alkaline inorganic sodium hydroxide and sodium bicarbonate buffer and then crystallizing them at high temperature. The mixture of magnesium ions, aluminum ions and strong alkali first generates magnesium hydroxide which is insoluble in water (at 25°C, the solubility product is 5.61×10 -12 ), aluminum hydroxide (at 25°C, solubility product 1.3×10 -33 ), magnesium carbonate (at 25°C, solubility product 6.82×10 -6 ) precipitation, and then these precipitates gradually dissolved in the crystallization, forming ion groups in the form of magnesium ions, aluminum ions and silicon ions to form magnesium soapstone crystal nuclei, which continue to grow, and finally magnesium soapstone with larger grains is obtained.

[0022] Since the added magnesium ions are high in content in the crystallization solution, and magnesium hydroxide and magnesium carbonate are insoluble, it is difficult for all the added magnesium ions to enter the magnesium soapstone layer plate, and part of the magnesium coexists in the crystallization solution in the form of magnesium hydroxide or magnesium carbonate precipitation, which cannot be removed during the washing process. Therefore, the final magnesium soapstone product contains impurity particles such as magnesium carbonate and magnesium hydroxide with larger particle sizes, which makes it impossible to obtain a stable colloid when the magnesium soapstone product is dispersed in water, and the particle size distribution of the dispersed particles is bimodal.

[0023] The preparation method of magnesium soapstone colloid provided by the present invention relates to an organic sodium citrate-inorganic alkaline buffer solution, wherein the oxygen ligand atoms in citrate ions form magnesium citrate complexes with relatively large solubility with magnesium ions, and magnesium citrate gradually dissociates more free magnesium ions in a crystallization solution, thereby promoting more magnesium ions to enter the magnesium soapstone layer plates, and the excess magnesium ions that have not entered the soapstone layer plates and interlayers can be removed in a water washing process, thereby making the magnesium soapstone product more easily swollen, stripped and dispersed in water to obtain a stable colloid, and the particle size distribution of the dispersed material particles in deionized water is unimodal, and the average particle size of the dispersed material particles is less than 100 nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 : Particle size distribution of dispersoid particles in the colloid containing magnesium saponite prepared in Examples 1 to 4. DETAILED DESCRIPTION

[0025] The present invention is further described below by means of specific embodiments, but the protection scope of the present invention is not limited thereto.

[0026] The water glass used in the following examples was purchased from Jiangsu Tongsheng Chemical Reagent Co., Ltd., with a silicon dioxide content of 27% and a sodium hydroxide content of 14%.

[0027] Example 1

[0028] The method for preparing a colloid containing magnesium saponite of the present embodiment comprises the following steps:

[0029] 1) According to the mass ratio of sodium citrate, sodium bicarbonate, sodium hydroxide and deionized water of 1:5.7:3.7:51.2, 1.7 g of sodium citrate, 9.65 g of sodium bicarbonate, 6.25 g of sodium hydroxide and 87 g of deionized water were mixed to prepare an alkaline solution.

[0030] 2) According to the mass ratio of aluminum salt based on aluminum content, magnesium salt based on magnesium content, and deionized water of 1:7.1:166, 2.34 g of aluminum nitrate nonahydrate, 10.15 g of magnesium chloride hexahydrate, and 28 g of deionized water were mixed to prepare an aqueous solution containing magnesium and aluminum.

[0031] 3) Under stirring conditions, first add 13.43 g of water glass to the alkaline solution prepared in step 1) to obtain a silicon-containing liquid, and then add the magnesium and aluminum-containing aqueous solution prepared in step 2) to the silicon-containing liquid to obtain a crystallization liquid, in which the mass ratio of aluminum, magnesium and silicon is 1:7.1:10.

[0032] 4) The crystallization liquid was placed in a crystallization kettle, crystallized at a constant temperature of 130°C for 12 hours, cooled, centrifuged, washed with water, dried at 80°C for 20 hours, crushed, and passed through a 100-mesh sieve to obtain magnesium soapstone. Magnesium soapstone was dispersed in deionized water at a mass fraction of 0.2%, stirred evenly, and the average particle size of the dispersed particles was measured to be 91.3nm.

[0033] Figure 1 (a) is the particle size distribution of the dispersoid particles in the colloid of magnesium-containing saponite prepared in Example 1.

[0034] Example 2

[0035] The method for preparing a colloid containing magnesium saponite of the present embodiment comprises the following steps:

[0036] 1) According to the mass ratio of sodium citrate, sodium bicarbonate, sodium hydroxide and deionized water of 1:4:2.8:39.4, 3.07 g of sodium citrate, 12.27 g of sodium bicarbonate, 8.73 g of sodium hydroxide and 121 g of deionized water were mixed to prepare an alkaline solution.

[0037] 2) According to the mass ratio of aluminum salt based on aluminum content, magnesium salt based on magnesium content, and deionized water of 1:10.7:267, 1.34 g of aluminum chloride hexahydrate, 13.53 g of magnesium chloride hexahydrate, and 40 g of deionized water were mixed to prepare an aqueous solution containing magnesium and aluminum.

[0038] 3) Under stirring conditions, first add 13.43 g of water glass to the alkaline solution prepared in step 1) to obtain a silicon-containing liquid, and then add the magnesium and aluminum-containing aqueous solution prepared in step 2) to the silicon-containing liquid to obtain a crystallization liquid, in which the mass ratio of aluminum, magnesium and silicon is 1:10.7:15.6.

[0039] 4) The crystallization liquid was placed in a crystallization kettle, crystallized at a constant temperature of 140°C for 16 hours, cooled, centrifuged, washed with water, dried at 100°C for 18 hours, crushed, and passed through a 100-mesh sieve to obtain magnesium soapstone. Magnesium soapstone was dispersed in deionized water at a mass fraction of 0.8%, stirred evenly, and the average particle size of the dispersed particles was measured to be 78.8nm.

[0040] Figure 1 (b) is the particle size distribution of the dispersoid particles in the colloid containing magnesium saponite prepared in Example 2.

[0041] Example 3

[0042] The method for preparing a colloid containing magnesium saponite of the present embodiment comprises the following steps:

[0043] 1) According to the mass ratio of sodium citrate, sodium bicarbonate, sodium hydroxide and deionized water of 1:3:2.3:30.5, 5.93g of sodium citrate, 17.78g of sodium bicarbonate, 13.5g of sodium hydroxide and 181g of deionized water were mixed to prepare alkaline solution.

[0044] 2) According to the mass ratio of aluminum salt based on aluminum content, magnesium salt based on magnesium content, and deionized water of 1:14.2:386, 2.34 g of aluminum nitrate nonahydrate, 25.6 g of magnesium nitrate hexahydrate, and 65 g of deionized water were mixed to prepare an aqueous solution containing magnesium and aluminum.

[0045] 3) Under stirring conditions, first add 28.24 g of water glass to the alkaline solution prepared in step 1) to obtain a silicon-containing liquid, and then add the magnesium and aluminum-containing aqueous solution prepared in step 2) to the silicon-containing liquid to obtain a crystallization solution, in which the mass ratio of aluminum, magnesium and silicon is 1:14.2:21.1.

[0046] 4) The crystallization liquid was placed in a crystallization kettle, crystallized at a constant temperature of 160°C for 18 hours, cooled, centrifuged, washed with water, dried at 110°C for 12 hours, crushed, and passed through a 100-mesh sieve to obtain magnesium soapstone. Magnesium soapstone was dispersed in deionized water at a mass fraction of 2%, stirred evenly, and the average particle size of the dispersed particles was measured to be 58.9nm.

[0047] Figure 1 (c) is the particle size distribution of the dispersoid particles in the colloid containing magnesium saponite prepared in Example 3.

[0048] Example 4

[0049] The method for preparing a colloid containing magnesium saponite of the present embodiment comprises the following steps:

[0050] 1) According to the mass ratio of sodium citrate, sodium bicarbonate, sodium hydroxide and deionized water of 1:2.3:1.9:24.4, 12.35 g of sodium citrate, 28.82 g of sodium bicarbonate, 23.5 g of sodium hydroxide and 301 g of deionized water were mixed to prepare an alkaline solution.

[0051] 2) According to the mass ratio of aluminum salt based on aluminum content, magnesium salt based on magnesium content, and deionized water of 1:16.9:485, 2.12 g of aluminum chloride hexahydrate, 42.67 g of magnesium nitrate hexahydrate, and 115 g of deionized water were mixed to prepare an aqueous solution containing magnesium and aluminum.

[0052] 3) Under stirring conditions, 47.43 g of water glass is first added dropwise to the alkaline solution prepared in step 1) to obtain a silicon-containing liquid, and then the aqueous solution containing magnesium and aluminum prepared in step 2) is added dropwise to the silicon-containing liquid to obtain a crystallization liquid, in which the mass ratio of aluminum, magnesium and silicon is 1:16.9:25.2.

[0053] 4) The crystallization liquid was placed in a crystallization kettle and crystallized at a constant temperature of 180°C for 20 hours. After cooling, it was centrifuged, washed with water, dried at 120°C for 10 hours, crushed, and passed through a 100-mesh sieve to obtain magnesium soapstone. Magnesium soapstone was dispersed in deionized water at a mass fraction of 1.5%, stirred evenly, and the average particle size of the dispersed particles was measured to be 52.7nm.

[0054] Figure 1 (d) is the particle size distribution of the dispersoid particles in the colloid containing magnesium saponite prepared in Example 4.

Claims

1. A method for preparing a colloid containing magnesium saponite, characterized in that: The steps include: (1) dissolving sodium citrate, sodium bicarbonate and sodium hydroxide in deionized water to prepare an alkaline solution; (2) mixing aluminum salt, magnesium salt and deionized water to prepare an aqueous solution containing magnesium and aluminum; (3) under stirring, firstly add water glass dropwise into the alkaline solution prepared in step (1) to obtain a silicon-containing liquid; Then, the aqueous solution containing magnesium and aluminum prepared in step (2) is added dropwise to the silicon-containing liquid to obtain a crystallization solution; (4) adding the crystallization solution obtained in step (3) to a crystallization kettle, crystallizing at a constant temperature of 100 to 200° C. for 6 to 24 hours, then cooling to room temperature, centrifuging, washing with water, and drying to obtain magnesium soapstone; (5) Adding the magnesium soapstone obtained in step (4) into deionized water and stirring evenly to obtain the magnesium soapstone-containing colloid.

2. The method for preparing the colloid containing magnesium saponite as claimed in claim 1, characterized in that: In step (1), the mass ratio of sodium citrate, sodium bicarbonate, sodium hydroxide and deionized water is 1:2-6:1.8-3.8:24-54.

3. The method for preparing the colloid containing magnesium saponite as claimed in claim 1, characterized in that: In step (2), the mass ratio of aluminum salt calculated as aluminum, magnesium salt calculated as magnesium, and deionized water is 1:7-18:160-512.

4. The method for preparing the colloid containing magnesium saponite as claimed in claim 1, characterized in that: In step (2), the aluminum salt is selected from aluminum chloride or aluminum nitrate.

5. The method for preparing the colloid containing magnesium saponite as claimed in claim 1, characterized in that: In step (2), the magnesium salt is selected from magnesium chloride or magnesium nitrate.

6. The method for preparing the colloid containing magnesium saponite according to claim 1, characterized in that: In the crystallization solution obtained in step (3), the mass ratio of aluminum, magnesium and silicon is 1:7 to 18:10 to 27.

7. The method for preparing the colloid containing magnesium saponite as claimed in claim 1, characterized in that: In the colloid containing magnesium saponite obtained in step (5), the mass fraction of magnesium saponite is 0.1-2%.

8. The colloid of magnesium-containing saponite obtained by the preparation method according to any one of claims 1 to 7.

9. The colloid containing magnesium saponite as claimed in claim 8, characterized in that: The particle size distribution of the dispersoid is unimodal, and the average particle size is less than 100 nm.

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