阅读说明：本技术 橄榄石低温低压水热合成蛇纹石的方法以及一种蛇纹石 (Method for hydrothermally synthesizing serpentine from olivine at low temperature and low pressure and serpentine ) 是由 孙红娟 周志强 彭同江 刘爱平 于 2021-08-31 设计创作，主要内容包括：本发明提供了一种橄榄石低温低压水热合成蛇纹石的方法以及一种蛇纹石,所述橄榄石低温低压水热合成蛇纹石的方法包括步骤：第一步：将镁橄榄石粉体、活性二氧化硅和第一碱性溶液按预定比例混合,得到混合溶液；第二步：将所述混合溶液在密闭、恒温条件下进行水热反应,得到蛇纹石悬浊液；第三步：将所述蛇纹石悬浊液过滤得到滤饼和滤液,所述滤饼经洗涤、干燥得到蛇纹石粉体。本发明具有合成工艺技术条件易实现、合成方法工序简易、操作方便、合成过程绿色环保、产生的滤液可进行回收利用等优点。(The invention provides a method for synthesizing serpentine by olivine low-temperature low-pressure hydrothermal synthesis and serpentine, and the method for synthesizing serpentine by olivine low-temperature low-pressure hydrothermal synthesis comprises the following steps: the first step is as follows: mixing forsterite powder, active silicon dioxide and a first alkaline solution according to a predetermined proportion to obtain a mixed solution; the second step is that: carrying out hydrothermal reaction on the mixed solution under the conditions of sealing and constant temperature to obtain a serpentine suspension; the third step: and filtering the serpentine turbid liquid to obtain a filter cake and a filtrate, and washing and drying the filter cake to obtain serpentine powder. The method has the advantages of easy realization of technical conditions of the synthesis process, simple and easy working procedures of the synthesis method, convenient operation, green and environment-friendly synthesis process, capability of recycling the generated filtrate and the like.)

1. A method for synthesizing serpentine hydrothermally at low temperature and low pressure by using olivine, is characterized by comprising the following steps:

the first step is as follows: mixing forsterite powder, active silicon dioxide and a first alkaline solution according to a predetermined proportion to obtain a mixed solution;

the second step is that: carrying out hydrothermal reaction on the mixed solution under the conditions of sealing and constant temperature to obtain a serpentine suspension;

the third step: and filtering the serpentine turbid liquid to obtain a filter cake and a filtrate, and washing and drying the filter cake to obtain serpentine powder.

2. The method for the low-temperature low-pressure hydrothermal synthesis of serpentine from olivine according to claim 1, characterized in that the method further comprises the step of adjusting the mixed solution obtained in the first step to a pH of 10 to 13 using a second alkaline solution.

3. The olivine low-temperature low-pressure hydrothermal synthesis method of serpentine according to claim 2, characterized in that the first alkaline solution is sodium metasilicate solution or a mixed solution of NaOH and sodium metasilicate, and the second alkaline solution is NaOH solution.

4. The olivine low-temperature low-pressure hydrothermal synthesis of serpentine according to claim 1, characterized in that the method further comprises a step of returning the filtrate obtained in the third step to the first step for recycling as alkaline solution.

5. The method for synthesizing the serpentine from the olivines at the low temperature and the low pressure through the hydrothermal method according to claim 1, wherein the particle size of the forsterite powder is 50-300 meshes, and the forsterite powder is obtained by drying, crushing and grinding a forsterite raw material.

6. The method for synthesizing serpentine from olivine through low-temperature and low-pressure hydrothermal method according to claim 1, wherein the active silica comprises at least one of sodium metasilicate and water glass, and the sodium metasilicate is obtained by reacting white carbon black with sodium hydroxide.

7. The olivine low-temperature low-pressure hydrothermal synthesis method of serpentine according to claim 1, characterized in that the forsterite powder, the active silica and the alkaline solution are mixed in the following ratio of forsterite powder: 1: 2-4 mol of active silica: and mixing the components in a mol ratio of 1: 2-3.

8. The method for synthesizing serpentine from olivine through low-temperature low-pressure hydrothermal synthesis according to claim 1, wherein the temperature of the hydrothermal reaction is 100-220 ℃, the pressure is 1.4-4.5 MPa, and the time is 5-15 days.

9. Serpentine obtained by the process according to any one of claims 1 to 8.

10. The serpentine according to claim 9, wherein the serpentine is powder with a particle size of 100-300 meshes, and the serpentine powder is in a shape of a sheet or a leaf.

Technical Field

The invention relates to the technical field of development and utilization of non-metallic minerals and preparation of inorganic non-metallic materials, in particular to a method for hydrothermally synthesizing serpentine from olivine at low temperature and low pressure and a serpentine.

Background

Olivine is an island-structured silicate mineral, [ SiO ]₄]The tetrahedron being present in islands, the vertices not being interconnected, each O^2-One side ofWith a Si⁴⁺Connecting, coordinating with other metal ions on the other side to balance electrovalence, wherein Si/O ratio is 1:4, and chemical formula is (Mg, Fe)₂[SiO₄]An orthorhombic system. The crystal form is often short column-shaped, and the aggregate is irregular granular. Such as forsterite, in which the silicon-oxygen monotetrahedra are separated from each other by [ MgO ]₆]Connected in the direction parallel to the c-axis, [ MgO₆]Octahedron are connected in a coplanar mode to form a zigzag chain, [ SiO ]₄]Tetrahedrally covered on [ MgO₆]In the gaps between the octahedral zigzag chains, each of [ SiO ]₄]Tetrahedral body [ MgO₆]The octahedron are separated and distributed in an island shape.

At present, the research on olivine mostly focuses on the aspects of geological causes, life orgasm and the like, and the application of olivine is not researched yet.

Disclosure of Invention

The present invention aims to address at least one of the above-mentioned deficiencies of the prior art. For example, one of the purposes of the invention is to provide a method for synthesizing serpentine from olivine by low-temperature low-pressure hydrothermal synthesis, wherein the method has the advantages of mild reaction conditions, low energy consumption and environmental protection. For another example, another object of the present invention is to provide a serpentine having a wide source of raw materials, excellent properties, and a wide range of applications.

In order to accomplish the above objects, according to one aspect of the present invention, there is provided a method for hydrothermally synthesizing serpentine from olivine at a low temperature and a low pressure, the method comprising the steps of:

the first step is as follows: mixing forsterite powder, active silicon dioxide and a first alkaline solution according to a predetermined proportion to obtain a mixed solution;

the second step is that: carrying out hydrothermal reaction on the mixed solution under the conditions of sealing and constant temperature to obtain a serpentine suspension;

the third step: and filtering the serpentine turbid liquid to obtain a filter cake and a filtrate, and washing and drying the filter cake to obtain serpentine powder.

In an exemplary embodiment of an aspect of the present invention, the method may further include a step of adjusting the mixed solution obtained in the first step to a pH of 10 to 13 using a second alkaline solution.

In one exemplary embodiment of an aspect of the present invention, the first alkaline solution may be a sodium metasilicate solution or a mixed solution of NaOH and sodium metasilicate, and the second alkaline solution may be a NaOH solution.

In an exemplary embodiment of an aspect of the present invention, the method may further include a step of returning the filtrate obtained in the third step to the first step to be recycled as the alkaline solution.

In an exemplary embodiment of an aspect of the present invention, the forsterite powder may have a particle size of 50 to 300 mesh, and the forsterite powder may be obtained by drying, crushing and grinding a forsterite raw material.

In an exemplary embodiment of an aspect of the present invention, the active silica may include at least one of sodium metasilicate, which may be obtained by reacting white carbon black with sodium hydroxide, and water glass.

In one exemplary embodiment of an aspect of the present invention, the forsterite powder, the active silica and the alkaline solution may be mixed as a mixture of forsterite powder: 1: 2-4 mol of active silica: and mixing the components in a mol ratio of 1: 2-3.

In an exemplary embodiment of an aspect of the present invention, the hydrothermal reaction may be performed at a temperature of 100 to 220 ℃, a pressure of 1.4 to 4.5MPa, and a time of 5 to 15 days.

According to a further aspect of the present invention there is provided a serpentine obtainable by a process as defined in any one of the preceding claims.

In an exemplary embodiment of another aspect of the present invention, the serpentine may be a powder with a particle size of 100 to 300 meshes, and the serpentine powder may have a plate shape or a leaf shape.

Compared with the prior art, the beneficial effects of the invention can comprise at least one of the following:

(1) the serpentine powder obtained by the synthesis method does not contain chrysotile serpentine minerals;

(2) the serpentine mineral synthesized by the synthetic method can be applied to lubricants, friction reducers, fuel additives and the like, and has wide application range and high additional value;

(3) the process of the invention is green and environment-friendly, and the generated filtrate and washing liquid can be recycled.

Drawings

FIG. 1 shows a forsterite serpentine mechanization diagram according to an exemplary embodiment of the present invention;

FIG. 2 shows an X-ray diffraction pattern of forsterite according to an exemplary embodiment of the present invention;

FIG. 3 shows an X-ray diffraction pattern corresponding to e-serpentine in FIG. 4;

FIG. 4 shows a scanning electron micrograph of serpentine according to an exemplary embodiment of the invention.

Detailed Description

Hereinafter, the method for synthesizing serpentine hydrothermally at low temperature and low pressure by olivine and a serpentine according to the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments.

FIG. 1 shows a forsterite serpentine mechanization diagram according to an exemplary embodiment of the present invention; FIG. 2 shows an X-ray diffraction pattern of forsterite according to an exemplary embodiment of the present invention; FIG. 3 shows an X-ray diffraction pattern corresponding to e-serpentine in FIG. 4; FIG. 4 shows a scanning electron micrograph of serpentine according to an exemplary embodiment of the invention.

In a first exemplary embodiment of the present invention, a method for the low-temperature, low-pressure hydrothermal synthesis of serpentine from olivine comprises the steps of:

the first step is as follows: mixing the forsterite powder, the active silicon dioxide and the first alkaline solution according to a preset proportion to obtain a mixed solution. For example, the forsterite powder, the active silica and the alkaline solution may be mixed as a forsterite powder: 1: 2-4 mol of active silica: and mixing the components in a mol ratio of 1: 2-3. For example, the mass ratio of solids to liquid may be 1 g: 2.5 g. Specifically, forsterite powder, active silica and a first alkaline solution are added into a hydrothermal high-pressure reaction kettle in proportion and mixed uniformly to obtain a mixed solution. For example, olivine powder is placed under high pressureReacting in a kettle, adding active SiO₂Dissolving in the first alkaline solution to obtain active SiO₂Adding the solution into a reaction kettle while stirring and adding active SiO₂And (3) solution. The first alkaline solution may be a sodium metasilicate solution or a mixed solution of NaOH and sodium metasilicate.

The second step is that: and carrying out hydrothermal reaction on the mixed solution under the conditions of sealing and constant temperature to obtain a serpentine suspension. For example, the hydrothermal reaction may be carried out at a temperature of 100 to 220 ℃, under a pressure (i.e., saturated water vapor pressure) of 1.4 to 4.5MPa, and for a period of 5 to 15 days. Specifically, the hydrothermal reaction kettle in the first step is sealed, stirred and heated to 100-220 ℃, for example, 200 ℃; reacting at constant temperature for 5-15 days, for example, 10 days, to obtain serpentine suspension.

The third step: and filtering the serpentine turbid liquid to obtain a filter cake and a filtrate, and washing and drying the filter cake to obtain serpentine powder. Specifically, filtering the serpentine turbid liquid to obtain a filter cake and a filtrate, washing the filter cake until the pH value is 7-10, and drying and grinding (the drying and grinding degree is determined according to actual requirements) to obtain the serpentine product.

In the exemplary embodiment, the method may further include a step of adjusting the mixed solution obtained in the first step to a pH of 10 to 13 using a second alkaline solution. The second alkaline solution may be a NaOH solution, such as a 0.5mol/L NaOH solution, which does not undergo substitution reactions with the metal cations in the forsterite starting material.

In the present exemplary embodiment, the method may further include a step of returning the filtrate obtained in the third step and the washing liquid of the filter cake to the first step to be recycled as the alkaline solution. And the filtrate and the washing liquid are recycled, so that the discharge of waste liquid is reduced, and the environmental protection problem is avoided.

In the exemplary embodiment, the forsterite powder may have a particle size of 50 to 300 meshes, and the forsterite powder may be obtained by drying, crushing and grinding a forsterite raw material. Here, forsterite used in the process is produced from scarlet rock, whose main chemical composition is MgO and SiO₂。

In the present exemplary embodiment, the active silica may include at least one of sodium metasilicate and water glass. For example, the sodium metasilicate can be obtained by reacting white carbon black with sodium hydroxide.

In a second exemplary embodiment of the present invention, the serpentine can be obtained by the synthesis method described in the first exemplary embodiment above. For example, the serpentine can be powder with the granularity of 100-300 meshes, and the serpentine powder can be in a sheet shape or a leaf shape.

The principle of the conversion of olivine to serpentine according to the invention is as follows:

SiO₂+NaOH_(aq)＝Na₂SiO₃ (1～1)

Mg₂SiO₄+2NaOH+H₂O＝2Mg(OH)₂+Na₂SiO₃ (1～2)

3Mg(OH)₂+3Na₂SiO₃+H₂O＝Mg₃Si₂O₅(OH)+NaOH (1～3)

3Mg₂SiO₄+4H₂O+SiO_2(aq)＝2Mg₃Si₂O₅(OH)₄ (1～4)

2Mg₂SiO₄+3H₂O＝Mg₃Si₂O₅(OH)₄+Mg(OH)₂ (1～5)

wherein the formula (1-1) shows that in the reaction process, amorphous SiO₂Under alkaline condition, the reaction first generates metasilicate ions, namely, silicon-oxygen tetrahedron is formed. The formula (1-2) shows that magnesium hydroxide (i.e., portonite) and metasilicate ions are formed by dissolving forsterite under alkaline conditions. The formulas (1-3) represent the combination of silicon-oxygen tetrahedrons with magnesium hydroxide octahedrons under alkaline conditions, where the metasilicate ion comes from the active SiO in solution₂Dissolution and dissolution of forsterite. The formulae (1 to 4) are the general reaction formulae of the formulae (1 to 1), (1 to 2) and (1 to 3). The formula (1-5) shows that under an alkaline condition, under a proper condition, spontaneously decomposed ions are recombined to form the serpentine after the forsterite is dissolved. The above mechanism of the conversion of forsterite into serpentine can be shown in fig. 1.

For a better understanding of the present invention, the following further illustrates the present invention with reference to specific examples, but the present invention is not limited to the following examples.

(1) Washing forsterite particles with deionized water, drying the forsterite particles with a 100 ℃ oven, and selecting the particles with good crystallization and no impurities under an optical microscope;

(2) and knocking the selected sample particles into fine particles by using a geological hammer, then placing the fine particles into an agate mortar, repeatedly grinding and sieving, and collecting 300-mesh sample powder for later use. FIG. 2 shows an X-ray diffraction pattern of the forsterite powder, and it can be seen from FIG. 2 that the forsterite powder has a high purity and a crystal structure of a forsterite crystal phase. Here, the abscissa 2 θ (°) represents twice the incident angle of x-rays, and the ordinate Intensity (a.u) represents the Intensity after diffraction. The chemical composition of forsterite is given in table 1;

TABLE 1 chemical composition of forsterite

Wherein, Fe₂O₃ ^TRepresents total iron, including FeO and Fe₂O₃

(3) Preparing 0.5mol/ml NaOH solution in a 500ml volumetric flask for adjusting pH;

(4) according to the chemical reaction process of converting forsterite into serpentine, 4.2g of 300-mesh forsterite powder and 0.6g of nano SiO₂Sequentially adding the mixture into a 150ml polytetrafluoroethylene high-pressure reaction tank;

(5) adding a proper amount of deionized water into a polytetrafluoroethylene inner container, stirring uniformly by using a magnetic stirrer, dropwise adding a NaOH solution, measuring the pH value of supernatant in a reaction container by using an acidimeter, and adjusting the pH value in a system to a designed value (the specific reaction conditions are given in Table 2); and the volume of the solution is kept to be 2/3 of the total volume of the polytetrafluoroethylene liner;

(6) putting the polytetrafluoroethylene inner container into a stainless steel metal outer sleeve, sealing, placing the stainless steel metal outer sleeve in a drying oven for constant-temperature reaction time at a preset temperature, and taking the polytetrafluoroethylene inner container out of the reaction tank in different reaction time;

(7) and after the reaction tank is naturally cooled, transferring the sample out, filtering, storing the solution in a 10ml centrifuge tube, and drying the solid product in an oven at 100 ℃ for 14 hours for later analysis and test.

TABLE 2 serpentine prepared under different reaction conditions

As can be seen from Table 2 and FIG. 4, the morphology of the samples from olivine to serpentine was significantly different at different reaction temperatures, times and pH values. Fig. 4 a shows olivine particles with a relatively flat and smooth surface, fig. 4 b, c, d and e show SEM pictures of samples transformed at 200 ℃ and pH 13 for 5, 10, 15 and 20 days, respectively, and fig. 4 f shows SEM pictures of samples transformed at 100 ℃ and pH 12 for 20 days. As can be seen from B, c, d and e in FIG. 4, the original relatively flat surface of the olivine particles formed a thin layer of distinct plate-like, leaf-like serpentine product as the reaction time increased. And the crystal profile of the sample becomes clearer and clearer. After 20 days of reaction, the formation of flaky and foliated serpentine was clearly seen. From f in fig. 4, it can be seen that a serpentine product with a small particle size and irregularity is formed only on the serpentine surface after 20 days of reaction at a pH of 12 and 100 ℃. As can be seen from e and f in FIG. 4, the increase in reaction temperature and pH is advantageous for the growth of serpentine crystals. FIG. 3 shows an X-ray diffraction pattern corresponding to e-serpentine in FIG. 4, from which FIG. 3 it can be seen that the major crystalline phases in the resulting serpentine are forsterite, serpentine and brucite (magnesium hydroxide).

It can be known from the comparison of forsterite raw ore and serpentine product that the basic condition is favorable for converting forsterite into serpentine, and it can be known from the comparison of e and f in fig. 4 that the serpentine product has better crystallinity and clearer contour at pH 13 compared with the pH 12 serpentine product; at low alkalinity, the serpentine produced is in a porous network. In general, the complete transformation of forsterite requires a certain temperature, pressure, fluid conditions and reaction time, and is a slow dissolution and recrystallization process.

In summary, the beneficial effects of the invention can include at least one of the following:

(1) the serpentine powder obtained by the synthesis method does not contain chrysotile serpentine minerals;

(2) the serpentine mineral synthesized by the synthetic method can be applied to lubricants, friction reducers, fuel additives and the like, and has wide application range and high additional value;

(3) the process of the invention is green and environment-friendly, and the generated filtrate and washing liquid can be recycled.

While the present invention has been described above in connection with the accompanying drawings and exemplary embodiments, it will be apparent to those of ordinary skill in the art that various modifications may be made to the above-described embodiments without departing from the spirit and scope of the claims.