Mineral materials for oil-water separation, their preparation methods and applications

Abstract

This invention provides a mineral material for oil-water separation, its preparation method, and its application. The mineral material comprises α-CaSO4·0.5H2O, and its crystal form is detected using Cu-Kα radiation. It has (110), (020), (400), and (204) crystal planes, with a relative intensity ratio of (204) to (110) crystal planes of (0.03–0.35):1. Because the (204) crystal plane has an oil-water separation function, it can rapidly fix trace amounts of water in the emulsion into the gypsum lattice, ultimately achieving efficient, rapid, and stable oil-water separation through low-speed centrifugation. The preparation method uses industrial by-product gypsum as raw material, and through controlled directional crystallization, prepares a high-efficiency oil-water separation material at low cost. The reaction conditions are mild and environmentally friendly, with low cost, high yield, and high product purity, providing a reference for the high-value utilization of by-product gypsum and reducing the water content of crude oil.

Description

Technical Field

[0001] This invention belongs to the field of mineral material application technology, specifically relating to mineral materials for oil-water separation, their preparation methods, and applications. Background Technology

[0002] Crude oil extracted from wells generally contains a certain amount of water. Excessive water content in crude oil leads to waste in storage and transportation, increases equipment requirements, and higher energy consumption. During oil refining, when water and crude oil are heated together, the water rapidly vaporizes and expands, increasing pressure and affecting normal refinery operations and product quality; it can even cause explosions. Therefore, crude oil must be dehydrated before export to ensure a water content of no more than 0.5%. Separating oil-water mixtures is, in principle, based on the differences in physical properties such as density and boiling point between oil and water. Common methods include heating, flotation, magnetic separation, electro / chemical coalescence, membrane filtration, and centrifugation. However, these traditional technologies are energy-intensive and costly, and are only effective for separating oil-water mixtures; they are less effective for separating water-in-oil emulsions with small droplets, high viscosity, and high stability. Previous studies have demonstrated that various novel special membranes can efficiently separate water-in-oil emulsions. However, in practical applications of filtration technology, membrane antifouling, scale buildup, and flux issues can lead to decreased separation efficiency. Furthermore, as water droplet size decreases and oil viscosity increases, the efficiency of membrane technology for separating water-in-oil emulsions becomes even lower. Unlike membrane separation technology, solid particulate water adsorbents, while capable of continuous emulsion separation and effectively avoiding problems such as poor membrane durability and fouling, still face technical bottlenecks such as high preparation costs and relatively poor adsorption effects. Existing research indicates that α-type hemihydrate gypsum (α-CaSO4·0.5H2O) is an unstable phase at temperatures ranging from 0 to 200°C, readily reacting with water to revert to CaSO4·2H2O at lower temperatures. Due to its abundant raw materials, low cost, and ease of separation and recovery, and utilizing its excellent water absorption and crystallization properties, it shows great potential in low-cost, green oil-water emulsion demulsification and trace water removal.

[0003] Industrial by-product gypsum, primarily composed of calcium sulfate dihydrate, is a byproduct discharged during industrial production. Due to its complex composition of impurities, its resource utilization is difficult, and long-term stockpiling can easily cause environmental pollution, making it a significant factor restricting the sustainable development of related industries. Depending on the production process and impurities, it is mainly classified into desulfurized gypsum, phosphogypsum, titanium gypsum, fluorogypsum, and salt gypsum. The main resource utilization pathways for by-product gypsum include building materials, cementitious materials, and ecological restoration, but these generally suffer from low added value, severely hindering its large-scale and high-value application. Therefore, developing high-value-added products using by-product gypsum as a raw material is crucial for its resource utilization and large-scale application.

[0004] However, there are currently few reports on the use of by-product gypsum to prepare oil-water separation materials. Furthermore, in existing processes for preparing α-CaSO4·0.5H2O by gypsum crystallization, the types of crystallization agents are complex, and precise crystallization technology for preparing high-efficiency oil-water separation materials is lacking, resulting in low dehydration efficiency of the obtained α-CaSO4·0.5H2O. Summary of the Invention

[0005] The purpose of this invention is to address the above-mentioned shortcomings of the prior art by providing mineral materials for oil-water separation, their preparation methods, and applications.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first objective of this invention is to provide a mineral material for oil-water separation, the mineral material comprising α-CaSO4·0.5H2O, wherein the crystal form of the α-CaSO4·0.5H2O is detected using Cu-Kα radiation, and X-ray powder diffraction, expressed in terms of 2θ angle and interplanar spacing, shows characteristic absorption peaks at 14.7°±0.2°, 25.6°±0.2°, 29.7°±0.2° and 31.9°±0.2°, corresponding to the (110) crystal plane, (020) crystal plane, (400) crystal plane and (204) crystal plane, respectively, wherein the relative intensity ratio of the (204) crystal plane to the (110) crystal plane is (0.03~0.35):1.

[0008] Furthermore, the α-CaSO4·0.5H2O crystals are rod-shaped, each rod having a diameter of 1–4 μm, a length of 20–50 μm, and an aspect ratio of 5–25.

[0009] A second objective of this invention is to provide a method for preparing the aforementioned mineral material for oil-water separation, comprising the following specific steps:

[0010] S1. Dissolve the crystal-changing agent Na2SO4 in a solvent and stir thoroughly to obtain a crystal-changing conditioning solution;

[0011] S2. Add the by-product gypsum to the crystallization conditioning solution in step S1 to obtain the first slurry. After thorough stirring, place it under a constant temperature bar for a certain period of time to obtain the second slurry. The purity of CaSO4·2H2O in the by-product gypsum is not less than 60%.

[0012] S3. After filtering, washing, drying and ultra-fine pulverizing the second slurry obtained in step S2, a mineral material for oil-water separation is obtained.

[0013] Furthermore, in step S1, the solvent is any one or more of distilled water, ethylene glycol, glycerol, and isopropanol.

[0014] Furthermore, in step S2, the by-product gypsum is any one or more of desulfurized gypsum, phosphogypsum, fluorogypsum, titanium gypsum, and salt gypsum.

[0015] Furthermore, the mass ratio of the crystallizing agent to the by-product gypsum is (5-20):10.

[0016] Furthermore, in step S2, the reaction temperature is 25-150℃ and the reaction time is 0.5-8.0h.

[0017] The third objective of this invention is to provide a method for demulsifying and separating oil and water using the aforementioned mineral materials. The mineral materials are added to an oil-water emulsion, stirred and mixed evenly, allowed to settle naturally, and then separated by low-speed centrifugation.

[0018] Furthermore, the mass ratio of the mineral material to the volume ratio of water in the oil-water emulsion is 1:(5-1000).

[0019] Furthermore, the oil-water emulsion is a mixed solution containing an aqueous phase, an oil phase, and a surfactant. The aqueous phase accounts for no more than 2% of the total mass. The oil phase includes any one or more of transformer oil, vacuum pump oil, lubricating oil, gasoline, and kerosene. The surfactant includes any one of SP80, SP60, TGI, and PGPH.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] (1) The present invention provides a mineral material for oil-water separation. The mineral material contains α-CaSO4·0.5H2O. Using Cu-Kα radiation, X-ray powder diffraction, expressed in terms of 2θ angle and interplanar spacing, shows characteristic absorption peaks at 14.7°±0.2°, 25.6°±0.2°, 29.7°±0.2°, and 31.9°±0.2°, corresponding to the (110), (020), (400), and (204) crystal planes, respectively. The relative intensity ratio of the (204) crystal plane to the (110) crystal plane is (0.03~0.35):1. Because the (204) crystal plane has the function of oil-water separation, it can quickly fix trace amounts of water in the emulsion into the gypsum lattice, and finally achieve efficient, rapid, and stable oil-water separation by low-speed centrifugation.

[0022] (2) The present invention provides a method for preparing mineral materials for oil-water separation. Using industrial by-product gypsum as raw material, a high-efficiency oil-water separation material is prepared at low cost through controllable directional crystallization. The reaction conditions are mild and green, the cost is low, the yield is high, and the product purity is high. This provides a reference for the high-value utilization of by-product gypsum and the reduction of crude oil water content.

[0023] (3) The mineral material for oil-water separation provided by this invention exhibits extremely high separation efficiency in demulsification and oil-water separation applications by utilizing the spontaneous hydration reaction of α-CaSO4·0.5H2O crystals. It is simple to operate, low in cost, green and non-toxic, and can be recycled. It can be widely used for crude oil dehydration, which increases the added value of by-product gypsum products and greatly promotes the resource utilization of by-product gypsum.

[0024] (4) The demulsification and oil-water separation method provided by the present invention is easy to operate, has high separation efficiency, and high added value. Attached Figure Description

[0025] Figure 1 XRD overlay images of the mineral materials α-CaSO4·0.5H2O prepared in Examples 1-3;

[0026] Figure 2a and 2b The images are scanning electron microscope (SEM) images of the by-product gypsum before and after crystallization in Example 2.

[0027] Figure 3 Statistical charts showing the aspect ratios of α-CaSO4·0.5H2O prepared in Examples 1-3;

[0028] Figure 4 The graph shows the particle size distribution results of α-CaSO4·0.5H2O prepared in Examples 1-3.

[0029] Figure 5 The graph shows the specific surface area test results of α-CaSO4·0.5H2O prepared in Examples 1-3;

[0030] Figure 6 The images show the unseparated emulsions and the oil-water separated emulsions of α-CaSO4·0.5H2O prepared in Examples 1-3, and their dispersion diagrams under an optical microscope.

[0031] Figure 7 The image shows the results of circulating oil-water separation of the mineral material α-CaSO4·0.5H2O prepared in Example 3.

[0032] Figure 8 The image shows a comparison of the separation of a water-in-oil emulsion with high viscosity before and after using the mineral material α-CaSO4·0.5H2O prepared in Example 3. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer, embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0034] The by-product gypsum used in the examples comes from the wet-process phosphoric acid production of a chemical plant in Hubei Province. The content of CaSO4·2H2O is not less than 98%.

[0035] Example 1

[0036] This embodiment provides a method for preparing mineral materials for oil-water separation.

[0037] The specific steps are as follows:

[0038] Step S1: Add 10g of by-product gypsum to 50mL of deionized water, stir and sonicate for 15min each to prepare a suspension.

[0039] Step S2: The suspension was subjected to hydrothermal reaction at 120℃ for 8 hours. After the reaction was completed, the solution was rapidly filtered and washed repeatedly with hot water and anhydrous ethanol. The filtered solid was collected and dried at 80℃ to obtain the mineral material α-CaSO4·0.5H2O.

[0040] Example 2

[0041] This embodiment provides a method for preparing mineral materials for oil-water separation.

[0042] Step S1: Place 6.4g of anhydrous Na2SO4 in 50mL of deionized water and stir to dissolve at room temperature to prepare Na2SO4 solution.

[0043] Step S2: Add 10g of by-product gypsum to the above Na2SO4 solution, place it in a constant temperature water bath at 98℃ and stir for 8h. After the reaction is completed, quickly filter the obtained solution and wash it multiple times with hot water and anhydrous ethanol. Collect the filtered solid and dry it at 80℃ to obtain the mineral material α-CaSO4·0.5H2O.

[0044] Example 3

[0045] This embodiment provides a method for preparing mineral materials for oil-water separation.

[0046] Step S1: Place 10.6g of anhydrous Na2SO4 in 50mL of deionized water and stir to dissolve at room temperature to prepare Na2SO4 solution.

[0047] Step S2: Add 10g of by-product gypsum to the above Na2SO4 solution, place it in a constant temperature water bath at 98℃ and stir for 8h. After the reaction is completed, quickly filter the obtained solution and wash it repeatedly with hot water and anhydrous ethanol. Collect the filtered solid and dry it at 80℃ to obtain the mineral material α-CaSO4·0.5H2O.

[0048] refer to Figure 1 The XRD superposition diagram of the mineral material α-CaSO4·0.5H2O prepared in Examples 1-3 is shown. The characteristic peaks match the PDF standard card of #01-083-0439, indicating that the obtained product is hemihydrate gypsum and no impurity peaks appear. This shows that the hemihydrate gypsum obtained by the by-product gypsum crystallization method provided by the present invention has high purity. Using Cu-Kα radiation, X-ray powder diffraction in terms of 2θ angle and interplanar spacing shows characteristic absorption peaks at 14.7°±0.2°, 25.7°±0.2°, 29.7°±0.2° and 31.9°±0.2°, respectively, corresponding to the (110) crystal plane, (020) crystal plane, (400) crystal plane and (204) crystal plane.

[0049] In the mineral material prepared in Example 1, the peak intensity of the (020) crystal face relative to the (110) crystal face was 32.0%, the peak intensity of the (400) crystal face relative to the (110) crystal face was 93.0%, and the peak intensity of the 204 crystal face relative to the (110) crystal face was 3.6%. In the mineral material prepared in Example 2, the peak intensity of the (020) crystal face relative to the (110) crystal face was 23.6%, and the peak intensity of the (400) crystal face relative to the (110) crystal face was 7%. 6.5%, the peak intensity of the (204) crystal plane relative to the (110) crystal plane is 15.4%; in the mineral material prepared in Example 3, the peak intensity of the (020) crystal plane relative to the (110) crystal plane is 33.6%, the peak intensity of the (400) crystal plane relative to the (110) crystal plane is 95.0%, and the peak intensity of the (204) crystal plane relative to the (110) crystal plane is 34.2%; as can be seen from the figure, the relative intensity value of the (204) crystal plane shows an increasing trend.

[0050] refer to Figure 2a and 2b The images shown are scanning electron microscope (SEM) images of the by-product gypsum before and after crystallization in Example 2. It can be seen that before crystallization, the by-product gypsum is mainly in the form of two-dimensional flakes, while after crystallization, it is mainly in the form of rods. The diameter is mainly between 1 and 4 μm, the length is mainly between 20 and 50 μm, and the aspect ratio is mainly between 10 and 25.

[0051] refer to Figure 3 The figure shows the aspect ratio of α-CaSO4·0.5H2O prepared in Examples 1 to 3. As can be seen from the figure, the α-CaSO4·0.5H2O crystal prepared in Example 3 has the largest aspect ratio. The aspect ratios of the three crystals are significantly different, and the crystal forms have undergone important changes.

[0052] refer to Figure 4 and Figure 5 The figures show the particle size and specific surface area test results of α-CaSO4·0.5H2O prepared in Examples 1 to 3, respectively. The particle size distribution of the preparation in Example 1 is D. 10 64.7μm, D 50 116.2μm, D 90 The particle size distribution was 187.3 μm; the particle size distribution prepared in Example 2 was D. 10 68.1μm, D 50 123.3μm, D 90 The particle size distribution was 213.6 μm; the particle size distribution prepared in Example 3 was D. 10 68.3μm, D 50 120.2μm, D 90 The particle size was 199.9 μm. As shown in the figure, the particle size difference among the three is not significant, but the α-CaSO4·0.5H2O prepared in Example 1 clearly has a larger specific surface area, followed by Example 2. A larger specific surface area is more advantageous for interfacial reactions. This also proves that the crystal form changed in the examples.

[0053] To better illustrate the performance and application effects of the mineral material for oil-water separation provided by this invention, the applicant has conducted the following research:

[0054] Example 4

[0055] This embodiment provides a method for demulsification and oil-water separation using mineral materials provided by the present invention.

[0056] The oil-water emulsion used in this embodiment is prepared by mixing water, industrial 25# transformer oil, surfactant Sp80 = 0.7g, 100mL, and 0.1g, and stirring vigorously for more than 16 hours.

[0057] The specific steps for demulsification and oil-water separation are as follows:

[0058] Step S1: Take 1.00g of α-CaSO4·0.5H2O prepared in Examples 1 to 3 and add it to 20mL of oil-water emulsion respectively. Stir at room temperature for 15-45min to fully mix the system.

[0059] Step S2: Stop stirring the above mixture, let it stand and centrifuge at a speed of 2000-5000 rpm for 2-10 minutes, depending on the viscosity and type of oil.

[0060] Step S3: After centrifugation, the solid and liquid are separated. The solid is repeatedly washed with detergent and then dried for recovery. The detergent can be an organic solvent such as n-hexane, cyclohexane, or acetone.

[0061] refer to Figure 6 The images show the unseparated emulsions and the oil-water emulsions prepared by α-CaSO4·0.5H2O in Examples 1-3 after oil-water separation, as well as their dispersion diagrams under an optical microscope. As can be seen from the figures, the turbidity of the oil-water emulsions after separation by α-CaSO4·0.5H2O changes significantly. The fine water droplets in the emulsion before separation are also reduced to varying degrees after separation. The emulsion prepared by α-CaSO4·0.5H2O in Example 3 is the clearest after oil-water separation, and there are almost no obvious water droplets.

[0062] Moisture analysis was performed using a Karl Fischer moisture analyzer, and the results are shown in Table 1. It is evident that the moisture content of the emulsion was significantly reduced by treatment with α-CaSO4·0.5H2O, decreasing from the initial 6420 ppm to 1584.67, 246.67, and 6.67 ppm, respectively. The highest separation efficiency was achieved with α-CaSO4·0.5H2O prepared in Example 3, reaching 99.90%.

[0063] Table 1. Water content and separation efficiency of the original emulsion and the treated emulsions of Examples 1-3.

[0064]

[0065] Based on the above data, it can be found that the α-CaSO4·0.5H2O prepared in Example 3 has a larger specific surface area, resulting in better oil-water separation. The oil-water separation effect of α-CaSO4·0.5H2O is closely related to its crystal form.

[0066] In some embodiments, the solid separated in Example 4 is used to replace the by-product gypsum material in the preparation of mineral material α-CaSO4·0.5H2O, and the resulting α-CaSO4·0.5H2O still has a high oil-water separation efficiency.

[0067] refer to Figure 7 The figure shows the results of oil-water separation in the cyclic process of the mineral material α-CaSO4·0.5H2O prepared in Example 3. After four cycles, it still has a high oil-water separation effect, indicating that the mineral material provided by the present invention has recyclable characteristics and can be recycled multiple times.

[0068] In some embodiments, the mineral materials provided by the present invention also have a good separation effect on water-in-oil emulsions with high viscosity for industrial mechanical pumps.

[0069] refer to Figure 8The image shows a comparison of the mineral material α-CaSO4·0.5H2O prepared in Example 3 before and after separation of a water-in-oil emulsion with high viscosity. It is easy to see that after oil-water separation, the emulsion transmittance is significantly improved and the water content is low.

[0070] In summary, the technology and equipment provided by this invention for selectively transforming by-product gypsum to prepare α-CaSO4·0.5H2O crystals are simple to implement, require low-level equipment, and have a large specific surface area. Furthermore, utilizing the crystal facet effect of α-CaSO4·0.5H2O can improve the oil-water separation efficiency of the material, and it possesses wide applicability and good recyclability, realizing the high-value utilization of by-product gypsum. This technology has significant application potential and guiding significance.

[0071] For any points not covered above, existing technologies shall apply.

[0072] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a mineral material for oil-water separation, characterized in that, The mineral material comprises α-CaSO4·0.5H2O. The crystal form of the α-CaSO4·0.5H2O is detected using Cu-Kα radiation. X-ray powder diffraction, expressed in terms of 2θ angle and interplanar spacing, shows characteristic absorption peaks at 14.7°±0.2°, 25.7°±0.2°, 29.7°±0.2°, and 31.9°±0.2°, corresponding to the (110), (020), (400), and (204) crystal planes, respectively. The relative intensity ratio of the (204) crystal plane to the (110) crystal plane is 0.

342. The preparation method includes the following specific steps: S1. Dissolve 10.6 g of crystal-changing agent Na2SO4 in deionized water and stir thoroughly to obtain a crystal-changing conditioning solution; S2. Add 10g of by-product gypsum to the crystallization conditioning solution in step S1 to obtain the first slurry. After stirring thoroughly, place it under constant temperature conditions for a certain time to obtain the second slurry. The by-product gypsum is a by-product gypsum produced by the wet process of phosphoric acid, and its content is not less than 98% as CaSO4·2H2O. The reaction temperature is 98℃ and the reaction time is 8h. S3. After filtering, washing, drying and ultra-fine pulverizing the second slurry obtained in step S2, a mineral material for oil-water separation is obtained.

2. A mineral material for oil-water separation prepared by the preparation method described in claim 1.

3. The mineral material as described in claim 2, characterized in that, The α-CaSO4·0.5H2O crystals are rod-shaped, with each rod having a diameter of 1~4μm, a length of 20~50μm, and an aspect ratio of 5~25.

4. A method for demulsifying and separating oil and water using the mineral material as described in claim 2 or 3, characterized in that, The mineral material is added to the oil-water emulsion, stirred and mixed evenly, and after natural sedimentation, the oil and water are separated by low-speed centrifugation.

5. The method as described in claim 4, characterized in that, The oil-water emulsion is a mixed solution containing an aqueous phase, an oil phase, and a surfactant. The aqueous phase accounts for no more than 2% of the total mass. The oil phase includes any one or more of transformer oil, vacuum pump oil, lubricating oil, gasoline, and kerosene. The surfactant includes any one of SP80 and SP60.

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