Selenite soap-based microemulsion as well as preparation method and application thereof

Abstract

The invention provides a preparation method of a seleninic acid soap-based microemulsion capable of being infinitely diluted by water, which comprises the following steps of: efficiently emulsifying various liquid oil by taking organic sodium selenite soap as a main emulsifier, fatty alcohol as a co-emulsifier and a composition of the organic sodium selenite soap and the fatty alcohol as an emulsifier to obtain the seleninic acid soap-based microemulsion by a simple preparation method; the obtained seleninic acid soap-based microemulsion can be infinitely diluted by water, and the obtained seleninic acid soap-based microemulsion is low in emulsifier content, good in solubilizing performance and high in stability. The invention further provides a imperative demulsification method of the seleninic acid soap-based microemulsion capable of being infinitely diluted by water, imperative demulsification of the seleninic acid soap-based microemulsion can be realized by changing the pH value of the seleninic acid soap-based microemulsion, a one-solid two-liquid three-phase system is obtained, high-efficiency recovery of organic seleninic acid is realized, and meanwhile, the pH value of the seleninic acid soap-based microemulsion is changed. And the chemical oxygen demand of the residual water phase treated by the activated carbon and the anion exchange resin is extremely low.

Description

Technical Field

[0001] This invention belongs to the field of specialty chemicals technology, specifically relating to a selenite soap-based microemulsion, its preparation method, and its application. Background Technology

[0002] Microemulsions are transparent and thermodynamically stable systems formed by emulsifiers, immiscible oil and water phases, and can be classified into three types: water-in-oil (W / O), bicontinuous (BC), and oil-in-water (O / W). The dispersed oil or water droplets in microemulsions range in size from several nanometers to tens of nanometers, making them suitable for solubilizing substances with rigid molecular structures and large dimensions. Furthermore, microemulsions contain both polar and non-polar microregions, allowing them to solubilize both polar and non-polar substances. Therefore, microemulsions hold significant promise for applications in hydrophobic solubilization, drug carriers, high-efficiency cleaning agents, and microreactors. However, a prominent challenge in constructing microemulsions is the high required amount of emulsifier, typically no less than 10% of the total mass, which makes demulsification extremely difficult. To address this, previous literature (Adv. Mater. 2000, 12: 1751-1757; ACS Sustain. Chem. Eng. 2015, 3: 443-450) proposed constructing microemulsions using the minimum amount of emulsifier possible, specifically through two methods: First, using a combination of ultra-long-chain branched alkylbenzene sulfonate sodium ULABS and diethylene glycol hexyl ether (DGHE) as the emulsifier (Adv. Mater. 2000, 12: 1751-1757). However, a significant problem with this technique is the extremely poor biodegradability of ULABS, with a half-life of up to 89.7 years in the natural environment. Second, using a combination of saturated and unsaturated mineral oils as the oil phase (ACS Sustain. Chem. Eng. 2015, 3: 443-450). However, a significant problem with this technique is that the required amount of emulsifier is still as high as 30% of the total mass of the microemulsion. Microemulsions that can be infinitely diluted with water (Colloid Surface A. 2014, 442: 105-110) reduce the overall concentration of organic species in the microemulsion, and thus also reduce the content of emulsifiers, but they cannot achieve forced demulsification. Furthermore, while there are reports in the literature of soap-based microemulsions such as sulfuric acid soaps, sulfonic acid soaps, betaine, and carboxylic acid soaps, no publicly available data has been disclosed regarding selenite-based microemulsions. Summary of the Invention

[0003] The purpose of this invention is to address the current technical deficiencies such as "no publicly available information has been disclosed on selenite soap-based microemulsions", "the amount of emulsifier required to form microemulsions is too high", and "microemulsions cannot be demulsified by command", and to provide a selenite soap-based microemulsion that can be infinitely diluted with water and its preparation method.

[0004] Technical solution: A selenite soap-based microemulsion, wherein the microemulsion is composed of an aqueous phase, an oil phase and an emulsifier, wherein the emulsifier is composed of a main emulsifier, organic sodium selenite soap and an auxiliary agent, fatty alcohol.

[0005] Furthermore, the organic sodium selenite soap is sodium dodecyl selenite soap, and the fatty alcohol is n-butanol.

[0006] Furthermore, the mass ratio of the sodium dodecyl selenite soap to n-butanol is 1:1.

[0007] Furthermore, the oil phase refers to one or more liquid mixtures of normal saturated alkanes with a total number of carbon atoms in their molecular structure ranging from 7 to 16.

[0008] Furthermore, the mass ratio of the oil phase to the emulsifier is 1:9.

[0009] The present invention provides a method for preparing the above-mentioned sodium dodecyl selenite soap, comprising: reacting bromododecane with Na2Se2 to obtain dodecyl diselenide; then oxidizing dodecyl diselenide with nitric acid to obtain dodecyl selenite; and finally mixing dodecyl selenite and sodium hydroxide in a molar ratio of 1:1 to obtain sodium dodecyl selenite soap.

[0010] This invention also provides the application of selenite soap-based microemulsions in on-demand demulsification and recovery. By changing the pH value of the selenite soap-based microemulsion, command-driven demulsification of the selenite soap-based microemulsion can be achieved, resulting in a one-solid-two-liquid-three-phase system, thus realizing the recovery of organic selenite.

[0011] The selenite soap-based microemulsion described in this invention exhibits strong stability. The droplet size of the obtained microemulsion remains largely unchanged under conditions such as storage at 25°C for 35 days, freeze-thaw cycles at -18°C to 25°C, and centrifugation at 10,000 rpm for 20 minutes.

[0012] The method of the present invention has the following advantages over the prior art: The selenite soap-based microemulsion provided by this invention fills a gap in publicly available domestic and international literature regarding selenite soap-based microemulsions. It consists of an aqueous phase, an oil phase, and an emulsifier. The emulsifier comprises the main emulsifier, organic sodium selenite soap, and the auxiliary agent, fatty alcohol. The selenite soap-based microemulsion provided by this invention is miscible with water in any proportion without any phase separation, layering, turbidity, or precipitation. The emulsifier content can be as low as 0.045%, exhibiting low emulsifier content, good solubilizing properties, and strong stability. By changing the pH value of the selenite soap-based microemulsion, forced demulsification can be achieved, resulting in a three-phase system (one solid, two liquids, three phases), enabling high-efficiency recovery of organic selenite acid with a recovery rate of not less than 96.5%. Simultaneously, the residual aqueous phase, after treatment with activated carbon and anion exchange resin, has an extremely low chemical oxygen demand, not exceeding 8.9 mg O2 / L.

[0013] The production process of selenite soap-based microemulsion provided by this invention is simple and efficient, with low equipment requirements, low production costs, low energy consumption, and no waste emissions. The command-driven demulsification technology for selenite soap-based microemulsion provided by this invention is simple, efficient, rapid, with low equipment requirements, low costs, and low energy consumption. Attached Figure Description

[0014] Figure 1 The sodium dodecyl selenite soap obtained in Example 1 of this invention 1 H NMR and 77 Se NMR spectrum.

[0015] Figure 2 This is the phase diagram of the selenite soap-based microemulsion of Example 2 of the present invention.

[0016] Figure 3 This is a diagram illustrating the demulsification effect of selenite soap-based microemulsion in Example 6 of the present invention.

[0017] Figure 4 These are electron microscope images of the oil and aqueous phases obtained after complete demulsification of the selenite soap-based microemulsion in Example 6 of this invention. Detailed Implementation

[0018] The following specific embodiments further illustrate the process methods and effects of the sodium dodecyl selenite soap, microemulsion, dilutionability, command demulsification, and selenite recovery provided by the present invention.

[0019] Example 1: Synthesis of Sodium Dodecyl Selenite Soap The reaction of bromododecane with Na₂Se₂ yields dodecyl diselenyl ether, which is then oxidized with nitric acid to give dodecyl selenite. 1 H NMR spectrum and 77 The Se NMR spectra are shown below. Figure 1 A and Figure 1 B. By Figure 1 As shown in A, the H signal of the terminal methyl group of dodecyl selenite (3 H) is around 0.86 ppm, the H signal of the 9 methylene groups in the carbon chain of dodecyl selenite (18 H) is around 1.21 ppm, the H signal of the 1 methylene group in the carbon chain of dodecyl selenite (2 H) is around 1.66 ppm, the H signal of the 1 methylene group in the carbon chain of dodecyl selenite (2 H) is around 3.1 ppm, and the H signal of the acidic H of dodecyl selenite (1 H) is around 5.6 ppm. The area integral ratio of the above H signals is 3:18:2:2:1, which is completely consistent with the theoretical value of the molecular structure of dodecyl selenite. Figure 1 The Se signal (1 Se) in dodecyl selenite is around 1214.2 ppm in B.

[0020] Dodecyl selenite and sodium hydroxide were mixed in a molar ratio of 1:1, anhydrous methanol was added and mixed evenly at room temperature, the solvent was removed and dried to obtain a white sodium dodecyl selenite soap solid with a yield of 100%.

[0021] Dodecyl selenite and sodium hydroxide were mixed in a molar ratio of 1:1, deionized water was added and the mixture was stirred evenly at room temperature. After removing the solvent water under reduced pressure, the mixture was dried to obtain a white sodium dodecyl selenite soap solid with a yield of 100%.

[0022] Dodecyl selenite and sodium hydroxide were mixed in a molar ratio of 1:1. A mixture of n-butanol and deionized water in a volume ratio of 1:1 was added and mixed evenly at room temperature. After removing the solvent, the mixture was dried to obtain a white sodium dodecyl selenite soap solid with a yield of 100%.

[0023] Analysis by two-phase titration showed that the purity of the sodium dodecyl selenite soap obtained in this embodiment was not less than 99.7%.

[0024] Example 2: Selenite soap-based microemulsion with n-decane C10 as the oil phase and phase diagram In this embodiment, sodium dodecyl selenite soap obtained in Example 1 is used as the main emulsifier, n-butanol is used as the co-emulsifier, and a composition of lauric acid amine soap and n-pentanol in a mass ratio of 1:1 is used as the emulsifier. n-Decane (C10) is used as the oil phase to construct a selenite soap-based microemulsion, designated MEC10. Figure 2 This is a phase diagram of a selenite soap-based microemulsion with n-decane C10 as the oil phase. Figure 2 Em represents the emulsifier, Decane represents the C10 oil phase, and the blue shaded area represents the microemulsion phase. From Figure 2 It can be seen that the MEC10 microemulsion region is connected to the water corner, indicating that MEC10 belongs to the selenite soap-based microemulsion that can be infinitely diluted with water. Further analysis... Figure 2The results lead to the following conclusion: when emulsifier, C10 oil and water are mixed in a mass ratio of 70.2:7.8:22 and then any proportion of water is added, they can spontaneously emulsify to form a selenite soap-based microemulsion.

[0025] Analysis using conductivity method Figure 2 The conductivity changes of MEC10 microemulsions with a mass ratio of Em (emulsifier) ​​to Decane (C10 oil) of 9:1 and varying water content (mass percentage, %) showed that when the water content was in the range of 21.6% to 33.9%, the resulting MEC10 microemulsion was a W / O type microemulsion; when the water content was in the range of 33.9% to 55.2%, the resulting MEC10 microemulsion was a BC type microemulsion; and when the water content was in the range of 55.2% to 99.9%, the resulting MEC10 microemulsion was an O / W type microemulsion.

[0026] Example 3: Stability of selenite soap-based microemulsions A MEC10 selenite soap-based microemulsion, designated MEC10-778, was prepared with a water content of 77.8%, a C10 oil content of 2.2%, and an emulsifier content of 20%. Identification confirmed that the MEC10-778 selenite soap-based microemulsion is an O / W type microemulsion. Dynamic laser light scattering (DLS) technology was used to measure the droplet diameter of the MEC10-778 microemulsion, which was approximately 8.8 nm. After storage at 25°C for 35 days, the MEC10-778 microemulsion remained clear and transparent, without any observed layering, phase separation, turbidity, or precipitation. DLS measurement showed that the droplet diameter of the MEC10-778 microemulsion after 35 days of storage at 25°C was approximately 8.9 nm.

[0027] The MEC10-778 microemulsion obtained in this embodiment was first frozen at -18°C for 12 hours, and then allowed to thaw naturally at 25°C for 3 hours. Upon observation, the MEC10-778 microemulsion remained clear and transparent, with no observed layering, phase separation, turbidity, or precipitation. The thawed MEC10-778 microemulsion was then subjected to 10 freeze-thaw cycles under the same conditions. Again, the MEC10-778 microemulsion remained clear and transparent, with no observed layering, phase separation, turbidity, or precipitation. Dynamic laser light scattering (DLS) technology determined that the droplet diameter of the MEC10-778 microemulsion after 10 freeze-thaw cycles was approximately 8.6 nm.

[0028] The MEC10-778 microemulsion obtained in this embodiment was centrifuged continuously at 10,000 rpm for 20 minutes at room temperature. The MEC10-778 microemulsion remained clear and transparent, with no observed layering, phase separation, turbidity, or precipitation. The MEC10-778 microemulsion sample, after one centrifugation, was then intermittently centrifuged under the same conditions for 20 cycles. The MEC10-778 microemulsion remained clear and transparent, with no observed layering, phase separation, turbidity, or precipitation. Dynamic laser light scattering (DLS) technology determined that the diameter of the MEC10-778 microemulsion droplets after 20 cycles of centrifugation at 10,000 rpm for 20 minutes was approximately 8.7 nm.

[0029] Example 4: Selenite soap-based microemulsion with alkane as the oil phase Based on the research on selenite soap-based microemulsions with C10 as the oil phase, further investigation was conducted using one or more of the following petroleum ethers with boiling ranges of 60-90°C (C69) and 90-120°C (C912) as the oil phase: n-heptane (C7), n-dodecane (C12), n-tetradecane (C14), and n-hexadecane (C16) with boiling ranges of 60-90°C and 90-120°C (C912), respectively. The emulsifier, oil phase, and deionized water were mixed at room temperature in a mass ratio of 70.2:7.8:22. The resulting selenite soap-based microemulsion codes and effects are listed in Table 1. In some of the soap-based microemulsions, the emulsifier was not added in the form of a mixture of sodium dodecyl selenite soap and n-butanol, but in the form of a mixture of dodecyl selenite, sodium hydroxide, and n-butanol, respectively. The molar ratio of dodecyl selenite and sodium hydroxide was 1:1, and n-butanol was added at 3.775 times the mass of sodium hydroxide.

[0030] Table 1. Series of selenite soap-based microemulsions with alkane as the oil phase.

[0031] As shown in Table 1, both pure alkanes and mixtures of alkanes can spontaneously form stable selenite soap-based microemulsions. The main emulsifier in the emulsifier can be added in the form of sodium dodecyl selenite soap to form a stable soap-based microemulsion, or it can be added in the form of a mixture of dodecyl selenite, sodium hydroxide, and n-butanol to form a stable selenite soap-based microemulsion in situ. This fully demonstrates that the production process of the selenite soap-based microemulsion provided by this invention is extremely simple and efficient, with very low equipment requirements, low production costs, ultra-low energy consumption, and no waste emissions.

[0032] Example 5: Water dilution properties of selenite soap-based microemulsions Example 2 has already detailed the water dilution properties of MEC10 selenite soap-based microemulsion. This example continues to use the series of selenite soap-based microemulsions obtained in Table 1 as examples to further illustrate the water dilution properties of selenite soap-based microemulsions. First, taking the selenite soap-based microemulsion designated MEC12 in Table 1 as an example, using deionized water as a diluent, the dilution effect of MEC12 was examined. According to the composition of MEC12 described in Example 3, the percentage of water in MEC12 is 22%. Different amounts of deionized water were directly added to the MEC12 obtained in Example 3 to obtain a series of selenite soap-based microemulsions with different water contents. The sample codes, water contents, and dilution effects are shown in Table 2.

[0033] Table 2. Series of selenite soap-based microemulsions obtained by diluting MEC12 with deionized water

[0034] As shown in Table 2, MEC12 exhibits excellent water dilution properties. The diluted series of selenite soap-based microemulsions are clear and transparent. No abnormal stratification, phase separation, turbidity, or precipitation was observed after storage at 25°C for 35 days, centrifugation at 10,000 rpm for 20 minutes 20 times, or freeze-thaw cycles at -18°C to 25°C for 10 times. In particular, the microemulsion droplet size of the series of selenite soap-based microemulsions diluted to a water content of 75.8% to 99.9% did not change significantly after storage at 25°C for 35 days, centrifugation at 10,000 rpm for 20 minutes 20 times, and freeze-thaw cycles at -18°C to 25°C for 10 times. This quantitatively demonstrates that MEC12 has excellent water dilution properties.

[0035] Except for MEC12 selenite soap-based microemulsion, the water dilution effects of the selenite soap-based microemulsions listed in Table 1 are similar to those listed in Table 2. All the series of soap-based microemulsions obtained after dilution are clear and transparent. No abnormal layering, phase separation, turbidity or precipitation was observed, whether stored at 25°C for 35 days, centrifuged at 10,000 rpm for 20 minutes 20 times, or subjected to freeze-thaw cycles of -18°C to 25°C 10 times.

[0036] According to the data in Table 2 and the composition calculation of the selenite soap-based microemulsion described in this embodiment, after dilution with water, the percentage content of emulsifier in the selenite soap-based microemulsion can be reduced to 5% or less, with a minimum of 0.045%, and the stability is good.

[0037] Example 6: Command-based demulsification of selenite soap-based microemulsions This embodiment first uses the selenite soap-based microemulsion MEC10-778 obtained in Example 3 as an example to illustrate the command-driven demulsification effect of the selenite soap-based microemulsion. The pH value of MEC10-778 was adjusted to 2.0 by adding hydrochloric acid, and the demulsification effect of the soap-based microemulsion was observed. The results are shown in […]. Figure 3 After adjusting the pH to 2.0 with hydrochloric acid, the originally clear and transparent MEC10-778 ( Figure 3 A1) transformed into a solid-liquid-three-phase system within 1 minute. Figure 3 A2), the solid can be separated using a simple filtration process, and after drying, it appears as a white solid. Figure 3 A3), after analysis and identification Figure 3 The white solid in A3 is dodecyl selenite. Therefore, the dodecyl selenite solid can be recovered after command-driven demulsification, with a recovery rate of 97.1 ± 0.1%. The two remaining liquid phases after separating the dodecyl selenite solid separate into two layers. Figure 3 A4), identified by Nille Red staining, has an upper oil phase and a lower aqueous phase, which can be separated using liquid-liquid separation techniques.

[0038] In the aforementioned on-demand demulsification technology, the pH of MEC10-778 was adjusted to 2.0 by replacing hydrochloric acid with sulfuric acid and phosphoric acid, respectively. MEC10-778 demulsified within 1 minute in both cases, transforming into a three-phase system (one solid, two liquids, and three phases). Figure 3 (The effect shown in A2 is the same). After adjusting the pH of MEC10-778 to 2.0 with sulfuric acid, the recovery rate of dodecyl selenite solid was 97.2±0.3%. After adjusting the pH of MEC10-778 to 2.0 with phosphoric acid, the recovery rate of dodecyl selenite solid was 97.3±0.2%. It can be seen that the type of acid used to adjust the pH of selenite soap-based microemulsion has no significant adverse effect on the on-demand demulsification effect.

[0039] The required pH value for imperative demulsification of the other selenite soap-based microemulsions described in Tables 1 and 2 is 2.0. Furthermore, demulsification occurred within one minute of pH adjustment to 2.0, resulting in a three-phase system consisting of one solid, two liquids, and three phases. Dodecyl selenite solids could be separated using filtration techniques, with recoveries ranging from a minimum of 96.5% to a maximum of 99.1%. After separation, both the upper oil phase and the lower aqueous phase, in a stratified state, were clear and transparent. Dynamic laser light scattering and cryo-transmission electron microscopy revealed the absence of aggregate structures in both phases. (See the results below.) Figure 4 A (Dynamic Laser Light Scattering Instrument) and Figure 4 B and C (cryotransmission electron microscopy).

[0040] Example 7: Chemical Oxygen Demand (COD) of the aqueous phase obtained after command-driven demulsification of selenite soap-based microemulsion This embodiment uses the aqueous phase obtained after command-driven demulsification of the selenite soap-based microemulsion described in Example 6 as an example to illustrate the effect of reducing the chemical oxygen demand (COD) to 8.9 mg O2 / L or below after treatment with ion exchange resin and activated carbon. The aqueous phase was mixed with 15g of ion exchange resin per 500ml of aqueous phase and allowed to stand for 5 minutes. After three adsorption treatments with ion exchange resin, the wastewater phase and activated carbon were mixed at room temperature for 12 hours at a mass ratio of 1:0.5. The activated carbon was then removed by filtration, yielding the treated aqueous phase. The COD value of the treated aqueous phase was analyzed. The results show that the maximum COD value of all treated aqueous phases in this embodiment was 8.7 ± 0.2 mg O2 / L, and the minimum was 6.1 ± 0.4 mg O2 / L. The results of this embodiment demonstrate that the aqueous phase obtained by the command-driven demulsification technology provided by this invention, after conventional treatment with ion exchange resin and activated carbon, has a COD that does not exceed 8.9 mg O2 / L.

[0041] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Any person skilled in the art can easily make changes or substitutions to the components after the present invention is disclosed, and all technical improvements that do not depart from the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A selenite soap-based microemulsion, characterized in that, The microemulsion consists of an aqueous phase, an oil phase, and an emulsifier, wherein the emulsifier consists of a primary emulsifier, organic sodium selenite soap, and an auxiliary agent, fatty alcohol.

2. The selenite soap-based microemulsion according to claim 1, characterized in that, The organic sodium selenite soap is sodium dodecyl selenite soap, and the fatty alcohol is n-butanol.

3. The selenite soap-based microemulsion according to claim 2, characterized in that, The mass ratio of sodium dodecyl selenite soap to n-butanol is 1:

1.

4. The selenite soap-based microemulsion according to claim 1, characterized in that, The oil phase refers to one or more liquid mixtures of normal saturated alkanes with a total number of carbon atoms in their molecular structure ranging from 7 to 16.

5. The selenite soap-based microemulsion according to claim 1, characterized in that, The mass ratio of the oil phase to the emulsifier is 1:

9.

6. The selenite soap-based microemulsion according to claim 2, characterized in that, The method for preparing sodium dodecyl selenite soap includes: reacting bromododecane with Na2Se2 to obtain dodecyl diselenide; then oxidizing dodecyl diselenide with nitric acid to obtain dodecyl selenite; and finally mixing dodecyl selenite and sodium hydroxide in a molar ratio of 1:1 to obtain sodium dodecyl selenite soap.

7. The application of a selenite soap-based microemulsion as described in any one of claims 1-6 in on-demand demulsification and recycling.

8. The application according to claim 7, characterized in that, By changing the pH value of selenite soap-based microemulsions, command-driven demulsification of selenite soap-based microemulsions can be achieved, resulting in a three-phase system consisting of one solid, two liquids, and one phase, thus enabling the recovery of organic selenite.

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