Method for modifying vermiculite with surfactant and application of modified vermiculite

Abstract

The application discloses a method for modifying vermiculite by using a surfactant and application of the modified vermiculite, and the method comprises the following steps: step A, pretreating vermiculite to obtain vermiculite powder; step B, adding the vermiculite powder into a sodium carbonate solution, heating and stirring, and then standing and centrifuging after the heating and stirring; washing the obtained solid to neutral, drying, and grinding and screening to obtain sodiumized vermiculite; step C, dispersing the sodiumized vermiculite into deionized water to obtain a sodiumized vermiculite dispersion liquid; step D, adding a gemini surfactant into the sodiumized vermiculite dispersion liquid, heating and stirring to react, and then centrifuging to obtain a solid product; and step E, washing the solid product with deionized water until no foam is generated, drying, and then grinding and screening to obtain the modified vermiculite; the modified vermiculite can be used for adsorbing anionic dyes. The application can solve the technical problem that the modified vermiculite has a low adsorption capacity for anionic dyes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vermiculite. Specifically, it is a method for modifying vermiculite using a surfactant and the application of modified vermiculite. BACKGROUND

[0002] As a water treatment adsorbent, not only the application performance is concerned, but also the price, source and storage of the material are considered. Vermiculite (Vt) is abundant in reserves, widely distributed, non-toxic and harmless. Vermiculite has characteristics in terms of composition elements and interlayer charge. Modified vermiculite is simple to operate, which proves the possibility of vermiculite as a functional material. Li + and Na + ions contained in the vermiculite layer have exchangeability and can be called exchangeable cations. Due to the cation exchange capacity of vermiculite, vermiculite can be prepared into excellent adsorbents and ion exchangers. The research on vermiculite as an adsorbent can be divided into two categories: one is natural vermiculite as an adsorbent, which exchanges ions with water pollutants, and the adsorption of heavy metals Pb 2+ , Ag + , Ni 2+ , Cr 3+ is the most, and the adsorption of dyes is relatively less. The other is modified vermiculite and activated vermiculite. Activated vermiculite refers to methods such as acid leaching and heat activation to change the surface properties of vermiculite. Modified vermiculite refers to the intercalation of surfactants into the interlayer of vermiculite to adsorb organic compounds, organic dyes and heavy metals. However, the modification method, structure and amount of surfactants have a great influence on the modification results of vermiculite. Traditional surfactants have only one head group and a hydrophobic group. By changing the alkyl chain length, various properties can be improved, but the ability to reduce surface tension is limited. Therefore, the modified vermiculite prepared by using surfactants still has great potential for improvement in the adsorption performance of anionic dyes. SUMMARY

[0003] Therefore, the technical problem to be solved by the present application is to provide a method for modifying vermiculite using a surfactant and the application of modified vermiculite, so as to solve the technical problem that the modified vermiculite has low adsorption capacity for anionic dyes.

[0004] To solve the above technical problems, the present application provides the following technical solutions:

[0005] The method for modifying vermiculite using a surfactant comprises the following steps:

[0006] Step A, pretreating vermiculite to obtain vermiculite powder;

[0007] Step B, after adding vermiculite powder into sodium carbonate solution, heating and stirring, after heating and stirring, standing, centrifugation; the solid obtained by centrifugation is washed to neutral, dried, and ground to obtain sodium vermiculite;

[0008] Step C, the sodium vermiculite is dispersed into deionized water to obtain a sodium vermiculite dispersion;

[0009] Step D, the Gemini surfactant is added to the sodium vermiculite dispersion, heated and stirred to react, and then centrifuged to obtain a solid product;

[0010] Step E, the solid product is washed with deionized water until no foam is generated, and then dried and ground to obtain the modified vermiculite.

[0011] In the preparation of sodium vermiculite, sodium carbonate solution is selected as the sodium source, compared with other sodium compounds such as sodium hydroxide, sodium bicarbonate, sodium chloride and sodium sulfate, the prepared sodium vermiculite is more beneficial to the intercalation of the Gemini surfactant, the intercalation modification effect is significantly improved, and the adsorption performance of the modified vermiculite to anionic dyes is significantly improved. After heating and stirring during sodium treatment, the sodium vermiculite and the aqueous phase are separated by standing for a period of time before centrifugation, which facilitates better separation of the sodium vermiculite and the aqueous phase, and on the other hand, it is beneficial to the sodium treatment of the vermiculite and the improvement of the modification effect of the Gemini surfactant. If the heating and stirring are not followed by standing and direct centrifugation, the modification effect of the modified vermiculite will be significantly reduced, which will affect the adsorption performance of the modified vermiculite to anionic dyes.

[0012] In the above method for modifying vermiculite with a surfactant, in step D, the preparation method of the Gemini surfactant is as follows:

[0013] Step (D-1), 1,4-cyclohexanediol and chloroacetyl chloride are mixed and subjected to heating and reflux reaction, and after the reaction is completed, the reaction system A is obtained by cooling to room temperature;

[0014] Step (D-2), first, distilled water is added to the reaction system A to hydrolyze the residual chloroacetyl chloride, then a saturated sodium bicarbonate solution is added to adjust the pH to alkaline, and finally, dichloromethane is used to extract the organic phase; the organic phase obtained by extraction is subjected to rotary evaporation to obtain an intermediate;

[0015] Step (D-3), the intermediate, ethyl acetate and tertiary amine are mixed and subjected to heating and reflux reaction, and after the reaction is completed, the reaction system B is obtained; the reaction system B is subjected to rotary evaporation to obtain a surfactant crude product;

[0016] Step (D-4), the surfactant crude product is redispersed in an organic solvent and subjected to heating and reflux reaction, and after the reaction is completed, the crystalline body is obtained by cooling, standing and suction filtration, and the crystalline body is dried to obtain the Gemini surfactant.

[0017] In step (D-1), the ratio of the volume of chloroacetyl chloride to the mass of 1,4-cyclohexanediol is 1.5-2.0 mL / g; the temperature of heating reflux is 90-100℃, and the reflux reaction time is 4-5 h.

[0018] In step (D-2), the ratio of the amount of distilled water to the volume of chloroacetyl chloride in step (D-1) is (1-2):1; saturated sodium bicarbonate solution is added to adjust the pH to 8-8.5

in this pH range, the hydrolysis of chloroacetyl chloride can be ensured to be complete, and the generated product will not be hydrolyzed

[0019] In step (D-3), the ratio of the intermediate to the tertiary amine is 1:2.0-2.5 in terms of the amount of substance; the ratio of ethyl acetate to the tertiary amine is (15-20):1 in terms of volume; the temperature of heating reflux is 90-100℃, and the reflux reaction time is 60-72 h; the temperature of rotary evaporation of the reaction system B is 60-80℃, and the rotary evaporation time is 2-3 h;

[0020] In step (D-4), the solid-liquid ratio of the crude surfactant to the organic solvent is 1:(10-15)

that is, 10-15 mL of the organic solvent needs to be added for every 1 g of the crude surfactant for dispersion

[0021] In the method for modifying vermiculite using a surfactant, the tertiary amine is N,N-dimethyl dodecylamine (dodecyl dimethyl tertiary amine), N,N-dimethyl tetradecylamine (tetradecyl dimethyl tertiary amine), N,N-dimethyl hexadecylamine (hexadecyl dimethyl tertiary amine), or N,N-dimethyl octadecylamine (octadecyl dimethyl tertiary amine).

[0022] In the method for modifying vermiculite using a surfactant, in step A, the method for pretreating vermiculite is as follows: after vermiculite is fully soaked with distilled water, it is ultrasonically cleaned in an ultrasonic cleaner for 20-30 min; after ultrasonic cleaning, it is suction filtered and dried at a temperature of 80-90℃; after drying, it is ground and passed through a 200-mesh sieve.

[0023] In step B of the method for modifying vermiculite by using surfactants, the molar concentration of the sodium carbonate solution is 1.0-2.0 mol / L; the mass ratio of the vermiculite powder to the sodium carbonate solution is 10-20:100; the temperature for heating and stirring is 80-90℃, and the time for heating and stirring is 6-8 h; after the heating and stirring are completed, the centrifugation is performed after standing for 8-12 h; the drying temperature is 75-85℃, and the drying time is 8-10 h; and the grinding is followed by sieving through a 200-mesh sieve.

[0024] In step C of the method for modifying vermiculite by using surfactants, the mass ratio of the sodium-modified vermiculite to the deionized water is 1-2:100.

[0025] In step D of the method for modifying vermiculite by using surfactants, the mass of the gemini surfactant is 25-100% of the mass of the sodium-modified vermiculite dispersion; the temperature for heating and stirring is 60-70℃, and the time for heating and stirring is 2-12 h; in step E, the drying temperature is 80-85℃, and the drying time is 8-10 h; and the grinding is followed by sieving through a 200-mesh sieve.

[0026] In step A of the method for modifying vermiculite by using surfactants, the method for pretreating the vermiculite is as follows: the vermiculite is fully soaked in distilled water and then ultrasonically cleaned in an ultrasonic cleaner for 20 min; after the ultrasonic cleaning is completed, the vermiculite is suction-filtered and dried at a temperature of 80℃; after the drying is completed, the vermiculite is ground and sieved through a 200-mesh sieve; this pretreatment is beneficial to the sodium ions entering the interlayer of the vermiculite and changing the interlayer charge during the sodium modification of the vermiculite, and is also beneficial to the gemini surfactant entering the interlayer of the vermiculite and replacing the cations in the interlayer, thereby improving the modification effect; if the particle size of the vermiculite is greater than 200 mesh, the sodium modification and the replacement of the interlayer ions of the vermiculite by the surfactant will be affected, and the adsorption effect of the modified vermiculite on anionic dyes will be affected;

[0027] In step B, the molar concentration of the sodium carbonate solution is 1.5 mol / L; the mass ratio of the vermiculite powder to the sodium carbonate solution is 15:100; the temperature for heating and stirring is 80℃, and the time for heating and stirring is 8 h; after the heating and stirring are completed, the centrifugation is performed after standing for 12 h; the drying temperature is 80℃, and the drying time is 10 h; and the grinding is followed by sieving through a 200-mesh sieve.

[0028] In step C, the mass ratio of the sodium-modified vermiculite to the deionized water is 1:100.

[0029] In step D, the mass of the gemini surfactant is 50% of the mass of the sodium-modified vermiculite dispersion; the temperature for heating and stirring is 60℃, and the time for heating and stirring is 2 h; under this modification condition, the decomposition of the gemini surfactant can be avoided, and the modification of the sodium-modified vermiculite can achieve an ideal effect.

[0030] In step E, the drying temperature is 80℃, and the drying time is 8h; after grinding, pass through a 200-mesh screen

the modified vermiculite has a better adsorption effect at this particle size

[0031] In step D, the preparation method of the gemini surfactant is as follows:

[0032] In step (D-1), 1,4-cyclohexanediol and chloroacetyl chloride are mixed and heated to reflux at 95℃ for 5h

under this reaction condition, the yield of the product is high, and the amount of by-product is small

under this ratio, the yield of the gemini surfactant is high, and the residual amount of chloroacetyl chloride is small

[0033] In step (D-2), distilled water is first added to the reaction system A to hydrolyze the residual chloroacetyl chloride; the volume ratio of the amount of distilled water to the volume of chloroacetyl chloride in step (D-1) is 1:1; then, saturated sodium bicarbonate solution is added to adjust the pH to 8; finally, the organic phase is extracted with dichloromethane for 3 times; the volume ratio of dichloromethane to chloroacetyl chloride in step (D-1) is 1:1 each time; the organic phase obtained by extraction is rotary evaporated at 25℃ to obtain an intermediate;

[0034] In step (D-3), the intermediate, ethyl acetate and tetradecyldimethyl tertiary amine are mixed and heated to reflux at 95℃ for 72h

under this reaction condition, the yield of the product is high, and the amount of by-product is small

which can ensure that the tertiary amine is completely reacted, and is conducive to the subsequent rotary evaporation separation

[0035] In step (D-4), the crude surfactant is dispersed into an organic solvent and heated to reflux at 60℃ for 30min; the solid-liquid ratio of the organic solvent to the crude surfactant is 1:10

i.e., 10mL of organic solvent is needed for every 1g of crude surfactant for dispersion

[0036] The modified vermiculite prepared by the above method is used for the adsorption of anionic dyes.

[0037] The technical scheme of the present application achieves the following beneficial technical effects:

[0038] 1、The sodiumization of vermiculite by sodium carbonate in the present application can not only improve the cation exchange capacity of vermiculite, but also can be beneficial to the intercalation modification of Gemini surfactant.

[0039] 2、Compared with the traditional surfactant as a modifier, the self-made Gemini surfactant is used as a modifier of sodiumized vermiculite in the present application, especially the Gemini surfactant synthesized by taking tetradecyl dimethyl tertiary amine as a raw material, which has a higher degree of interlayer coincidence with the sodiumized vermiculite prepared by the method of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1a The synthesis schematic diagram of the intermediate in the embodiment of the present application;

[0041] Figure 1b The synthesis schematic diagram of the surfactant in the embodiment of the present application;

[0042] Figure 2 The standard curve of acid red 66 in the embodiment of the present application;

[0043] Figure 3 The XRD diagram of different modified vermiculites prepared in the embodiment of the present application;

[0044] Figure 4 The IR spectrum diagram of different modified vermiculites prepared in the embodiment of the present application;

[0045] Figure 5 The influence of the reaction time of sodiumized vermiculite and surfactant on the adsorption performance in the embodiment of the present application;

[0046] Figure 6 The influence curve diagram of the surfactant structure on the adsorption performance of modified vermiculite in the embodiment of the present application;

[0047] Figure 7The effect of surfactant dosage on the adsorption performance of modified vermiculite in embodiments of the present invention is shown in the graph.

[0048] Figure 8 The effect curve of adsorption equilibrium time on adsorption performance in the embodiments of the present invention;

[0049] Figure 9 The effect of the amount of modified vermiculite added on the adsorption performance in the embodiments of the present invention is shown in the figure.

[0050] Figure 10 The effect of pH on the adsorption performance of modified vermiculite in the embodiments of the present invention;

[0051] Figure 11a The first-order kinetic curve of modified vermiculite adsorbing 15 mg / L Acid Red 66 in an embodiment of the present invention;

[0052] Figure 11b Second-order kinetic curves of modified vermiculite adsorbing 15 mg / L Acid Red 66 in embodiments of the present invention;

[0053] Figure 12a The first-order kinetic curve of modified vermiculite adsorbing 20 mg / L Acid Red 66 in an embodiment of the present invention;

[0054] Figure 12b Second-order kinetic curves of modified vermiculite adsorption of 20 mg / L Acid Red 66 in embodiments of the present invention;

[0055] Figure 13a Langmuir adsorption model of modified vermiculite (T = 298.15 K) according to embodiments of the present invention;

[0056] Figure 13b The Freundlich adsorption model of modified vermiculite (T = 298.15 K) in this embodiment of the invention;

[0057] Figure 14a Langmuir adsorption model of modified vermiculite (T = 308.15 K) according to embodiments of the present invention;

[0058] Figure 14b The Freundlich adsorption model of modified vermiculite (T = 308.15 K) in this embodiment of the invention;

[0059] Figure 15 The modified vermiculite of this invention, lnKL---T -1 Line graph. Detailed Implementation

[0060] 1. Preparation of modified vermiculite

[0061] 1.1 Preparation of sodium vermiculite

[0062] The vermiculite belongs to high layer charge clay, and it is difficult to modify directly due to its high layer charge density. The exchange of inorganic cations can reduce the layer charge, which is beneficial to the organic intercalation reaction. The vermiculite was soaked in distilled water and stirred, and then was ultrasonically cleaned in an ultrasonic cleaner for 20 min, filtered, dried at 80°C, ground in a maroon mortar, and sieved through a 200-mesh sieve. A certain amount of vermiculite was placed in a 250-mL beaker, and 1.5 mol / L Na2CO3 solution was added to the beaker, with a solid-liquid ratio of 15% (mass ratio). The mixture was stirred at 80°C for 8 h, and then was left to stand for 12 h before being centrifuged. The supernatant was discarded after the centrifuged sample was washed with distilled water until it was neutral. The sample was dried in an oven at 80°C for 10 h, ground, and sieved through a 200-mesh sieve for storage.

[0063] The sodium vermiculite prepared in this example has a high negative charge and a high hydration, swelling and dispersion capacity, which is beneficial to the intercalation of the intercalation agent, as indicated by the cation exchange capacity (CEC) of the sodium vermiculite, which was measured by the exchange of ammonium ions and was 92.00 mmol / 100 g.

[0064] 1.2 Preparation of organic vermiculite

[0065] 1.2.1 Synthesis of cationic surfactant (Gemini surfactant)

[0066] 5 g (0.05 mol) of 1,4-cyclohexanediol was refluxed with 9 mL of chloroacetyl chloride at 95°C for 5 hours. After cooling, the unreacted chloroacetyl chloride was hydrolyzed with distilled water (the ratio of the amount of distilled water to the initial volume of chloroacetyl chloride was 1:1), the pH was adjusted to 8 with a saturated NaHCO3 solution, and the organic phase was extracted with dichloromethane three times (the ratio of dichloromethane to the initial volume of chloroacetyl chloride was 1:1). After rotary evaporation, the intermediate was obtained and stored in a sealed container. The temperature during rotary evaporation of the organic phase was 25°C. The specific synthesis steps are shown in Figure 1a .

[0067] 1.35 g (0.005 mol) of the intermediate, 40 mL of ethyl acetate, and 2.2 times (2.2 times the amount of the intermediate) of different carbon chain tertiary amines (carbon chains of 12, 14, 16, and 18, respectively, such as dodecyl dimethyl tertiary amine, tetradecyl dimethyl tertiary amine, hexadecyl dimethyl tertiary amine, or octadecyl dimethyl tertiary amine) were refluxed at 95°C for 72 h. After cooling, the temperature was set to 70°C for 2 h for rotary evaporation, and a white powder was obtained, which was the crude surfactant. The crude surfactant was dispersed in an organic solvent and recrystallized at 60°C. The solid-liquid ratio of the organic solvent to the crude surfactant was 1:10 (i.e., 10 mL of organic solvent was added for every 1 g of crude surfactant for dispersion). The organic solvent was a mixture of chloroform and acetone in a volume ratio of 1:2. The solution was clear and stable. After 30 min of reaction, the solution was cooled and filtered. The crystalline product was dried (drying temperature: 60°C, drying time: 3 h) to obtain the surfactant. The specific synthesis steps are shown in Figure 1b.

[0068] In this embodiment, the surfactant synthesized by using dodecyl dimethyl tertiary amine with a carbon chain of 12 is denoted as C12-EG-C12; the surfactant synthesized by using tetradecyl dimethyl tertiary amine with a carbon chain of 14 is denoted as C14-EG-C14; the surfactant synthesized by using hexadecyl dimethyl tertiary amine with a carbon chain of 16 is denoted as C16-EG-C16; and the surfactant synthesized by using octadecyl dimethyl tertiary amine with a carbon chain of 18 is denoted as C18-EG-C18.

[0069] 1.2.2 Preparation of organically modified vermiculite

[0070] The organically modified vermiculite is obtained by exchanging inorganic ions in the interlayer of vermiculite with organic cations, so that the organic cations enter the interlayer of vermiculite to obtain modified organic vermiculite. First, a certain amount of sodium vermiculite (or raw vermiculite) is mixed with deionized water in a conical flask at a solid-liquid ratio of 1:100 to obtain a mixed dispersion liquid, and then a certain amount of a series of gemini quaternary ammonium salt surfactants (the gemini quaternary ammonium salt surfactants are C12-EG-C12, C14-EG-C14, C16-EG-C16 or C18-EG-C18 prepared in the foregoing, and the addition amount is set to 25wt%, 50wt%, 75wt%, 100wt% of the mass of the mixed dispersion liquid) is added to the mixed dispersion liquid, and the mixture is stirred at 60°C for a period of time. After cooling and centrifugation, the solid product obtained by centrifugation of the mixed modified vermiculite dispersion system is washed 6 times with deionized water until no foam is generated, and the obtained sample is dried at 80°C in an oven for 8h. The sample is ground with a mortar and sieved through a 200 mesh sieve, and is sealed and stored for use. The amount of surfactant and the amount of vermiculite are related as follows:

[0071]

[0072] In the formula, CEC is the cation exchange capacity of sodium vermiculite (mmol / g); n 表 is the amount of substance of the surfactant (mol); m 蛭 is the mass of vermiculite (g).

[0073] In this embodiment, the raw vermiculite is denoted as Vt, and the sodium vermiculite is denoted as Na-Vt; the organically modified sodium vermiculite prepared by using sodium vermiculite, C12-EG-C12 and an addition amount of 25wt% is denoted as Na-Vt+25% carbon dodecane; the organically modified vermiculite prepared by using raw vermiculite, C12-EG-C12 and an addition amount of 25wt% is denoted as Vt+25% carbon dodecane; and the organically modified vermiculite prepared by using other addition amounts or other surfactants is denoted in this form.

[0074] 2 Adsorption test method

[0075] 2.1 Configuration of anionic dyes

[0076] 100 mg of Acid Red 66 was weighed into distilled water, and diluted to a 1 L volumetric flask, ready for use. The maximum wavelength was 505 nm when the dilution was 20 mg / L and scanned by a double-beam UV-visible spectrophotometer. Meanwhile, solutions with mass concentrations of 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L, and 25 mg / L were diluted, and a standard curve was drawn as shown in Figure 2

[0077] The concentration of anionic dyes adsorbed on the organic modified vermiculite can be calculated by the following formula:

[0078]

[0079] The removal rate can be calculated by the following formula:

[0080]

[0081] wherein q e (mg / g) represents the adsorption capacity of the organic modified vermiculite to the anionic dye solution, C0(mg / L) and C e (mg / L) represent the initial concentration and the equilibrium concentration of the anionic dye solution, respectively, m (g) represents the mass of the modified vermiculite (adsorbent), V (L) represents the volume of the solution, A0and Ae represent the initial absorbance and the equilibrium absorbance of the anionic dye solution, respectively.

[0082] 2.2 Determination of adsorption performance

[0083] 50 mL of Acid Red 66 dye was added to a 250 mL conical flask, a certain amount of modified vermiculite was added, sealed, and stirred and shaken in a water bath shaker at 35°C. Samples were taken at different times, the mixture was centrifuged, the absorbance was measured at 505 nm by a double-beam UV-visible spectrophotometer, and the calculation was performed.

[0084] 2.3 Characterization methods

[0085] The phase analysis was performed by a D8 Advance X-ray diffractometer (XRD) produced by Bruker Company in Germany, with the working conditions being: copper target, X-ray wavelength being 0.15418 nm, tube voltage being 40 kV, tube current being 40 mA, scanning range being 2θ = 4-80°, and continuous scanning; the absorbance of the dye was measured by a double-beam UV-visible spectrophotometer TU-1901 produced by Beijing Pu Zai, with the maximum wavelength being 505 nm; the infrared spectrometer used in the experiment was an IRTACER-100 Fourier infrared spectrometer produced by Shimadzu Company in Japan. The spectral wave number range measured for the sample was 4000-400 cm -1 , and the resolution was 4 cm -1 .​

[0086] 3. Characterization Analysis and Discussion of Results

[0087] 3.1 XRD pattern

[0088] like Figure 3 As shown, the peak height of the original vermiculite at 5.93° is 1.49 nm, which is a characteristic peak of vermiculite. The peak at 9.65° is a characteristic peak of biotite, and the presence of biotite affects the CEC value of vermiculite. After sodium modification, the diffraction peaks between 4° and 10° are broken, indicating that sodium ions have changed the interlayer charge of vermiculite, and a large number of ions have been exchanged. After surfactant modification, the diffraction peaks between 4° and 10° are weakened, which is because quaternary ammonium salt compounds have entered the vermiculite interlayer and widened the spacing. When surfactant is intercalated into vermiculite, the diffraction peaks of biotite change significantly, which may be a result of the change in the interlayer charge of biotite and the weakening of the interlayer forces after surfactant intercalation.

[0089] When different amounts of surfactant were intercalated into vermiculite, the sodium ion peak became sharper with increasing surfactant concentration, while the biotite peak height showed slight changes. When the C14 surfactant concentration was 100%, the biotite peak became sharp and shifted backward, which may be due to changes in the surfactant distribution within the vermiculite after more surfactant was intercalated into the sodium-modified vermiculite. The characteristic peaks of vermiculite weakened with different surfactant intercalations, while the sodium ion and biotite peaks became blunted, confirming that the length of the surfactant alkyl chain affects the layer charge of vermiculite.

[0090] 3.2 Infrared Spectrum

[0091] The infrared spectrum of vermiculite, by Figure 4 The absorption peaks in vermiculite can provide information about the elemental bonding patterns within the vermiculite structure. At 1000 cm⁻¹... -1 The strongest absorption peak is located at 685 cm⁻¹, which is the stretching vibration peak formed by the Si-O bonds in the silicon-oxygen tetrahedral layer; at 685 cm⁻¹... -1 The absorption peak is the bending vibration peak of RO-Si (R = octahedral cations such as Al, Fe, Mg, etc.); at 3560 cm⁻¹ -1 The absorption peak is the stretching vibration peak of -OH in the octahedral layer; located at 3420 cm⁻¹. -1 and 1640cm -1 The two absorption peaks represent the stretching and bending vibrations of -OH groups in interlayer water molecules, respectively. Surfactant modification did not destroy the structure of vermiculite itself; it only exchanged with interlayer cations. In Gemini surfactants, the main functional groups are alkyl long chains and ester groups, with a peak at 2920 cm⁻¹. -1 and 2850cm -1 Stretching vibration peaks of -CH3 and -CH2 in surfactants; 1034 cm⁻¹ -1is the stretching vibration peak of C-N and 1000 cm -1 is the stretching vibration peak of Si-O bond; 1450 cm -1 is the in-plane bending vibration peak of C-H bond; 1740 cm -1 is the stretching vibration peak of C=O, indicating the presence of carbonyl in the modified vermiculite, and the absorption peak of carbonyl is usually at 1730 cm -1 , and the displacement to the high frequency region is caused by the strong electron-withdrawing effect of the spacer quaternary ammonium salt cation; 721 cm -1 is the in-plane rocking vibration peak of long-chain methylene, and the characteristic peaks of vermiculite and surfactant in the infrared spectrum confirm that the surfactant is intercalated in the vermiculite.

[0092] 3.3 Effect of reaction time with surfactant on adsorption performance

[0093] Sodium vermiculite was reacted with 50% C14-EG-C14 for different times (2h, 4h, 6h, 8h, 10h, 12h) to prepare samples, and anionic acid red 66 dye was adsorbed. Acid red 66 was diluted to 20 mg / L, 50 mL was taken and dropped into a 250 mL conical flask, and the modified vermiculite was used in an amount of 0.05 g. The absorbance was measured at different times and calculated. The experimental results are shown in Figure 5 . The reaction time of sodium vermiculite with surfactant has a great effect on the adsorption performance of vermiculite, and the removal rate is between 10% and 95%, 2h>4h>8h>6h>10h>12h. The longer the reaction time with surfactant, the worse the effect of modified vermiculite. This is because there are double lipid groups in quaternary ammonium salt surfactant, which are easy to hydrolyze in solution. The more surfactant is lost, the less it is intercalated into vermiculite. Therefore, the best time for surfactant modified vermiculite is 2h, and the removal rate can reach 95.05%.

[0094] 3.4 Effect of surfactant structure on adsorption performance

[0095] Sodium vermiculite was reacted with 50% C12-EG-C12, C14-EG-C14, C16-EG-C16, and C18-EG-C18 for 2h, and then dried and treated, and acid red 66 dye was adsorbed. Acid red 66 was diluted to 20 mg / L, 50 mL was taken and dropped into a 250 mL conical flask, and the modified vermiculite was used in an amount of 0.05 g. The absorbance was measured at different times.

[0096] The experimental results are shown in Figure 6As shown in the figure, the modified vermiculite adsorption 90 min is basically balanced, wherein, the length of the carbon chain is different, the carbon chain of 14 surfactant modified vermiculite is the best, which can reach 95.05%. In the adsorption performance, the carbon chain of 14 > carbon chain of 12 > carbon chain of 16 > carbon chain of 18, which may be related to the length of the alkyl chain of the surfactant and the interlayer spacing of the vermiculite. The shorter the alkyl chain, the less the surfactant can expand the interlayer of the vermiculite, and the adsorption performance of the modified vermiculite is reduced. The longer the alkyl chain, the more the surfactant can enter the interlayer of the vermiculite and exchange ions. The arrangement of the surfactant in the interlayer of the vermiculite is inclined, or the surfactant cannot enter the interlayer structure of the vermiculite completely because the length of the alkyl chain of the cationic surfactant is longer than the interlayer spacing of the vermiculite. It may also be that the stability of the surfactant decreases with the increase of the alkyl chain. Therefore, the reason why the carbon chain of 14 surfactant is better than other chain length surfactants may be that the alkyl chain length of the carbon chain of 14 is more consistent with the interlayer spacing of the vermiculite, and after entering the interlayer of the vermiculite, the surfactant can expand the interlayer of the vermiculite, and the surfactant can enter the vermiculite completely.

[0097] 3.5 Effect of surfactant dosage on adsorption performance

[0098] Different amounts of C14-EG-C14 (25%, 50%, 75%, 100%) were intercalated into sodium vermiculite for 2h and dried for use, and adsorbed acid red 66 dye. Acid red 66 was diluted to 20mg / L, 50mL was taken into a 250mL conical flask, water bath 35℃ oscillation stirring, the amount of modified vermiculite was 0.05g, different time sampling measured absorbance. The experimental results are shown in Figure 7 As shown in the figure, different amounts of surfactant have a certain effect on the modified vermiculite, 50%>100%>75%>25%, among them, 45min before, the amount of 50% and 100% has similar effect on the modification of vermiculite, after 45min, the amount of 50%, 75% and 100% has little difference on the adsorption performance of modified vermiculite, which may be related to the content of sodium ions in the vermiculite. Sodium ion exchange is carried out between the cations in the vermiculite and the sodium ions, and the content of sodium ions increases, but the total number of interlayer charges of the vermiculite does not change. The essence of surfactant modification is the exchange of sodium ions and cations in the surfactant. Because the number of interlayer charges of the vermiculite is limited, when the exchange of cations reaches equilibrium, with the increase of the amount of surfactant, the adsorption effect of the modified vermiculite is similar.

[0099] 3.6 Effect of adsorption equilibrium time on adsorption performance

[0100] The original vermiculite, the original vermiculite reacted with 50% C14-EG-C14 for 2h, the sodium vermiculite reacted with 50% C14-EG-C14 for 2h, and the modified vermiculite was dried for standby and adsorbed acid red 66 dye. Acid red 66 was diluted to 20mg / L, 50mL was taken and dropped into a 250mL conical flask, water bath 35℃ stirring, the amount of modified vermiculite was 0.05g, and the absorbance was measured at different time (5min, 15min, 30min, 45min, 60min, 75min, 90min, 120min). The experimental results are shown in Figure 8 The adsorbent was poured into the dye, and the adsorption rate was very fast within 5min, and then the adsorption rate was steadily rising in the subsequent adsorption experiment, and basically balanced after 90min. Vermiculite has poor adsorption of refractory organic dyes, and the adsorption performance of vermiculite can be improved by modification; sodium vermiculite with 50% surfactant has better modification effect than vermiculite with 50% surfactant, and sodium modification can not only improve the cation exchange capacity of vermiculite, but also promote organic modification.

[0101] 3.7 The influence of the amount of modified vermiculite on the adsorption performance

[0102] The original vermiculite, the original vermiculite reacted with 50% C14-EG-C14 for 2h, the sodium vermiculite reacted with 50% C14-EG-C14 for 2h, and the modified vermiculite was dried for standby and adsorbed acid red 66 dye. Acid red 66 was diluted to 20mg / L, 50mL was taken and dropped into a 250mL conical flask, water bath 35℃ stirring, the amount of modified vermiculite was 10mg, 20mg, 30mg, 40mg, 50mg, 75mg, and the absorbance was measured at different time. The experimental results are shown in Figure 9 The more the amount of input, the more the adsorption amount of acid red 66, 75mg>50mg>40mg>30mg>20mg>10mg, and the removal rate of acid red 66 dye by 75mg and 50mg can reach 95.05%.

[0103] 3.8 The influence of pH on the adsorption performance

[0104] 0.05g sodium vermiculite reacted with 50% C14-EG-C14 for 2h to obtain modified vermiculite, and 50mL of 20mg / L acid red 66 dye was adsorbed, water bath 35℃ oscillation stirring, and the absorbance was measured at different time. 1mol / L HCl solution and 1mol / L NaOH solution were used to adjust the pH of the dye. The experimental results are shown in Figure 10As shown, the adsorption of modified vermiculite is closely related to the acid-base property of the dye, neutral environment (pH = 7) > acidic environment > alkaline environment. In neutral environment, the quaternary ammonium salt cations in the interlayer of modified vermiculite directly interact with anionic dyes. When pH > 7, the sulfonic acid groups in the dye acid red 66 react with hydroxyl groups, and after the destruction of the anion of the dye, the adsorption capacity of the cationic modified vermiculite is weakened; when pH < 7, the sulfonic acid groups in the dye acid red 66 are salified, and the anion content is reduced, and the adsorption is weakened.

[0105] 3.9 Adsorption kinetics

[0106] In a 250 mL conical flask, 50 mL of acid red 66 dye with different initial concentrations and 50 mg of modified vermiculite (sodium vermiculite reacted with 50% C14-EG-C14 for 2 hours) were added, and the adsorption was oscillated in a water bath constant temperature oscillator at 308.15 K. After different adsorption times, the upper liquid was taken out, the absorbance of the solution was measured, the dye concentration and the adsorption amount were calculated, and the Langmuir pseudo-first-order kinetic equation and the pseudo-second-order kinetic equation were expressed.

[0107] ln(q e -q t )=lnq e -k1 t(3-1);

[0108] Pseudo-second-order kinetic equation:

[0109]

[0110] In the formula, k1 is the pseudo-first-order rate constant, min -1 ; k2 is the pseudo-second-order rate constant, g·mg -1 ·min -1 ; q e is the equilibrium adsorption amount; q t is the adsorption amount corresponding to the adsorption time (mg·g -1 ); t is the adsorption time (min).

[0111] From Figure 11a and Figure 11b , Figure 12a and Figure 12b , and Table 1, it can be seen that the pseudo-second-order kinetic equation has high fitting degree and large correlation coefficient R 2 , indicating that the adsorption kinetics model of acid red 66 dye in modified vermiculite is more consistent with the pseudo-second-order reaction model. Since the pseudo-second-order kinetic equation is based on the assumption that the chemical adsorption between the adsorbent and the adsorbate is the rate-controlling step of the entire adsorption process, and the equilibrium adsorption amount calculated by the pseudo-second-order kinetic equation is very close to the experimental value.

[0112] Table 1

[0113]

[0114] 3.10 Isotherm

[0115] At a certain temperature, the relationship between the concentration of acid red 66 dye and the adsorption capacity of modified vermiculite (sodium vermiculite reacted with 50% C14-EG-C14 for 2 hours) when the adsorption of acid red 66 dye by modified vermiculite reached equilibrium can be represented by an adsorption isotherm. The adsorption mechanism of acid red 66 by modified vermiculite can be determined by using an adsorption model. Isotherm simulation of acid red 66 adsorption by modified vermiculite was studied, and the data obtained from the adsorption experiment were fitted using the Langmuir isotherm equation and the Freundlich isotherm equation, respectively.

[0116] (1) Langmuir adsorption model:

[0117]

[0118] (2) Freundlich adsorption model:

[0119]

[0120] where q e is the equilibrium adsorption capacity of acid red 66 by modified vermiculite (mg / g); C e is the concentration of the solution when the adsorption reaches equilibrium (mg / L); q m is the maximum adsorption capacity of acid red 66 by modified vermiculite; K L is the Langmuir isotherm constant related to the adsorption of acid red 66 by modified vermiculite (L / mg); K F is the Freundlich isotherm constant related to the binding energy, reflecting the difficulty of adsorption; is the component factor, indicating the strength of the adsorption capacity with the increase of concentration, reflecting the difficulty of adsorption.

[0121] The experimental results are shown in Tables 1 and 2, and Figures 1 and 2. Figure 13a and Figure 13b , Figure 14a and Figure 14b At T = 298.15 K and T = 308.15 K, the Langmuir adsorption model and the Freundlich adsorption model both conform to the linear relationship, but the R 2 of the Langmuir adsorption model is higher than the R 2 of the Freundlich adsorption model, indicating that the adsorption of acid red 66 by modified vermiculite conforms more to the Langmuir adsorption model.

[0122] 3.11 Adsorption thermodynamics

[0123] A 250 mL conical flask was added with 50 mL of 20 mg / L acid red 66 dye and 50 mg of modified vermiculite (sodium vermiculite reacted with 50% C14-EG-C14 for 2 hours), and then the mixture was oscillated in a water bath constant temperature oscillator for 90 min at different temperatures, after which the upper liquid was taken out and the absorbance of the solution was measured, and the thermodynamic state functions △G, △S and △H were calculated by using the formula e , △S e and △H e . L The plot of lnK e vs. 1 / T was drawn, and the slope and intercept were used to obtain △S e and △H e .

[0124]

[0125]

[0126] ΔG e = ΔH e -TΔS L (3-7)

[0127] In the formula, R is the gas molar constant (8.314 J / mol·K); K e is the Langmuir adsorption constant; and T is the absolute temperature (K).

[0128] The experimental results are shown in Figure 15 , and the slope and intercept of the equation in the graph were used to obtain △H e and △S e . When the dye concentration was 20 mg / L, △H -1 =-10.177 kJ·mol e , △S -1 =0.604 kJ·mol e , and the △G of the adsorption reaction was less than zero, indicating that the adsorption reaction could proceed spontaneously. The entropy change △S e was greater than zero, indicating that the process of modified vermiculite adsorbing acid red 66 was an entropy-increasing reaction. The enthalpy change △H e was less than zero, and the adsorption reaction was an exothermic reaction. The increase in temperature was not conducive to the adsorption reaction, which was consistent with the experimental results.

[0129] 4. Conclusion

[0130] (1) When the sodium vermiculite is modified by using the cationic Gemini quaternary ammonium salt surfactant, the organic modified vermiculite with strong adsorption to anionic dyes can be obtained. The modification method in this embodiment is simple and easy to operate, and the adsorption of the modified vermiculite is related to the physicochemical properties of the surfactant.

[0131] (2) The method of the embodiment can improve the cation exchange capacity (CEC) of the original vermiculite after sodium modification, and the Gemini surfactant can improve the adsorption performance of the sodium-modified vermiculite on the non-degradable dye. The test results show that when C14-EG-C14 is used as the surface active modifier and the addition amount is 50wt%, the intercalated sodium-modified vermiculite has the strongest adsorption capacity, which can reach 95.05%.

[0132] (3) The adsorption kinetics proves that the adsorption process of the organic modified sodium-modified vermiculite is more in line with the pseudo-second-order reaction model, and chemical adsorption is dominant; the adsorption isotherm proves that the organic modified vermiculite is more in line with the Langmuir adsorption model for adsorbing acid red 66; and the adsorption thermodynamics proves that the adsorption process is an exothermic reaction.

[0133] (4) The raw materials used in the embodiment are cheap and easy to obtain, and a new Gemini quaternary ammonium salt surfactant is synthesized. The surfactant contains an ester bond and is environmentally degradable, and is not easy to cause secondary pollution.

Claims

1. Use of a surfactant-modified vermiculite, characterized in that, The application relates to a method for preparing a surfactant-modified vermiculite for adsorbing anionic dyes, which comprises the following steps: Step A: pretreating vermiculite to obtain vermiculite powder; Step B: adding the vermiculite powder into a sodium carbonate solution and stirring under heating, and then centrifuging after standing; Step C: dispersing the sodium-modified vermiculite into deionized water to obtain a sodium-modified vermiculite dispersion; Step D: adding a gemini surfactant into the sodium-modified vermiculite dispersion, stirring under heating to carry out a reaction, and then centrifuging to obtain a solid product; Step E: washing the solid product with deionized water until no foam is generated, and then drying and sieving to obtain the modified vermiculite; In step D, the gemini surfactant is prepared by the following steps: Step (D-1): mixing 1,4-cyclohexanediol and chloroacetyl chloride, and then carrying out a heating reflux reaction, and then cooling to room temperature to obtain a reaction system A; Step (D-2): adding distilled water into the reaction system A to hydrolyze residual chloroacetyl chloride, then adding a saturated sodium bicarbonate solution to adjust the pH to alkaline, and finally extracting the organic phase with dichloromethane; the extracted organic phase is spin-evaporated to obtain an intermediate; Step (D-3): mixing the intermediate, ethyl acetate and a tertiary amine, and then carrying out a heating reflux reaction, and then obtaining a reaction system B; the reaction system B is spin-evaporated to obtain a surfactant crude product; Step (D-4): dispersing the surfactant crude product into an organic solvent to carry out a heating reflux reaction, and then cooling and standing to obtain a crystal after filtration, and then drying the crystal to obtain the gemini surfactant; The tertiary amine is N,N-dimethyl dodecylamine, N,N-dimethyl tetradecylamine, N,N-dimethyl hexadecylamine or N,N-dimethyl octadecylamine; In step B, the mass concentration of the sodium carbonate solution is 1.0-2.0 mol / L; the mass ratio of the vermiculite powder to the sodium carbonate solution is 10-20:100; the temperature of the heating and stirring is 80-90 DEG C; the heating and stirring time is 6-8 h; the centrifuging is carried out after standing for 8-12 h; the drying temperature is 75-85 DEG C; the drying time is 8-10 h; and the sieving is carried out after grinding. In step (D-1), the volume ratio of chloroacetyl chloride to 1,4-cyclohexanediol is 1.5-2.0 mL / g; the heating reflux temperature is 90-100 DEG C; and the reflux reaction time is 4-5 h; 2. The use of a surfactant-modified vermiculite according to claim 1, characterized in that, In step (D-2), the volume ratio of the distilled water to chloroacetyl chloride in step (D-1) is (1-2):1; the pH is adjusted to 8-8.5 by adding the saturated sodium bicarbonate solution; when the organic phase is extracted with dichloromethane, the volume ratio of dichloromethane to chloroacetyl chloride in step (D-1) is 1:1, and the extraction is carried out for 3 times; and the temperature of the organic phase spin-evaporation is 20-30 DEG C; ​ In step (D-3), the mass ratio of the intermediate to the tertiary amine is 1:2.0-2.5; the volume ratio of ethyl acetate to the tertiary amine is (15-20):1; the temperature for heating and refluxing is 90-100°C, and the refluxing reaction time is 60-72 h; the rotary evaporation temperature of the reaction system B is 60-80°C, and the rotary evaporation time is 2-3 h; In step (D-4), the solid-liquid ratio of the surfactant crude product to the organic solvent is 1 g:(10-15) mL; the organic solvent is a mixture of chloroform and acetone in a volume ratio of 1:(2-3); the temperature for heating and refluxing is 55-65°C, and the refluxing reaction time is 30-50 min; the drying temperature of the crystal is 50-60°C, and the drying time is 3-5 h.

3. The use of a surfactant-modified vermiculite according to claim 1, characterized in that, In step A, the method for pretreating the vermiculite is as follows: the vermiculite is immersed in distilled water, and then ultrasonically cleaned in an ultrasonic cleaner for 20-30 min; after the ultrasonic cleaning, the vermiculite is filtered under suction and dried at a temperature of 80-90°C; after the drying, the vermiculite is ground and passed through a 200-mesh sieve.

4. The use of a surfactant-modified vermiculite according to claim 1, characterized in that, In step C, the mass ratio of the sodium-modified vermiculite to deionized water is 1-2:

100.

5. The use of a surfactant-modified vermiculite according to claim 1, characterized in that, In step D, the mass of the gemini surfactant is 25-100% of the mass of the sodium-modified vermiculite dispersion; the temperature for heating and stirring is 60-70°C, and the heating and stirring time is 2-12 h; in step E, the drying temperature is 80-85°C, and the drying time is 8-10 h; after grinding, the product is passed through a 200-mesh sieve.

6. The use of a surfactant-modified vermiculite according to claim 1, characterized in that, In step A, the method for pretreating the vermiculite is as follows: the vermiculite is immersed in distilled water, and then ultrasonically cleaned in an ultrasonic cleaner for 20 min; after the ultrasonic cleaning, the vermiculite is filtered under suction and dried at a temperature of 80°C; after the drying, the vermiculite is ground and passed through a 200-mesh sieve; In step B, the molar concentration of the sodium carbonate solution is 1.5 mol / L; the mass ratio of the vermiculite powder to the sodium carbonate solution is 15:100; the temperature for heating and stirring is 80°C, and the heating and stirring time is 8 h; after the heating and stirring, the product is left to stand for 12 h, and then centrifuged; the drying temperature is 80°C, and the drying time is 10 h; after grinding, the product is passed through a 200-mesh sieve; In step C, the mass ratio of the sodium-modified vermiculite to deionized water is 1:100; In step D, the mass of the gemini surfactant is 50% of the mass of the sodium-modified vermiculite dispersion; the temperature for heating and stirring is 60°C, and the heating and stirring time is 2 h; In step E, the drying temperature is 80°C, and the drying time is 8 h; after grinding, the product is passed through a 200-mesh sieve; In step D, the gemini surfactant is prepared by the following method: In step (D-1), 1,4-cyclohexanediol and chloroacetyl chloride are mixed, and then heated and refluxed at a temperature of 95°C for 5 h; the volume ratio of chloroacetyl chloride to the mass of 1,4-cyclohexanediol is 1.8 mL / g; after the reaction, the product is cooled to room temperature to obtain reaction system A; Step (D-2), distilled water was first added to the reaction system A to hydrolyze the residual chloroacetyl chloride, the ratio of the amount of distilled water to the volume of chloroacetyl chloride in step (D-1) was 1:1; then saturated sodium bicarbonate solution was added to adjust the pH to 8; finally, the organic phase was extracted with dichloromethane for 3 times, the ratio of the volume of dichloromethane to the volume of chloroacetyl chloride in step (D-1) was 1:1; the extracted organic phase was rotary evaporated at 25℃ to obtain the intermediate; Step (D-3), the intermediate, ethyl acetate and tetradecyldimethyl tertiary amine were mixed and heated to reflux at 95℃ for 72h, the ratio of the amount of intermediate to the amount of tertiary amine was 1:2.2, the ratio of the volume of ethyl acetate to the volume of tetradecyldimethyl tertiary amine was 15:1; after the reaction, reaction system B was obtained; reaction system B was rotary evaporated at 70℃ for 2h to obtain the crude surfactant; Step (D-4), the crude surfactant was redispersed in an organic solvent and heated to reflux at 60℃ for 30min, the solid-liquid ratio of the crude surfactant to the organic solvent was 1g:10mL, the organic solvent was a mixture of chloroform and acetone with a volume ratio of 1:2; after the reaction, the crystalline was obtained by cooling, standing and suction filtration, and the crystalline was dried at 60℃ for 3h to obtain the gemini surfactant.

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