CN104209106B - The Fe of 5-sulphosalicylic acid functionalization 3o 4magnetic nano-particle and synthetic method thereof and application - Google Patents

Abstract

The invention discloses a 5-sulfosalicylic acid functionalized Fe ₃ O ₄ magnetic nano particle, a synthesis method and an application thereof. The Fe ₃ O ₄ magnetic nanoparticles functionalized with 5-sulfosalicylic acid are coated with tetraethyl orthosilicate on the Fe ₃ O ₄ magnetic nanoparticles, and the obtained Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles are then And 5-sulfosalicyloyl chloride reaction. The particle synthesis method of the invention is simple, and the synthesized particles are spherical, uniform in size, good in dispersibility, and have good adsorption effect on selenium form, which provides a feasibility basis for studying trace selenium form in environmental water samples.

Description

5-sulfosalicylic acid functionalized Fe3O4 magnetic nanoparticles and its synthesis method and application

technical field

The invention relates to _Fe3O4 magnetic nanoparticles functionalized with ₅ -sulfosalicylic acid, a synthesis method and application thereof, and belongs to the technical field of nanomaterials.

Background technique

Magnetic particles (MPs) are usually composed of magnetic elements such as iron, nickel, cobalt and their oxides. Superparamagnetic iron oxide nanoparticles (Fe ₃ O ₄ , γ-Fe ₂ O ₃ ), as a new solid-phase extraction adsorbent, have attracted widespread attention in the field of atomic spectroscopy. Magnetic nanoparticles have the following advantages: easy surface modification, selective adsorption of analytes, and biocompatibility. Bare Fe ₃ O ₄ is easy to aggregate and has no selectivity for matrix adsorption in complex samples. Using SiO ₂ -coated Fe ₃ O ₄ nanoparticles prevents the surface of the particles from being oxidized and changes the magnetic properties, and at the same time provides further chemical functionalization. offers the possibility.

In the prior art, commonly used active functional groups for modifying the surface of magnetic nanoparticles include: carboxyl (-COOH), amino (-NH ₂ ), hydroxyl (-OH), mercapto (-SH), etc. In addition, conjugated structures can be used (such as polyaniline, etc.), large surface area (such as C18, etc.) and micellar properties for adsorption. At present, there is no report on the modification of magnetic nanoparticles with 5-sulfosalicylic acid, nor is there any report on the adsorption of selenium ions by magnetic nanoparticles modified with 5-sulfosalicylic acid.

Contents of the invention

The technical problem to be solved by the present invention is to provide a 5-sulfosalicylic acid functionalized Fe ₃ O ₄ magnetic nanoparticle and its synthesis method and application. The 5-sulfosalicylic acid functionalized Fe ₃ O ₄ magnetic nanoparticles synthesized by the method of the invention are spherical, uniform in size, good in dispersibility, and have good adsorption effect on the form of selenium.

The ₅ -sulfosalicylic acid functionalized _Fe3O4 magnetic nanoparticles of the present invention have a structural formula as follows:

in, Indicates Fe ₃ O ₄ magnetic nanoparticles.

The synthesis method of the ₅ -sulfosalicylic acid functionalized _Fe3O4 magnetic nanoparticles of the present invention is as follows: first adopt the co _- precipitation method to prepare _Fe3O4 magnetic nanoparticles, and then use ethyl orthosilicate to Fe ₃ O ₄ magnetic nanoparticles were coated to obtain Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles, and the obtained Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles were reacted with 5-sulfosalicyloyl chloride to obtain 5-sulfo Fe ₃ O ₄ magnetic nanoparticles functionalized with base salicylic acid; the 5-sulfosalicylic acid chloride is composed of dihydrate 5-sulfosalicylic acid and excess thionyl chloride in the presence of catalyst formamide The reaction is made.

A more specific method for synthesizing _Fe3O4 magnetic nanoparticles functionalized with ₅ -sulfosalicylic acid specifically includes the following steps:

1) Preparation of Fe ₃ O ₄ magnetic nanoparticles

Fe ₃ O ₄ magnetic nanoparticles were prepared by co-precipitation method;

2) Preparation of Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles

Take Fe ₃ O ₄ magnetic nanoparticles and place them in alcohol/water solution, add tetraethyl orthosilicate to it after ultrasonic dispersion, and adjust the pH of the solution to 4~5 or pH=9~10 under a protective atmosphere, and set the temperature at 70 Stirring and reacting at ~90°C for 1-16 hours, separating the reaction mixture using an external magnetic field, washing, and drying to obtain Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles;

3) Sulfur functionalization of Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles

3.1) Take 5-sulfosalicylic acid dihydrate and add excess thionyl chloride, then add catalyst formamide, react at 100-120°C for 5-12h, evaporate the excess thionyl chloride after cooling the reactant, and obtain 5-sulfosalicyl chloride;

3.2) Put Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles and excess 5-sulfosalicyl chloride into a reaction vessel, add catalyst pyridine, stir and react at 0-10°C for 12-24 hours, and separate the reaction mixture using an external magnetic field , washed and dried to obtain 5-sulfosalicylic acid functionalized Fe ₃ O ₄ magnetic nanoparticles.

In step 1) of the above synthesis method, the step of preparing Fe ₃ O ₄ magnetic nanoparticles by co-precipitation method is the same as the existing conventional technology, preferably including the following steps: according to Fe ³⁺ :Fe ²⁺ =1.3～2:1 The ratio of the amount of the substance weighs FeCl ₃ 6H ₂ O and FeCl ₂ 4H ₂ O into a reaction vessel, add deoxygenated water to dissolve them, raise the temperature to 60-90°C under a protective atmosphere, add ammonia water to adjust the pH= 9 to 10 minutes, heat preservation reaction for 30 to 120 minutes, the reaction mixture is separated by an external magnetic field, washed and dried to obtain Fe ₃ O ₄ magnetic nanoparticles. The amount of the above-mentioned deoxygenated water is usually calculated as 50-150 mL of deoxygenated water per 0.01 mol of iron salt (including ferrous iron salt and ferric iron salt).

In step 2) of the above synthesis method, the alcohol in the alcohol/water solution is glycerol or ethanol, the volume ratio of alcohol to water is preferably 0.6 to 1.5:1, and the amount of alcohol/water solution is usually 1gFe ₃ O ₄ magnetic Nanoparticles are calculated with 50-100mL alcohol/water solution. _In this step, the time for ultrasonic dispersion is the same as that of the prior art, usually ₁₀ to 50 min; The mass-volume ratio of ethyl acetate is: 1g: 2-5ml. After adding tetraethyl orthosilicate, adjust the pH of the solution to 4~5 or pH=9 to 10 and then carry out the reaction to obtain Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles, and adjust the pH of the solution to 4~5 Or the Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles obtained by the reaction at pH=9~10 have almost no difference in properties and performance; in general, use a weak acid to adjust the pH=4~5 of the solution, such as glacial acetic acid or Formic acid, etc.; adjust the pH of the solution to 9-10 with a weak base, such as ammonia or sodium bicarbonate.

In step 3.1) of the above synthesis method, usually, the molar ratio of 5-sulfosalicylic acid dihydrate and thionyl chloride is usually 1:25-72. The dosage of the catalyst formamide is usually 20-55% of the molar weight of 5-sulfosalicylic acid dihydrate. The reaction is usually carried out under oil bath conditions. In order to avoid bumping during the reaction, it is preferable to add several zeolites to the reaction system.

In step 3.2) of the above synthesis method, the mass ratio of Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles to 5-sulfosalicyloyl chloride is usually 1:3-6. The catalyst pyridine is anhydrous pyridine, specifically, the water in the pyridine can be removed according to the existing conventional method; the amount of the anhydrous pyridine is usually 5-5% of the mass of the Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles. 10%. The reaction is usually performed under ice bath conditions.

In the synthesis method of the present invention, the water used can be water that does not bring other impurities into the reaction system, such as sub-boiling water, double distilled water, deionized water, pure water, etc.; the protective atmosphere can be specifically Other protective atmospheres such as nitrogen, argon, helium; Described washing is usually water (as mentioned above, can be sub-boiling water, double distilled water, deionized water, pure water, etc.) and dehydrated alcohol to wash alternately; The drying described above usually adopts vacuum drying.

The 5-sulfosalicylic acid functionalized Fe ₃ O ₄ magnetic nanoparticles synthesized by the above method have a particle diameter of 10-15 nm, are spherical, uniform in size and good in dispersibility.

The present invention also includes the application of the above-mentioned sulfo-functionalized Fe ₃ O ₄ magnetic nanoparticles in the adsorption and separation of selenium forms, specifically for Se(VI), Se(IV), SeMet (selenomethionine) and SeCys ₂ (selenomethionine). Cystine) had better adsorption effects on the four forms of selenium, among which Se(IV) was the best. During adsorption, adjust the pH=1～5 (preferably pH=3～5, more preferably pH=4) of the liquid sample containing selenium ions or selenium compounds, and then add sulfo-functionalized Fe ₃ O ₄ magnetic nanoparticles Adsorption is carried out, and the adsorption can achieve a better effect when the adsorption time is ≥ 4 minutes, and it is preferably controlled to 5 minutes. When the total concentration of selenium ions in the liquid sample containing selenium ions or selenium compounds is ≤20ng·mL ^-1 , under the above conditions (pH of the liquid sample to be tested=4, adsorption time is 5min), the sulfo-functionalized When the added amount of Fe ₃ O ₄ magnetic nanoparticles is 10 mg, the selenium ions in the above samples can be completely adsorbed. If it is necessary to analyze the adsorbed selenium ions to determine the concentration of selenium ions in the sample, specifically during the analysis, place the Fe ₃ O ₄ magnetic nanoparticles adsorbed on the sulfo-functionalized selenium ions in a container, add Na ₂ CO ₃ The solution is ultrasonically eluted, and the ultrasonic time is ≥ 3 min, preferably 4 min, and then the supernatant is collected for detection of selenium content; the concentration of the Na ₂ CO ₃ solution is preferably 0.1-2.0 mol/L.

Furthermore, the present invention provides the application of sulfo-functionalized Fe ₃ O ₄ magnetic nanoparticles in the speciation analysis of selenium in liquid samples and the detection of trace selenium. The detection limit of trace selenium in the liquid sample is 0.17-0.54 ng/mL.

Compared with the prior art, the present invention provides a sulfo-functionalized _Fe3O4 magnetic nanoparticle modified by ₅ -sulfosalicyloyl chloride, the synthesis method of the particle is simple, and the synthesized particle is spherical , uniform in size, good dispersion, and good adsorption to selenium species.

Description of drawings

Fig. 1 is the infrared characterization spectrogram of MNPs, SMNPs and SSA-SMNPs magnetic nanoparticle that the embodiment of the present invention 1 makes, wherein, a is the infrared spectrum of MNPs magnetic nanoparticle, b is the infrared spectrum of SMNPs magnetic nanoparticle, c is the infrared spectrum of SSA-SMNPs magnetic nanoparticles;

Fig. 2 is the XRD figure of the SSA-SMNPs magnetic nanoparticle that the embodiment of the present invention 1 makes;

Fig. 3 is the TEM figure of the SSA-SMNPs magnetic nanoparticle that the embodiment of the present invention 1 makes;

Fig. 4 is the hysteresis loop of the SSA-SMNPs magnetic nanoparticle that the embodiment of the present invention 1 makes;

Figure 5 is the state of the SSA-SMNPs magnetic nanoparticles prepared in Example 1 of the present invention under the conditions of no magnetic field and a magnetic field, wherein a figure represents the state of the SSA-SMNPs magnetic nanoparticles under the condition of no magnetic field, and figure b represents the state of SSA -The state of SMNPs magnetic nanoparticles under the condition of magnetic field;

Figures 6 to 9 are the work of Se(VI), Se(IV), SeMet and SeCys ₂ in the mixed standard solution (the concentrations of Se(VI), Se(IV)SeMet and SeCys ₂ are all 5ng·mL ^-1 ) curve;

Fig. 10 is the electrophoresis figure of CE-ETAAS determination mixed standard solution and the selenium form in the fermented bean curd and fermented bean curd wastewater samples, wherein A is Se(VI), Se(IV)SeMet and SeCys that concentration is 5ng mL _- ¹ Electrophoresis of mixed standard solution; B is the electrophoresis of fermented bean curd wastewater sample; C is 4ng·mL ^-1 Se(VI), 3ng·mL ^-1 Se(IV), 2ng·mL ^-1 SeMet, 2ng·mL ^-1 Electrophoresis of the mixture of SeCys ₂ and bean curd wastewater samples; D is the electrophoresis of the bean curd emulsion; E is _6ng mL ^-1 Se(VI), 4ng mL ^-1 Se(IV), 3ng mL ^-1 SeMet , 4ng·mL ^-1 SeCys ₂ and the electrophoresis of the mixture of saprophyllum samples.

detailed description

The present invention will be further described below with specific examples, but the present invention is not limited to these examples.

In the following examples, the MNPs represent Fe ₃ O ₄ magnetic nanoparticles, the SMNPs represent Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles, and the SSA-SMNPs represent 5-sulfosalicylic acid functional Fe ₃ O ₄ magnetic nanoparticles.

Example 1

1) Preparation of Fe ₃ O ₄ magnetic nanoparticles (MNPs)

Accurately weigh 4.7300g FeCl ₃ 6H ₂ O and 1.9881g FeCl ₂ 4H ₂ O (Fe ³⁺ :Fe ²⁺ =1.75:1, n/n), dissolve them in 200mL deoxygenated water (deoxygenated sub-boiling water), Sonicate for 10 minutes, then transfer to a 500mL three-neck flask, stir at 85°C and 800rpm for 30min under nitrogen protection, and quickly add 20mL of ammonia water with a concentration of 25% to 28%, and the color of the solution turns black immediately (the pH of the solution at this time is 9.5) , matured for 30 minutes. The reaction mixture was cooled to room temperature, separated by an external magnetic field, washed three times alternately with sub-boiling water and absolute ethanol, dried under vacuum at 70 °C, and cooled to obtain MNPs.

2) Preparation of Fe ₃ O ₄ /SiO ₂ Magnetic Nanoparticles (SMNPs)

Dissolve 2 g of the above-prepared MNPs in 200 mL of glycerol and sub-boiling water (1:1, v/v) for ultrasonic dispersion for 30 min, add 10 mL of TEOS (tetraethyl orthosilicate, the amount of TEOS is calculated as 1 g of MNPs by adding 5 mL of TEOS), and transfer to In a 500mL three-neck flask, under nitrogen protection, adjust the pH to 4.5 with glacial acetic acid, stir the reaction at 800rpm at 90°C for 2h, cool the reaction mixture to room temperature, separate it with an external magnetic field, and wash it three times alternately with sub-boiling water and absolute ethanol. Vacuum drying at 70°C and cooling to obtain SMNPs.

3) Preparation of 5-sulfosalicylic acid functionalized Fe ₃ O ₄ magnetic nanoparticles (SSA-SMNPs)

3.1) Weigh 2.5g of SSA (5-sulfosalicylic acid dihydrate) in a 100mL three-necked flask, put 3 zeolites, add 40mL of SOCl ₂ and formamide accounting for 24% of the molar amount of SSA, and react in an oil bath at 110°C After 7 hours, the reactant was cooled to room temperature, and excess SOCl ₂ was evaporated at 55° C. with a rotary evaporator to obtain a light brown oily substance, which was 5-sulfosalicylic acid chloride. Through result characterization, it is determined that the structural formula of 5-sulfosalicyl chloride is as follows:

3.2) Put the above-prepared SMNPs and excess 5-sulfosalicylic acid chloride (the mass ratio of SMNPs and 5-sulfosalicylic acid chloride is 1:3) into a reaction solution container, and add 5% of the mass of SMNPs Anhydrous pyridine, stirred and reacted at 5-10°C for 24h, then separated by an external magnetic field, washed alternately with sub-boiling water and absolute ethanol three times, dried in vacuum at 70°C, and cooled to obtain SSA-SMNPs. The synthetic route of described SSA-SMNPs is as follows:

Characterize the SSA-SMNPs prepared above:

1. FT-IR spectrum

The SSA-SMNPs were characterized by FT-IR spectroscopy, which confirmed that the silanol and sulfo groups _were bonded to the surface of _Fe3O4 magnetic nanoparticles. The infrared characterization images of MNPs, SMNPs and SSA-SMNPs are shown in Fig. 1 . In MNPs, the peak at 586cm ^-1 is the characteristic absorption peak of Fe-O. The -OH on the surface of Fe ₃ O ₄ particles can bond with SiO ₂ to prevent Fe ₃ O ₄ from being oxidized and provide a platform for the next step of attaching functional groups. In SMNPs, the peak at 1080.12 cm ^-1 is the stretching vibration of Si-O, indicating that SiO ₂ is successfully bonded to the surface of Fe ₃ O ₄ . In SSA-SMNPs, C=O stretching vibration occurs at 1670cm ^-1 , the carbonyl is conjugated with the benzene ring, and the absorption shifts to low frequencies. At 1431.54cm ^-1 is the vibration of the benzene ring skeleton ^[27] , indicating the existence of the benzene ring. The peak at 1160cm ^-1 is -SO ₃ H stretching vibration absorption peak. It shows that SSA is successfully bonded to the surface of SMNPs magnetic nanoparticles.

2. Elemental analysis

Elemental analysis is the analysis that identifies the elements present in compounds and their amounts. The carbon, hydrogen, nitrogen, and sulfur in the measured substance are converted into carbon dioxide, water vapor, nitrogen, and sulfur dioxide respectively after catalytic oxidation-reduction. The oxygen in the substance to be tested is pyrolyzed to obtain carbon monoxide. Driven by the carrier gas, the mixed gas is effectively separated after passing through the chromatographic column, and each component is sequentially measured by the TCD detector of the elemental analyzer. In the experiment, the elements of C, S, and H in the SSA-SMNPs particles were analyzed, and the C content was 6.86%, and the S content was 2.618%. The calculated molar ratio of C to S was 7:1, which indicated that sulfosalicylic acid was successfully grafted onto _SiO2 -coated MNPs, and sulfo-functionalized SSA-SMNPs magnetic nanoparticles were synthesized.

3. XRD analysis

X-ray diffraction (XRD) is an effective method for studying the microstructure of crystalline substances and some amorphous substances. The XRD patterns of the SSA-SMNPs magnetic nanoparticles prepared in the above examples are shown in FIG. 2 . It can be seen from the figure that the diffraction peaks of SSA- _SMNPs appear at 2θ of 30.38°, 35.70°, 43.28°, _53.86 °, 57.36° and 62.86°, corresponding to (220), (311), (400), (422), (511) and (440) crystal planes. It is consistent with the standard Fe ₃ O ₄ crystal data (JCPDS No.65-3107). The peak position of each diffraction peak basically did not change, indicating that the spinel structure of Fe ₃ O ₄ nanoparticles was not changed during the process of surface coating SiO ₂ and sulfonic acid group functionalization. The magnetic nanoparticle spectrum of SSA-SMNPs was analyzed by software Jade5.0, and the average particle size of SSA-SMNPs was estimated to be 10.9nm.

4. TEM analysis

Transmission electron microscopy (TEM) can directly obtain the size and shape of particles. The TEM image of the SSA-SMNPs magnetic nanoparticles prepared in the above embodiment is shown in FIG. 3 . It can be seen from the figure that the average particle size of SSA-SMNPs prepared by this method is about 10.9nm, the size is uniform, spherical, and the dispersion is good. By coating _SiO2 and sulfo functionalization, the agglomeration between the magnetic nanoparticles is improved, the dispersion of the magnetic nanoparticles is improved, and the chemical stability of the magnetic nanoparticles is enhanced.

5. VSM analysis

The hysteresis loop reflects the response ability of magnetic materials to changes in magnetic field, and is an important curve to characterize the characteristics of magnetic materials. The magnetic properties of the SSA-SMNPs prepared in the above embodiment were studied by using a vibrating sample magnetometer (VSM), and the hysteresis loop is shown in FIG. 4 . The figure shows the hysteresis loop of SSA-SMNPs measured at 300K, and the saturation magnetization of SSA-SMNPs is 69.4emu·g ^-1 . During the magnetization process, the magnetization of SSA-SMNPs increases rapidly with the increase of the external magnetic field intensity, and quickly reaches saturation. When the external magnetic field intensity weakens, the magnetization intensity of SSA-SMNPs returns along the original magnetization path, presenting a reversible "S" type, without any hysteresis loop, indicating that SSA-SMNPs have no remanence and coercive force at 300K, and have good superparamagnetism. Fig. 5 is the state of the SSA-SMNPs magnetic nanoparticle that above-mentioned embodiment makes under the condition of no magnetic field and magnetic field, wherein a figure represents the state of SSA-SMNPs magnetic nanoparticle under the condition of no magnetic field, b figure represents SSA-SMNPs The state of magnetic nanoparticles in the presence of a magnetic field. Under the action of an external magnetic field, SSA-SMNPs adsorbed on the magnetic field side of the bottle wall, which also indicated that SSA-SMNPs had good magnetic properties.

Example 2

1) Preparation of MNPs

Accurately weigh FeCl ₃ 6H ₂ O and FeCl ₂ 4H ₂ O according to the amount ratio of Fe ³⁺ : Fe ²⁺ = 2:1, add deoxygenated water (deoxygenated water is deoxygenated sub-boiling water, deoxygenated water The dosage is calculated by using 100mL of deoxygenated water per 0.01mol of iron salt (including ferrous and ferric salts), ultrasonication for 5min, and then transferred to a 500mL three-necked flask, stirred at 1000rpm at 70°C for 10min under nitrogen protection, Quickly add ammonia water (concentration: 25%) to adjust the pH of the solution to 10, and ripen for 60 minutes. The reaction mixture was cooled to room temperature, separated by an external magnetic field, washed three times alternately with sub-boiling water and absolute ethanol, dried under vacuum at 60°C, and cooled to obtain MNPs;

2) Preparation of SMNPs

Dissolve 2 g of the above-prepared MNPs in 200 mL of ethanol and sub-boiling water (0.6:1, v/v) for ultrasonic dispersion for 10 min, add TEOS (the amount of TEOS is calculated by adding 2 mL of TEOS to 1 g of MNPs), transfer to a 500 mL three-necked flask, and nitrogen Protected, adjust the pH to 5 with glacial acetic acid, stir the reaction at 800rpm at 80°C for 10h, cool the reaction mixture to room temperature, separate with an external magnetic field, wash 3 times alternately with sub-boiling water and absolute ethanol, dry in vacuum at 70°C, and cool. Get SMNPs;

3) Preparation of SSA-SMNPs

3.1) Weigh 2.5g of SSA (5-sulfosalicylic acid dihydrate) in a 100mL three-neck flask, put 2 zeolites, add 50mL of SOCl ₂ and formamide accounting for 40% of the molar amount of SSA, and react in an oil bath at 110°C After 10 hours, the reactant was cooled to room temperature, and the excess SOCl ₂ was evaporated at 70°C with a rotary evaporator to obtain 5-sulfosalicyl chloride;

3.2) Put the above-prepared SMNPs and excess 5-sulfosalicyl chloride (the mass ratio of SMNPs and 5-sulfosalicyl chloride is 1:5) into a reaction solution container, and add 10% of the mass of SMNPs Anhydrous pyridine, stirred and reacted at 0-4°C for 18h, then separated by an external magnetic field, washed alternately with sub-boiling water and absolute ethanol three times, dried in vacuum at 70°C, and cooled to obtain SSA-SMNPs.

The average particle size of the SSA-SMNPs prepared in this example is 12.4 nm, and the saturation magnetization at 300K is 70.1 emu·g ^-1 .

Example 3

1) Preparation of MNPs

Accurately weigh FeCl ₃ 6H ₂ O and FeCl ₂ 4H ₂ O according to the amount ratio of Fe ³⁺ : Fe ²⁺ = 1.3:1, add deoxygenated water (deoxygenated water is deoxygenated sub-boiling water, deoxygenated water The dosage is calculated by using 50mL deoxygenated water per 0.01mol iron salt (including ferrous iron salt and ferric iron salt), ultrasonic for 30min, then transferred to a 500mL three-necked flask, stirred at 1000rpm at 90°C for 20min under nitrogen protection, Quickly add ammonia water (concentration: 28%) to adjust the pH of the solution to 9, and ripen for 120 minutes. The reaction mixture was cooled to room temperature, separated by an external magnetic field, washed three times alternately with sub-boiling water and absolute ethanol, dried under vacuum at 60°C, and cooled to obtain MNPs;

2) Preparation of SMNPs

Dissolve 3 g of the above-prepared MNPs in 200 mL of ethanol and sub-boiling water (1.5:1, v/v) for ultrasonic dispersion for 50 min, add TEOS (the amount of TEOS added is calculated by adding 3 mL TEOS to 1 g of MNPs), transfer it to a 500 mL three-necked flask, and nitrogen protection, adjust the pH to 9 with ammonia water, stir the reaction at 1000rpm at 70°C for 1h, cool the reaction mixture to room temperature, separate with an external magnetic field, alternately wash 3 times with sub-boiling water and absolute ethanol, dry at 60°C in vacuum, and cool to obtain SMNPs;

3) Preparation of SSA-SMNPs

3.1) Weigh 2.5g of SSA (5-sulfosalicylic acid dihydrate) in a 100mL three-necked flask, put 2 zeolites into it, add 50mL of SOCl ₂ and formamide accounting for 55% of the molar amount of SSA, and react in an oil bath at 100°C After 10 h, the reactant was cooled to room temperature, and the excess SOCl ₂ was evaporated with a rotary evaporator at 55°C to obtain 5-sulfosalicyl chloride;

3.2) Put the above-prepared SMNPs and excess 5-sulfosalicylic acid chloride (the mass ratio of SMNPs and 5-sulfosalicylic acid chloride is 1:6) into a reaction solution container, and add 8% of the mass of SMNPs Anhydrous pyridine, stirred and reacted at 0°C for 12h, then separated by an external magnetic field, washed alternately with sub-boiling water and absolute ethanol three times, dried in vacuum at 60°C, and cooled to obtain SSA-SMNPs.

The average particle size of the SSA-SMNPs prepared in this example is 11.5 nm, and its saturation magnetization is 71.2 emu·g ^-1 at 300K.

Example 4

1) Preparation of MNPs

Accurately weigh FeCl ₃ 6H ₂ O and FeCl ₂ 4H ₂ O according to the ratio of Fe ³⁺ : Fe ²⁺ = 1:1, and add 150 mL of deoxygenated water (deoxygenated water is deoxygenated sub-boiling water, deoxygenated The amount of water used is calculated by using 150mL of deoxygenated water per 0.01mol of iron salt (including ferrous and ferric salts), sonicated for 30min, then transferred to a 500mL three-necked flask, stirred at 1000rpm at 65°C under argon protection After 30 minutes, quickly add ammonia water to adjust the pH of the solution to 10, and ripen for 90 minutes. The reaction mixture was cooled to room temperature, separated by an external magnetic field, washed three times alternately with sub-boiling water and absolute ethanol, dried under vacuum at 80°C, and cooled to obtain MNPs;

2) Preparation of SMNPs

Dissolve 4 g of the above-prepared MNPs in 200 mL of ethanol and sub-boiling water (0.8:1, v/v) for ultrasonic dispersion for 10 min, add TEOS (the amount of TEOS added is calculated as 1 g of MNPs added to 5 mL TEOS), transfer to a 500 mL three-necked flask, and argon Gas protection, adjust the pH to 10 with ammonia water, stir the reaction at 1000rpm at 70°C for 16h, cool the reaction mixture to room temperature, separate with an external magnetic field, wash 3 times alternately with sub-boiling water and absolute ethanol, dry at 80°C in vacuum, and cool. Get SMNPs;

3) Preparation of SSA-SMNPs

3.1) Weigh 2.5g of SSA (5-sulfosalicylic acid dihydrate) in a 100mL three-necked flask, put 2 zeolites, add 30mL of SOCl ₂ and formamide accounting for 30% of the molar amount of SSA, and react in an oil bath at 120°C After 5h, the reactant was cooled to room temperature, and the excess SOCl ₂ was evaporated with a rotary evaporator at 55°C to obtain 5-sulfosalicyl chloride;

3.2) Put the above-prepared SMNPs and excess 5-sulfosalicyl chloride (the mass ratio of SMNPs and 5-sulfosalicyl chloride is 1:4) into a reaction solution container, and add 6% of the mass of SMNPs Anhydrous pyridine, stirred and reacted at 5°C for 20h, then separated by an external magnetic field, washed alternately with sub-boiling water and absolute ethanol three times, dried in vacuum at 50°C, and cooled to obtain SSA-SMNPs.

The average particle diameter of the SSA-SMNPs prepared in this example is 10.2nm, and the saturation magnetization at 300K is 75.1emu·g ^-1 .

Experimental example: the adsorption of the SSA-SMNPs magnetic nanoparticles prepared in Example 1 to a selenium-containing liquid sample was measured by CE-ETAAS coupling technology

1. Instruments and working conditions

TAS-986 Atomic Absorption Spectrophotometer (Beijing General Instrument Co., Ltd.), Selenium Hollow Cathode Lamp (Beijing Shuguang Electronic Light Source Instrument Co., Ltd.), SpectrumTwoFT-IR Infrared Spectrometer (PerkinElmer), RigakuD/max2500/pc Type X X-ray powder diffractometer (Japan Rigaku); MPMS-XL-7 superconducting quantum interference magnetic measurement system (U.S. QuantumDesign Company); JEM-2100 transmission electron microscope (Japan); PE2400II elemental analyzer (PerkinElmer); nebulizer device (see Deng Biyang etc. Talanta109 (2013) 128～132); rotameter (Jiangyin Keda Instrument Factory), HV-303P1 high-voltage electrophoresis power supply (Tianjin Shenghuo Technology Co., Ltd.), fused silica capillary (Hebei Yongnian Ruifeng Chromatography Company), DW-3 digital display stepless constant speed stirrer (Gongyi Yingyu Yuhua Instrument Factory), SYZ-550 quartz high-purity water distiller (Jiangsu Qinhua Glass Instrument Factory).

2. Reagents

FeCl ₂ 4H ₂ O, FeCl ₃ 6H ₂ O, tetraethylsilicate (TEOS), ammonia water, 5-sulfosalicylic acid dihydrate (SSA), NaOH, hydrochloric acid, sodium phosphate (Na ₃ PO ₄ 12H ₂ O) and disodium hydrogen phosphate (Na ₂ HPO ₄ 12H ₂ O) (Xilong Chemical Co., Ltd.), absolute ethanol, glacial acetic acid (Guangdong Guanghua Technology Co., Ltd.), glycerol, Na ₂ CO ₃ (Shantou Guanghua Chemical Factory), thionyl chloride (SOCl ₂ , Tianjin Zhiyuan Chemical Co., Ltd.), methanol (Shanghai Reagent Company), cetyltrimethylammonium bromide (CTAB, Hunan Xiangzhong Chemical Reagent Development Center).

The reagents used in the experiment were of analytical grade; the water used in the experiment was sub-boiling water.

3. Introduction of samples

The volume of the injected sample is affected by the injection time, injection pressure, sample properties and capillary length, etc. The experiment uses 0.04MPa argon pressure to introduce the sample solution into the capillary, the injection time is 10s, and the injection volume is about 0.5μL. Pretreatment of new fused silica capillary: rinse with CH ₃ OH for 30 min, then rinse with 0.1mol·L ^-1 NaOH for 40 min, and finally rinse with sub-boiling water for 10 min. Before each experiment, rinse with buffer solution for 8 minutes. After the experiment, rinse with 0.1mol·L ^-1 NaOH for 10 minutes and sub-boiling water for 15 minutes. Before the experiment, all samples were ultrasonically treated for 10 min to remove air bubbles and prevent flow break during the electrophoresis process. During the experiment, first fill the entire capillary with the buffer solution, then inject the sample under pressure, replace the buffer solution after the sample injection, and use ETAAS to detect according to the working conditions in Table 1 and Table 2 below.

Table 1 Working parameters of capillary electrophoresis and atomic absorption spectrometry

Table 2 Electrothermal atomic absorption heating program

4. Sample pretreatment

The water samples measured in the experiment were taken from the fermented bean curd and fermented bean curd wastewater from the same fermented bean curd factory in Guilin. After collection, let it stand for one day, then filter with filter paper, then filter with a sand core funnel, and finally filter with a 0.45 μm filter membrane. The filtered solution was stored for future use.

5. Solid phase extraction process

Take 10 mL of the sample solution (that is, the solution obtained after filtering at point 4 above) into a beaker, adjust the pH to 4 with 0.1 mol L- ¹ HCl solution, and add 10 mg of the SSA-SMNPs magnetic nanoparticles prepared in Example 1. The mixture was ultrasonically adsorbed for 5 minutes and separated by an external magnetic field. Then add 0.5mL Na ₂ CO ₃ solution (0.5mol·L ^-1 ) for elution, sonicate the new mixed solution for 4min, separate it by an external magnetic field, collect the supernatant with a PTEF tube, measure it with CE-ETAAS, repeat three times . Blank solutions were prepared as above.

6. Working curve, detection limit and repeatability

Under the above-mentioned experimental conditions of Table 1 and Table 2, the mixed standard solution of Se(VI), Se(IV), SeMet and SeCys ₂ with a concentration of 5ng mL ^-1 was continuously measured for 6 times, and the relative standard deviation (RSD , n=6) were 2.2%, 0.7%, 2.5% and 2.9%, respectively. The detection limits (3σ, n=11) of Se(VI), Se(IV), SeMet and SeCys ₂ were 0.18, 0.17, 0.54 and 0.49 ng·mL ^-1 , respectively. The linear range, enrichment factor EF (EF=slope of calibration curve after enrichment/slope of calibration curve before enrichment) and linear correlation coefficient are shown in Table 3, and the working curves are shown in Figures 6-10. Reuse is one of the important factors to evaluate the adsorptive materials, and the experiments show that the SSA-SMNPs particles can be reused 3 times for quantitative recovery experiments.

Table 3 Linear range and correlation coefficient (n=6)

7. Sample Analysis

Under the experimental conditions of the above-mentioned Table 1 and Table 2, Se(VI), Se(IV), SeMet and SeCys in the wastewater discharged from the fermented bean curd factory and the SeCys ₂ selenium form were measured with CE-ETAAS, as shown in Figure 10 shown. Compared with the mixed standard electrophoresis (curve A in Figure 10), it can be seen that there are two forms of selenium, Se(VI) and Se(IV), in the fermented bean curd wastewater, and their contents are 3.83ng·mL ^-1 and 2.62ng·mL ^-1 , respectively. There are four kinds of selenium forms Se(VI), Se(IV), SeMet and SeCys ₂ in the putrefaction emulsion, the contents of which are 6.39ng·mL ^-1 , 4.08ng·mL ^-1 , 2.77ng·mL ^-1 and 4ng·mL -1 respectively mL ^-1 . The content of inorganic selenium species in fermented bean curd wastewater or bean curd emulsion was higher than that of organic selenium species.

Under the experimental conditions of the above Table 1 and Table 2, the CE-ETAAS method was used to carry out the recovery experiment of Se(VI), Se(IV), SeMet and SeCys ₂ in the fermented bean curd wastewater and fermented bean curd, and the recovery rate was obtained The range was 99.14% to 104.5%, and the RSD range was 0.82% to 3.5%. The results are shown in Table 4 and Table 5.

Table 4 Se (IV) and Se (VI) analysis results and recovery rate in fermented bean curd wastewater and bean curd emulsion (n=6)

Water1 is the waste water of the fermented bean curd factory; Water2 is the fermented bean curd emulsion.

Table 5 SeMet and SeCys ₂ analysis results and recoveries in fermented bean curd wastewater and fermented bean curd emulsion (n=6)

Water1 is the waste water of the fermented bean curd factory; Water2 is the fermented bean curd emulsion.

8. Conclusion

The SSA-SMNPs magnetic nanoparticles prepared by the method described in the invention have a good adsorption effect on selenium ions, and a method for analyzing the form of selenium by CE-ETAAS is established. The enrichment factors of the prepared SSA-SMNPs magnetic nanoparticles to Se(VI), Se(IV), SeMet and SeCys ₂ were 12, 18, 21 and 29, respectively, and the detection limit was 0.17-0.54 ng·mL ^-1 . The obtained SSA-SMNPs magnetic nanoparticles were applied to the analysis of Se(VI), Se(IV), SeMet and SeCys ₂ in fermented bean curd liquid and fermented bean curd liquid, and the results were good. The SSA-SMNPs magnetic nanometer particle and method described in the invention provide a new analytical means for studying trace selenium forms in environmental water samples.

Claims (5)

1.5-sulfosalicylic acid functionalized Fe3O4The synthetic method of magnetic nanoparticles is characterized in that: the structural formula of the _{5 -} sulfosalicylic _acid functionalized _Fe3O4 magnetic nanoparticles is as follows: in, Indicates Fe ₃ O ₄ magnetic nanoparticles; The synthesis method of the Fe ₃ O ₄ magnetic nanoparticles functionalized with 5-sulfosalicylic acid is as follows: first, the Fe ₃ O ₄ magnetic nanoparticles are prepared by co-precipitation method, and then the Fe ₃ O 4 ₄ Magnetic nanoparticles are coated to obtain Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles, and the obtained Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles are reacted with 5-sulfosalicyl chloride to obtain 5-sulfosalicyl Acid-functionalized Fe ₃ O ₄ magnetic nanoparticles; the 5-sulfosalicylic acid chloride is prepared by reacting 5-sulfosalicylic acid dihydrate and excess thionyl chloride in the presence of catalyst formamide . 2. 5-sulfosalicylic acid functionalized Fe according to claim 1 ₃ O The synthetic method of O ₄ magnetic nanoparticles, it is characterized in that: specifically comprise the following steps: 1) Preparation of Fe ₃ O ₄ magnetic nanoparticles Fe ₃ O ₄ magnetic nanoparticles were prepared by co-precipitation method; 2) Preparation of Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles Take Fe ₃ O ₄ magnetic nanoparticles and place them in alcohol/water solution, add tetraethyl orthosilicate to it after ultrasonic dispersion, and adjust the pH of the solution to 4~5 or pH=9~10 under a protective atmosphere, and set the temperature at 70 Stirring and reacting at ~90°C for 1-16 hours, separating the reaction mixture using an external magnetic field, washing, and drying to obtain Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles; 3) Sulfur functionalization of Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles 3.1) Take 5-sulfosalicylic acid dihydrate and add excess thionyl chloride, then add catalyst formamide, react at 100-120°C for 5-12h, evaporate the excess thionyl chloride after cooling the reactant, and obtain 5-sulfosalicyl chloride; 3.2) Put Fe ₃ O ₄ /SiO ₂ magnetic nanoparticles and excess 5-sulfosalicyl chloride into a reaction vessel, add catalyst pyridine, stir and react at 0-10°C for 12-24 hours, and separate the reaction mixture using an external magnetic field , washed and dried to obtain 5-sulfosalicylic acid functionalized Fe ₃ O ₄ magnetic nanoparticles. 3. 5-sulfosalicylic acid functionalized Fe according to claim 2 ₃ O The synthetic method of O ₄ magnetic nanoparticles, it is characterized in that: in step 2), the alcohol in the alcohol/water solution is glycerol Alcohol or ethanol, the volume ratio of alcohol to water is 0.6-1.5:1. 4. 5-sulfosalicylic acid functionalized Fe according to claim ₂ O The synthetic method of O ₄ magnetic nanoparticles is characterized in that: in step 3.1), the consumption of catalyst formamide is dihydrate 5-sulfonic acid 20-55% of the molar weight of salicylic acid. 5. 5-sulfosalicylic acid functionalized Fe according to claim 2 ₃ O ₄ The synthetic method of magnetic nanoparticle is characterized in that: in step 3.2), catalyst pyridine is anhydrous pyridine, and its consumption is Fe 5-10% of the mass of ₃ O ₄ /SiO ₂ magnetic nanoparticles.