Preparation of porous organic material loaded with platinum nanoparticles and its application in colorimetric detection and removal of Hg 2+ in the title

Abstract

The present application relates to the technical field of colorimetric detection and removal of heavy metals, and particularly relates to a preparation of porous organic material loaded with platinum nanoparticles and application of the porous organic material in colorimetric detection and removal of Hg 2+ The porous organic material comprises a porous organic polymer loaded with platinum nanoparticles, and the average particle size of the platinum nanoparticles is 2.65 nm; the porous organic material loaded with platinum nanoparticles provided by the present application has Hg 2+ activated oxyenzyme-like activity. Based on the Hg 2+ activated oxyenzyme-like activity, a method for colorimetric detection of Hg 2+ is constructed. The porous organic material can also remove Hg 2+ efficiently, and the removal rate is as high as 99.4%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of colorimetric detection and removal of heavy metals, and particularly relates to preparation of porous organic material loaded with platinum nanoparticles and application of the porous organic material in colorimetric detection and removal of Hg 2+ . BACKGROUND

[0002] In recent years, heavy metal pollution has become a global environmental problem. Hg 2+ is a highly toxic and non-biodegradable heavy metal ion that can have toxic effects on various tissues and organs. Industrial discharge of Hg 2+ wastewater increases the deposition of mercury in lakes and soil, and Hg 2+ is absorbed and amplified by organisms, seriously threatening the ecological system and human health. Therefore, detection and removal of Hg 2+ is particularly important.

[0003] Among various analytical methods, including atomic absorption spectroscopy, inductively coupled plasma mass spectrometry, electrochemistry, fluorescence spectroscopy and colorimetry, colorimetry is increasingly favored due to its simplicity, low cost, speed and color change visible to the naked eye, and has been widely used in detection of toxic ions, biological small molecules and organic pollutants, etc. At present, colorimetry based on nano-enzyme has been used for sensitive detection of Hg 2+ . However, most nano-materials cannot effectively remove Hg 2+ , only realizing detection of Hg 2+ . Therefore, it is necessary to develop a dual-functional nano-enzyme for detection and removal of Hg 2+ . In previous reports, Hg 2+ can enhance or inhibit the catalytic activity of noble metal nano-enzymes (Au, Ag, Pt, etc.), and the catalysts of noble metals have been applied to detect Hg 2+ . It is known that the catalytic performance of noble metal nano-enzymes decreases due to serious aggregation phenomenon and poor stability. Notably, Pt NPs uniformly fixed usually have excellent catalytic performance. Therefore, loading Pt NPs on porous organic materials with customizable units is a new idea. SUMMARY

[0004] In view of the problems in the prior art, the present application provides a preparation of porous organic material loaded with platinum nanoparticles, which realizes uniform loading of platinum nanoparticles on the porous material by introducing thioether groups in the porous organic material to fix the platinum nanoparticles. Another object of the present application is to provide application of the porous organic polymer loaded with platinum nanoparticles in colorimetric detection and removal of Hg 2+ . Importantly, the constructed colorimetry can detect Hg 2+The application has the advantages of high specificity, wide detection range and rapidness. 2+ When the application is used to remove Hg

[0005] The application is realized by the following technical scheme:

[0006] A porous organic material loaded with platinum nanoparticles, the porous organic material comprising a porous organic polymer loaded with platinum nanoparticles, the platinum nanoparticles having an average particle size of 2.65 nm;

[0007] The porous organic polymer comprises the following chemical structure:

[0008] ;

[0009] The porous organic polymer is prepared by one-step condensation of pyrrole and 2,5-bis(methylthio) terephthaldehyde.

[0010] A preparation method of a porous organic material loaded with platinum nanoparticles, comprising the following steps: adding a porous organic polymer and polyvinylpyrrolidone into ethanol, deionized water and potassium chloroplatinate solution, ultrasonic mixing and stirring for 3 h, heating to react under vigorous stirring, the heating temperature is 70-90 DEG C, after the reaction is finished, the product is recovered by centrifugation, and the product is washed with a mixed solution of ethanol and water with a volume ratio of 1:1 for three times; vacuum drying at 60 DEG C for 24 h, and the porous organic material loaded with platinum nanoparticles is obtained.

[0011] Further, the preparation method of the porous organic polymer comprises the following steps:

[0012] (1) preparing 2,5-bis(methylthio) terephthaldehyde:

[0013] Firstly, 2,5-dibromoterephthaldehyde, DMF and NaSCH3 are added into a three-necked flask, stirring at room temperature under N2 atmosphere for 12 h; secondly, 1 mol / L hydrochloric acid is added into the product; then the product is extracted with chloroform for three times, and washed with deionized water for several times; the crude product is obtained by reduced pressure distillation, and the crude product is further purified by silica gel chromatography; finally, vacuum drying for 24 h, and the light orange solid is obtained;

[0014] (2) preparing a porous organic polymer (POP):

[0015] 2,5-bis(methylthio) terephthaldehyde, FeCl2.4H2O, propionic acid and pyrrole are added into a 50 ml three-necked flask under N2 atmosphere, refluxing at 150 DEG C for 48 h; the product is recovered by centrifugation, and then washed with methanol, 0.1 mol / L hydrochloric acid, tetrahydrofuran and deionized water for several times; vacuum drying at 60 DEG C for 24 h, and the black powder is obtained.

[0016] Further, the mass ratio of the polyvinylpyrrolidone and the porous organic polymer is 3:1.

[0017] Further, the concentration of the potassium chloroplatinate solution is 0.05-0.2 mol / L, preferably 0.1 mol / L.

[0018] Further, the volume ratio of the ethanol, deionized water and potassium chloroplatinate solution is 10:9:1.

[0019] Further, the heating temperature is 70-90°C, preferably 80°C.

[0020] The application also provides the application of the porous organic material loaded with platinum nanoparticles in colorimetric detection of Hg 2+ .

[0021] A method for colorimetric detection of Hg 2+ by the porous organic material loaded with platinum nanoparticles, comprising the following steps:

[0022] (1) adjusting the pH value of the NaAc-HAc buffer solution, wherein the pH value of the buffer solution is 2-8, preferably 4;

[0023] (2) preparing Hg 2+ solutions with different concentrations, wherein the concentration of the Hg 2+ solution is 0-1 mmol / L;

[0024] (3) adding the porous organic material loaded with platinum nanoparticles, the Hg 2+ solution of step (2) and 3,3',5,5'-tetramethylbenzidine (TMB) solution into the NaAc-HAc buffer solution, and reacting, wherein the reaction time is 30-180 s, preferably 120 s, and then measuring the absorbance value at 652 nm.

[0025] The application also provides the application of the porous organic material loaded with platinum nanoparticles in removal of Hg 2+ .

[0026] A method for removal of Hg 2+ by the porous organic material loaded with platinum nanoparticles, comprising the following steps:

[0027] (1) adjusting the pH value of the Hg 2+ solution, wherein the pH value is 4-9, preferably 7;

[0028] (2) preparing Hg 2+ solutions with different concentrations, wherein the concentration of the Hg 2+ solution is 60-100 ppm;

[0029] (3) Disperse the porous organic polymer loaded with platinum nanoparticles onto Hg 2+ The mixture is placed in an aqueous solution and then shaken for a period of time, from 0.5 to 12 hours, preferably 8 hours. The supernatant is separated by centrifugation, residual material is filtered off, and the Hg after adsorption is measured. 2+ concentration.

[0030] Compared with existing technical solutions, the technical features and beneficial effects of the present invention are as follows:

[0031] (1) The technical solution of the present invention successfully fixes nano-platinum particles on the polymer by introducing thioether groups on the porous organic polymer. The ultra-small nano-platinum particles are evenly distributed on the polymer and have good stability.

[0032] (2) The porous organic material supported on platinum nanoparticles provided by this invention has high catalytic activity. Compared with porous organic polymers alone, the catalytic activity is significantly higher when Hg is added. 2+ Afterwards, the catalytic activity of the porous organic polymer loaded with platinum nanoparticles was significantly increased by 11 times.

[0033] (3) The porous organic material loaded with platinum nanoparticles provided by the present invention has Hg 2+ Activated oxidase-like activity. Based on Hg 2+ Activated oxidase-like activity was used to construct a colorimetric detection method for Hg. 2+ This method, compared to other methods for detecting Hg... 2 + The method is simpler, requiring no addition of hydrogen peroxide or Hg. 2+ The substance that acts. Additionally, this method is used in the detection of Hg. 2+ It has the advantages of high specificity, wide linear range and short detection time.

[0034] (4) The porous organic material provided by the present invention can also efficiently remove Hg. 2+ The removal rate is as high as 99.4%. Attached Figure Description

[0035] Figure 1 Transmission electron microscopy (TEM) image of the porous organic material prepared in accordance with the present invention.

[0036] Figure 2 The infrared spectrum of the porous organic material prepared in the present invention.

[0037] Figure 3 Nitrogen adsorption-desorption diagram and pore size distribution diagram of the porous organic material prepared for the present invention.

[0038] Figure 4The porous organic material prepared in the implementation of the present application is used for detecting Hg 2+ The linear correction graph. DETAILED DESCRIPTION

[0039] The present application is further described below in conjunction with specific examples, but is not limited thereto.

[0040] Meanwhile, the experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0041] Example 1

[0042] The following gives a method for preparing a porous organic polymer loaded with platinum nanoparticles.

[0043] 1. Preparation of 2,5-bis(methylthio)terephthalaldehyde:

[0044] First, 2,5-dibromoterephthalaldehyde (0.2 g, 0.685 mmol), DMF (25 mL) and NaSCH3(200 μL, 3.26 mmol) were added to a three-necked flask, and stirred at room temperature for 12 h under N2atmosphere. Second, 1 mol / L hydrochloric acid (50 mL) was added to the product. Then the product was extracted with chloroform three times, and washed with deionized water several times. The crude product was obtained by reduced pressure distillation, and further purified by silica gel chromatography. Finally, the product was dried under vacuum for 24 h to obtain a light orange solid. 1 H NMR (400 MHz, CDCl3, δ), 10.33 (s, 2H), 7.76 (s, 2H), 2.50 (s, 6H).

[0045] 2. Preparation of porous organic polymer (POP):

[0046] 2,5-bis(methylthio)terephthalaldehyde (0.0549 g, 0.243 mmol), FeCl2.4H2O (0.137 g, 0.689 mmol), propionic acid (20 ml) and pyrrole (40 μL, 0.571 mmol) were added to a 50 ml three-necked flask under N2atmosphere, and refluxed at 150°C for 48 h. The product was recovered by centrifugation, and then washed with methanol, 0.1 mol / L hydrochloric acid, tetrahydrofuran and deionized water several times. The product was dried under vacuum at 60°C for 24 h to obtain a black powder.

[0047] 3. Preparation of porous organic material loaded with platinum nanoparticles (Pt / POP):

[0048] 10 mg of porous organic polymer and 30 mg of polyvinylpyrrolidone were added to a 20 mL glass bottle, followed by 5 mL of ethanol, 4.5 mL of deionized water, and 0.5 mL of potassium chloroplatinate solution (0.1 mol / L). The mixture was ultrasonically mixed and stirred for 3 h. The reaction was then carried out at 80 °C for 3 h under vigorous stirring. The product was recovered by centrifugation and washed three times with a 1:1 mixture of ethanol and water. The product was then vacuum dried at 60 °C for 24 h to obtain a black powder.

[0049] TEM images of Pt / POP prepared in this embodiment are shown ( Figure 1 Ultra-small Pt NPs are uniformly distributed within porous organic materials. For example... Figure 2 As shown, in the infrared spectrum of POP, the stretching vibration peak of -C=O in 2,5-bis(methylthio)terephthalaldehyde (1688 cm⁻¹) is visible. -1 The peak of the CH stretching vibration of methyl groups almost disappeared, and a peak appeared at 2918 cm⁻¹. -1 The presence of Pt / POP indicates successful POP preparation. The characteristic peaks of Pt / POP are almost identical to those of POP, suggesting that the POP structure remains intact even with the formation of Pt NPs. The pore size distribution of Pt / POP was examined using nitrogen adsorption-desorption isotherms. Figure 3 As shown, the specific surface area of ​​Pt / POP is 252.8 m². 2 / g, the main pore sizes of Pt / POP are concentrated in ~4.3 and ~4.49 nm.

[0050] Example 2

[0051] Add Pt / POP solution (200 μL, 20 mg / L) and Hg to NaAc-HAc buffer (1.4 mL, pH=4). 2+ A 2 mL mixture of 200 μL (10 μmol / L) buffer solution and 200 μL (100 μmol / L) TMB was prepared and reacted at room temperature for 2 minutes. The absorbance at 652 nm was measured using a UV-Vis spectrophotometer. Table 1 shows that only TMB or Hg were present in the buffer solution. 2+ When Pt / POP is present, the absorbance at 652 nm is close to 0, indicating that no reaction has occurred in the system. When Pt / POP is present, the absorbance at 652 nm is very small, indicating that TMB undergoes a weak oxidation reaction. However, when Pt / POP and Hg... 2+ When they coexist, there is a large absorbance value at 652nm, indicating that the coexistence of the two can catalyze the oxidation of TMB to turn blue.

[0052] Table 1. Absorbance values ​​of different systems at 652 nm

[0053]

[0054] As shown in Table 2, compared with pure Pt / POP, the addition of Hg... 2+ Subsequently, the catalytic performance of Pt / POP improved by 16 times, confirming that the Pt / POP catalyst has excellent Hg resistance. 2+ Enhanced oxidase-like activity. In contrast, POP with added Hg 2+ Subsequently, the catalytic performance did not show a significant improvement. This indicates that the introduction of nano-platinum particles significantly enhances the Hg content of porous organic materials. 2+ Activated oxidase-like activity.

[0055] Table 2 Comparison of Hg values ​​for POP and Pt / POP 2+ Enhanced catalytic performance

[0056]

[0057] Example 3

[0058] The following describes the colorimetric detection of Hg in porous organic polymers loaded with platinum nanoparticles prepared in this invention. 2+ The method.

[0059] Prepare a series of Hg concentrations 2+ For the blank experiment, Pt / POP solution (200 μL, 25 mg / L) and TMB (200 μL, 80 μmol / L) were added to NaAc-HAc buffer (1.6 mL, pH=4). After reacting at room temperature for 2 minutes, the absorbance (A0) at 652 nm was measured as a blank. Then, Pt / POP solution (200 μL, 25 mg / L), TMB (200 μL, 80 μmol / L), and Hg at different concentrations were added. 2+ Add 1.4 mL of NaAc-HAc buffer (pH=4), react at room temperature for 2 minutes, and record the absorbance value as A1. Calculate ΔA = A1 - A0, and plot ΔA against Hg. 2+ Concentration-to-Hg relationship curves. Under the condition of Pt / POP presence, different concentrations of Hg... 2+ It can catalyze the colorimetric reaction of TMB to varying degrees. For example... Figure 4 As shown, with Hg 2+ With increasing concentration, ΔA initially increases and then levels off. Within the range of 0.2–50 μmol / L, ΔA and Hg... 2+ The concentration showed a good linear relationship, and the detection limit was calculated to be 36.5 nmol / L.

[0060] Example 4

[0061] The following describes the effect of the porous organic polymer loaded with platinum nanoparticles prepared in this invention on Hg. 2+ Other interfering ions (Hg)2+ Pb 2+ Cd 2+ Al 3+ Ba 2+ Mg 2+ Zn 2+ Co 2+ Cu 2+ Na + ) to evaluate the selectivity of Pt / POP to Hg 2+ . As shown in Table 3, the response intensity of Hg 2+ at 652 nm is about 10 times of other interfering ions, which indicates that Pt / POP has good selectivity to Hg 2+ .

[0062] Table 3 Absorbance value changes of different cations

[0063]

[0064] Example 5

[0065] The Pt / POP prepared in the present application is used to detect Hg 2+ in actual water samples. The feasibility of the Pt / POP+TMB sensing platform for detecting Hg 2+ is verified in actual water samples (industrial wastewater). Different concentrations of Hg 2+ standard solution (5, 10 and 30 μmol / L) are added to the actual samples, and then the Pt / POP+TMB colorimetric platform is used for analysis. As shown in Table 4, the recovery rate is between 93.40% and 108.27%, which indicates that the Pt / POP+TMB colorimetric platform has good accuracy and practicability for detecting Hg 2+ in actual water samples.

[0066] Table 4 Experimental results of recovery rate of the method of the present application for different concentrations of Hg 2+ in actual water samples

[0067]

[0068] Example 6

[0069] The removal efficiency of Hg 2+ in aqueous solution by the porous organic material loaded with platinum nanoparticles prepared in the present application is given below.

[0070] The pH of the Hg 2+ aqueous solution is adjusted to 7 using HNO3 and NaOH. 1 mg of Pt / POP is dispersed in 5 mL of Hg 2+In aqueous solutions (60, 70, 80, 90, and 100 ppm). The mixture was shaken for 6 h, the supernatant was separated by centrifugation, residual material was filtered off, and the Hg after adsorption was measured. 2+ Concentration. Table 5 shows the effect of Pt / POP on different concentrations of Hg. 2+ The removal efficiency was high, with a maximum removal efficiency exceeding 99%. These results indicate that Pt / POP is a promising adsorbent for effectively capturing Hg from aqueous solutions. 2+ .

[0071] Table 5. Pt / POP as an adsorbent for Hg removal 2+ performance

[0072]

[0073] Adjust Hg using HNO3 and NaOH 2+ The pH of the aqueous solution is 4-9, and the preparation of Hg is also important. 2+ The initial concentration was 150 ppm. 1 mg Pt / POP was dispersed in 5 mL of Hg. 2+ In an aqueous solution, shake for 6 hours, separate the supernatant, filter off the residual material, and determine the Hg after adsorption. 2+ Concentration. As shown in Table 6, pH affects Hg. 2+ Adsorption has a significant impact, with the highest removal efficiency at pH=7.

[0074] Table 6 Effect of pH on removal efficiency

[0075]

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications or equivalent variations made using the above technical content without departing from the scope of the present invention shall still fall within the scope of the present invention and shall be included within the protection scope of the present invention.

Claims

1. Use of a porous organic material loaded with platinum nanoparticles for the colorimetric detection of Hg 2+ characterized in that: The porous organic material has Hg 2+ enhanced oxidase-like activity; thereby catalyzing the color reaction of 3,3',5,5'-tetramethylbenzidine (TMB), calculating the absorbance value change, and realizing the detection of Hg 2+ based on the absorbance value change; The porous organic material comprises a porous organic polymer loaded with platinum nanoparticles, the platinum nanoparticles are fixed by thioether groups in the porous organic polymer, and the average particle size of the platinum nanoparticles is 2.65 nm; The porous organic polymer comprises the following chemical structure: ； The porous organic polymer is prepared by one-step condensation of pyrrole and 2,5-bis(methylthio) terephthaldehyde.

2. The porous organic material loaded with platinum nanoparticles according to claim 1 for use in colorimetric detection of Hg 2+ characterized in that The preparation method of the porous organic material loaded with platinum nanoparticles comprises the following steps: adding the porous organic polymer and polyvinylpyrrolidone into ethanol, deionized water and a potassium chloroplatinate solution, ultrasonic mixing and stirring for 3 h, heating and reacting under vigorous stirring, centrifugal recovery of the product after the reaction is completed, washing with a mixed solution of ethanol and water in a volume ratio of 1:1 for three times, and vacuum drying at 60 DEG C for 24 h to obtain the porous organic material loaded with platinum nanoparticles.

3. The porous organic material loaded with platinum nanoparticles according to claim 2 for use in colorimetric detection of Hg 2+ characterized in that The preparation method of the porous organic polymer comprises the following steps: (1) preparing 2,5-bis(methylthio) terephthaldehyde: Firstly, 2,5-dibromoterephthaldehyde, DMF and NaSCH3 are added into a three-necked flask, stirring at room temperature under N2 atmosphere for 12 h; secondly, 1 mol / L hydrochloric acid is added into the product; then the product is extracted with chloroform for three times, and washed with deionized water for several times; the crude product is obtained by reduced pressure distillation, and further purified by silica gel chromatography; finally, vacuum drying for 24 h to obtain a light orange solid; (2) preparing the porous organic polymer POP: 2,5-bis(methylthio) terephthaldehyde, FeCl2.4H2O, propionic acid and pyrrole are added into a 50 ml three-necked flask under N2 atmosphere, refluxing at 150 DEG C for 48 h; the product is recovered by centrifugal recovery, and then washed with methanol, 0.1 mol / L hydrochloric acid, tetrahydrofuran and deionized water for several times; vacuum drying at 60 DEG C for 24 h to obtain a black powder.

4. The porous organic material loaded with platinum nanoparticles according to claim 2 for use in colorimetric detection of Hg 2+ characterized in that The mass ratio of the polyvinylpyrrolidone and the porous organic polymer is 3:1; The volume ratio of the ethanol, deionized water and the potassium chloroplatinate solution is 10:9:1; The concentration of the potassium chloroplatinate solution is 0.05-0.2 mol / L.

5. The porous organic material loaded with platinum nanoparticles according to claim 2 for use in colorimetric detection of Hg 2+ characterized in that The heating temperature is 70-90 DEG C.

6. The platinum-nanoparticle-loaded porous organic material according to claim 1 for use in colorimetric detection of Hg 2+ characterized in that Colorimetric detection of hg by porous organic materials loaded with platinum nanoparticles 2+ comprising the steps of: (1) adjusting the pH value of the NaAc-HAc buffer solution, and the pH value of the buffer solution is 2-8; (2) preparing Hg solutions with different concentrations 2+ The concentration of the Hg 2+ solution is 0-1 mmol / L; (3) The solution of the porous organic material loaded with platinum nanoparticles, the Hg 2+ solution of step (2) and the TMB solution were added to the NaAc-HAc buffer solution, and the reaction was carried out for 30-180 s. The absorbance value at 652 nm was measured after the reaction.

7. Use of a porous organic material loaded with platinum nanoparticles for the removal of Hg 2+ characterized in that: The porous organic material comprises a porous organic polymer loaded with platinum nanoparticles, the platinum nanoparticles are fixed by thioether groups in the porous organic polymer, and the average particle size of the platinum nanoparticles is 2.65 nm; The porous organic polymer comprises the following chemical structure: ； The porous organic polymer is prepared by one-step condensation of pyrrole and 2,5-bis(methylthio) terephthaldehyde. At pH = 7, maximum Hg 2+ removal efficiency.

8. The porous organo material loaded with platinum nanoparticles according to claim 7 for use in the removal of Hg 2+ characterized in that Porous organic material loaded with platinum nanoparticles for removal of Hg 2+ comprising the steps of: Adjusting Hg 2+ pH of the solution; the pH is between 4 and 9; Hg was prepared in different concentrations 2+ solutions; the Hg 2+ The concentration of the Hg solutions was 60-100 ppm; Dispersing platinum nanoparticle-loaded porous organic polymers into Hg 2+ aqueous solution, then the mixture was shaken for a period of time, the shaking time was 0.5-12 h, the supernatant was separated by centrifugation, the residual material was filtered out, and the Hg 2+ concentration after adsorption was determined.

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