Preparation method of nano zero-valent iron-based adsorption material

Abstract

The invention discloses a preparation method of a nano zero-valent iron-based adsorbing material, which comprises the following steps: (1) adding 100 mL of deionized water into a 500 mL four-necked flask, then adding 1.0% of TA, purging for 15 minutes by using N2, then adding 2.78 g of FeSO4. 7H2O, and stirring for 10-60 minutes at the speed of 300 revolutions per minute; (2) dropwise adding 50 mL of a 0.5 M NaBH4 aqueous solution into the flask in the step (1) at a speed of 1 drop / second to obtain a black precipitate, and continuously stirring for 30 min after dropwise adding is finished; then carrying out magnetic attraction separation on the black precipitate, and respectively washing with deionized water and ethanol for three times; (3) adding 60mL of deionized water into a 250mL three-neck bottle, and then adding 60mg of amine substances into the three-neck bottle; the particles in the step (2) are then added to the solution, and the pH is adjusted to 8-9. And stirring at a speed of 300 revolutions per minute for 30 minutes, and then carrying out magnetic separation. And alternately washing with deionized water and ethanol for 3 times, and drying in a vacuum oven at 60 DEG C for 12 hours to obtain the composite particles.

Description

Technical Field

[0001] The invention relates to the technical field of adsorbents, and in particular to a method for preparing a nano zero-valent iron-based adsorbent for adsorbing heavy metals. Technical Background

[0002] Industrial wastewater contains a large amount of toxic heavy metal ions, which will pose a great threat to the health of animals and plants if directly discharged into natural water bodies. Therefore, my country's "Comprehensive Wastewater Discharge Standard" (GB 8978-1996) has strict requirements on the concentration of heavy metal ions in industrial wastewater. So far, the solutions to the problem of heavy metal wastewater treatment include adsorption, reduction, membrane separation, ion exchange, chemical precipitation, etc. Among them, adsorption and reduction are the most economical and effective methods to solve this problem.

[0003] Nano zero-valent iron (nZVI) is considered to be a typical representative for the treatment of heavy metal-containing wastewater because of its simple preparation, high activity, easy separation, environmental friendliness, and reduction and adsorption properties. The high activity of nZVI can reduce highly toxic high-valent heavy metal ions to low-toxic low-valent ions. At the same time, its surface itself carries hydroxyl groups, which can fix some heavy metal ions on its surface through adsorption. However, nZVI itself has a large specific surface energy, which makes it easy to agglomerate, which reduces the specific surface area and charge transfer efficiency of the particles, affecting the reduction and adsorption properties of the particles. In addition, the high activity of nZVI makes it easy to be oxidized by air during application, forming an oxide layer, which reduces its reduction characteristics. In particular, it will be oxidized and inactivated during storage, so nZVI has certain requirements for storage conditions.

[0004] Usually, the modification of nZVI is only carried out to address its shortcomings of easy agglomeration and low adsorption during use, while ignoring its oxidation loss during storage, which not only increases the cost of nZVI, but also ignores its practical significance. Therefore, it is of great economic benefit and practical significance to develop an nZVI-based adsorbent for removing heavy metal ions that can be stably stored in the air. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing an nZVI-based adsorbent with air stability for removing heavy metal ions. The method enhances the air stability of nZVI nanoparticles by coating an antioxidant with antioxidant properties on the surface of the nZVI nanoparticles. In addition, amine substances are introduced on the surface of the nZVI nanoparticles through Michael addition and Schiff base reactions to enhance the adsorption effect of the composite particles. The preparation process of the present invention is simple, economical, and easy to implement in continuous industrial production. While ensuring that the composite particles have high adsorption properties, the particles are given excellent air stability, and have broad market application prospects.

[0006] To this end, the technical solution of the present invention is as follows:

[0007] A method for preparing a nanometer zero-valent iron-based adsorption material, comprising the following steps:

[0008] Step 1: Add 100 mL of deionized water to a 500 mL four-necked flask, then add 0.1-20% of an antioxidant, purge with N2 for 15-30 minutes, add 1-5 g of FeSO4·7H2O, and stir at 300 rpm for 10-60 minutes.

[0009] Step 2: Add 50 mL of 0.1-1.0 M NaBH4 aqueous solution into the flask at a rate of 1 drop / second to obtain a black precipitate, and continue stirring for 15-30 minutes after the addition is completed. Then, the black precipitate is separated by magnetic attraction and rinsed with deionized water and ethanol three times respectively.

[0010] Step 3: Add 60 mL of deionized water to a 250 mL three-necked flask, followed by 10-150 mg of amines. Then add the particles in step 2 to the solution and adjust the pH to 8-9. Stir at 300 rpm for 15-30 min and separate by magnetic attraction. Rinse with deionized water and ethanol alternately for 3 times, and dry in a vacuum oven at 60°C for 12 h.

[0011] Furthermore, the antioxidant used in step 1 is one of citric acid (CA), tannic acid (TA), cyclodextrin (CD) or sodium alginate (SA) or a mixture thereof in any proportion.

[0012] Furthermore, the amine substance used in step three is one of 3-aminopropyltriethoxysilane (KH550), polyethyleneimine (PEI), polyaniline (PANI), chitosan (CS) or pyrrole (Py) or a mixture thereof in any proportion.

[0013] The present invention has the following advantages and beneficial effects:

[0014] 1. The nano zero-valent iron-based adsorption material for air stability of the present invention has a simple preparation method, low preparation cost, high repeatability, and is easy to realize industrial production.

[0015] 2. The nanometer zero-valent iron-based adsorption material for air stability of the present invention has a high removal rate for heavy metal ions, excellent antioxidant properties, and broad market application prospects.

[0016] Specific implementation methods

[0017] To realize the above-mentioned technology, the present invention is described below in combination with the embodiments of the present invention through drawings and embodiments. However, the embodiments described in the present invention are only part, not all embodiments. The technical solutions and methods for improving the present invention all belong to the protection scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a surface SEM image of the air-stable modified nano zero-valent iron-based adsorption material obtained in Example 4 of the present invention.

[0019] Figure 2 This is a performance test chart of the air-stable modified nano zero-valent iron-based adsorption material obtained in Examples 1 to 5 of the present invention for removing Cr(VI). Different modified nanoparticles are recorded as Fe-TA(x%)-PEI, wherein x% (molar ratio of TA to Fe) is the TA content.

[0020] Figure 3 This is a test diagram of the long-term storage stability of the air-stable modified nano zero-valent iron-based adsorption material obtained in Example 4 of the present invention under dry air conditions. DETAILED DESCRIPTION

[0021] Examples 1-5

[0022] Add 100 mL of deionized water to a 500 mL four-necked flask, followed by 0.1-20% antioxidant (tannic acid content see Table 1). After purging with N2 for 15-30 min, add 2.78 g of FeSO4·7H2O and stir at 300 rpm for 15 min; drip 50 mL of 0.4 M NaBH4 aqueous solution into the flask at a rate of 1 drop / second to obtain a black precipitate, and continue stirring for 30 min after the addition. Then separate the black precipitate by magnetic absorption, and rinse it with deionized water and ethanol for 3 times respectively; add 60 mL of deionized water to a 250 mL three-necked flask, followed by 60 mg of PEI. Then add the particles in step 2 to the solution and adjust the pH to 8-9. Stir at 300 rpm for 10 min and then separate by magnetic absorption. After rinsing with deionized water and ethanol alternately 3 times, dry it in a vacuum oven at 60°C for 12 h to obtain an air-stable modified nano zero-valent iron-based adsorption material. The ability of the adsorbent to remove heavy metals was tested in a 20 mg / L Cr(VI) solution. The results are as follows:

[0023] Table 1 Removal rate of Cr(VI) of the formula and composite particles of Examples 1-5

[0024]

[0025]

[0026] Comparative Example 1

[0027] Add 100mL of deionized water to a 500mL four-necked flask, followed by 1.0% CA. After purging with N2 for 15 to 30 minutes, add 2.78g of FeSO4·7H2O and stir at 300 rpm for 15 minutes; drip 50mL of 0.4M NaBH4 aqueous solution into the flask at a rate of 1 drop / second to obtain black particles. Continue stirring for 30 minutes after the addition. Then separate the black precipitate by magnetic absorption and rinse it with deionized water and ethanol three times respectively for use; add 60mL of deionized water to a 250mL three-necked flask, followed by 60mg of PEI. Then add the above black particles to the solution and adjust the pH to 8-9. Stir at 300 rpm for 10 minutes and then separate by magnetic absorption. After rinsing alternately with deionized water and ethanol three times, dry it in a vacuum oven at 60℃ for 12 hours. The ability of the adsorbent to remove heavy metals was tested in a 20mg / L Cr(VI) solution, and the results are as follows:

[0028] Comparative Example CA% / (CA / Fe) PEI(mg) Reaction time (min) Cr(VI) removal rate (%) 1 1.0 60 10 94.18

[0029] Comparative Example 2

[0030] Add 100mL of deionized water to a 500mL four-necked flask, followed by 1.0% TA. After purging with N2 for 15 to 30 minutes, add 2.78g of FeSO4·7H2O and stir at 300 rpm for 15 minutes; drip 50mL of 0.4M NaBH4 aqueous solution into the flask at a rate of 1 drop / second to obtain black particles. Continue stirring for 30 minutes after the addition. Then separate the black precipitate by magnetic absorption and rinse it with deionized water and ethanol three times respectively for use; add 60mL of deionized water to a 250mL three-necked flask, followed by 60mg of PANI. Then add the above black particles to the solution and adjust the pH to 8-9. Stir at 300 rpm for 10 minutes and then separate by magnetic absorption. After rinsing alternately with deionized water and ethanol three times, dry it in a vacuum oven at 60℃ for 12 hours. The ability of the adsorbent to remove heavy metals was tested in a 20mg / L Cr(VI) solution, and the results are as follows:

[0031] Comparative Example TA% / (TA / Fe) PANI (mg) Reaction time (min) Cr(VI) removal rate (%) 2 1.0 60 10 91.64

[0032] Determination method of Cr(VI) removal rate

[0033] At pH = 3 and room temperature, 0.05 g of particles were added to 100 mL of 20 mg / L chromium-containing wastewater, and the mixture was shaken continuously for 2 h. The filtrate was collected through a 0.1 μm filter membrane at certain time intervals. The concentration of Cr(VI) in the filtrate was determined by UV spectrophotometer using diphenylcarbohydrazide as the complexing agent.

[0034]

[0035] Among them, C0 (mg / L) and C t (mg / L) are the initial concentration and the concentration at time t, respectively.

[0036] The test results show that the nano zero-valent iron-based composite particles modified by TA and PEI have a high removal ability for Cr(VI), indicating that the composite particles have important value in the application of heavy metal ions in the removal system.

[0037] In order to evaluate the long-term air stability of the composite particles, the present invention placed the composite particles in air conditions for 30 days and took samples every 5 days to test their Cr(VI) removal effect. Figure 3 shown.

Claims

1. A method for preparing a nanometer zero-valent iron-based adsorption material, It is characterized in that The following steps are involved: 1) Add 100 mL of deionized water to a 500 mL four-necked flask, followed by 0.1-20% of an antioxidant. 2 After purging for 15 to 30 minutes, add 1 to 5 g FeSO 4 7H 2 O, stirring at 300 rpm for 10 to 60 min. 2) Add 50 mL 0.1-1.0 M NaBH 4 The aqueous solution was dripped into the flask at a rate of 1 drop / second to obtain a black precipitate, and stirring was continued for 15 to 30 minutes after the dripping was completed. The black precipitate was then separated by magnetic attraction and rinsed with deionized water and ethanol three times respectively. 3) Add 60 mL of deionized water to a 250 mL three-necked flask, followed by 10-150 mg of amines. Then add the particles in step 2 to the solution and adjust the pH to 8-9. Stir at 300 rpm for 15-30 min and separate by magnetic attraction. Rinse with deionized water and ethanol alternately for 3 times, and dry in a vacuum oven at 60°C for 12 h.

2. The preparation method according to claim 1, Features: The antioxidant used in step 1) is one of citric acid (CA), tannic acid (TA), cyclodextrin (CD) or sodium alginate (SA) or a mixture thereof in any proportion.

3. The preparation method according to claim 1, Features: The amine substance used in step 3) is one of 3-aminopropyltriethoxysilane (KH550), polyethyleneimine (PEI), polyaniline (PANI), chitosan (CS) or pyrrole (Py) or a mixture thereof in any proportion.

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