CN113477937B - Method for green synthesis of composite nano iron particles and application thereof - Google Patents
Method for green synthesis of composite nano iron particles and application thereof Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
- B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
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- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/28—Treatment of water, waste water, or sewage by sorption
- C02F1/281—Treatment of water, waste water, or sewage by sorption using inorganic sorbents
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/70—Treatment of water, waste water, or sewage by reduction
- C02F1/705—Reduction by metals
Abstract
The invention discloses a method for green synthesis of composite nano iron particles and application thereof, wherein the method comprises the following steps: 1) Preparing a lutein solution; 2) Dripping the lutein solution into a soluble divalent or trivalent ferric salt solution while stirring, controlling the temperature to be 30-65 ℃, reacting for 5-60min to obtain a nano-iron suspension, and introducing nitrogen into the solution all the time in the reaction process; 3) Carrying out suction filtration on the nano-iron suspension, sequentially cleaning the obtained particles by using deionized water and absolute ethyl alcohol, carrying out vacuum drying for 8-24 hours at 35-60 ℃, and grinding to obtain nano-iron particles; 4) Preparing a coating solution, and then adding the nano-iron particles into the coating solution for coating to obtain the composite nano-iron particles. In the synthetic method of the composite nano-iron particles, the zero-valent nano-iron is prepared by adopting nontoxic lutein as a reducing agent, so that the method does not cause environmental pollution, has low cost and is a green and environment-friendly synthetic process.
Description
Technical Field
The invention relates to the technical field of chemical synthesis, in particular to a method for green synthesis of composite nano iron particles and application thereof.
Background
The nano zero-valent iron is a reducing agent with strong chemical reducibility, and has excellent adsorption performance and high reduction activity due to the specific surface effect and small-size effect, so the nano zero-valent iron has huge application prospect.
For example, the nanoscale zero-valent iron can be used to remove high-valent ions by reduction to achieve purification. Typically, the sewage from electroplating, printing and dyeing industries contains Cr 6+ It has carcinogenic and teratogenic effects, and can utilize nano zero-valent iron to remove toxic Cr 6+ Reduced to nontoxic Cr 3+ So as to realize sewage purification.
The preparation method of the nano zero-valent iron can be divided into a physical method and a chemical method, wherein the physical method comprises an evaporation condensation method, a sputtering method, a high-energy mechanical ball milling method and the like; the chemical methods are mainly classified into liquid-phase chemical reduction methods, active hydrogen-molten metal reaction methods, gas-phase chemical reduction methods, and gas-phase thermal decomposition methods, and the commonly used chemical reduction methods are those in which iron salts or oxides thereof are reduced with a reducing agent to produce nanoscale zero-valent iron particles. The reducing agent commonly used at present is KBH 4 、NaBH 4 、N 2 H 4 However, these reducing agents are toxic and cause environmental pollution. Another one isOn the other hand, the nano zero-valent iron has small particle size and high surface activity, so the nano zero-valent iron is easy to oxidize and deteriorate and is not beneficial to storage, and in addition, the nano zero-valent iron is easy to agglomerate when being used, so the nano zero-valent iron can be used after being usually matched with a dispersing agent or prepared into a dispersing solution. For example, patent CN106180755A discloses a method for green synthesis of nano zero-valent iron by using water hyacinth extract and application thereof, which can overcome the disadvantage that the reducing agent used in the conventional method has toxicity, but does not provide a corresponding solution to the disadvantage that nano zero-valent iron is easy to agglomerate and inconvenient to store.
Therefore, there is a need to provide a more reliable solution.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a method for green synthesis of composite nano-iron particles and applications thereof, aiming at the defects in the prior art.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a green synthesis method of composite nano-iron particles comprises the following steps:
1) Dissolving lutein in ethyl acetate, and stirring to completely dissolve to obtain lutein solution;
2) Dripping the lutein solution into a soluble divalent or trivalent ferric salt solution while stirring, controlling the temperature to be 30-65 ℃, reacting for 5-60min to obtain a nano-iron suspension, and introducing nitrogen into the solution all the time in the reaction process;
3) Carrying out suction filtration on the nano-iron suspension, sequentially cleaning the obtained particles by using deionized water and absolute ethyl alcohol, carrying out vacuum drying for 8-24 hours at 35-60 ℃, and grinding to obtain nano-iron particles;
4) Preparing a coating solution, and then adding the nano-iron particles into the coating solution for coating to obtain the composite nano-iron particles.
Preferably, the soluble ferrous or ferric salt solution is any one or combination of ferrous chloride, ferrous sulfate, ferric trichloride and ferric sulfate solution;
the concentration of solute in the soluble bivalent or trivalent ferric salt solution is 0.05-0.3mol/L.
Preferably, the concentration of lutein in the lutein solution is 0.25-5g/L.
Preferably, the raw materials of the coating solution in the step 4) include montmorillonite, water-soluble starch, deionized water, hydroxypropyl methylcellulose and ethanol.
Preferably, the preparation method of the coating solution in the step 4) comprises:
a. preparing a solution A: adding water-soluble starch into deionized water, stirring at 35-65 deg.C until completely dissolved to obtain starch solution, pulverizing montmorillonite, adding into the starch solution, stirring, and keeping stirring;
b. preparing a solution B: adding deionized water into ethanol to obtain ethanol solution, adding hydroxypropyl methylcellulose into the ethanol solution, and stirring to dissolve completely.
Preferably, in the step 4), the method for coating the nano-iron particles specifically includes:
4-1) adding the nano iron particles into the solution A, reacting for 5-45min under the condition of keeping stirring, standing for 3-10min, filtering, drying filter residues in vacuum, and purging with nitrogen to obtain intermediate particles;
4-2) adding the intermediate particles into the solution B, stirring for 3-20min, standing for 2-10min, filtering, taking filter residues, drying in vacuum, and purging with nitrogen to obtain the composite nano iron particles.
Preferably, the mass fraction of the starch in the solution A is 5-20%, and the mass fraction of the montmorillonite is 5-25%.
Preferably, the methyl group content of the hydroxypropyl methylcellulose is 25-30% and the hydroxypropyl content is 6-12%.
Preferably, the mass fraction of the ethanol solution is 40-65%.
Preferably, the particle size of the montmorillonite is 0.1-0.25mm.
In the present invention, lutein is used as reducing agent from Fe 2+ 、Fe 3+ The zero-valent nano-iron is prepared by reduction in a liquid phase system, and the lutein is a natural plant extract and is used in vegetables, fruits, flowers and other plantsWidely existing in the field, has strong reducibility and has a chemical formula of C 40 H 56 O 2 Has no toxicity and environmental pollution, is a green and environment-friendly raw material, and has rich sources and low price. The lutein is hardly dissolved in water, but is dissolved in some organic solvents, such as ethanol, acetone, ethyl acetate and the like, the lutein has higher solubility in the ethyl acetate (5000-8000 mg/L may be reached at room temperature), the ethyl acetate is also a non-toxic or low-toxicity compound, the lutein is easy to hydrolyze in water to generate acetic acid and ethanol, and the environment is not polluted. The lutein has good reduction effect on high-valence iron, and the method adopts natural pollution-free lutein as a reducing agent to prepare the zero-valence nano-iron, does not cause environmental pollution, has low cost, and is a green and environment-friendly synthesis process.
The zero-valent nano-iron has strong reducibility and poor stability, is not beneficial to storage, has small particle size, is easy to agglomerate and can cause negative effects on the use of the zero-valent nano-iron. The invention further coats the nano-iron particles to form a shell outside the nano-iron particles, so that the defects can be overcome, the nano-iron particles inside the nano-iron particles are protected, the stability of the nano-iron particles is enhanced, and the agglomeration of the nano-iron particles can be reduced.
Specifically, in the invention, the nano iron particles are adsorbed by taking montmorillonite particles as a carrier, and the nano iron particles can be firmly adsorbed on the montmorillonite by water-soluble starch, so that the montmorillonite and the nano iron particles form stable intermediate particles; and then a layer of hydroxypropyl methyl cellulose protective film is formed outside the intermediate particles by the film forming property of the hydroxypropyl methyl cellulose. The hydroxypropyl methyl cellulose protective film can well protect the nano-iron particles on the inner layer, prevent the nano-iron particles from being oxidized, improve the stability of the composite nano-iron particles and facilitate storage. And the hydroxypropyl methyl cellulose is easy to dissolve in water, and the outer protective film can be dissolved by water when the hydroxypropyl methyl cellulose is used, so that the functional particles in the hydroxypropyl methyl cellulose can be exposed to realize related effects. Montmorillonite can be used as a load carrier of the nano-iron particles on one hand, and also has good water absorption performance on the other hand, so that the effect of moisture protection can be achieved, and further montmorillonite has water swelling performance and strong adsorbability, so that the composite nano-iron particles have more abundant functions, and the application of the composite nano-iron particles is convenient to expand.
The invention also provides an application of the composite nano iron particles as a water purifying agent or a material for preparing the water purifying agent.
The composite nano iron particles provided by the invention have rich functions and are very suitable for being used as a water purifying agent. The nano iron particles have strong reducibility, and can be used for removing some high-valence ions in water through reduction reaction, such as toxic hexavalent chromium (chromium exists mainly as trivalent chromium and hexavalent chromium which is a carcinogenic toxic substance and is a main source and electroplating and printing and dyeing wastewater) which can be reduced into pollution-free trivalent chromium through the nano iron particles. When the composite nano iron particles are used, the composite nano iron particles are added into sewage to be treated, and the hydroxypropyl methyl cellulose protective film can be quickly dissolved, so that internal montmorillonite and nano iron particles are exposed; montmorillonite expands after absorbing water (the volume can be increased by several times to more than ten times), so that gaps among nano-iron particles loaded on montmorillonite are increased by times, so that the nano-iron particles can be in more sufficient contact with sewage and fully react with high-valence ions in the sewage, and the utilization rate and the treatment efficiency of the nano-iron particles are greatly improved; furthermore, the montmorillonite has strong adsorption performance, can effectively adsorb pollutants in sewage, and improves the purification efficiency; montmorillonite and nano-iron particles can generate a synergistic enhancement effect in many aspects, and the purification performance of the composite nano-iron particles is improved.
The composite nano-iron particles provided by the invention can be used as a water purifying agent alone or together with other water purifying agents, and are specifically selected according to the sewage components to be treated, and the dosage of the composite nano-iron particles also needs to be selected according to the treated objects.
The invention has the beneficial effects that:
in the synthetic method of the composite nano-iron particles, the zero-valent nano-iron is prepared by adopting nontoxic lutein as a reducing agent, so that the method does not cause environmental pollution, has low cost and is a green and environment-friendly synthetic process;
the composite nano-iron particles can be used as a water purifying agent or a material for preparing the water purifying agent, and can be used for removing some high-valence ions (such as hexavalent chromium) in water through reduction reaction by virtue of the strong reducibility of the nano-iron particles;
according to the invention, the nano iron particles can be prevented from being oxidized by coating the hydroxypropyl methyl cellulose protective film, the stability of the composite nano iron particles can be improved, and the composite nano iron particles are convenient to store;
according to the invention, the montmorillonite loaded nano iron particles can effectively prevent the nano iron particles from agglomerating, so that the function of the nano iron particles can be realized conveniently, and the water absorption expansibility of the montmorillonite can enable the nano iron particles to be in contact reaction with high-valence ions in water more fully, thereby improving the purification effect.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with examples are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms than those specifically described herein, and it will be apparent to those skilled in the art that many more modifications are possible without departing from the spirit and scope of the invention.
Reagents and instruments used in the examples are all conventional in the art and are not specifically described. The experimental procedures, in which specific conditions are not indicated in the examples, are generally carried out according to conventional conditions, such as those in the literature, in books, or as recommended by the manufacturer of the kits. The reagents used in the examples are all commercially available.
Example 1
A green synthesis method of composite nano-iron particles comprises the following steps:
1) Dissolving lutein in ethyl acetate, and stirring to completely dissolve to obtain lutein solution;
wherein the concentration of lutein in the lutein solution is 1g/L.
2) Dropwise adding the lutein solution into the soluble divalent or trivalent ferric salt solution while stirring, controlling the temperature at 45 ℃, reacting for 15min to obtain a nano-iron suspension, and introducing nitrogen into the solution all the time in the reaction process;
wherein the soluble ferrous salt solution or ferric salt solution is 0.1mol/L ferrous chloride solution.
3) And (3) carrying out suction filtration on the nano-iron suspension, sequentially cleaning the obtained particles by using deionized water and absolute ethyl alcohol, carrying out vacuum drying at 45 ℃ for 12 hours, and grinding to obtain the nano-iron particles.
4) Preparing a coating solution, and then adding the nano-iron particles into the coating solution for coating to obtain the composite nano-iron particles, wherein the preparation method comprises the following specific steps:
4-1) preparing a coating solution:
a. preparing a solution A: adding water-soluble starch into deionized water, stirring at 45 deg.C until completely dissolved to obtain starch solution, pulverizing montmorillonite, adding into the starch solution, stirring, and keeping stirring;
the mass fraction of starch in the solution A is 7%, the mass fraction of montmorillonite is 12%, and the particle size of montmorillonite is 0.2-0.25mm;
b. preparing a solution B: adding deionized water into ethanol to obtain an ethanol solution, then adding hydroxypropyl methyl cellulose into the ethanol solution, and stirring until the hydroxypropyl methyl cellulose is completely dissolved;
the methyl content of the hydroxypropyl methylcellulose is 28.1 percent, and the hydroxypropyl content is 8.4 percent; the mass fraction of the ethanol solution is 50 percent;
4-2) adding the nano iron particles into the solution A, reacting for 25min under the condition of keeping stirring, standing for 5min, filtering, drying filter residues in vacuum, and purging with nitrogen to obtain intermediate particles;
4-3) adding the intermediate particles into the solution B, stirring for 5min, standing for 3min, filtering, vacuum-drying filter residues, and purging with nitrogen to obtain the composite nano-iron particles.
Example 2
A green synthesis method of composite nano-iron particles comprises the following steps:
1) Dissolving lutein in ethyl acetate, and stirring to completely dissolve to obtain lutein solution;
wherein the concentration of lutein in the lutein solution is 1.5g/L.
2) Dripping the lutein solution into the soluble divalent or trivalent ferric salt solution while stirring, controlling the temperature to be 48 ℃, reacting for 12min to obtain a nano-iron suspension, and introducing nitrogen into the solution all the time in the reaction process;
wherein the soluble ferrous salt solution is 0.15mol/L ferrous chloride solution.
3) And (3) carrying out suction filtration on the nano-iron suspension, sequentially cleaning the obtained particles by using deionized water and absolute ethyl alcohol, carrying out vacuum drying at 45 ℃ for 16 hours, and grinding to obtain the nano-iron particles.
4) Preparing a coating solution, and then adding the nano-iron particles into the coating solution for coating to obtain the composite nano-iron particles, wherein the preparation method comprises the following specific steps:
4-1) preparing a coating solution:
a. preparing a solution A: adding water-soluble starch into deionized water, stirring at 50 deg.C until completely dissolved to obtain starch solution, pulverizing montmorillonite, adding into the starch solution, stirring, and keeping stirring;
the mass fraction of starch in the solution A is 10%, the mass fraction of montmorillonite is 11%, and the particle size of montmorillonite is 0.2-0.25mm;
b. preparing a solution B: adding deionized water into ethanol to obtain an ethanol solution, then adding hydroxypropyl methyl cellulose into the ethanol solution, and stirring until the hydroxypropyl methyl cellulose is completely dissolved;
the methyl content of the hydroxypropyl methylcellulose is 28.1 percent, and the hydroxypropyl content is 8.4 percent; the mass fraction of the ethanol solution is 50 percent;
4-2) adding the nano iron particles into the solution A, reacting for 30min under the condition of keeping stirring, standing for 5min, filtering, drying filter residues in vacuum, and purging with nitrogen to obtain intermediate particles;
4-3) adding the intermediate particles into the solution B, stirring for 7min, standing for 3min, filtering, vacuum-drying the filter residue, and purging with nitrogen gas to obtain the composite nano-iron particles.
Example 3
A green synthesis method of composite nano-iron particles comprises the following steps:
1) Dissolving lutein in ethyl acetate, stirring to dissolve completely to obtain lutein solution;
wherein the concentration of lutein in the lutein solution is 3g/L.
2) Dripping the lutein solution into the soluble divalent or trivalent ferric salt solution while stirring, controlling the temperature to be 42 ℃, reacting for 17min to obtain a nano-iron suspension, and introducing nitrogen into the solution all the time in the reaction process;
wherein the soluble ferrous salt solution is 0.25mol/L ferrous chloride solution.
3) And (3) carrying out suction filtration on the nano-iron suspension, sequentially cleaning the obtained particles by using deionized water and absolute ethyl alcohol, carrying out vacuum drying at 50 ℃ for 13 hours, and grinding to obtain the nano-iron particles.
4) Preparing a coating solution, and then adding the nano-iron particles into the coating solution for coating to obtain the composite nano-iron particles, wherein the preparation method comprises the following specific steps:
4-1) preparing a coating solution:
a. preparing a solution A: adding water-soluble starch into deionized water, stirring at 55 deg.C until completely dissolved to obtain starch solution, pulverizing montmorillonite, adding into the starch solution, stirring, and keeping stirring;
the mass fraction of starch in the solution A is 12%, the mass fraction of montmorillonite is 15%, and the particle size of montmorillonite is 0.2-0.25mm;
b. preparing a solution B: adding deionized water into ethanol to obtain an ethanol solution, then adding hydroxypropyl methylcellulose into the ethanol solution, and stirring until the hydroxypropyl methylcellulose is completely dissolved;
the methyl content of the hydroxypropyl methylcellulose is 28.1 percent, and the hydroxypropyl content is 8.4 percent; the mass fraction of the ethanol solution is 50 percent;
4-2) adding the nano iron particles into the solution A, reacting for 35min under the condition of keeping stirring, standing for 7min, filtering, drying filter residues in vacuum, and purging with nitrogen to obtain intermediate particles;
4-3) adding the intermediate particles into the solution B, stirring for 10min, standing for 5min, filtering, vacuum-drying filter residues, and purging with nitrogen to obtain the composite nano-iron particles.
Example 4
A green synthesis method of composite nano-iron particles comprises the following steps:
1) Dissolving lutein in ethyl acetate, and stirring to completely dissolve to obtain lutein solution;
wherein the concentration of lutein in the lutein solution is 2.5g/L.
2) Dripping the lutein solution into the soluble divalent or trivalent ferric salt solution while stirring, controlling the temperature at 45 ℃, reacting for 17min to obtain a nano-iron suspension, and introducing nitrogen into the solution all the time in the reaction process;
wherein the soluble ferrous salt solution or ferric salt solution is 0.22mol/L ferrous chloride solution.
3) And (3) carrying out suction filtration on the nano-iron suspension, sequentially cleaning the obtained particles by using deionized water and absolute ethyl alcohol, carrying out vacuum drying at 50 ℃ for 14 hours, and grinding to obtain the nano-iron particles.
4) Preparing a coating solution, and then adding the nano-iron particles into the coating solution for coating to obtain the composite nano-iron particles, wherein the preparation method comprises the following specific steps:
4-1) preparing a coating solution:
a. preparing a solution A: adding water-soluble starch into deionized water, stirring at 55 deg.C until completely dissolved to obtain starch solution, pulverizing montmorillonite, adding into the starch solution, stirring, and keeping stirring;
the mass fraction of starch in the solution A is 8%, the mass fraction of montmorillonite is 17%, and the particle size of montmorillonite is 0.2-0.25mm;
b. preparing a solution B: adding deionized water into ethanol to obtain an ethanol solution, then adding hydroxypropyl methyl cellulose into the ethanol solution, and stirring until the hydroxypropyl methyl cellulose is completely dissolved;
the methyl content of the hydroxypropyl methylcellulose is 28.1 percent, and the hydroxypropyl content is 8.4 percent; the mass fraction of the ethanol solution is 50 percent;
4-2) adding the nano iron particles into the solution A, reacting for 40min under the condition of keeping stirring, standing for 7min, filtering, drying filter residues in vacuum, and purging with nitrogen to obtain intermediate particles;
4-3) adding the intermediate particles into the solution B, stirring for 12min, standing for 5min, filtering, vacuum-drying the filter residue, and purging with nitrogen gas to obtain the composite nano-iron particles.
The present invention will be further explained by examining the sewage containing hexavalent chromium using the composite nano-iron particles prepared in examples 1 to 4 as a water purifying agent, and by combining the examination results of the water purifying agent in the comparative example below.
Comparative example 1
The nano-iron particles prepared in steps 1) -3) of example 1 were used directly as water purifying agents.
Comparative example 2
In this comparative example, only the difference from example 1 is step 4), and step 4) in this comparative example is specifically as follows:
4-1) preparing a coating solution:
preparing a solution B: adding deionized water into ethanol to obtain an ethanol solution, then adding hydroxypropyl methylcellulose into the ethanol solution, and stirring until the hydroxypropyl methylcellulose is completely dissolved;
the methyl content of the hydroxypropyl methylcellulose is 28.1 percent, and the hydroxypropyl content is 8.4 percent; the mass fraction of the ethanol solution is 50 percent;
4-2) adding the nano iron particles prepared in the step 3) into the solution B, stirring for 5min, standing for 3min, filtering, taking filter residues, drying in vacuum, and purging with nitrogen to obtain the composite nano iron particles.
Namely, in the comparative example, the nano iron particles prepared in the step 3) are coated with the hydroxypropyl methyl cellulose protective film.
Example 4 Water purifying agent vs. Cr 6+ Removal performance test of
The detection method comprises the following steps:
preparing 10mg/L test solution with pH of 5 to simulate sewage, adding 1L of the test solution to 1 portion of the water purifying agent of examples 1-4 and 1-2, shaking at room temperature for 15min, filtering, and measuring Cr in the filtrate by using diphenyl carbonyl dihydrazide method 6+ The concentration of (c); then calculating the water purifying agent pair Cr according to the following formula 6+ The adsorption efficiency of (2) was measured three times for each sample, and the average value was taken, and the results are shown in table 1.
The adsorption efficiency calculation formula is as follows:
SE=(C 0 -C e )/C 0 *100%;
wherein, C 0 And C e Respectively represents Cr 6+ Initial and equilibrium concentrations.
TABLE 1
Example 1 | Example 2 | Example 3 | Example 4 | Comparative example 1 | Comparative example 2 | |
Efficiency of adsorption/%) | 97.6 | 98.1 | 96.8 | 98.3 | 61.2 | 73.4 |
As can be seen from Table 1, the composite nano-iron particles obtained in examples 1 to 4 are all Cr-free 6+ Shows high-efficiency adsorption and can be used for Cr 6+ And (4) removing. The adsorption efficiency of the water purifying agent of the comparative example 1 is greatly reduced, and mainly after the nano iron particles are directly added into the test solution, agglomeration occurs, so that the utilization efficiency of the nano iron particles is greatly reduced, and the nano iron particles cannot be sufficiently combined with Cr 6+ The contact reaction causes the removal efficiency to be low, and on the other hand, the nano iron particles are partially oxidized because of no outer layer protection, so that the reducibility is reduced. The adsorption efficiency of comparative example 2 is higher than that of comparative example 1, but is also significantly lower than that of examples 1 to 4, mainly for two reasons: 1. the hydroxypropyl methyl cellulose protective film can prevent the nano iron particles from being oxidized; 2. the strong adsorption property of montmorillonite can improve Cr of water purifying agent 6+ The nano-iron particles can be effectively prevented from agglomerating by loading the montmorillonite, and the water-absorbing expansibility of the montmorillonite can ensure that the nano-iron particles are more fully mixed with Cr in water 6+ Contact reaction, thereby improving the purification effect.
While embodiments of the invention have been disclosed above, it is not limited to the applications listed in the description and the embodiments, which are fully applicable in all kinds of fields of application of the invention, and further modifications may readily be effected by those skilled in the art, so that the invention is not limited to the specific details without departing from the general concept defined by the claims and the scope of equivalents.
Claims (6)
1. A method for green synthesis of composite nano-iron particles is characterized by comprising the following steps:
1) Dissolving lutein in ethyl acetate, and stirring to completely dissolve to obtain lutein solution;
2) Dripping the lutein solution into a soluble divalent or trivalent ferric salt solution while stirring, controlling the temperature to be 30-65 ℃, reacting for 5-60min to obtain a nano-iron suspension, and introducing nitrogen into the solution all the time in the reaction process;
3) Carrying out suction filtration on the nano-iron suspension, sequentially cleaning the obtained particles by using deionized water and absolute ethyl alcohol, carrying out vacuum drying for 8-24 hours at 35-60 ℃, and grinding to obtain nano-iron particles;
4) Preparing a coating solution, and then adding the nano-iron particles into the coating solution for coating to obtain composite nano-iron particles;
the raw materials of the coating liquid in the step 4) comprise montmorillonite, water-soluble starch, deionized water, hydroxypropyl methyl cellulose and ethanol;
the preparation method of the coating solution in the step 4) comprises the following steps:
a. preparing a solution A: adding water-soluble starch into deionized water, stirring at 35-65 deg.C until completely dissolved to obtain starch solution, pulverizing montmorillonite, adding into the starch solution, stirring, and keeping stirring;
b. preparing a solution B: adding deionized water into ethanol to obtain an ethanol solution, then adding hydroxypropyl methyl cellulose into the ethanol solution, and stirring until the hydroxypropyl methyl cellulose is completely dissolved;
the coating method of the nano iron particles specifically comprises the following steps:
4-1) adding the nano iron particles into the solution A, reacting for 5-45min under the condition of keeping stirring, standing for 3-10min, filtering, drying filter residues in vacuum, and purging with nitrogen to obtain intermediate particles;
4-2) adding the intermediate particles into the solution B, stirring for 3-20min, standing for 2-10min, filtering, vacuum-drying filter residues, and purging with nitrogen gas to obtain composite nano iron particles;
the concentration of solute in the soluble bivalent or trivalent ferric salt solution is 0.05-0.3mol/L;
the concentration of the lutein in the lutein solution is 0.25-5g/L.
2. The method for green synthesis of composite nano-iron particles according to claim 1, wherein the soluble ferrous or ferric salt solution is any one or combination of ferrous chloride, ferrous sulfate, ferric chloride and ferric sulfate solution.
3. The green synthesis method of composite nano-iron particles according to claim 1, wherein the mass fraction of starch in solution A is 5% -20%, and the mass fraction of montmorillonite is 5% -25%.
4. The method for green synthesis of composite nano-iron particles according to claim 1, wherein the methyl content of hydroxypropyl methylcellulose is 25-30% and the hydroxypropyl content is 6-12%.
5. The green synthesis method of composite nano-iron particles according to claim 1, wherein the mass fraction of ethanol solution is 40-65%.
6. Use of the composite nano-iron particles according to any one of claims 1 to 5 as a water purifying agent or as a material for the preparation of a water purifying agent.
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