CN114054001A - Magnetic nano adsorbent and preparation method and application thereof - Google Patents

Abstract

The invention discloses a magnetic nano adsorbent and a preparation method and application thereof, wherein the magnetic nano adsorbent is Fe₃O₄@SiO₂@ Cs can be used for efficiently removing heavy metals and bacteria in water simultaneously, is simple to operate, high in removal efficiency, large in adsorption capacity, stable in structure, convenient to separate, wide in application, free of secondary pollution and capable of being processed intoThe method has low cost and good application prospect in the aspect of removing pollutants in water.

Description

Magnetic nano adsorbent and preparation method and application thereof

Technical Field

The invention belongs to the technical field of nanometer, and particularly relates to an application of a magnetic nanometer adsorbent in removing heavy metals and bacteria in water simultaneously.

Background

The development of industrialization leads to the increasing variety and quantity of pollutants in environmental water, and water pollutants can be divided into three categories, namely physical pollutants, chemical pollutants and biological pollutants according to the variety of harmful substances released by pollution sources. The physical contaminants mainly include suspended contaminants, radioactive contaminants and thermal contaminants, the suspended contaminants include insoluble substances contained in water, such as solid substances, foamed plastics and the like, the radioactive contaminants include radioactive substances, such as radioactive wastewater, radioactive waste and the like, and the thermal contaminants include cooling water of various industrial processes; the chemical pollutants mainly comprise inorganic chemical pollutants and organic chemical pollutants, the inorganic chemical pollutants comprise heavy metals and compounds thereof, such As mercury (Hg), cadmium (Cd), chromium (Cr), lead (Pb), arsenic (As), vanadium (V), cobalt (Co), copper (Cu), nickel (Ni), manganese (Mn) and other heavy metals, and the organic chemical pollutants comprise phenols and cresols, aromatic hydrocarbons and derivatives thereof, cyanogen and nitriles, organic oxides, organic chlorides, pesticides and the like; biological contaminants include bacteria, viruses, parasites, and the like. Among them, heavy metal pollution and bacterial pollution are considered to be the most common pollutants at present, and because heavy metals have the characteristics of high toxicity, strong accumulation, easy biological enrichment, biological amplification, no degradability and carcinogenicity, the heavy metals not only pollute the ecosystem, but also seriously threaten the survival and health of human beings.

Materials currently reported for removing heavy metals from water include metal organic framework materials, magnetic composite adsorption materials, mesoporous molecular sieves, cellulose-based adsorption materials, carbon-based materials, hydrogel materials, magnetic mesoporous materials, such as: CN201911007464.4 discloses a zinc-based metal organic framework material, and the zinc-based metal organic framework material is applied to the treatment of heavy metal wastewater; CN201610891600.0 discloses a magnetic composite adsorption material (MnO)₂-Fe₃O₄) And the method is applied to removing heavy metals in water; CN202011605511.8 discloses a functionalized mesoporous molecular sieve MCM-41, and the mesoporous molecular sieve MCM-41 is applied to the adsorption of heavy metal ions Pb (II) in water; CN201010570303.9 discloses a cellulose matrix adsorbing material with carboxyl functionalization, and the cellulose matrix adsorbing material is applied to removing heavy metal cations in water; CN201811463751.1 discloses a carbon-based material, which is prepared by taking hydrothermal carbon as a raw material and combining with the processes of microbial liquid fermentation and steam explosion to improve the hydrothermal carbon, and is applied to the purification of heavy metal wastewater; CN201910771713.0 discloses a hydrogel material, which is prepared by respectively adding cross-linking agents into gamma-polyglutamic acid and polyaspartic acid, dissolving the cross-linking agents in a buffer solution containing a photoinitiator, forming gel under the irradiation of an ultraviolet lamp, and applying the gel to absorb heavy metal ions in wastewater; CN201710611743.6 discloses a floatable magnetic hollow material, which is prepared by combining agricultural wastes such as banana and the like, dried leaves of Musaceae, dried leaves of corn, rice husks and the like with alginate, nano ferroferric oxide and nano ferrous chloride, and is applied to the removal of heavy metals in water.

Materials currently reported for removing bacteria from water include superparamagnetic nickel nanoparticles, acrylonitrile copolymers, nanocomposite filters, carbon fibers, such as: CN202010351718.0 discloses a superparamagnetic nickel nano-tubeRice particles, the superparamagnetic nickel nano particles are prepared by adding NiCl into DEG in the presence of NaOH and NaCit₂Carrying out thermal hydrolysis and reduction reaction; the prepared NaOH/DEG mixture is rapidly injected into NiCl₂Obtained in the/NaCit/DEG phase and applied to adsorb bacteria and bacterial spores in water; CN201780056155.9 discloses a membrane of acrylonitrile copolymer prepared from sodium methallylsulfonate and acrylonitrile, and its application for removing bacteria in water; CN201410644645.9 discloses a nano composite filter material, which is obtained by mixing and grinding seaweed mud, E33 and zeolite powder, adding water, then firing at high temperature, mixing the product obtained by firing with nano titanium dioxide, and applying the product to remove bacteria in water; CN201810102072.5 discloses a carbon fiber adsorption medium, which is activated carbon particles, chopped activated carbon fiber aggregate or activated carbon fiber felt with a certain thickness, and is applied to water purification.

Although the prior art can be respectively used for removing heavy metals and bacteria in water to a certain extent, the prior art still has some technical defects, such as incapability of being simultaneously used for removing heavy metals and bacteria in water, complex operation, low removal efficiency, expensive raw materials, high cost, complex procedure for preparing the adsorption material, poor stability, easy generation of secondary pollution and the like.

Disclosure of Invention

In view of the above, in order to overcome the above disadvantages and shortcomings of the prior art, the present invention provides an application of a magnetic nano-adsorbent, Fe, in removing heavy metals and bacteria in water simultaneously₃O₄@SiO₂@ Cs can be used for simultaneously and efficiently removing heavy metals and bacteria in water, is simple to operate, high in removal efficiency, large in adsorption capacity, stable in structure, convenient to separate, wide in application, free of secondary pollution and low in treatment cost, and has a good application prospect in the aspect of removing pollutants in water.

The above object of the present invention is achieved by the following technical solutions:

the invention provides a preparation method of a magnetic nano-adsorption material for simultaneously removing heavy metals and bacteria in water.

Further, the method comprises the steps of:

(1) preparation of Fe₃O₄A magnetic fluid;

(2) to the Fe obtained in step (1)₃O₄Adding a solvent into the magnetofluid to obtain a dispersion liquid;

(3) adding ammonia water and ethyl orthosilicate into the dispersion liquid obtained in the step (2), and reacting to obtain a magnetic material Fe₃O₄@SiO₂；

(4) Fe obtained in the step (3)₃O₄@SiO₂Mixing with chitosan solution, adding glutaraldehyde solution, and reacting to obtain magnetic nano-adsorption material Fe₃O₄@SiO₂@Cs。

Further, the Fe in the step (1)₃O₄The preparation of the magnetic fluid comprises the step of adding FeCl₃·6H₂O and FeSO₄·7H₂Adding O into solvent for dissolving, adding concentrated hydrochloric acid for ultrasonic treatment, and adjusting pH of the solution after ultrasonic treatment>10 hours, reacting, standing to obtain Fe₃O₄A magnetic fluid;

preferably, the FeCl₃·6H₂O and FeSO₄·7H₂The molar ratio of O is 4: 3;

preferably, the solvent is pure water;

preferably, the addition amount of the concentrated hydrochloric acid is 800-;

more preferably, the addition amount of the concentrated hydrochloric acid is 850 μ L;

preferably, the time of the ultrasonic treatment is 20-40 min;

more preferably, the time of the ultrasonic treatment is 30 min;

preferably, the pH adjustment is performed by adding ammonia;

preferably, the reaction is carried out under heating and stirring conditions;

more preferably, the temperature of the heating is 65-95 ℃;

most preferably, the temperature of the heating is 80 ℃;

more preferably, the stirring speed is 750-1250 r/min;

most preferably, the speed of stirring is 1000 r/min;

more preferably, the stirring time is 30-60 min;

most preferably, the stirring time is 40 min.

Further, FeCl is added₃·6H₂O and FeSO₄·7H₂Adding O into pure water, fully stirring and properly heating to completely dissolve the O, and then carrying out suction filtration;

further, the reaction is carried out under the condition of water bath.

Further, standing for 30-90min after the reaction is finished, and separating the obtained precipitate from the reaction medium by using magnetic separation to obtain Fe₃O₄A magnetic fluid;

preferably, the standing time is 60 min.

Further, the solvent in the step (2) comprises absolute ethyl alcohol and pure water;

preferably, the dosage of the anhydrous ethanol is 250-750 mL;

more preferably, the dosage of the absolute ethyl alcohol is 500 mL;

preferably, the amount of the pure water is 100-400 mL;

more preferably, the amount of the pure water is 250 mL.

Further, adding Fe obtained in the step (1)₃O₄Adding solvent absolute ethyl alcohol and pure water into the magnetic fluid, and then carrying out ultrasonic treatment;

preferably, the time of the ultrasonic treatment is 5-15 min;

more preferably, the time of the ultrasonic treatment is 10 min.

Further, the dosage of the ammonia water in the step (3) is 20-50mL, and the dosage of the tetraethoxysilane is 25-75 mL;

preferably, the dosage of the ammonia water is 38mL, and the dosage of the tetraethoxysilane is 50 mL;

preferably, the reaction in step (3) comprises a first stage reaction and a second stage reaction;

more preferably, the first stage reaction and the second stage reaction are carried out under heating and stirring conditions;

most preferably, the heating temperature of the first stage reaction is 40-80 ℃;

most preferably, the heating temperature of the first stage reaction is 60 ℃;

most preferably, the stirring speed of the first-stage reaction is 750-1250 r/min;

most preferably, the stirring speed of the first stage reaction is 1000 r/min;

most preferably, the stirring time of the first stage reaction is 1-2 h;

most preferably, the stirring time of the first stage reaction is 1.5 h;

most preferably, the heating temperature of the second stage reaction is 40-80 ℃;

most preferably, the heating temperature of the second stage reaction is 60 ℃;

most preferably, the stirring speed of the second-stage reaction is 250-750 r/min;

most preferably, the stirring speed of the second stage reaction is 500 r/min;

most preferably, the stirring time of the second stage reaction is 1-5 h;

most preferably, the stirring time for the second stage reaction is 3 h.

Further, the reaction is carried out under the condition of water bath.

Further, after the reaction is finished, the obtained material is subjected to magnetic separation, the supernatant is discarded, the material is fully washed and then is subjected to vacuum drying, and the magnetic material Fe is obtained after the drying₃O₄@SiO₂。

Further, Fe in step (4)₃O₄@SiO₂The dosage of the chitosan solution is 0.05-0.35g, the dosage of the chitosan solution is 40-80mL, and the pentanedium salt isThe dosage of the aldehyde solution is 1-5 mL;

preferably, the Fe₃O₄@SiO₂The dosage of the chitosan solution is 0.2g, the dosage of the chitosan solution is 60mL, and the dosage of the glutaraldehyde solution is 3 mL;

more preferably, the chitosan solution is a 1% chitosan solution and the glutaraldehyde solution is a 5% glutaraldehyde solution;

most preferably, the 5% glutaraldehyde solution is added dropwise;

preferably, the reaction in step (4) is carried out under heating and stirring conditions;

more preferably, the temperature of the heating is 40-80 ℃;

most preferably, the temperature of the heating is 60 ℃;

more preferably, the stirring speed is 250-750 r/min;

most preferably, the stirring speed is 500 r/min;

more preferably, the stirring time is 20-40 min;

most preferably, the stirring time is 30 min.

Further, the 1% chitosan solution is prepared by using 3% acetic acid as a solvent;

further, the reaction is carried out under the condition of water bath, and after the reaction is finished, precipitates obtained by the reaction are separated out through magnetic separation;

preferably, the precipitate obtained by separation is fully washed by 3 percent acetic acid and dried in vacuum to obtain the magnetic nano adsorbing material Fe₃O₄@SiO₂@Cs。

A second aspect of the present invention provides a magnetic nano-adsorbent material for simultaneously removing heavy metals and bacteria from water.

Further, the magnetic nano-adsorption material is prepared by the method of the first aspect of the invention;

preferably, the magnetic nano-adsorption material is structurally characterized in that: fe₃O₄Being a magnetic core, SiO₂Is an intermediate layer, and is characterized in that,the chitosan is the outermost layer.

The third aspect of the invention provides the application of the magnetic nano-adsorption material of the second aspect of the invention in removing heavy metals and bacteria in water simultaneously;

preferably, the heavy metals include Cr, As, Hg, Se, Pb, Cd, V, Co, Cu, Ni, Mn, Ag, Zn, Ba, Be;

more preferably, the heavy metal is Cr, As, Hg, Se, Pb, Cd;

preferably, the bacteria include gram positive and gram negative bacteria;

more preferably, the gram-positive bacterium is staphylococcus aureus;

more preferably, the gram-negative bacterium is escherichia coli.

The fourth aspect of the invention provides the application of the magnetic nano-adsorption material of the second aspect of the invention in removing heavy metals in water;

preferably, the heavy metals include Cr, As, Hg, Se, Pb, Cd, V, Co, Cu, Ni, Mn, Ag, Zn, Ba, Be;

more preferably, the heavy metal is Cr, As, Hg, Se, Pb, Cd.

A fifth aspect of the invention provides the use of a magnetic nano-adsorbent material according to the second aspect of the invention for the removal of bacteria from water;

preferably, the bacteria include gram positive and gram negative bacteria;

more preferably, the gram-positive bacterium is staphylococcus aureus;

more preferably, the gram-negative bacterium is escherichia coli.

According to a sixth aspect of the invention, there is provided the use of the magnetic nano-adsorbent material according to the second aspect of the invention as a wastewater treatment agent in water treatment.

The invention adopts a coprecipitation method to synthesize Fe₃O₄@SiO₂@ Cs, core Fe₃O₄Has strong magnetism and SiO in the middle layer₂Play a role in improving Fe₃O₄Oxidation resistance ofThe stability of the chitosan is enhanced, and the chitosan on the outermost layer provides amino and mainly plays a role in adsorbing and removing heavy metals and bacteria in water.

The invention synthesizes the obtained magnetic nano-adsorption material Fe₃O₄@SiO₂The @ Cs is characterized, the removal conditions of the heavy metal and bacteria applied to the water are optimized, in addition, the preferential adsorption sequence of the heavy metal ions in the water is tested, and the prior adsorption sequence is applied to the removal of the heavy metal and the bacteria in the actual water sample.

Compared with the prior art, the invention has the following advantages and beneficial effects:

in the invention, Fe₃O₄Being a magnetic core, SiO₂Is the middle layer and the chitosan is the outermost layer, and synthesizes Fe₃O₄@SiO₂The @ Cs magnetic nano adsorbent is prepared from common laboratory medicines as synthetic raw materials, is low in synthesis cost and simple in synthesis process, and the synthesized magnetic nano adsorbent is stable in structure and Fe₃O₄@SiO₂@ Cs has high adsorption rate on heavy metals and bacteria in water, high adsorption efficiency, large adsorption capacity and good removal effect, and the synthesized Fe is₃O₄@SiO₂The @ Cs has good adsorption effect on various heavy metal ions and various bacteria (including gram-positive bacteria and gram-negative bacteria) in water, the application range is wide, the adsorbed magnetic nano-adsorbent can be rapidly separated through an external magnetic field, and the operation is simple and convenient.

Drawings

Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a flow chart of an embodiment of the present invention;

FIG. 2 is the synthesis of Fe₃O₄@SiO₂Experimental flow charts for @ Cs;

FIG. 3 is for Fe₃O₄、Fe₃O₄@SiO₂、Fe₃O₄@SiO₂@ Cs, by X-ray diffraction analysis (XRD);

FIG. 4 is for Fe₃O₄@SiO₂And Fe₃O₄@SiO₂Results obtained by SEM characterization analysis of @ Cs, wherein A is: fe₃O₄@SiO₂And B, drawing: fe₃O₄@SiO₂@Cs；

FIG. 5 is for Fe₃O₄@SiO₂@ Cs is subjected to SEM-mapping characterization analysis to obtain a result graph;

FIG. 6 is for Fe₃O₄@SiO₂@ Cs in Fourier transform Infrared Spectroscopy (FTIR);

FIG. 7 is for Fe₃O₄@SiO₂@ Cs BET Aperture analysis₂Adsorption and desorption isotherm diagrams;

FIG. 8 is for Fe₃O₄@SiO₂、Fe₃O₄@SiO₂Results obtained by Zeta potential analysis of @ Cs;

FIG. 9 is for Fe₃O₄、Fe₃O₄@SiO₂、Fe₃O₄@SiO₂@ Cs is subjected to vibration sample magnetometer analysis to obtain a result graph;

FIG. 10 is for Fe₃O₄@SiO₂The pH optimization result graph when @ Cs adsorbs Cr (VI);

FIG. 11 is for Fe₃O₄@SiO₂Results of optimization of adsorption time when @ Cs adsorbs Cr (VI);

FIG. 12 is for Fe₃O₄@SiO₂A result graph of optimizing the dosage of the adsorbent when @ Cs adsorbs Cr (VI);

FIG. 13 is Fe₃O₄@SiO₂Results plot of the adsorption efficiency of @ Cs to heavy metal ions;

FIG. 14 is Fe₃O₄@SiO₂Results plot of the adsorption capacity of @ Cs to heavy metal ions;

FIG. 15 shows the measurement of Fe₃O₄@SiO₂A result graph of the priority order of @ Cs to heavy metal adsorption in water;

FIG. 16 is for Fe₃O₄@SiO₂@ Cs adsorption of Escherichia coli pH, an optimized result graph;

FIG. 17 is for Fe₃O₄@SiO₂Results of optimization of adsorption time when @ Cs adsorbs Escherichia coli;

FIG. 18 shows the volume of bacterial suspension and the adsorbent Fe₃O₄@SiO₂Results of the effect of the adsorption frequency of @ Cs on the efficiency of adsorbing Escherichia coli;

FIG. 19 shows an adsorbent Fe₃O₄@SiO₂Results graph of the effect of the amount of @ Cs on the efficiency of adsorption of Escherichia coli;

FIG. 20 is for Fe₃O₄@SiO₂Results of optimization of adsorption frequency when @ Cs adsorbs Escherichia coli;

FIG. 21 validation of Fe with Staphylococcus aureus₃O₄@SiO₂Graph of the adsorption effect of @ Cs on bacteria, wherein, graph A: non-adsorbed, panel B: after one adsorption, panel C: after two times of adsorption;

FIG. 22 is Fe₃O₄@SiO₂Results of the removal effect of @ Cs on actual water samples.

Detailed Description

The present invention is further illustrated below with reference to specific examples, which are intended to be illustrative only and are not to be construed as limiting the invention. As will be understood by those of ordinary skill in the art: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents. The following examples are examples of experimental methods not indicating specific conditions, and the detection is usually carried out according to conventional conditions or according to the conditions recommended by the manufacturers.

Example 1 magnetic Nanosorbent Fe₃O₄@SiO₂Preparation of @ Cs

1、Fe₃O₄Preparation of

5.21g FeCl was weighed₃·6H₂O and 4.22g FeSO₄·7H₂O (molar ratio 4:3) is added into 250mL of pure water, fully stirred, properly heated to be completely dissolved and filtered. Adding 850 μ L concentrated hydrochloric acid, and removing by ultrasonicOxygen treatment for 30 min. Adding the solution after ultrasonic treatment into a three-neck round-bottom flask, adding ammonia water to adjust the pH value to be more than 10, and stirring for 40min under the conditions that the water bath temperature is 80 ℃ and the stirring speed is 1000 r/min. Standing for 60min after the reaction is finished to obtain black precipitate. Separating the precipitate from the reaction medium by magnetic separation to obtain Fe magnetic fluid₃O₄。

2、Fe₃O₄@SiO₂Preparation of

Adding 500mL of absolute ethyl alcohol and 250mL of pure water into the magnetic fluid, adding the mixture into a three-neck round-bottom flask after completely dispersing, and performing ultrasonic treatment for 10 min. After the completion of sonication, 38mL of ammonia water and 50mL of ethyl orthosilicate were added to the dispersion. Stirring for 1.5h under the reaction condition that the water bath temperature is 60 ℃ and the stirring speed is 1000r/min, then stirring for 3h under the condition that the stirring speed is 500r/min, and stopping the reaction. And (3) magnetically separating the obtained material, pouring out the supernatant, fully washing, putting into a vacuum drier, and fully drying.

3、Fe₃O₄@SiO₂Preparation of @ Cs

0.2g of Fe₃O₄@SiO₂The magnetic material was mixed with 60mL of a 1% strength chitosan solution (3% acetic acid as solvent) and 3mL of a 5% strength glutaraldehyde solution was added dropwise. Stirring is continuously carried out for 30min under the reaction condition that the water bath temperature is 60 ℃ and the stirring speed is 500 r/min. After the reaction is finished, separating out the precipitate by magnetic separation, fully washing the precipitate by using 3 percent acetic acid, and drying the precipitate in vacuum to obtain Fe₃O₄@SiO₂@Cs。

4. Results of the experiment

FIG. 1 shows a flow chart of an embodiment of the present invention, and FIG. 2 shows Fe production in this example₃O₄@SiO₂Experimental flow chart of @ Cs, Fe prepared finally₃O₄@SiO₂@ Cs is in the form of black particles.

Example 2 magnetic Nanoadsorbent Fe₃O₄@SiO₂Characterization of @ Cs

1. Experimental methods

This example is a comparison of Fe synthesized in example 1₃O₄@SiO₂@ Cs was characterized by (X-ray diffraction) XRD, (scanning electron microscope) SEM, (scanning electron microscope-element distribution) SEM-mapping, (Fourier transform infrared absorption) FTIR, (specific surface area test) BET, (Zeta potential) Zeta, (vibrating sample magnetometer) VSM, respectively.

Respectively to Fe₃O₄、Fe₃O₄@SiO₂、Fe₃O₄@SiO₂@ Cs was characterized by XRD to analyze the composition, internal structure or morphology of the synthesized material; for the finally obtained Fe₃O₄@SiO₂@ Cs was subjected to SEM and SEM-mapping characterization to analyze Fe₃O₄@SiO₂The surface structure and composition of @ Cs, and the distribution characteristics of elements in space; for 1% chitosan solution and Fe₃O₄@SiO₂The @ Cs is subjected to FTIR characterization so as to analyze the characteristics of the material such as spectral peak position, wave number, peak shape and the like; for the finally obtained Fe₃O₄@SiO₂@ Cs was subjected to BET characterization to analyze Fe₃O₄@SiO₂Specific surface area, pore size distribution, pore volume, etc. of @ Cs; for Fe₃O₄@SiO₂And Fe₃O₄@SiO₂@ Cs Zeta potential characterization was performed to analyze Fe₃O₄@SiO₂And Fe₃O₄@SiO₂The case where the Cs surface is charged; for Fe₃O₄、Fe₃O₄@SiO₂、Fe₃O₄@SiO₂@ Cs was subjected to VSM characterization to analyze Fe₃O₄、Fe₃O₄@SiO₂、Fe₃O₄@SiO₂Magnetic properties of @ Cs.

2. Results of the experiment

The experimental results show that in Fe₃O₄The diffraction peaks of (3451) (6480) (3170) (2780) (3602) (4168) (2394) (see fig. 3) correspond to 2 theta values of 30.3 degrees, 35.5 degrees, 43.1 degrees, 53.7 degrees, 57.2 degrees, 62.8 degrees and 72.9 degrees, and the characteristic peaks show that Fe is contained in the diffraction peaks₃O₄Having the typical characteristics of cubic phase and face-centered cubic structure, and alsoIs clear of Fe₃O₄Stable in three materials and good stability during modification thereof, Fe₃O₄@SiO₂And Fe₃O₄@SiO₂The 2 theta peak value of @ Cs is increased somewhat between 20 deg. -70 deg. (see FIG. 3), due to Fe₃O₄The surface is coated with amorphous SiO₂Caused by coating, Fe₃O₄@SiO₂The 2 theta peak value of @ Cs is greatly increased between 20 DEG and 30 DEG (see figure 3) due to the addition of chitosan, and the above results all indicate that SiO is₂And Cs has been successfully coated onto Fe₃O₄The above.

The results of SEM characterization showed that Fe₃O₄@SiO₂、Fe₃O₄@SiO₂@ Cs are irregular ovals. Fe₃O₄@SiO₂Particle size of 50 to 70nm, Fe₃O₄@SiO₂The @ Cs particle size is still small, between 150nm and 300 nm. The particles were intact and uniform with better morphology (see fig. 4A and B). Fe₃O₄@SiO₂The middle part has obvious deep and light layering, the deep color is a core, the light color is a shell, the middle part has a typical core-shell structure, and the substance with the darker color in the middle part is Fe₃O₄The outer layer is wrapped by SiO₂(see FIG. 4A), indicating Fe₃O₄With SiO₂Successful combination of (1) Fe can also be seen in FIG. 5₃O₄@SiO₂The results of the local element information of @ Cs show that the elements of iron, oxygen, silicon and nitrogen are uniformly distributed in Fe₃O₄@SiO₂@ Cs surface, indicating SiO₂And Cs are successfully coated to Fe₃O₄The above.

The results of FTIR characterization showed 1700cm in line a (1% chitosan solution)^-1is-NH contained in chitosan₂The vibration absorption peak of medium N-H; 3250cm^-1To 3400cm^-1is-NH in chitosan₂and-OH, which is also the main absorption band for the formation of associated hydrogen bonds; b line (Fe)₃O₄@SiO₂@ Cs) of 570cm^-1A vibration absorption peak at the Fe-O bond; 800cm^-1The absorption peak is the symmetric stretching vibration peak and the bending vibration peak of Si-O-Si; 1100cm^-1A strong and wide absorption peak is positioned and is a Si-O-Si bond antisymmetric stretching vibration absorption peak; 1700cm^-1Is of the formula-NH₂The vibration absorption peak of medium N-H; 3250cm^-1At a peak-to-high frequency of 3405cm^-1The position shift reflects the interaction between Si-OH and chitosan, oxygen and nitrogen atoms and influences the hydroxylammonia overlapping stretching vibration of chitosan molecules; at 3400cm^-1Is represented by-NH₂and-OH (see FIG. 6), the above results indicate that chitosan has been successfully modified in Fe₃O₄@SiO₂Of (2) is provided.

The BET characterization results show that Fe₃O₄@SiO₂N of @ Cs₂The adsorption and desorption isotherms show typical type III isotherms with hysteresis loops of type H3, consistent with the characteristics of mesoporous structure (see FIG. 7), Fe was obtained based on BET adsorption experiments₃O₄Is 141.86m²In terms of/g, in favor of SiO₂Coating of (2), Fe₃O₄@SiO₂Is 21.82m²/g，Fe₃O₄@SiO₂@ Cs specific surface area 27.34m²Is due to-NH₂The coating increases the specific surface area and provides more adsorption sites for the adsorbent.

The results of Zeta characterisation show that Fe₃O₄@SiO₂The surface is negatively charged at-41.3 mv, which may be Fe₃O₄@SiO₂Due to addition of-OH to the surface, Fe₃O₄@SiO₂The @ Cs surface was positively charged at +28.89mv (see FIG. 8), indicating-NH₂Successfully modifies to Fe₃O₄@SiO₂And the surface of the adsorbent is positively charged, which is more beneficial to electrostatic adsorption.

The results of VSM characterization showed that the nanoparticles exhibited coercivity and remanence close to zero (see fig. 9), indicating that they have typical superparamagnetism; fe₃O₄、Fe₃O₄@SiO₂、Fe₃O₄@SiO₂@ Cs three-material saturated bodyAnd magnetization of 84.2, 76.4, 57.8emu/g, respectively (see FIG. 9), due to SiO₂And the addition of chitosan leads to the coercive force to be diluted, the saturation magnetization is reduced, but Fe₃O₄@SiO₂The saturation magnetization of @ Cs can still be rapidly separated by the magnet, and therefore, the adsorbent can be adsorbed and separated by means of an external magnetic field.

Comparative example 1 Fe₃O₄@SiO₂Optimization of pH when @ Cs adsorbs Cr (VI)

1. Experimental methods

When the pH was measured to be 1, 1.5, 2, 2.25, 2.5, 2.75, 3, 4, 5, 6, 7 under the experimental conditions of a Cr (vi) concentration of 20 μ g/L, an adsorption time of 15min, and an adsorbent amount of 50mg, Fe was added to the reaction mixture₃O₄@SiO₂@ Cs has an effect of adsorbing Cr (VI).

2. Results of the experiment

The experimental results showed that the adsorption efficiency increased with increasing pH as the pH was changed from 1 to 2.5, and in the pH 2.5 environment, the adsorption efficiency was as high as 79.5%, but decreased with increasing pH as the pH was changed from 2.5 to 7, and in the pH 7 environment, the adsorption efficiency was as low as 8.5% (see fig. 10), indicating that the adsorbent Fe was present in the pH 2.5 environment₃O₄@SiO₂The @ Cs has the best effect of adsorbing Cr (VI).

Comparative example 2 Fe₃O₄@SiO₂Optimization of adsorption time when @ Cs adsorbs Cr (VI)

1. Experimental methods

Under the experimental conditions that the pH value is 2.5, the concentration of Cr (VI) is 20 mug/L and the dosage of the adsorbent is 50mg, when the adsorption time is respectively 5min, 10min, 15min, 30min, 60min and 90min, Fe is measured₃O₄@SiO₂@ Cs has an effect of adsorbing Cr (VI).

2. Results of the experiment

The experimental result shows that the adsorption efficiency is rapidly increased along with the adsorption time when the adsorption time is 0min to 15min, the adsorption efficiency is slowly increased along with the adsorption time and finally tends to balance when the adsorption time is 15min to 90min (see figure 11), and the adsorption time is selected to be 15min in combination with the time cost and the adsorption efficiency.

Comparative example 3 Fe₃O₄@SiO₂Optimization of adsorbent dosage when @ Cs adsorbs Cr (VI)

1. Experimental methods

Fe was measured under the conditions of pH 2.5, Cr (VI) concentration of 20. mu.g/L and adsorption time of 15min at the adsorbent dosages of 0.025g, 0.05g, 0.075g, 0.1g and 0.15g, respectively₃O₄@SiO₂@ Cs has an effect of adsorbing Cr (VI).

2. Results of the experiment

The experimental results show that the dosage of the adsorbent is increased from 25mg to 100mg, the adsorption efficiency is increased from 62.5% to 90.5%, the dosage of the adsorbent is increased from 100mg to 150mg, the adsorption efficiency is increased from 90.5% to 94.5%, the adsorption efficiency is not obviously improved (see figure 12), and the optimal dosage of the adsorbent is finally determined to be 100mg by combining economic factors and adsorption efficiency.

Comparative example 4 determination of Fe₃O₄@SiO₂Adsorption capacity of @ Cs to other heavy metals

1. Experimental methods

Under the above-described optimum experimental conditions, Fe was measured separately₃O₄@SiO₂The adsorption efficiency of @ Cs to heavy metal ions As, Hg, Se, Pb and Cd, and Fe₃O₄@SiO₂The adsorption capacity of @ Cs to heavy metal ions Cr (VI), As, Hg, Se.

2. Results of the experiment

The experimental results show that Fe₃O₄@SiO₂The adsorption efficiencies of @ Cs for As of 73.54%, for Hg of 91.6% and for Se even more up to 100% (see FIG. 13), indicating that the adsorbent Fe₃O₄@SiO₂@ Cs can also be used for adsorbing other heavy metal ions in the drinking water; further, Fe₃O₄@SiO₂@ Cs also has high adsorption capacity for other heavy metal ions in drinking water, Fe₃O₄@SiO₂The adsorption capacity of @ Cs to Cr (VI) reaches 82.5mg/g,has high adsorption capacity to other heavy metals, wherein the adsorption capacity to Se is as high as 129.928mg/g (see figure 14), and the results show that Fe₃O₄@SiO₂The @ Cs has good effects on removal and enrichment of heavy metal ions in the drinking water.

Comparative example 5 determination of Fe₃O₄@SiO₂Priority order of @ Cs to adsorption of heavy metals in water

1. Experimental methods

To study Fe₃O₄@SiO₂The preferential selectivity of @ Cs to the adsorption of heavy metals in water selects various cations as competitive ions, and compares Fe at two different concentrations (high concentration and national standard concentration)₃O₄@SiO₂The adsorption efficiency of @ Cs for various metal cations.

2. Results of the experiment

The experimental results show that Fe is present at high concentrations, both at the national standard concentration and at the same time₃O₄@SiO₂The adsorption selectivity of @ Cs for each metal cation is: cr (VI) approximately equals to As>Hg>Se (see FIG. 15).

Comparative example 6 Fe₃O₄@SiO₂Optimization of pH when @ Cs adsorbs Escherichia coli

1. Experimental methods

The same amount of the same system was collected, the dilution gradient was the same, and when the pH was measured to be pH 3, pH 4, pH 5, pH 6, pH 7, pH 8, pH 9, Fe was measured₃O₄@SiO₂The adsorption efficiency of @ Cs to E.coli.

2. Results of the experiment

The experimental result shows that Fe is added under the condition of pH 3₃O₄@SiO₂The adsorption efficiency of @ Cs to Escherichia coli is extremely high, and the magnetic material Fe₃O₄@SiO₂The adsorption efficiency of @ Cs to Escherichia coli slightly fluctuates with the change of pH, but the adsorption efficiency can still reach over 86% (see figure 16), which indicates that the magnetic material Fe prepared by the method disclosed by the invention₃O₄@SiO₂@ Cs has better effect on water samples with pH between 3 and 9The water purification effect and the adsorption performance can not change along with the change of the environment, further showing that the Fe of the invention₃O₄@SiO₂The @ Cs has better stability and applicability.

Comparative example 7 Fe₃O₄@SiO₂Optimization of adsorption time when @ Cs adsorbs Escherichia coli

1. Experimental methods

Taking the same amount of bacterial liquid in the same system, diluting with the same gradient, and using magnetic material Fe₃O₄@SiO₂At @ Cs dosage of 1mg, and Fe at adsorption time of 5min, 10min, 15min, 30min, 60min, and 180min₃O₄@SiO₂The adsorption efficiency of @ Cs to E.coli.

2. Results of the experiment

The experimental result shows that the adsorption rate reaches 74.95% when the adsorption time is 5 min; the data show that the adsorption equilibrium can be achieved only when the adsorption time of a plurality of adsorbents reaches 2-24h in the using process, and the magnetic material Fe prepared by the method₃O₄@SiO₂1mg for @ Cs, the adsorption time is 3h, the adsorption rate can reach 97.40% (see figure 17), after adsorption is finished, the magnetic material can be quickly separated by using one magnet, and further effective separation and reuse of the adsorbent are realized₃O₄@SiO₂The application prospect of the @ Cs as the adsorbent is better.

Comparative example 8 Fe₃O₄@SiO₂Optimization of @ Cs for complete removal of E.coli

1. Experimental methods

The concentration of the Escherichia coli in the experimental sample is 4915cfu/mL, and when the amounts of Escherichia coli liquid to be measured are 20mL and 100mL respectively, the adsorbent Fe₃O₄@SiO₂In the case where the adsorption frequency of @ Cs is 1, 2, 3 or 4 times, Fe₃O₄@SiO₂The adsorption efficiency of @ Cs on Escherichia coli; when the amounts of the adsorbents used were measured to be 0.001g, 0.0025g, 0.005g, 0.0075g, and 0.01g, respectively, Fe₃O₄@SiO₂Adsorption of @ Cs to E.coliEfficiency; determination of the adsorbent Fe₃O₄@SiO₂In the case where the adsorption frequency of @ Cs is 1, 2, 3 or 4 times, Fe₃O₄@SiO₂The adsorption efficiency of @ Cs to E.coli.

2. Results of the experiment

The experimental result shows that the adsorption effect of 100mL of bacterial liquid is obviously lower than that of 20mL of bacterial liquid every time (see fig. 18), which indicates that the adsorption effect is reduced by increasing the volume of the bacterial liquid without changing the material dosage, so that a large-volume sample can be completely purified by properly increasing the adsorbent dosage and adsorbing for multiple times; firstly, the adsorption efficiency is improved by changing the dosage of the adsorbent, and as a result, the adsorption efficiency is gradually increased along with the increase of the dosage of the adsorbent as shown in figure 19; the subsequent research on the improvement of the adsorption efficiency by increasing the adsorption times shows that the result is shown in FIG. 20, Escherichia coli in sewage can be completely adsorbed by a repeated adsorption method for many times, and the adsorption time can reach 100% after 4 times, further showing that the magnetic material Fe prepared by the invention₃O₄@SiO₂The @ Cs has a good application prospect in the aspect of adsorbing gram-negative bacteria as an adsorbent.

Application example 1 Fe₃O₄@SiO₂Test of removal Effect of @ Cs on gram-Positive bacteria

1. Experimental methods

This application example uses Staphylococcus aureus to verify Fe₃O₄@SiO₂The adsorption Effect of @ Cs on bacteria and Fe respectively₃O₄@SiO₂The adsorption effect before, after and after the adsorption of @ Cs is recorded and analyzed.

2. Results of the experiment

The experimental results show that Fe₃O₄@SiO₂The adsorption of @ Cs twice can completely remove staphylococcus aureus (see fig. 21A-C), which indicates that whether gram-negative bacteria or gram-positive bacteria are subjected to the method of multiple adsorption, Fe₃O₄@SiO₂@ Cs completely removed. Further shows Fe₃O₄@SiO₂@ Cs may be used for bacterial removal.

Application example 2 Fe₃O₄@SiO₂@ Cs effect of removing heavy metals and bacteria in standard water sample

1. Experimental methods

The application example is that 1mL of standard solution to be removed of heavy metal and bacteria is taken, 0.05g of adsorbent is added, vortex oscillation is carried out for 30min, a magnet is used for abutting against the adsorbed aqueous solution, and after 10s, a pipette is used for taking out supernatant solution.

2. Results of the experiment

The experimental result shows that the adsorbent Fe₃O₄@SiO₂The supernatant solution after the @ Cs adsorption contains almost no heavy metals and bacteria.

Application example 3 Fe₃O₄@SiO₂Removal effect of @ Cs in application of heavy metals and bacteria in actual water sample

1. Experimental methods

In order to research the chitosan functional magnetic material Fe prepared by the invention₃O₄@SiO₂@ Cs is applied to adsorption effect of actual samples, 200 mu L of Tianjin City river eastern river water sample and Tianjin City river western region people park water sample are respectively collected by the application example and directly used for coating plates, Escherichia coli exists in both the two water samples, the concentration of the Escherichia coli in the sea river water sample is cf537 u/mL, the concentration of the Escherichia coli in the people park water sample is 597cfu/mL and exceeds the water quality sanitary requirement of national drinking water, and 2.5mg of Fe is weighed₃O₄@SiO₂And (5) subpackaging @ Cs, adding 20mL of water sample, shaking for 5min, and adsorbing the bacterial liquid for multiple times, wherein the water sample without the material is used as a blank.

2. Results of the experiment

The experimental results show that 2.5mg Fe₃O₄@SiO₂The @ Cs still has an adsorption effect on the 20mL water sample, and can still reach the adsorption balance (see figure 22) through four times of adsorption, and the obtained water sample microorganism indexes meet the national regulation of sanitary requirements on the quality of the drinking water.

The above description of the embodiments is only intended to illustrate the method of the invention and its core idea. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications will also fall into the protection scope of the claims of the present invention.

Claims (10)

1. A preparation method of a magnetic nano-adsorption material for simultaneously removing heavy metals and bacteria in water is characterized by comprising the following steps:

(1) preparation of Fe₃O₄A magnetic fluid;

(2) to the Fe obtained in step (1)₃O₄Adding a solvent into the magnetofluid to obtain a dispersion liquid;

(3) adding ammonia water and ethyl orthosilicate into the dispersion liquid obtained in the step (2), and reacting to obtain a magnetic material Fe₃O₄@SiO₂；

(4) Fe obtained in the step (3)₃O₄@SiO₂Mixing with chitosan solution, adding glutaraldehyde solution, and reacting to obtain magnetic nano-adsorption material Fe₃O₄@SiO₂@Cs。

2. The method according to claim 1, wherein the Fe in step (1)₃O₄The preparation of the magnetic fluid comprises the step of adding FeCl₃·6H₂O and FeSO₄·7H₂Adding O into solvent for dissolving, adding concentrated hydrochloric acid for ultrasonic treatment, and adjusting pH of the solution after ultrasonic treatment>10 hours, reacting, standing to obtain Fe₃O₄A magnetic fluid;

preferably, the FeCl₃·6H₂O and FeSO₄·7H₂The molar ratio of O is 4: 3;

preferably, the solvent is pure water;

preferably, the addition amount of the concentrated hydrochloric acid is 800-;

more preferably, the addition amount of the concentrated hydrochloric acid is 850 μ L;

preferably, the time of the ultrasonic treatment is 20-40 min;

more preferably, the time of the ultrasonic treatment is 30 min;

preferably, the pH adjustment is performed by adding ammonia;

preferably, the reaction is carried out under heating and stirring conditions;

more preferably, the temperature of the heating is 65-95 ℃;

most preferably, the temperature of the heating is 80 ℃;

more preferably, the stirring speed is 750-1250 r/min;

most preferably, the speed of stirring is 1000 r/min;

more preferably, the stirring time is 30-60 min;

most preferably, the stirring time is 40 min.

3. The method according to claim 1, wherein the solvent in step (2) comprises absolute ethanol, pure water;

preferably, the dosage of the anhydrous ethanol is 250-750 mL;

more preferably, the dosage of the absolute ethyl alcohol is 500 mL;

preferably, the amount of the pure water is 100-400 mL;

more preferably, the amount of the pure water is 250 mL.

4. The method according to claim 1, wherein the amount of the ammonia water used in the step (3) is 20-50mL, and the amount of the tetraethoxysilane used is 25-75 mL;

preferably, the dosage of the ammonia water is 38mL, and the dosage of the tetraethoxysilane is 50 mL;

preferably, the reaction in step (3) comprises a first stage reaction and a second stage reaction;

more preferably, the first stage reaction and the second stage reaction are carried out under heating and stirring conditions;

most preferably, the heating temperature of the first stage reaction is 40-80 ℃;

most preferably, the heating temperature of the first stage reaction is 60 ℃;

most preferably, the stirring speed of the first-stage reaction is 750-1250 r/min;

most preferably, the stirring speed of the first stage reaction is 1000 r/min;

most preferably, the stirring time of the first stage reaction is 1-2 h;

most preferably, the stirring time of the first stage reaction is 1.5 h;

most preferably, the heating temperature of the second stage reaction is 40-80 ℃;

most preferably, the heating temperature of the second stage reaction is 60 ℃;

most preferably, the stirring speed of the second-stage reaction is 250-750 r/min;

most preferably, the stirring speed of the second stage reaction is 500 r/min;

most preferably, the stirring time of the second stage reaction is 1-5 h;

most preferably, the stirring time for the second stage reaction is 3 h.

5. The method of claim 1, wherein in step (4) Fe₃O₄@SiO₂The dosage of the chitosan solution is 0.05-0.35g, the dosage of the chitosan solution is 40-80mL, and the dosage of the glutaraldehyde solution is 1-5 mL;

preferably, the Fe₃O₄@SiO₂The dosage of the chitosan solution is 0.2g, the dosage of the chitosan solution is 60mL, and the dosage of the glutaraldehyde solution is 3 mL;

more preferably, the chitosan solution is a 1% chitosan solution and the glutaraldehyde solution is a 5% glutaraldehyde solution;

most preferably, the 5% glutaraldehyde solution is added dropwise;

preferably, the reaction in step (4) is carried out under heating and stirring conditions;

more preferably, the temperature of the heating is 40-80 ℃;

most preferably, the temperature of the heating is 60 ℃;

more preferably, the stirring speed is 250-750 r/min;

most preferably, the stirring speed is 500 r/min;

more preferably, the stirring time is 20-40 min;

most preferably, the stirring time is 30 min.

6. A magnetic nano-adsorption material for simultaneously removing heavy metals and bacteria in water, which is prepared by the method of any one of claims 1 to 5;

preferably, the magnetic nano-adsorption material is structurally characterized in that: fe₃O₄Being a magnetic core, SiO₂The middle layer is the chitosan layer, and the outermost layer is the chitosan layer.

7. Use of the magnetic nano-adsorbent material of claim 6 for simultaneous removal of heavy metals and bacteria from water;

preferably, the heavy metals include Cr, As, Hg, Se, Pb, Cd, V, Co, Cu, Ni, Mn, Ag, Zn, Ba, Be;

more preferably, the heavy metal is Cr, As, Hg, Se, Pb, Cd;

preferably, the bacteria include gram positive and gram negative bacteria;

more preferably, the gram-positive bacterium is staphylococcus aureus;

more preferably, the gram-negative bacterium is escherichia coli.

8. Use of the magnetic nano-adsorbent material of claim 6 for the removal of heavy metals from water;

preferably, the heavy metals include Cr, As, Hg, Se, Pb, Cd, V, Co, Cu, Ni, Mn, Ag, Zn, Ba, Be;

more preferably, the heavy metal is Cr, As, Hg, Se, Pb, Cd.

9. Use of the magnetic nano-adsorbent material of claim 6 for the removal of bacteria from water;

preferably, the bacteria include gram positive and gram negative bacteria;

more preferably, the gram-positive bacterium is staphylococcus aureus;

more preferably, the gram-negative bacterium is escherichia coli.

10. Use of the magnetic nano-adsorbent material of claim 6 as a wastewater treatment agent in water treatment.

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