CN112337444A - Organic modified magnetic bentonite MB/CP and preparation method and application thereof - Google Patents
Organic modified magnetic bentonite MB/CP and preparation method and application thereof Download PDFInfo
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/06—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04
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- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
- B01J20/12—Naturally occurring clays or bleaching earth
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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Abstract
本发明公开一种有机改性磁性膨润土MB/CP及其制备方法和应用，采用微波共沉淀法和微波固液相法将制备得到的Fe3O4磁流体负载到天然钙基膨润土上，得到磁性钙基膨润土，再使用羧甲基纤维素钠和聚乙烯亚胺反应形成的接枝共聚物为有机修饰剂对磁性钙基膨润土进行表面修饰，得到有机改性磁性膨润土MB/CP。制备得到的有机改性磁性膨润土MB/CP结构中含有丰富的羟基等亲水基团，使其具有强烈的亲水性和分散性，在水中可长久保持悬浮状态；平均孔径和孔容有一定程度的增大，有利于其吸附性能的增强，对重金属离子Pb(Ⅱ)和Cd(Ⅱ)的吸附效果好；磁饱和强度高，磁分离能力与磁响应能力好，在外加磁场的作用下可实现快速的磁分离，具有良好的循环利用性能。
The invention discloses an organic modified magnetic bentonite MB/CP and a preparation method and application thereof. The prepared Fe 3 O 4 magnetic fluid is loaded on natural calcium-based bentonite by a microwave co-precipitation method and a microwave solid-liquid phase method to obtain Magnetic calcium-based bentonite, and then use the graft copolymer formed by the reaction of sodium carboxymethyl cellulose and polyethyleneimine as an organic modifier to modify the surface of the magnetic calcium-based bentonite to obtain organically modified magnetic bentonite MB/CP. The prepared organically modified magnetic bentonite MB/CP structure is rich in hydrophilic groups such as hydroxyl groups, which makes it have strong hydrophilicity and dispersibility, and can remain suspended in water for a long time; the average pore size and pore volume have a certain The increase of the degree of adsorption is conducive to the enhancement of its adsorption performance, and the adsorption effect of heavy metal ions Pb(II) and Cd(II) is good; the magnetic saturation strength is high, the magnetic separation ability and magnetic response ability are good, and under the action of an external magnetic field It can realize fast magnetic separation and has good recycling performance.
Description
Technical Field
The invention belongs to the technical field of bentonite deep processing, and particularly relates to organically modified magnetic bentonite MB/CP and a preparation method and application thereof.
Background
In recent years, due to the rapid development of industries such as mining, printing and dyeing, electroplating and the like, a large amount of heavy metal ion wastewater is generated. Heavy metals are characterized by difficult degradation, easy accumulation, large toxicity and the like, have wide sources, and often coexist in mining wastewater, electroplating wastewater and various environmental sewage. The excessive heavy metal ions in the water environment not only cause serious pollution to the water environment, but also cause serious harm to aquatic organisms and human beings through a food chain. Pb (II) and Cd (II) belong to heavy metals, the form of Pb (II) and Cd (II) in nature can be changed continuously, the spatial position is changed continuously, and finally, different degrees of injuries and damages are generated to human nervous tissues, digestive systems and the like through enrichment and dispersion.
The negative magnetic technology is characterized in that a strongly magnetic substance with good dispersibility is introduced into a weakly magnetic or non-magnetic material to construct a composite material so as to improve the saturation magnetism of the material, so that the negative magnetic material can be rapidly separated under the action of an external magnetic field. In order to avoid secondary pollution to the ecological environment caused by the waste of the bentonite and realize the repeated cyclic utilization of the bentonite adsorption material, the bentonite needs to be negatively magnetized so as to improve the solid-liquid separation capacity of the bentonite. Wherein, Fe3O4The synthesis is simple and easy, the cost is low, the magnetic saturation intensity is good, the magnetic separation performance is stable, and Fe3O4Has a certain adsorption capacity to pollutants, so that Fe3O4Is one of the particles currently commonly used for negative magnetism. Such as Wang superman, by using Fe3O4Performing negative magnetism on the bentonite, wherein the adding amount of the prepared magnetic bentonite is 0.5 g.L-1The maximum adsorption capacity of Langumir of the tetracycline is increased to 147mg g-1The adsorbent was completely separated from the solution at 35 s.
But Fe3O4The performance of the Fe-Fe alloy is not stable enough, the Fe-Fe alloy is easy to oxidize and agglomerate when contacting with air, and the Fe alloy is Fe3O4Can occupy partial adsorption points on the magnetic bentonite, thereby reducing the adsorption effect of the bentonite on heavy metal ions and influencing the magnetic stability and the solid-liquid separation capability of the magnetic bentonite. In order to solve the problems of the bentonite negative magnetism, an organic compound can be added into the magnetic bentonite for modification so as to prepare an organic magnetic bentonite composite adsorbing material with more complete functions, so that the problems of solid-liquid separation damage and magnetic stability reduction of the magnetic bentonite can be solved, and the adsorption capacity of the magnetic bentonite on heavy metal ions can be synergistically improved. For example, the cationic surfactant cetyl trimethyl ammonium bromide (CTMAB) and the amphoteric surfactant Sodium Dodecyl Sulfate (SDS) are combined to carry out organic modification on the magnetic bentonite to obtain the amphoteric compound modified magnetic bentonite BS-CT-MBT, the adsorption effect of the BS-CT-MBT on phenol is discussed, and the result shows that the adsorption capacity of the BS-CT-MBT on phenol is greatly improved compared with that of pure bentonite, and the adsorption capacity is 16.34mg g-1Increased to 205.81mg g-1Meanwhile, the solid-liquid separation is relatively thorough within 30 s. It is assumed that, in the process of organically modifying the magnetic bentonite, if the physical and chemical characteristics of organic matters are not considered, the adsorption capacity of the prepared organically modified magnetic bentonite to heavy metal ions cannot achieve the expected adsorption effect. Therefore, not only a proper amount of Fe should be added3O4The nano particles and proper organic modifier are selected to obtain the organic modified magnetic bentonite composite material which not only has magnetic separation capability, but also can improve the adsorption performance of heavy metals.
At present, the adsorption effect of the adsorption material for adsorbing heavy metal ions Pb (II) and Cd (II) is poor, so that bentonite is taken as a carrier, and a proper amount of Fe is added3O4The nano particles are modified by selecting a proper organic modifier, and the organic modified magnetic bentonite composite material with good adsorption performance and good recycling performance on heavy metal ions Pb (II) and Cd (II) is necessary to be prepared.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the organic modified magnetic bentonite MB/CP and the preparation method and the application thereof, which can improve the adsorption performance of heavy metal ions Pb (II) and Cd (II) and can realize rapid magnetic separation under the condition of an external magnetic field so as to recycle for many times.
The technical scheme of the invention is as follows:
a method for preparing organic modified magnetic bentonite MB/CP adopts a microwave coprecipitation method to prepare magnetic nano Fe3O4Loading the particles on natural calcium bentonite (RB) to obtain magnetic calcium bentonite (MB), and performing surface modification on the magnetic calcium bentonite (MB) by using a graft copolymer formed by reaction of sodium carboxymethylcellulose (CMC) and Polyethyleneimine (PEI) as an organic modifier to obtain the organically modified magnetic bentonite MB/CP. The graft copolymerization of CMC and PEI is shown in FIG. 2.
The principle of the invention is as follows:
chitosan can not modify bentonite by using pure natural chitosan so far, and commercialized chitosan needs to be purchased; and polyethyleneimine may be obtained by polymerization of monomers. The cost of chitosan is 130 yuan/kg, while the cost of polyethyleneimine is as low as 8 yuan/kg, so that the cost is lower compared with that of chitosan; meanwhile, polyethyleneimine is more environment-friendly, is mostly of an amino structure, can be better combined with sodium carboxymethylcellulose, is more compact in combination, and cannot cause secondary pollution to the environment. The adsorption capacity of the sodium carboxymethylcellulose and the chitosan modified bentonite to heavy metals reaches 420mg g-1The adsorption capacity of the sodium carboxymethylcellulose and the polyethyleneimine modified bentonite to heavy metals can reach 760mg g-1The adsorption effect is better, and the removal rate and the adsorption capacity are higher.
As a preferred technical solution, the method specifically comprises the following steps:
(1)Fe3O4preparing magnetic fluid: FeCl is added2·4H2O and FeCl3·6H2Placing the dissolved O in a microwave solid-liquid synthesizer for microwave heating reaction for 0.5-2 h, cooling to room temperature after the reaction is stopped, and obtaining Fe3O4A magnetic fluid;
(2) preparation of organic modifier: respectively dissolving sodium carboxymethylcellulose and polyethyleneimine in water, and stirring until the solution is uniform to obtain a sodium carboxymethylcellulose solution and a polyethyleneimine solution;
(3) preparing organic modified magnetic bentonite MB/CP: adding sodium carboxymethylcellulose solution into Fe3O4And (3) placing the magnetic fluid in a microwave solid-liquid synthesizer for reaction for 0.5-1 h, then adding a polyethyleneimine solution for continuous reaction for 0.5-1 h, then adding natural calcium bentonite for continuous reaction for 0.5-1 h, cooling to room temperature after the reaction is finished, washing and drying to obtain the organic modified magnetic bentonite MB/CP.
The process flow chart of the invention for preparing the organic modified magnetic bentonite MB/CP is shown in figure 1.
As a preferable aspect of the present invention, in the step (1), FeCl2·4H2O and FeCl3·6H2The mass ratio of O is 1: 1.5-2.2, and the setting parameters and reaction conditions of the microwave solid-liquid synthesizer are as follows: at 50-60 ℃, 500-600W, mixing the phases (0), and stirring at a speed of 200-600 rpm; the reaction process is as follows: carrying out reaction for 2-10 min in a microwave preheating stage, adding an alkaline solution to adjust the pH value of a reaction system to 7-13, then carrying out reaction for 0.5-1 h, ageing for 0.3-1 h after the reaction is finished, and cooling to room temperature; the alkaline solution is any one of ammonia water, sodium hydroxide and potassium hydroxide.
Preferably, in the step (2), the mass concentration of the sodium carboxymethyl cellulose solution and the polyethyleneimine solution is 0.1-10%, and before use, the sodium carboxymethyl cellulose solution is diluted by 2-4 times with water, and the polyethyleneimine solution is diluted by 1-3 times.
Preferably, in the step (3), the ratio of the amounts of the sodium carboxymethylcellulose and the polyethyleneimine added is 0.3-1.2: 1.
Preferably, in the step (3), Fe3O4The ratio of the amount of the substance(s) to the sum of the amounts of the substances of sodium carboxymethylcellulose, polyethyleneimine and natural calcium bentonite added is 2.5-17.5: 100.
Preferably, in the step (3), the set parameters and reaction conditions of the microwave solid-liquid synthesizer are as follows: 50-60 ℃, 500-600W, mixed phase (0), and stirring speed of 200-600 rpm.
Further, the structure of the organic modified magnetic bentonite MB/CP prepared by the method is determined, the organic modified magnetic bentonite MB/CP takes natural calcium bentonite as a carrier and loads magnetic nano Fe3O4Particles and a quaternary composite material with the surface modified by organic modifiers of sodium carboxymethyl cellulose and polyethyleneimine, and the structure of the quaternary composite material is shown in figure 3; in FIG. 3, the interlayer is natural calcium bentonite, and the substance in the square frame is single-grain magnetic Fe3O4Structural unit of particles, single grain magnetic Fe3O4The particle building block is shown in figure 4.
Further, the organic modified magnetic bentonite MB/CP prepared by the method is subjected to physical and chemical property detection, the interlayer spacing of the organic modified magnetic bentonite MB/CP is 1.30-1.77 nm, and the BET specific surface area is 70-86 m2·g-1The pore volume is 0.48-0.64cm3·g-1Average pore diameter of 10.4-12.5nm and saturation magnetization value of 17.87-19.23emu g-1Under the action of an external magnetic field, the solid-liquid separation and recovery of 10-12s can be realized.
The application of the organic modified magnetic bentonite MB/CP is used for adsorbing heavy metal ions Pb (II) and Cd (II).
The invention has the beneficial effects that:
(1) the invention uses the graft copolymer formed by the reaction of sodium carboxymethylcellulose and polyethyleneimine as an organic modifier to carry out surface modification on the magnetic calcium bentonite, and the characterization result of XPS shows that the sodium carboxymethylcellulose and the polyethylene glycolGraft copolymer generated by ene imine reaction to Fe3O4The magnetic core has a protection effect and can protect the stability of the magnetic core; according to the VSM representation result and the magnetic separation effect graph, the magnetic saturation intensity of the MB/CP is greatly enhanced, the magnetic separation speed is remarkably improved, the solid-liquid separation speed is high, and the repeated utilization can be realized for many times.
(2) The organic modified magnetic bentonite MB/CP has good adsorption performance on heavy metal ions Pb (II) and Cd (II), the adsorption equilibrium time of the MB/CP on the Pb (II) and the Cd (II) is 43min and 37min respectively, the removal rate of the MB/CP on the Pb (II) and the Cd (II) is 99% when the MB/CP is in adsorption equilibrium, and the adsorption speed and the removal rate on the Pb (II) and the Cd (II) are far higher than those of the MB and RB; meanwhile, the MB/CP also has good recycling performance, and the removal rate of the MB/CP on Pb (II) and Cd (II) is still kept above 90% after 5 times of circulation.
(3) The invention uses the graft copolymer formed by the reaction of sodium carboxymethylcellulose and polyethyleneimine as an organic modifier to carry out surface modification on the magnetic calcium bentonite, and after the organic modification of organic substances CMC and PEI, on one hand, the surface of MB/CP contains more-OH and-NH2The functional groups are equal, so that the complexing effect on Pb (II) and Cd (II) can be realized; on the other hand, the organic modification enlarges the pore volume and the average pore diameter of the MB/CP, and can more quickly and effectively adsorb Pb (II) and Cd (II), so that the adsorption capacity of the MB/CP on the Pb (II) and the Cd (II) is better than that of the MB and the RB.
Drawings
FIG. 1 is a process flow diagram of the present invention for preparing organically modified magnetic bentonite MB/CP;
FIG. 2 is a diagram of a graft copolymerization reaction of CMC and PEI;
FIG. 3 is a structural view of an organically modified magnetic bentonite MB/CP according to the present invention;
FIG. 4 shows a single grain magnetic Fe3O4A particle structure unit;
FIG. 5 is a XPS survey spectrum of RB, MB and MB/CP;
FIG. 6 is a spectrum of Fe2p for MB and MB/CP;
FIG. 7 is a plot of a Fe2p spectral peak fit for MB;
FIG. 8 is a plot of a MB/CP peak fit of the Fe2p spectrum;
FIG. 9 is an XRD diffraction pattern of RB, MB and MB/CP;
FIG. 10 shows the IR spectrum analysis of RB, MB and MB/CP;
FIGS. 11-13 are N of RB, MB, and MB/CP2Adsorption-desorption isotherms, wherein the corresponding small graphs in the graph are the aperture distribution graphs of RB, MB and MB/CP respectively;
FIG. 14 is a hysteresis loop of MB and MB/CP under the conditions of a magnetic field strength of-30 KOe to 30KOe and a temperature of 25 ℃;
FIGS. 15-17 are SEM topographs at 10kv for RB, MB and MB/CP;
FIGS. 18 to 19 are graphs showing the adsorption process of Pb (II) and Cd (II) by RB, MB and MB/CP at different adsorption times;
FIGS. 20-21 are graphs of the adsorption process of Pb (II) and Cd (II) by RB, MB and MB/CP at different initial concentrations of the solution;
FIGS. 22-23 are graphs of the adsorption process of RB, MB and MB/CP for Pb (II) and Cd (II) at different initial solution pH;
FIGS. 24-25 are graphs of the adsorption process of RB, MB and MB/CP for Pb (II) and Cd (II) at different HA concentrations;
FIGS. 26-27 are graphs showing the results of 5 cycles of adsorption of RB, MB and MB/CP to Pb (II) and Cd (II).
Detailed Description
The invention will be further described in detail with reference to the following detailed description and the accompanying drawings, but the invention is not limited to the scope of protection.
Example 1
A method for preparing organic modified magnetic bentonite MB/CP adopts a microwave coprecipitation method to prepare magnetic nano Fe3O4Loading the particles on natural calcium bentonite to obtain magnetic calcium bentonite, and performing surface modification on the magnetic calcium bentonite by using a graft copolymer formed by reaction of sodium carboxymethylcellulose and polyethyleneimine as an organic modifier to obtain the organically modified magnetic bentonite MB/CP. The method specifically comprises the following steps:
(1)Fe3O4preparing magnetic fluid: mixing the materialsFeCl in an amount ratio of 1:1.52·4H2O and FeCl3·6H2And (3) completely dissolving O, and placing the dissolved O in a microwave solid-liquid synthesizer, wherein the set parameters and reaction conditions of the microwave solid-liquid synthesizer are as follows: 50 ℃, 500W, mixed phase (0), stirring speed 200 rpm; the reaction process is as follows: reacting for 2min at microwave preheating stage, adding ammonia water to adjust pH value of reaction system to 7, reacting for 0.5h, aging for 0.5h after reaction, cooling to room temperature to obtain Fe3O4A magnetic fluid;
(2) preparation of organic modifier: dissolving sodium carboxymethylcellulose and polyethyleneimine with water respectively, stirring until the solution is uniform to obtain 0.1% sodium carboxymethylcellulose solution and polyethyleneimine solution, storing at 2 deg.C, diluting with water for 2 times before use, and diluting with polyethyleneimine solution for 2 times to obtain sodium carboxymethylcellulose solution and polyethyleneimine solution;
(3) preparing organic modified magnetic bentonite MB/CP: adding sodium carboxymethylcellulose solution into Fe3O4And (3) placing the magnetic fluid in a microwave solid-liquid synthesizer for reaction for 0.5h, wherein the set parameters and reaction conditions of the microwave solid-liquid synthesizer are as follows: mixing the phases (0) at 50 ℃ and 500W at a stirring speed of 200rpm, adding a polyethyleneimine solution to continuously react for 0.5h, controlling the mass ratio of the added sodium carboxymethylcellulose to the polyethyleneimine to be 0.3:1, adding natural calcium bentonite to continuously react for 0.5h, and controlling Fe3O4The ratio of the amount of the substances to the sum of the amounts of the substances of the sodium carboxymethylcellulose, the polyethyleneimine and the natural calcium bentonite is 2.5:100, the mixture is cooled to room temperature after the reaction is finished, then the mixture is alternately washed for 2 times by using absolute ethyl alcohol and deionized water, and then the mixture is placed in a vacuum drying oven to be dried for 24 hours at 50 ℃ in vacuum, so that the organic modified magnetic bentonite MB/CP is obtained.
Example 2
A method for preparing organic modified magnetic bentonite MB/CP adopts a microwave coprecipitation method to prepare magnetic nano Fe3O4Loading the particles on natural calcium bentonite to obtain magnetic calcium bentonite, and mixing with sodium carboxymethylcelluloseThe grafted copolymer formed by the reaction of polyethyleneimine is used as an organic modifier to carry out surface modification on the magnetic calcium bentonite, so that the organically modified magnetic bentonite MB/CP can be obtained. The method specifically comprises the following steps:
(1)Fe3O4preparing magnetic fluid: FeCl with the amount ratio of the substances being 1:1.72·4H2O and FeCl3·6H2And (3) completely dissolving O, and placing the dissolved O in a microwave solid-liquid synthesizer, wherein the set parameters and reaction conditions of the microwave solid-liquid synthesizer are as follows: 52 ℃, 520W, mixed phase (0), stirring speed 300 rpm; the reaction process is as follows: reacting for 4min at microwave preheating stage, adding sodium hydroxide to adjust pH value of reaction system to 8, reacting for 0.6h, aging for 1h after reaction, cooling to room temperature to obtain Fe3O4A magnetic fluid;
(2) preparation of organic modifier: dissolving sodium carboxymethylcellulose and polyethyleneimine with water respectively, stirring until the solution is uniform to obtain a sodium carboxymethylcellulose solution and a polyethyleneimine solution with mass concentration of 1%, storing at 3 ℃, diluting the sodium carboxymethylcellulose solution by 3 times with water before use, and diluting the polyethyleneimine solution by 1 time to obtain a sodium carboxymethylcellulose solution and a polyethyleneimine solution;
(3) preparing organic modified magnetic bentonite MB/CP: adding sodium carboxymethylcellulose solution into Fe3O4And (3) placing the magnetic fluid in a microwave solid-liquid synthesizer for reaction for 0.6h, wherein the set parameters and reaction conditions of the microwave solid-liquid synthesizer are as follows: mixing the phases (0) at 52 ℃ and 520W at a stirring speed of 300rpm, adding a polyethyleneimine solution to continuously react for 0.6h, controlling the mass ratio of the added sodium carboxymethylcellulose to the polyethyleneimine to be 0.5:1, adding natural calcium bentonite to continuously react for 0.6h, and controlling Fe3O4The ratio of the amount of the substances to the sum of the amounts of the substances of the sodium carboxymethylcellulose, the polyethyleneimine and the natural calcium bentonite is 5:100, the mixture is cooled to room temperature after the reaction is finished, then the mixture is alternately washed for 2-6 times by using absolute ethyl alcohol and deionized water, and then the mixture is placed in a vacuum drying oven to be dried for 20 hours at 52 ℃, so that the organic modified magnetic bentonite MB/CP is obtained.
Example 3
A method for preparing organic modified magnetic bentonite MB/CP adopts a microwave coprecipitation method to prepare magnetic nano Fe3O4Loading the particles on natural calcium bentonite to obtain magnetic calcium bentonite, and performing surface modification on the magnetic calcium bentonite by using a graft copolymer formed by reaction of sodium carboxymethylcellulose and polyethyleneimine as an organic modifier to obtain the organically modified magnetic bentonite MB/CP. The method specifically comprises the following steps:
(1)Fe3O4preparing magnetic fluid: FeCl with the amount ratio of the substances being 1:1.82·4H2O and FeCl3·6H2And (3) completely dissolving O, and placing the dissolved O in a microwave solid-liquid synthesizer, wherein the set parameters and reaction conditions of the microwave solid-liquid synthesizer are as follows: at 54 ℃, 530W, mixed phase (0), stirring speed of 350 rpm; the reaction process is as follows: reacting for 5min at microwave preheating stage, adding ammonia water to adjust pH value of reaction system to 10, reacting for 0.7h, aging for 0.9h after reaction, cooling to room temperature to obtain Fe3O4A magnetic fluid;
(2) preparation of organic modifier: dissolving sodium carboxymethylcellulose and polyethyleneimine with water respectively, stirring until the solution is uniform to obtain a sodium carboxymethylcellulose solution and a polyethyleneimine solution with mass concentration of 3%, storing at 0 ℃, diluting the sodium carboxymethylcellulose solution by 3 times with water before use, and diluting the polyethyleneimine solution by 3 times to obtain a sodium carboxymethylcellulose solution and a polyethyleneimine solution;
(3) preparing organic modified magnetic bentonite MB/CP: adding sodium carboxymethylcellulose solution into Fe3O4And (3) placing the magnetic fluid in a microwave solid-liquid synthesizer for reaction for 0.7h, wherein the set parameters and reaction conditions of the microwave solid-liquid synthesizer are as follows: mixing the phases (0) at 54 ℃ and 530W at a stirring speed of 350rpm, adding a polyethyleneimine solution to continuously react for 0.7h, controlling the mass ratio of the added sodium carboxymethylcellulose to the polyethyleneimine to be 0.6:1, adding natural calcium bentonite to continuously react for 0.7h, and controlling Fe3O4The amount of the substance(s) is equal to the amount of the added sodium carboxymethyl cellulose, polyethyleneimine and natural calcium-based bentoniteThe ratio of the total amount of the substances for moistening the soil is 10:100, after the reaction is finished, the mixture is cooled to room temperature, then is alternately washed for 3 times by absolute ethyl alcohol and deionized water, and is then placed in a vacuum drying oven for vacuum drying for 17 hours at the temperature of 53 ℃, and the organic modified magnetic bentonite MB/CP is obtained.
Example 4
A method for preparing organic modified magnetic bentonite MB/CP adopts a microwave coprecipitation method to prepare magnetic nano Fe3O4Loading the particles on natural calcium bentonite to obtain magnetic calcium bentonite, and performing surface modification on the magnetic calcium bentonite by using a graft copolymer formed by reaction of sodium carboxymethylcellulose and polyethyleneimine as an organic modifier to obtain the organically modified magnetic bentonite MB/CP. The method specifically comprises the following steps:
(1)Fe3O4preparing magnetic fluid: FeCl with the amount ratio of the substances being 1:1.92·4H2O and FeCl3·6H2And (3) completely dissolving O, and placing the dissolved O in a microwave solid-liquid synthesizer, wherein the set parameters and reaction conditions of the microwave solid-liquid synthesizer are as follows: 55 ℃, 550W, mixed phase (0), stirring speed 400 rpm; the reaction process is as follows: reacting for 6min at microwave preheating stage, adding potassium hydroxide to adjust pH value of reaction system to 12, reacting for 0.8h, aging for 0.8h after reaction, cooling to room temperature to obtain Fe3O4A magnetic fluid;
(2) preparation of organic modifier: dissolving sodium carboxymethylcellulose and polyethyleneimine with water respectively, stirring until the solution is uniform to obtain a sodium carboxymethylcellulose solution and a polyethyleneimine solution with mass concentration of 5%, storing at 4 ℃, diluting the sodium carboxymethylcellulose solution by 4 times with water before use, and diluting the polyethyleneimine solution by 3 times to obtain a sodium carboxymethylcellulose solution and a polyethyleneimine solution;
(3) preparing organic modified magnetic bentonite MB/CP: adding sodium carboxymethylcellulose solution into Fe3O4And (3) placing the magnetic fluid in a microwave solid-liquid synthesizer for reaction for 0.8h, wherein the set parameters and reaction conditions of the microwave solid-liquid synthesizer are as follows: 55 ℃ at 550W, mixing the phases (0), stirring at 400rpm, and then adding polyethyleneimineThe solution is continuously reacted for 0.8h, the ratio of the added substances of the sodium carboxymethyl cellulose to the added substances of the polyethyleneimine is controlled to be 0.8:1, then the natural calcium bentonite is added for continuous reaction for 0.8h, and the Fe is controlled3O4The ratio of the amount of the substances to the sum of the amounts of the substances added, namely the sodium carboxymethyl cellulose, the polyethyleneimine and the natural calcium bentonite, is 12:100, the mixture is cooled to room temperature after the reaction is finished, then the mixture is alternately washed for 4 times by using absolute ethyl alcohol and deionized water, and then the mixture is placed in a vacuum drying oven to be dried for 15 hours at 55 ℃, so that the organic modified magnetic bentonite MB/CP is obtained.
Example 5
A method for preparing organic modified magnetic bentonite MB/CP adopts a microwave coprecipitation method to prepare magnetic nano Fe3O4Loading the particles on natural calcium bentonite to obtain magnetic calcium bentonite, and performing surface modification on the magnetic calcium bentonite by using a graft copolymer formed by reaction of sodium carboxymethylcellulose and polyethyleneimine as an organic modifier to obtain the organically modified magnetic bentonite MB/CP. The method specifically comprises the following steps:
(1)Fe3O4preparing magnetic fluid: FeCl with the amount ratio of the substances being 1:22·4H2O and FeCl3·6H2And (3) completely dissolving O, and placing the dissolved O in a microwave solid-liquid synthesizer, wherein the set parameters and reaction conditions of the microwave solid-liquid synthesizer are as follows: 580W at 57 ℃, mixed phase (0) and stirring speed of 500 rpm; the reaction process is as follows: reacting for 8min at microwave preheating stage, adding sodium hydroxide to adjust pH value of reaction system to 13, reacting for 0.9h, aging for 0.3h after reaction, cooling to room temperature to obtain Fe3O4A magnetic fluid;
(2) preparation of organic modifier: dissolving sodium carboxymethylcellulose and polyethyleneimine with water respectively, stirring until the solution is uniform to obtain 8% sodium carboxymethylcellulose solution and polyethyleneimine solution, storing at 2 deg.C, diluting with water for 2 times before use, and diluting polyethyleneimine solution for 1 time to obtain sodium carboxymethylcellulose solution and polyethyleneimine solution;
(3) organic modified magnetPreparing bentonite MB/CP: adding sodium carboxymethylcellulose solution into Fe3O4And (3) placing the magnetic fluid in a microwave solid-liquid synthesizer for reaction for 0.9h, wherein the set parameters and reaction conditions of the microwave solid-liquid synthesizer are as follows: at 57 ℃, 580W, mixing phase (0), stirring speed 500rpm, adding polyethyleneimine solution to continue reacting for 0.9h, controlling the ratio of the added sodium carboxymethylcellulose to the polyethyleneimine to be 1:1, adding natural calcium bentonite to continue reacting for 0.9h, and controlling Fe3O4The ratio of the amount of the substances to the sum of the amounts of the substances of the sodium carboxymethylcellulose, the polyethyleneimine and the natural calcium bentonite is 15:100, the mixture is cooled to room temperature after the reaction is finished, then the mixture is alternately washed for 5 times by using absolute ethyl alcohol and deionized water, and then the mixture is placed in a vacuum drying oven to be dried for 13 hours at 58 ℃ in vacuum, so that the organic modified magnetic bentonite MB/CP is obtained.
Example 6
A method for preparing organic modified magnetic bentonite MB/CP adopts a microwave coprecipitation method to prepare magnetic nano Fe3O4Loading the particles on natural calcium bentonite to obtain magnetic calcium bentonite, and performing surface modification on the magnetic calcium bentonite by using a graft copolymer formed by reaction of sodium carboxymethylcellulose and polyethyleneimine as an organic modifier to obtain the organically modified magnetic bentonite MB/CP. The method specifically comprises the following steps:
(1)Fe3O4preparing magnetic fluid: FeCl with the amount ratio of the substances being 1:2.22·4H2O and FeCl3·6H2And (3) completely dissolving O, and placing the dissolved O in a microwave solid-liquid synthesizer, wherein the set parameters and reaction conditions of the microwave solid-liquid synthesizer are as follows: 60 ℃, 600W, mixed phase (0), stirring speed 600 rpm; the reaction process is as follows: reacting for 10min at the microwave preheating stage, adding ammonia water to adjust the pH value of the reaction system to 9, then reacting for 1h, aging for 0.7h after the reaction is finished, and cooling to room temperature to obtain Fe3O4A magnetic fluid;
(2) preparation of organic modifier: dissolving sodium carboxymethylcellulose and polyethyleneimine with water respectively, stirring until the solution is uniform to obtain a sodium carboxymethylcellulose solution and a polyethyleneimine solution with mass concentration of 10%, storing at 3 ℃, diluting the sodium carboxymethylcellulose solution by 3 times with water before use, and diluting the polyethyleneimine solution by 2 times to obtain a sodium carboxymethylcellulose solution and a polyethyleneimine solution;
(3) preparing organic modified magnetic bentonite MB/CP: adding sodium carboxymethylcellulose solution into Fe3O4And (3) placing the magnetic fluid in a microwave solid-liquid synthesizer for reaction for 1h, wherein the microwave solid-liquid synthesizer has the following setting parameters and reaction conditions: 60 ℃, 600W, mixing phase (0), stirring at a speed of 600rpm, adding a polyethyleneimine solution, continuously reacting for 1h, controlling the mass ratio of the added sodium carboxymethylcellulose to the polyethyleneimine to be 1.2:1, adding natural calcium bentonite, continuously reacting for 1h, and controlling Fe3O4The ratio of the amount of the substances to the sum of the amounts of the substances added in the sodium carboxymethyl cellulose, the polyethyleneimine and the natural calcium bentonite is 17.5:100, the mixture is cooled to room temperature after the reaction is finished, then the mixture is alternately washed for 6 times by absolute ethyl alcohol and deionized water, and then the mixture is placed in a vacuum drying oven to be dried for 10 hours at 60 ℃, so that the organic modified magnetic bentonite MB/CP is obtained.
Firstly, material characterization of organic modified magnetic bentonite:
characterization analysis method
X-ray Photoelectron Spectroscopy (XPS). The test sample is irradiated with X-rays, and inner electrons around atoms or molecules in the test sample are excited to emit photoelectrons. The energy spectrum diagram of photoelectrons is made by taking the kinetic energy/binding energy of the photoelectrons as an abscissa and taking the relative intensity as an ordinate, and the constituent elements of the surface of the material and the chemical states of the elements are determined by analyzing the surface binding energy of the material.
X-Ray Diffraction (XRD). A D/max 2500V type X-ray diffractometer of Shimadzu corporation in Japan is adopted to characterize a sample so as to obtain the properties of the prepared material, such as phase characteristics, crystal structure and the like, and the instrument controls the tube voltage to be 40kV, the tube current to be 20mA, the scanning angle to be 2 theta to be 5-80 degrees and the scanning speed to be 10 DEG/min in the operation process.
Fourier infrared spectrum (Fourier Transform-free Spectrometer, FT-IR). The method comprises the steps of adopting a NicoleetiS 50 type Fourier infrared spectrometer of American Saimer Feishale company to analyze changes of functional groups and magnetic nanoparticles of the material, wherein the scanning angle is 4000-400 cm-1。
Fully automated specific surface and pore analysis (Brunner-Emmet-Teller, BET). The specific surface area, pore volume and pore size distribution of bentonite and composite bentonite are analyzed by using a NOVA4200E full-automatic specific surface and pore analyzer of Congta instruments, USA, and the sample is degassed at 100 deg.C in advance for not less than 6h under vacuum condition before testing.
Vibrating Sample Magnetometers (VSM). The magnetic saturation strength of the sample is measured by adopting a 7410 type vibration sample magnetometer of the United states Hubin company, the test temperature is 298K, the magnetic field scanning range is-20000 Oe, and the stepping rate is 6 Oe/s.
Scanning Electron Microscope (SEM). Before SEM characterization, the sample needs to be dispersed by ethanol, and after the sample is completely dispersed, the sample is placed under a microscope for appearance observation.
(II) characterization analysis results (characterization analysis of the organically modified magnetic bentonite MB/CP prepared in example 3)
XPS full spectrum analysis results are shown in FIG. 5
XPS survey spectra of RB, MB and MB/CP are shown in FIG. 5. As can be seen from the figure, the appearance positions of characteristic peaks of O, Al, Si, C, Ca and the like on MB and MB/CP are consistent with the characteristic peak of RB, which indicates that the structure of bentonite is kept intact and is not damaged in the process of carrying out negative magnetic and organic modification on MB and MB/CP. Moreover, a new peak of the binding energy of Fe2p and N1s appears on the full spectrum of MB and MB/CP, and the characteristic peak of the binding energy of Fe2p is magnetic Fe3O4A characteristic peak of (1), which indicates Fe3O4Have been successfully loaded on MB and MB/CP; the characteristic peak of the binding energy of N1s contained in MB/CP indicates that the corresponding components of CMC and PEI have bound to MB.
The results of Fe2p mapping of MB and MB/CP are shown in FIGS. 6-8
The Fe2p spectra of MB and MB/CP are shown in FIG. 6; the peak-fit plot of the Fe2p spectrum for MB is shown in FIG. 7, and the peak-fit plot of the Fe2p spectrum for MB/CP is shown in FIG. 8.
As can be seen from FIG. 6, MB shows a new characteristic peak at 718.4ev, where the characteristic peak is Fe2O3Characteristic wake peaks of (1). As can be seen by comparing FIG. 7 and FIG. 8, Fe of MB and MB/CP3+With Fe2+The characteristic peaks of (A) appear at 711.7ev, 725.1ev, 710.3ev and 723.4ev respectively, and Fe in MB is calculated3+With Fe2+The frontal area accounts for 80.2 percent and 19.8 percent respectively, and Fe in MB/CP3+With Fe2+The ratio of the frontal area of (A) to (B) was 67.4% and 32.6%, respectively, from which it was found that Fe was contained in MB/CP3+Area of front and Fe2+The frontal area ratio of 2:1, and Fe in MB3+Area of front and Fe2+The frontal area ratio of (a) is greater than 2: 1. this result indicates Fe in MB3O4The Fe in the MB/CP is effectively protected by adding organic modifiers such as CMC, PEI and the like due to the long-time exposure and oxidation in the air3O4Not oxidized.
XRD analysis results are shown in FIG. 9
FIG. 9 is an XRD diffraction pattern of RB, MB and MB/CP. As can be seen from the figure, the basic structure of the bentonite is not destroyed after MB and MB/CP are negatively magnetically and organically modified, and the characteristic peaks (2 θ ═ 5.74 ° and 19.80 °) of montmorillonite and (2 θ ═ 21.9 °) of quartz in the bentonite still remain in MB and MB/CP. Diffraction peaks at 30.08 °, 35.41 °, 43.05 °, 52.24 °, 56.94 °, 62.52 ° and 74.72 ° 2 θ, respectively, with Fe3O4The diffraction crystal planes at (220), (311), (400), (422), (511), (440) and (533) correspond to each other, and Fe is explained3O4The surface loading of MB and MB/CP was successful. Wherein, the maps of MB and MB/CP have almost no impurity peak, and the crystal purity is higher after the bentonite is organically modified by negative magnetism and CMC and PEI. In the organic composite bentonite MB/CP, the bentonite occupies the main position, and simultaneously, due to the addition of organic CMC and PEI, Fe3O4Part of the characteristic peak is masked, affecting the transmission of X-rays, so that the Fe of MB/CP3O4The characteristic peak shape and the peak intensity are weakened.The layer spacing (d) of RB, MB and MB/CP can be calculated according to the Bragg equation001) 1.54nm, 1.30nm and 1.77nm, respectively. Wherein the interlayer spacing of MB is reduced compared to RB because Fe is added3O4Ca on RB in the preparation of MB2+Quilt H+Replacement; after the MB is organically modified by the CMC and the PEI, the interlayer spacing of the MB/CP is slightly increased, which shows that the CMC and the PEI which are organic matters do not enter the interlayer of the bentonite, but are loaded on the surface of the bentonite, so that the interlayer spacing is slightly increased.
FT-IR analysis results are shown in FIG. 10
Infrared spectroscopic analysis of RB, MB and MB/CP is shown in FIG. 10. The IR spectra of RB, MB and MB/CP are similar, as illustrated in Fe3O4In the process of organically modifying RB, CMC and PEI, the bentonite is used as a basic skeleton, and the structure of the bentonite is not damaged. 3620cm in infrared spectral curves of RB, MB and MB/CP–1、3435cm–1The absorption peaks correspond to the absorption peaks of the structural water hydroxyl-OH stretching vibration in the bentonite; 1640cm–1The absorption peak corresponds to the bending vibration absorption peak of the interlayer absorbed water hydroxyl-OH in the bentonite; 2920cm–1And 2850cm–1The absorption peak is respectively from methyl-H on CMC3And methine-CH2The stretching vibration peaks correspond to each other; 1055cm–1The absorption peak corresponds to the absorption peak of Si-O stretching vibration in bentonite. The infrared spectrum of MB/CP is 1330cm compared with that of RB and MB–1A new absorption peak appears, and the absorption peak corresponds to amide (-CONH)2) Characteristic peaks, presumably due to the-COOH of CMC and-NH of PEI2The amide group formation may occur, which indicates that CMC and PEI have been successfully supported on the surface of MB by graft copolymerization. 584cm–1The absorption peak at (B) corresponds to the absorption peak of Fe-O bond, indicating that Fe3O4Have been successfully loaded on MB and MB/CP. Combining the analysis result of XRD and the analysis result of XPS, the bentonite, organic CMC, PEI and Fe can be proved3O4The four were successfully combined.
BET analysis results are shown in FIGS. 11 to 13
FIGS. 11, 12 and 13 represent N for RB, MB and MB/CP, respectively2Adsorption-desorption isotherms, corresponding panels in fig. 11, 12 and 13 are the pore size distribution plots for RB, MB and MB/CP, respectively. As can be seen from the figure, when 0.44<P/P0<When the temperature is 0.97, the adsorption-desorption isotherms of RB, MB and MB/CP all have a great rising trend; when P/P is present0>At 0.44, H appears on the adsorption-desorption isotherms of the three materials3The hysteresis regression phenomenon of the type hysteresis loop, which occurs, indicates that adsorption confinement does not occur in a region where the relative pressure is high. The adsorption-desorption isotherms of MB and MB/CP belong to a IV-type curve, so that MB and MB/CP are adsorption materials with a hierarchical pore structure, and comprise macropores and mesopores, wherein the macropores can reduce the diffusion resistance of MB/CP to a certain extent, and the mesopores can improve the adsorption performance of MB/CP to pollutants to a certain extent, so that the adsorption capacity of MB/CP to Pb (II) and Cd (II) can be obviously improved after organic modification by CMC and PEI.
Table 1 shows the BET specific surface area, pore size, and void analysis results of RB, MB, and MB/CP, and it is understood from table 1 that MB and MB/CP have an increased specific surface area compared to RB, but have a decreased specific surface area compared to MB/CP, because CMC and PEI are supported only on the surface of bentonite, and are not intercalated between layers, and thus have a slightly decreased specific surface area after organic modification. The pore volume and the average pore diameter of MB/CP are increased compared with those of MB and RB, because various reaction conditions promote the exchange between ions in the process of synthesizing MB/CP by solid-liquid phase, the organic matter of CMC and PEI loaded on the surface of bentonite also improves and increases the pore structure of bentonite, so that mesopores and macropores with adsorption capacity in the bentonite are increased, which is more beneficial to the removal of heavy metals.
TABLE 1 BET specific surface area, pore size and void analysis results of RB, MB and MB/CP
| BET specific surface area/m2·g–1 | Pore volume/cm3·g–1 | Average pore diameter/ | |
| RB | |||
| 70 | 0.15 | 3.9 | |
| MB | 86 | 0.23 | 5.5 |
| MB/CP | 74 | 0.48 | 10.4 |
The results of the VSM analysis are shown in FIG. 14
FIG. 14 shows hysteresis loops of MB and MB/CP under the conditions of magnetic field strength of-30 KOe to 30KOe and temperature of 25 ℃. As can be seen from the curves in the figure, the hysteresis loops of MB and MB/CP are both "S" type curves, and hysteresis phenomena are not generated, which indicates that both MB and MB/CP have good superparamagnetism. The magnetic saturation intensities of MB and MB/CP are significantly different, and the magnetic saturation intensity of MB is 10.12emu g–1Magnetic saturation of MB/CP was 17.87emu g–1Much higher than the magnetic saturation of MB, because of the Fe in MB3O4The magnetic nano-particles are loaded on the surface of RB and are easy to be made of Fe when contacting with air3O4Oxidation to Fe2O3Thus, therefore, it isLeading to a certain reduction of the magnetic properties; organic matters on the composite bentonite MB/CP organically modified by CMC and PEI have certain protection effect on magnetic nuclei, and can effectively prevent Fe3O4So that the MB/CP magnetic saturation is greater.
In addition, the upper left corner and the lower right corner in FIG. 14 are the magnetic separation effects of MB/CP and MB, respectively, under the same applied magnetic field. As can be seen from the magnetic separation experiment, after 12s of magnetic separation time, the MB solution is turbid, a small amount of sample is dispersed in the bottle, and the MB/CP solid-liquid separation is thorough, which also shows that Fe is organically modified by CMC and PEI3O4Closely bound to bentonite, the MB/CP separation ability and magnetic response ability are better.
SEM analysis results are shown in FIGS. 15-17
SEM topographs at multiples of RB, MB and MB/CP10 kv are shown in FIGS. 15, 16 and 17, respectively. As can be seen from the figure, the surface of RB is smooth and uniform, and Fe is loaded3O4The rear MB is rough in surface and many fine particles are present in a layered stack, which is Fe3O4The result of mutual accumulation on the surface of bentonite is that the pore diameter and the specific surface area of MB are increased; the small particles in the MB/CP are piled up into sheets, and the coated condition of the MB/CP is observed, the polymeric lamellar structure is presented, the surface of the MB/CP is much smoother than that of the MB, and the layering is more prominent, because the organic matter CMC and PEI are compounded on the surface of bentonite, and the Fe is coated at the same time3O4And bentonite. The above phenomena all indicate that MB/CP compounding is successful.
Second, adsorption experiment and recycle performance evaluation of Pb (II) and Cd (II) (analysis of organic modified magnetic bentonite MB/CP prepared in example 3)
(I) adsorption experiment for Pb (II) and Cd (II)
1. Influence of adsorption time
The mass concentration of the preparation is 200 mg.L-1500mL of the Pb (II) solution was put in a conical flask with a stopper, and 1.0 g. L of each solution was added-1At a pH of 5 at 25 ℃ in a thermostated water bath oscillator at 150r/min, oscillating and adsorbing for 2h at a rotating speed, taking supernatant at different time intervals within 0-120 min, and measuring the concentration of the supernatant of Pb (II) at a wavelength of 283.3nm by using an atomic absorption spectrophotometer.
At 25 ℃ and pH 5, the reaction temperature was adjusted to 100 mg. multidot.L-1500mL of Cd (II) solution were added with 1.0 g. L each-1And (3) oscillating and adsorbing RB, MB and MB/CP in a constant-temperature water bath oscillator for 2 hours at the condition of 150r/min, sampling at different time intervals of 0-120 min, and then measuring the concentration of the supernatant of Cd (II) at the wavelength of 228.8nm by using an atomic absorption spectrophotometer.
The effect of adsorption time is shown in figures 18 and 19. As can be seen from FIGS. 18 and 19, the adsorption process of Pb (II) and Cd (II) by RB, MB and MB/CP goes through a rapid rise and then gradually reaches the adsorption equilibrium as the adsorption time is prolonged. In the initial stage of adsorption, the surfaces of RB, MB and MB/CP have more adsorption sites which can be utilized, so that the adsorption rate of Pb (II) and Cd (II) is higher, and the state of rapid rise is presented; with the progress of the adsorption process, effective adsorption sites on the surfaces of RB, MB and MB/CP are reduced, and the adsorption rate is reduced, so that the removal rate of Pb (II) and Cd (II) is gradually reduced, and the adsorption tends to be balanced. The adsorption equilibrium time of MB/CP to Pb (II) and Cd (II) is 43min and 37min respectively, and the removal rate of the MB/CP is 99% during adsorption equilibrium; the adsorption equilibrium time of MB to Pb (II) and Cd (II) is 120min, and the removal rates of MB in adsorption equilibrium are 59% and 43% respectively; the adsorption equilibrium time of RB to Pb (II) and Cd (II) is respectively 90min and 58min, and the removal rate in adsorption equilibrium is respectively 69% and 53%. Therefore, the MB/CP has far higher adsorption speed and removal rate to Pb (II) and Cd (II) than MB and RB, because the surface of the MB/CP contains more-OH and-NH after organic modification of organic CMC and PEI2The functional groups can realize the complexing action on Pb (II) and Cd (II). And secondly, the organic modification enlarges the pore volume and the average pore diameter of the MB/CP, and can quickly and effectively adsorb Pb (II) and Cd (II), so that the adsorption capacity of the MB/CP on the Pb (II) and the Cd (II) is better than that of the MB and RB.
2. Influence of initial concentration of solution
Preparing a series of mass concentration ranges from 0 to 1500 mg.L-150mL of Pb (II) solution with different concentration gradients are put into a plurality of 100mL conical flasks, and 1.0 g.L of Pb (II) solution is added-1The RB, MB and MB/CP are subjected to oscillation adsorption for 2 hours in a constant-temperature water bath oscillator at the rotating speed of 150r/min under the conditions of 25 ℃ and the pH value of 5, supernatant liquid is taken after the adsorption equilibrium is reached, and the concentration before and after the adsorption equilibrium of the Pb (II) is measured by an atomic absorption spectrophotometer.
Preparing a series of mass concentrations of 0-1000 mg.L under the conditions of 25 ℃ and pH value of 5-150mL of Cd (II) solution was put in 100mL conical flasks, and 1.0 g. L. was added-1Oscillating and adsorbing the solution for 2 hours in a constant-temperature water bath oscillator at the rotating speed of 150r/min until the solution reaches adsorption equilibrium, taking supernate, and measuring the concentration of Cd (II) before and after the adsorption equilibrium by using atomic absorption spectrophotometer.
The adsorption isotherms of Pb (II) and Cd (II) by RB, MB and MB/CP at different initial concentrations of the solution are shown in FIGS. 20 and 21. As can be seen from the graph, as the initial concentration of the solution increases, the adsorption capacity of MB and MB/CP to Pb (II) and Cd (II) gradually increases. When the initial concentration of Pb (II) and Cd (II) is low, the MB and MB/CP have high adsorption rate on the Pb (II) and Cd (II), and the adsorption capacity is obviously increased; and when the initial concentration of Pb (II) and Cd (II) is gradually increased, the adsorption isotherm is gradually gentle, and finally the adsorption balance is achieved. The reason is that when the initial concentration of Pb (II) and Cd (II) is low, the surfaces of the adsorbing materials MB and MB/CP contain more adsorption sites for Pb (II) and Cd (II) to occupy, so that the adsorption rate of MB and MB/CP to Pb (II) and Cd (II) is high; then when the initial concentration of Pb (II) and Cd (II) reaches high concentration, the adsorption sites of MB and MB/CP are mostly occupied by Pb (II) and Cd (II), and the adsorption saturation is reached, so that the adsorption capacity is not increased any more. As can be seen from the graph, the adsorption capacities of RB, MB and MB/CP for Pb (II) were 107mg g, respectively-1、376mg·g-1And 704mg g-1The adsorption capacity for Cd (II) was 256mg g-1、107mg·g-1And 454 mg. g-1Obviously, the adsorption capacity of MB/CP to Pb (II) and Cd (II) is much higher than that of MB and RB. According to characteristic analysis such as BET, the absorption capacity of MB/CP to Pb (II) and Cd (II) is increased due to the increase of the surface aperture and the complexation between the organic functional groups on the surface and Pb (II) and Cd (II).
Influence of pH value
When the initial pH values of the solutions are different, the adsorption influence experiment of RB, MB and MB/CP on Pb (II) and Cd (II) is that the addition amount of RB, MB and MB/CP is 1.0 g.L at 25 DEG C-1Under the conditions of (1). Preparing a series of 200 mg.L mass concentrations-150mL of Pb (II) solution (2) in a conical flask, with 0.1 mol. L each-1、1.0mol·L-1Adjusting the pH value of the solution to 1-7 by HCl and NaOH, oscillating and adsorbing the solution for 2h in a constant-temperature water bath oscillator at the rotating speed of 150r/min, taking a supernatant after adsorption balance, measuring the concentration of Pb (II) during adsorption balance by atomic absorption spectrophotometry, and measuring the pH values before and after adsorption by the pH meter.
Preparing a series of 100 mg.L mass concentrations in the same way-150mL of Cd (II) solution in an Erlenmeyer flask, using 0.1 mol. L-1、1.0mol·L-1The pH value of the HCl and NaOH adjusting solution is 1-7, and the adding amount of RB, MB and MB/CP is 1.0 g.L-1The solution is oscillated and adsorbed for 2h at the temperature of 25 ℃ and at the speed of 150r/min in a constant-temperature water bath oscillator, supernatant liquid is taken after adsorption equilibrium, the concentration of Cd (II) during adsorption equilibrium is measured by atomic absorption spectrophotometry, and the pH value before and after adsorption is measured by pH.
The effect of the initial pH of the solution is shown in figures 22 and 23. As can be seen from the figure, under the condition that the pH value is 1-7, the process of adsorbing Pb (II) and Cd (II) by RB, MB and MB/CP is obviously changed, and the adsorption change can be roughly divided into three processes: when the pH value is 1-2, the removal rate of Pb (II) by RB, MB and MB/CP is lower than 30%, and the removal rate of Cd (II) is lower than 20%, which may be caused by that under the condition of low pH value, the solution is strongly acidic, and a large amount of H+By making the adsorbent surface-NH2Functional groups such as-OH and the like are protonated and positively charged, so that the adsorbent is electrostatically repelled from Pb (II) and Cd (II), and the removal rate is low; when the pH values are 2-3 and 2-4 respectively, the removal rate of Pb (II) and Cd (II) by MB/CP is highThe amplitude increased from 24% and 4% to 91% and 85%, respectively, probably because the solution H increased with increasing pH+Decrease, decrease of competitive adsorption, — NH on MB/CP surface2Deprotonation of functional groups-OH, Pb (II) and Cd (II) with OH-The reaction is carried out, and after the adsorption action under the strong acid condition, the MB/CP has a certain buffer action on the acid environment, so that the removal rate of the MB/CP on Pb (II) and Cd (II) is greatly increased; when the pH value is 3-7 and 4-7, the removal rate of the MB/CP on Pb (II) is increased from 91% to 99%, then the balance is kept, and the removal rate of the MB/CP on Cd (II) is kept above 85%, and the method is basically stable. When the pH value of the solution is increased from 1 to 7, the equilibrium pH value of Pb (II) and Cd (II) adsorbed by MB/CPeFrom 2.2 and 2.3 to 5.4 and 6.0, respectively. When the pH value of the Pb (II) solution is 3-7, the pH value iseSubstantially above 3; for Cd (II), when the pH value of the solution is 4-7, the pH value of the solution iseBasically, the pH value is above 4, which shows that MB/CP has certain buffering capacity to the initial pH value. As can be seen from the graph, the removal rates of Pb (II) and Cd (II) by MB and MB/CP are the best when the pH value is 5.
Effect of HA coexistence
Preparing a series of Pb (II) with the mass concentration of 200 mg.L-1And the mass concentration of HA is 0-40 mg.L-150mL of the mixed solution (2) was put in a plurality of Erlenmeyer flasks, and 1.0 g. multidot.L of the mixed solution was added to each of the Erlenmeyer flasks-1The RB, MB and MB/CP components are subjected to oscillation adsorption for 2 hours at the rotating speed of 150r/min under the conditions of 25 ℃ and the pH value of 5 until the adsorption equilibrium is reached, and the concentration of Pb (II) after the adsorption equilibrium is measured by an atomic absorption spectrophotometer from the supernatant.
At 25 ℃ pH 5, RB, MB and MB/CP were added in amounts of 1.0 g.L as above-1Under the condition of (2), a series of Cd (II) with the concentration of 100 mg.L is prepared-1HA concentration of 0-40 mg.L-150mL of the mixed solution is put into a plurality of conical flasks, the mixed solution is oscillated and adsorbed for 2 hours at the rotating speed of 150r/min until the adsorption balance is reached, and the concentration of Cd (II) after the adsorption balance is measured by an atomic absorption spectrophotometer for supernatant fluid.
The effect of humic acid HA is shown in FIGS. 24 and 25. From the figure canIt is seen that HA is present at concentrations less than 5 mg.L-1In the process, the compound has a certain promotion effect on the adsorption of Pb (II) by RB and MB, also has a certain promotion effect on the adsorption of Cd (II) by RB, MB and MB/CP, but the promotion effect is not obvious, but has a certain inhibition effect on the adsorption of Pb (II) by MB/CP; as the HA concentration continues to increase, it HAs a certain promoting effect on MB/CP adsorbing Pb (II) because HA contains functional groups of-NH, -OH, etc., and MB/CP also contains-NH2and-OH and the like, and the increase of the functional groups is beneficial to the adsorption of Pb (II) and Cd (II) by MB/CP. Therefore, when the HA concentration is increased, the removal rate of Pb (II) and Cd (II) by MB/CP is improved to a certain extent, but the removal rate can not be increased after the MB/CP reaches the adsorption saturation.
(II) evaluation of Recycling Performance
The mass concentration of the preparation is 200 mg.L-1500mL of the Pb (II) solution was put in a conical flask with a stopper, and 1.0 g. L of each solution was added-1The RB, MB and MB/CP components (B) are subjected to oscillation adsorption for 2 hours in a constant-temperature water bath oscillator at the temperature of 25 ℃ and the pH value of 5 and at the rotating speed of 150r/min, supernatant liquid is taken, and the concentration of the supernatant liquid of Pb (II) is measured at the wavelength of 283.3nm by using an atomic absorption spectrophotometer. And (3) desorbing RB, MB and MB/CP adsorbed with Pb (II) by adopting absolute ethyl alcohol, and repeating the steps for 5 times of cycle experiments.
At 25 ℃ and pH 5, the reaction temperature was adjusted to 100 mg. multidot.L-1500mL of Cd (II) solution were added with 1.0 g. L each-1The RB, MB and MB/CP are subjected to oscillation adsorption for 2 hours in a constant-temperature water bath oscillator at the speed of 150r/min, supernatant liquid is taken, and the concentration of the supernatant liquid of the Cd (II) is measured by an atomic absorption spectrophotometer at the wavelength of 228.8 nm. And (3) desorbing RB, MB and MB/CP after Cd (II) is adsorbed by adopting absolute ethyl alcohol, and repeating the steps to perform 5 times of cycle experiments.
The results of 5 cycles of adsorption of RB, MB and MB/CP on Pb (II) and Cd (II) are shown in FIGS. 26 and 27. As can be seen from the figure, after 5 adsorption-desorption cycle experiments, the removal rates of Pb (II) and Cd (II) by RB are respectively reduced from 57% and 49% to 29% and 31%, the removal rates of Pb (II) and Cd (II) by MB are respectively reduced from 82% and 78% to 62% and 63%, and the removal rates of Pb (II) and Cd (II) by MB/CP are respectively reduced toII) the removal rate is still kept above 90% after 5 cycles. It can be seen that MB/CP is magnetic Fe3O4The loading of the particles and the modification of the CMC and the PEI not only improve the adsorption-desorption performance, but also protect the stability of the magnetic core to a certain extent.
Further, the same characterization was performed on the organically modified magnetic bentonite MB/CP prepared in examples 1-2 and 4-6 as that of the organically modified magnetic bentonite MB/CP prepared in example 3, and the characterization results of the organically modified magnetic bentonite MB/CP prepared in all the examples were highly coincident, indicating that the prepared product was excellent in reproducibility.
From the above analysis, one can obtain:
performing structural determination on the organic modified magnetic bentonite MB/CP prepared by the method, wherein the organic modified magnetic bentonite MB/CP takes natural calcium bentonite as a carrier and is loaded with magnetic nano Fe3O4Particles and a quaternary composite material with the surface modified by organic modifiers of sodium carboxymethyl cellulose and polyethyleneimine, and the structure of the quaternary composite material is shown in figure 3; in FIG. 3, the interlayer is natural calcium bentonite, and the substance in the square frame is single-grain magnetic Fe3O4Structural unit of particles, single grain magnetic Fe3O4The particle building block is shown in figure 4.
The physical and chemical properties of the organic modified magnetic bentonite MB/CP are detected, the interlayer spacing of the organic modified magnetic bentonite MB/CP is 1.30-1.77 nm, and the BET specific surface area is 70-86 m2·g-1The pore volume is 0.48-0.64cm3·g-1Average pore diameter of 10.4-12.5nm and saturation magnetization value of 17.87-19.23emu g-1Under the action of an external magnetic field, the solid-liquid separation and recovery of 10-12s can be realized.
Claims (10)
1. An organic modified magnetic bentonite MB/CP is characterized in that: the organic modified magnetic bentonite MB/CP takes natural calcium bentonite as a carrier and is loaded with magnetic nano Fe3O4Particles and surface-modified with organic modifiers sodium carboxymethylcellulose and polyethyleneimineThe structure of the quaternary composite material is shown in FIG. 3; in FIG. 3, the interlayer is natural calcium bentonite, and the substance in the square frame is single-grain magnetic Fe3O4Structural unit of particles, single grain magnetic Fe3O4The particle building block is shown in figure 4.
2. The organo-modified magnetic bentonite MB/CP as claimed in claim 1, wherein: the interlayer spacing of the organic modified magnetic bentonite MB/CP is 1.30-1.77 nm, and the BET specific surface area is 70-86 m2·g-1The pore volume is 0.48-0.64cm3·g-1Average pore diameter of 10.4-12.5nm and saturation magnetization value of 17.87-19.23emu g-1Under the action of an external magnetic field, the solid-liquid separation and recovery of 10-12s can be realized.
3. A method for preparing organically modified magnetic bentonite MB/CP as claimed in claim 1 or 2, characterized in that: the method adopts a microwave coprecipitation method to prepare magnetic nano Fe3O4Loading the particles on natural calcium bentonite to obtain magnetic calcium bentonite, and performing surface modification on the magnetic calcium bentonite by using a graft copolymer formed by reaction of sodium carboxymethylcellulose and polyethyleneimine as an organic modifier to obtain the organically modified magnetic bentonite MB/CP.
4. The method for preparing the organically modified magnetic bentonite MB/CP as claimed in claim 3, wherein the method comprises the following steps: the method specifically comprises the following steps:
(1)Fe3O4preparing magnetic fluid: FeCl is added2·4H2O and FeCl3·6H2Placing the dissolved O in a microwave solid-liquid synthesizer for microwave heating reaction for 0.5-2 h, cooling to room temperature after the reaction is stopped, and obtaining Fe3O4A magnetic fluid;
(2) preparation of organic modifier: respectively dissolving sodium carboxymethylcellulose and polyethyleneimine in water, and stirring until the solution is uniform to obtain a sodium carboxymethylcellulose solution and a polyethyleneimine solution;
(3) preparing organic modified magnetic bentonite MB/CP: adding sodium carboxymethylcellulose solution into Fe3O4And (3) placing the magnetic fluid in a microwave solid-liquid synthesizer for reaction for 0.5-1 h, then adding a polyethyleneimine solution for continuous reaction for 0.5-1 h, then adding natural calcium bentonite for continuous reaction for 0.5-1 h, cooling to room temperature after the reaction is finished, washing and drying to obtain the organic modified magnetic bentonite MB/CP.
5. The method for preparing the organically modified magnetic bentonite MB/CP according to claim 4, wherein the method comprises the following steps: in step (1), FeCl2·4H2O and FeCl3·6H2The mass ratio of O is 1: 1.5-2.2, and the setting parameters and reaction conditions of the microwave solid-liquid synthesizer are as follows: at 50-60 ℃, 500-600W, mixing the phases (0), and stirring at a speed of 200-600 rpm; the reaction process is as follows: carrying out reaction for 2-10 min in a microwave preheating stage, adding an alkaline solution to adjust the pH value of a reaction system to 7-13, then carrying out reaction for 0.5-1 h, ageing for 0.3-1 h after the reaction is finished, and cooling to room temperature; the alkaline solution is any one of ammonia water, sodium hydroxide and potassium hydroxide.
6. The method for preparing the organically modified magnetic bentonite MB/CP according to claim 4, wherein the method comprises the following steps: in the step (2), the mass concentration of the sodium carboxymethyl cellulose solution and the polyethyleneimine solution is 0.1-10%, before use, the sodium carboxymethyl cellulose solution is diluted by 2-4 times with water, and the polyethyleneimine solution is diluted by 1-3 times.
7. The method for preparing the organically modified magnetic bentonite MB/CP according to claim 4, wherein the method comprises the following steps: in the step (3), the mass ratio of the added sodium carboxymethylcellulose to the added polyethyleneimine is 0.3-1.2: 1.
8. The method for preparing the organically modified magnetic bentonite MB/CP as claimed in claim 7, wherein: in step (3), Fe3O4The amount of substance (a) and the amount of carboxymethyl cellulose addedThe ratio of the sum of the amounts of sodium, polyethyleneimine and natural calcium bentonite is 2.5-17.5: 100.
9. The method for preparing the organically modified magnetic bentonite MB/CP according to claim 4, wherein the method comprises the following steps: in the step (3), the setting parameters and reaction conditions of the microwave solid-liquid synthesizer are as follows: 50-60 ℃, 500-600W, mixed phase (0), and stirring speed of 200-600 rpm.
10. The application of the organic modified magnetic bentonite MB/CP obtained by the preparation method of any one of claims 3 to 9 is characterized in that: used for adsorbing heavy metal ions Pb (II) and Cd (II).
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