CN109304470B - Surface-modified amorphous zero-valent iron, and preparation method and application thereof - Google Patents
Surface-modified amorphous zero-valent iron, and preparation method and application thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of organic wastewater treatment by an advanced oxidation method, and particularly relates to surface-modified amorphous zero-valent iron, a preparation method thereof and an efficient treatment technology applied to organic wastewater.
Description
Technical Field
The invention belongs to the technical field of organic wastewater treatment by an advanced oxidation method, and particularly relates to surface-modified amorphous zero-valent iron, a preparation method thereof and an efficient treatment technology applied to organic wastewater.
Background
Zero-valent iron is unique in chemical property and physical property, and is an indispensable ring in the fields of groundwater remediation, soil remediation and the like. The zero-valent iron particles have strong reducibility, can effectively treat various pollutants such as halogenated organic matters, heavy metals, azo dyes, acid radical ions and the like in water, and are one of main materials for applying the permeable reactive wall technology to groundwater remediation. However, the current practice of zero-valent iron repair technology still faces great difficulty, mainly due to the defects of easy oxidation and easy agglomeration of iron, and the like, the effective contact area of zero-valent iron and pollutants is reduced, and the activity of zero-valent iron is reduced. In order to solve the problem of application of zero-valent iron to practical engineering, researchers in the field modify and modify zero-valent iron by various methods in recent years, and the modification mainly comprises technical modification of bimetal, surface modified zero-valent iron, load-type zero-valent iron and the like.
The invention patent with publication number CN 102614918A discloses that a chemical reduction method is used for preparing nano zero-valent iron particles modified by a dispersant, so that the stable dispersion of the nano particles is ensured, and the degradation efficiency of the material on chlorinated organic compounds in water is improved. The method uses potassium borohydride solution to prepare zero-valent iron, and the economy of the method is reduced because the cost of potassium borohydride is extremely high and a byproduct boron hydroxide is generated in the reaction process.
The invention patent with the patent application number of CN 200810207760.4 prepares the polyelectrolyte fibrofelt loaded zero-valent iron material through an electrostatic spinning method, ensures the dispersibility of the zero-valent iron, is beneficial to recovery and reduces secondary pollution. Sodium borohydride is also used in the process, which results in higher preparation cost.
The two patents of the invention both use borohydride, so that the preparation cost of the zero-valent iron is higher.
According to the literature (Shen W, Mu Y, Wang B, et al. enhanced atmospheric diffraction of4-chlorophenol with ionic nanoparticles applied Surface Science,2017,393: 316-.
Disclosure of Invention
Aiming at the defects or improvement requirements of the prior art, the invention provides modified amorphous zero-valent iron, a preparation method and application thereof, aiming at preparing the surface modified amorphous zero-valent iron by combining a melting melt-spinning method and a high-energy ball milling method and introducing polyelectrolyte into a ball milling system, wherein the surface of the amorphous zero-valent iron has more coordination unsaturated points, so that the chemical performance of the material is improved; the dispersibility of the amorphous iron powder is improved through surface modification, and the combination of the amorphous iron powder and the surface modification not only ensures that the amorphous iron powder has better chemical catalytic activity when organic wastewater is treated in an advanced oxidation system, but also improves the dispersibility and the migration capacity of the amorphous zero-valent iron in a water body, and improves the degradation effect of the amorphous zero-valent iron on organic wastewater pollutants, thereby solving the technical problems of easy agglomeration, low chemical activity, high cost and the like when the zero-valent iron material in the prior art is used for treating wastewater through advanced oxidation.
To achieve the above objects, according to one aspect of the present invention, there is provided a method for preparing surface-modified amorphous zero-valent iron, comprising the steps of:
(1) preparing a non-metal-containing iron-based amorphous strip with the width of 2-5 mm and the thickness of 0.01-0.1 mm by using a melting melt spinning method;
(2) carrying out primary ball milling crushing on the iron-based amorphous strip obtained in the step (1) in an inert atmosphere, wherein the diameter of a ball adopted in the ball milling process is 4-6 mm, the mass ratio of the ball to the iron-based amorphous strip is 10-35: 1, and adding a solvent in the ball milling process to obtain primary amorphous zero-valent iron powder;
(3) and (3) carrying out secondary ball milling on the primary amorphous zero-valent iron powder obtained in the step (2) in an inert atmosphere, and adding polyelectrolyte in the ball milling process, wherein the diameter of a ball adopted in the ball milling process is 0.5-1.5 mm, and the mass ratio of the mass of the ball to the mass of the primary amorphous zero-valent iron powder is 18.2-66.7: 1, so as to obtain the surface-modified amorphous zero-valent iron with the particle size of 200-250 nm.
Preferably, the melt spinning speed of the melt spinning method in the step (1) is 10-20 m/min.
Preferably, the nonmetal elements in the step (1) comprise silicon and boron, and preferably, the atomic ratio of iron element, silicon element and boron element in the iron-based amorphous strip is 1: 0.1-0.2; preferably 79:10: 11.
Preferably, the ball milling speed in the step (2) is 800-1000 r/min, and the ball milling time is 90-300 min.
Preferably, the polyelectrolyte in step (3) is a water-soluble polyelectrolyte including one or more of polyacrylic acid, polyacrylamide, polyvinylamine, and carboxymethyl cellulose.
Preferably, the added mass of the polyelectrolyte accounts for 15-25% of the mass of the primary amorphous zero-valent iron powder in the step (3).
Preferably, the ball milling speed in the step (3) is 800-1000 r/min, and the ball milling time is 90-300 min.
Preferably, the solvent in the step (3) is isopropanol or ethanol, and 3.6-10 m L of the solvent is added per gram of the primary amorphous zero-valent iron powder.
Preferably, the inert atmosphere is nitrogen or argon.
According to another aspect of the present invention, there is provided a surface-modified amorphous zero-valent iron prepared according to the preparation method as described above.
According to another aspect of the invention, the application of the surface modified amorphous zero-valent iron is provided, and the surface modified amorphous zero-valent iron is applied to an advanced oxidation technology for treating organic polluted wastewater, preferably, the iron powder and hydrogen peroxide are applied to the advanced oxidation technology for cooperatively treating the polluted wastewater.
In general, the above technical solutions contemplated by the present invention can achieve the following advantageous effects compared to the prior art.
1. In the traditional method, sodium borohydride is used for reducing (ferrous) ions, the cost is high, and the prepared iron powder is easy to oxidize and agglomerate; the method comprises the steps of firstly preparing an iron-based amorphous strip by a melting melt-spinning method, then performing high-energy ball milling twice, and adding polyelectrolyte into the ball milling for the second time, so that the surface of the prepared amorphous zero-valent iron is attached with polyelectrolyte ionized groups with charges, and the obtained surface-modified amorphous zero-valent iron has good chemical activity, has great advantages in oxidation resistance and dispersibility, is simple and easy to obtain raw materials, and has low cost;
2. the dispersed amorphous zero-valent iron prepared by the invention has an amorphous structure, has no obvious ordering rule, has more coordination unsaturated points on the surface, and improves the chemical property and the catalytic property of the material;
3. the dispersed amorphous zero-valent iron prepared by the method has a rough surface, improves the adsorption capacity of the material, is beneficial to generating adsorption-catalytic degradation-adsorption effects, enhances the mass transfer phenomenon in the solution and improves the catalytic effect of the material;
4. after polyelectrolyte is introduced into a ball milling system, the dispersibility of the amorphous zero-valent iron material is greatly improved;
5. the method combines a melting melt-spinning method with a two-stage high-energy ball milling method, carefully selects and sets appropriate process parameters including the melt-spinning speed, the diameter and weight of balls respectively adopted by the two-stage ball milling, the time and the rotating speed of ball milling, the amount of a dispersing agent added during secondary ball milling and the like, reasonably controls the width and the thickness of an iron-based amorphous strip prepared by the melting melt-spinning method and the particle size of primary amorphous iron powder obtained by primary ball milling, and finally obtains the dispersive amorphous zero-valent iron with a certain particle size range through the mutual synergistic cooperation of the parameters;
6. the polyelectrolyte is introduced into the preparation method of the amorphous zero-valent iron, so that the ionized charged groups of the polyelectrolyte are attached to the surface of the prepared amorphous zero-valent iron, and the polyelectrolyte plays a role of a dispersing agent on one hand, and on the other hand, when the amorphous zero-valent iron is applied to wastewater pollutant degradation, especially to the wastewater pollutant degradation by the Fenton method or the Fenton-like method, the polyelectrolyte can also be used as a Fenton reaction promoter, and the negatively charged groups ionized by the polyelectrolyte are coordinated and combined with ferric ions, so that the conversion from ferric ions to ferrous ions is facilitated, the Fenton degradation reaction is promoted, and the wastewater pollutant degradation efficiency and the degradation effect are obviously improved.
Drawings
FIG. 1 is a schematic view of a process for preparing modified amorphous zero-valent iron according to the present invention;
FIG. 2 is a comparison of XRD patterns of modified amorphous zero valent iron prepared in example 1 of the present invention and commercial reduced iron powder;
FIG. 3 is an atomic force microscope image of modified amorphous zero valent iron prepared in example 1 of the present invention;
FIG. 4 is a comparison of the dispersing effect of the modified amorphous zero-valent iron prepared in example 1 of the present invention and the ordinary amorphous zero-valent iron prepared in comparative example 1 without adding a dispersant;
FIG. 5 is a graph comparing the degradation of p-chlorophenol by modified amorphous zero-valent iron prepared in example 1 of the present invention, by ordinary amorphous zero-valent iron prepared in comparative example 1, and by crystalline zero-valent iron prepared in comparative example 2;
FIG. 6 is a graph showing the effect of modified amorphous zero-valent iron prepared in example 1 of the present invention on the degradation of methylene blue.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention provides a preparation method of modified amorphous iron powder, which comprises the following steps:
(1) preparing an iron-based amorphous strip: preparing a non-metal-containing iron-based amorphous strip with the width of 2-5 mm and the thickness of 0.01-0.1 mm by using a melting melt spinning method; the melt spinning speed of the melt spinning method is preferably 10-20 m/min; the nonmetal elements can comprise silicon and boron, and preferably, the atomic ratio of the iron element, the silicon element and the boron element in the iron-based amorphous strip is 1: 0.1-0.2, and preferably 79:10: 11.
(2) Primary crushing: carrying out primary ball milling crushing on the iron-based amorphous strips obtained in the step (1) in an inert atmosphere, wherein the diameter of balls adopted in the ball milling process is 4-6 mm, the mass ratio of the balls to the iron-based amorphous strips is 10-35: 1, and adding a solvent in the ball milling process to obtain primary amorphous zero-valent iron powder; the ball-to-material ratio is an important condition for ball milling, the ball-to-material ratio is insufficient for ball milling or needs a long time for ball milling, and the yield of over ball milling has an influence.
The solvent is isopropanol or ethanol, the addition amount of the solvent is 2-6 m L, the solvent can avoid continuous high temperature in the ball milling process, so that the dispersing agent and iron powder can be fully and uniformly mixed, the grinding aid can also serve as a grinding aid, the ball milling effect is more sufficient, the particle size of powder is smaller, the ball milling speed is 800-1000 r/min, the ball milling time is 90-300 min, and the inert atmosphere is nitrogen or argon.
(3) Secondary ball milling: and (3) carrying out secondary ball milling on the primary amorphous zero-valent iron powder obtained in the step (2) in an inert atmosphere, and adding polyelectrolyte in the ball milling process, wherein the diameter of balls adopted in the ball milling process is 0.5-1.5 mm, and the mass ratio of the balls to the primary amorphous zero-valent iron powder is 18.2-66.7: 1, so that the amorphous iron powder with the particle size of 200-250 nm is obtained.
The ball milling speed is 800-1000 r/min, the ball milling time is 90-300 min, the solvent is isopropanol or ethanol, 3.6-10 m L of solvent is added into each gram of primary amorphous zero-valent iron powder, the solvent is guaranteed to slightly soak the powder and stainless steel pellets in the experimental process, the obtained volume ensures that all advantages of the solvent can be achieved, the inert atmosphere is nitrogen or argon, the polyelectrolyte is water-soluble polyelectrolyte, preferably one or more of polyacrylic acid, polyacrylamide, polyvinylamine and carboxymethyl cellulose, the polyelectrolyte is water-soluble polyelectrolyte, after the polyelectrolyte is added, groups with charges can be ionized with water, the ionizable groups are attached to the surface of the amorphous iron powder, so that the whole powder particles have the same charges, the iron powder particles are dispersed, the adding amount of the polyelectrolyte directly influences the dispersibility and chemical activity of the prepared amorphous iron powder, the adding amount of the amorphous polyelectrolyte accounts for 15-25% of the mass of the primary zero-valent iron powder, the adding amount of the amorphous polyelectrolyte can ensure that the prepared amorphous zero-valent iron powder has good dispersibility and no agglomeration, the amorphous iron powder and the amorphous pollutants and the amorphous iron powder prepared by the adding amount of the amorphous iron powder directly influences the dispersibility and the chemical activity, and the adding of the amorphous iron powder, so that the amorphous iron powder has good dispersibility and the chemical activity of the added amorphous iron powder.
The dispersed amorphous iron powder prepared by the preparation method is applied to the advanced oxidation technology for efficiently treating organic polluted wastewater, particularly the iron powder and hydrogen peroxide are applied to the cooperative treatment of the polluted wastewater, and a good pollutant degradation effect is obtained. According to the invention, polyelectrolyte is added in the preparation process of amorphous iron powder, so that on one hand, the agglomeration of amorphous iron powder can be relieved or avoided, and the reaction activity is improved; on the other hand, polyelectrolyte is attached to the surface of the amorphous iron powder prepared by the method, so that a loose and discontinuous granular iron oxide is formed on the surface of the iron powder instead of a compact iron oxide film, and thus when the amorphous iron powder is used for treating organic polluted wastewater, the loose and discontinuous granular iron oxide on the surface of the iron powder is easily dissolved out to promote a Fenton degradation reaction; furthermore, the ionizable groups in the polyelectrolyte are bound with Fe3+Combined to form a complex, which in this complex form promotes Fe in Fenton's reaction3+To Fe2+The conversion of the amorphous iron powder further promotes the Fenton degradation reaction and improves the pollution degradation efficiency, so the polyelectrolyte added in the preparation method of the amorphous iron powder simultaneously plays three roles of dispersing agent, iron oxide dissolution promotion and Fenton reaction promotion.
The amorphous material has irregular atom sequence inside, unsaturated electron arrangement of atoms and many coordination unsaturated points on the surface, so that the chemical energy is higher, the adsorption of the material can be promoted, and the adsorption of the material is reducedThe surface chemical energy is that amorphous zero-valent iron powder with the particle size range of 200-250 nm is prepared by a melting melt-spinning method and two-stage ball milling, and more coordination unsaturated points on the surface of the amorphous iron powder can promote the catalytic performance of the iron powder, thereby being beneficial to the generation and the implementation of Fenton reaction. However, the particle size of the amorphous iron powder prepared by the conventional amorphous iron powder preparation method is not as fine as that of the crystalline phase nano iron powder prepared by the conventional liquid phase method, so from this angle, the chemical activity of the amorphous iron powder is generally considered to be not as high as that of the crystalline phase nano iron powder with a finer particle size, but on the other hand, the crystalline phase iron powder with a finer particle size, such as the nano crystalline phase iron powder, is easy to agglomerate and affect the chemical activity. The invention creatively prepares the amorphous iron powder by a melting melt-spinning method and a two-stage ball milling technology and introduces water-soluble polyelectrolyte in the preparation process of the amorphous iron powder, so that ionized groups with the same charge obtained by ionizing the polyelectrolyte are attached to the surface of the prepared amorphous iron powder, the dispersibility of the particles of the amorphous iron powder is good due to the repulsion of the same charge, and the chemical activity of the particles is increased; on the other hand, the existence of polyelectrolyte enhances the oxidation resistance of the amorphous iron powder, the surface of the amorphous iron powder is not easily oxidized to form a compact iron oxide film in an oxygen-containing environment, but loose or discontinuous iron oxide particles, so that the iron oxide is easily dissolved out when the amorphous iron powder is applied to advanced oxidation technology sewage treatment, and the Fenton reaction is promoted, and the chemical activity of the amorphous iron powder is improved in this respect; further, as described above, the ionizable group and Fe in the surface polyelectrolyte3+Combined to form a complex, which in this complex form promotes Fe in Fenton's reaction3+To Fe2+The Fenton degradation reaction is further promoted, the pollution degradation efficiency is improved, and the chemical activity of the amorphous iron powder is further improved. Therefore, the polyelectrolyte is skillfully added in the melting and strip throwing method, the two-stage ball milling method and the ball milling process, and although the prepared crystalline phase iron powder (10-50 nm) has the particle size (200-250 nm) larger than that of the crystalline phase iron powder prepared by the traditional liquid phase method, the dispersion type, the oxidation resistance and the chemical activity of the amorphous iron powder are obviously improved by carrying out surface modification on the amorphous iron powder in the preparation process.
The following are examples:
example 1
(1) According to the atomic ratio of Fe: si: weighing three simple substances of Fe, Si and B respectively at a ratio of 79:10:11, melting in a WK-IID type vacuum arc amorphous material preparation furnace, and preparing into an iron-based amorphous strip at a linear speed of 11.4m/min on a WK-II vacuum strip throwing machine; the strip is about 2mm wide and about 0.1mm thick.
(2) Weighing 2.0g of the amorphous strip, selecting 30g of 5mm small balls, weighing 5m of isopropanol L, ball-milling for 300min at a ball-milling speed of 1000r/min under the condition of nitrogen, separating, and drying in vacuum to obtain the primary amorphous zero-valent iron powder.
(3) Weighing 0.8g of the primary amorphous zero-valent iron powder, selecting 30g of small balls with the diameter of 1mm and 0.2g of polyacrylic acid, weighing 5m L of isopropanol, carrying out ball milling for 300min at the ball milling speed of 1000r/min under the condition of nitrogen, separating, and carrying out vacuum drying to obtain the fine modified amorphous iron powder.
FIG. 1 is a schematic view of a process for preparing amorphous iron powder according to this embodiment; fig. 2 is a comparison of XRD patterns of the amorphous iron powder prepared in example 1 and the commercial reduced iron powder, and it can be seen that the commercial reduced iron powder has distinct diffraction peaks at 44.9 ° and 65.0 °, while the amorphous iron powder prepared in this example has no distinct diffraction peaks, indicating that its atomic arrangement structure is disordered, the lattice structure is not distinct, and it is a typical amorphous structure.
Fig. 3 is an atomic force microscope picture of the amorphous iron powder prepared in example 1, which shows that the particle size is about 200 to 250nm, and the surface has a plurality of nano-scale protrusions and is rough.
Comparative example 1
According to the atomic ratio of Fe: si: weighing three simple substances of Fe, Si and B respectively at a ratio of 79:10:11, melting in a WK-II D type vacuum arc amorphous material preparation furnace, and preparing into an iron-based amorphous strip at a linear speed of 11.4m/min on a WK-II vacuum strip throwing machine; the strip is about 2mm wide and about 0.1mm thick.
(2) Weighing 2.0g of the amorphous strip, selecting 30g of 5mm small balls, weighing 5m of isopropanol L, ball-milling for 300min at a ball-milling speed of 1000r/min under the condition of nitrogen, separating, and drying in vacuum to obtain the primary amorphous zero-valent iron powder.
(3) Weighing 1.0g of the primary amorphous zero-valent iron powder, selecting 30g of 1mm small balls, weighing 5m of isopropanol L, ball-milling for 300min at a ball-milling speed of 1000r/min under the condition of nitrogen, separating, and drying in vacuum to obtain the fine common amorphous zero-valent iron powder.
Fig. 4 is a comparative test of dispersibility of the amorphous zero-valent iron powder samples prepared in comparative example 1 (left side) and example 1 (right side), and it can be seen that the dispersion type sample suspensions to which polyacrylic acid was added as a dispersant have uniform color and the dispersibility is significantly superior to the ordinary dispersed iron powder of comparative example 1.
Example 2
The amorphous iron powder is prepared by the following method:
(1) according to the atomic ratio of Fe: si: weighing three simple substances of Fe, Si and B respectively at a ratio of 79:10:11, melting in a WK-IID type vacuum arc amorphous material preparation furnace, and preparing into an iron-based amorphous strip at a linear speed of 11.4m/min on a WK-II vacuum strip throwing machine; the strip is about 2mm wide and about 0.1mm thick.
(2) Weighing 2.0g of the amorphous strip, selecting 20g of 5mm small balls, weighing 3m of isopropanol L, ball-milling for 90min at a ball-milling speed of 1000r/min under the condition of nitrogen, separating, and drying in vacuum to obtain the primary amorphous zero-valent iron powder.
(3) Weighing 0.85g of the primary amorphous zero-valent iron powder, selecting 50g of 1mm small balls and 0.15g of polyacrylic acid, weighing 6.5m L of isopropanol, ball-milling for 300min at the ball-milling speed of 1000r/min under the condition of nitrogen, separating, and drying in vacuum to obtain the fine amorphous iron powder.
Example 3
The amorphous iron powder is prepared by the following method:
(1) according to the atomic ratio of Fe: si: weighing three simple substances of Fe, Si and B respectively at a ratio of 79:10:11, melting in a WK-IID type vacuum arc amorphous material preparation furnace, and preparing into an iron-based amorphous strip at a linear speed of 3.8m/min on a WK-II vacuum strip throwing machine; the strip is about 2mm wide and about 0.1mm thick.
(2) Weighing 2.0g of the amorphous strip, selecting 10g of 5mm small balls, weighing 2m of isopropanol L, ball-milling at a ball-milling speed of 800r/min for 300min under the condition of nitrogen, separating, and drying in vacuum to obtain the primary amorphous zero-valent iron powder.
(3) Weighing 0.75g of the primary amorphous zero-valent iron powder, selecting 20g of 1mm small balls and 0.25g of polyacrylic acid, weighing 3.6m L of isopropanol, ball-milling for 300min at the ball-milling speed of 1000r/min under the condition of nitrogen, separating, and drying in vacuum to obtain the fine dispersed amorphous iron powder.
Comparative example 2
Preparing the crystal form zero-valent iron by using a traditional liquid phase reduction method, namely preparing FeCl with the concentration of 0.3M and the concentration of 100M L3Solution and 100M L NaBH of 1.5M concentration4Solution of NaBH in nitrogen at room temperature4FeCl is slowly dropped into the solution3In the solution, the color of the solution is changed from brown to black green until the solution finally becomes black particles, and then the solution is centrifugally cleaned for 3 times and dried in vacuum to obtain the zero-valent iron prepared by the liquid phase method, wherein the particle size range of the zero-valent iron is 10-50 nm.
Compared with the zero-valent iron prepared by the traditional sodium borohydride reduction method in the comparative example, the amorphous iron powder prepared by the invention has great advantages in oxidation resistance. Specifically, the zero-valent iron prepared by the liquid phase method in the comparative example shows a darker iron oxide color after being contacted with air for 24 hours, namely, the surface of the iron powder turns from black to yellow, but the zero-valent iron prepared by the embodiment 1 of the invention has no obvious color change.
The following examples demonstrate the effect of the surface-modified amorphous zero-valent iron prepared by the method of the present invention in the removal of organic contaminants:
example 4
0.02g of the modified amorphous zero-valent iron prepared in example 1, 0.02g of the ordinary amorphous zero-valent iron prepared in comparative example 1 and 0.02g of the crystalline zero-valent iron prepared in comparative example 2 and having a particle size range of 10-50 nm are weighed and added into three portions of 50m L p-chlorophenol solution (initial concentration of 100 mg/L and initial pH of 2.3) respectively, and 15 mu L H is added2O2Solution (30 wt%). Samples were taken at intervals after mixing, and the content of p-chlorophenol in water was measured by high performance liquid chromatography, and the comparison is shown in FIG. 5.
As can be seen from FIG. 5, the degradation effect of the modified amorphous iron powder introduced with polyacrylic acid is obvious, and p-chlorophenol in water can be basically removed within 10 min; and because of the introduction of polyacrylic acid, the dispersibility of the iron powder is greatly improved, and iron oxide is separated out in the degradation process, so that the degradation effect is obviously better than that of the ordinary amorphous zero-valent iron without the introduction of polyacrylic acid, and the modified amorphous iron powder prepared in example 1 has a good purification effect on phenol wastewater. Meanwhile, the amorphous zero-valent crystalline phase iron powder prepared by the traditional liquid phase method is slightly superior to zero-valent crystalline phase iron powder prepared by the traditional liquid phase method, so that the amorphous zero-valent iron powder prepared by the invention not only has greatly improved oxidation resistance and dispersibility, but also still keeps good chemical activity, and the preparation cost of the zero-valent iron is reduced compared with that of the traditional preparation method. In addition, the grain diameter of the zero-valent crystalline phase iron powder prepared by the traditional liquid phase method is very fine, which is about 50 nanometers, and the grain diameter is independently seen, the chemical activity of the amorphous iron powder is far higher than that of the amorphous iron powder with the particle size of about 200-250 nm prepared in the embodiment 1 of the invention in theory, the degradation effect on the parachlorophenol is also reasonably much higher than that of the amorphous iron powder with the particle size range prepared in the embodiment 1 of the invention, in fact, as can be seen from the test effect, the invention improves the surface quality of the amorphous iron powder, polyelectrolyte is introduced on the surface of the prepared amorphous iron powder, and the polyelectrolyte has combined action in three aspects of dispersibility, oxidation resistance and Fenton reaction promotion, therefore, the chemical activity and the Fenton degradation efficiency of the amorphous iron powder are greatly improved, namely, the requirement on the granularity of the iron powder is greatly reduced by adopting polyelectrolyte to carry out surface modification on the amorphous iron powder.
Example 5
0.02g of the modified amorphous iron powder prepared in example 1 was weighed into a 50m L methylene blue solution (initial concentration 20 mg/L, initial pH 3) and 15. mu. L H was added2O2Solution (30 wt%). Samples were taken at intervals after mixing and the results of the color change of the samples are shown in FIG. 6. It can be seen from fig. 6 that the color of the methylene blue solution obviously shows a gradually decreasing rule, which indicates that the modified amorphous iron powder prepared in example 1 has a good decoloring effect on non-azo dye wastewater.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (11)
1. A preparation method of surface modified amorphous zero-valent iron is characterized by comprising the following steps:
(1) preparing a non-metal-containing iron-based amorphous strip with the width of 2-5 mm and the thickness of 0.01-0.1 mm by using a melting melt spinning method;
(2) carrying out primary ball milling crushing on the iron-based amorphous strip obtained in the step (1) in an inert atmosphere, wherein the diameter of a ball adopted in the ball milling process is 4-6 mm, the mass ratio of the ball to the iron-based amorphous strip is 10-35: 1, and adding a solvent in the ball milling process to obtain primary amorphous zero-valent iron powder;
(3) performing secondary ball milling on the primary amorphous zero-valent iron powder obtained in the step (2) in an inert atmosphere, and adding polyelectrolyte in the ball milling process, wherein the diameter of a ball adopted in the ball milling process is 0.5-1.5 mm, and the mass ratio of the ball to the primary amorphous zero-valent iron powder is 18.2-66.7: 1, so as to obtain surface-modified amorphous zero-valent iron with the particle size of 200-250 nm;
the polyelectrolyte is water-soluble polyelectrolyte, and after the polyelectrolyte is added in the ball milling process, the polyelectrolyte can be ionized into groups with charges when meeting water, and the ionizable groups are attached to the surface of the amorphous iron powder, so that the whole powder particles have the same charges, and the dispersibility of the amorphous iron powder is improved.
2. The method according to claim 1, wherein the melt spinning method of step (1) has a spinning speed of 10 to 20 m/min.
3. The preparation method according to claim 1, wherein the nonmetal elements in the step (1) include silicon and boron, and an atomic ratio of iron element, silicon element and boron element in the iron-based amorphous ribbon is 1: 0.1-0.2.
4. The preparation method of claim 1, wherein the ball milling speed in the step (2) is 800-1000 r/min, and the ball milling time is 90-300 min.
5. The method according to claim 1, wherein the polyelectrolyte in the step (3) is a water-soluble polyelectrolyte including one or more of polyacrylic acid, polyacrylamide, polyvinylamine, and carboxymethylcellulose.
6. The preparation method of claim 1, wherein the polyelectrolyte is added in the step (3) in an amount of 15-25% by mass based on the mass of the primary amorphous zero-valent iron powder.
7. The preparation method of claim 1, wherein the ball milling speed in the step (3) is 800-1000 r/min, and the ball milling time is 90-300 min.
8. The preparation method according to claim 1, wherein the solvent in the step (3) is isopropanol or ethanol, and 3.6-10 m L of the solvent is added per gram of the primary amorphous zero-valent iron powder.
9. A surface-modified amorphous zero-valent iron prepared by the preparation method according to any one of claims 1 to 8.
10. Use of the surface-modified amorphous zero-valent iron of claim 9 in advanced oxidation technology for the treatment of organically contaminated wastewater.
11. The use of claim 10, wherein iron powder and hydrogen peroxide are used in conjunction to treat contaminated wastewater in advanced oxidation technologies.
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