CN117772126A - Modified ferrihydrite and preparation method and application thereof - Google Patents
Modified ferrihydrite and preparation method and application thereof Download PDFInfo
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- CN117772126A CN117772126A CN202410024139.3A CN202410024139A CN117772126A CN 117772126 A CN117772126 A CN 117772126A CN 202410024139 A CN202410024139 A CN 202410024139A CN 117772126 A CN117772126 A CN 117772126A
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- 238000001179 sorption measurement Methods 0.000 claims abstract description 70
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- 239000002131 composite material Substances 0.000 claims 1
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- WLZRMCYVCSSEQC-UHFFFAOYSA-N cadmium(2+) Chemical compound [Cd+2] WLZRMCYVCSSEQC-UHFFFAOYSA-N 0.000 abstract description 43
- 239000011148 porous material Substances 0.000 abstract description 29
- 150000002500 ions Chemical class 0.000 abstract description 9
- 229910021645 metal ion Inorganic materials 0.000 abstract description 3
- 239000002244 precipitate Substances 0.000 abstract description 2
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 18
- 230000000052 comparative effect Effects 0.000 description 15
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 7
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- 229910002651 NO3 Inorganic materials 0.000 description 3
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
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- AEIXRCIKZIZYPM-UHFFFAOYSA-M hydroxy(oxo)iron Chemical compound [O][Fe]O AEIXRCIKZIZYPM-UHFFFAOYSA-M 0.000 description 2
- 150000002505 iron Chemical class 0.000 description 2
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- 239000012798 spherical particle Substances 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 1
- 229910018557 Si O Inorganic materials 0.000 description 1
- 229910002803 Si-O-Fe Inorganic materials 0.000 description 1
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- CUPCBVUMRUSXIU-UHFFFAOYSA-N [Fe].OOO Chemical compound [Fe].OOO CUPCBVUMRUSXIU-UHFFFAOYSA-N 0.000 description 1
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- XIEPJMXMMWZAAV-UHFFFAOYSA-N cadmium nitrate Inorganic materials [Cd+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O XIEPJMXMMWZAAV-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention provides a modified ferrihydrite and a preparation method and application thereof, and relates to the technical field of cadmium pollution treatment. The preparation method of the modified ferrihydrite comprises the following steps: fe (NO) 3 ) 3 ·9H 2 Adding the O medicine into deionized water for dissolution, then adding KOH solution, stirring vigorously, washing to remove electrolyte after precipitation, and then air-drying, grinding and sieving to obtain ferrihydrite powder; then the ferrihydrite powder is put into a centrifuge tube, and different concentrations are addedShaking the sodium silicate solution at constant temperature in a constant-temperature water bath, culturing for 24 hours, taking out, putting into a centrifuge, centrifuging, removing supernatant, and freeze-concentrating the rest precipitate to obtain the modified ferrihydrite. The modified ferrihydrite provided by the invention has the advantages of more pores, large specific surface area and more adsorption sites for metal ions, and the adsorption capacity of the modified ferrihydrite on heavy metal ions such as cadmium ions is obviously better than that of common ferrihydrite, so that the modified ferrihydrite can be used for treating soil and water body polluted by cadmium.
Description
Technical Field
The invention relates to the technical field of treatment of cadmium pollution, in particular to modified ferrihydrite, a preparation method and application thereof.
Background
Cadmium is an important chemical element and has wide application and important economic value. It is widely used in the industrial fields of batteries, alloys, coatings, plastics, cosmetics, pigments, etc. However, due to the toxicity and environmental accumulation of cadmium, much attention is paid to the treatment and application of cadmium ions to prevent irreversible damage to the environment. Cadmium has high toxicity and potential harm to human health and environment. The industrial wastewater contains cadmium ions and a plurality of heavy metal ions which seriously pollute the environment, if the heavy metal ions cannot be effectively treated, the heavy metal ions flow into the natural environment for a long time, and the environment is a huge strike for the whole ecological environment. Therefore, the method has important significance for pollution and control of cadmium element.
Ferrihydrite (Ferrihydrite) is a common ferrite mineral, and is a component of iron oxyhydroxide (FeOOH) with a chemical formula of Fe 5 OH 8 ·4H 2 O. Its crystal structure belongs to monoclinic system and has typical alpha-FeOOH structure. The ferrihydrite has good adsorption performance and particularly has remarkable effect on the adsorption of heavy metal ions. Since oxygen and hydrogen atoms in the lattice structure can form strong chemical bonds with metal ions, the ferrierite can effectively adsorb and fix the metal ions in the solution. In addition, the ferrihydrite also has certain ion exchange capacity and can exchange with ions in the solution. Overall, ferrihydrite, a common ferrite mineral, has rich structural and property characteristics. The characteristics of stability, adsorption performance, optical magnetism and the like provide a wide prospect for the application of the catalyst in the fields of environmental management, catalytic reaction, material science and the like.
However, natural ferrihydrite has a limited ability to adsorb contaminants, so that in both theoretical research and engineering practice, scholars have begun to focus on modification of ferrihydrite to further increase its reactivity and utilization efficiency. However, the modification method which is too complicated is often complicated in process and high in cost, so that the actual use meaning of the modified material is still not great.
Accordingly, a modified ferrihydrite, a method for preparing the same and applications thereof are provided by those skilled in the art to solve the problems set forth in the background art.
Disclosure of Invention
(one) solving the technical problems
Aiming at the defects of the prior art, the invention provides a modified ferrihydrite, a preparation method and application thereof, and solves the problems that the complicated modification method is often complicated in process and high in cost, so that the actual use meaning of the modified material is still not great.
(II) technical scheme
In order to achieve the above purpose, the invention is realized by the following technical scheme:
the preparation method of the modified ferrihydrite comprises the following steps:
step 1, firstly, 35 to 46g of Fe (NO) is weighed on an electronic balance 3 ) 3 ·9H 2 Placing the O medicine into a 1000mL beaker, and then adding 500mL deionized water to dissolve the O medicine;
step 2, waiting for Fe (NO) 3 ) 3 ·9H 2 After the O medicine is completely dissolved, 300-360 mL of 1mol/L KOH solution is added into the solution, wherein the last 20mL is added dropwise, the pH is regulated to 7-8, and the solution is vigorously stirred, and electrolyte is removed by washing after precipitation;
step 3, naturally air-drying at a shady and cool ventilation place, grinding uniformly after air-drying, and sieving with a 100-mesh sieve to obtain ferrihydrite powder for later use;
step 4, weighing a proper amount of ferrihydrite powder, putting the ferrihydrite powder into a 500mL centrifuge tube, respectively adding sodium silicate solutions with different concentrations, and oscillating at constant temperature in a constant-temperature water bath;
step 5, culturing for 16-32 h under the constant temperature condition, taking out, putting into a centrifuge for centrifugation, and extracting part of supernatant after centrifugation is finished;
and 6, freezing the residual precipitation liquid in the centrifuge tube at the temperature of between 90 ℃ below zero and 70 ℃ below zero for 40 to 56 hours, and concentrating by adopting a freezing vacuum rotary instrument until powdery substances are obtained, thus obtaining the modified ferrihydrite.
Preferably, in the step S2, the alkali liquor dropwise adding rate of slowly adjusting the pH value of the mixed solution of the KOH solution is 1-2 mL/min.
Preferably, in the step S4, the concentration of the added sodium silicate solution is 90mg/L or 120mg/L and SiO is used 2 Is calculated.
Preferably, in the step S4, the constant temperature oscillation time is 2 hours, and the oscillation speed is 80r/min.
Preferably, in the step S5, the rotation speed of the centrifugal machine is 4000r/min, and the centrifugation time is 10min.
Preferably, after the step S6, a low-temperature drying treatment is further required to store the obtained modified ferrihydrite, wherein the drying mode is vacuum freeze drying, and the temperature of the vacuum freeze drying is-30 to-50 ℃.
The embodiment of the invention also provides the modified ferrihydrite prepared by the preparation method.
The embodiment of the invention also provides application of the modified iron ore in the heavy metal cadmium ion adsorption process.
Preferably, the heavy metal comprises cadmium.
Preferably, the method for treating cadmium pollution by the modified ferrihydrite comprises the following steps: under the conditions that the temperature is 308-318 and the K, pH value is 7-8, the modified ferrihydrite is utilized to adsorb heavy metal cadmium ions in the soil and the water body polluted by cadmium.
(III) beneficial effects
The invention provides modified ferrihydrite and a preparation method and application thereof. The beneficial effects are as follows:
1. the modified ferrihydrite is obtained after the modification of silicon, the adsorption of heavy metal cadmium is promoted, the desorption amount is reduced, the achievement has important application value in practice, the specific surface area and the pore structure of the modified ferrihydrite are changed, and the adsorption of the heavy metal cadmium is more facilitated.
2. The invention provides a modified ferrihydrite, a preparation method and application thereof, wherein the adsorption and desorption effects of the modified ferrihydrite on cadmium are influenced by the environment, the higher the temperature is, the better the adsorption effect on cadmium ions is, the adsorption effect is the best when the pH value is 7, the desorption is opposite to the adsorption and desorption, the adsorption and desorption reaction reaches a saturated state for about 2 hours, the maximum adsorption capacity is 23.7326mg/g under the condition that 318K and pH value are 7 and vibrate for 2 hours, and the minimum desorption capacity is 0.0303mg/g under the condition that 298K and pH value is 4 and does not vibrate.
3. The invention provides a modified ferrihydrite and a preparation method and application thereof, and through adsorption research of the modified ferrihydrite on cadmium ions, the modified ferrihydrite is found to have good adsorption performance under proper conditions, and can efficiently remove the cadmium ions, and the research provides theoretical and experimental basis for modification of the ferrihydrite and application of the modified ferrihydrite in the field of heavy metal ion adsorption.
Drawings
FIG. 1 is an electron microscope scan of ferrihydrite produced in comparative example 1 of the present invention;
FIG. 2 is an electron microscope scan of the modified ferrihydrite prepared in example 3 of the present invention;
FIG. 3 is an infrared spectrum of the modified ferrihydrite produced in example 3 and the ferrihydrite produced in comparative example 1 according to the present invention;
FIG. 4 is an N2 desorption isotherm plot of the modified ferrihydrite produced in example 3 and the ferrihydrite produced in comparative example 1 according to the present invention;
FIG. 5 is a graph showing the pore size distribution of BJH of the modified ferrihydrite produced in example 3 and the ferrihydrite produced in comparative example 1 according to the present invention;
FIG. 6 is an X-ray diffraction pattern of the modified ferrihydrite produced in example 3 and the ferrihydrite produced in comparative example 1 according to the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1:
the embodiment provides a preparation method of modified ferrihydrite, which specifically comprises the following steps:
step 1, 35g of Fe (NO) was weighed on an electronic balance 3 ) 3 ·9H 2 Placing the O medicine into a 1000mL beaker, and then adding 500mL deionized water to dissolve the O medicine;
step 2, waiting for Fe (NO) 3 ) 3 ·9H 2 After the O medicine is completely dissolved, 300mL of 1mol/L KOH solution is added into the solution, wherein the last 20mL is added dropwise, the pH is regulated to 7, the solution is vigorously stirred, and electrolyte is removed by washing after precipitation;
step 3, naturally air-drying at a shady and cool ventilation place, grinding uniformly after air-drying, and sieving with a 100-mesh sieve to obtain ferrihydrite powder for later use;
step 4, weighing 2g of ferrihydrite powder, putting the ferrihydrite powder into a 500mL centrifuge tube, adding 200mL of sodium silicate solution with mass concentration of 90mg/L calculated by silicon dioxide, and oscillating at constant temperature in a constant-temperature water bath, wherein the constant-temperature oscillating time is 2 hours, and the oscillating speed is 80r/min;
step 5, culturing for 16 hours under the constant temperature condition, taking out and putting into a centrifugal machine for centrifugation, and extracting part of supernatant liquid for discarding after the centrifugation is finished, wherein the rotation speed of the centrifugal machine is 4000r/min, and the centrifugation time is 10min;
and 6, freezing the residual precipitation liquid in the centrifuge tube at the temperature of minus 90 ℃ for 40 hours, and concentrating by adopting a freezing vacuum rotary instrument until powdery substances are obtained, thus obtaining the modified ferrihydrite.
After the step 6, a low-temperature drying treatment is needed to store the obtained modified ferrihydrite, wherein the drying mode is vacuum freeze drying, and the temperature of the vacuum freeze drying is-30 ℃.
Example 2:
the embodiment provides a preparation method of modified ferrihydrite, which specifically comprises the following steps:
step 1, firstly, 46g of Fe (NO) is weighed on an electronic balance 3 ) 3 ·9H 2 O medicine is put intoIn a 1000mL beaker, 500mL deionized water was added to dissolve the solution;
step 2, waiting for Fe (NO) 3 ) 3 ·9H 2 After the O medicine is completely dissolved, 360mL of 1mol/L KOH solution is added into the solution, wherein the last 20mL is added dropwise, the pH is regulated to 8, the solution is vigorously stirred, and electrolyte is removed by washing after precipitation;
step 3, naturally air-drying at a shady and cool ventilation place, grinding uniformly after air-drying, and sieving with a 100-mesh sieve to obtain ferrihydrite powder for later use;
step 4, weighing 4g of ferrihydrite powder, putting the ferrihydrite powder into a 500mL centrifuge tube, adding 200mL of sodium silicate solution with mass concentration of 110mg/L calculated by silicon dioxide, and oscillating at constant temperature in a constant-temperature water bath, wherein the constant-temperature oscillating time is 2 hours, and the oscillating speed is 80r/min;
step 5, culturing for 32 hours under the constant temperature condition, taking out and putting into a centrifugal machine for centrifugation, and extracting part of supernatant after centrifugation is finished, wherein the rotation speed of the centrifugal machine is 4000r/min, and the centrifugation time is 10min;
and 6, freezing the residual precipitation liquid in the centrifuge tube at the temperature of-70 ℃ for 56 hours, and concentrating by adopting a freezing vacuum rotary instrument until powdery substances are obtained, thus obtaining the modified ferrihydrite.
After the step 6, a low-temperature drying treatment is needed to store the obtained modified ferrihydrite, wherein the drying mode is vacuum freeze drying, and the temperature of the vacuum freeze drying is-50 ℃.
Example 3:
the embodiment provides a preparation method of modified ferrihydrite, which specifically comprises the following steps:
step 1, first 40g of Fe (NO) was weighed on an electronic balance 3 ) 3 ·9H 2 Placing the O medicine into a 1000mL beaker, and then adding 500mL deionized water to dissolve the O medicine;
step 2, waiting for Fe (NO) 3 ) 3 ·9H 2 After the O drug was completely dissolved, 330mL of 1mol/L KOH solution was added to the solution, the last 20mL was added dropwise, and the pH was adjusted7, stirring vigorously, washing to remove electrolyte after precipitation;
step 3, naturally air-drying at a shady and cool ventilation place, grinding uniformly after air-drying, and sieving with a 100-mesh sieve to obtain ferrihydrite powder for later use;
step 4, weighing 3g of ferrihydrite powder, putting the ferrihydrite powder into a 500mL centrifuge tube, adding 200mL of sodium silicate solution with mass concentration of 110mg/L calculated by silicon dioxide, and oscillating at constant temperature in a constant-temperature water bath, wherein the constant-temperature oscillating time is 2 hours, and the oscillating speed is 80r/min;
step 5, culturing for 24 hours under the constant temperature condition, taking out and putting into a centrifugal machine for centrifugation, and extracting part of supernatant after centrifugation is finished, wherein the rotation speed of the centrifugal machine is 4000r/min, and the centrifugation time is 10min;
and 6, freezing the residual precipitation liquid in the centrifuge tube at the temperature of minus 80 ℃ for 48 hours, and concentrating by adopting a freezing vacuum rotary instrument until powdery substances are obtained, thus obtaining the modified ferrihydrite.
After the step 6, a low-temperature drying treatment is needed to store the obtained modified ferrihydrite, wherein the drying mode is vacuum freeze drying, and the temperature of the vacuum freeze drying is-40 ℃.
Comparative example 1:
the comparative example provides a preparation method of modified ferrihydrite, specifically, the preparation method of modified ferrihydrite comprises the following steps:
step 1, first 40g of Fe (NO) was weighed on an electronic balance 3 ) 3 ·9H 2 Placing the O medicine into a 1000mL beaker, and then adding 500mL deionized water to dissolve the O medicine;
step 2, waiting for Fe (NO) 3 ) 3 ·9H 2 After the O medicine is completely dissolved, 330mL of 1mol/L KOH solution is added into the solution, wherein the last 20mL is added dropwise, the pH is regulated to 7-8, the solution is vigorously stirred, and electrolyte is removed by washing after precipitation;
and step 3, naturally air-drying at a shady and ventilated place, grinding uniformly after air-drying, and sieving with a 100-mesh sieve to obtain the ferrihydrite powder.
The embodiment of the invention also provides the modified ferrihydrite prepared by the preparation method.
The embodiment of the invention also provides application of the modified iron ore in the heavy metal cadmium ion adsorption process.
The modified ferrihydrite produced in example 3 above and the ferrihydrite produced in comparative example 1 were subjected to electron microscopy. Referring to fig. 1 to 2, in which fig. 1 is an electron microscopic scan of the ferrihydrite prepared in comparative example 1, it can be seen from the figure that the ferrihydrite prepared in comparative example 1 is a non-uniform particulate matter, the individual particles are large, the surface is rough, the crystallinity is poor, the appearance is irregular, and it is a mineral with no fixed morphology, and most of it presents small particles, and the particulate matter clusters together to form a particularly compact polymer; in addition, fig. 2 is an electron microscopic scan of the modified ferrihydrite produced in example 3, and it can be seen from the graph that the modified ferrihydrite produced in example 3 has a larger spherical particle size, increased porosity, more loose structure, larger spherical particle size, further increased pore diameter, more uniform, relatively regular morphology, more adsorption sites for metals, and more adsorption capacity than the ferrihydrite produced in comparative example 1.
The modified ferrihydrite obtained in example 3 was subjected to infrared spectroscopic analysis, the analysis results of which are shown in FIG. 3, FIG. 3 shows the infrared spectra of the modified ferrihydrite obtained in example 3 and various treatments, and it can be seen from the figure that the infrared spectra were obtained at 460cm -1 The absorption peak at the position is a bending vibration peak of tetrahedral Si-O, 1789cm -1 The absorption band at the position is an expansion vibration peak of Si-O-Fe bond, 834cm -1 The nitrate complex of the inner layer of the two teeth. 3431cm -1 Is the absorption peak of the stretching vibration and bending vibration of the water molecule, 1384cm -1 Is the absorption peak of nitrate in ferrihydrite. 892cm -1 、795cm -1 Is characteristic peak of ferrihydrite, 834cm -1 、706cm -1 Is the bending vibration band of nitrate. After modification, si-O-bond forms a new telescopic vibration peak with the iron matrix on the surface of the ferrites, which indicates that the modification is successful.
The modified ferrihydrite produced in example 3 and the ferrihydrite produced in comparative example 1 were measured according to BET and BJH, respectivelyThe specific surface area and pore diameter were measured by the method, and the specific surface area and pore diameter of ferrihydrite were measured by using F-SORB3400 type specific surface area pore diameter analyzer, and the measurement results were shown in FIGS. 4 to 5, as can be seen from FIG. 4, in N 2 In the adsorption-desorption test, with N 2 The relative pressure (p/p 0) increases, modifying N on ferrihydrite 2 The adsorption amount of (2) is also increasing. N (N) 2 Molecules are adsorbed on the inner surface of the pores of the material mainly in a single layer or multiple layers. When the pressure is in the range of 0.19-0.50, the adsorption quantity is increased sharply; when the pressure is within the range of 0.54-0.97, the adsorption quantity changes smoothly; when the relative pressure (p/p 0) is 0.97 to 1.0, the adsorption amount increases to the maximum value. This is N 2 The molecules are subjected to capillary condensation in the pore canal of the material. And N of modified sample 2 The adsorption amount is higher than that of the raw iron ore because new pore structures are formed among the modified particles.
As can be seen from FIG. 5, the pore diameters of the modified ferrihydrite produced in example 3 and the ferrihydrite produced in comparative example 1 are both in the range of 1.65 to 4.86nm, and refinement of the modified sample particles causes an increase in inter-particle pore density and an increase in pore diameter. And the average pore diameters of the two samples are 2.39nm and 2.83nm respectively, and the cumulative pore volumes are 0.0202cm respectively 3 ·g -1 And 0.0346cm 3 ·g -1 The pore size and pore volume of the modified sample are both increased, and the increase in average pore size and pore volume also confirms the change in pore structure of the sample. The specific surface area of the ferrihydrite prepared in comparative example 1 is 165.17m 2 ·g -1 The method comprises the steps of carrying out a first treatment on the surface of the The modified ferrihydrite prepared in example 3 has a specific surface area of 177.80m 2 ·g -1 The specific surface area of the modified ferrihydrite is also increased. Analysis of the pore structure data of the ferrihydrite revealed that the pore structure of the ferrihydrite was smaller and the cumulative pore volume was also smaller, while the pore volume of the modified ferrihydrite was increased, probably due to the new pore structure formed by the ferrihydrite particles acting with the silica gel. Therefore, the pore diameter and the pore volume of the ferrihydrite after the modification of the silicon are increased, the specific surface area is increased, and the adsorption capacity of the modified ferrihydrite to the metal cadmium is improved.
The modified ferrihydrite obtained in example 3 and the ferrihydrite obtained in comparative example 1 were subjected to x-ray diffraction measurement, and as shown in fig. 6, the product of ferrihydrite and modified ferrihydrite has no sharp peaks and poor crystallinity, and is amorphous. The tiny peaks of the ferrihydrite, which occur approximately at the 2 theta positions of 25 degrees and 40 degrees, are characteristic peaks of goethite, and indicate that a small amount of ferrihydrite is converted into goethite in the process of synthesizing the ferrihydrite. The three samples in the figure have two relatively distinct broad peaks at positions 41 ° and 75 ° in 2 theta. The standard atlas card was substantially identical compared to the former study (Gautier, 2006; kuKKKAdapu, 2003), and was slightly shifted to the right because in scanning samples, in order to increase resolution, a scan pattern was used that was greater than 2 theta. Two sharp peaks appear at 22 DEG and 35 DEG, particularly sharp peaks with very high intensity appear at 35 DEG, which indicate that new crystals are generated at the two places, and according to the results of the tests and the documents examined, it can be deduced that new complexes are generated between the Si-Cd and the hydroxyl groups and the Fe on the ferrihydrite or complexes exist in the form of interpolymers. Therefore, the ferrihydrite has fewer spectral peaks, a broader peak shape, and is an amorphous peak. Many auxiliary peaks appear in the XRD pattern of ferrihydrite, indicating that the degree of crystallization of ferrihydrite is very low, which is consistent with Schwertmann and Cornell (1991) believing that ferrihydrite is an amorphous oxide of low degree of crystallization. The broad diffraction peaks in the spectrum show that the modified ferrihydrite crystals prepared in example 3 have small particle sizes, so that more surface adsorption sites can be provided, and the adsorption capacity is enhanced. After the modified ferrihydrite adsorbs cadmium, a new peak is generated on the basis of the original two peaks, which indicates that the Si-O-Cd complex or the copolymerization complex with iron participation is generated.
The modified ferrihydrite prepared in example 3 was subjected to adsorption and desorption experiments at 298K, 308K, 318K, pH 4-8, and Si concentration of 120mg/L for cadmium ion solutions of 10mg/L, 20mg/L, 40mg/L, 60mg/L, 80mg/L, and 100mg/L, respectively, and the experimental results were shown in tables 1-15 below.
TABLE 1 adsorption and desorption effects of modified ferrihydrite on cadmium ions at a temperature of 298 to K, pH of 4
TABLE 2 adsorption and desorption effects of modified ferrihydrite on cadmium ions at a temperature of 298 to K, pH of 5
TABLE 3 adsorption and desorption effects of modified ferrihydrite on cadmium ions at a temperature of 298 to K, pH of 6
TABLE 4 adsorption and desorption effects of modified ferrihydrite on cadmium ions at a temperature of 298 to K, pH of 7
TABLE 5 adsorption and desorption effects of modified ferrihydrite on cadmium ions at a temperature of 298 to K, pH of 8
TABLE 6 adsorption and desorption effects of modified ferrihydrite on cadmium ions at a temperature of 308℃ 308K, pH at 4
TABLE 7 adsorption and desorption effects of modified ferrihydrite on cadmium ions at a temperature of 308℃ 308K, pH at 5
TABLE 8 adsorption and desorption effects of modified ferrihydrite on cadmium ions at a temperature of 308℃ 308K, pH at 6
TABLE 9 adsorption and desorption effects of modified ferrihydrite on cadmium ions at a temperature of 308℃ 308K, pH at 7
TABLE 10 adsorption and desorption effects of modified ferrihydrite on cadmium ions at a temperature of 308℃ 308K, pH at 8
TABLE 11 adsorption and desorption effects of modified ferrihydrite on cadmium ions at a temperature of 318 to K, pH of 4
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TABLE 12 adsorption and desorption effects of modified ferrihydrite on cadmium ions at a temperature of 318 to K, pH at 5
TABLE 13 adsorption and desorption effects of modified ferrihydrite on cadmium ions at a temperature of 318 to K, pH of 6
TABLE 14 adsorption and desorption effects of modified ferrihydrite on cadmium ions at a temperature of 318 to K, pH at 7
TABLE 15 adsorption and desorption effects of modified ferrihydrite on cadmium ions at a temperature of 318℃ 318K, pH at 8
As can be seen from tables 1 to 15 above, the adsorption amount of the modified ferrihydrite to the heavy metal cadmium becomes larger with the increase of the pH value of the solution, while the desorption amount is the opposite. When the temperature is 318K and the pH value is 8, the adsorption quantity of the adsorbent to cadmium reaches the maximum value, but when the pH value is 8, cadmium ions are partially hydrolyzed to generate precipitate, so that the adsorption quantity is overlarge, the real result of an adsorption and desorption test is confused, and the error judgment is obtained on the adsorption of the cadmium ions by the modified ferrihydrite. Therefore, the adsorption capacity at pH 7 is selected as the optimal value, the maximum adsorption capacity is 23.7326mg/g and the desorption capacity is 0.1606mg/g; and when the temperature is 298K and the pH value is 4, the adsorption quantity of the modified ferrihydrite to cadmium ions is minimum and the desorption quantity is maximum, namely, 17.7492mg/g and 0.1811mg/g.
The experimental data prove that the adsorption and desorption effects of the modified ferrihydrite on cadmium ions are influenced by the environment, the higher the temperature is, the better the adsorption effect of the modified ferrihydrite on the cadmium ions is, the better the adsorption effect is when the pH value is 7, and the desorption is opposite to the adsorption and desorption, and the adsorption and desorption reactions reach a saturated state for about 2 hours. The maximum adsorption capacity is 23.7326mg/g under the condition of 318K and pH 7 oscillation for 2 hours; the minimum desorption amount is 0.0303mg/g under the condition of no oscillation at the pH of 298K and 4.
The thermodynamic research result shows that the adsorption process of the ferrihydrite to the cadmium is an endothermic process, and the adsorption reaction is facilitated by increasing the reaction temperature. The Δg value is less than zero, indicating that the reaction can proceed spontaneously without the aid of external conditions.
The observation by an electron microscope shows that the morphology of the ferrihydrite is in a compact sphere shape, and after the silicon is added, the morphology of the ferrihydrite is loosened, a large number of gaps are formed, and the adsorption performance is improved.
The infrared characterization result shows that a new adsorption peak appears on the surface of the modified ferrihydrite, which indicates that new substances are generated on the surface of the ferrihydrite.
BET and BJH analysis results show that the modified ferrihydrite forms a new pore structure, the pore volume and the active site are obviously increased, the specific surface area is increased, and the adsorption of cadmium ions is facilitated.
The above experiments for adsorbing cadmium ions all used the following methods: firstly, 1.3g of ferrihydrite or modified ferrihydrite is weighed and ground into powder, the powder is placed in a 100mL centrifuge tube, then, cadmium nitrate solutions (the nickel ion concentration is 0, 10, 20, 40, 60, 80 and 100 mg/L) with different concentrations calculated by cadmium ions are added to be 25mL, the pH value of the mixed solution is adjusted to a value required by an experiment, then, the mixed solution is placed at a set temperature (298K, 308K or 318K) respectively for oscillation for 2 hours, the vibration speed is 80r/min, after the oscillation, the centrifuge tube is cultivated for 24 hours under the constant temperature condition, the centrifuge tube is taken out and placed in a centrifuge with the rotating speed of 4000r/min for centrifugation for 10min, after the centrifugation is finished, the supernatant is extracted and filtered, the content of cadmium ions is measured by an atomic absorption spectrophotometry, and the adsorption quantity is calculated according to the difference between the cadmium ion content of the solution before and after the balance.
The desorption experiments on cadmium ions all adopt the following methods: after the adsorption experiment is completed, the supernatant is separated, the weight of the centrifuge tube and the sample is weighed, the weight of the residual liquid and the content of cadmium ions in the residual liquid are calculated,then 0.01mol/L NaNO is added into the centrifuge tube 3 The solution is added with sodium nitrate to complement ion difference, and then is placed at a set temperature (298K, 308K or 318K) to oscillate for 2 hours, the oscillation speed is 80r/min, after oscillation, the centrifuge tube is cultivated for 24 hours under the constant temperature condition, then the centrifuge tube is taken out and put into a centrifuge with the rotation speed of 4000r/min to be centrifuged for 10 minutes, after centrifugation is finished, the supernatant is pumped out and filtered, the content of cadmium ions is measured by an atomic absorption spectrophotometry, and the desorption amount is calculated according to the difference between the cadmium ion content of the solution before and after desorption.
In addition, the above-mentioned instruments and reagents not specifically described are commercially available products.
In conclusion, the modified ferrihydrite prepared by the embodiment of the invention has excellent adsorption capacity on heavy metal ions such as cadmium ions and the like, and can be used for treating cadmium pollution. Under the conditions that the temperature is 318K and the pH value is 7 and the vibration is carried out for 2 hours, the adsorption capacity of the modified ferrihydrite on cadmium ions is strong.
According to the invention, through the adsorption research of the modified ferrihydrite on the cadmium ions, the modified ferrihydrite is found to have good adsorption performance under proper conditions, and the cadmium ions can be efficiently removed.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (9)
1. The preparation method of the modified ferrihydrite is characterized by comprising the following steps of:
step 1, firstly, 35 to 46g of Fe (NO) is weighed on an electronic balance 3 ) 3 ·9H 2 Placing the O medicine into a 1000mL beaker, and then adding 500mL deionized water to dissolve the O medicine;
step 2, waiting for Fe (NO) 3 ) 3 ·9H 2 After the O medicine is completely dissolved, 300-360 mL of 1mol/L is added into the solutionKOH solution, wherein the last 20mL is added dropwise, the pH is regulated to 7-8, and the solution is vigorously stirred, and electrolyte is removed by washing after precipitation;
step 3, naturally air-drying at a shady and cool ventilation place, grinding uniformly after air-drying, and sieving with a 100-mesh sieve to obtain ferrihydrite powder for later use;
step 4, weighing a proper amount of ferrihydrite powder, putting the ferrihydrite powder into a 500mL centrifuge tube, respectively adding sodium silicate solutions with different concentrations, and oscillating at constant temperature in a constant-temperature water bath;
step 5, culturing for 16-32 h under the constant temperature condition, taking out, putting into a centrifuge for centrifugation, and extracting part of supernatant after centrifugation is finished;
and 6, freezing the residual precipitation liquid in the centrifuge tube at the temperature of between 90 ℃ below zero and 70 ℃ below zero for 40 to 56 hours, and concentrating by adopting a freezing vacuum rotary instrument until powdery substances are obtained, thus obtaining the modified ferrihydrite.
2. The method for preparing modified ferrihydrite according to claim 1, wherein in step 2, the alkali solution drop rate of slowly adjusting the pH value of the mixed solution by dropwise adding KOH solution is 1-2 mL/min.
3. The process for preparing modified ferrihydrite according to claim 1, wherein in step 4, the sodium silicate solution is added at a concentration of 90mg/L or 120mg/L and is prepared as SiO 2 Is calculated.
4. The method for preparing modified ferrihydrite according to claim 1, wherein in step 4, the constant temperature oscillation time is 2 hours, and the vibration speed is 80r/min.
5. The method for preparing modified ferrihydrite according to claim 1, wherein in step 5, the rotational speed of the centrifuge is 4000r/min and the centrifugation time is 10min.
6. The method for preparing modified ferrihydrite according to claim 1, wherein after the step 6, a low-temperature drying treatment is further required to store the obtained modified ferrihydrite, the drying mode is vacuum freeze drying, and the temperature of the vacuum freeze drying is-30 to-50 ℃.
7. A modified ferrihydrite produced by the production process according to any one of claims 1 to 7.
8. The use of a modified ferrihydrite composite according to claim 7 in heavy metal insulator adsorption processes.
9. The use of modified ferrierite according to claim 8, wherein said heavy metal comprises cadmium.
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