Method for preparing iron film by using iron-rich solution

Abstract

The invention discloses a method for preparing an iron film by using an iron-rich solution. The method comprises the following steps: step 1, preparing the iron-rich solution; step 2, solution pretreatment; step 3, carrying out hydrothermal reaction; step 4, sample recovery; according to the method, the iron oxide film is directly generated on the gas-liquid interface, the thickness can be controlled within 20 microns, and controllable synthesis and directional conversion are achieved by optimizing parameters. No organic solvent is used, so that the loss of the organic solvent and the generation of organic wastewater are avoided, and the environmental protection property is good. The prepared iron oxide film shows good inertness, strong acid etching resistance, no obvious magnetic response, no photocatalytic activity, no persulfate activation effect and stable performance. Iron can be efficiently and selectively separated from the iron-rich solution generated by inorganic acid extraction, loss of rare earth or heavy metal is avoided, the method is suitable for treating iron-containing waste, and waste recycling is achieved.

Description

Technical Field

[0001] The invention relates to the field of chemical engineering and environmental technology, and in particular to a method for preparing an iron film by utilizing an iron-rich solution. Background Art

[0002] Inorganic thin film materials are widely used in national production industries, providing important functions such as corrosion protection, wear resistance, antioxidant properties, thermal insulation, and catalysis. Traditional inorganic thin films are typically formed on the surface of a substrate through redox reactions, coordination complexation, and particle deposition to form micron- or nanometer-thick films. However, separating these thin film materials from the substrate surface is difficult.

[0003] To address this issue, several methods have been developed to directly obtain inorganic thin film materials. One approach involves using conventional organic membrane materials to prepare organic-inorganic membrane materials, which are then deorganized to produce inorganic membrane materials. Another approach involves chemical reactions at the interface of immiscible solvents (such as water and n-hexane) to produce inorganic membrane materials. However, these methods have drawbacks, such as the potential use of organic solvents, which can lead to solvent loss and the generation of organic wastewater.

[0004] Directly preparing inorganic thin films on aqueous solutions avoids the use of organic solvents. Iron oxide films prepared using this method can exhibit novel physical and chemical phenomena and application properties. Recovering valuable components from wastes such as iron-containing waste sludge requires dissolving the sludge in a strong acid to generate an iron-rich solution, which is then separated to recover the valuable elements. If the iron in such leachates could be directly separated into an iron-based film, novel waste recycling methods could be achieved. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing an iron film using an iron-rich solution to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing an iron film using an iron-rich solution, comprising the following steps:

[0007] Step 1: preparing an iron-rich solution: the iron-rich solution is obtained from a solution prepared from chemical reagents or a hydrochloric acid or sulfuric acid leaching solution of high-iron-containing waste;

[0008] Step 2: Solution pretreatment: Rapidly cool the prepared solution to 4°C and refrigerate for 24 hours; then, after warming to room temperature, adjust the initial pH of the solution to a range of -0.1 to 1.2 using 2-3 M hydrochloric acid or sulfuric acid;

[0009] Step 3, performing a hydrothermal reaction: conditioning the pretreated solution before the reaction, placing the conditioned solution into a reactor to increase the temperature, keeping the temperature, and then adjusting the pressure. Finally, stopping the heating and cooling the solution to room temperature;

[0010] Step 4: Sample recovery: Open the reactor and pour in the solution pretreated in step 2. The liquid level will rise and the film will float up and be taken out.

[0011] Preferably, the step 1 is specifically a solution prepared by chloride or sulfate, wherein the ferrous iron concentration is 80-135 g / L; if it comes from iron-containing waste, hydrochloric acid or sulfuric acid is used for leaching and dissolving to generate a ferrous iron-rich solution;

[0012] Adjust the concentration of neodymium or praseodymium: if neodymium is used, add neodymium to the solution at a mass ratio of 1:3-1:6 to iron; if praseodymium is used, add praseodymium to the solution at a mass ratio of 1:10-1:15 to iron;

[0013] Adjust the sodium formate dosage: Add sodium formate to the solution to a molar ratio of 1 / 60 to 1 / 90 to iron. After adding sodium formate, sonicate the solution for 30 minutes.

[0014] If the solution contains aluminum, it is necessary to remove the aluminum first to make its concentration less than 5 mg / L;

[0015] If the solution contains copper and manganese, the concentration of copper and manganese should be controlled to be less than 2g / L.

[0016] Preferably, step 3 specifically comprises: using a TOC meter to detect the TOC value of the solution; then adding sodium nitrate to the solution so that the mass ratio of sodium nitrate to TOC is in the range of 0.05-0.5; placing the tempered solution into a reactor, heating it to 160° C. at 5° C. / min, and maintaining the temperature for 4 hours; then releasing the pressure to less than 0.4 MPa, continuing the constant pressure control for 2 hours; finally, stopping heating and cooling to room temperature.

[0017] Preferably, step 4 is specifically as follows: opening the reactor and slowly pouring the solution in step 2 into the reactor; as the solution is poured in, the liquid level rises, the film floats up and is taken out intact; the surface of the film presents spherical particles with a thickness of 10-20 μm, the side facing the gas is silver, and the side facing the solution is black, showing new crystal characteristics, strong corrosion resistance, no obvious magnetic response, and no catalytic activity; during the above process, there is no loss of neodymium or praseodymium in the solution, and its concentration remains basically unchanged; after adding ferrous iron to the solution, it can be reused for film preparation.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention directly generates an iron oxide film at the gas-liquid interface, the thickness of which can be controlled within 20 μm, and realizes controllable synthesis and directional conversion by optimizing parameters. No organic solvent is required, which avoids the loss of organic solvent and the generation of organic wastewater, and has good environmental protection. The obtained iron oxide film shows good inertness, resistance to strong acid corrosion, no obvious magnetic response, no photocatalytic activity, no persulfate activation effect, and stable performance. It can efficiently and selectively separate iron from the iron-rich solution produced by inorganic acid leaching, avoid the loss of rare earth or heavy metals, and is suitable for treating iron-containing waste and realizing waste resource utilization. One-step hydrothermal synthesis, no need for subsequent treatment, simple process, short flow, easy operation, and stable operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a color map of the film of the present invention facing the gas interface;

[0021] Figure 2 is a color image of the solution-facing side of the film of the present invention;

[0022] Figure 3 is a film thickness diagram of the present invention;

[0023] Figure 4 It is a rough surface pattern formed on the surface of the film of the present invention;

[0024] Figure 5 is the XRD spectrum of the present invention;

[0025] Figure 6 is the XRF spectrum of the present invention;

[0026] Figure 7 is the XPS spectrum of the present invention;

[0027] Figure 8 is a peak diagram of ferric iron of the present invention;

[0028] Figure 9 is a graph showing the concentration of imidacloprid degraded by persulfate of the present invention;

[0029] Figure 10 is a film generation diagram of the present invention;

[0030] Figure 11 This is a morphology diagram of spherical particle stacking according to the present invention;

[0031] Figure 12 It is the diffraction peak pattern of the hematite of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] See also Figure 1-12 The present invention provides a method for preparing an iron film using an iron-rich solution, comprising the following steps:

[0034] Step 1: preparing an iron-rich solution: the iron-rich solution is obtained from a solution prepared from chemical reagents or a hydrochloric acid or sulfuric acid leaching solution of high-iron-containing waste;

[0035] Step 2: Solution pretreatment: Rapidly cool the prepared solution to 4°C and refrigerate for 24 hours; then, after warming to room temperature, adjust the initial pH of the solution to a range of -0.1 to 1.2 using 2-3 M hydrochloric acid or sulfuric acid;

[0036] Step 3, performing a hydrothermal reaction: conditioning the pretreated solution before the reaction, placing the conditioned solution into a reactor to increase the temperature, keeping the temperature, and then adjusting the pressure. Finally, stopping the heating and cooling the solution to room temperature;

[0037] Step 4: Sample recovery: Open the reactor and pour in the solution pretreated in step 2. The liquid level will rise and the film will float up and be taken out.

[0038] Step 1 is specifically a solution prepared by preparing chloride or sulfate, wherein the ferrous iron concentration is 80-135 g / L; if the source is iron-containing waste, hydrochloric acid or sulfuric acid is used to extract and dissolve the resulting ferrous iron-rich solution;

[0039] Adjust the concentration of neodymium or praseodymium: if neodymium is used, add neodymium to the solution at a mass ratio of 1:3-1:6 to iron; if praseodymium is used, add praseodymium to the solution at a mass ratio of 1:10-1:15 to iron;

[0040] Adjust the sodium formate dosage: Add sodium formate to the solution to a molar ratio of 1 / 60 to 1 / 90 to iron. After adding sodium formate, sonicate the solution for 30 minutes.

[0041] If the solution contains aluminum, it is necessary to remove the aluminum first to make its concentration less than 5 mg / L;

[0042] If the solution contains copper and manganese, the concentration of copper and manganese should be controlled to be less than 2g / L.

[0043] Specifically, step 3 includes detecting the TOC value of the solution using a TOC meter; then adding sodium nitrate to the solution so that the mass ratio of sodium nitrate to TOC is within the range of 0.05-0.5; placing the tempered solution into a reactor, heating it to 160° C. at a rate of 5° C. / min, and maintaining the temperature for 4 hours; then releasing the pressure to less than 0.4 MPa, and continuing to maintain the constant pressure for 2 hours; finally, stopping heating and cooling the solution to room temperature.

[0044] Specifically, step 4 is to open the reactor and slowly pour the solution in step 2 into the reactor; as the solution is poured in, the liquid level rises, the film floats up and is taken out intact; the surface of the film presents spherical particles with a thickness of 10-20 μm, the side facing the gas is silver, and the side facing the solution is black, showing new crystal characteristics, strong corrosion resistance, no obvious magnetic response, and no catalytic activity; during the above process, there is no loss of neodymium or praseodymium in the solution, and its concentration remains basically unchanged; after adding ferrous iron to the solution, it can be reused for film preparation.

[0045] Example 1: Synthesis of Iron Oxide Thin Films Using Chemical Reagents

[0046] (1) Prepare iron-rich solution

[0047] Prepare a solution containing ferrous sulfate, neodymium chloride, and sodium formate, with an iron concentration of 120 g / L, a 1 / 4 weight ratio of neodymium iron, and a molar ratio of sodium formate to iron of 1 / 80. Ultrasonicate the solution for 30 minutes, refrigerate at 4°C for 24 hours, and finally warm to room temperature. Adjust the pH to 1 using 3M hydrochloric acid.

[0048] (2) Hydrothermal reaction

[0049] Sodium nitrate was added to the solution in step (1) at a mass ratio of sodium nitrate to TOC of 0.1. The solution was then placed in a reactor and heated to 160°C at a rate of 5°C / min and held at this temperature for 4 hours. The pressure was then reduced to less than 0.4 MPa and the pressure was maintained at this temperature for 2 hours. Finally, heating was stopped and the solution was cooled to room temperature.

[0050] (3) Film collection

[0051] The reactor was opened and the solution in step (1) was slowly poured into the reactor; as the solution was poured in, the liquid level rose, and the film floated up and was taken out.

[0052] The color of the film to the gas interface is silvery white (attached Figure 1 ), the color of the side facing the solution is black (with Figure 2 ). Its thickness is 5-10μm (attached Figure 3 ), the surface is a rough surface formed by the stacking of multiple spherical particles (attached Figure 4 Although its XRD spectrum shows obvious diffraction peaks (Appendix Figure 5), but no corresponding spectrum was found in the corresponding JADE database. Figure 6 ) shows that the iron content is 99.98wt.%. Its corresponding XPS spectrum (attached) Figure 7 ), showing a clear peak of trivalent iron (attached Figure 8 ).

[0053] (4) Film properties

[0054] The film was broken and then placed in 3M HCl with a solid-liquid ratio of 1:100 and stirred at 120 rpm for 24 hours. No obvious iron dissolution occurred. The film fragments dispersed in the acid solution did not migrate toward the magnetic pole under a strong magnetic field. The film did not activate persulfate to degrade imidacloprid (attached Figure 9 ), and its performance is stable under oxidizing conditions.

[0055] Example 2: Preparation of iron film from NdFeB waste leachate

[0056] (1) Sludge dissolution

[0057] The waste was mixed with hydrochloric acid at a solid-to-liquid ratio of 1:3 at room temperature, then stirred at 120 rpm for 2 hours. The aqueous phase was filtered and collected. The iron content was 115 g / L, the mass ratio of praseodymium to iron was 1:13, the copper content was 0.9 g / L, and the manganese content was 1.4 g / L.

[0058] (2) Solution conditioning

[0059] Take the solution from step (1) and add sodium formate to the solution at a molar ratio of 1:70 to iron. After adding sodium formate, sonicate for 30 minutes and then refrigerate at 4°C. Before use, remove the solution and adjust the pH to 1 with 2M HCl.

[0060] (3) Hydrothermal reaction

[0061] Sodium nitrate was added to the solution tempered in step (2) at a mass ratio of 0.05 to TOC. The solution was then placed in a reactor and heated to 160°C at a rate of 10°C / min, held at this temperature for 3.5 hours. When the pressure dropped to less than 0.35 MPa, the pressure was maintained at this temperature for another 2 hours. Heating was stopped and the solution was allowed to cool to room temperature.

[0062] (4) Film collection

[0063] After opening the reactor, a thin film was observed (attached Figure 10 ), its surface still presents the morphology of spherical particle stacking (attached Figure 11 ), but there are a small number of large-sized spherical particles. Its XRD spectrum shows the unknown characteristic peak corresponding to the above, but there is also the diffraction peak of hematite (attached Figure 12 ).

[0064] (5) Process control

[0065] (5.1) Adding an equal amount of glucose or urea to the solution of step (1) to replace sodium formate, the resulting product is red hematite without film formation;

[0066] (5.2) Add 1 g / L Al to the solution in step (1) 3+ , repeating the following steps, the obtained product is red hematite, and no film is formed;

[0067] (5.3) The dosage of nitrate in the solution of step (3) was adjusted so that its weight ratio to TOC was 5 and 10. The obtained product was red hematite without film formation.

[0068] In summary, the method provided by the present invention for preparing an iron film using an iron-rich solution can efficiently prepare an iron film with good performance by rationally adjusting the solution components, performing pretreatment and hydrothermal reaction, and at the same time realize the separation and recovery of iron in the solution, which has significant economic benefits and environmental significance.

[0069] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an iron film using an iron-rich solution, characterized in that: The following steps are involved: Step 1: preparing an iron-rich solution: the iron-rich solution is obtained from a solution prepared from chemical reagents or a hydrochloric acid or sulfuric acid leaching solution of high-iron-containing waste; Step 2: Solution pretreatment: Rapidly cool the prepared solution to 4°C and refrigerate for 24 hours; then, after warming to room temperature, adjust the initial pH of the solution to a range of -0.1 to 1.2 using 2-3 M hydrochloric acid or sulfuric acid; Step 3, performing a hydrothermal reaction: conditioning the pretreated solution before the reaction, placing the conditioned solution into a reactor to increase the temperature, keeping the temperature, and then adjusting the pressure. Finally, stopping the heating and cooling the solution to room temperature; Step 4: Sample recovery: Open the reactor and pour in the solution pretreated in step 2. The liquid level will rise and the film will float up and be taken out.

2. The method for preparing an iron thin film using an iron-rich solution according to claim 1, wherein: Specifically, step 1 comprises preparing a solution of chloride or sulfate, wherein the ferrous iron concentration is 80-135 g / L; if the source is iron-containing waste, leaching and dissolving the solution with hydrochloric acid or sulfuric acid to generate a ferrous iron-rich solution; Adjust the concentration of neodymium or praseodymium: if neodymium is used, add neodymium to the solution at a mass ratio of 1:3-1:6 to iron; if praseodymium is used, add praseodymium to the solution at a mass ratio of 1:10-1:15 to iron; Adjust the sodium formate dosage: Add sodium formate to the solution to a molar ratio of 1 / 60 to 1 / 90 to iron. After adding sodium formate, sonicate the solution for 30 minutes. If the solution contains aluminum, it is necessary to remove the aluminum first to make its concentration less than 5 mg / L; If the solution contains copper and manganese, the concentration of copper and manganese should be controlled to be less than 2g / L.

3. The method for preparing an iron thin film using an iron-rich solution according to claim 1, wherein: Specifically, step 3 includes detecting the TOC value of the solution using a TOC meter; then adding sodium nitrate to the solution so that the mass ratio of sodium nitrate to TOC is within the range of 0.05-0.5; placing the tempered solution into a reactor, heating it to 160° C. at a rate of 5° C. / min, and maintaining the temperature for 4 hours; then releasing the pressure to less than 0.4 MPa, and continuing to maintain the constant pressure for 2 hours; finally, stopping heating and cooling the solution to room temperature.

4. The method for preparing an iron thin film using an iron-rich solution according to claim 1, wherein: Specifically, step 4 comprises opening the reactor and slowly pouring the solution of step 2 into the reactor; as the solution is poured in, the liquid level rises, the film floats up and is taken out intact; the surface of the film presents spherical particles with a thickness of 10-20 μm, the side facing the gas is silver, and the side facing the solution is black, showing new crystal characteristics, strong corrosion resistance, no obvious magnetic response, and no catalytic activity; during the above process, there is no loss of neodymium or praseodymium in the solution, and its concentration remains basically unchanged; after adding ferrous iron to the solution, it can be reused for film preparation.

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