Ferrihydrite and its preparation method and application

Abstract

The present invention belongs to the technical field of iron-based material synthesis, and relates to a ferrihydrite and a preparation method and application thereof. The technical problems that the process of preparing ferrihydrite in the prior art is complicated, the cost is high, and large-scale production is impossible are solved. The present application provides a method for preparing ferrihydrite, comprising the following steps: pumping water into the equipment, adding ferrous sulfate after aeration, continuing aeration, and calculating by mass ratio, the ratio of ferrous sulfate to water is 1:16-20 to obtain a ferrous sulfate solution; adding sodium hydroxide to the ferrous sulfate solution, calculating by mass ratio, the ratio of sodium hydroxide to water is 1:40-70, maintaining the pH at 7-8, and continuing aeration until ferrous ions and ferric ions are not detected to obtain ferrihydrite. The present application has a simple process and low cost. Ferrous sulfate can use a by-product of a titanium dioxide plant, can be produced on a large scale, and realizes the waste utilization of ferrous sulfate, a by-product of a titanium dioxide plant. At the same time, the present application also provides a ferrihydrite and an application thereof.

Description

Technical Field

[0001] The invention belongs to the technical field of iron-based material synthesis, and in particular relates to ferrihydrite and a preparation method and application thereof. Background Art

[0002] During the production process of titanium dioxide plants, a large amount of ferrous sulfate byproduct is produced. Its main component is FeSO4·7H2O, which is an important sulfur and iron resource. Since the production of titanium dioxide produces 2.5 to 4 tons of ferrous sulfate per ton of product, although the byproduct ferrous sulfate has various uses, the output of ferrous sulfate is too large. So far, a small amount of ferrous sulfate is used as a water purifier, fertilizer, feed additive and building materials, namely, water treatment grade ferrous sulfate or polyferric sulfate, fertilizer grade ferrous sulfate heptahydrate, feed grade ferrous sulfate monohydrate and ferrous sulfate for construction, etc. However, the demand for these products cannot completely digest the amount of ferrous sulfate byproduct in the existing sulfuric acid method titanium dioxide production. Most of the ferrous sulfate can only be piled up or buried as waste, which brings great waste and environmental pollution. How to effectively utilize these byproducts, reduce environmental pollution and realize the recycling of resources is a problem that needs to be solved.

[0003] Ferrihydrite is an iron-based magnetic material with high specific surface area and surface activity. It has excellent adsorption properties and is a functional material in the field of environmental engineering. It can be used to fix heavy metals in polluted water and soil and adsorb volatile organic compounds. Although ferrihydrite is widely present in nature, the environment in which ferrihydrite exists is extremely complex and requires a cumbersome mineral processing process to obtain. Artificial synthesis can quickly obtain high-purity ferrihydrite. At present, the raw materials for artificial synthesis of ferrihydrite are ferric chloride or ferric nitrate. Ferric chloride is highly corrosive and will corrode the reaction equipment, increasing the cost of equipment maintenance and replacement. The price of ferric nitrate is relatively high, which leads to an increase in the cost of synthesizing ferrihydrite. In addition, due to the complex synthesis process of ferrihydrite, the difficulty in controlling reaction conditions, and the complexity of post-processing, it is currently mainly synthesized in small doses in the laboratory for experimental research, and there is little large-scale artificial synthesis. Therefore, it is necessary to develop a method with simple process and suitable for large-scale production of ferrihydrite. Summary of the invention

[0004] 1. Problems to be solved

[0005] In view of the technical problems that the process of preparing ferrihydrite in the prior art is complicated, the cost is high, and large-scale production is impossible, the present application provides a method for preparing ferrihydrite, which has a simple process and low cost. Ferrous sulfate can use the by-product of titanium dioxide factory, and can be produced on a large scale, thus realizing the waste utilization of ferrous sulfate by-product of titanium dioxide factory. At the same time, the present application also provides ferrihydrite and its application.

[0006] 2. Technical solution

[0007] In order to achieve the above purpose, the technical solution provided is:

[0008] A method for preparing ferrihydrite comprises the following steps:

[0009] S1. Pump water into the device, add ferrous sulfate after aeration, continue aeration, and calculate by mass ratio, the ratio of ferrous sulfate to water is 1:16 to 20 to obtain a ferrous sulfate solution;

[0010] S2. Add sodium hydroxide to the ferrous sulfate solution, the ratio of sodium hydroxide to water is 1:40-70 by mass, the pH is maintained at 7-8, and aeration is continued until no ferrous ions and ferric ions are detected, thereby obtaining the ferrihydrite.

[0011] Preferably, the concentration of the sodium hydroxide is 200-250 g / L.

[0012] Preferably, the total dosage of sodium hydroxide is 300L to 400L.

[0013] Furthermore, the aeration time in step S1 is 30 minutes to 60 minutes; when no ferrous ions and ferric ions are detected in step S2, the cumulative aeration time is no more than 24 hours.

[0014] Furthermore, in the step S2, the ferrous ions, ferric ions and pH value are detected at target intervals;

[0015] When the cumulative aeration time is ≤12h, the target interval time is 10min to 20min;

[0016] When the cumulative aeration time is greater than 12 hours, the target interval time is 1 hour to 2 hours.

[0017] Furthermore, the equipment is a water tank with an aeration device at the bottom; the effective volume of the water tank is 9m 3 ~10m 3 .

[0018] Preferably, the water tank is cylindrical.

[0019] Furthermore, the aeration device is a rotary blower; the pressure of the rotary blower is 0.1 kg / cm 2 ~0.5kg / cm 2 .

[0020] Furthermore, the method for preparing ferrihydrite also includes the step of making the ferrihydrite into powder.

[0021] Preferably, the equipment used to make the ferrihydrite into powder is a chamber diaphragm filter press; the feed pressure is 0.8 MPa, the feed delay is 1000 s, the pressing pressure is 1 MPa, and the pressing delay is 800 s to 1200 s.

[0022] The ferrihydrite cake formed after dehydration by the chamber diaphragm filter press has a low moisture content, which is convenient for subsequent drying and crushing processing.

[0023] Furthermore, in step S2, hydroxylamine hydrochloride and o-phenanthroline are used to qualitatively detect ferrous ions and ferric ions.

[0024] Furthermore, the ferrous sulfate is taken from the by-product of a titanium dioxide plant.

[0025] A ferrihydrite is prepared according to the method.

[0026] The invention discloses an application of ferrihydrite, wherein the ferrihydrite is applied in the preparation of environmental management materials.

[0027] 3. Beneficial effects

[0028] Compared with the existing known technology, the technical solution provided by the present invention has the following beneficial effects:

[0029] (1) A method for preparing ferrihydrite of the present invention comprises the following steps: pumping water into the equipment, adding ferrous sulfate after aeration, and continuing aeration. The ratio of ferrous sulfate to water is 1:16-20 by mass ratio, thereby obtaining a ferrous sulfate solution; adding sodium hydroxide to the ferrous sulfate solution, wherein the ratio of sodium hydroxide to water is 1:40-70 by mass ratio, maintaining the pH at 7-8, and continuing aeration until no ferrous ions and ferric ions are detected, thereby obtaining the ferrihydrite. The method has a simple process flow, low cost, and can be mass-produced. Using ferrous sulfate, a by-product of a titanium dioxide plant, as a raw material to synthesize ferrihydrite can realize the resource utilization of ferrous sulfate and reduce resource waste; direct discharge or burial of ferrous sulfate can cause environmental pollution. By synthesizing ferrihydrite, environmental pollution problems can be effectively reduced, and economic benefits can be obtained by producing high value-added ferrihydrite products.

[0030] (2) The ferrihydrite of the present invention is prepared using the method, which realizes large-scale production and reduces the cost of unit products; ferrihydrite has excellent adsorption properties and has a significant removal effect on a variety of pollutants, and is an environmentally functional material.

[0031] (3) Application of the ferrihydrite of the present invention: the ferrihydrite is used in the preparation of environmental management materials to improve its stability, adsorption performance and recyclability, so as to be better applied in the fields of environmental management and catalysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The invention discloses a process flow of a method for preparing ferrihydrite.

[0033] Figure 2 This is the XRD pattern of ferrihydrite.

[0034] Figure 3 It is a schematic diagram of the water tank equipment in the embodiment, wherein: 1. water tank; 2. aeration device. DETAILED DESCRIPTION

[0035] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with embodiments.

[0036] Example 1

[0037] A method for preparing ferrihydrite in this embodiment comprises the following steps:

[0038] S1. Pump 4m3 of water into the water tank 1 equipped with an aeration device. 3 Clean water, turn on aeration device 2, aeration is carried out by a rotary blower, the fan pressure is 0.5kg / cm 2 , add 250 kg of ferrous sulfate, and continue aeration for 30 minutes to completely dissolve the ferrous sulfate to obtain a ferrous sulfate solution;

[0039] like Figure 3 As shown, the water tank 1 is cylindrical and has an effective volume of 9m 3 ~10m 3 , an aeration device 2 is provided at the bottom of the water tank 1;

[0040] S2, add 250g / L sodium hydroxide solution to obtain ferrous sulfate solution, obtain mixed ore pulp, adjust the mixed ore pulp pH to 7-8, continue aeration, then measure the mixed ore pulp pH every 10min-20min, qualitatively detect ferrous ions and ferric ions in the mixed ore pulp, according to the pH reduction, continue to add 250g / L sodium hydroxide solution to the mixed ore pulp, keep the mixed ore pulp pH at 7-8, aerate for 12h, cumulatively add 200L of sodium hydroxide solution, the pH slowly decreases after that, measure the mixed ore pulp pH every 1h-2h, qualitatively detect ferrous ions and ferric ions in the mixed ore pulp, according to the pH reduction, add 200L sodium hydroxide solution to the mixed ore pulp again in batches, keep the mixed ore pulp pH at 7-8, the total amount of sodium hydroxide solution added is 400mL, and ferrous ions and ferric ions are not detected after cumulative aeration for 24h to obtain ferrihydrite ore pulp;

[0041] Hydroxylamine hydrochloride and o-phenanthroline were used to qualitatively detect the presence of ferrous and ferric ions;

[0042] S3, start the chamber diaphragm filter press, set the feed pressure to 0.8MPa, feed delay to 1000s, press pressure to 1MPa, press delay to 1200s, feed and press the obtained ferrihydrite slurry, the total pressing time is 30min, and form ferrihydrite cake. The wet weight of the ferrihydrite cake is 180kg, and the powdered ferrihydrite obtained after drying and crushing is 100kg.

[0043] The wet weight of the ferrihydrite cake obtained in the parallel experiment ranged from 180kg to 200kg, and the powdered ferrihydrite obtained after drying and crushing ranged from 100kg to 120kg.

[0044] The process flow of a method for preparing ferrihydrite in the present application is as follows: Figure 1 As shown, the aeration device used plays an important role in the whole process of synthesizing ferrihydrite from ferrous sulfate. Aeration can not only accelerate the dissolution of ferrous sulfate, but also increase the concentration of dissolved oxygen (DO) in the solution, promote the oxidation of Fe(II) to Fe(III), thereby promoting the mineralization rate of ferrihydrite, and at the same time prevent the formed minerals from being deposited at the bottom and affecting the feed.

[0045] After the sodium hydroxide solution is added in step S2, the pH of the mixed slurry decreases rapidly due to the rapid precipitation of Fe(III). Therefore, the pH of the mixed slurry needs to be measured every 10 to 20 minutes. According to the decrease in pH, sodium hydroxide solution is added to keep the pH of the mixed slurry at 7 to 8. After 12 hours of aeration, Fe(III) decreases, the precipitation formation rate slows down, and the pH of the mixed slurry no longer decreases in the short term. Therefore, it is adjusted to measure the pH of the mixed slurry every 1 to 2 hours. According to the decrease in pH, sodium hydroxide solution is added to keep the pH of the mixed slurry at 7 to 8.

[0046] The ferrihydrite cake formed after dehydration by the chamber membrane filter press in step S3 has a low moisture content, which is convenient for subsequent drying and crushing.

[0047] The raw material ferrous sulfate for preparing ferrihydrite uses the by-product of titanium dioxide plant, which not only saves costs but also realizes the recycling of the by-product ferrous sulfate of titanium dioxide plant.

[0048] In this embodiment, the ratio of ferrous sulfate to water is 1:16, the ratio of sodium hydroxide to water is 1:40, the pH of the mixed pulp is maintained at 7-8, the total pressing time is 30 minutes, and the obtained ferrihydrite is reddish brown. Figure 2 The XRD spectrum of ferrihydrite shows that it has few and broad peaks.

[0049] Example 2

[0050] A method for preparing ferrihydrite in this embodiment comprises the following steps:

[0051] S1. Pump 4m3 of water into the water tank 1 equipped with an aeration device. 3 Clean water, turn on aeration device 2, aeration is carried out by a rotary blower, the fan pressure is 0.5kg / cm 2 , add 250 kg of ferrous sulfate, and continue aeration for 30 minutes to completely dissolve the ferrous sulfate to obtain a ferrous sulfate solution;

[0052] like Figure 3 As shown, the water tank 1 is cylindrical and has an effective volume of 9m 3 ~10m 3 , an aeration device 2 is provided at the bottom of the water tank 1;

[0053] S2, add a 250g / L sodium hydroxide solution to the ferrous sulfate solution to obtain a mixed slurry, adjust the pH of the mixed slurry to 7-8, continue aeration, then measure the pH of the mixed slurry every 10min-20min, qualitatively detect ferrous ions and ferric ions in the mixed slurry, according to the pH reduction, continue to add sodium hydroxide solution to the mixed slurry, keep the pH of the mixed slurry at 7-8, aerate for 12h, cumulatively add 200L of sodium hydroxide solution, and then the pH slowly decreases, measure the pH of the mixed slurry every 1h-2h, add 200L of sodium hydroxide solution to the mixed slurry in batches, keep the pH of the mixed slurry at 7-8, the total amount of sodium hydroxide solution added is 400mL, and no ferrous ions and ferric ions are detected after cumulative aeration for 24h to obtain ferrihydrite slurry;

[0054] Hydroxylamine hydrochloride and o-phenanthroline were used to qualitatively detect the presence of ferrous and ferric ions;

[0055] S3, start the chamber diaphragm filter press, set the feed pressure to 0.8MPa, feed delay to 1000s, press pressure to 1MPa, press delay to 800s, feed and press the obtained ferrihydrite slurry, the total pressing time is 24min, and form ferrihydrite cake. The wet weight of the ferrihydrite cake is 200kg, and the powdered ferrihydrite obtained after drying and crushing is 100kg.

[0056] The wet weight of the ferrihydrite cake obtained in the parallel experiments ranged from 200kg to 220kg, and the powdered ferrihydrite obtained after drying and crushing ranged from 100kg to 120kg.

[0057] The constant pressure pressing time of this embodiment is shortened and the moisture content of the ore cake is increased.

[0058] In this embodiment, the ratio of ferrous sulfate to water is 1:16, the ratio of sodium hydroxide to water is 1:40, the pH of the mixed slurry is maintained at 7-8, the total pressing time is 24 minutes, and the obtained ferrihydrite is reddish brown.

[0059] Example 3

[0060] A method for preparing ferrihydrite in this embodiment comprises the following steps:

[0061] S1. Pump 5m3 of water into the water tank 1 equipped with an aeration device. 3 Clean water, turn on aeration device 2, aeration is carried out by a rotary blower, the fan pressure is 0.5kg / cm 2 , add 250 kg of ferrous sulfate, and continue aeration for 30 minutes to completely dissolve the ferrous sulfate to obtain a ferrous sulfate solution;

[0062] like Figure 3 As shown, the water tank 1 is cylindrical and has an effective volume of 9m 3 ~10m 3 , an aeration device 2 is provided at the bottom of the water tank 1;

[0063] S2, add 250g / L sodium hydroxide solution to obtain ferrous sulfate solution, obtain mixed ore pulp, adjust the mixed ore pulp pH to 7-8, continue aeration, then measure the mixed ore pulp pH every 10min-20min, qualitatively detect ferrous ions and ferric ions in the mixed ore pulp, according to the pH reduction, continue to add 250g / L sodium hydroxide solution to the mixed ore pulp, keep the mixed ore pulp pH at 7-8, aerate for 12h, cumulatively add 200L of sodium hydroxide solution, the pH slowly decreases after that, measure the mixed ore pulp pH every 1h-2h, qualitatively detect ferrous ions and ferric ions in the mixed ore pulp, according to the pH reduction, add 200L sodium hydroxide solution to the mixed ore pulp again in batches, keep the mixed ore pulp pH at 7-8, the total amount of sodium hydroxide solution added is 400mL, and ferrous ions and ferric ions are not detected after cumulative aeration for 24h to obtain ferrihydrite ore pulp;

[0064] Hydroxylamine hydrochloride and o-phenanthroline were used to qualitatively detect the presence of ferrous and ferric ions;

[0065] S3, start the chamber diaphragm filter press, set the feed pressure to 0.8MPa, feed delay to 1000s, press pressure to 1MPa, press delay to 1200s, feed and press the obtained ferrihydrite slurry, the total pressing time is 30min, and form ferrihydrite cake. The wet weight of the ferrihydrite cake is 180kg, and the powdered ferrihydrite obtained after drying and crushing is 100kg.

[0066] The wet weight of the ferrihydrite cake obtained in the parallel experiment ranged from 180kg to 200kg, and the powdered ferrihydrite obtained after drying and crushing ranged from 100kg to 120kg.

[0067] In this embodiment, the amount of water is increased. Calculated by mass ratio, the ratio of ferrous sulfate to water is 1:20, the ratio of sodium hydroxide to water is 1:50, the pH of the mixed slurry is maintained at 7-8, the total pressing time is 30 minutes, and the prepared ferrihydrite is reddish brown.

[0068] Comparative Example 1

[0069] The preparation method of ferrihydrite in this comparative example comprises the following steps:

[0070] Pump 4m3 of water into the aeration tank 1. 3 Clean water, turn on aeration device 2, aeration is carried out by a rotary blower, the fan pressure is 0.5kg / cm 2 , add 250kg of ferrous sulfate, aerate for 24h to obtain ore slurry;

[0071] The pH value was determined, and the presence of ferrous and ferric ions was qualitatively detected using hydroxylamine hydrochloride and o-phenanthroline;

[0072] Start the chamber diaphragm filter press, set the feed pressure to 0.8MPa, the feed delay to 1000s, the pressing pressure to 1MPa, the pressing delay to 1200s, feed and press the obtained slurry, the total pressing time is 30min, and form a ore cake.

[0073] In this comparative example, no sodium hydroxide is added, that is, the pH value is not maintained in the range of 7-8. The actual pH drops naturally from 4 to 1, and the ferrous ions and ferric ions cannot be completely precipitated. After the reaction is completed, ferrous ions and ferric ions can still be detected in the slurry. The mineral obtained by filter pressing is brown-green in color, which can be roughly judged to be ferrous hydroxide, non-hydraulic ferrite, because ferrous ions are difficult to be completely oxidized by air under acidic conditions.

[0074] In summary, the preparation method of ferrihydrite in the present application uses ferrous sulfate and sodium hydroxide as raw materials, and utilizes an aeration device and a chamber diaphragm filter press to obtain ferrihydrite, which has a simple process flow, low cost, and can be mass-produced. Ferrous sulfate, a by-product of a titanium dioxide plant, is used as a raw material to synthesize ferrihydrite, which solves the technical problems of high economic cost and heavy environmental burden of processing by-products, and realizes resource recycling.

[0075] The above-mentioned embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person skilled in the art, several modifications, improvements and substitutions can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the attached claims.

Claims

1. A method for preparing ferrihydrite, characterized in that: The following steps are involved: S1. Pump water into the device, add ferrous sulfate after aeration, continue aeration, and calculate by mass ratio, the ratio of ferrous sulfate to water is 1:16 to 20 to obtain a ferrous sulfate solution; S2. Add sodium hydroxide to the ferrous sulfate solution, the ratio of sodium hydroxide to water is 1:40-70 by mass, the pH is maintained at 7-8, and aeration is continued until no ferrous ions and ferric ions are detected, thereby obtaining the ferrihydrite.

2. The method for preparing ferrihydrite according to claim 1, characterized in that: The aeration time in step S1 is 30 minutes to 60 minutes; when no ferrous ions and ferric ions are detected in step S2, the cumulative aeration time is no more than 24 hours.

3. The method for preparing ferrihydrite according to claim 2, characterized in that: In the step S2, the ferrous ions, ferric ions and pH value are detected at target intervals; When the cumulative aeration time is ≤12h, the target interval time is 10min to 20min; When the cumulative aeration time is greater than 12 hours, the target interval time is 1 hour to 2 hours.

4. The method for preparing ferrihydrite according to claim 1, characterized in that: The equipment is a water tank with an aeration device at the bottom; the effective volume of the water tank is 9m 3 ~10m 3 .

5. The method for preparing ferrihydrite according to claim 4, characterized in that: The aeration device is a rotary blower; the pressure of the rotary blower is 0.1kg / cm 2 ~0.5kg / cm 2 .

6. A method for preparing ferrihydrite according to any one of claims 1 to 5, characterized in that: The method also includes the step of preparing the ferrihydrite into powder.

7. The method for preparing ferrihydrite according to claim 6, characterized in that: In the step S2, hydroxylamine hydrochloride and o-phenanthroline are used to qualitatively detect ferrous ions and ferric ions.

8. The method for preparing ferrihydrite according to claim 7, characterized in that: The ferrous sulfate is taken from the by-product of a titanium dioxide plant.

9. A ferrihydrite, characterized in that: Prepared according to the method according to any one of claims 1 to 8.

10. An application of ferrihydrite, characterized in that: The ferrihydrite described in claim 9 is applied to the preparation of environmental management materials.

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