A ferric oxide flocculant, its preparation method and application

Abstract

This invention discloses a ferric oxide flocculant, its preparation method, and its application, relating to the field of ferric oxide preparation technology. The preparation method of the ferric oxide flocculant includes the following steps: mixing a calcium hydroxide solution, a solution containing ferrous ions, and iron powder to obtain a mixed solution; then, purging the mixed solution with air for 15–90 minutes to carry out an oxidation reaction, thereby obtaining the ferric oxide flocculant. The aeration rate when purging the mixed solution is 0.2–1.5 L / min. This invention provides oxygen through aeration and an alkaline environment through the addition of calcium hydroxide solution, eliminating the need for strict control of the oxygen content and pH value of the reaction solution, thus overcoming the problem of harsh reaction conditions in the conventional preparation and conversion of green rust into ferric oxide. Furthermore, the ferric oxide flocculant obtained by this invention retains the original loose structure, large specific surface area, and high flocculation activity of green rust, and can be used as a flocculant.

Description

Technical Field

[0001] This invention relates to the field of iron oxide preparation technology, and in particular to an iron oxide flocculant, its preparation method, and its application. Background Technology

[0002] Due to its small particle size, large specific surface area, and magnetic properties, ferric oxide flocculant has received widespread attention and application in the environmental protection industry, especially as a flocculant for water treatment. Currently, the magnetic flocculants being developed are basically formed by encapsulating or polymerizing traditional flocculants with the magnetic nanomaterial ferric oxide.

[0003] Green rust is an important metastable intermediate product generated during the formation and transformation of iron oxides. Due to its strong ability to adsorb certain heavy metal cations, organic anions, and inorganic ions, and its reducing properties comparable to zero-valent iron, green rust has significant research and application value in wastewater treatment and water remediation. However, because green rust is highly sensitive to the environment and easily oxidizes, its preparation and use generally require an oxygen-free or micro-oxygen environment, making direct large-scale application difficult. However, by preparing green rust and converting it to magnetite (Fe3O4) without altering the reaction conditions, the original porous structure and large specific surface area of ​​green rust can be preserved. More importantly, after conversion to magnetite, it remains stable under normal temperature and pressure for a long period and can be recycled and reused using its magnetic properties, thus greatly expanding its application scope and fields.

[0004] Currently, the preparation of ferric oxide (Fe3O4) via the conversion of green rust generally involves two steps. First, green rust is prepared using a co-precipitation method, oxidation method, or a ferrous / ferrous composite system. Then, the green rust is converted to ferric oxide via a water bath heating method, pH adjustment with alkali, or slow oxidation under a micro-oxygen environment. The co-precipitation, oxidation, or ferrous / ferrous composite system methods require strict control of the anaerobic or micro-oxygen environment, or precise control of the reaction pH. Therefore, the preparation process is cumbersome, and the reaction conditions are harsh. Furthermore, when green rust is converted to ferric oxide, the changed reaction conditions cause the generated ferric oxide to easily agglomerate, failing to maintain the original loose structure and high flocculation activity of the green rust. Therefore, conventional methods for preparing and converting ferric oxide from green rust suffer from harsh reaction conditions and low flocculation activity in the resulting ferric oxide. Summary of the Invention

[0005] The main objective of this invention is to provide a ferric oxide flocculant, its preparation method, and its application, aiming to solve the problems of harsh reaction conditions and low flocculant activity of the conventional method of preparing and converting ferric oxide from green rust.

[0006] To achieve the above objectives, the present invention provides a method for preparing a ferric oxide flocculant, comprising the following steps:

[0007] A calcium hydroxide solution, a solution containing ferrous ions, and iron powder are mixed to obtain a mixture. Air is then introduced into the mixture for 15–90 minutes to carry out an oxidation reaction, resulting in a ferric oxide flocculant.

[0008] The aeration rate when introducing air into the mixture is 0.2 to 1.5 L / min.

[0009] Optionally, the solution containing ferrous ions includes at least one of ferrous chloride tetrahydrate solution and ferrous sulfate heptahydrate solution.

[0010] Optionally, the concentration of ferrous ions in the mixture is 0.01–0.06 mol / L.

[0011] Optionally, when the calcium hydroxide solution is a saturated calcium hydroxide solution, the amount of the saturated calcium hydroxide solution added is 40% to 90% of the total volume of the mixture.

[0012] Optionally, the mass of the iron powder is 1% to 5% of the total mass of the mixture.

[0013] Optionally, the step of mixing calcium hydroxide solution, a solution containing ferrous ions, and iron powder to obtain a mixed solution, and then introducing air into the mixed solution for 15-90 minutes to carry out an oxidation reaction to obtain ferric oxide flocculant includes:

[0014] A calcium hydroxide solution, a solution containing ferrous ions, and iron powder are mixed to obtain a mixture. Air is then introduced into the mixture for 15–90 minutes to carry out an oxidation reaction, resulting in a mixture containing black suspended flocs.

[0015] Centrifugation of the mixture containing black suspended flocs yields ferric oxide flocculant.

[0016] Optionally, in the step of centrifuging the mixture containing black suspended flocs to obtain ferric oxide flocculant, the centrifugation time is 5-10 min; and / or,

[0017] The centrifugation speed is 1000-2000 r / min.

[0018] This invention provides a ferric oxide flocculant, which includes a ferric oxide flocculant prepared according to the preparation method of the ferric oxide flocculant.

[0019] This invention provides an application of the aforementioned ferric oxide flocculant in the removal of organic matter.

[0020] Optionally, the organic compound includes at least one of humic acid and furfural.

[0021] The beneficial effects of this invention are as follows:

[0022] (1) The method for preparing ferric oxide flocculant of the present invention uses calcium hydroxide solution to provide a weakly alkaline environment; air provides oxygen and carbon dioxide, and carbon dioxide generates carbonate ions under alkaline conditions; iron powder is used to maintain a micro-oxygen environment in the solution and form a "zero-valent iron / divalent iron" composite system with ferrous ions. Therefore, under micro-oxygen and weakly alkaline conditions, ferrous iron, ferric iron, carbonate ions, and anions introduced by the added ferrous salt react to first form green rust. When air is continuously introduced, the green rust slowly oxidizes to form ferric oxide. The present invention uses aeration to provide oxygen to the reaction solution and iron powder to maintain micro-oxygen conditions in the solution, and adds calcium hydroxide solution to provide the alkaline environment required for the reaction. It does not require strict control of dissolved oxygen content in the reaction solution, nor does it require the addition of sodium hydroxide alkaline solution to precisely control the reaction pH value, thus overcoming the problem of harsh reaction conditions in the conventional conversion of green rust to ferric oxide.

[0023] (2) The method for preparing the iron oxide flocculant provided by the present invention first forms green rust, and then directly oxidizes the green rust into iron oxide without changing the reaction conditions. The iron oxide obtained retains the original loose structure, large specific surface area and high flocculation activity of the green rust. Therefore, the iron oxide obtained has high flocculation activity and can be used as a flocculant without the need to mix it with traditional flocculants. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0025] Figure 1 This is the XRD diffraction pattern of the iron oxide flocculant and magnetite (74-748Magnetite) in Example 1 of this invention;

[0026] Figure 2 This is a scanning electron microscope (SEM) image of the iron oxide flocculant of Example 1 of the present invention.

[0027] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, or solution B, or a solution where both A and B are satisfied simultaneously. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Ferric oxide (Fe3O4) flocculants have gained widespread attention and application in the environmental protection industry, particularly as flocculants for water treatment, due to their small particle size, large specific surface area, and magnetic properties. Currently, most magnetic flocculants are formed by encapsulating or polymerizing traditional flocculants with the magnetic nanomaterial ferric oxide. Common preparation methods for ferric oxide include co-precipitation, hydrothermal methods, sol-gel methods, solvothermal methods, and high-temperature pyrolysis methods. However, these methods still suffer from problems such as harsh reaction conditions and easy agglomeration, which have not been well resolved.

[0030] Green rust is an important metastable intermediate product generated during the formation and transformation of iron oxides. Due to its strong ability to adsorb certain heavy metal cations, organic anions, and inorganic ions, and its reducing properties comparable to zero-valent iron, green rust has significant research and application value in wastewater treatment and water remediation. Iron(III) oxide, prepared from green rust and converted without altering the reaction conditions, retains the original loose structure and high flocculation activity of green rust.

[0031] Currently, the preparation of ferric oxide (Fe3O4) via the conversion of green rust generally involves two steps. First, green rust is prepared using a co-precipitation method, oxidation method, or a ferrous / ferrous composite system. Then, the green rust is converted into ferric oxide through a water bath heating method, pH adjustment with alkali, or slow oxidation under a micro-oxygen environment. The preparation of green rust using co-precipitation, oxidation, or ferrous / ferrous composite systems requires strict control of the anaerobic or micro-oxygen environment, or precise control of the reaction pH. Therefore, the preparation process is cumbersome, the reaction conditions are harsh, and the converted ferric oxide tends to agglomerate due to the change in reaction conditions, failing to maintain the original loose structure and high flocculation activity of the green rust.

[0032] Therefore, the conventional method of preparing and converting iron oxide from green rust has the problems of harsh reaction conditions and low flocculation activity of the obtained iron oxide.

[0033] In view of this, the present invention provides a method for preparing a ferric oxide flocculant, comprising the following steps:

[0034] A calcium hydroxide solution, a solution containing ferrous ions, and iron powder are mixed to obtain a mixture. Air is then introduced into the mixture for 15–90 minutes to carry out an oxidation reaction, resulting in a ferric oxide flocculant.

[0035] The aeration rate when introducing air into the mixture is 0.2 to 1.5 L / min.

[0036] It should be noted that the method for preparing ferric oxide flocculant of this invention is carried out in an open environment at normal temperature and pressure. All reagents are of analytical grade, and the experimental water is ordinary distilled water. Normal temperature refers to a temperature of 5–30°C, and normal pressure refers to a pressure of 65.0–100.5 kPa.

[0037] In the technical solution of this invention, calcium hydroxide solution provides hydroxide ions (OH-). - The system can regulate the alkaline environment; the introduction of air provides carbon dioxide and oxygen. Carbon dioxide reacts with water under alkaline conditions to form carbonate ions, and oxygen dissolves in the solution to form dissolved oxygen. The added iron powder is zero-valent iron (ZVFe), which reacts with dissolved oxygen in the solution to generate ferrous iron (Fe2+), ferric iron (Fe3+), and OH-. The presence of ZVFe has three main functions: 1) It helps maintain a weakly alkaline buffer environment; 2) It continuously replenishes the system with ferrous and fecal iron (Fe2+) ions; 3) The iron powder reacts promptly with dissolved oxygen in the water and oxygen introduced from the air, ensuring the mixture always maintains a micro-oxygen environment. Furthermore, ZVFe forms a "ZVFe / Fe2+" composite system with ferrous ions. The catalytic effect of ferrous iron (Fe2+) ensures that ZVFe remains reactive and does not become passivated. Therefore, under micro-oxygen and weakly alkaline conditions, ferrous iron (Fe2+), ferric iron (Fe3+), carbonate ions, and anions introduced by the added ferrous salt react to form green rust. When air continues to be introduced, the green rust slowly oxidizes to form magnetite (Fe3O4).

[0038] The method for preparing ferric oxide flocculant according to this invention does not require precise control of oxygen supply conditions or control and adjustment of the reaction pH value. It has the advantages of relaxed reaction conditions, simple operation, and low reaction cost. In the technical solution of this invention, the reaction time is greatly shortened as the amount of air introduced increases. The aeration rate when introducing air into the mixture is set to 0.2-1.5 L / min, which can avoid oxidizing green rust into goethite or ferriferrite, thus preventing the yield of ferric oxide.

[0039] This invention prepares green rust and converts it into iron oxide (Fe3O4) without changing the reaction conditions. The obtained iron oxide retains the original loose structure, large specific surface area and high flocculation activity of the green rust. Therefore, the obtained iron oxide flocculant has high flocculation activity and can be used as a flocculant without the need to mix it with traditional flocculants.

[0040] In any embodiment of the present invention, the solution containing ferrous ions includes at least one of ferrous chloride tetrahydrate solution and ferrous sulfate heptahydrate solution.

[0041] In any embodiment of the present invention, the concentration of ferrous ions in the mixture is 0.01 to 0.06 mol / L.

[0042] In any embodiment of the present invention, when the calcium hydroxide solution is a saturated calcium hydroxide solution, the amount of the saturated calcium hydroxide solution added is 40% to 90% of the total volume of the mixture.

[0043] In any embodiment of the present invention, the mass of the iron powder is 1% to 5% of the total mass of the mixture. Increasing the amount of iron powder added helps to shorten the reaction time.

[0044] In any embodiment of the present invention, in the step of mixing calcium hydroxide solution, a solution containing ferrous ions, and iron powder to obtain a mixed solution, and then introducing air into the mixed solution for 15 to 90 minutes to carry out an oxidation reaction to obtain ferric oxide flocculant, the oxidation reaction is carried out by placing the reaction solution in a magnetic stirrer and stirring at a speed of 50 to 150 r / min.

[0045] In any embodiment of the present invention, the step of mixing calcium hydroxide solution, a solution containing ferrous ions, and iron powder to obtain a mixed solution, and then introducing air into the mixed solution for 15-90 minutes to carry out an oxidation reaction to obtain ferric oxide flocculant includes:

[0046] A calcium hydroxide solution, a solution containing ferrous ions, and iron powder are mixed to obtain a mixture. Air is then introduced into the mixture for 15–90 minutes to carry out an oxidation reaction, resulting in a mixture containing black suspended flocs.

[0047] Centrifugation of the mixture containing black suspended flocs yields ferric oxide flocculant.

[0048] A calcium hydroxide solution and a ferrous salt solution are mixed, and then an appropriate amount of reduced iron powder is added to the mixture to obtain a solution. The solution is stirred in a magnetic stirrer and aerated with compressed air. After 5-10 minutes of aeration, dark green suspended flocs are observed to form. Further aeration causes the dark green flocs to transform into glossy black flocs. The resulting flocs are centrifuged, and the supernatant is discarded. The resulting bottom precipitate is the iron(III) oxide flocculant. In this invention, after aeration, carbon dioxide in the air generates carbonate ions under alkaline conditions, providing carbonate for the formation of green rust. Under micro-oxygen and weakly alkaline conditions, ferrous iron, ferric iron, carbonate, and the anions introduced by the added ferrous salt react to initially form green rust. At this point, dark green suspended flocs appear in the solution. With continued aeration, the green rust slowly oxidizes, and the dark green suspended flocs transform into black suspended flocs, forming the iron(III) oxide flocculant.

[0049] In any embodiment of the present invention, in the step of centrifuging the mixture containing black suspended flocs to obtain ferric oxide flocculant, the centrifugation time is 5 to 10 minutes.

[0050] In any embodiment of the present invention, the rotational speed during centrifugation is 1000 to 2000 r / min.

[0051] This invention provides a ferric oxide flocculant, which includes ferric oxide flocculant prepared by the method described above.

[0052] This invention provides an application of the aforementioned ferric oxide flocculant in the removal of organic matter.

[0053] In any embodiment of the present invention, the organic compound includes at least one of humic acid and furfural.

[0054] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0055] Example 1

[0056] A method for preparing a ferric oxide flocculant, comprising the following steps:

[0057] (1) Add 45 mL of saturated Ca(OH)2 solution (the amount of saturated Ca(OH)2 solution added is 90% of the total volume of the mixture) and 5 mL of FeCl2 solution (the concentration of ferrous ions in the mixture is 0.035 mol / L) to a 100 mL beaker, and finally add 2.0 g of reduced iron powder (the mass percentage of iron powder is 4%) to obtain a total volume of 50 mL of the mixture.

[0058] (2) The mixture was magnetically stirred and compressed air was introduced. The magnetic speed was 100 r / min, the compressed air flow rate was 0.5 L / min, and the air introduction time was 60 min, resulting in a mixture containing black suspended flocs.

[0059] (3) Centrifuge the mixture containing black suspended flocs to obtain iron(III) oxide. The centrifugation time is 5 min and the centrifugation speed is 1500 r / min.

[0060] Results: After step (2) began, dark green flocs were observed to slowly appear in the mixture. After about 15 minutes, the dark green flocs gradually changed from dark green to black suspended flocs. As the reaction time increased, the production of black suspended flocs increased, and the beaker wall was covered with a black film with a metallic luster. The black suspended flocs were not oxidized by air and remained black after being placed in an open environment for 2 hours. The mixture containing black suspended flocs was centrifuged, and the mass of the solids after centrifugation was 0.74 g.

[0061] Example 2

[0062] This embodiment was prepared according to a similar method and conditions as in Example 1. The difference is that in step (1), the amount of saturated Ca(OH)2 solution added is 40% of the total volume of the mixture, the concentration of ferrous ions in the mixture is 0.01 mol / L, and the total volume of the mixture is 50 mL by adding distilled water, and the mass percentage of iron powder is 1%; in step (2), the amount of compressed air introduced is 0.2 L / min, and the air introduction time is 90 min.

[0063] Results: The amount of flocs produced was relatively small. When the mixture containing black suspended flocs was centrifuged, the mass of solids after centrifugation was 0.31g, indicating that even with an increase in reaction time, the amount of product generated was still small when the amount of each reactant was reduced.

[0064] Example 3

[0065] This embodiment is prepared according to a similar method and conditions as in Example 1, except that the mass percentage of iron powder in step (1) is 5%; and the compressed air flow rate in step (2) is 1.5 L / min, and the air flow time is 15 min.

[0066] Results: The mixture containing black suspended flocs was centrifuged, and the mass of the solids after centrifugation was 0.67 g. This indicates that increasing the amount of iron powder added and the aeration rate can significantly shorten the reaction time.

[0067] Example 4

[0068] This embodiment was prepared according to a similar method and conditions as in Example 1, except that in step (1), the concentration of ferrous ions in the mixture was 0.06 mol / L and the mass percentage of iron powder was 3%; in step (2), the compressed air flow rate was 0.8 L / min and the air flow time was 45 min.

[0069] Results: The mixture containing black suspended flocs was centrifuged, and the mass of the solids after centrifugation was 1.05 g. This indicates that increasing the amount of ferrous iron added can significantly increase the product yield.

[0070] Example 5

[0071] This embodiment was prepared according to a similar method and conditions as in Example 1, except that in step (1), the amount of saturated Ca(OH)2 solution added was 60% of the total volume of the mixture, and distilled water was added to make the total volume of the mixture 50 mL, and the mass percentage of iron powder was 3%.

[0072] Results: The mixture containing black suspended flocs was centrifuged, and the mass of solids after centrifugation was 0.65 g. This indicates that reducing the amount of saturated Ca(OH)₂ solution added has little effect on the amount of product formed.

[0073] Example 6

[0074] This embodiment was prepared according to a similar method and conditions as in Example 1, except that the FeCl2 solution in step (1) was replaced by the FeSO4 solution (the concentration of ferrous ions in the mixture was 0.035 mol / L).

[0075] Results: The reaction phenomenon was basically the same as in Example 1, but the amount of floc produced was significantly greater than that in Example 1. The amount of solid matter after centrifugation was 1.69 g, and the supernatant after centrifugation was clearer and more transparent than that in Example 1.

[0076] Example 7

[0077] Application of a ferric oxide flocculant in the removal of humic acid:

[0078] 0.74g of the iron oxide flocculant from Example 1 was added to 50mL of a humic acid solution with a concentration of 1340.0mg / L. After shaking on a rotating shaker for 30min, the mixture was centrifuged and the concentration of humic acid in the supernatant was measured to be 130.0mg / L. The humic acid removal rate was as high as 90.3%, and the adsorption capacity of the prepared iron oxide flocculant for humic acid was 81.8mg / g.

[0079] The removal rate of humic acid is calculated as follows: (mass of humic acid before adsorption - mass of humic acid after adsorption) / (mass of humic acid before adsorption) × 100%.

[0080] Example 8

[0081] Application of a ferric oxide flocculant in the removal of furfural:

[0082] 0.74 g of the iron oxide flocculant from Example 1 was added to 100 mL of a furfural solution with a concentration of 1000.0 mg / L. After shaking on a rotating shaker for 30 min, the mixture was centrifuged and the concentration of furfural in the supernatant was measured to be 83.6 mg / L. The furfural removal rate reached 91.6%, and the adsorption capacity of the prepared iron oxide flocculant for furfural was 123.8 mg / g.

[0083] The removal rate of furfural is calculated as follows: (mass of furfural before adsorption - mass of furfural after adsorption) / (mass of furfural before adsorption) × 100%.

[0084] Table 1 Parameters of Examples 1-6

[0085]

[0086] Note: In Examples 1-5, ferrous ions were provided by FeCl2, and in Example 6, ferrous ions were provided by FeSO4.

[0087] Comparative Example 1

[0088] Compared with Example 1, distilled water was used instead of saturated calcium hydroxide solution in step (1), and everything else was the same as in Example 1.

[0089] Results: No obvious changes were observed in the solution after the reaction; no dark green flocs appeared, and no black flocs were formed. This is because no saturated calcium hydroxide solution was added to the reaction solution, which could not provide a weakly alkaline environment, preventing the reaction from producing green rust or iron(III) oxide, and therefore, iron(III) oxide flocculant could not be obtained.

[0090] Comparative Example 2

[0091] Compared with Example 1, no iron powder is added in step (1), but everything else is the same as in Example 1.

[0092] Results: A small amount of grayish-white flocs were observed after the reaction began. As the reaction proceeded, the final flocs turned yellowish-brown. The grayish-white flocs were a mixture of a small amount of dark green flocs and white ferrous hydroxide. As the reaction progressed, the green rust was gradually over-oxidized into yellow goethite or ferrihydrite, while the ferrous hydroxide was gradually converted into yellow ferric hydroxide, resulting in the final flocs being yellowish-brown and making it impossible to obtain ferric oxide flocculant.

[0093] Comparative Example 3

[0094] Compared with Example 1, no air is introduced in step (2), otherwise it is the same as Example 1.

[0095] Results: Dark green flocs were observed, but as the reaction proceeded, yellowish-brown flocs appeared on the surface of the dark green flocs, while the interior remained dark green flocs, unable to transform into black flocs. This is because without air circulation, a micro-oxygen environment could not be provided, and the green rust could not be further oxidized to iron(III) oxide, thus iron(III) oxide flocculant could not be obtained.

[0096] Comparative Example 4

[0097] Compared with Example 1, the aeration rate of air introduced in step (2) is 3.0 L / min, and the rest is the same as in Example 1.

[0098] Results: It was observed that the dark green flocs gradually transformed into yellowish-brown flocs. This was because the aeration was too high, and the green rust was oxidized into goethite or ferrimagnesia, so it was impossible to obtain ferric oxide flocculant.

[0099] Performance testing

[0100] The XRD pattern of the iron(III) oxide prepared in Example 1 was obtained by X-ray diffraction, and the results are as follows: Figure 1 As shown. Figure 1 This is the XRD diffraction pattern of the iron(III) oxide flocculant and magnetite (74-748) from Example 1. See also... Figure 1 The XRD pattern obtained in Example 1 is highly consistent with the peaks of the standard magnetite pattern (74-748), indicating that iron(III) oxide was formed.

[0101] The morphology of the iron oxide flocculant in Example 1 was characterized using scanning electron microscopy. The results are as follows: Figure 2 As shown. Figure 2 This is a SEM image of the iron oxide flocculant from Example 1, wherein... Figure 2 Image (a) is a scanning electron microscope (SEM) image (10kx magnification) of the iron oxide flocculant from Example 1. Figure 2 Image (b) is a scanning electron microscope (SEM) image (5kx magnification) of the iron oxide flocculant from Example 1. Figure 2 It can be seen that the prepared ferric oxide flocculant has a loose structure and typical flocculant characteristics, indicating that the prepared ferric oxide flocculant can be used as a flocculant.

[0102] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A method for preparing a ferric oxide flocculant, characterized in that, Includes the following steps: A calcium hydroxide solution, a solution containing ferrous ions, and iron powder are mixed to obtain a mixture. Air is then introduced into the mixture for 15-90 minutes to carry out an oxidation reaction, resulting in a ferric oxide flocculant. The aeration rate when introducing air into the mixture is 0.2~1.5L / min, the ferrous ion concentration in the mixture is 0.01~0.06mol / L, the mass of the iron powder is 1%~5% of the total mass of the mixture, the calcium hydroxide solution is a saturated calcium hydroxide solution, and the amount of the saturated calcium hydroxide solution added is 40%~90% of the total volume of the mixture.

2. The method for preparing the ferric oxide flocculant as described in claim 1, characterized in that, The solution containing ferrous ions includes at least one of ferrous chloride tetrahydrate solution and ferrous sulfate heptahydrate solution.

3. The method for preparing the ferric oxide flocculant as described in claim 1, characterized in that, The step of mixing calcium hydroxide solution, a solution containing ferrous ions, and iron powder to obtain a mixed solution, and then introducing air into the mixed solution for 15-90 minutes to carry out an oxidation reaction to obtain ferric oxide flocculant includes: A calcium hydroxide solution, a solution containing ferrous ions, and iron powder are mixed to obtain a mixture. Air is then introduced into the mixture for 15-90 minutes to carry out an oxidation reaction, resulting in a mixture containing black suspended flocs. Centrifugation of the mixture containing black suspended flocs yields ferric oxide flocculant.

4. The method for preparing the ferric oxide flocculant as described in claim 3, characterized in that, In the step of centrifuging the mixture containing black suspended flocs to obtain ferric oxide flocculant, the centrifugation time is 5-10 min; and / or, The centrifugation speed is 1000~2000 r / min.

5. A ferric oxide flocculant, characterized in that, The ferric oxide flocculant includes the ferric oxide flocculant prepared by the preparation method according to any one of claims 1-4.

6. The application of the ferric oxide flocculant as described in claim 5 in the removal of organic matter.

7. The application as described in claim 6, characterized in that, The organic matter includes at least one of humic acid and furfural.

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