A manganese dioxide-iron oxide composite material for removing arsenic from acidic wastewater and a preparation method thereof
By combining manganese dioxide nanotubes with ferric salts and methyl orange, a stable manganese dioxide-iron oxide composite material is formed, which solves the stability and porosity problems of iron-manganese binary oxide materials, and achieves efficient arsenic removal and low-cost large-scale production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YUNNAN YUNTIANHUA
- Filing Date
- 2024-08-05
- Publication Date
- 2026-06-26
AI Technical Summary
Existing iron-manganese binary oxide materials lack porous structures, have poor stability, are prone to aggregation, are difficult to mass-produce, and are costly, thus limiting their application in arsenic adsorption and removal.
Manganese dioxide nanotubes were mixed with ferric salts and methyl orange and calcined to form a manganese dioxide-iron oxide composite material. Methyl orange was used as a binder to stably load iron oxide on the surface of manganese dioxide nanotubes, forming a stable pore structure and improving the adsorption effect.
It achieves efficient removal of trivalent and pentavalent arsenic, simplifies the preparation process, facilitates large-scale promotion and transportation, reduces costs, and improves the stability and porosity of composite materials.
Abstract
Description
Technical Field
[0001] This invention relates to the field of chemical composite materials technology, and in particular to a manganese dioxide-iron oxide composite material for arsenic removal from acidic wastewater and its preparation method. Background Technology
[0002] Arsenic is a widely distributed toxic element, toxic and carcinogenic to humans and other organisms. Arsenic in water is mainly divided into As(III) and As(V). Because As(III) is much more toxic than As(V), and As(III) has higher solubility and mobility compared to As(V), As(III) is more difficult to remove from wastewater than As(V).
[0003] Common methods for removing arsenic from water include electrocoagulation sedimentation, coagulation sedimentation, ion exchange, adsorption, and biological methods. Among these, adsorption is widely used due to its simple operation, low cost, and variety of adsorbents. Iron oxides such as magnetite, hematite, and goethite have high affinity for arsenic and are frequently used in the remediation of arsenic pollution. However, iron oxides are far less effective at removing As(III) than As(V). Therefore, more and more researchers at home and abroad are trying to combine iron oxides with manganese oxides, which have strong oxidizing capabilities, to obtain iron-manganese binary oxides, hoping to achieve efficient removal of both As(III) and As(V). However, single iron-manganese binary oxide materials lack porous structures, have poor stability, and are prone to aggregation, which limits their application in the adsorption and removal of arsenic.
[0004] Patent CN17861619A and its invention, "MnO2 / GO@Fe2O3 Composite Aerogel and its Preparation Method and Application," describe its use for arsenic removal from wastewater. However, they fail to consider the high cost, limitations on large-scale promotion, and issues related to storage and transportation. Since it's used for wastewater treatment, the required quantity is substantial, and its preparation necessitates the introduction of components like graphene to enhance its arsenic removal capabilities. However, graphene is expensive, the performance of different batches of graphene products is unstable, and the synthesis of composite materials often employs hydrothermal methods with stringent reaction conditions, making large-scale production difficult.
[0005] This shows that the excessively high cost seriously affects its use, while the complex process and multiple steps greatly limit the possibility of large-scale application. In addition, it requires careful storage because it is easily damaged or crushed by external forces, which is not conducive to its use after long-distance transportation to its destination. These issues urgently need to be addressed. Summary of the Invention
[0006] The purpose of this invention is to provide a manganese dioxide-iron oxide composite material for arsenic removal from acidic wastewater and its preparation method, overcoming the problems of existing iron-manganese binary oxide materials lacking porous structure, having poor stability, being prone to aggregation, and being difficult to mass-produce.
[0007] To solve the above problems, the present invention employs the following technical means:
[0008] A method for preparing a manganese dioxide-iron oxide composite material for arsenic removal from acidic wastewater includes the following steps:
[0009] S1, Synthesis of manganese dioxide nanotubes;
[0010] S2. The manganese dioxide nanotubes are mixed with ferric salt and methyl orange to form a mixed solution, and then dried to obtain a mixed powder.
[0011] S3. The mixed powder is calcined to obtain the manganese dioxide-iron oxide composite material.
[0012] The purpose of S3 calcination is to remove the methyl orange between the iron oxide and manganese dioxide nanotubes. Ferric ions form iron oxide during calcination, and after the methyl orange is burned off, it is stably loaded onto the wall of the manganese dioxide nanotubes.
[0013] As a preferred technical solution, a composite material of ferric salt-methyl orange-manganese dioxide nanotubes is formed in the mixed solution of S2, and the ferric salt is oxidized to iron oxide in the subsequent calcination process of S3.
[0014] In this process, manganese dioxide nanotubes are mixed with ferric salt and methyl orange. During the mixing process, methyl orange acts as a bonding agent between the ferric salt and the surface of manganese dioxide nanotubes, connecting the ferric salt and manganese dioxide nanotubes to form a stable calcination precursor. The precursor is then dried and dehydrated at 70-80°C to form a mixed precursor powder, i.e., a mixed powder.
[0015] As a preferred technical solution, a composite material of ferric ions-methyl orange-manganese dioxide nanotubes is formed in the mixed solution of S2;
[0016] During this process, under the action of methyl orange, a composite material of ferric ions-methyl orange-manganese dioxide nanotubes is formed, forming a stable calcination precursor. It is then dried and dehydrated at 70-80°C to form a mixed precursor powder, i.e., mixed powder.
[0017] As a preferred technical solution, the trivalent iron salt is either ferric chloride or ferric nitrate.
[0018] As a preferred technical solution, the mass ratio of the manganese dioxide nanotubes, the ferric salt and the methyl orange is 30-60:3-5:1.
[0019] As a preferred technical solution, the stirring time of the mixed solution in S2 is 8 to 12 hours.
[0020] As a preferred technical solution, the calcination temperature of the mixed powder in step 3) is 600-650℃, and the calcination time is 8-12h.
[0021] Controlling the calcination temperature is crucial to ensuring the functionality of composite materials. When the calcination temperature is too low, methyl orange, acting as a binder between iron oxide and manganese dioxide nanotubes, cannot be removed. Consequently, the iron oxide and manganese dioxide nanotubes cannot achieve a stable load, resulting in insufficient iron oxide loading on the surface of the manganese dioxide nanotubes in the final composite material, thus affecting its functionality. Conversely, if the calcination temperature is too high, the tube structure of the manganese dioxide nanotubes will be destroyed, leading to tube collapse and reduced porosity of the finished composite material. Furthermore, significant damage to the tube structure of the manganese dioxide nanotubes can cause the composite material to easily agglomerate, severely reducing its functionality.
[0022] The present invention also discloses a manganese dioxide-iron oxide composite material, comprising manganese dioxide nanotubes, iron oxide and methyl orange;
[0023] The iron oxide is in situ loaded on the surface of the manganese dioxide nanotubes;
[0024] The methyl orange serves as a binder for the composite of the iron oxide and the manganese dioxide nanotubes.
[0025] The manganese dioxide / iron oxide composite material utilizes methyl orange as a linker between manganese dioxide nanotubes and iron oxide, allowing iron oxide to be better loaded onto the inner and outer walls of the manganese dioxide nanotubes. On one hand, manganese dioxide nanotubes can adsorb methyl orange; on the other hand, methyl orange can form a complex with ferric ions, thereby achieving iron oxide loading on the manganese dioxide nanotubes.
[0026] The present invention also provides a weakly acidic wastewater arsenic removal agent containing a manganese dioxide-iron oxide composite material.
[0027] Using methyl orange as a binder, iron oxide is in-situ loaded onto manganese dioxide nanotubes to form a manganese dioxide nanotube / iron oxide composite material. On the one hand, the large amount of iron oxide loaded on the manganese dioxide nanotubes provides excellent removal capacity for pentavalent arsenic. On the other hand, the strong oxidizing property of manganese dioxide is utilized to oxidize a large amount of trivalent arsenic in the wastewater to pentavalent arsenic, allowing the oxidized trivalent arsenic to be treated by iron oxide. Furthermore, the characteristics of manganese dioxide nanotubes are utilized, with iron oxide loaded on both the inner and outer walls of the nanotubes, increasing the reaction sites for the entire composite material to react with the wastewater. At the same time, the structural characteristics of the nanotubes themselves are utilized, leaving a large number of voids between the tubes when the composite material is stacked. The nanotubes themselves also have duct-like voids, thus giving the entire iron-manganese binary composite material good porosity and improving the adsorption effect. In addition, the stacking between the tubes effectively reduces the aggregation of the manganese dioxide / iron oxide composite material, improving the service life and reuse rate of the composite material. It can be used in the arsenic removal process of weakly acidic wastewater at a lower cost and higher efficiency.
[0028] As a preferred technical solution, it is used for arsenic removal in weakly acidic wastewater with a pH of 2-5. If the pH is too low, the acidity is too strong, which will cause the iron oxide to dissolve; if the pH is too high, the oxidizing power of manganese dioxide will be weakened, which is not conducive to arsenic removal.
[0029] The method for preparing a manganese dioxide-iron oxide composite material for arsenic removal from acidic wastewater includes the following steps: S1, synthesizing manganese dioxide nanotubes; S2, mixing the manganese dioxide nanotubes with ferric salt and methyl orange to form a mixed solution, and drying to obtain a mixed powder; S3, calcining the mixed powder to obtain the manganese dioxide-iron oxide composite material.
[0030] Advantages of this invention:
[0031] Based on methyl orange as a linker, ferric salts are directly loaded onto manganese dioxide nanotubes during the conversion of ferric salts to ferric oxide. This results in a high loading of ferric oxide onto both the inner and outer walls of the manganese dioxide nanotubes. Subsequent calcination further stabilizes the loading of ferric oxide onto the manganese dioxide nanotubes. Thus, a weakly acidic wastewater arsenic removal agent capable of simultaneously and efficiently removing both trivalent and pentavalent arsenic is obtained through a simple preparation process.
[0032] The preparation method of this invention is simple, easy to promote on a large scale, and convenient to transport. Detailed Implementation
[0033] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.
[0034] Example 1:
[0035] 1) Manganese dioxide nanotubes were synthesized according to the literature (Journal of Power Sources 2013, 241, 359-366). The specific literature is "Yao W, Zhou H, Lu Y. Synthesis and property of novel MnO2@polypyrrole coaxial nanotubes as electrode material for supercapacitors[J].Journal of Power Sources,2013,241(NOV.1):359-366.DOI:10.1016 / j.jpowsour.2013.04.142".
[0036] 2) Add manganese dioxide nanotubes to a solution containing ferric chloride and methyl orange, stir for 8 hours, and then dry the black turbid liquid in an oven. The mass ratio of manganese dioxide, ferric chloride and methyl orange is 30:5:1.
[0037] 3) The dried powder is heated and calcined at 600℃ for 10 hours to obtain manganese dioxide-iron oxide composite material.
[0038] 4) The pH of a 5 mg / L sodium arsenite solution was adjusted to 2 using 0.1 mol / L hydrochloric acid and 0.1 mol / L sodium hydroxide. 2 mg / mL of a manganese dioxide-iron oxide composite material was added and the solution was shaken at room temperature. The adsorbed solution was filtered through a 0.22 μm microfiltration membrane. The adsorbed amount of arsenic in the resulting supernatant was determined by ICP to be 8.1 mg / g. The adsorbed material was filtered out and desorbed using 1 mol / L NaOH as the eluent. This adsorption and desorption process was repeated five times, and the adsorption capacity was retained at 78.2%.
[0039] Example 2:
[0040] 1) Manganese dioxide nanotubes were synthesized according to the literature (Journal of Power Sources 2013, 241, 359-366).
[0041] 2) Add manganese dioxide nanotubes to a solution containing ferric nitrate and methyl orange, stir for 10 hours, and then dry the black turbid liquid in an oven. The mass ratio of manganese dioxide, ferric nitrate and methyl orange is 50:5:1.
[0042] 3) The dried powder was heated and calcined at 650℃ for 8 hours to obtain the manganese dioxide-iron oxide composite material.
[0043] 4) The pH of a 5 mg / L sodium arsenite solution was adjusted to 4 using 0.1 mol / L hydrochloric acid and 0.1 mol / L sodium hydroxide. 2 mg / mL of a manganese dioxide-iron oxide composite material was added and the solution was shaken at room temperature. The adsorbed solution was filtered through a 0.22 μm microfiltration membrane. The adsorbed arsenic content in the resulting supernatant was determined by ICP to be 9.6 mg / g. The adsorbed material was filtered and desorbed using 1 mol / L NaOH as the eluent. This adsorption and desorption process was repeated five times, and the adsorption capacity was retained at 76.8%.
[0044] Example 3:
[0045] 1) Manganese dioxide nanotubes were synthesized according to the literature (Journal of Power Sources 2013, 241, 359-366).
[0046] 2) Add manganese dioxide nanotubes to a solution containing ferric nitrate and methyl orange, stir for 12 hours, and then dry the black turbid liquid in an oven. The mass ratio of manganese dioxide, ferric nitrate and methyl orange is 50:4:1.
[0047] 3) The dried powder is heated and calcined at 600℃ for 12 hours to obtain manganese dioxide-iron oxide composite material.
[0048] 4) The pH of a 5 mg / L sodium arsenite solution was adjusted to 3 using 0.1 mol / L hydrochloric acid and 0.1 mol / L sodium hydroxide. 2 mg / mL of a manganese dioxide-iron oxide composite material was added and the solution was shaken at room temperature. The adsorbed solution was filtered through a 0.22 μm microfiltration membrane. The adsorbed amount of arsenic in the resulting supernatant was determined by ICP to be 9.2 mg / g. The adsorbed material was filtered out and desorbed using 1 mol / L NaOH as the eluent. This adsorption and desorption process was repeated five times, and the adsorption capacity was retained at 77.5%.
[0049] Example 4:
[0050] 1) Manganese dioxide nanotubes were synthesized according to the literature (Journal of Power Sources 2013, 241, 359-366).
[0051] 2) Add manganese dioxide nanotubes to a solution containing ferric chloride and methyl orange, stir for 10 hours, and then dry the black turbid liquid in an oven. The mass ratio of manganese dioxide, ferric chloride and methyl orange is 40:5:1.
[0052] 3) The dried powder is heated and calcined at 600℃ for 10 hours to obtain manganese dioxide-iron oxide composite material.
[0053] 4) The pH of a 5 mg / L sodium arsenite solution was adjusted to 5 using 0.1 mol / L hydrochloric acid and 0.1 mol / L sodium hydroxide. 2 mg / mL of a manganese dioxide-iron oxide composite material was added and the solution was shaken at room temperature. The adsorbed solution was filtered through a 0.22 μm microfiltration membrane, and the adsorbed arsenic content in the resulting supernatant was determined by ICP to be 8.6 mg / g. The adsorbed material was filtered out and desorbed using 1 mol / L NaOH as the eluent. This adsorption and desorption process was repeated five times, and the adsorption capacity was retained at 79.1%.
[0054] Comparative Example 1
[0055] 1) Manganese dioxide nanotubes were synthesized according to the literature (Journal of Power Sources 2013, 241, 359-366).
[0056] 2) Add manganese dioxide nanotubes to a solution containing ferric chloride, stir for 8 hours, and then dry the black turbid liquid in an oven. The mass ratio of manganese dioxide to ferric chloride is 30:1.
[0057] 3) The dried powder is heated and calcined at 600℃ for 10 hours to obtain manganese dioxide-iron oxide composite material.
[0058] 4) The pH of a 5 mg / mL sodium arsenite solution was adjusted to 2 using 0.1 mol / L hydrochloric acid and 0.1 mol / L sodium hydroxide. 2 mg / mL of a manganese dioxide-iron oxide composite material was added and the solution was shaken at room temperature. The adsorbed solution was filtered through a 0.22 μm microfiltration membrane. The adsorbed amount of arsenic in the resulting supernatant was determined by ICP to be 6.7 mg / g. The adsorbed material was filtered out and desorbed using 1 mol / L NaOH as the eluent. This adsorption and desorption process was repeated five times, and the adsorption capacity was retained at 75.9%.
[0059] Compared with Example 1, when manganese dioxide nanotubes were added to a solution containing ferric chloride, and methyl orange was not used as a binder for the composite of ferric oxide and manganese dioxide nanotubes, the manganese dioxide-ferric oxide composite material prepared under the same other preparation conditions showed a significant decrease in both the adsorption capacity for arsenic and the adsorption capacity after desorption.
[0060] Comparative Example 2
[0061] 1) Add commercially available manganese dioxide nanoparticles to a solution containing ferric chloride and methyl orange, stir for 8 hours, and then dry the black turbid liquid in an oven. The mass ratio of manganese dioxide, ferric chloride and methyl orange is 30:5:1.
[0062] 2) The dried powder was heated and calcined at 600℃ for 10 hours to obtain the manganese dioxide-iron oxide composite material.
[0063] 3) The pH of a 5 mg / mL sodium arsenite solution was adjusted to 2 using 0.1 mol / L hydrochloric acid and 0.1 mol / L sodium hydroxide. 2 mg / mL of a manganese dioxide-iron oxide composite material was added and the solution was shaken at room temperature. The adsorbed solution was filtered through a 0.22 μm microfiltration membrane. The adsorbed amount of arsenic in the resulting supernatant was determined by ICP to be 7.2 mg / g. The adsorbed material was filtered out and desorbed using 1 mol / L NaOH as the eluent. This adsorption and desorption process was repeated five times, and the adsorption capacity was retained at 74.8%.
[0064] Compared with Example 1, when commercially available manganese dioxide nanoparticles were used to replace the manganese dioxide nanotubes synthesized according to the literature (Journal of PowerSources 2013, 241, 359-366), and all other preparation conditions were the same, the manganese dioxide-iron oxide composite material showed a significant decrease in both the adsorption capacity for arsenic and the adsorption capacity after desorption.
[0065] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.
Claims
1. A method for preparing a manganese dioxide-iron oxide composite material for arsenic removal from acidic wastewater, characterized in that, Includes the following steps: S1, Synthesis of manganese dioxide nanotubes; S2. The manganese dioxide nanotubes are mixed with ferric salt and methyl orange to form a mixed solution, and then dried to obtain a mixed powder; the mass ratio of the manganese dioxide nanotubes, ferric salt and methyl orange is 30-60:3-5:
1. S3. The mixed powder is calcined to obtain a manganese dioxide-iron oxide composite material; the calcination temperature of the mixed powder is 600-650℃ and the calcination time is 8-12h.
2. The method for preparing a manganese dioxide-iron oxide composite material for arsenic removal from acidic wastewater as described in claim 1, characterized in that: The ferric salt is either ferric chloride or ferric nitrate.
3. The method for preparing a manganese dioxide-iron oxide composite material for arsenic removal from acidic wastewater as described in claim 1, characterized in that: The stirring time for the mixed solution in S2 is 8 to 12 hours.
4. A manganese dioxide-iron oxide composite material prepared by the method for preparing a manganese dioxide-iron oxide composite material for arsenic removal from acidic wastewater as described in any one of claims 1 to 3, characterized in that: The iron oxide is in situ loaded on the surface of the manganese dioxide nanotubes; The methyl orange serves as a binder for the composite of the iron oxide and the manganese dioxide nanotubes.
5. A weakly acidic wastewater arsenic removal agent, characterized in that: The composite material containing manganese dioxide-iron oxide as described in claim 4.
6. The weakly acidic wastewater arsenic removal agent as described in claim 5, characterized in that: It is used for arsenic removal in weakly acidic wastewater with a pH of 2 to 5.