Ferric salt modified myriophyllum spicatum biochar as well as preparation method and application thereof

Abstract

The invention discloses ferric salt modified myriophyllum verticillatum biochar and a preparation method and application thereof.The preparation method comprises the steps that S1, myriophyllum verticillatum is washed and soaked with distilled water, then dried, smashed and sieved, and myriophyllum verticillatum powder is obtained; s2, adding the myriophyllum spicatum powder obtained in the step S1 into a ferrous chloride solution, and heating in a water bath until gel is formed; s3, drying the gel obtained in the step S2 at a constant temperature to obtain dry gel; s4, pyrolyzing the xerogel obtained in the step S3 in an inert gas atmosphere to obtain a pyrolysis product; and S5, washing the pyrolysis product obtained in the step S4, drying, grinding and sieving to obtain the ferric salt modified myriophyllum spicatum biochar. Myriophyllum verticillatum is adopted as a raw material, gelatinization and pyrolysis are performed to obtain the biochar, the biochar is chemically modified by using a ferrous chloride solution to improve the adsorption characteristic so as to adsorb phosphate in a polluted water body, and the prepared biochar has magnetism and is beneficial to recycling.

Description

Technical Field

[0001] The invention belongs to the technical field of preparing biochar from waste biomass, and specifically relates to an iron salt-modified foxtail algae biochar and a preparation method and application thereof. Background Art

[0002] Phosphorus is a non-renewable resource that is essential for biological growth and agriculture. However, large amounts of phosphorus are discharged into the environment, resulting in a waste of this valuable resource. Excessive phosphorus content in water bodies can lead to eutrophication of water bodies, causing hypoxia in water bodies and posing a serious threat to aquatic ecosystems. Therefore, effective treatment of phosphorus in eutrophic water bodies is essential for phosphorus recovery and wastewater treatment. There are many methods for treating phosphorus in eutrophic water bodies, such as chemical precipitation, membrane treatment, crystallization, and advanced oxidation processes. However, these technologies have many disadvantages, such as complex procedures, high treatment costs, and high energy requirements. In contrast, adsorption methods have low operating costs and high treatment efficiency. Many studies have focused on using cheap materials (such as biomass or solid waste) and practical methods to solve the problem of water eutrophication.

[0003] Since the raw materials for preparing biochar, such as biomass, sludge, etc., are widely available, inexpensive, and contain rich pore structures. Therefore, biochar has become one of the common materials in the adsorption process. However, the biochar obtained by direct pyrolysis of biomass and other materials has a dense texture, a small specific surface area, a lack of adsorbable active sites, and a limited adsorption capacity for pollutants. Therefore, many scholars have improved the adsorption properties of biochar by modifying biochar. Chemical modification, impregnation and heat treatment are often used for biomass modification, giving biomass more adsorption functional groups, a larger specific surface area and a rich pore structure, thereby improving the adsorption of pollutants. For the modification of biochar, it is usually based on the characteristics of the pollutants. The adsorption of phosphates is more likely to use biochar modified with metal cations to form a coordination complex with phosphate. A large amount of literature has shown that calcium (Ca), iron (Fe), and lanthanum (La) can effectively lock and adsorb phosphates and have a strong affinity for phosphates.

[0004] As a common waste, the careless disposal of foxtail algae will cause environmental pollution. If the foxtail algae can be used to adsorb phosphates in polluted water, it will not only help solve the eutrophication problem of water bodies, but also have important significance for the transformation of waste into treasure.

[0005] Therefore, it is necessary to develop an iron salt-modified foxtail algae biochar to adsorb excessive phosphate in polluted water bodies, solve water eutrophication and effectively utilize fishery waste. Summary of the invention

[0006] The present invention aims to provide an iron salt modified foxtail algae biochar and a preparation method and application thereof, so as to prepare low-cost, environmentally friendly biochar with excellent adsorption performance for phosphate, realize water eutrophication control and effective utilization of fishery waste, and achieve the dual goals of environmental protection and resource recycling.

[0007] To achieve the above object, the present invention is implemented by the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing iron salt-modified foxtail algae biochar, the preparation method comprising the following steps:

[0009] S1, preparing foxtail algae powder;

[0010] S2, adding foxtail algae powder to ferrous chloride solution, heating and stirring until gel is formed;

[0011] S3, drying the gel obtained in step S2 to obtain a dry gel;

[0012] S4, pyrolyzing the dry gel obtained in step S3 under an inert gas atmosphere to obtain a pyrolysis product;

[0013] S5. Wash the pyrolysis product obtained in step S4, dry and grind it, and then sieve it to obtain iron salt modified foxtail algae biochar.

[0014] The present invention is a special process of preparing dry gel with foxtail algae and then pyrolyzing it, which realizes sol-gel conversion through the formation and polymerization of coordination compounds. This process first involves the coordination of a large number of small molecular metals to form a stable sol system (the organic components in foxtail algae react with ferrous chloride, and a large number of small molecular metals coordinate with organic functional groups in foxtail algae); as water molecules continue to disappear, these small molecular complexes are interconnected through carboxyl-metal ion bonds and hydrogen bonds to form a three-dimensional spatial gel network structure. The wet gel is dried at a constant temperature to become a dry gel, and the moisture is removed to solidify the structure. The dry gel is pyrolyzed under the protection of an inert gas (such as nitrogen), and the high temperature of 500-700°C causes the dry gel to undergo thermal decomposition and carbonization reaction to form biochar with a specific pore structure and chemical composition. The iron element is distributed in the biochar in a specific form to enhance its performance.

[0015] Biochar has a porous structure, and after modification, a granular structure (possibly iron oxide) appears on the surface, which increases the specific surface area and adsorption sites. These pores and surface structures can adsorb phosphate molecules in sewage onto the surface of biochar through physical effects such as van der Waals forces, achieving initial enrichment of phosphate. Iron salt modification causes the surface of biochar to carry active ingredients such as iron oxides, and iron has a strong affinity for phosphate. In sewage, iron ions can react chemically with phosphate to form coordination complexes. This chemical adsorption is more stable and stronger than physical adsorption, greatly improving the adsorption capacity and selectivity of biochar for phosphate.

[0016] As a further optimization scheme of the present invention, in step S1, the method for preparing foxtail algae powder includes: first washing and soaking the foxtail algae in distilled water for 2-6 hours, then drying at 75-105° C., crushing and passing through a 100-200 mesh sieve to obtain foxtail algae powder.

[0017] As a further optimization scheme of the present invention, in step S2, the concentration of the ferrous chloride solution is 0.01-1 mol / L, and the usage ratio of the foxtail algae powder to the ferrous chloride solution is 1 g: 10-100 mL.

[0018] As a further optimization scheme of the present invention, in step S2, the temperature of the water bath heating is 60-90°C, and the stirring speed is 100-200r / min.

[0019] As a further optimization scheme of the present invention, in step S3, the constant temperature drying temperature is 75-105°C.

[0020] As a further optimization scheme of the present invention, in step S4, the pyrolysis temperature is 500-700° C., and the pyrolysis time is 2-3 hours.

[0021] As a further optimization scheme of the present invention, in step S5, the pyrolysis product is washed with deionized water, the drying temperature is 75-105° C., and the sieve mesh number is 100-200 mesh.

[0022] In a second aspect, the present invention provides an iron salt-modified foxtail algae biochar, which is prepared by the above-mentioned method for preparing the iron salt-modified foxtail algae biochar.

[0023] In a third aspect, the present invention provides an application of iron salt-modified foxtail algae biochar for adsorbing phosphates in polluted water bodies.

[0024] As a further optimization scheme of the present invention, iron salt-modified foxtail algae biochar is added to the polluted water body, with an addition amount of 0.25 g / L to 2 g / L per 1 L of polluted water body, and stirred for 8 to 24 hours at room temperature to complete the treatment of the polluted water body; the original phosphate concentration of the polluted water body is 20 mg / L to 100 mg / L.

[0025] Compared with the prior art, the technical solution provided by the present invention has the following advantages and beneficial effects:

[0026] 1. Existing technologies for treating phosphorus in eutrophic water bodies, such as chemical precipitation, membrane treatment, crystallization and advanced oxidation processes, have problems of complex procedures, high processing costs and high energy requirements. At the same time, traditional biochar is obtained by direct pyrolysis of biomass, with dense texture, small specific surface area, few adsorption active sites and limited adsorption capacity. The present invention uses common waste Myriophyllum to prepare biochar, which is used for efficient and stable adsorption of phosphates in polluted water bodies, converting it from a pollution source into a valuable adsorption material, realizing the resource utilization of waste, solving the problem of eutrophication of water bodies, and reducing the environmental pollution caused by the arbitrary discarding of Myriophyllum, achieving the dual goals of environmental protection and resource recycling.

[0027] 2. The present invention first modifies the discarded foxtail algae with iron salts and prepares it into gel by hydrothermal method, and then prepares the gel prepared from the modified foxtail algae into magnetic biochar material by pyrolysis method. This process realizes sol-gel conversion through the formation and polymerization of coordination compounds, making the metal ion Fe 2+ The reaction process is stable and controllable, and metal Fe can be added as needed. 2+ , achieving uniform doping of metals and optimizing biochar performance. Chemical modification of iron salts can improve adsorption characteristics and thus be used to adsorb phosphates in polluted water. Compared with traditional biochar, the biochar prepared by the present invention has many particle structures (possibly iron oxides) on its surface, which increases the specific surface area and adsorption sites, and significantly improves the adsorption capacity of phosphates.

[0028] 3. Biochar has a porous structure. After modification, the particle structure on its surface further increases the specific surface area and adsorption sites, and can adsorb phosphate molecules through physical effects such as van der Waals forces to achieve initial enrichment. At the same time, iron salt modification makes the surface of biochar carry active ingredients such as iron oxides. Iron has a strong affinity for phosphates and can react chemically with phosphates in sewage to form coordination complexes. This chemical adsorption is more stable and firm than physical adsorption, which greatly improves the adsorption capacity and selectivity of biochar for phosphates, and effectively improves the removal effect of phosphates in polluted water.

[0029] 4. The modified biochar prepared by the present invention has magnetic properties, can be quickly separated and recovered by an external magnetic field, and can be reused multiple times. This not only reduces the consumption of biochar in the process of treating polluted water, but also reduces the treatment cost, which is an advantage that other adsorption materials in the prior art do not have.

[0030] 5. Using fishery waste Myriophyllum as the raw material for biochar has simple process, low cost and is environmentally friendly. Using waste Myriophyllum to synthesize phosphate adsorbent in water effectively improves the adsorption effect of phosphate in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a diagram showing the removal effect of phosphate adsorption by the modified foxtail algae biochar in Example 1.

[0032] Figure 2 This is a diagram showing the removal effect of phosphate adsorption by unmodified foxtail algae biochar in Comparative Example 1.

[0033] Figure 3 This is a diagram showing the removal effect of different concentrations of phosphate by the modified foxtail algae biochar of Example 1.

[0034] Figure 4 This is a scanning electron microscope image of the modified foxtail algae biochar in Example 1.

[0035] Figure 5 This is a scanning electron microscope image of the unmodified foxtail algae biochar in Comparative Example 1.

[0036] Figure 6 This is a rendering of the recycling capacity of the modified foxtail algae biochar of Example 1. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the technical solution of the present invention, the preferred implementation scheme of the present invention is described below in conjunction with specific embodiments, but it should not be understood as limiting the present invention and is only used as an example.

[0038] The experimental methods or test methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are obtained from conventional commercial channels or prepared by conventional methods unless otherwise specified.

[0039] Example 1

[0040] This embodiment provides a method for preparing iron salt modified foxtail algae biochar, and the specific steps are as follows:

[0041] S1, washing and soaking the foxtail algae with distilled water for 2 hours, drying at 75°C, crushing, and passing through a 100-mesh sieve to obtain foxtail algae powder;

[0042] S2, adding the Myriophyllum powder obtained in step S1 to a 1 mol / L ferrous chloride solution, with the Myriophyllum powder and the ferrous chloride solution in a ratio of 1 g:15 mL, placing the mixture in a water bath at 70° C. and stirring at 150 r / min until a gel is formed;

[0043] S3, placing the gel obtained in step S2 in a constant temperature box and drying at 105°C for 24 hours to obtain a dry gel;

[0044] S4, placing the dry gel obtained in step S3 in a tubular furnace, and pyrolyzing it at 500° C. for 2 h under a nitrogen atmosphere to obtain a pyrolysis product;

[0045] S5. Wash the pyrolysis product obtained in step S4 with deionized water, dry it at 105° C. for 12 h, grind it and pass it through a 100-mesh sieve to obtain iron salt-modified foxtail algae biochar.

[0046] Example 2

[0047] This embodiment provides a method for preparing iron salt modified foxtail algae biochar, and the specific steps are as follows:

[0048] S1, washing and soaking the foxtail algae with distilled water for 4 hours, drying at 85°C, crushing, and passing through a 150-mesh sieve to obtain foxtail algae powder;

[0049] S2, adding the Myriophyllum powder obtained in step S1 to 0.05 mol / L ferrous chloride solution, with the amount ratio of Myriophyllum to ferrous chloride solution being 1 g:85 mL, placing in a water bath and heating at 85° C. and stirring at 200 r / min until a gel is formed;

[0050] S3, placing the gel obtained in step S2 in a constant temperature box and drying at 100° C. for 24 h to obtain a dry gel;

[0051] S4, placing the dry gel obtained in step S3 in a tubular furnace, and pyrolyzing it at 700° C. for 2 h under a nitrogen atmosphere to obtain a pyrolysis product;

[0052] S5. Wash the pyrolysis product obtained in step S4 with deionized water, dry it at 100° C. for 12 h, grind it and pass it through a 150-mesh sieve to obtain iron salt-modified foxtail algae biochar.

[0053] Example 3

[0054] This embodiment provides a method for preparing iron salt modified foxtail algae biochar, and the specific steps are as follows:

[0055] S1, washing and soaking the foxtail algae with distilled water for 6 hours, drying at 100°C, crushing, and passing through a 200-mesh sieve to obtain foxtail algae powder;

[0056] S2, adding the Myriophyllum powder obtained in step S1 to 0.5 mol / L ferrous chloride solution, with the amount ratio of Myriophyllum to ferrous chloride solution being 1 g:40 mL, placing in a water bath and heating at 90° C. and stirring at 150 r / min until a gel is formed;

[0057] S3, placing the gel obtained in step S2 in a constant temperature box and drying at 105°C for 24 hours to obtain a dry gel;

[0058] S4, placing the dry gel obtained in step S3 in a tubular furnace, and pyrolyzing it at 600° C. for 2 h under a nitrogen atmosphere to obtain a pyrolysis product;

[0059] S5. Wash the pyrolysis product obtained in step S4 with deionized water, dry it at 105° C. for 12 h, grind it and pass it through a 100-mesh sieve to obtain iron salt-modified foxtail algae biochar.

[0060] Comparative Example

[0061] The foxtail algae powder obtained in step S1 is directly pyrolyzed in a tube furnace at 600° C. under a nitrogen atmosphere for 2 h to obtain unmodified foxtail algae biochar.

[0062] Performance Testing

[0063] The modified foxtail algae biochar of Example 1 was added to the polluted water (the phosphate concentration in the polluted water was 50 mg / L) at a dosage of 0.5 g / L, and stirred at room temperature for 24 hours to complete the treatment of the polluted water. The treated water was tested, and the adsorption amount mg / g refers to the adsorption amount of phosphorus, which is 24.91 mg / g, and the following is obtained: Figure 1 The diagram shows the removal effect of modified foxtail algae biochar on polluted water.

[0064] The comparative example was tested in the same manner as in Example 1, and the following results were obtained: Figure 2 The figure shows the removal effect of unmodified foxtail algae biochar on polluted water.

[0065] Depend on Figure 1 and Figure 2 From the comparison, it can be seen that the effect of phosphate removal by unmodified biochar is significantly inferior to that by modified biochar, and the adsorption of phosphate by modified biochar is significantly higher than that by unmodified biochar.

[0066] The modified foxtail algae biochar of Example 1 was added to the polluted water (the phosphate concentration in the polluted water was 25 mg / L, 50 mg / L, and 75 mg / L) at a dosage of 0.5 g / L. The water was stirred at room temperature for 12 h to complete the treatment of the polluted water. Figure 3 The figure shows the removal effect of phosphate by modified foxtail algae biochar.

[0067] from Figure 3 It can be seen that the removal of phosphate by biochar changes rapidly in the first 2 hours, and the adsorption rate slows down in the later period. As the phosphate concentration increases, the adsorption capacity of biochar also gradually increases.

[0068] Figure 4and Figure 5 To modify the morphology of biochar, Figure 4 and Figure 5 It can be seen that the surface of unmodified biochar is porous, and many granular structures appear on the surface of modified biochar. This may be due to the production of iron oxides on the surface of biochar. These changes are beneficial to the adsorption of pollutants.

[0069] from Figure 6 It can be seen that after three cycle experiments, the adsorption capacity of biochar can still reach 19.78 mg / g, which is 79% of the initial adsorption capacity, indicating that the biochar has a strong recyclability.

[0070] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing iron salt modified foxtail algae biochar, characterized in that: The preparation method comprises the following steps: S1, preparing foxtail algae powder; S2, adding foxtail algae powder to ferrous chloride solution, heating and stirring until gel is formed; S3, drying the gel obtained in step S2 to obtain a dry gel; S4, pyrolyzing the dry gel obtained in step S3 under an inert gas atmosphere to obtain a pyrolysis product; S5. Wash the pyrolysis product obtained in step S4, dry and grind it, and then sieve it to obtain iron salt modified foxtail algae biochar.

2. The method for preparing the iron salt modified foxtail algae biochar according to claim 1, characterized in that: In step S1, the method for preparing foxtail algae powder includes: washing and soaking the foxtail algae in distilled water for 2-6 hours, drying at 75-105° C., crushing and passing through a 100-200 mesh sieve to obtain foxtail algae powder.

3. The method for preparing the iron salt modified foxtail algae biochar according to claim 1, characterized in that: In step S2, the concentration of the ferrous chloride solution is 0.01-1 mol / L, and the usage ratio of the foxtail algae powder to the ferrous chloride solution is 1 g: 10-100 mL.

4. The method for preparing the iron salt modified foxtail algae biochar according to claim 1, characterized in that: In step S2, the water bath heating temperature is 60-90°C, and the stirring speed is 100-200 r / min.

5. The method for preparing the iron salt modified foxtail algae biochar according to claim 1, characterized in that: In step S3, the constant temperature drying temperature is 75-105°C.

6. The method for preparing the iron salt modified foxtail algae biochar according to claim 1, characterized in that: In step S4, the pyrolysis temperature is 500-700°C, and the pyrolysis time is 2-3h.

7. The method for preparing the iron salt modified foxtail algae biochar according to claim 1, characterized in that: In step S5, the pyrolysis product is washed with deionized water, dried at 75-105° C., and sieved with a mesh size of 100-200 mesh.

8. An iron salt modified foxtail algae biochar, characterized in that: The biochar is prepared by the method for preparing the iron salt-modified foxtail algae biochar according to any one of claims 1 to 7.

9. An application of the iron salt modified foxtail algae biochar as claimed in claim 8, characterized in that: Used to adsorb phosphates in polluted water.

10. The use according to claim 9, characterized in that: The iron salt-modified foxtail algae biochar is added to the polluted water body, with the dosage of 0.25g / L~2g / L per 1L of polluted water body. The treatment is stirred at room temperature for 8~24h to complete the treatment of the polluted water body. The original phosphate concentration of the polluted water body is 20mg / L~100mg / L.

Images