Application of iron-manganese-based composite microalgae biochar material as phosphorus removal adsorbent in treatment of phosphorus-containing wastewater

Abstract

The application discloses application of an iron-manganese-based composite microalgae biochar material as a phosphorus removal adsorbent in treatment of phosphorus-containing wastewater, and a preparation method of the iron-manganese-based composite microalgae biochar material is as follows: Chlorella pyrenoidosa powder is immersed in a mixed solution of ferric chloride, manganese sulfate and EDTA, and then dried, ground and pyrolyzed to obtain the iron-manganese-based composite microalgae biochar material. The biochar has a large specific surface area, is rich in oxygen-containing functional groups and has many adsorption sites, the addition of ferric chloride makes the biochar magnetic and easy to recover, the addition of manganese sulfate increases the specific surface area and oxygen-containing functional groups of the biochar, the biochar structure is a flaky accumulated aggregate, and the biochar has strong adsorption capacity and can be applied to treatment of phosphorus-containing polluted water bodies. The addition of EDTA makes the iron and manganese better loaded on the microalgae, and can make the biochar produce specific chemical adsorption with phosphate, and further improves the adsorption performance of the material, and provides a new way and thought for removal of phosphate in an aquatic environment and recycling of harmful algae.

Description

Technical fields:

[0001] This invention relates to the fields of solid waste resource utilization and phosphorus-containing wastewater treatment, specifically to the application of iron-manganese-based composite microalgae biochar material as a phosphorus removal adsorbent in phosphorus-containing wastewater treatment. Background technology:

[0002] Phosphorus is an essential element for the growth of aquatic organisms. However, excessive phosphorus input can lead to eutrophication, accompanied by excessive algal growth. These algal blooms are characterized by their rapid growth and wide adaptability, releasing algal toxins that not only severely damage and harm the aquatic ecosystem but also affect human production activities and health. Therefore, finding an effective method to remove phosphate pollution from water bodies and to recycle harmful algae has become a global concern.

[0003] Currently, commonly used phosphorus removal technologies include chemical precipitation, biological treatment, membrane separation, and adsorption. Among these, adsorption has attracted more attention due to its high efficiency, simple operation, low cost, and few byproducts. Therefore, seeking low-cost, high-performance adsorbents for water pollution removal has significant application prospects. Among numerous adsorbents, biochar, due to its relatively large specific surface area and abundant oxygen-containing groups (such as hydroxyl and carboxyl groups), exhibits good affinity for heavy metals and anions, and is therefore widely used in research. Raw materials for biochar preparation include straw, sludge, sawdust, algae, and animal excrement. Algae, in particular, are a high-quality biomass resource with rapid reproduction and large biomass; using algae as a biochar raw material can provide a new approach for the recycling and utilization of harmful algae. Summary of the Invention:

[0004] This invention provides the application of iron-manganese-based composite microalgae biochar material as a phosphorus adsorbent in the treatment of phosphorus-containing wastewater. Based on the modification of biochar with iron and manganese elements, ethylenediaminetetraacetic acid (EDTA) is introduced. The resulting iron-manganese-based composite microalgae biochar material has a large specific surface area, rich oxygen-containing functional groups, and strong adsorption capacity for phosphates, providing a new approach for the removal of phosphates and the recycling of harmful algae in aquatic environments.

[0005] This invention is achieved through the following technical solutions:

[0006] The application of iron-manganese-based composite microalgae biochar material as a phosphorus removal adsorbent in the treatment of phosphorus-containing wastewater. The iron-manganese-based composite microalgae biochar material is a microalgae biochar loaded with iron and manganese, mainly prepared from ferric chloride, manganese sulfate, Chlorella, and EDTA as raw materials. Its preparation method includes the following steps:

[0007] 1) Chlorella powder is mixed with ferric chloride, manganese sulfate and EDTA for impregnation. After solid-liquid separation, drying and grinding, a pretreated algae powder mixture is obtained.

[0008] 2) The pretreated algal powder mixture is pyrolyzed at a temperature of 500-800℃ and dried to obtain iron-manganese based composite microalgae biochar.

[0009] Preferably, in step 1), the mass ratio of Chlorella:ferric chloride:manganese sulfate is 1:0.5-1.25:0.5-1.25, more preferably 1:1-1.25:0.875-1.25, and the concentration of EDTA is 0.05-0.15M.

[0010] Preferably, in step 1), the impregnation is performed by adding water as a dispersant, in a water bath at 40-60°C, with a stirring speed of 500-600 r / min, for an impregnation time of 120-180 min.

[0011] Preferably, in step 1), the solid-liquid separation is performed using high-speed centrifugation, with a centrifugation speed of 4000-5000 r / min and a centrifugation time of 15-20 min.

[0012] Preferably, the drying process is carried out using a vacuum oven drying method, with a drying temperature of 60-100℃ and a drying time of 24-36 hours.

[0013] Preferably, in step 2), the heating rate is 5-10℃ / min, the pyrolysis time is 60-120min, nitrogen is passed through for 15-20min before pyrolysis, nitrogen protection is maintained throughout the process, and the nitrogen flow rate is 100ml-200 / min.

[0014] The beneficial effects of this invention are as follows:

[0015] (1) This invention uses microalgae, which have large biomass, wide availability and low price, as raw materials. Through high-temperature pyrolysis, iron-manganese based composite microalgae biochar material with large specific surface area, rich oxygen-containing functional groups and many N and O adsorption sites is obtained.

[0016] (2) The addition of ferric chloride during the preparation process makes it magnetic and easy to recover. The addition of manganese sulfate increases its specific surface area and oxygen-containing functional groups. The addition of EDTA allows iron and manganese to be better loaded on microalgae. At the same time, the addition of EDTA enables biochar to produce specific chemical adsorption with phosphate, which further improves the adsorption performance of the material. The resulting biochar structure is a sheet-like aggregate with strong adsorption capacity. It has a good effect on adsorbing phosphate in polluted water bodies and can be applied to the treatment of phosphorus-polluted water bodies. It provides a new approach and idea for the removal of phosphate and the recycling of harmful algae in aquatic environments. Attached image description:

[0017] Figure 1The adsorption results of phosphate by the iron-manganese-based composite microalgae biochar material in Examples 1-3 and Comparative Example 1 are shown.

[0018] Figure 2 The image shows a SEM image of the iron-manganese based composite microalgae biochar material in Example 1.

[0019] Figure 3 This is a TEM image of the iron-manganese based composite microalgae biochar material in Example 1.

[0020] Figure 4 The figures show the N2 adsorption-pore size distribution curves and N2 adsorption-desorption curves of the iron-manganese based composite microalgae biochar material in Example 1.

[0021] Figure 5 The images show the infrared spectra of the iron-manganese-based composite microalgae biochar material before and after adsorption in Example 1. FMBC refers to the material before adsorption, and FMBC+P refers to the material after adsorption.

[0022] Figure 6 Thermogravimetric analysis (TGA) of the iron-manganese-based composite microalgae biochar material in Example 1.

[0023] Figure 7 The adsorption kinetics of phosphate by the iron-manganese-based composite microalgae biochar material in Example 1 are shown.

[0024] Figure 8 The isotherm of phosphate adsorption by the iron-manganese-based composite microalgae biochar material in Example 1 is shown. Detailed implementation method:

[0025] The following is a further description of the invention, but not a limitation thereof.

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. However, the examples given are not intended to limit the invention. Any modifications or substitutions made based on the teachings of this invention shall fall within the protection scope of this invention.

[0027] Example 1

[0028] Chlorella powder was mixed with ferric chloride and manganese sulfate at a mass ratio of 1:1.25:1.10, and 0.1M EDTA was added. Water was used as the dispersant, and the mixture was stirred in a 50℃ water bath at 600 rpm for 2.5 h. Afterwards, high-speed centrifugation was used for solid-liquid separation, followed by drying at 60℃ for 24 h, and finally pyrolysis at 650℃ for 2 h. The resulting iron-manganese-based composite microalgae biochar material was obtained after grinding and drying. BET test results are shown in Table 1. The biochar obtained in Example 1 was subjected to SEM, TEM, N2 adsorption-desorption, infrared spectroscopy, and thermogravimetric analysis. Results are shown in [Table 1]. Figures 2-6 .

[0029] Table 1

[0030]

[0031] Example 2

[0032] Chlorella powder was mixed with ferric chloride and manganese sulfate at a mass ratio of 1:1.25:0.875, and 0.1M EDTA was added. Water was used as the dispersant, and the mixture was stirred in a water bath at 50℃ for 2.5h at 600r / min. After that, solid-liquid separation was performed by high-speed centrifugation, and the mixture was dried at 60℃ for 24h. Finally, it was pyrolyzed at 650℃ for 1h, ground and dried to obtain iron-manganese based composite microalgae biochar material.

[0033] Example 3

[0034] Chlorella powder was mixed with ferric chloride and manganese sulfate at a mass ratio of 1:1.25:1.25, and 0.1M EDTA was added. Water was used as the dispersant, and the mixture was stirred in a water bath at 50℃ for 2.5h at 600r / min. After that, solid-liquid separation was performed by high-speed centrifugation, and the mixture was dried at 60℃ for 24h. Finally, it was pyrolyzed at 650℃ for 1.5h, ground and dried to obtain iron-manganese based composite microalgae biochar material.

[0035] Comparative Example 1

[0036] The difference from Example 1 is that EDTA was not added.

[0037] Experiment 1: Phosphate Adsorption Experiment

[0038] Experimental Procedure: 0.1 g of biochar from Examples 1-3 and Comparative Example 1 were placed in 100 ml Erlenmeyer flasks, respectively. Phosphate (KH₂PO₄) solution (50 mg / L) was added, and the flasks were incubated at 25°C and 600 rpm for 2 hours with constant temperature shaking. Small aliquots were then taken and centrifuged at 10000 rpm for 10 minutes. The supernatant was used to determine the phosphate concentration using the molybdenum antimony colorimetric method. Three replicates were performed for each group, and the average value was taken. Adsorption results are shown below. Figure 1 .

[0039] Depend on Figure 1It can be seen that the biochar in Example 1 exhibited an adsorption rate of 91.66% for phosphate, with an adsorption capacity of 23.42 mg / g; the biochar in Example 2 showed an adsorption rate of 79.62% for phosphate, with an adsorption capacity of 20.04 mg / g; the biochar in Example 3 showed an adsorption rate of 71.24% for phosphate, with an adsorption capacity of 17.83 mg / g; while the biochar in Comparative Example 1 showed an adsorption rate of only 4.13% for phosphate, with an adsorption capacity of 1.03 mg / g. The iron-manganese-based composite microalgae biochar materials prepared in Examples 1-3 of this invention all showed higher adsorption rates for phosphate in the adsorption experiment system than the biochar in the comparative examples, with the iron-manganese-based composite microalgae biochar material prepared in Example 1 exhibiting the best adsorption capacity for phosphate.

Claims

1. The application of iron-manganese based composite microalgae biochar material as a phosphorus removal adsorbent in the treatment of phosphorus-containing wastewater, characterized in that, The iron-manganese based composite microalgae biochar material is a microalgae biochar with a sheet-like structure loaded with iron and manganese. It is prepared from ferric chloride, manganese sulfate, Chlorella, and EDTA as raw materials, and its preparation method includes the following steps: 1) Mix Chlorella powder with ferric chloride, manganese sulfate and EDTA, add water as a dispersant, and impregnate in a water bath at 40-60 ℃ with a stirring speed of 500-600 r / min for 120-180 min. After solid-liquid separation, drying and grinding, a pretreated algae powder mixture is obtained. The mass ratio of Chlorella: Ferric chloride: Manganese sulfate is 1:0.5-1.25:0.5-1.25; 2) The pretreated algal powder mixture is pyrolyzed at a temperature of 650 ℃, a heating rate of 5-10 ℃ / min, and a pyrolysis time of 60-120 min. Nitrogen gas is passed through for 15-20 min before pyrolysis and nitrogen protection is maintained throughout the process. After drying, iron-manganese based composite microalgae biochar is obtained.

2. The application according to claim 1, characterized in that, Step 1) The mass ratio of Chlorella: Ferric chloride: Manganese sulfate is 1:1-1.25:0.875-1.

25.

3. The application according to claim 1, characterized in that, In step 1), the concentration of EDTA is 0.05-0.15M.

4. The application according to claim 1, characterized in that, In step 1), the solid-liquid separation is performed using high-speed centrifugation, with a centrifugation speed of 4000-5000 r / min and a centrifugation time of 15-20 min.

5. The application according to claim 1, characterized in that, The drying process described in step 1) is performed using a vacuum oven drying method, with a drying temperature of 60-100 ℃ and a drying time of 24-36 h.

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