A preparation method of biochar composite material for efficiently removing mercury ions in the environment

Abstract

The present invention discloses a method for preparing a biochar composite material for efficiently removing mercury ions in the environment, and belongs to the technical field of preparation of environmental functional materials. The present invention solves the technical problems that the synthesis of existing biochar composite materials is complex and costly, and the biochar composite material may cause secondary pollution to the environment during use. The present invention directly mixes Chlorella powder and ferric sulfate solution and dries and pre-oxidizes them, so that the ferric sulfate is evenly distributed in the algae powder, improves the uniformity of the product, and then pyrolyzes under nitrogen protection to directly prepare the biochar composite material. The obtained biochar composite material has a fast and efficient removal rate of mercury in the environment, with a minimum removal efficiency of 88% at a concentration of 40 mg / L, and the biochar composite material can efficiently remove mercury in a variety of water environments, and the removal rate is fast and there is no secondary pollution.

Description

Technical Field

[0001] The invention relates to a method for preparing a biochar composite material for efficiently removing mercury ions in the environment, and belongs to the technical field of preparation of environmental functional materials. Background Art

[0002] Among heavy metal pollution, mercury pollution is considered to be one of the most harmful pollutants to human health. Mercury has strong toxicity and bioaccumulation in the environment. It can be converted into more toxic organic mercury through biological and non-biological processes, and after entering the organism, it is converted into highly toxic organic mercury compounds that are not easy to bioremediate. The methods currently used to treat mercury in wastewater include chemical precipitation, coagulation, ion exchange, adsorption, reduction and membrane separation, but these methods have high operating costs and low removal efficiency. In recent years, biochar has won a lot of attention as a raw material among its wide range of high-quality adsorbents, but the specific surface area of ​​existing biochar is small, the saturated adsorption capacity is low, and biochar is mainly physical adsorption, the removal rate is slow, and there is desorption phenomenon and unstable adsorption. Therefore, people modify biochar on the basis of pyrolysis to obtain biochar composite materials, but the current methods for modifying biochar are relatively cumbersome and costly. Therefore, it is very necessary to provide a preparation method for biochar composite materials with simple synthesis method and low cost. Summary of the invention

[0003] In order to solve the technical problems that the synthesis of existing biochar composite materials is complex and costly, and the biochar composite materials may cause secondary pollution to the environment during use, the present invention provides a preparation method of a biochar composite material with a simple synthesis method, low cost and low pollution, and can effectively remove mercury metal in the environment.

[0004] The technical solution of the present invention:

[0005] A method for preparing a biochar composite material for efficiently removing mercury ions in the environment, the method comprising the following steps:

[0006] Step 1, drying the biomass to obtain biomass powder;

[0007] Step 2, mixing ferric sulfate, biomass powder and water, and then drying and pre-oxidizing in an oven to obtain a mixture;

[0008] Step 3, pyrolyzing the mixture obtained in step 2 in a tubular furnace, and then grinding to obtain a biochar composite material.

[0009] It is further defined that the specific operation process of step 1 is: drying the biomass in an oven at 45° C. for 24 hours.

[0010] In a further embodiment, the biomass is Chlorella.

[0011] It is further defined that the specific operation process of step 2 is: add ferric sulfate into a corundum boat and add water to dissolve it, then add biomass powder, mix evenly, and place in an oven at 75-85°C for drying and pre-oxidation treatment for 36 hours.

[0012] It is further defined that the mass ratio of iron sulfate to biomass powder is (0.35-0.7):1.

[0013] It is further defined that the specific operation process of step 3 is: placing the mixture obtained in step 2 into a tubular furnace, introducing nitrogen at a flow rate of 200 mL / min, and heating to 700°C at a heating rate of 3 to 7°C / min, keeping warm for 2 hours, naturally cooling to room temperature, turning off the nitrogen, obtaining biochar, grinding, and obtaining a biochar composite material.

[0014] The biochar composite material prepared by the above method is used to remove mercury in the water environment, and the removal efficiency is 87.8-92.2%.

[0015] The present invention has the following beneficial effects: the present invention directly mixes the chlorella powder and the iron sulfate solution and dries and pre-oxidizes them, so that the iron sulfate is evenly distributed in the algae powder, improving the uniformity of the product, and then pyrolyzes under nitrogen protection to directly prepare a biochar composite material. The biochar composite material can efficiently remove mercury in a variety of water environments, and the removal rate is fast and there is no secondary pollution. In addition, the present invention also has the following advantages:

[0016] (1) The method provided by the present invention is simple, with cheap raw materials, low cost and low energy consumption;

[0017] (2) The biochar composite material obtained by the present invention has a fast and efficient removal rate of mercury in the environment, with a minimum removal efficiency of 88% at a concentration of 40 mg / L, and the material can effectively remove mercury in a variety of water environments;

[0018] (3) The biochar composite material obtained by the present invention does not cause the risk of secondary pollution to the environment during the process of removing mercury from the environment;

[0019] (4) The preparation process of the present invention does not require complicated special instruments and equipment, and has a wide range of application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a microstructure diagram of the biochar composite material prepared in Example 1;

[0021] Figure 2 This is a comparison chart of the removal efficiency of mercury ions of different concentrations by the biochar composite material prepared in Example 1;

[0022] Figure 3This is a comparison chart of the mercury ion removal efficiency of different biochar composite materials prepared in Example 1 in different water environments. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0024] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0025] Embodiment 1:

[0026] Step 1: Dry the Chlorella in an oven at 45°C for 24 hours.

[0027] Step 2, adding ferric sulfate to a corundum boat and adding water to dissolve it, then adding the chlorella powder obtained in step 1, mixing evenly, and drying in an oven at 80°C for 36 hours. The purpose of the drying treatment is to pre-oxidize the chlorella powder while drying the mixture, wherein the mass ratio of ferric sulfate to chlorella powder is 0.7:1. Too high or too low a mass ratio will affect the adsorption capacity of the final product.

[0028] Step 3, placing the mixture obtained in step 2 into a tubular furnace, introducing nitrogen at a flow rate of 200 mL / min to prevent oxidation of the biochar composite material during pyrolysis, and heating the mixture to 700°C at a heating rate of 5°C / min, keeping the temperature for 2 hours, naturally cooling the mixture to room temperature, turning off the nitrogen, obtaining the biochar, and grinding the biochar to obtain the biochar composite material.

[0029] The surface microstructure of the obtained biochar composite material was characterized by high-power transmission electron microscopy. Figure 1 Said by Figure 1 It can be seen that ferrous sulfide is wrapped inside the biochar, its size is between 25-50nm, and it is evenly distributed inside the biochar.

[0030] Under laboratory conditions, the biochar composite material obtained above was used to remove mercury ions from water environments with different concentrations. The test conditions were: the mercury ion concentrations in the experimental water were 3.76 mg / L, 7.57 mg / L, 13.3 mg / L and 39.4 mg / L, respectively. 30 mg of the biochar composite material was added to 30 mL of the experimental water. After 24 hours of treatment, the mercury ion concentration in each experimental water was tested, and the mercury ion removal efficiency was calculated. The results are as follows Figure 2 As shown by Figure 2It can be seen that the mercury removal capacity of biochar composite materials can reach up to 92% under laboratory conditions.

[0031] Under laboratory conditions, the biochar composite material obtained above was used to carry out removal tests on different complex water environments. The test conditions were: the complex water environments were high-organic wastewater, groundwater and seawater, and the mercury ion concentrations in each complex water environment were 13.2 mg / L, 15.8 mg / L, and 28.1 mg / L, respectively. 30 mg of the biochar composite material was added to 30 mL of the experimental water. After 24 hours of treatment, the mercury ion concentration in each experimental water was tested, and the mercury ion removal efficiency was calculated. The results are as follows Figure 3 As shown by Figure 3 It can be seen that biochar composite materials can effectively remove mercury in different complex water environments under laboratory conditions.

[0032] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a biochar composite material for efficiently removing mercury ions in the environment, characterized in that: The method comprises the following steps: Step 1, drying the biomass to obtain biomass powder; The biomass is Chlorella vulgaris; the specific operation process of step 1 is: drying the biomass in an oven at 45° C. for 24 hours; Step 2, mixing ferric sulfate, biomass powder and water, and then drying and pre-oxidizing in an oven to obtain a mixture; The mass ratio of the iron sulfate to the biomass powder is (0.35-0.7):1; The specific operation process of step 2 is: adding ferric sulfate to a corundum boat and adding water to dissolve it, then adding biomass powder, mixing evenly, and placing in an oven at 75-85° C. for drying and pre-oxidation treatment for 36 hours; Step 3, placing the mixture obtained in step 2 into a tubular furnace, introducing nitrogen at a flow rate of 200 mL / min, and heating to 700°C at a heating rate of 3-7°C / min, keeping warm for 2 hours, naturally cooling to room temperature, turning off the nitrogen, obtaining biochar, grinding, and obtaining a biochar composite material.

2. Use the biochar composite material prepared by the method described in claim 1 to remove mercury in the water environment.

3. The method for removing mercury from water environment using biochar composite material according to claim 2, characterized in that: The removal efficiency is 87.8~92.2%.

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