CN114832778A - Shaddock peel biochar for adsorbing arsenic as well as preparation method and application thereof - Google Patents

Abstract

The invention provides a pomelo peel biochar used for adsorbing arsenic and a preparation method and application thereof, wherein the preparation method includes sequentially performing pre-treatment, solid-phase carbonization and grinding on the pomelo peel. In the technical scheme adopted in the present invention, the pomelo peel biochar obtained by solid-phase carbonization and grinding of pomelo peel includes a biochar body and particles attached to the surface of the biochar body, and the particle size of the particles is 200-400 nm. The nanometer size is smaller and the adsorption performance is stronger. In addition, grapefruit peel biochar has high content of potassium, calcium and other metals, which has a better adsorption and fixation effect on trivalent arsenic, and can be applied to the remediation of arsenic pollution in water and soil environments.

Description

Grapefruit peel biochar for arsenic adsorption and preparation method and application thereof

technical field

The invention relates to the technical field of comprehensive utilization of agricultural wastes, in particular to soil heavy metal pollution remediation, and more particularly to a preparation method of grapefruit peel biochar for arsenic adsorption, grapefruit peel biochar and applications thereof.

Background technique

Arsenic (As) is a metalloid element widely distributed in nature. Arsenic in soil is often present in the form of compounds, the most important of which are inorganic arsenic (III) and arsenic (V) compounds. Arsenic pollution in paddy soil and its long-term flooded tillage significantly increase the bioavailability of arsenic, which often leads to excessive inorganic arsenic content in rice. In my country's main rice-producing areas such as Hunan, Guangxi, Yunnan, Guizhou and Sichuan, the excessive rate of inorganic arsenic in rice is as high as 40-60%. Inorganic arsenic is a known human carcinogen. Long-term exposure to low levels of arsenic can increase the risk of various cancers, diabetes, and cardiovascular diseases, seriously threatening human health in my country. As the health problems caused by inorganic arsenic pollution in rice have attracted much attention, the treatment of arsenic-contaminated rice fields has become an urgent task in the field of environmental protection.

At present, the commonly used chemical methods for arsenic-contaminated soil remediation include immobilization, leaching, and electrokinetic remediation. Among them, the immobilization method is a technology that adsorbs or precipitates pollutants in the soil through a fixing agent, thereby reducing the potential risks caused by excessive pollutants in the soil. The core of the fixation method is the selection and preparation of the fixative. The existing arsenic removal fixatives include iron oxide, lime, solid waste, etc. These materials are expensive to prepare, or alter soil properties, or introduce other contaminants that increase health risks. At present, biochar materials in natural fixatives have the advantages of low preparation cost and ecological environmental protection, but usually have a limited capacity for adsorbing arsenic.

Biochar is obtained by pyrolysis of straw and other wastes under anoxic or anaerobic conditions. It has the characteristics of large specific surface area, high porosity, strong adsorption and stable chemical properties. Biochar can not only passivate and remediate pollutants in the soil, but also sequester carbon and reduce emissions and improve the soil environment. In recent years, biochar has been favored by scholars as a carrier or adsorbent commonly used to treat arsenic pollution in soil. However, at present, the biochars with better adsorption effect are all modified biochars, which are modified substances instead of biochars. This not only increases the steps of the preparation process, but also increases the cost and technical difficulty.

Because the white flesh structure of grapefruit peel is white cotton wool, there are many pores, a large number of white tendons and rich nutrients, and the surface of grapefruit peel is rough, which is a good raw material for the preparation of activated carbon. At present, there are also related reports that hydrothermal carbonization of grapefruit peel is used to obtain grapefruit peel biochar for the adsorption of heavy metal ions such as zinc, cadmium, lead, and copper. However, the chemical forms of arsenic as a metalloid element and heavy metal ions such as zinc, cadmium, lead, and copper are different, and the effect of biochar is different from that of biochar, and the biochar of grapefruit peel cannot achieve better adsorption of arsenic.

SUMMARY OF THE INVENTION

Based on the above problems, the object of the present invention is to provide a preparation method of grapefruit peel biochar, grapefruit peel biochar and application thereof, which have better adsorption effect on arsenic, especially trivalent arsenic, and are suitable for soil Repair of arsenic contamination.

In order to achieve the above object, the first aspect of the present invention provides a method for preparing pomelo peel biochar for adsorbing arsenic, which includes sequentially performing pretreatment, solid-phase carbonization and grinding on pomelo peel.

In the technical scheme adopted in the present invention, the pomelo peel is subjected to solid-phase carbonization and grinding to obtain pomelo peel biochar, and a large amount of particulate matter is attached to the surface of the biochar body obtained by solid-phase carbonization, and the particulate matter may be the white flesh structure of pomelo peel. It is formed by solid-phase carbonization. The nanometer size of the particles is small and the adsorption performance is strong. In addition, grapefruit peel biochar has high content of potassium, calcium and other metals, which can produce electrostatic adsorption for trivalent arsenic, which has a better adsorption and fixation effect, and can be used for the remediation of arsenic pollution in water and soil environments. The present invention utilizes agricultural waste pomelo peels to prepare biochar adsorbents with particles on the surface through a simple and rapid solid-phase carbonization method, fully utilizes resources, reduces environmental pollution, has good economic benefits, and is beneficial to industrialized production.

Preferably, the pretreatment includes naturally air-drying and pulverizing the grapefruit peel.

Preferably, the particle size of the grapefruit peel after being pulverized by a belt sieve pulverizer is 60 mesh.

Preferably, the temperature of the solid-phase carbonization is 300-700° C., and the time is 1-3 hours.

Preferably, the solid-phase carbonization is carried out in a muffle furnace, and the heating rate is 8-15° C./min.

The second aspect of the present invention provides grapefruit peel biochar, which is prepared by the aforementioned preparation method of grapefruit peel biochar, including a biochar body and particles attached to the surface of the biochar body, and the particle size of the biochar body is 800-2700 nm, and the particle size of the particles is 200-400 nm. The nanometer size of the particles obtained by the invention has a strong adsorption capacity for arsenic, and more importantly, a better adsorption effect for trivalent arsenic.

The third aspect of the present invention provides the application of grapefruit peel biochar. The grapefruit peel biochar is added to the arsenic-containing soil or water sample, mixed and subjected to adsorption treatment. The invention utilizes the grapefruit peel biochar with particles on the surface to repair arsenic pollution in water and soil.

Preferably, the ratio of the weight/g of the arsenic-containing soil to the weight/g of the grapefruit peel biochar is 100:1-3.

Preferably, the arsenic in the arsenic-containing soil is trivalent arsenic.

Description of drawings

Fig. 1 is the SEM image of grapefruit peel biochar in Example 1.

Fig. 2 is the particle size distribution result of grapefruit peel biochar tested by Zeta instrument in Example 1.

Figure 3 is the result of NMR test of grapefruit peel biochar in Example 1.

Figure 4 is the adsorption isotherm of arsenic adsorption by grapefruit peel biochar in Example 2.

Figure 5 shows the adsorption results of grapefruit peel biochar on arsenic in Example 3.

Detailed ways

The grapefruit peel biochar of the invention can be used for arsenic adsorption in arsenic-containing soil or water samples, and is especially suitable for the adsorption of trivalent arsenic. And during adsorption, grapefruit peel biochar was added to the arsenic-containing soil or water samples for adsorption treatment. Wherein, the ratio of the weight/g of the arsenic-containing soil to the weight/g of the grapefruit peel biochar is 100:1 to 3. More preferably, the ratio of the weight/g of the arsenic-containing soil to the weight/g of the grapefruit peel biochar is 100:3.

The preparation method of grapefruit peel biochar includes the following steps of pre-treatment, solid-phase carbonization and grinding of grapefruit peel.

Among them, the pretreatment includes natural air drying and pulverization of the pomelo peel. In the specific operation, it can be air-dried first and then pulverized, or it can be pulverized and then air-dried naturally. The temperature of natural air-drying is 25-40° C., that is, air-drying at room temperature, and the drying time is 5-7 d, preferably 25° C. natural air-drying, and the drying time is 7 d. The particle size of the grapefruit peel after being pulverized by a sieve pulverizer is 60 mesh.

The solid-phase carbonization is carried out in a muffle furnace, and the heating rate is 8-15°C/min, preferably 10°C/min. The temperature of solid-phase carbonization is 300～700℃, and the time is 1～3h. Preferably, it is 500°C and carbonized for 2h. During the solid-phase carbonization process, the grapefruit peel is first placed in a closed ceramic jar, and then placed in a muffle furnace for carbonization.

The pomelo peel after solid-phase carbonization can pass through a 2mm sieve after being ground. The pomelo peel biochar obtained after grinding includes a biochar body and particles attached to the surface of the biochar body, the particle size of the biochar body is 800-2700 nm, and the particle size of the particles is 200-400 nm.

In order to better illustrate the purpose, technical solutions and beneficial effects of the present invention, the present invention will be further described below with reference to specific embodiments. It should be noted that the following implementation of the method is a further explanation of the present invention, and should not be regarded as a limitation of the present invention.

Example 1 Preparation of grapefruit peel biochar

After the pomelo peel was naturally air-dried at 25°C for 7 days, it was pulverized by a sieve pulverizer to a particle size of 60 mesh, and placed in a closed ceramic jar. The ceramic jar was placed in a muffle furnace, and the muffle furnace was heated to 500 °C at 10 °C/min, and the pomelo peel was subjected to solid-phase carbonization reaction for 2 h. After the carbonization reaction, it is ground and pulverized to pass through a 2mm sieve to obtain grapefruit peel biochar. The grapefruit peel biochar was tested by SEM and Zeta instrument. The results are shown in Figure 1 and Figure 2, respectively. The particle size distribution of the biochar body is 800-2700 nm, and the surface is attached to particles. The particle size distribution of the particles is 200～400nm. NMR test and elemental analysis of grapefruit peel biochar were carried out. The results are shown in Figure 3 and Table 1, respectively. The surface of grapefruit peel biochar mainly contains elements such as carbon, oxygen, potassium, and calcium, and has functions such as hydroxyl, carboxyl, and carbonyl groups. group, which can adsorb trivalent arsenic through electrostatic adsorption, hydrogen bond formation, etc. In addition, metal cations such as potassium and calcium are beneficial to form complex complexes with particulate matter and trivalent arsenic on the surface of grapefruit peel biochar, and further adsorb trivalent arsenic.

Table 1 Elemental analysis of grapefruit peel biochar

Example 2 Adsorption of arsenic in aerobic water samples by grapefruit peel biochar

Take part of the grapefruit peel biochar obtained in Example 1, soak it in deionized water for 24 hours and stir regularly, and then filter it. The solid content obtained by filtration is dried at 60 ° C for 48 hours to obtain grapefruit peel biochar after removing surface particles.

First prepare As(III) and As(V) water samples with certain concentrations respectively. Weigh 0.05g of the grapefruit peel biochar (BC) obtained in Example 1 and 0.05g of the grapefruit peel biochar (SCBC) after removing the surface particles, and place them in a 50mL centrifuge tube, respectively, and accurately measure 25mL of As(III) and The As(V) water sample was added to the centrifuge tube, put on the lid and placed in a water bath shaker, shaken at 180 r/min for 24 hours at a water temperature of 25°C, and filtered.

The concentration of the obtained filtrate and the prepared As(III) and As(V) aqueous sample solutions were measured by atomic fluorescence spectrometer (AFS), and the adsorption amount was calculated according to the difference of the arsenic concentration before and after adsorption.

The results showed that the adsorption capacity of grapefruit peel biochar to As(III) water samples was 1365 μg/g, and the adsorption capacity of As(V) water samples was only 54 μg/g. The adsorption capacity of the grapefruit peel biochar to As(III) water samples after removing surface particles was 491 μg/g, and the adsorption capacity of As(V) water samples was only 55 μg/g. The comparison of the two shows that the pomelo peel biochar made by the present invention has better adsorption performance for arsenic, especially for trivalent arsenic, which may be due to the small particle size of the particles on the surface of the biochar body. The nano-size effect indicates that the pomelo peel is ground after solid-phase carbonization without cleaning and filtration, and the obtained pomelo peel biochar has a high adsorption performance for As(III), which is related to the more particles on its surface. The adsorption of As(III) by grapefruit peel biochar conforms to the Langmuir adsorption model.

Table 2 Adsorption results of arsenic in water samples

25ml water sample As(III) As(V) Adsorption capacity after 0.05g BC treatment 1365μg/g 54μg/g Adsorption capacity after 0.05g SCBC treatment 491μg/g 55μg/g

(Note: μg/g is the arsenic adsorbed per gram of particulate matter)

Example 3 Adsorption of grapefruit peel biochar on arsenic in anaerobic soil

The effect of pomelo peel biochar on arsenic adsorption in anaerobic soil was studied by simulating the microenvironment of flooded paddy field soil.

The specific operation is as follows: each weighing 7.0 g of arsenic-contaminated paddy soil is added to two 100 mL vials. Then, 0.21 g of grapefruit peel biochar in Example 1 was added to one of the vials, and the other vial was used as a blank control. Then 70 mL of PIPES buffer solution was added to each at a final concentration of 30 mM, pH 7.3. Finally, lactic acid was added as a carbon source for microbial growth and reproduction, and the final concentration of lactic acid was 10 mM. Each vial was filled with nitrogen, and then cultured in the dark under 30°C anaerobic conditions after capping. Use a disposable syringe to take the reaction solution supernatant from each vial, filter it with a 0.45 μm filter head, and place it in a centrifuge tube to add nitric acid for storage. The speciation of arsenic in the solution was determined by AFS to determine the effect of grapefruit peel biochar on the adsorption of arsenic in paddy soil. The results are shown in Figure 5. It can be seen from Figure 5 that, compared with the blank control without the addition of grapefruit peel biochar, on the 16th and 20th days of anaerobic culture, in the treatment of adding grapefruit peel biochar, the As(III) concentration in the aqueous solution can be reduced by 21.5-22.2%.

The raw material of the invention is grapefruit peel, and the preparation process is simple. At present, the annual output of pomelo in my country is about 20 million tons. The utilization of pomelo peel will reduce the cost of waste treatment. The use of grapefruit peel as the raw material for preparing biochar is applied to the arsenic remediation of polluted water and soil, turning waste into treasure, which is economically feasible, beneficial to industrial production, and has important environmental significance and application value.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it is not limited to those listed in the embodiments. It should be understood by those of ordinary skill in the art that the technical solutions of the present invention, such as the preparation process parameters of grapefruit peel biochar, can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention.

Claims (10)

1. a preparation method for the pomelo peel biochar for adsorbing arsenic, is characterized in that, comprises that pomelo peel is successively carried out to pretreatment, solid phase carbonization and grinding. 2 . The preparation method of the pomelo peel biochar for adsorbing arsenic according to claim 1 , wherein the pretreatment comprises naturally air-drying and pulverizing the pomelo peel. 3 . 3. The preparation method of the pomelo peel biochar for adsorbing arsenic according to claim 2, wherein the particle size of the pomelo peel after being pulverized by a belt sieve pulverizer is 60 meshes. 4 . The preparation method of grapefruit peel biochar for adsorbing arsenic according to claim 1 , wherein the temperature of the solid-phase carbonization is 300-700° C. and the time is 1-3 hours. 5 . 5 . The method for preparing grapefruit peel biochar for arsenic adsorption according to claim 1 , wherein the solid-phase carbonization is carried out in a muffle furnace, and the heating rate is 8-15° C./min. 6 . 6 . The preparation method of the pomelo peel biochar for adsorbing arsenic according to claim 1 , wherein the pomelo peel after solid-phase carbonization can pass through a 2mm sieve after being ground. 7 . 7. The grapefruit peel biochar prepared by the method for preparing the grapefruit peel biochar for adsorbing arsenic according to any one of claims 1 to 6, characterized in that it comprises a biochar body and a biochar body attached to the biochar body For the particles on the surface, the particle size of the biochar body is 800-2700 nm, and the particle size of the particles is 200-400 nm. 8 . The application of the pomelo peel biochar according to claim 7 , wherein the pomelo peel biochar is added to the arsenic-containing soil or water sample to mix and carry out adsorption treatment. 9 . 9 . The application of grapefruit peel biochar according to claim 8 , wherein the ratio of the weight/g of the arsenic-containing soil to the weight/g of the grapefruit peel biochar is 100:1-3. 10 . 10 . The application of grapefruit peel biochar according to claim 8 , wherein the arsenic in the arsenic-containing soil is trivalent arsenic. 11 .

Images