Modified biochar and application thereof in cadmium-polluted soil remediation and vegetable quality improvement

Abstract

The invention discloses modified biochar and application thereof in remediation of cadmium-contaminated soil and improvement of vegetable quality, according to the scheme, taxus chinensis sawdust is used as a wood biochar raw material, biochar is prepared through pyrolysis at 550 DEG C, then the biochar is mixed with sepiolite, then the biochar is prepared by adopting an ultrafine pulverizer, and the biochar is applied together with chemical fertilizer, so that the quality of cadmium-contaminated soil is improved. The method is used for vegetable quality improvement and soil pollution remediation; the charcoal has the effects of providing nutrients required by plant growth, promoting plant growth and biomass accumulation, improving plant photosynthetic ability, improving plant quality and the like on plants. According to the scheme, the biochar material prepared by the ultrafine pulverizer has the advantages of ultrafine particle size, uniform distribution and higher adsorption performance. Generally speaking, the biochar provided by the scheme is simple and convenient to prepare, has a high prevention and control effect on the polluted soil, and can effectively reduce the content of effective cadmium in the soil, improve the soil stability and realize a win-win situation of economy, society and environment.

Description

Technical Field

[0001] The present invention relates to the field of soil pollution remediation technology in the field of environmental science and engineering, and in particular to modified biochar and its application in remediation of cadmium-contaminated soil and improvement of vegetable quality. Background Art

[0002] With the rapid development of industry, production activities in many sectors, such as mining, metallurgy, electroplating, and chemicals, generate massive amounts of waste that require disposal daily. Furthermore, some factories produce cadmium-containing wastewater as a byproduct. When these wastes and residues are accumulated in storage yards, they can easily seep and wash away heavy metals, leading to the soil's increasing problem of cadmium contamination. Once soil is contaminated with cadmium, it poses a significant threat. Cadmium, in particular, is not static and fixed in the soil. Its physical and chemical forms can undergo numerous changes, sometimes dissolving in the soil solution, sometimes attaching to the surface of soil particles, and even reacting with other soil substances to form new compounds. This fluctuating form makes cadmium's migration complex. Cadmium can be carried deep into the soil by rainwater or absorbed by plant roots and transported aboveground. Contaminated soil significantly reduces its fertility, not only impacting crop growth but also accumulating through the food chain, posing a serious threat to human health.

[0003] Traditional methods for remediating cadmium contamination in soil, such as chemical leaching, can quickly remove some cadmium, but they are prone to secondary pollution and are costly. The soil-injection method is labor-intensive and severely disrupts the soil ecosystem. In recent years, biochar has emerged as a promising environmental treatment method. Its porous structure and rich functional groups enable it to adsorb heavy metals and improve soil properties. However, conventional biochar is limited by factors such as particle size and pore distribution, and its adsorption efficiency, morphological regulation, and migration retardation for cadmium need to be improved.

[0004] The rise of ultrafine-grade material technology has brought a turning point in the application of biochar. Due to its unique size effect, biochar has a larger specific surface area and stronger reactivity. Currently, related research is still in the exploratory stage. This proposal uses biochar as a remediation material, employing potted plant experiments and using spectroscopic and molecular biology techniques to study its effects on the transformation and migration of heavy metals such as lead and cadmium in soil, as well as its ability to control heavy metals in plants. This study provides technical support and theoretical guidance for the application of biochar in soil heavy metal remediation. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to propose a modified biochar and its application in the remediation of cadmium-contaminated soil and the improvement of vegetable quality. This solution is reliable in implementation and flexible in application. It can use biochar to passivate and control cadmium in contaminated soil. By enhancing the interaction between biochar and cadmium, the bioavailability and mobility of cadmium in the soil are reduced, thereby reducing the transfer of cadmium into plants, improving soil environmental quality, and ensuring the safety of agricultural products.

[0006] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0007] A method for preparing modified biochar comprises: washing and drying a woody biochar raw material, subjecting it to pyrolysis and carbonization under oxygen-limited conditions, cooling the product to room temperature to obtain biochar, mixing the biochar with sepiolite under stirring conditions, adding deionized water to mix them evenly, and drying and pulverizing the mixture to a preset particle size to obtain modified biochar.

[0008] As a possible implementation method, further, the wood biochar raw material described in this solution is washed with deionized water and then air-dried.

[0009] As a possible implementation method, further, the oxygen-limited condition described in this solution is to introduce nitrogen as a protective gas to reduce the oxygen content in the pyrolysis carbonization treatment environment.

[0010] As a possible implementation manner, further, the temperature of the pyrolysis carbonization treatment in this solution is 550°C, the heating rate during the heating process is 10°C / min, and the pyrolysis carbonization time is 2h.

[0011] As a possible implementation method, further, the biochar and sepiolite described in this solution are mixed in a mass ratio of 2:1.

[0012] As a possible implementation manner, further, the wood biochar raw material described in this solution is one or more of yew, nanmu, and camphor wood sawdust.

[0013] As an example of a preferred implementation option, the preparation method of this solution includes the following steps:

[0014] (1) Biochar preparation: The woody biochar raw material was washed with deionized water and air-dried, and then pyrolyzed and carbonized under oxygen-limited conditions at a target temperature of 550°C and a heating rate of 10°C / min for 2 h. The product was then cooled to room temperature in the furnace to obtain biochar.

[0015] (2) Preparation of modified biochar: Biochar and sepiolite were mixed in a mass ratio of 2:1, and deionized water was added under stirring to mix them evenly. The mixed system was then dried and crushed to a preset particle size using an ultrafine grinder to obtain modified biochar.

[0016] Based on the above, this solution also provides a modified biochar, which is prepared by the preparation method described above.

[0017] Based on the above, this solution also provides an application of modified biochar in the remediation of cadmium-contaminated soil and / or improvement of vegetable quality; wherein the vegetable is Shanghai pakchoy.

[0018] The modified biochar mentioned in this solution is not limited to being used for the remediation of cadmium-contaminated soil, it can also be used in other soil pollution situations to achieve soil remediation or improvement.

[0019] In terms of application, this project explored the impact of biochar through potted plant experiments. The experiment consisted of a control group, a pollution group, a microbial char group, and a biochar group. Each group had four replicates, and each pot weighed 2 kg of soil. The biochar application rate was 20 g per pot, mixed evenly with soil sieved through a 2 mm sieve before planting the seedlings.

[0020] Through experimental demonstration, this scheme combines the prepared biochar with chemical fertilizers to improve the cadmium barrier rate of Chinese cabbage. By applying biochar and then applying it to Chinese cabbage, the cadmium content in Chinese cabbage plants decreased by 14.18% compared with the contaminated group and 7.13% in the unmodified biochar group, and the biomass of Chinese cabbage was significantly increased.

[0021] The above-mentioned technical solution offers the following advantages over existing technologies: The present invention utilizes yew wood chips as the raw material for wood biochar, producing biochar through pyrolysis at 550°C. This biochar is then mixed with sepiolite and processed using an ultrafine grinder. This biochar, when combined with fertilizer, can be used to improve vegetable quality and remediate soil contamination. The biochar's benefits for plants include providing nutrients, promoting plant growth and biomass accumulation, increasing photosynthetic capacity, and improving plant quality. Regarding production, the ultrafine grinder used in this method offers advantages over conventional ball milling, including ease of operation and temperature control. The resulting biochar exhibits ultra-small, uniform particle size distribution and enhanced adsorption properties. Overall, the biochar produced in this method is easy to produce and highly effective in controlling contaminated soil. It can effectively reduce the effective cadmium content in soil and increase soil stability, achieving a win-win situation for the economy, society, and the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is an electron microscope characterization image of the modified biochar prepared in Example 1 of this scheme. DETAILED DESCRIPTION

[0024] The present invention will be described in further detail below with reference to the accompanying drawings and examples. It is particularly noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Similarly, the following examples are only some embodiments of the present invention and are not intended to be exhaustive. All other embodiments obtained by those of ordinary skill in the art without creative effort are intended to fall within the scope of protection of the present invention.

[0025] Example 1

[0026] This embodiment provides a method for preparing modified biochar, which includes:

[0027] (1) Biochar preparation: The yew sawdust was used as the raw material for wood biochar, washed with deionized water to remove impurities, and then air-dried. After the wood biochar raw material was dried, it was moved into a carbonization chamber, and nitrogen was introduced to create an oxygen-limited condition. The wood biochar raw material was pyrolyzed and carbonized at a target temperature of 550°C and a heating rate of 10°C / min for 2 h. The product was then cooled to room temperature in the furnace to obtain biochar.

[0028] (2) Preparation of modified biochar: The prepared biochar and sepiolite were mixed in a mass ratio of 2:1, and deionized water was added under stirring to mix them evenly. The mixed system was then dried and processed using an ultrafine grinder at a grinding parameter of 8000 r / min until the material reached a micron-level particle size close to the nanometer level to obtain modified biochar.

[0029] Among them, the number of teeth of the static blade of the ultrafine grinder can be 200, which crushes the material to reduce the particle size and increase its specific surface area until the biochar material is crushed to a micron-level particle size close to the nanometer level.

[0030] The biochar material prepared in this example was observed under an electron microscope, and the results were shown in FIG. Figure 1 shown.

[0031] The physical and chemical properties of the prepared modified biochar were measured, and the results were: pH 10.07, total carbon 328 g / kg, total nitrogen 2.68 g / kg, total phosphorus 1.69 g / kg, and total potassium 3.71 g / kg.

[0032] Example 2

[0033] In order to verify the effect of the modified biochar in Example 1 on soil cadmium passivation and plant cadmium absorption and isolation, this embodiment also proposes the following example combined with a potted plant experiment for comparison.

[0034] Potted plant experiment 1

[0035] The basic chemical properties of the soil used in the experiment were: pH 5.57, total nitrogen 0.62 g / kg, total phosphorus 0.58 g / kg, total potassium 41.28 g / kg, available phosphorus 16.32 mg / kg, available potassium 123.65 mg / kg, and cadmium 0.09 mg / kg.

[0036] The pot size of the pot experiment was (18.5cm*15.0cm), and the experimental object was Shanghai pakchoy; the experiment set up two treatments: control group and pollution group.

[0037] Among them, the control group did not add pollutants, and the polluted group was polluted with 5 mg / kg cadmium. Each group had 4 replicates, and the soil weight of each pot was 2 kg.

[0038] The same management measures were adopted for 45 days after planting, and plant height, leaf number, stem diameter, plant cadmium content, and soil cadmium content were measured. The effects of the pollution and control groups on the quality of pakchoi and soil are shown in Table 1.

[0039] As can be seen from Table 1, the plant height, leaf number, stem diameter, plant cadmium content and soil cadmium content of the pollution group (P group) were different from those of the control group (CK group). The plant height, leaf number and stem diameter decreased by 25.27%, 33.33% and 33.88% respectively. The cadmium content in plants increased by 1.32 mg / kg, the exchangeable cadmium content in the soil increased by 1.71 mg / kg, the reducible cadmium content in the soil increased by 1.21 mg / kg, the oxidizable cadmium content in the soil increased by 0.98 mg / kg and the residual cadmium content in the soil increased by 0.83 mg / kg.

[0040] Table 1 Effects of pollution on soil cadmium forms and pakchoy

[0041]

[0042] From the above, we can know that when cadmium contamination occurs in the soil, it will have a negative impact on the growth quality of Shanghai cabbage and the soil.

[0043] Potted plant experiment 2

[0044] The basic chemical properties of the soil used in the experiment were pH 5.57, total nitrogen 0.62 g / kg, total phosphorus 0.58 g / kg, total potassium 41.28 g / kg, available phosphorus 16.32 mg / kg, available potassium 123.65 mg / kg, and cadmium 0.09 mg / kg.

[0045] The pot size of the pot experiment was (18.5cm*15.0cm), and the experimental object was Shanghai pakchoy; the experiment set up two treatments: pollution group (P) and unmodified biochar group (B).

[0046] Among them, the pollution group (Group P) was not applied with biochar, and the biochar group (Group B) was the unmodified biochar prepared in step (1) of Example 1. Each group had 4 replicates, the soil weight of each pot was 2 kg, and the biochar application rate was 20 g / pot.

[0047] The same management measures were adopted. After 45 days of planting, plant height, leaf number, stem diameter, plant cadmium content, and soil cadmium content were measured. The effects of the pollution group (P) and the biochar group (B) on the quality of pakchoi and soil are shown in Table 2.

[0048] It can be seen that the plant height, leaf number and stem diameter of the Shanghai cabbage corresponding to the biochar group increased by 38.19%, 50% and 55% respectively compared with the pollution group. The plant cadmium content decreased by 6.4%, the exchangeable cadmium content in the soil decreased by 4.79%, the reducible cadmium content in the soil decreased by 6.81%, the oxidizable cadmium content in the soil increased by 3.81%, and the residual cadmium content in the soil increased by 7.78%.

[0049] Table 2 Effects of biochar on soil cadmium forms and pakchoy

[0050]

[0051] As can be seen from the above, adding the biochar prepared in this embodiment to the soil has a promoting effect on soil improvement and the growth quality of Shanghai pakchoy.

[0052] Potted experiment 3

[0053] The basic chemical properties of the soil used in the experiment were pH 5.57, total nitrogen 0.62 g / kg, total phosphorus 0.58 g / kg, total potassium 41.28 g / kg, available phosphorus 16.32 mg / kg, available potassium 123.65 mg / kg, and cadmium 0.09 mg / kg.

[0054] The pot size of the pot experiment was (18.5cm*15.0cm), and the experimental object was Shanghai green cabbage; the experiment set up two treatments: pollution group (P) and biochar group (NMB).

[0055] The contaminated group (P) was not treated with biochar, while the biochar group (NMB) was treated with the biochar prepared in step (2) of Example 1. Each group consisted of four replicates, with each pot weighing 2 kg of soil and applying 20 g of biochar per pot. The same management measures were adopted, and after 45 days of cultivation, plant height, leaf number, stem diameter, plant cadmium content, and soil cadmium content were measured. Table 3 shows the effects of the contaminated group on the quality of Chinese cabbage and the soil. Table 3 also shows the effects of the biochar group on the quality of Chinese cabbage and the soil.

[0056] It can be seen that compared with the pollution group (P), the plant height, leaf number and stem diameter of the biochar group (NMB) increased by 59.37%, 66.67% and 63.38% respectively, the plant cadmium content decreased by 10.6%, the exchangeable cadmium content in the soil decreased by 9.57%, the reducible cadmium content in the soil decreased by 16.67%, the oxidizable cadmium content in the soil increased by 20.95%, and the residual cadmium content in the soil increased by 14.44%.

[0057] Table 3 Effects of biochar on soil cadmium forms and pakchoy

[0058]

[0059] As can be seen from the above, the biochar prepared in this embodiment has a significant promoting effect on soil improvement and the growth quality of Shanghai pakchoy.

[0060] Potted experiment 4

[0061] The basic chemical properties of the soil used in the experiment were pH 5.57, total nitrogen 0.62 g / kg, total phosphorus 0.58 g / kg, total potassium 41.28 g / kg, available phosphorus 16.32 mg / kg, available potassium 123.65 mg / kg, and cadmium 0.09 mg / kg.

[0062] The pot size of the pot experiment was (18.5cm*15.0cm), and the experimental object was Shanghai green cabbage; the experiment set up two treatments: unmodified biochar group (B) and biochar group (NMB).

[0063] Among them, the biochar group is the unmodified biochar prepared in Example 1, with 4 replicates per group, 2 kg of soil per pot, and 20 g of biochar applied per pot. The same management measures were taken, and after 45 days of planting, the plant height, number of leaves, stem diameter, plant cadmium content, and soil cadmium content were measured. The effects of the pollution group on the quality of Chinese cabbage and soil are shown in Table 4. The effects of the biochar group on the quality of Chinese cabbage and soil are shown in Table 4. It can be seen that the plant height, number of leaves, and stem diameter of biochar increased by 15.33%, 11.11%, and 6.05%, respectively, the plant cadmium content decreased by 6.8%, the exchangeable cadmium content in the soil decreased by 5.03%, the reducible cadmium content in the soil decreased by 10.57%, the oxidizable cadmium content in the soil increased by 16.51%, and the residual cadmium content in the soil increased by 6.19%.

[0064] Table 4 Effects of biochar modification on soil cadmium forms and pakchoy

[0065]

[0066] Comprehensive analysis shows that the biochar prepared by this scheme has the best effect on soil cadmium forms and pakchoi, lower cost and best comprehensive benefits.

[0067] The above descriptions are only some embodiments of the present invention and do not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made by using the contents of the description and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing modified biochar, characterized in that: It includes: After washing and drying the wood biochar raw material, it is subjected to pyrolysis and carbonization treatment under oxygen-limited conditions. The product is then cooled to room temperature to obtain biochar. The biochar is then mixed with sepiolite under stirring conditions. At the same time, deionized water is added to mix the mixture evenly. The mixed system is then dried and crushed to a preset particle size to obtain modified biochar.

2. The method for preparing modified biochar according to claim 1, wherein: The wood biochar raw material is washed with deionized water and then air-dried.

3. The method for preparing modified biochar according to claim 1, wherein: The oxygen-limited condition is to introduce nitrogen as a protective gas to reduce the oxygen content in the pyrolysis carbonization treatment environment.

4. The method for preparing modified biochar according to claim 1, wherein: The temperature of the pyrolysis carbonization treatment is 550° C., the heating rate during the heating process is 10° C. / min, and the pyrolysis carbonization time is 2 h.

5. The method for preparing modified biochar according to claim 1, wherein: The biochar and sepiolite are mixed in a mass ratio of 2:

1.

6. The method for preparing modified biochar according to any one of claims 1 to 5, characterized in that: The wood biochar raw material is one or more of yew, nanmu and camphor wood sawdust.

7. The method for preparing modified biochar according to claim 6, wherein: It includes the following steps: (1) After washing the wood biochar raw material with deionized water and air-drying, it was pyrolyzed and carbonized under oxygen-limited conditions at a target temperature of 550°C and a heating rate of 10°C / min for 2 h. The product was then cooled to room temperature in the furnace to obtain biochar; (2) Biochar and sepiolite are mixed in a mass ratio of 2:1, and deionized water is added under stirring to mix them evenly. The mixed system is then dried and crushed to a preset particle size using an ultrafine grinder to obtain modified biochar.

8. A modified biochar, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 7.

9. Application of modified biochar in remediation of cadmium-contaminated soil and / or improvement of vegetable quality.

10. The use according to claim 9, characterized in that: The vegetable is Shanghai green cabbage.

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