A soil conditioner containing biochar, its preparation method and application

Abstract

This invention belongs to the field of soil remediation technology, specifically relating to a soil conditioner containing biochar, its preparation method, and its application. The biochar within the particle size range described in this invention is less prone to loss through surface runoff, thus reducing its ability to improve soil structure. It also possesses sufficient specific surface area to load alkaline groups, increasing the pH value of soil in rare earth tailings waste sites. When applied to soil in rare earth tailings waste sites, it can maximize the effect of biochar, effectively improving soil structure, physicochemical properties, and microecology, and promoting plant growth. Example results show that, compared to soil conditioners containing biochar with an undefined particle size range, the soil conditioner containing biochar with a fixed particle size range provided by this invention increases the dry weight of ryegrass by 13.07%–20.96%.

Description

Technical Field

[0001] This invention belongs to the field of soil remediation technology, specifically relating to a soil conditioner containing biochar, its preparation method, and its application. Background Technology

[0002] Rare earth tailings areas, lacking vegetation cover, are highly susceptible to severe soil erosion, leading to soil degradation problems such as soil structure damage, fertility decline, and acidification. Furthermore, heavy metal pollution makes it difficult for most plants to grow normally. Even with favorable hydrothermal conditions allowing for natural succession and regeneration, it can take decades or even centuries for the soil in rare earth tailings areas to recover to its original state. During this period, the severe soil degradation, water and soil erosion, environmental pollution, and ecological restoration issues remain unresolved. Currently, soil amendment techniques are the preferred method for remediating soil in rare earth tailings waste sites. Soil amendments often include organic fertilizers, bio-manure, lime, and biochar. However, current biochar soil amendments have only undergone simple studies on biochar dosage and ratio, and their remediation effect on ion-adsorption rare earth tailings waste sites has not met expectations. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a soil conditioner containing biochar, its preparation method and application. The soil conditioner containing biochar provided by the present invention screens biochar and selects biochar with a specific particle size composition, which can maximize its role in alleviating soil acidification, improving soil microecology, improving soil structure and promoting plant growth.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] This invention provides a soil conditioner containing biochar, comprising biochar and organic fertilizer; the biochar has a particle size of 0.15–2 mm.

[0006] Preferably, the mass ratio of biochar to organic fertilizer is 4 to 6:1.

[0007] Preferably, the biochar preparation method involves sequentially anaerobic carbonizing, pulverizing, and sieving the biomass raw material to obtain biochar.

[0008] Preferably, the anaerobic carbonization temperature is 450–550°C, and the holding time is 50–70 min.

[0009] Preferably, the rate of heating to the anaerobic carbonization temperature is 8–12 °C / min.

[0010] Preferably, the biomass raw material includes tulip tree and / or rice husk.

[0011] This invention also provides a method for preparing the biochar-containing soil conditioner described in the above technical solution, comprising the following steps:

[0012] The biochar and organic fertilizer are mixed to obtain a soil conditioner containing biochar.

[0013] The present invention also provides the application of the soil conditioner containing biochar described in the above technical solution or the soil conditioner containing biochar prepared by the preparation method described in the above technical solution in the remediation of soil in ion-type rare earth tailings waste sites.

[0014] Preferably, the mass of the soil conditioner containing biochar is 5-7% of the dry weight of the soil in the ion-type rare earth tailings waste site.

[0015] This invention provides a soil conditioner containing biochar, comprising biochar and organic fertilizer; the biochar has a particle size of 0.15–2 mm. The biochar in this soil conditioner, with a particle size range specified in the invention, is less prone to loss due to surface runoff, thus preserving its ability to improve soil structure. It also possesses sufficient specific surface area to support alkaline groups, increasing the pH value of soil in ion-exposed rare earth tailings waste sites. When applied to such soil, it maximizes the effect of biochar, effectively improving soil structure, physicochemical properties, and microecology, and promoting plant growth. Example results show that, compared to soil conditioners containing biochar with an undefined particle size range, the soil conditioner with biochar of a fixed particle size range provided by this invention increases the dry weight of ryegrass by 13.07–20.96%. Attached Figure Description

[0016] Figure 1 The total dry weight of ryegrass after soil remediation using a soil conditioner containing biochar, in which biochar and organic fertilizer are mixed in different mass ratios, as shown in Example 1 of the present invention.

[0017] Figure 2 Total dry weight of ryegrass after remediation with a soil conditioner containing biochar and a soil conditioner containing biochar with an undefined particle size range, as shown in Example 2 of this invention.

[0018] Figure 3 The total dry weight of ryegrass after remediation using a soil conditioner containing biochar and a soil conditioner containing biochar with an undefined particle size range, as shown in Example 3 of the present invention. Detailed Implementation

[0019] This invention provides a soil conditioner containing biochar, comprising biochar and organic fertilizer; the biochar has a particle size of 0.15–2 mm.

[0020] Unless otherwise specified, the present invention does not have special requirements on the source of raw materials used, and commercially available products well known to those skilled in the art can be used.

[0021] The soil conditioner containing biochar provided by this invention includes biochar. In this invention, the particle size of the biochar is 0.15–2 mm.

[0022] In this invention, the preferred method for preparing biochar is to sequentially subject biomass raw materials to anaerobic carbonization, pulverization, and sieving to obtain biochar. In this invention, the anaerobic carbonization temperature is preferably 450–550°C, more preferably 500°C, and the holding time is preferably 50–70 min, more preferably 60 min; the vacuum degree of the anaerobic carbonization is preferably 200–400 Pa, more preferably 300 Pa; the rate of heating to the anaerobic carbonization temperature is preferably 8–12°C / min, more preferably 10°C / min; the biomass raw materials preferably include tulip tree and / or rice husks; the anaerobic carbonization equipment is preferably a well-type vacuum furnace; the pulverization equipment is preferably a disc mill; and the sieve used for sieving has a mesh size of 10–100 mesh.

[0023] The biochar-containing soil conditioner provided by this invention features biochar with a specific particle size range. Within this range, it avoids the problems of excessively small biochar particle size leading to damage to some pore structure, reduced ability to improve soil structure, and inability to provide a suitable living environment for microorganisms, thus weakening its effect on improving soil microecology and promoting plant growth. It also avoids the problem of excessively small biochar particles being easily lost through surface runoff, further diminishing its effect on improving soil structure. Conversely, it avoids excessively large biochar particles, which reduce specific surface area and weaken its ability to raise the pH value of acidic soils. The biochar-containing soil conditioner provided by this invention is not easily lost through surface runoff and has sufficient specific surface area to load alkaline groups, raising the pH value of acidic soils. This maximizes the effects of biochar in alleviating soil acidification, improving soil microecology, improving soil structure, and promoting plant growth.

[0024] The soil conditioner containing biochar provided by this invention includes organic fertilizer. In this invention, the organic fertilizer is purchased externally and only needs to meet the organic fertilizer standards in "Organic Fertilizer" (NY525-2021).

[0025] In this invention, the mass ratio of biochar to organic fertilizer is preferably 4 to 6:1, and more preferably 5:1.

[0026] This invention also provides a method for preparing the biochar-containing soil conditioner described in the above technical solution, comprising the following steps:

[0027] The biochar and organic fertilizer are mixed to obtain a soil conditioner containing biochar.

[0028] The present invention does not specifically limit the mixing process; any mixing process well known in the art can be used to mix the materials evenly.

[0029] The present invention also provides the application of the soil conditioner containing biochar described in the above technical solution or the soil conditioner containing biochar prepared by the preparation method described in the above technical solution in the remediation of soil in ion-type rare earth tailings waste sites.

[0030] In this invention, the mass of the soil conditioner containing biochar is preferably 5-7% of the dry weight of the soil in the ion-type rare earth tailings waste site, more preferably 6%.

[0031] This invention does not impose any particular limitation on the application of the biochar-containing soil conditioner in the remediation of soil in ion-type rare earth tailings waste sites; the method can be selected according to the actual situation.

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0033] Example 1

[0034] The Liriodendron tulipifera biomass was placed in a well-type vacuum furnace with a vacuum degree of 300 Pa and raised to 500 °C within 50 min at a rising rate of 10 °C / min for anaerobic carbonization for 60 min. The resulting Liriodendron tulipifera biochar was then ground by a disc mill and passed through a 10-100 mesh sieve to obtain biochar with a particle size of 0.15-2 mm.

[0035] Biochar and organic fertilizer (purchased from the market and conforming to NY525-2021 standard) were mixed in mass ratios of 2:1, 4:1, 6:1, 8:1, and 10:1 to obtain soil conditioners containing biochar.

[0036] Example 2

[0037] The Liriodendron tulipifera biomass was placed in a well-type vacuum furnace with a vacuum degree of 300 Pa and raised to 500 °C within 50 min at a rising rate of 10 °C / min for anaerobic carbonization for 60 min. The resulting Liriodendron tulipifera biochar was then ground by a disc mill and passed through a 10-100 mesh sieve to obtain biochar with a particle size of 0.15-2 mm.

[0038] Biochar and organic fertilizer (purchased from the market and conforming to NY525-2021 standard) are mixed at a mass ratio of 5:1 to obtain a soil conditioner containing biochar.

[0039] Example 3

[0040] Rice husks were placed in a well-type vacuum furnace with a vacuum degree of 300 Pa and raised to 500 °C in 50 min at a rising rate of 10 °C / min for anaerobic carbonization for 60 min. The resulting rice husk biochar was then ground by a disc mill and passed through a 10-100 mesh sieve to obtain biochar with a particle size of 0.15-2 mm.

[0041] Biochar and organic fertilizer (purchased from the market and conforming to NY525-2021 standard) are mixed at a mass ratio of 5:1 to obtain a soil conditioner containing biochar.

[0042] Comparative Example 1

[0043] The difference from Example 2 is that the biochar is made by carbonization and pulverization without sieving, but the rest is the same as Example 2.

[0044] Comparative Example 2

[0045] The difference from Example 3 is that the biochar is made by carbonization and pulverization without sieving, but the rest is the same as Example 3.

[0046] Application Example 1

[0047] The remediation soil samples were taken from a rare earth tailings waste site in Jingnao Township, Dingnan County. This waste site, an area where rare earth mining tailings had accumulated, had been abandoned for over 20 years. The soil structure was severely damaged, with extremely poor water and fertilizer retention capacity, making it virtually impossible for any type of plant to grow on the slopes. Soil samples from the 0-20cm layer were air-dried indoors before being used for indoor potted plant experiments.

[0048] The soil physicochemical properties are analyzed as follows:

[0049] Table 1 Soil structural properties

[0050]

[0051] Table 2 Soil physicochemical properties

[0052]

[0053] Each plastic flowerpot was weighed 1 kg. The test seeds were soaked in 75% (volume ratio) ethanol for 3 minutes and then rinsed three times with sterile water. 30 seeds were evenly sown in each pot. After germination, seedlings were thinned, leaving 20 uniformly growing plants per pot. Soil conditioners containing biochar (with biochar to organic fertilizer ratios of 2:1, 4:1, 6:1, 8:1, and 10:1 from Example 1) were added to the rare earth tailings to be remediated, with the organic fertilizer accounting for 1% of the soil dry weight. These were grouped as A2, A4, A6, A8, and A10. The control group (CK) was not included. The plants were placed in an artificial climate chamber at a controlled temperature of 27°C. Water was added every 2 days, weighed, and the soil moisture content was maintained at 70%. Pruning was performed 25 days after planting, resulting in plants 9 cm above the ground. Harvesting was done every 10 days thereafter, with ryegrass harvested after 55 days.

[0054] Application Example 2

[0055] The difference from Application Example 1 is that the soil conditioner containing biochar with a biochar to organic fertilizer mass ratio of 5:1 in Example 2 and the soil conditioner containing biochar with an undefined particle size range in Comparative Example 1 were applied to the rare earth tailings to be remediated at 1% of the dry weight of the organic fertilizer. They were respectively grouped as FB and WFB, with no addition as the control group CK. The rest of the contents are the same as in Application Example 1.

[0056] Application Example 3

[0057] The difference from Application Example 1 is that the soil conditioner containing biochar with a biochar-to-organic fertilizer mass ratio of 5:1 in Example 3 and the soil conditioner containing biochar with an undefined particle size range in Comparative Example 2 were applied to the rare earth tailings to be remediated at 1% of the soil dry weight of organic fertilizer, and were respectively grouped as DFB and DWFB. The control group CK was set as no addition. The rest of the contents are the same as Application Example 1.

[0058] Performance testing

[0059] (1) After harvesting the ryegrass plants in Example 1, they were placed in an oven at 105°C for 1 hour to kill the enzymes. Then, the oven temperature was adjusted to 80°C and dried to a constant weight. After cooling to room temperature, they were weighed. The results are as follows: Figure 1 As shown.

[0060] Depend on Figure 1 It can be seen that, compared with the control group, the average dry weight of ryegrass increased by about 5% after applying the soil conditioner containing biochar according to this invention; the biomass growth of ryegrass began to slow down when the biochar to organic fertilizer mass ratio was 6:1 and the addition amount was 7% of the soil dry weight. In summary, under the premise of ensuring economic efficiency, the optimal remediation effect can be obtained when the biochar to organic fertilizer mass ratio is in the range of 4 to 6:1 and the addition amount is in the range of 5 to 7%.

[0061] (2) After harvesting the ryegrass plants in Example 2, they were placed in an oven at 105°C for 1 hour to kill the enzymes. Then, the oven temperature was adjusted to 80°C and dried to a constant weight. After cooling to room temperature, they were weighed. The results are as follows: Figure 2 As shown.

[0062] Depend on Figure 2 It can be seen that after the remediation agent was added to the soil of rare earth tailings waste site, the growth of ryegrass was significantly improved and the biomass was greatly increased. In addition, the remediation agent containing fixed particle size biochar was more effective. The average dry weight of ryegrass in the group containing fixed particle size biochar was 20.96% higher than that in the group containing soil conditioner containing undefined particle size biochar.

[0063] (3) After harvesting the ryegrass plants in Example 3, they were placed in an oven at 105℃ for 1 hour to kill the enzymes, then the oven temperature was adjusted to 80℃ to dry to a constant weight. After cooling to room temperature, they were weighed. The results are as follows: Figure 3 As shown.

[0064] Depend on Figure 3 It was found that the addition of a remediation agent containing biochar of a fixed particle size to the soil of rare earth tailings waste sites resulted in better ryegrass growth. The average dry weight of ryegrass in the DFB remediation agent group (containing biochar of a fixed particle size) was 13.07% higher than that in the DWFB soil conditioner group (containing biochar of an undefined particle size range).

[0065] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. The application of a soil conditioner containing biochar in the remediation of soil from ion-adsorption rare earth tailings waste sites, characterized in that, The soil conditioner containing biochar is composed of biochar and organic fertilizer; the particle size of the biochar is 0.15~2mm; The mass ratio of biochar to organic fertilizer is 4-6:1; The mass of the soil conditioner containing biochar is 5-7% of the dry weight of the soil in the ion-type rare earth tailings waste site.

2. The application according to claim 1, characterized in that, The method for preparing biochar is as follows: the biomass raw material is subjected to anaerobic carbonization, crushing and sieving in sequence to obtain biochar.

3. The application according to claim 1, characterized in that, The anaerobic carbonization temperature is 450~550℃, and the holding time is 50~70min.

4. The application according to claim 2 or 3, characterized in that, The rate of heating to the anaerobic carbonization temperature is 8~12℃ / min.

5. The application according to claim 2, characterized in that, The biomass raw materials include tulip trees and / or rice husks.

6. The application according to claim 1, characterized in that, The method for preparing the soil conditioner includes the following steps: The biochar and organic fertilizer are mixed to obtain a soil conditioner containing biochar.

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