An enhanced remediation method for heavy metal contaminated soil through activation-enrichment-passivation

Abstract

This invention discloses a combined activation-enrichment-passivation enhanced remediation technology for heavy metal contaminated soil. A biomass activator is prepared using substandard fruit trees and fruit peels as biomass solid waste. This biomass activator is used to activate heavy metals in the contaminated soil. Heavy metals are then extracted from the soil through enrichment by native wild dominant plants. Biochar prepared from the solid residue after activator extraction and zeolite synthesized from coal gangue are used to passivate and stabilize the heavy metals remaining in the soil after phytoremediation. This technology, employing the combined use of biomass activator activation, phytoremediation, and passivation, effectively treats heavy metal pollution in soil, improves remediation efficiency, reduces remediation costs, and simultaneously achieves solid waste resource utilization and soil pollution remediation.

Description

Technical Field

[0001] This invention belongs to the field of soil heavy metal pollution remediation technology, specifically involving a combined enhanced remediation method for heavy metal contaminated soil through activation, enrichment, and passivation. Background Technology

[0002] With the acceleration of urbanization and industrialization, human activities have released large amounts of pollutants into the soil, leading to soil pollution, among which heavy metal pollution is particularly prominent. Heavy metals in farmland soil not only affect crop yield and quality but also threaten human health through the food chain. Faced with the severe situation of soil pollution, how to remediate soil heavy metal pollution has become a hot research topic in the fields of agriculture, ecology, and environmental science. To achieve the sustainable use of farmland and ensure that humans have access to sufficient and safe food, it is urgent to research and propose economical, efficient, and feasible soil heavy metal pollution remediation technologies.

[0003] In the field of heavy metal contaminated soil remediation technologies, traditional physical remediation techniques typically involve large-scale engineering projects and high remediation costs. Chemical remediation techniques, such as chemical activation and chemical leaching, use chelating agents and chemical leaching agents that pose a risk of secondary pollution and can damage soil structure and cause nutrient loss. Phytoremediation suffers from low availability of heavy metals in the soil, limited absorption and accumulation of heavy metals by plants, and time-consuming remediation processes. These shortcomings and deficiencies have prompted researchers to continuously seek new remediation technologies and methods. Developing novel, highly selective, low-residue, and low-side-effect biodegradable chelating agents or low-molecular-weight organic acids to replace the widely used, recalcitrant chelating agents such as EDTA in current chemical activation techniques, and developing technologies to utilize biological waste and industrial waste residues to prepare porous, high-adsorption-performance biochar and zeolite molecular sieves for solid waste resource recovery, are currently important directions for breakthroughs in environmental remediation. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a combined enhanced remediation technology for heavy metal contaminated soil, comprising:

[0007] Biomass solid waste is pretreated to obtain activator A, passivator B, and passivator C;

[0008] Activator A was used to activate the soil contaminated with heavy metals.

[0009] Next, native wild dominant plants were used to enrich the activated heavy metal contaminated soil.

[0010] Finally, a composite passivating agent consisting of passivating agent B, passivating agent C and gangue-based zeolite was used to passivate the enriched heavy metal contaminated soil, thus achieving the combined enhanced remediation of heavy metal contaminated soil.

[0011] The biomass solid waste consists of substandard fruit trees and peels, and the pretreatment method includes...

[0012] Cleaned and damaged fruit trees and peels are crushed into biomass solid waste powder.

[0013] Biomass solid waste powder and deionized water are mixed at a ratio of 2-5 mL of deionized water per 1 g of biomass solid waste powder, shaken at 20-25℃ for 30-50 minutes, and centrifuged for 30-50 minutes to obtain mixture I;

[0014] Mixture I is filtered to obtain supernatant and solid residue, wherein the supernatant is activator A;

[0015] The solid residue is washed, dried, pyrolyzed at 400~600℃ for 2~4 h, ground and sieved to obtain fruit pomace biochar, which is passivating agent B;

[0016] Fruit pomace biochar B is mixed with a phosphorus-containing solution and stirred at 60-80℃ for 2-4 hours. The filter cake obtained by vacuum filtration is dried at 80-110℃ for 12-36 hours to obtain modified fruit pomace biochar, which is passivating agent C.

[0017] As a preferred embodiment of the activation-enrichment-passivation combined enhanced remediation technology for heavy metal contaminated soil described in this invention, wherein: the activation treatment method includes,

[0018] Activator A is added to heavy metal contaminated soil at a concentration of 5-20%, and the solid-liquid ratio of contaminated soil to activator A is 1:1-5 (g / mL). The mixture is then thoroughly mixed.

[0019] Cultivate at room temperature for 30-60 days, maintaining soil moisture content at 65%-70% of field capacity.

[0020] As a preferred embodiment of the combined enhanced remediation technology for heavy metal contaminated soil activation-enrichment-passivation as described in this invention, the native wild dominant plants include wild Artemisia argyi and Bidens pilosa.

[0021] As a preferred embodiment of the combined enhanced remediation technology for heavy metal contaminated soil activation-enrichment-passivation described in this invention, the enrichment treatment method involves extracting heavy metals from the activated soil through artificial intercropping and rotation of native wild dominant plants.

[0022] As a preferred embodiment of the combined enhanced remediation technology for heavy metal contaminated soil activation-enrichment-passivation described in this invention, the mass ratio of phosphorus-containing solids in the phosphorus-containing solution to fruit pomace biochar is 1:5 to 1:10.

[0023] As a preferred embodiment of the activation-enrichment-passivation combined enhanced remediation technology for heavy metal contaminated soil described in this invention, the phosphorus-containing solution includes K3PO4 solution or nano-hydroxyapatite suspension, and the solid-liquid ratio of phosphorus-containing solid to deionized water in the phosphorus-containing solution is 1:5 (g / mL).

[0024] As a preferred embodiment of the enhanced remediation technology for heavy metal contaminated soil by activation-enrichment-passivation as described in this invention, the method for preparing the gangue-based zeolite is as follows:

[0025] Coal gangue is crushed and ground into 150-200 mesh powder, mixed with concentrated hydrochloric acid at a ratio of 1:10 (g / mL), and heated to dryness at 60-80℃;

[0026] Coal gangue powder and NaOH are mixed at a mass ratio of 1:1 to 1:1.2 and melted at 600 to 650°C for 2 to 3 hours to obtain an alkali fusion product.

[0027] The alkali fusion product was mixed with deionized water at a ratio of 1:6 to 10 (g / mL), sonicated for 0.5 h to 1 h, and then centrifuged.

[0028] Sodium silicate was added to the supernatant to adjust the SiO2 / Al2O3 ratio, and the mixture was stirred and aged at room temperature for 12–18 h.

[0029] Crystallization, filtration, water washing, and drying yield gangue-based zeolite.

[0030] As a preferred embodiment of the activation-enrichment-passivation combined enhanced remediation technology for heavy metal contaminated soil described in this invention, wherein the SiO2 / Al2O3 ratio is 4 to 10.

[0031] As a preferred embodiment of the enhanced remediation technology for heavy metal contaminated soil by activation-enrichment-passivation as described in this invention, the crystallization temperature is 90-100℃ and the time is 12-24 h.

[0032] As a preferred embodiment of the activation-enrichment-passivation combined enhanced remediation technology for heavy metal contaminated soil described in this invention, the total content of passivating agent B, passivating agent C and gangue-based zeolite is 6% to 9% of the heavy metal contaminated soil.

[0033] Beneficial effects of this invention:

[0034] (1) The biomass activator activation technology provided by the present invention can increase the potential bioavailability of heavy metals in the soil by 55% to 70%, and the remediation technology of enriching and extracting heavy metals by native wild dominant plants can increase the ability of plants to enrich and transport heavy metals by 50% to 80%. It can overcome the problems of low bioavailability of heavy metals in the soil, small amount of plant absorption and enrichment, and long time required for treatment and remediation in the current phytoremediation of heavy metal contaminated soil.

[0035] (2) The combined enhanced remediation technology for heavy metal contaminated soil activation-enrichment-passivation provided by the present invention can efficiently solve the heavy metal pollution of soil. The raw materials for the preparation of activator and biochar are derived from the residual fruit wood and fruit peel biomass solid waste of the fruit industry, and the raw materials for synthesizing zeolite are derived from coal gangue, a solid waste of mining. This technology is highly efficient, effective and low cost in solving the problem of heavy metal pollution in soil, and can also realize the resource utilization of biomass solid waste and mining solid waste. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0037] Figure 1 This is a potted experiment photograph of the enrichment and extraction of heavy metals from soil treated with a biomass activator by wild Artemisia argyi in Example 1 of the present invention.

[0038] Figure 2 This is a SEM image of the fruit pomace biochar used for passivation repair in Example 1 of the present invention.

[0039] Figure 3 This is a SEM image of the gangue-based zeolite used for passivation repair in Example 1 of the present invention.

[0040] Figure 4 This is a SEM image of the modified fruit pomace biochar used for passivation repair in Example 1 of the present invention.

[0041] Figure 5 This is a SEM image of the modified fruit pomace biochar used for passivation repair in Example 2 of the present invention.

[0042] Figure 6This is a potted plant experiment in Example 2 of the present invention, which showed the enrichment and extraction of heavy metals from soil treated with a biomass activator by Bidens pilosa. Detailed Implementation

[0043] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0044] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0045] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0046] Unless otherwise specified, all raw materials used in this invention are commercially available in the field.

[0047] The coal gangue used in this invention was collected from Xiayukou Coal Mine in Hancheng, Shaanxi Province. The chemical composition of the original coal gangue and the coal gangue after acid dissolution and alkali fusion treatment in Example 1 is shown in Table 1.

[0048] Table 1 Chemical composition of coal gangue

[0049] Element(%) <![CDATA[Na2O]]> <![CDATA[K2O]]> CaO MgO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> <![CDATA[TiO2]]> LOI Before processing 0.35 0.85 0.39 0.24 35.14 18.14 1.63 0.46 19.80 After processing 0.34 0.66 0.06 0.16 60.01 10.43 0.10 0.06 0.13

[0050] The soils used in Examples 1 and 2 of this invention were collected from farmland in Ziwu Town, Chang'an District, Xi'an City, Shaanxi Province. The soil pH was 7.8, the organic matter content was 14.1 g / kg, the available nitrogen content was 60 mg / kg, the available phosphorus content was 10 mg / kg, and the available potassium content was 143 mg / kg. The Pb-contaminated soil was artificially contaminated by adding lead nitrate solution and aged at room temperature for 90 days at 70% soil field capacity.

[0051] The contaminated soil in Example 3 of this invention was collected from farmland surrounding a zinc smelter in Shangluo City, Shaanxi Province. The basic physicochemical properties and heavy metal content of the soil are shown in Table 2.

[0052] Table 2. Physicochemical properties, major components, and heavy metal content of contaminated soil in Example 3.

[0053] pH LOI (%) Clay particles (%) Silt (%) Sand particles (%) CaO <![CDATA[K2O]]> <![CDATA[Na2O]]> 8.3 12.3 17.7 56.0 26.3 0.9 1.5 2.0 MgO <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> <![CDATA[SiO2]]> Cu Pb Zn Cd 1.8 6.7 7.8 33.1 130.8 495.5 3678.7 4.6

[0054] Note: The units for the content of constant components are %; the units for the content of heavy metals (Cu, Pb, Zn and Cd) are mg / kg.

[0055] Example 1

[0056] This embodiment provides a combined enhanced remediation technology for heavy metal contaminated soil, including:

[0057] 1. Pretreatment of biomass solid waste

[0058] The cleaned defective Fuji apples are crushed to obtain apple pulp powder;

[0059] Add deionized water at a ratio of apple pomace to deionized water of 1:2 (g / mL), shake at 25°C for 30 minutes, centrifuge for 30 minutes to obtain mixture I;

[0060] Mixture I is filtered to obtain supernatant and solid residue, wherein the supernatant is activator A;

[0061] The solid residue was washed with deionized water, dried in an oven at 80°C to constant weight, and then placed in an oven at 105°C for 2 hours. It was then transferred to a muffle furnace and pyrolyzed at 400°C for 4 hours to obtain fruit pomace biochar, which is passivating agent B. It was ground through a 60-mesh sieve and sealed for storage.

[0062] K3PO4 was added to deionized water at a solid-liquid ratio of 1:5 (g / mL) and sonicated for 0.5 h to obtain a K3PO4 solution. Fruit pomace biochar B was added to the K3PO4 solution and stirred in an 80℃ water bath for 2 h at a mass ratio of 1:5. The mixture was then filtered and dried in a constant temperature oven at 80℃ for 36 h to obtain modified fruit pomace biochar, which is passivating agent C.

[0063] 2. Preparation of gangue-based zeolite

[0064] Coal gangue was crushed and ground into 150-mesh powder, mixed with concentrated hydrochloric acid at a ratio of 1:10 (g / mL), and heated to dryness at 60°C in a constant temperature water bath. The coal gangue powder was mixed with NaOH at a mass ratio of 1:1 and melted in a muffle furnace at 600°C for 3 h. The alkali-fused product was mixed with deionized water at a ratio of 1:6 (g / mL), sonicated for 0.5 h, and centrifuged. Sodium silicate was added to the supernatant to adjust the SiO2 / Al2O3 ratio to 6, and the mixture was magnetically stirred and aged at room temperature for 12 h. The mixture was then transferred to a hydrothermal synthesis reactor and placed in a constant temperature oven at 90°C for crystallization for 24 h. The crystallized product was filtered, washed with water, and dried to obtain gangue-based zeolite.

[0065] 3. Heavy metal soil remediation

[0066] 3.1 Activation treatment:

[0067] Add 5% activator A to Pb-contaminated soil (850 mg / kg), with a solid-liquid ratio of 1:1 (g / mL) between the contaminated soil and activator A, and mix thoroughly.

[0068] Cultivate at room temperature for 30 days, adding water every 3 days to maintain the soil moisture content at 65% of field capacity.

[0069] 3.2 Plant enrichment and extraction treatment:

[0070] Through pot experiments, heavy metals in the activated soil were extracted using wild Artemisia argyi. During the plant's growth period, it was regularly irrigated. The plants were sown in spring and harvested in autumn, with both the above-ground and underground parts harvested together, for a two-round planting and restoration process.

[0071] 3.3 Passivation treatment:

[0072] Pb in soil that has undergone phytoaccumulation and extraction was passivated using 2% passivating agent B, 2% passivating agent C, and 2% gangue-based zeolite.

[0073] The process included activation treatment, plant enrichment and extraction treatment, and passivation treatment. At the same time, corresponding control experiments were carried out, with the control group consisting of untreated contaminated soil.

[0074] Figure 1 This is a photograph of a potted plant experiment in this embodiment on the enrichment and extraction of heavy metals from soil treated with a biomass activator by wild Artemisia argyi.

[0075] Figure 2 This is a SEM image of the pomace biochar used for passivation repair in this embodiment.

[0076] Figure 3 This is a SEM image of the gangue-based zeolite used for passivation repair in this embodiment.

[0077] Figure 4 This is a SEM image of the modified fruit pomace biochar used for passivation repair in this embodiment.

[0078] After activation treatment with activator A, the potential bioavailable phosphorus (Pb) in the soil reached 76%. In the phytoencapsulation extraction treatment, wild Artemisia argyi showed an enrichment coefficient of 1.7 and a translocation coefficient of 1.1 for Pb. After passivation treatment, the content of potential bioavailable Pb in the soil decreased by 62% compared with the unpassivated control group.

[0079] Example 2

[0080] This embodiment provides a combined enhanced remediation technology for heavy metal contaminated soil, including:

[0081] 1. Pretreatment of biomass solid waste

[0082] The cleaned defective Fuji apples were crushed and added to deionized water at a ratio of apple pomace to deionized water of 1:3 (g / mL). The mixture was shaken at 20°C for 50 minutes and then centrifuged for 50 minutes to obtain mixture I.

[0083] Mixture I is filtered, and the supernatant and solid residue are collected. The supernatant is activator A.

[0084] The solid residue was washed with deionized water, dried in an oven at 80°C to constant weight, and then placed in an oven at 105°C for 2 hours. It was then transferred to a muffle furnace and pyrolyzed at 600°C for 2 hours to obtain fruit pomace biochar, which is passivating agent B. It was ground through a 60-mesh sieve and sealed for storage.

[0085] Nano-hydroxyapatite was added to deionized water at a solid-liquid ratio of 1:10 (g / mL) and sonicated for 1 h to obtain a nano-hydroxyapatite suspension. Passivating agent B was added to the nano-hydroxyapatite suspension and stirred in a 60℃ water bath for 4 h at a mass ratio of 1:10 between the nano-hydroxyapatite suspension and the fruit pomace biochar. The mixture was then filtered and dried in a constant temperature oven at 100℃ for 24 h to obtain modified fruit pomace biochar, which is the passivating agent C.

[0086] 2. Preparation of gangue-based zeolite

[0087] Coal gangue was crushed and ground into 200-mesh powder, mixed with concentrated hydrochloric acid at a ratio of 1:10 (g / mL), and heated to dryness at 80°C in a constant temperature water bath. The coal gangue powder was mixed with solid NaOH at a mass ratio of 1:1.2 and melted in a muffle furnace at 650°C for 2 h. The alkali-fused product was mixed with deionized water at a ratio of 1:8 (g / mL), sonicated for 1 h, and centrifuged. Sodium silicate was added to the supernatant to adjust the SiO2 / Al2O3 ratio to 8, and the mixture was magnetically stirred and aged at room temperature for 12 h. The mixture was then transferred to a hydrothermal synthesis reactor and placed in a constant temperature oven at 100°C for crystallization for 12 h. The crystallized product was filtered, washed with water, and dried to obtain gangue-based zeolite.

[0088] 3. Remediation of heavy metal contaminated soil

[0089] 3.1 Activation treatment:

[0090] Add 10% of activator A to the Pb-contaminated soil (850 mg / kg), with a solid-liquid ratio of 1:5 (g / mL) between the contaminated soil and activator A, and mix thoroughly.

[0091] Cultivate at room temperature for 60 days, adding water every 3 days to maintain the soil moisture content at 70% of field capacity.

[0092] 3.2 Enrichment and Extraction Processing:

[0093] Heavy metals were extracted from soil treated with activator A using Bidens pilosa in pot experiments. The plants were watered regularly during their growth period. Both above-ground and below-ground parts of the plants were harvested in spring and autumn. Two rounds of replanting were conducted for remediation.

[0094] 3.3 Passivation treatment:

[0095] Pb in soil that has undergone phytoencapsulation and extraction was passivated using 3% passivating agent B, 3% passivating agent C, and 3% gangue-based zeolite.

[0096] The process included activation treatment, plant enrichment and extraction treatment, and passivation treatment. At the same time, corresponding control experiments were carried out, with the control group consisting of untreated contaminated soil.

[0097] Figure 5 This is a SEM image of the modified fruit pomace biochar used for passivation repair in this embodiment.

[0098] Figure 6 This is a photograph of a potted plant experiment in this embodiment on the enrichment and extraction of heavy metals from soil treated with a biomass activator by Bidens pilosa.

[0099] After activation treatment with activator A, the potential bioavailable phosphorus (Pb) in the soil reached 88%. In the plant enrichment and extraction treatment, the enrichment coefficient of Bidens pilosa for Pb was 1.9, and the translocation coefficient was 1.6. After passivation treatment, the content of potential bioavailable Pb in the soil decreased by 70% compared with the unpassivated control group.

[0100] Example 3

[0101] This embodiment provides a combined enhanced remediation technology for heavy metal contaminated soil, including:

[0102] 1. Pretreatment of biomass solid waste

[0103] The cleaned and damaged pineapple peels were crushed and added to deionized water at a ratio of 1:3 (g / mL). The mixture was shaken at 25°C for 30 minutes and then centrifuged for 50 minutes to obtain mixture I.

[0104] Mixture I is filtered to obtain supernatant and solid residue, wherein the supernatant is activator A;

[0105] The solid residue was washed with deionized water, dried in an oven at 80°C to constant weight, and then placed in an oven at 105°C for 2 hours. It was then transferred to a muffle furnace and pyrolyzed at 500°C for 3 hours to obtain pineapple peel residue biochar, which is passivating agent B. It was ground through a 60-mesh sieve and sealed for storage.

[0106] Nano-hydroxyapatite was added to deionized water at a solid-liquid ratio of 1:5 (g / mL) and sonicated for 1 h to obtain a nano-hydroxyapatite suspension. Fruit pomace biochar was added to the nano-hydroxyapatite suspension at a mass ratio of 1:8 and stirred in a 70℃ water bath for 4 h. The mixture was then filtered and dried in a constant temperature oven at 90℃ for 36 h to obtain modified pineapple pomace biochar, which is passivating agent C.

[0107] 2. Remediation of heavy metal contaminated soil

[0108] 2.1 Activation treatment:

[0109] 20% of activator A was added to soil contaminated with Cu, Pb, Zn, and Cd. The contents of Cu, Pb, Zn, and Cd were 130.8 mg / kg, 495.5 mg / kg, 3678.7 mg / kg, and 4.6 mg / kg, respectively. The solid-liquid ratio of the contaminated soil to activator A was 1:5 (g / mL), and the mixture was thoroughly mixed.

[0110] Cultivate at room temperature for 60 days, adding water every 3 days to maintain soil moisture content at 70% of field capacity;

[0111] 2.2 Enrichment and Extraction Processing:

[0112] Through pot experiments, heavy metals in soil treated with activator A were extracted using wild Artemisia argyi and Bidens pilosa. During the plant growth period, the plants were watered regularly. The plants were sown in spring and harvested in autumn, with both the above-ground and underground parts harvested together. Two rounds of remediation were carried out: the first round was planted with wild Artemisia argyi, and the second round was planted with Bidens pilosa.

[0113] 2.3 Passivation treatment:

[0114] Heavy metals in soil that has undergone phytoaccumulation and extraction were passivated using 8% passivating agent C.

[0115] The process included activation treatment, plant enrichment and extraction treatment, and passivation treatment. At the same time, corresponding control experiments were carried out, with the control group consisting of untreated contaminated soil.

[0116] After activation treatment with activator A, the potential bioavailability of Cu, Pb, Zn, and Cd in the soil reached 72%, 90%, 84%, and 81%, respectively. In the phytoencular enrichment extraction treatment, the enrichment coefficients of wild Artemisia argyi for Cu, Pb, Zn, and Cd were 1.4, 1.3, 1.5, and 2.6, respectively, and the translocation coefficients were 1.5, 1.1, 1.6, and 4.5, respectively; while those of Bidens pilosa for Cu, Pb, Zn, and Cd were 1.5, 1.6, 1.3, and 2.1, respectively, and the translocation coefficients were 1.3, 1.1, 1.4, and 2.5, respectively. After passivation treatment, the contents of potential bioavailability of Cu, Pb, Zn, and Cd in the soil decreased by 55%–72% compared to the unpassivated control group.

[0117] Comparative Example 1

[0118] The difference between this comparative example and Example 1 is that no activation or passivation treatment was performed; only plant enrichment treatment was performed.

[0119] Through pot experiments, Pb (850 mg / kg) was extracted from Pb-contaminated soil using wild Artemisia argyi. During the plant's growth period, it was regularly irrigated. The plants were sown in spring and harvested in autumn, with both above-ground and below-ground parts harvested together, for a two-round remediation process.

[0120] The bioavailability of Pb in the soil of this comparative example without activation treatment with activator A was 21%, which was 55% lower than that in the soil of Example 1 that was activated with activator A. The enrichment coefficient of wild Artemisia argyi for Pb was 0.9 and the translocation coefficient was 0.7, which were only 53% and 64% of the enrichment coefficient and translocation coefficient of Example 1, respectively.

[0121] As can be seen, the activation treatment of activator A in Example 1 can effectively improve the bioavailability of Pb in the soil, promote the enrichment and translocation of Pb in the polluted soil by wild Artemisia argyi, and improve the efficiency of Pb-polluted soil enrichment, extraction and remediation by wild Artemisia argyi. Compared with the comparative example, it can shorten the remediation time of polluted soil by 47%.

[0122] Comparative Example 2

[0123] The difference between this comparative example and Example 2 is that no activation or passivation treatment was performed; only plant enrichment treatment was performed.

[0124] Through pot experiments, Pb (850 mg / kg) was extracted from Pb-contaminated soil using Bidens pilosa. During the plant's growth period, it was regularly irrigated. The plants were sown in spring and harvested in autumn, with both above-ground and below-ground parts harvested together, for a two-round remediation planting process.

[0125] In this comparative example, the bioavailability of Pb in the soil without activator A was 21%, which is 67% lower than that in the soil treated with activator A in Example 2. The enrichment coefficient of Bidens pilosa for Pb was 1.1, and the translocation coefficient was 0.9, only 58% and 56% of the enrichment coefficient and translocation coefficient in Example 2, respectively. Therefore, the activation treatment with activator A in Example 2 can effectively improve the bioavailability of Pb in the soil, promote the enrichment and translocation of Pb in contaminated soil by Bidens pilosa, and improve the efficiency of Pb enrichment, extraction, and remediation of Pb-contaminated soil. Compared with this comparative example, it can shorten the remediation time of contaminated soil by 42%.

[0126] Comparative Example 3

[0127] The difference between this comparative example and Example 3 is that no activation or passivation treatment was performed; only plant enrichment treatment was performed.

[0128] Pot experiments were conducted to extract Cu, Pb, Zn, and Cd from soil contaminated with a mixture of Cu, Pb, Zn, and Cd (containing 130.8 mg / kg, 495.5 mg / kg, 3678.7 mg / kg, and 4.6 mg / kg, respectively). The plants were regularly irrigated during their growth period. Plants were sown in spring and harvested in autumn, with both above-ground and below-ground parts harvested together. Two rounds of remediation planting were carried out: the first round planting wild Artemisia argyi, and the second round planting Bidens pilosa.

[0129] In this comparative example, the bioavailability of Cu, Pb, Zn, and Cd in the untreated soil was 21%, 20%, 24%, and 23% of their total values, respectively, which was 51%, 70%, 60%, and 58% lower than that in the biotreated soil of Example 3. The enrichment coefficients of wild Artemisia for Cu, Pb, Zn, and Cd were 0.8, 0.7, 0.9, and 1.5, respectively, only 57%, 54%, 60%, and 58% of those in Example 3; the translocation coefficients were 0.9, 0.6, 1.0, and 2.5, respectively, only 60%, 55%, 62%, and 56% of those in Example 3. The enrichment coefficients of Bidens pilosa for Cu, Pb, Zn and Cd were 0.9, 1.0, 0.8 and 1.3, respectively, which were only 60%, 63%, 62% and 62% of the enrichment coefficients in Example 3; the translocation coefficients were 0.8, 0.7, 1.0 and 1.5, respectively, which were only 62%, 64%, 71% and 60% of the enrichment coefficients in Example 3.

[0130] As can be seen, the activation treatment of activator A in Example 3 can effectively improve the bioavailability of Cu, Pb, Zn and Cd in the soil, promote the enrichment and translocation of Cu, Pb, Zn and Cd in the contaminated soil by wild Artemisia argyi and Bidens pilosa, and improve the efficiency of enrichment, extraction and remediation of Cu, Pb, Zn and Cd combined contaminated soil by wild Artemisia argyi and Bidens pilosa. Compared with the comparative example, it can shorten the remediation time of contaminated soil by 37% to 40%.

[0131] Comparative Example 4

[0132] The difference between this comparative example and Example 1 is that conventional EDTA is used as an activator for activation treatment, and no passivation treatment is performed. Other steps are the same as in Example 1. Heavy metal contaminated soil is then activated and subjected to phytoenyl enrichment treatment.

[0133] In this comparative example, the potential bioavailability of Pb in the soil after EDTA activation treatment reached 42%, which is 34% lower than the bioavailability of Pb in the soil activated by activator A in Example 1. The enrichment coefficient of wild Artemisia argyi for Pb was 1.1, and the translocation coefficient was 0.9, which are only 64% and 82% of the enrichment coefficient and translocation coefficient in Example 1, respectively. In Example 1, the mass fraction of activator A was only 5%, yet it achieved a significantly better effect than Comparative Example 3.

[0134] It is evident that activator A in Example 1 has a better promoting effect on the activation efficiency of Pb in contaminated soil than the conventional activator EDTA, thereby affecting the subsequent enrichment and translocation capacity of Pb in contaminated soil by wild Artemisia argyi.

[0135] In summary, the activation-enrichment-passivation combined enhanced remediation technology for heavy metal contaminated soil provided by this invention can efficiently solve soil heavy metal pollution. The raw materials for the preparation of activator and biochar come from the biomass solid waste of substandard fruit trees and fruit peels in the fruit industry, and the raw materials for synthesizing zeolite come from coal gangue, a solid waste from mining. This technology is highly efficient, effective, and low-cost in solving the problem of heavy metal pollution in soil, and can also realize the resource utilization of biomass solid waste and mining solid waste.

[0136] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A combined activation-enrichment-passivation enhanced remediation method for heavy metal contaminated soil, characterized in that: include, Biomass solid waste is pretreated to obtain activator A, passivator B, and passivator C; Activator A was used to activate the soil contaminated with heavy metals. The activation treatment includes adding activator A to the heavy metal contaminated soil, wherein the concentration of activator A is 5-20%, the solid-liquid ratio of the contaminated soil to activator A is 1:1-5 (g / mL), and mixing them evenly. Cultivate at room temperature for 30-60 days, maintaining soil moisture content at 65%-70% of field capacity; Next, native wild dominant plants were used to enrich the activated heavy metal contaminated soil. Finally, a composite passivating agent consisting of passivating agent B, passivating agent C and gangue-based zeolite was used to passivate the enriched heavy metal contaminated soil, thus achieving the combined enhanced remediation of heavy metal contaminated soil. The biomass solid waste consists of substandard fruit trees and peels, and the pretreatment method includes... Cleaned and damaged fruit trees and peels are crushed into biomass solid waste powder. Biomass solid waste powder and deionized water are mixed at a ratio of 2-5 mL of deionized water per 1 g of biomass solid waste powder, shaken at 20-25℃ for 30-50 minutes, and centrifuged for 30-50 minutes to obtain mixture I; Mixture I is filtered to obtain supernatant and solid residue, wherein the supernatant is activator A; The solid residue is washed, dried, pyrolyzed at 400~600℃ for 2~4 h, ground and sieved to obtain fruit pomace biochar, which is passivating agent B; Passivating agent B is mixed with a phosphorus-containing solution and stirred at 60-80℃ for 2-4 hours. The filter cake obtained by vacuum filtration is dried at 80-110℃ for 12-36 hours to obtain modified fruit pomace biochar, which is passivating agent C.

2. The method for enhanced remediation of heavy metal contaminated soil by activation-enrichment-passivation as described in claim 1, characterized in that: The native wild dominant plants include wild mugwort and beggar-ticks.

3. The method for enhanced remediation of heavy metal contaminated soil by activation-enrichment-passivation as described in claim 1, characterized in that: The enrichment treatment method involves extracting and enriching heavy metals from the activated soil through artificial intercropping and rotation of native wild dominant plants.

4. The method for enhanced remediation of heavy metal contaminated soil by activation-enrichment-passivation as described in claim 1, characterized in that: The mass ratio of phosphorus-containing solids in the phosphorus-containing solution to fruit pomace biochar is 1:5 to 1:

10.

5. The method for enhanced remediation of heavy metal contaminated soil by activation-enrichment-passivation as described in claim 4, characterized in that: The phosphorus-containing solution includes a K3PO4 solution or a nano-hydroxyapatite suspension, and the solid-liquid ratio of the phosphorus-containing solid to deionized water in the phosphorus-containing solution is 1:5 (g / mL).

6. The method for enhanced remediation of heavy metal contaminated soil by activation-enrichment-passivation as described in claim 1, characterized in that: The preparation method of the gangue-based zeolite is as follows: Coal gangue is crushed and ground into 150-200 mesh powder, mixed with concentrated hydrochloric acid at a ratio of 1:10 (g / mL), and heated to dryness at 60-80℃; Coal gangue powder and NaOH are mixed at a mass ratio of 1:1 to 1:1.2 and melted at 600 to 650°C for 2 to 3 hours to obtain an alkali fusion product. The alkali fusion product was mixed with deionized water at a ratio of 1:6 to 10 (g / mL), sonicated for 0.5 h to 1 h, and then centrifuged. Sodium silicate was added to the supernatant to adjust the SiO2 / Al2O3 ratio, and the mixture was stirred and aged at room temperature for 12–18 h. Crystallization, filtration, water washing, and drying yield gangue-based zeolite.

7. The method for enhanced remediation of heavy metal contaminated soil by activation-enrichment-passivation as described in claim 6, characterized in that: The SiO2 / Al2O3 ratio is 4 to 10.

8. The method for enhanced remediation of heavy metal contaminated soil by activation-enrichment-passivation as described in claim 6, characterized in that: The crystallization temperature is 90–100°C, and the time is 12–24 h.

9. The method for enhanced remediation of heavy metal contaminated soil by activation-enrichment-passivation as described in claim 1, characterized in that: The total content of passivating agent B, passivating agent C, and gangue-based zeolite is 6% to 9% of the heavy metal contaminated soil.

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