Self-adaptive charcoal-solid waste-based blocking and controlling material for rapid blocking and controlling of organic-heavy metal combined pollution

Abstract

The invention discloses a self-adaptive charcoal-solid waste-based prevention and control material for rapid prevention and control of organic-heavy metal combined pollution, and belongs to the technical field of pollution control materials. The preparation method of the material comprises the following steps: performing dry powder mixing on the sulfur-aluminum-iron series low-carbon cementing material, the auxiliary cementing material and the biochar to obtain a colloidal material; and mixing the colloidal material with in-situ soil, adding water, and stirring to form the biochar-solid waste-based pollution prevention and control material. Through biochar coupling, the water content of the system is optimized, the pore structure of the material is optimized, and the material forming time is shortened; the auxiliary cementing material promotes the hydration reaction of the material, so that the strength is higher, and the compactness is better; porous and functional groups of the biochar realize adsorption resistance and control on heavy metals and organic pollution.

Description

Technical Field

[0001] This invention belongs to the field of pollution control materials technology, specifically relating to adaptive biochar-solid waste-based control materials for rapid control of organic-heavy metal complex pollution. Background Technology

[0002] The main pollutants in soil pollution include heavy metals (such as lead, cadmium, arsenic, and mercury) and organic pollutants (such as polycyclic aromatic hydrocarbons, chlorinated hydrocarbons, and volatile organic compounds). Once these pollutants enter the soil environment, they are characterized by being difficult to degrade, easily migrating, and highly biotoxic. They not only threaten the safety of agricultural products but also enter groundwater through infiltration, further posing risks to the ecological environment and human health. Existing soil remediation technologies, such as excavation and landfill, solidification and stabilization, soil washing, and thermal treatment, can reduce pollutant levels to some extent, but they generally suffer from high remediation costs, significant damage to soil physicochemical properties, and limited applicability, making it difficult to meet the long-term risk management needs of complex sites.

[0003] Pollutant control materials, as a novel soil remediation method developed in recent years, can control the migration and exposure risks of pollutants under in-situ conditions. Their main mechanisms of action include: physical barrier effects by reducing soil porosity and permeability; chemical fixation through complexation, precipitation, or ion exchange with heavy metal ions; adsorption of organic and inorganic pollutants through specific surface area and porous structure; and reactive control through the slow release of active components to achieve reductive dechlorination of chlorinated organic compounds. Compared with traditional remediation methods, control materials offer advantages such as ease of operation, strong in-situ applicability, and minimal environmental disturbance, effectively delaying the risk of pollutants migrating downwards or entering the food chain.

[0004] Among various pollution control materials, cementitious materials based on the resource utilization of solid waste are gradually attracting attention. Using industrial solid wastes such as steel slag, fly ash, and blast furnace slag as raw materials to prepare cementitious materials can not only reduce material costs and improve sustainability, but also effectively immobilize various pollutants by forming a dense solidified body and complex hydration product phases. Among these, sulfur-aluminum-iron-based cementitious materials, rich in aluminum and iron active components, can generate structures such as hydrotalcite-like compounds and iron-aluminum hydroxyl salts during hydration, exhibiting strong adsorption and immobilization capabilities for heavy metal ions, while also possessing the potential for synergistic control of organic pollutants. Therefore, developing sulfur-aluminum-iron-based cementitious materials based on industrial solid waste provides a new technological path for achieving long-term and stable control of soil pollution.

[0005] However, existing sulfur-aluminum-iron-based cementitious materials have shortcomings in pollutant control (heavy metals, volatile organic compounds, etc.), including: limited early strength, insufficient pollutant blocking efficiency, and uncontrollable pore structure. Therefore, an adaptive biochar-solid waste-based control material for rapid control of organic-heavy metal complex pollution is proposed. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an adaptive biochar-solid waste-based control material for rapid control of organic-heavy metal complex pollution, thus solving the problems in existing technologies.

[0007] The objective of this invention can be achieved through the following technical solutions: A method for preparing biochar-solid waste-based pollution control materials includes the following steps: A colloidal material is obtained by dry mixing of sulfur-aluminum-iron-based low-carbon cementitious material, auxiliary cementitious material and biochar. After mixing the colloidal material with the in-situ soil, water is added and stirred to form a biochar-solid waste-based pollution control material.

[0008] Furthermore, the mass ratio of the sulfur-aluminum-iron-based low-carbon cementitious material to the auxiliary cementitious material is (85-95):(5-15).

[0009] Furthermore, the mass of the biochar is 1-3% of the sum of the mass of the sulfur-aluminum-iron-based low-carbon cementitious material and the auxiliary cementitious material.

[0010] Furthermore, the mass of the colloidal material accounts for 20-30% of the total mass of the in-situ soil and the colloidal material.

[0011] 5. The method for preparing a biochar-solid waste-based pollution control material according to claim 1, characterized in that the water-to-solid ratio in the biochar-solid waste-based pollution control material is 15-20%.

[0012] Furthermore, the sulfur-aluminum-iron-based low-carbon cementitious material comprises the following raw materials in weight percentages: 35-45% CaO, 20-30% Al2O3, 6-15% Fe2O3, 8-15% SO3, and 4-12% SiO2.

[0013] Furthermore, the auxiliary cementing material includes one or more of the following: slag, fly ash or silica fume, steel slag, etc.

[0014] Biochar-based pollution control material is prepared using the above-described preparation method.

[0015] The above-mentioned biochar-solid waste-based pollution control materials are used in soil pollution management or remediation.

[0016] A building casting material, comprising the above-mentioned biochar-solid waste-based pollution control material.

[0017] The beneficial effects of this invention are: 1. By coupling with biochar, the water content of the system is optimized, the pore structure of the material is optimized, and the molding time of the material is shortened; the auxiliary cementing material promotes the hydration reaction of the material, resulting in higher strength and better density; the porosity and functional groups of biochar achieve adsorption and control of heavy metals and organic pollutants.

[0018] 2. The present invention controls the mass ratio of sulfur-aluminum-iron-based low-carbon cementitious material to auxiliary cementitious material at (85-95): (5-15), which can ensure the reactivity of the sulfur-aluminum-iron-based cementitious system while introducing the potential hydration activity of the auxiliary cementitious material, improving the fluidity and working performance of the system, and further enhancing its adaptability to various pollutants.

[0019] 3. The biochar content of this invention is 1-5% of the total mass of the cementitious material. Within this range, the porous structure and surface functional groups of biochar can be fully utilized to enhance the adsorption and fixation of organic pollutants and heavy metals, while avoiding excessive addition that may have an adverse effect on the strength and stability of the cementitious system.

[0020] 4. The amount of colloidal material added in this invention accounts for 20-30% of the total mass of the in-situ soil and colloidal material. Under the premise of maintaining the basic structure of the soil, it can form an effective barrier to significantly inhibit the migration of pollutants, while ensuring construction adaptability and economic rationality.

[0021] 5. The total water-to-solid ratio of this invention is 15-20%. This ratio ensures the smooth progress of the hydration reaction in the cementing system, avoiding both insufficient water leading to incomplete cementation and excessive water causing increased porosity, thereby improving the compactness and long-term stability of the barrier material.

[0022] 6. The content of CaO, Al2O3, Fe2O3 and SO3 in the sulfur-aluminum-iron-based low-carbon cementitious material of the present invention is controlled within a specific range, which can generate a variety of stable hydration products such as hydrated calcium silicate, aluminate, iron-aluminum hydroxyl salt and ettringite during the hydration process. These products are not only beneficial to soil structure reinforcement, but also can achieve efficient fixation of pollutants through ion exchange and precipitation.

[0023] 7. The auxiliary cementing material of the present invention is selected from solid wastes such as slag, fly ash, silica fume and steel slag. Its active mineral components can produce a synergistic effect with the sulfur-aluminum-iron cementing system, further improving the strength, density and durability of the material, while realizing the resource utilization of solid waste, reducing costs and having good environmental benefits. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a statistical chart of the strength under different biochar content and clay ratios according to the present invention; Figure 2 This is a graph showing the effect of biochar content on coagulation time in this invention; Figure 3 This is a statistical chart of the permeability coefficients of biochar coupling materials under different systems of this invention; Figure 4 This is a diagram illustrating the effect of the biochar-coupled barrier material of this invention on pollutants. Figure 5 This is a graph showing the test results of the barrier material's ability to control pollutants (VOCs + heavy metals). Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] A method for preparing adaptive biochar-solid waste-based control materials for rapid control of organic-heavy metal complex pollution includes the following steps: S1, a colloidal material is obtained by dry mixing of sulfur-aluminum-iron-based low-carbon cementitious material (powder), auxiliary cementitious material (powder) and biochar. The mass ratio of sulfur-aluminum-iron low-carbon cementitious material to auxiliary cementitious material is (85-95):(5-15); the mass of biochar is 1-5% of the sum of the mass of sulfur-aluminum-iron low-carbon cementitious material and auxiliary cementitious material (i.e., the amount of biochar added).

[0028] S2, after mixing colloidal materials with in-situ soil, water is added and stirred to form biochar-solid waste-based pollution control materials; Among them, the mass of colloidal materials accounts for 20-30% of the total mass of in-situ soil and colloidal materials (i.e., the clay-colloidal ratio); in biochar-solid waste-based pollution control materials, the water-solid ratio is 15-20%.

[0029] The sulfur-aluminum-iron-based low-carbon cementitious material comprises the following raw materials by mass percentage: 35-45% CaO, 20-30% Al2O3, 6-15% Fe2O3, 8-15% SO3, and 4-12% SiO2.

[0030] The auxiliary cementing materials include one or more of the following: slag, fly ash or silica fume, steel slag, etc.

[0031] The technical solution of the present invention will be described in detail below through the following embodiments, wherein all parts mentioned in the following embodiments are parts by mass; and, in the embodiments, the sulfur-aluminum-iron-based low-carbon cementitious material includes the following raw materials by mass percentage: 40% CaO, 25% Al2O3, 10% Fe2O3, 10% SO3 and 12% SiO2; the auxiliary cementitious material is slag.

[0032] Example 1 S1, 85 parts of sulfur-aluminum-iron low-carbon cementitious material, 15 parts of auxiliary cementitious material (powder) are mixed with biochar to obtain colloidal material; wherein, the mass of biochar is 1% of the sum of the mass of sulfur-aluminum-iron low-carbon cementitious material and auxiliary cementitious material (i.e., the amount of biochar is 1%).

[0033] S2, after mixing the colloidal material with the in-situ soil, add water and stir to form a biochar-solid waste-based pollution control material; wherein, the mass of the colloidal material accounts for 30% of the total mass of the in-situ soil and the colloidal material (i.e., the colloidal-soil ratio is 30%); in the biochar-solid waste-based pollution control material, the water-solid ratio is 15%.

[0034] Example 2 S1, 95 parts of sulfur-aluminum-iron low-carbon cementitious material, 5 parts of auxiliary cementitious material (powder) are mixed with biochar to obtain colloidal material; wherein, the mass of biochar is 1% of the sum of the mass of sulfur-aluminum-iron low-carbon cementitious material and auxiliary cementitious material (i.e., the amount of biochar is 1%).

[0035] S2, after mixing the colloidal material with the in-situ soil, add water and stir to form a biochar-solid waste-based pollution control material; wherein, the mass of the colloidal material accounts for 30% of the total mass of the in-situ soil and the colloidal material (i.e., the colloidal-soil ratio is 30%); in the biochar-solid waste-based pollution control material, the water-solid ratio is 20%.

[0036] Example 3 In this embodiment, the strength (as of time) of the prepared biochar-solid waste-based pollution control material under different biochar content and clay ratios was studied. Specifically, based on the preparation method in Example 1, the mechanical strength of the obtained resistance-controlled material was tested by setting different biochar content (0, 1%, 2%, 3%, 4%, 5%) and different clay ratios (15%, 20%, 25%, 30%); the test results are as follows. Figure 1 As shown, from Figure 1 The results show that under different curing times (8h, 12h, 16h), the unconfined compressive strength exhibits a certain pattern with changes in biochar content. Overall, within a certain range, changes in biochar content cause fluctuations in compressive strength, and the trend and magnitude of these fluctuations differ under different curing times. For example, under certain combinations of clay-cement ratios and curing times, as the biochar content increases, the compressive strength first increases and then decreases, or exhibits other trends. This indicates that a higher or lower biochar content does not necessarily correspond to optimal strength; rather, there exists a relatively suitable range within which the compressive strength can reach a good level. Similarly, the clay-cement ratio also has a significant impact on compressive strength under different biochar content and curing time conditions. With changes in the clay-cement ratio, the unconfined compressive strength shows significant increases and decreases. It can be observed that when the clay-cement ratio is at certain specific values, the compressive strength is relatively high, indicating that the selection of the clay-cement ratio is crucial to the compressive performance of the material. A suitable clay-cement ratio can effectively improve the unconfined compressive strength. Therefore, it can be concluded that the biochar content should be maintained at 1-3%, and the clay-cement ratio should be >20%.

[0037] Example 4 In this embodiment, the effect of biochar content on the setting time of the barrier material is studied; Based on the preparation method in Example 1, the condensation time of the barrier material was determined by setting different amounts of biochar (0, 1%, 2%, 3%, 4%, 5%). Test results are as follows Figure 2 As shown, Figure 2 As can be seen, the initial setting time of the resistance material continuously increases with the biochar content from 0% to 5%. When the biochar content is 0%, the initial setting time is relatively short; however, when the content increases to 5%, the initial setting time is significantly prolonged. This indicates that the incorporation of biochar can delay the initial setting process of the resistance material, and this delaying effect is continuously strengthened with the increase of biochar content. The final setting time of the resistance material also increases with the increase of biochar content. From 0% to 5% biochar content, the final setting time gradually increases. This shows that biochar not only affects the initial setting time but also has a significant delaying effect on the final setting time, and the higher the biochar content, the more pronounced the extension of the final setting time. Considering both rapid molding and strength, a biochar addition of 1-3% should be selected.

[0038] Comparative Example 1 The only difference between the comparative example and Example 1 is that no biochar was added; the final product is a barrier material (SAF-soil).

[0039] Example 5 In this embodiment, the permeability coefficient of the barrier control material (SAF@BC-soil) prepared in Example 1 and the barrier control material (SAF-soil) prepared in Comparative Example 1 was tested. Variable head permeability tests were conducted according to the test methods in the industry standard JTG 3430-2020 "Specifications for Geotechnical Tests for Highways". The permeability solutions were deionized water, HCl solution (pH=2), NaOH solution (pH=12), CaCl2 solution (50mmol / L), C6H6 solution (50mmol / L), C2H4Cl2 solution (50mmol / L), and CCl4 solution (50mmol / L).

[0040] Test results are as follows Figure 3 As shown, in aqueous media, the permeability coefficient of SAF@BC-soil (biochar-coupled barrier material) is significantly lower than that of SAF-soil (barrier material without biochar coupling), indicating that the introduction of biochar effectively reduces the material's permeability in aqueous media and enhances its barrier control capability. In acidic (pH = 3), alkaline (pH = 12), and saline (50 mmol / L (CaCl2)) media, the permeability coefficient of SAF@BC-soil remains lower than that of SAF-soil. Furthermore, compared to aqueous media, although the permeability coefficient of SAF@BC-soil fluctuates under different acid, alkaline, and saline environments, it remains consistently at a low level, indicating that the biochar-coupled barrier material can maintain good low permeability and stable barrier control performance even under complex chemical environments. Under organic pollutant solutions (50 ppm C6H6, C2H4Cl2, CCl4), the permeability coefficient of SAF@BC-soil is significantly lower than that of SAF-soil. This demonstrates that biochar-coupled control materials also have a good barrier effect on the permeation of organic pollutants, effectively hindering the seepage of organic pollutant solutions within the material. This indicates that biochar coupling can significantly reduce the permeability coefficient of control materials, enhancing their barrier capabilities against water, acid / alkali / salt solutions, and organic pollutant solutions. Furthermore, under different chemical environments (acid / alkali, salt, organic pollutants), biochar-coupled control materials maintain a low permeability coefficient, exhibiting stable and reliable barrier performance, making them suitable for barrier control needs in various complex pollution scenarios.

[0041] Example 6 In this embodiment, the VOCs control effect of the barrier material (SAF@BC-soil) prepared in Example 1 and the barrier material (SAF-soil) prepared in Comparative Example 1 was tested. The rapid VOCs-blocking effect of biochar-coupled control materials was determined by column experiments. The lower part of the experimental column contained soil contaminated with VOCs (C6H6, C2H4Cl2, CCl4) at 50 ppm and 100 ppm, while the middle part contained the control material. The ability to block pollutants was evaluated by measuring the VOCs concentration in the uncontaminated soil at the top.

[0042] Test results are as follows Figure 4 As shown in the figure, throughout the entire test period, SAF@BC-soil (biochar-coupled control material) reduced the concentration of volatile organic compounds (VOCs) more significantly than SAF-soil (uncoupled biochar control material). Over time, SAF@BC-soil reduced pollutant concentrations more rapidly, and at the end of the test, its corresponding pollutant concentration was lower. Biochar coupling significantly enhances the control effect: Coupling biochar into the control material significantly improves the control effect on different types and concentrations of volatile organic compounds (VOCs). Whether it is low concentration (50 ppm) or high concentration (100 ppm) of C6H6, C2H4Cl2, and CCl4, SAF@BC-soil can more effectively reduce pollutant concentrations. The control effect varies for different pollutants: The material's control effect varies for different types of VOCs, suggesting that in practical applications, biochar-coupled control materials need to be specifically optimized and applied according to the specific pollutant type. It has excellent long-term pollution control capabilities: SAF@BC-soil maintains stable and durable pollution control capabilities throughout the entire testing period. Compared with SAF-soil, it is better able to meet the needs of long-term pollution control and has better application prospects.

[0043] Example 7 In this embodiment, the barrier control effect of the barrier control material (SAF@BC-soil) prepared in Example 1 and the barrier control material (SAF-soil) prepared in Comparative Example 1 on pollutants (VOCs + heavy metals) was tested. The experimental procedure is as follows: The test site was a coking plant, covering an area of ​​700m². 2The site was found to be contaminated with a combination of heavy metal chromium and volatile organic compounds. The average chromium (VI) content was 121 mg / kg, and the average 1,2-dichloroethane content was 200 mg / kg, exceeding the screening values ​​for Class II construction land (Cr 5.7 mg / kg) and (1,2-dichloroethane 9 mg / kg) in the "Soil Environmental Quality Standard for Construction Land Soil Pollution Risk Control" (GB 36600-2018) by 21.23 times and 22.22 times, respectively. Within a 5×5m area of ​​the contaminated site, the barrier material prepared in Example 1 (SAF@BC-soil) and the barrier material prepared in Comparative Example 1 (SAF-soil) were tested.

[0044] Starting from the leveling of the soil, the concentration of 1,2-dichloroethane in the soil and the concentration of Cr in the infiltrated solution in the upper part of the barrier material are measured at regular intervals, and the barrier effect is evaluated based on the changing trends.

[0045] Experimental results are as follows Figure 5 As shown, Comparative Example 1 showed Cr within 72 h 6+ The concentration remained at a relatively high level, approximately 50–70 mg / L, with significant fluctuations, indicating that the system was susceptible to Cr. 6+ Its removal and stabilization capabilities are limited. In contrast, under the same conditions, Cr in Example 1... 6+ The concentration remained consistently between 0 and 0.6 mg / L, significantly lower than that of Comparative Example 1, and the concentration increase was slow, demonstrating a significant passivation and fixation effect on heavy metals. Therefore, the combination of biochar and sulfur-aluminum-iron materials significantly improved the Cr... 6+ The removal efficiency and stability of the composite material effectively control the migration and release of heavy metals. Combined with another set of spectral results, it was found that in Comparative Example 1, the concentration of 1,2-dichloroethane varied significantly, indicating that the pollutant continued to be released; while in Example 1, the concentration of 1,2-dichloroethane decreased significantly throughout the reaction process and remained at a low level, demonstrating that the composite material also exhibits excellent control performance in adsorbing and degrading VOCs.

[0046] In summary, this invention, by coupling biochar with sulfur-aluminum-iron materials, can significantly improve the system's resistance to Cr. 6+ It has the ability to immobilize heavy metal ions and effectively reduce the release concentration of volatile organic compounds such as 1,2-dichloroethane, thereby achieving synergistic control of typical complex pollutants.

[0047] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0048] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing biochar-solid waste-based pollution control materials, characterized in that, Includes the following steps: A colloidal material is obtained by dry mixing of sulfur-aluminum-iron-based low-carbon cementitious material, auxiliary cementitious material and biochar. After mixing the colloidal material with the in-situ soil, water is added and stirred to form a biochar-solid waste-based pollution control material.

2. The method for preparing biochar-solid waste-based pollution control material according to claim 1, characterized in that, The mass ratio of the sulfur-aluminum-iron-based low-carbon cementitious material to the auxiliary cementitious material is (85-95):(5-15).

3. The preparation method of the biochar-solid waste-based pollution control material according to claim 1, characterized in that, The mass of the biochar is 1-3% of the sum of the mass of the sulfur-aluminum-iron low-carbon cementitious material and the auxiliary cementitious material.

4. The method for preparing the biochar-solid waste-based pollution control material according to claim 1, characterized in that, The mass of the colloidal material accounts for 20-30% of the total mass of the in-situ soil and the colloidal material.

5. The method for preparing a biochar-solid waste-based pollution control material according to claim 1, characterized in that, The water-to-solid ratio in the biochar-solid waste-based pollution control material is 15-20%.

6. The method for preparing the biochar-solid waste-based pollution control material according to claim 1, characterized in that, The sulfur-aluminum-iron-based low-carbon cementitious material comprises the following raw materials by mass percentage: 35-45% CaO, 20-30% Al2O3, 6-15% Fe2O3, 8-15% SO3, and 4-12% SiO2.

7. The method for preparing biochar-solid waste-based pollution control material according to claim 1, characterized in that, The auxiliary cementing materials include one or more of the following: slag, fly ash or silica fume, steel slag, etc.

8. A biochar-solid waste-based pollution control material, characterized in that, It was prepared using the preparation method according to any one of claims 1-7.

9. The application of the biochar-solid waste-based pollution control material according to claim 8 in soil pollution control or remediation.

10. A building casting material, characterized in that, This includes the biochar-solid waste-based pollution control material as described in claim 8.

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