Ecological restoration material and application thereof

Abstract

An eco-remediation material is disclosed, obtained by modifying sodium hexametaphosphate bentonite with a biosurfactant; wherein the weight ratio of biosurfactant to sodium hexametaphosphate bentonite is (5-10):100. Furthermore, the application of this eco-remediation material to the remediation of contaminated soil in landfills is also disclosed. Compared with existing technologies, this eco-remediation material exhibits higher expansion characteristics and lower permeability.

Description

Technical Field

[0001] This invention belongs to the field of landfill wastewater treatment technology; it relates to an ecological restoration material and its application. Background Technology

[0002] In my country, urban waste is primarily disposed of through landfills. Due to insufficient understanding of landfills in the past, soil and groundwater pollution is widespread, seriously threatening urban environmental safety. Soil pollution at landfills mainly results from landfill wastewater, such as leachate, penetrating deep into the soil layer during waste dumping. This wastewater undergoes filtration, adsorption, sedimentation, or migration with groundwater, leading to soil contamination through physical, chemical, and biological processes. Leachate has a complex composition, characterized by high heavy metal content, high organic matter concentration, significant water quality fluctuations, high ammonia nitrogen content, and an imbalanced nutrient ratio. Therefore, once leachate enters the soil and groundwater, it causes extremely complex pollution problems with highly persistent environmental toxicity. This presents a significant challenge to landfill remediation. Furthermore, most of my country's landfills are located in the central and eastern regions, where fine-grained soils have high adsorption capacity but low permeability, further posing a significant risk to landfill remediation.

[0003] Remediation technologies for contaminated soil from landfills require comprehensive consideration of multiple factors, prioritizing solutions that are technically applicable, have suitable remediation timelines, and whose remediation components are permissible. Furthermore, factors such as reducing pollutant toxicity and preventing secondary pollution should be taken into account to comprehensively minimize environmental hazards and impacts on human safety. Existing remediation technologies include physical remediation, chemical remediation, and bioremediation.

[0004] Vertical barrier technology can be used to directly isolate pollutants from the external environment and control groundwater flow to prevent pollutants from being transported by advection. This technology has a wide range of applications, excellent seepage prevention performance, strong site adaptability, and engineering costs far lower than various active remediation technologies. It combines temporary and permanent remediation functions and is particularly suitable for the remediation of industrial contaminated sites and landfills.

[0005] In vertical barrier technology, bentonite has excellent low permeability, swelling and shrinkage, dispersibility and cation exchange properties, thus producing unique barrier performance. It has been widely used in in-situ vertical barrier systems to control the migration of pollutants.

[0006] Chinese invention patent application CN114291861A discloses a landfill wastewater remediation material, comprising a solidifying material with a solid-liquid ratio of 1:(1.8-4) and landfill leachate. The solidifying material comprises the following raw materials in parts by weight: 60-80 parts bentonite, 29-39 parts tailings powder, 0.5-1.5 parts superabsorbent resin, 0.5-1 part cellulose, and 0.5-2 parts grass seeds. This solidifying material can improve the treatment efficiency of landfill leachate and also utilize landfill leachate for ecological restoration.

[0007] Chinese invention patent application CN1569660A discloses an inorganic-organic composite bentonite wastewater treatment material and its preparation method. Crushed bentonite is added to a cationic surfactant solution and stirred in a water bath. An AlCl3 solution is added to the suspension at a concentration of 1–10 mmol AlCl3 / g bentonite. Under water bath stirring, a NaOH or Na2CO3 solution is added dropwise to the suspension, and the product is aged at room temperature. After repeated washing and filtration, the product is dried and ground. This application first exchanges the surfactant into the bentonite interlayer, then forms aluminum hydroxyl groups in the bentonite interlayer and on the surface. This reduces the competition between the hydroxyl metal and the surfactant in the bentonite interlayer, which is beneficial for the exchange and adsorption of phosphate and improves the coagulation performance of the modified bentonite. It can simultaneously remove organic pollutants and phosphates from wastewater.

[0008] However, in practical applications, bentonite exhibits significantly increased permeability, resulting in poor seepage prevention under the influence of pollutants, especially in scenarios with high concentrations of pollutants. Therefore, there is an urgent need to find an ecological restoration material with higher expansion characteristics and lower permeability. Summary of the Invention

[0009] The purpose of this invention is to provide an ecological restoration material with higher expansion characteristics and lower permeability.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: an ecological restoration material is obtained by modifying sodium hexametaphosphate bentonite (SHMP@B) and biosurfactant (BF); wherein the weight ratio of biosurfactant (BF) to sodium hexametaphosphate bentonite (SHMP@B) is (5-10):100.

[0011] Advantageously, the weight ratio of biosurfactant (BF) to sodium hexametaphosphate bentonite (SHMP@B) is (6-9):100.

[0012] In the ecological restoration material according to the present invention, the biosurfactant (BF) is selected from rhamnolipin (RL) or sophorolipid (SL).

[0013] Advantageously, the biosurfactant (BF) is selected from sophorolipid (SL).

[0014] In the ecological restoration material according to the present invention, the biosurfactant (BF) is selected from mixed sophorolipids (SL).

[0015] According to the ecological restoration material of the present invention, the weight ratio of acidic sophorolipid to lactone sophorolipid in the mixed sophorolipid (SL) is (1-4):1.

[0016] Advantageously, the weight ratio of acidic sophorolipid to lactone sophorolipid in the mixed sophorolipid (SL) is (2-3):1.

[0017] According to the ecological restoration material of the present invention, the sodium hexametaphosphate bentonite is obtained by modifying bentonite (B) with sodium hexametaphosphate (SHMP).

[0018] In the ecological restoration material of the present invention, the weight ratio of sodium hexametaphosphate (SHMP) to bentonite (B) is (3-8):100.

[0019] Advantageously, the weight ratio of sodium hexametaphosphate (SHMP) to bentonite (B) is (4-7):100.

[0020] According to the ecological restoration material of the present invention, the bentonite (B) is selected from sodium bentonite (SB) or calcium bentonite (CB).

[0021] According to the ecological restoration material of the present invention, the bentonite (B) is selected from calcium-based bentonite (CB).

[0022] On the other hand, the present invention provides a use of the ecological restoration material according to the present invention, wherein it is used for the remediation of contaminated soil in landfills.

[0023] According to the application described in the invention, it is used as a vertical barrier system.

[0024] Compared with existing technologies, the ecological restoration material described in this invention exhibits higher expansion characteristics and lower permeability characteristics. Detailed Implementation

[0025] It must be noted that, unless the context clearly specifies otherwise, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” can include one or more referents (i.e., two or more, including two).

[0026] Unless otherwise specified, numerical ranges in this invention are approximate and therefore may include values ​​outside of said range. The numerical range may be expressed in this invention as from “about” a particular value and / or to “about” another particular value. When such a range is expressed, another aspect includes from said one particular value and / or to another particular value. Similarly, when a value is expressed as an approximation using the antecedent “about,” it should be understood that said particular value forms another aspect. It should also be understood that each endpoint in a numerical range is significant in relation to and independent of another endpoint.

[0027] The reference to the weight parts of a specific element or component in the composition or article in the specification and the final claims refers to the weight relationship between that element or component and any other element or component in the composition or article, expressed in parts by weight.

[0028] In this invention, unless specifically indicated otherwise, or implied by the context or customary practice in the art, all solutions referred to herein are aqueous solutions; when the solute in the aqueous solution is a liquid, all fractions and percentages are by volume, and the volume percentage of a component is based on the total volume of the composition or product containing that component; when the solute in the aqueous solution is a solid, all fractions and percentages are by weight, and the weight percentage of a component is based on the total weight of the composition or product containing that component.

[0029] The terms “comprising,” “including,” “having,” and similar expressions used in this invention are not intended to exclude the presence of any optional components, steps, or procedures, whether or not any optional components, steps, or procedures are specifically disclosed. For the avoidance of any doubt, unless stated to the contrary, all methods claimed by using the term “comprising” may include one or more additional steps, equipment parts or components, and / or substances. In contrast, the term “consisting of” excludes any components, steps, or procedures not specifically described or enumerated. Unless otherwise stated, the term “or” refers to members listed individually and in any combination.

[0030] Furthermore, the contents of any patent or non-patent documents referenced in this invention are incorporated herein by full citation, especially regarding definitions disclosed in the relevant field (where there is no inconsistency with any definitions specifically provided herein) and common knowledge.

[0031] In this invention, unless otherwise specified, all parts are by weight, all temperatures are expressed in °C or at ambient temperature, and all pressures are at or near atmospheric pressure. Room temperature means 20-30 °C. E-10 means 10 -10There are various variations and combinations of reaction conditions (e.g., component concentrations, required solvents, solvent mixtures, temperature, pressure, and other reaction ranges) and conditions that can be used to optimize the purity and yield of the product obtained by the method. Optimization of such method conditions will only require reasonable routine experiments.

[0032] Example 1

[0033] Calcium-based bentonite (CB) was added to a 20 g / L aqueous solution of sodium hexametaphosphate (SHMP); the amount of sodium hexametaphosphate (SHMP) used was 5 wt% based on the dry weight of calcium-based bentonite (CB). The mixture was thoroughly stirred to form a slurry and allowed to stand for hydration for 24 h. Then, it was stirred again for 15 min, and finally dried at 105 °C. The slurry was then ground through a 200-mesh sieve to obtain sodium hexametaphosphate-modified calcium-based bentonite (SHMP@CB).

[0034] SHMP@CB was added to a 10 wt% aqueous solution of mixed sophorolipid (SL), which was obtained by diluting SLMP 3150 (acidic sophorolipid: lactone sophorolipid weight ratio = 2.5:1) from Shaanxi Deguan Biotechnology Co., Ltd. Based on the dry weight of SHMP@CB, the amount of mixed sophorolipid (SL) used was 8 wt%. The mixture was thoroughly stirred and allowed to stand for hydration for 24 h. Then, it was stirred again for 15 min, and finally dried at 105℃. The slurry was then ground through a 200-mesh sieve to obtain SL-SHMP@CB.

[0035] IR spectra show that SLMP-SHMP@CB at 3612 cm⁻¹ -1 3449cm -1 3410cm -1 2963cm -1 1732cm -1 1639cm -1 1562cm -1 1420cm -1 925cm -1 795cm -1 and 473cm -1 Characteristic absorption peaks appear at positions such as [positions not specified].

[0036] Comparative Example 1

[0037] Calcium-based bentonite (CB) was added to a 20 g / L aqueous solution of sodium hexametaphosphate (SHMP); the amount of sodium hexametaphosphate (SHMP) used was 5 wt% based on the dry weight of calcium-based bentonite (CB). The mixture was thoroughly stirred to form a slurry and allowed to stand for hydration for 24 h. Then, it was stirred again for 15 min, and finally dried at 105 °C. The slurry was then ground through a 200-mesh sieve to obtain sodium hexametaphosphate-modified calcium-based bentonite (SHMP@CB).

[0038] SHMP@CB was added to a 10 wt% aqueous solution of acidic sophorolipid (SL), which was obtained by diluting SLA1240 from Shaanxi Deguan Biotechnology Co., Ltd. Based on the dry weight of SHMP@CB, the amount of acidic sophorolipid (SL) used was 8 wt%. The mixture was thoroughly stirred and allowed to stand for hydration for 24 h. Then, it was stirred again for 15 min, and finally dried at 105℃. The slurry was then ground through a 200-mesh sieve to obtain SL-SHMP@CB.

[0039] Example 2

[0040] Calcium-based bentonite (CB) was added to a 20 g / L aqueous solution of sodium hexametaphosphate (SHMP); the amount of sodium hexametaphosphate (SHMP) used was 6 wt% based on the dry weight of calcium-based bentonite (CB). The mixture was thoroughly stirred to form a slurry and allowed to stand for hydration for 24 h. Then, it was stirred again for 15 min, and finally dried at 105 °C. The slurry was then ground through a 200-mesh sieve to obtain sodium hexametaphosphate-modified calcium-based bentonite (SHMP@CB).

[0041] SHMP@CB was added to an 8 wt% aqueous solution of mixed sophorolipid (SL), which was obtained by diluting SLMP 3150 (acidic sophorolipid: lactone sophorolipid weight ratio = 2.5:1) from Shaanxi Deguan Biotechnology Co., Ltd. Based on the dry weight of SHMP@CB, the amount of mixed sophorolipid (SL) used was 7 wt%. The mixture was thoroughly stirred and allowed to stand for hydration for 24 h. Then, it was stirred again for 15 min, and finally dried at 105℃. The slurry was then ground through a 200-mesh sieve to obtain SL-SHMP@CB.

[0042] Performance testing

[0043] The expansion index is an important indicator reflecting expansion and contraction properties and water-holding capacity. The test method follows Section 5.5 of JG / T193-2006, using a solution containing Cd. 2+ A 500 mg / L heavy metal aqueous solution can be used as a substitute for deionized water.

[0044] The permeability coefficient is an important indicator of water permeability and pollution resistance. The specific test method is as follows: Refer to GB / T50123-2019, using a unit area of ​​4000 g / m². 2 Prepare a sample (Φ61.8*10mm) and pre-saturate it; place the sample into a container, filling the remaining cavity with permeable stone. Seal with Vaseline, connect the container with the water head device, ensuring the water head height does not exceed 2m; use a Cd-containing... 2+ Replace deionized water with a 500 mg / L heavy metal aqueous solution; record the values ​​and calculate the permeability coefficient.

[0045] The results are shown in Table 1.

[0046] Table 1

[0047] Bulk expansion index (mL / 2g) Permeability coefficient (m / s) Example 1 SL-SHMP@CB 29.7 1.2E-11 Comparative Example 1: SL-SHMP@CB 22.6 4.9E-11 SHMP@CB 7.1 1.6E-10

[0048] As can be seen from Table 1, compared with SL-SHMP@CB and SHMP@CB of Comparative Example 1, SL-SHMP@CB of Example 1 of this application exhibits higher expansion characteristics and lower permeation characteristics.

[0049] Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various modifications, substitutions, deletions, corrections or adjustments to the technical solutions of this invention, and these equivalent technical solutions also fall within the scope defined by the claims of this invention.

Claims

1. An ecological restoration material, obtained by modifying sodium hexametaphosphate bentonite with a biosurfactant; the weight ratio of biosurfactant to sodium hexametaphosphate bentonite is (5-10):100; The sodium hexametaphosphate bentonite is obtained by modifying bentonite with sodium hexametaphosphate; the weight ratio of sodium hexametaphosphate to bentonite is (3-8):100; the bentonite is selected from calcium-based bentonite. The biosurfactant is selected from mixed sophorolipids; the weight ratio of acidic sophorolipids to lactone sophorolipids in the mixed sophorolipids is (1-4):

1.

2. The use of the ecological restoration material according to claim 1, characterized in that, Used for the remediation of contaminated soil in landfills.

3. The use according to claim 2, characterized in that, As a vertical barrier system.