A marine waste-based biocomposite soil remediation agent and a preparation method thereof

Abstract

The present application relates to the technical field of soil remediation, and particularly relates to a biological composite soil remediation agent based on marine waste and a preparation method thereof.The soil remediation agent of the present application is composed of shell powder, seaweed extract and microbial inoculum, wherein the viable cell count of the microbial inoculum in the biological composite soil remediation agent based on marine waste is 1-5x10 8 CFU / g; the mass ratio of the shell powder and the seaweed extract is 1-10:0.1-1.The soil remediation agent provided by the present application is expected to achieve more significant and more durable remediation effect on acidic and severely cadmium-contaminated soil in a shorter time, with lower application amount and economic cost, and simultaneously achieve improvement of soil ecological function, thereby providing a brand-new and comprehensive solution for safe utilization of agricultural land.

Description

Technical Field

[0001] This invention relates to the field of soil remediation technology, and in particular to a bio-composite soil remediation agent based on marine waste and its preparation method. Background Technology

[0002] In recent years, with the rapid development of industrial and agricultural production, heavy metal pollution in farmland soil has become increasingly prominent, with cadmium (Cd) attracting particular attention due to its high mobility and toxicity. According to the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (Trial)" (GB 15618-2018), the risk screening value for cadmium in acidic farmland with a pH ≤ 5.5 is 0.3 mg / kg. When the cadmium content in the soil approaches or exceeds the severe pollution level of 1.5 mg / kg, it far exceeds the risk control value, posing a serious threat to agricultural product safety and human health, and necessitates effective remediation measures.

[0003] Currently, remediation technologies for cadmium contamination in agricultural land soil mainly include physical, chemical, and biological remediation methods. However, existing technologies all have significant limitations when dealing with acidic, heavily cadmium-contaminated soils.

[0004] Physical remediation methods, such as topsoil application and deep tillage, can reduce the concentration of pollutants in the topsoil in the short term, but they involve large-scale engineering and high costs. In essence, they only transfer or dilute pollutants and fail to achieve true removal of pollutants. They may also damage the original soil structure and are not suitable for large areas of moderately to lightly polluted farmland.

[0005] Chemical remediation, particularly in-situ passivation, primarily involves adding passivating agents such as lime, bentonite, and apatite to adjust soil pH or reduce the bioavailability of cadmium through adsorption and precipitation. However, this method suffers from the drawback of only addressing the symptoms, not the root cause; cadmium remains in the soil and is not removed from the environment. In acidic soils, passivation effectiveness is particularly dependent on pH increases, but due to the continuous effects of rainwater leaching and soil acidification, its effects are difficult to sustain and prone to "rebound." Furthermore, excessive application of chemical amendments can lead to secondary risks such as soil compaction, salinization, and nutrient imbalances.

[0006] Bioremediation methods mainly include phytoremediation and microbial remediation. Phytoremediation utilizes hyperaccumulating plants to absorb and remove cadmium from the soil, which is environmentally friendly. However, hyperaccumulating plants typically grow slowly and have small biomass, resulting in extremely long remediation cycles, making it difficult to meet the practical needs of rapid remediation. Furthermore, under acidic, high-cadmium stress, plant growth is inhibited, leading to a sharp drop in remediation efficiency. Moreover, harvested cadmium-rich plants are hazardous waste, posing high costs and risks for subsequent disposal. Microbial remediation utilizes specific functional microorganisms to adsorb, precipitate, or complex cadmium. However, their functions are often relatively singular, and exogenous microorganisms face difficulties in colonizing in complex acidic soil environments, are susceptible to competition from indigenous microbial communities, and are affected by nutrient limitations, leading to unstable remediation results.

[0007] To overcome the shortcomings of single remediation technologies, various combined remediation techniques have been attempted in recent years. However, existing combined remediation methods mostly remain at the level of simple stacking of different materials, lacking in-depth design and optimization of the synergistic mechanisms between materials. For example, the addition of certain chemical passivating agents may inhibit the activity of soil microorganisms, resulting in poor synergistic effects between passivation and microbial remediation, or even a situation where the effect is reduced rather than increased, often accompanied by a significant increase in remediation costs.

[0008] In summary, existing remediation technologies generally suffer from high costs, long cycles, unstable effects, poor environmental adaptability, or are only applicable to specific levels of pollution. In particular, there is a lack of a technical solution that can simultaneously achieve high efficiency, stability, economy, and environmental friendliness, and specifically address the challenges of remediating acidic (pH < 5.5) heavily cadmium-contaminated farmland soil (cadmium content 0.8–1.5 mg / kg). Therefore, developing a synergistic remediation material capable of withstanding the dual stresses of strong acid and high cadmium levels, providing long-lasting remediation effects, and without damaging soil ecological functions has significant practical implications and application value. Summary of the Invention

[0009] The purpose of this invention is to provide a bio-composite soil remediation agent based on marine waste and its preparation method, so as to solve the technical problems existing in the prior art.

[0010] To achieve the above-mentioned objectives, the present invention provides the following technical solution: One of the technical solutions of this invention provides a bio-composite soil remediation agent based on marine waste, composed of shell powder, seaweed extract, and microbial inoculants, wherein the viable count of the microbial inoculants in the bio-composite soil remediation agent based on marine waste is 1~5×10⁻⁶. 8 CFU / g; the mass ratio of the shell powder to the seaweed extract is 1~10:0.1~1.

[0011] The second technical solution of this invention provides a method for preparing the above-mentioned bio-composite soil remediation agent based on marine waste, comprising the following steps: A soil remediation agent is obtained by mixing shell powder, seaweed extract, and microbial inoculant.

[0012] The third technical solution of this invention provides the application of the above-mentioned bio-composite soil remediation agent based on marine waste in the remediation of acidic and cadmium-contaminated soil.

[0013] The fourth technical solution of the present invention provides a soil remediation method, comprising the following steps: applying the above-mentioned marine waste-based bio-composite soil remediation agent to the surface of acidic, cadmium-contaminated soil, rotary tilling to mix the soil conditioner with the soil, and leaving it for 40 days to reduce acidity and cadmium pollution.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention scientifically combines specific functional microbial agents, seaweed extract, and shell powder to form a composite remediation agent. Shell powder, acting as a pH regulator and passivation core, rapidly neutralizes soil acidity, provides adsorption sites for calcium ions and cadmium, and reduces cadmium activity. Seaweed extract, as a microbial synergist and soil conditioner, stimulates the proliferation of functional microorganisms, enhancing their tolerance and activity; it also improves soil aggregate structure and increases organic matter. The functional microbial agents, acting as a long-term stabilizing and transformation engine, colonize the improved soil environment, further fixing cadmium through biosorption, extracellular precipitation, or micro-area passivation, and transforming it into a more stable form, preventing rebound.

[0015] This invention utilizes shell powder to rapidly adjust acidity, creating a suitable living environment for microorganisms. This breaks through the bottleneck of low bioremediation efficiency in acidic soils. Chemical passivation provides immediate effects, while biological passivation provides lasting stability. Seaweed extract acts as a bridge to strengthen both. Furthermore, all materials are natural or environmentally friendly. While remediating cadmium pollution, it also replenishes calcium and organic matter, promotes the recovery of soil microbial communities, and enhances soil fertility. The materials are widely available and low in cost. Moreover, the synergistic effect reduces the high dosage requirements of single materials, improving the cost-effectiveness of remediation.

[0016] The soil remediation agent provided by this invention is expected to achieve more significant and longer-lasting remediation effects on acidic, heavily cadmium-contaminated soil in a shorter time, with lower application rates and economic costs, while simultaneously improving soil ecological functions, providing a new and comprehensive solution for the safe use of agricultural land. Detailed Implementation

[0017] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0018] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0019] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0020] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0021] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0022] All raw materials used in this invention can be obtained commercially or prepared using existing technologies.

[0023] This invention provides a bio-composite soil remediation agent based on marine waste, composed of shell powder, seaweed extract, and microbial inoculants, wherein the viable count of the microbial inoculants in the bio-composite soil remediation agent based on marine waste is 1~5×10⁻⁶. 8 CFU / g; the mass ratio of the shell powder and seaweed extract is 1~10:0.1~1, preferably 1~5:0.1~0.5, and more preferably 2~3:0.2~0.3.

[0024] In this invention, the viable count of the microbial agent in the marine waste-based bio-composite soil remediation agent is preferably 1×10⁻⁶. 8 CFU / g.

[0025] In this invention, the preferred mass ratio of the shell powder to the seaweed extract is 10:1.

[0026] In this invention, the shell powder mainly plays a dominant role in pH adjustment and co-precipitation. Specifically, the main component of the shell powder is calcium carbonate, which slowly dissolves in acidic soil, consuming H₂. + Cadmium ions gradually and steadily increase soil pH. When soil pH rises to the neutral or slightly alkaline range (e.g., >6.0), the solubility of cadmium ions decreases significantly, making it easier to form precipitates such as CdCO3 and Cd(OH)2, or enhancing their specific adsorption on the surfaces of iron-manganese oxides and clay minerals, thus achieving a transformation from exchangeable to carbonate-bound and iron-manganese oxide-bound states. Simultaneously, the dissolution of calcium carbonate provides Ca2+. 2+ Can be used with Cd 2+ Ion competition occurs, inhibiting the absorption of Cd by plants; simultaneously, isomorphic substitution or co-precipitation can occur on the surface of calcium carbonate, transferring Cd... 2+ Fixed to its lattice or surface.

[0027] In this invention, the content of seaweed polysaccharides in the seaweed extract is ≥50%.

[0028] In this invention, the seaweed extract functions as an organic complex and ecological regulator. Specifically, the seaweed extract is rich in active substances such as seaweed polysaccharides (e.g., alginate), phenolic compounds, and proteins. It contains numerous functional groups such as carboxyl (-COOH), hydroxyl (-OH), and amino (-NH2), which can interact with Cd. 2+ Strong complexing or chelating reactions occur, forming water-soluble or poorly soluble complexes with large molecular weights and high stability, thus reducing Cd. 2+ The ion activity of the extract is high. The organic matter in the extract can promote the formation of soil micro-aggregates and increase the soil's adsorption capacity for Cd. At the same time, it can also act as an organic colloid, providing abundant adsorption sites, providing easily usable carbon sources and nutrients for functional microorganisms in the soil (including exogenously added inoculants), stimulating their metabolic activity, and indirectly enhancing the microbial remediation process.

[0029] In this invention, the microbial agent is preferably Bacillus, and the Bacillus is preferably one or more of Bacillus subtilis, Bacillus subtilis and Bacillus mucilaginosus.

[0030] In this invention, the role of the microbial agent is driven by bioadsorption and transformation. Specifically, the selected functional microorganisms have cell walls rich in polysaccharides and glycoproteins, which can passively adsorb Cd through ion exchange, surface complexation, electrostatic adsorption, and other processes. 2+Microorganisms can actively metabolize Cd into less bioavailable forms through intracellular sequestration (such as binding to metallothioneins and phytochelates) and extracellular precipitation (such as secreting carbonate and phosphate ions to precipitate Cd). The colonization of beneficial microorganisms can improve soil microecology, promote nutrient cycling, enhance plant root vitality, and indirectly improve the soil system's resistance to pollution stress and its remediation potential.

[0031] This invention also provides a method for preparing the above-mentioned bio-composite soil remediation agent based on marine waste, comprising the following steps: A soil remediation agent is obtained by mixing shell powder, seaweed extract, and microbial inoculant.

[0032] This invention also provides the application of the above-mentioned marine waste-based biocomposite soil remediation agent in the remediation of acidic, cadmium-contaminated soils.

[0033] In this invention, the mechanism of the soil remediation agent is as follows: Shell powder preferentially increases soil pH, creating an optimal chemical and biological environment for subsequent microbial activity (most microorganisms thrive in neutral environments) and the stable existence of macromolecules in seaweed extract. It also directly promotes the precipitation of some Cd. Based on the improved pH conditions, seaweed extract "captures" Cd in solution and some weakly bound Cd through organic complexation, while microorganisms act on Cd at the solution and solid-phase interface through bioadsorption and transformation. These three elements form a three-dimensional fixation network from solution to solid phase, from inorganic precipitation to organic complexation, and from physicochemical adsorption to biotransformation. Seaweed extract, as a synergist for microorganisms, improves the survival and activity of the microbial agent; microbial metabolites may further alter the form of Cd and promote the transformation of organic matter; calcium ions provided by shell powder help maintain soil structural stability. These three elements mutually promote each other, producing a synergistic remediation effect.

[0034] The composite system of this invention is particularly suitable for acidic soils with low concentrations of Cd contaminated soil. Shell powder precisely addresses the acidity issue; seaweed extract and microbial agents exhibit high affinity and efficient removal capabilities for low concentrations of heavy metals, avoiding the problems of insufficient efficiency or excessive cost of single physicochemical methods at low concentrations.

[0035] The present invention also provides a soil remediation method, comprising the following steps: applying the above-mentioned marine waste-based biocomposite soil remediation agent to the surface of acidic, cadmium-contaminated soil, rotary tilling to mix the soil conditioner with the soil, and leaving it for 40 days to reduce acidity and cadmium pollution.

[0036] In this invention, the depth of rotary tillage is 0~20cm; the pH of the acidic, cadmium-contaminated soil is ≤5.5, and the cadmium content is 0.8~1.5mg / kg.

[0037] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0038] In an embodiment of the present invention, the shell powder is obtained by washing oyster shell powder with deionized water, drying it, pulverizing it through a 100-mesh sieve, and calcining it at 900°C; the seaweed extract contains 50% seaweed polysaccharide; the microbial agent is purchased from Zhengzhou Zhongke Chemical Products Co., Ltd., with an effective viable count ≥50 billion / g, and the main bacteria are Bacillus subtilis, Bacillus licheniformis, and Bacillus spp.

[0039] Example 1 A soil remediation agent is composed of 5g of shell powder, 0.5g of seaweed extract, and a microbial inoculant. The viable count of the microbial inoculant in the soil remediation agent is 1×10⁻⁶. 8 CFU / g.

[0040] Preparation method of soil remediation agent: The soil remediation agent is obtained by mixing shell powder, seaweed extract and microbial agent evenly.

[0041] Comparative Example 1 A soil remediation agent, composed of 1g of shell powder and microbial inoculant; the viable count of the microbial inoculant in the soil remediation agent is 1×10⁻⁶. 8 CFU / g.

[0042] Preparation method of soil remediation agent: The soil remediation agent is obtained by mixing shell powder and microbial inoculant evenly.

[0043] Comparative Example 2 A soil remediation agent, composed of 5g of shell powder and microbial inoculant; the viable count of the microbial inoculant in the soil remediation agent is 1×10⁻⁶. 8 CFU / g.

[0044] Preparation method of soil remediation agent: The soil remediation agent is obtained by mixing shell powder and microbial inoculant evenly.

[0045] Comparative Example 3 A soil remediation agent, composed of 10g of shell powder and microbial inoculant; the viable count of the microbial inoculant in the soil remediation agent is 1×10⁻⁶. 8 CFU / g.

[0046] The oyster shell powder was cleaned with deionized water, dried, pulverized and passed through a 100-mesh sieve, and calcined at 900℃ to obtain shell powder. Preparation method of soil remediation agent: The soil remediation agent is obtained by mixing shell powder and microbial inoculant evenly.

[0047] Comparative Example 4 A soil remediation agent, composed of 0.1g of seaweed extract and microbial inoculant; the viable count of the microbial inoculant in the soil remediation agent is 1×10⁻⁶. 8 CFU / g.

[0048] Preparation method of soil remediation agent: The soil remediation agent is obtained by mixing seaweed extract and microbial inoculant evenly.

[0049] Comparative Example 5 A soil remediation agent, composed of 0.5g of seaweed extract and microbial inoculant; the viable count of the microbial inoculant in the soil remediation agent is 1×10⁻⁶. 8 CFU / g.

[0050] Preparation method of soil remediation agent: The soil remediation agent is obtained by mixing seaweed extract and microbial inoculant evenly.

[0051] Comparative Example 6 A soil remediation agent, composed of 1g of seaweed extract and microbial inoculant; the viable count of the microbial inoculant in the soil remediation agent is 1×10⁻⁶. 8 CFU / g.

[0052] Preparation method of soil remediation agent: The soil remediation agent is obtained by mixing seaweed extract and microbial inoculant evenly.

[0053] Test case Soil: Local farmland soil was collected with a pH of 4.54 at a depth of 0-20cm. The soil was then air-dried, sieved, and placed in a container.

[0054] Experimental method: Base fertilizer was applied to the collected soil in one go, namely, P2O5 0.2 g / kg, K2O 0.3 g / kg, N 0.2 g / kg (calculated as pure nitrogen, urea as nitrogen source), and CdCl2 as cadmium source, and the cadmium content in the soil was adjusted to 0.8 mg / kg (calculated as pure cadmium).

[0055] The soil remediation agents of Example 1 and Comparative Examples 1-6 were directly mixed into 1 kg of conditioned soil for remediation. The method of adding the soil remediation agents is shown in Table 1.

[0056] Table 1 Adding Method

[0057] The soil was remediated according to the treatment methods in Table 1. After 40 days of remediation, the soil pH, available cadmium content, and soil enzyme activity were tested. The test results are shown in Tables 2 and 3.

[0058] Table 2. Available cadmium content and pH of soil

[0059] Table 3 Soil enzyme activity

[0060] As shown in Table 2, the soil remediated by the soil remediation agent prepared in Example 1 of this invention had a cadmium content lower than the screening or control values ​​specified in GB15618-2018, and the content of effective cadmium was significantly reduced compared with the blank group. The pH value increased from acidic to neutral, indicating that the soil remediation agent prepared in this invention has a significant effect on regulating soil pH and cadmium pollution. Through the synergistic pathway of acid-base regulation-chemical fixation-microbial transformation-organic complexation, it transforms the highly active and mobile cadmium form in the soil into a stable state, thereby reducing its bioavailability and environmental risk.

[0061] As shown in Table 3, none of the applied treatments had a toxic effect on soil enzyme activity; on the contrary, they increased enzyme activity to varying degrees, indicating that the experimental treatments helped improve soil biological fertility. Treatment 7, in particular, showed outstanding performance in enhancing soil overall metabolism (CAT) and nitrogen cycling (Urease). The soil remediated by the soil remediation agent prepared in Example 1 of this invention showed the greatest change in urease, indicating that the soil remediation agent of Example 1 greatly promoted the soil nitrogen transformation capacity. Catalase levels continued to rise from 19.14 in the control to 36.96 in treatment 7, indicating that the soil remediation agent of Example 1 effectively enhanced the metabolic activity and detoxification capacity of soil microorganisms.

[0062] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A bio-composite soil remediation agent based on marine waste, characterized in that, Composed of shell powder, seaweed extract, and microbial inoculants, the bio-composite soil remediation agent based on marine waste contains microbial inoculants with a viable count of 1~5×10⁻⁶. 8 CFU / g; the mass ratio of the shell powder to the seaweed extract is 1~10:0.1~1.

2. The bio-composite soil remediation agent based on marine waste according to claim 1, characterized in that, The mass ratio of the shell powder to the seaweed extract is 10:

1.

3. The bio-composite soil remediation agent based on marine waste according to claim 1, characterized in that, The seaweed extract contains ≥50% seaweed polysaccharides.

4. The bio-composite soil remediation agent based on marine waste according to claim 1, characterized in that, The microbial agent is one or more of Bacillus subtilis, Bacillus subtilis, and Bacillus mucilaginosus.

5. The preparation method of the bio-composite soil remediation agent based on marine waste according to any one of claims 1 to 4, characterized in that, Includes the following steps: A soil remediation agent is obtained by mixing shell powder, seaweed extract, and microbial inoculant.

6. The application of the marine waste-based bio-composite soil remediation agent according to any one of claims 1 to 4 in the remediation of acidic, cadmium-contaminated soil.

7. A soil remediation method, characterized in that, The process includes the following steps: applying the marine waste-based bio-composite soil remediation agent as described in any one of claims 1 to 4 to the surface of acidic, cadmium-contaminated soil, rotary tilling to mix the soil conditioner with the soil, and leaving it for 40 days to reduce acidity and cadmium pollution.

8. The soil remediation method according to claim 7, characterized in that, The rotary tillage depth is 0~20cm; the acidic, cadmium-contaminated soil has a pH ≤ 5.5 and a cadmium content of 0.8~1.5mg / kg.

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