Electrode exchange direct current electrodynamics assisted phytoremediation soil

Abstract

The utility model discloses an electrode exchange direct current electrodynamics assisted phytoremediation soil, which belongs to the technical field of soil reactors, and comprises a rectangular acrylic mold, the acrylic mold is of a box-shaped structure with an opening at the upper end, and transparent acrylic plates are symmetrically arranged in the acrylic mold left and right. Heavy metal contaminated soil is filled between the transparent acrylic plates, plants are planted in the heavy metal contaminated soil, an electrode is arranged in the heavy metal contaminated soil, and the positive electrode and the negative electrode of the electrode are connected with a power-up device through electric wires; the power-up device is powered on for 8-12 hours every day, and the current direction is changed once before each time of power-on. According to the utility model, heavy metal pollutants are promoted to gather at root systems, and the effect of adsorbing and removing heavy metals in soil by plant rhizomes is improved.

Description

A DC electrodynamic assisted phytoremediation of soil using electrode exchange Technical Field

[0001] This invention relates to the field of soil reactor technology, and in particular to a direct current electrodynamics-assisted phytoremediation of soil using electrode exchange. Background Technology

[0002] Heavy metal pollution in soil has garnered significant attention due to its substantial ecological and health hazards. Soil possesses the capacity to absorb and store various substances, bearing approximately 90% of environmental pollutants. However, soil's self-purification capacity is limited; once heavy metals enter the soil, they are difficult to eliminate or dilute through natural degradation. Heavy metals in the soil can stress plant root cells, increasing membrane permeability and damaging cell membranes. This can lead to imbalances in binding enzymes and intracellular enzymes, as well as the entry of toxic substances and the leakage of intracellular substances, ultimately causing plant death. Due to the migration and accumulation characteristics of heavy metal pollutants, the concentration of heavy metals in organisms can increase tens of thousands of times compared to the environmental medium. Heavy metals enter the human body step by step along the food chain and accumulate over a long period, posing a significant threat to human health. In the human body, heavy metals can strongly interact with proteins and various enzymes, rendering them inactive. They may also accumulate in certain organs. If the levels exceed the body's tolerance limits, it can cause acute, subacute, and chronic poisoning, posing a serious threat to human health.

[0003] Many soil remediation technologies have been developed both domestically and internationally. From the perspective of remediation principles, soil remediation technologies can be broadly classified into three categories: physical remediation, chemical remediation, and bioremediation. Physical remediation of heavy metal-contaminated soil typically provides a more thorough and stable remediation effect, but it involves large-scale engineering, high investment, and can easily lead to a decrease in soil fertility. Chemical remediation suffers from drawbacks such as the consumption of large amounts of chemical agents, high investment, operational difficulties, and the potential harm of chemical reagents to soil organisms and the soil environment. Bioremediation, on the other hand, refers to the use of microorganisms, plants, or animals to degrade, stabilize, or remove pollutants in the soil under certain conditions, restoring the polluted ecosystem to its normal function. Compared with traditional physical and chemical remediation technologies, bioremediation of contaminated soil has the following advantages: ① The physical, chemical, and biological characteristics of the soil remain largely unchanged, generally without damaging the soil environment required for plant growth, and without generating secondary pollution; ② Under certain conditions, it can achieve the mineralization of organic pollutants; ③ It offers diverse treatment methods, allowing for both in-situ and ex-situ remediation depending on the conditions; ④ It has low treatment costs; ⑤ It has a wide range of applications, capable of treating different types and degrees of contaminated soil. Phytoremediation is an environmental pollution remediation technology that utilizes certain plants and their symbiotic microbial systems capable of tolerating and hyperaccumulating heavy metals to remove pollutants. Plants can only accumulate soluble heavy metals near the rhizosphere, and their remediation efficiency is limited by the accessibility and bioavailability of heavy metals in the soil. Some plants with high heavy metal absorption are called hyperaccumulators, but these plants have long growth periods, resulting in lengthy remediation times. Factors limiting their heavy metal absorption rate include relatively small biomass, short root systems, the selectivity and feasibility exhibited by the plant type, and the slow transport process on the plant root surface. On the other hand, due to the low activity of heavy metals, the effectiveness of phytoremediation is relatively low. Adding chemical reagents can improve heavy metal activity; for example, surfactants can increase the water solubility of pollutants and promote the dissolution of heavy metals and organic matter. Chelating agents such as ethylenediaminetetraacetic acid (EDTA), N,N'-(1,2-ethanediyl)bisaspartic acid, and diethyltriaminepentaacetic acid (DTA) can react with metals to form complexes that facilitate diffusion in soil and plant tissues, leading to plant absorption. However, this approach carries risks such as heavy metal leaching from the soil, inhibited plant growth, and water pollution. In contrast, electrokinetic remediation (EKAPR) offers advantages such as rapid and efficient remediation, ease of operation, economy, and preservation of the original natural ecosystem, as it eliminates the need for extensive excavation and transportation of contaminated soil. To address the limitations of phytoremediation, including long remediation times, limited root accessibility, and low proportions and slow replenishment of bioavailable pollutants in the rhizosphere, researchers have proposed applying a low-intensity electric field to the contaminated soil near plant rhizosphere to enhance the remediation effect of plants on soil pollution—an technique known as electrokinetic-assisted phytoremediation (EKAPR).

[0004] In the EKAPR system, an applied electric field may promote the utilization of nutrients in the soil, and pollutants may desorb at the soil-water interface and migrate to the rhizosphere, thereby overcoming or reducing the limitations of phytoremediation. Direct current enhances remediation efficiency by increasing the diffusion of pollutants and microorganisms, and also improves the absorption efficiency of heavy metals by plants. Considering the current status both domestically and internationally, electro-enhanced phytoremediation is currently the most feasible method for heavy metal removal, which couples electrodynamic remediation with phytoremediation to activate heavy metals in the soil and enhance the translocation and accumulation of heavy metals by plants.

[0005] It has the following advantages:

[0006] (1) Enhance soil bioremediation treatment: Electrical stimulation of soil and plants to achieve the enrichment of heavy metals and promote plant adsorption.

[0007] (2) Stable operation: Electrodynamic assisted phytoremediation (EKAPR) technology can be operated simply by applying electricity. The operation is simple and the direct current can provide a relatively stable electric field, which helps to ensure the relative stability of the electrodynamic process.

[0008] (3) No secondary pollution: Compared with traditional physical and chemical remediation methods, phytoremediation uses the physiological metabolic processes of plants to absorb, transform or fix pollutants in the soil without adding additional chemical agents to the soil, thus avoiding the risk of secondary pollution.

[0009] (4) Facilitates heavy metal recovery: The plants used for remediation accumulate heavy metals mainly in their above-ground parts, such as stems and leaves. This makes harvesting the plants relatively easy, as the biomass enriched with heavy metals can be obtained by harvesting the above-ground parts, avoiding the complex operations and high costs of directly extracting heavy metals from the soil.

[0010] However, electrodynamic assisted phytoremediation (EKAPR) technology also has some drawbacks:

[0011] (1) Low remediation efficiency: For some complex contaminated soils, such as soils containing multiple heavy metals or soils with organic pollutants and heavy metals, the remediation efficiency of EKAPR technology may be low, and it is difficult to achieve the ideal remediation effect in a short period of time.

[0012] (2) Changes in soil properties: Under the influence of direct current, water electrolysis occurs near the electrodes. Hydrogen ions are generated at the anode, increasing the acidity of the soil near the anode; hydroxide ions are generated at the cathode, increasing the alkalinity of the soil near the cathode. Changes in soil pH, temperature, and oxygen content can affect the survival and activity of soil microorganisms. During electrokinetic remediation, soil salts may accumulate near the electrodes as ions migrate.

[0013] Based on this, this invention proposes a DC electrodynamic-assisted plant remediation method using electrode exchange. Summary of the Invention

[0014] The purpose of this invention is to provide an electrode-exchange DC electrodynamic-assisted plant remediation of soil, thereby solving the aforementioned problems.

[0015] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0016] This invention relates to a DC electrodynamic-assisted phytoremediation system for electrode exchange, comprising a rectangular acrylic mold, which is a box-shaped structure with an open top. The interior of the acrylic mold contains symmetrically arranged transparent acrylic plates, with heavy metal-contaminated soil filling the spaces between the plates. Plants are grown within the heavy metal-contaminated soil, and electrodes are disposed within the soil. The positive and negative terminals of the electrodes are connected to a power supply device via wires. The power supply device is powered on for 8-12 hours daily, with the current direction changed before each power-on.

[0017] Furthermore, the voltage gradient controlled by the power supply device is 1V / cm.

[0018] Furthermore, the electrode includes two symmetrically distributed vertical electrodes and a horizontal electrode located at the bottom of the acrylic mold; the vertical electrodes and the horizontal electrodes accumulate charges with opposite signs, and the vertical electrodes and the horizontal electrodes are 10 cm apart in the horizontal direction.

[0019] Furthermore, both the vertical and horizontal electrodes are made of graphite rods, 12cm long, 3cm wide, and 1cm thick.

[0020] Furthermore, a multimeter for measuring the device's current variation is connected in series on the wire between the electrode and the power supply device.

[0021] Furthermore, the selected plants are those with high heavy metal adsorption capacity and alkali tolerance.

[0022] Compared with the prior art, the beneficial technical effects of this utility model are as follows:

[0023] This novel electrode-exchange direct current electrodynamic-assisted phytoremediation of soil utilizes different electrode arrangements. Heavy metal cations in the soil move towards the cathode, while other negatively charged organic ions and colloidal particles move towards the anode. This alters the soil moisture distribution (under the influence of the electric field, water molecules in the soil pores move towards the surface of charged soil particles, and simultaneously migrate from the anode to the cathode as a whole). This changes the community structure of microorganisms, and the activity of microbial enzymes is affected by electrical stimulation, thereby promoting the accumulation of heavy metal pollutants in the roots and improving the desorption and removal effect of heavy metals from the soil by plant roots and stems. Attached Figure Description

[0024] The present invention will be further described below with reference to the accompanying drawings.

[0025] Figure 1 is a schematic diagram of the DC electrodynamics-assisted phytoremediation of soil structure using electrode exchange according to this invention.

[0026] Figure 2 shows the electrophoretic diagram of cation and anion migration;

[0027] Explanation of reference numerals in the attached diagram: 1. Transparent acrylic sheet; 2. Heavy metal contaminated soil; 3. Plant; 4. Acrylic mold; 5. Electrode; 6. Wire; 7. Power supply device. Detailed Implementation

[0028] As shown in Figures 1-2, an electrode-exchange DC electrodynamic assisted plant remediation soil includes a rectangular acrylic mold 4, which is a box-shaped structure with an open top. Transparent acrylic plates 1 are symmetrically installed inside the acrylic mold 4, and heavy metal-contaminated soil 2 is filled between the transparent acrylic plates 1. Several ventilation holes are provided on the transparent acrylic plates 1, and a hollow structure is formed between the end face of the transparent acrylic plates 1 away from the heavy metal-contaminated soil 2 and the side wall of the acrylic mold 4. This hollow structure supplies air to the soil, maintains the balance of various gases in the soil, ensures the suitability of the gas composition in the soil, and enables plants to grow healthily.

[0029] Plants 3 are planted in the heavy metal contaminated soil 2. The plants 3 are selected from plants with high heavy metal adsorption capacity and alkali tolerance, such as Iris tectorum and Haloxylon ammodendron.

[0030] Electrodes 5 are installed inside the heavy metal contaminated soil 2. The positive and negative terminals of the electrodes 5 are connected to an electric power supply device 7 via wires 6. The electrodes 5 include two symmetrically distributed vertical electrodes and a horizontal electrode located at the bottom of the acrylic mold 4. The vertical and horizontal electrodes accumulate charges of opposite signs and are 10 cm apart horizontally. Both the vertical and horizontal electrodes are made of graphite rods, 12 cm long, 3 cm wide, and 1 cm thick. The electric power supply device 7 is powered on for 8-12 hours per day. Before each power-on, the current direction is changed. This can be achieved by switching relay contacts to change the connection between the graphite rod and the positive and negative terminals of the power supply, such as:

[0031] Normally closed contact: The vertical electrode is connected to the positive terminal of the power supply, and the horizontal electrode is connected to the negative terminal (forward current);

[0032] Normally open contact: The vertical electrode is connected to the negative terminal of the power supply, and the horizontal electrode is connected to the positive terminal (reverse current).

[0033] The voltage gradient controlled by the power supply device 7 is 1V / cm. The voltage gradient is essentially the electric field strength (E), which refers to the voltage change per unit distance. The formula is:

[0034]

[0035] Where U is the voltage across the electrodes (unit: V), and d is the distance between the two electrodes (unit: cm).

[0036] The physical meaning of 1V / cm: The voltage difference per centimeter is 1V, that is, the electric field strength E = 1V / cm = 100V / m.

[0037] A multimeter for measuring the device's current variation is connected in series on the wire 6 between the electrode 5 and the power supply device 7.

[0038] The usage process of this utility model is as follows:

[0039] Plants with high heavy metal adsorption capacity and alkali tolerance were selected and cultured for approximately 42 days. The specific process is as follows:

[0040] First, the prepared simulated heavy metal contaminated soil 2 is filled into the cavity formed between the transparent acrylic plates 1, with the soil height being 15cm, and the soil must be mixed evenly.

[0041] Then, plants with similar age, growth, number of leaves, and leaf area density were selected from the plant population and planted in heavy metal contaminated soil 2, and watered regularly to ensure that the soil fully absorbs water.

[0042] Finally, the voltage gradient of the power supply device 7 is controlled to be 1V / cm, and it is powered on for 12 hours a day. The current direction is changed once before each power-on to achieve the effect of anode and cathode exchange.

[0043] In the above process, vertical electrodes are placed on the left and right sides of the three root systems of the plant, and horizontal electrodes are placed at the bottom center of the three root systems, forming an electric field. The direction of the direct current electric field is from the anodes on the left and right sides to the cathode in the middle. Since the anodes are positively charged and the cathodes are negatively charged, the electric field lines start from the anodes and converge at the cathode rod in the middle. Heavy metal cations in the soil migrate against the direction of the electric field, i.e., from the anode to the cathode; while heavy metal anions (such as certain anionic pollutants) move along the direction of the electric field, from the cathode to the anode. This gives pollutants with different charges in the soil specific migration paths, enhances the effect of electrodynamic assisted phytoremediation (EKAPR), improves the enrichment of heavy metals, and further promotes plant adsorption.

[0044] The embodiments described above are merely preferred embodiments of the present utility model and are not intended to limit the scope of the present utility model. Various modifications and improvements made to the technical solutions of the present utility model by those skilled in the art without departing from the spirit of the present utility model should fall within the protection scope defined by the claims of the present utility model.

Claims

1. A direct current electrodynamic assisted phytoremediation method for electrode exchange, characterized in that: The device includes a rectangular acrylic mold (4), which is a box-shaped structure with an open top. Transparent acrylic plates (1) are symmetrically arranged inside the acrylic mold (4). Heavy metal contaminated soil (2) is filled between the transparent acrylic plates (1). Plants (3) are planted in the heavy metal contaminated soil (2). Electrodes (5) are arranged inside the heavy metal contaminated soil (2). The positive and negative poles of the electrodes (5) are connected to a power supply device (7) through wires (6). The power supply device (7) is powered on for 8-12 hours a day, and the current direction is changed once before each power supply.

2. The DC electrodynamic assisted phytoremediation of soil with electrode exchange according to claim 1, characterized in that: The power supply device (7) controls the voltage gradient to be 1V / cm.

3. The electrode-exchange DC electrodynamic-assisted phytoremediation of soil according to claim 1, characterized in that: The electrode (5) includes two symmetrically distributed vertical electrodes and a horizontal electrode located at the bottom of the acrylic mold (4); the vertical electrodes and the horizontal electrodes have opposite signs of accumulated charge, and the vertical electrodes and the horizontal electrodes are 10 cm apart in the horizontal direction.

4. The electrode-exchange DC electrodynamic-assisted phytoremediation of soil according to claim 3, characterized in that: Both the vertical and horizontal electrodes are made of graphite rods, 12cm long, 3cm wide, and 1cm thick.

5. The DC electrodynamic assisted phytoremediation of soil with electrode exchange according to claim 1, characterized in that: A multimeter for measuring the device current is connected in series on the wire (6) between the electrode (5) and the power supply device (7).

6. The DC electrodynamic assisted phytoremediation of soil with electrode exchange according to claim 1, characterized in that: The plants (3) selected are those with high heavy metal adsorption capacity and alkali resistance.

Images