CN104515911A - Device and method for monitoring electric field for electrokinetic remediation of contaminated soil - Google Patents

Abstract

The invention relates to an electric field monitoring device and method for electrodynamic restoration of polluted soil. The device includes a probe and a main control unit; the main control unit includes an electrode polarity detection module, a reference negative pressure calibration module, an A/D module, and a field strength Conversion module, control module. The probe is inserted into the electrically repaired soil, and the collected voltage signal is output to the main control unit. The main control unit performs benchmark correction, analog-to-digital conversion on the voltage signal, and calculates the electric field strength value according to the preset parameters. The method includes processing the voltage signal of the polluted soil collected by the probe, and calculating the electric field strength value according to the set parameters, so as to monitor the electric field strength in the electrokinetic restoration process of the polluted soil in real time. The invention can realize the real-time monitoring of the electric field intensity in the electrokinetic restoration process of polluted soil, and effectively improve the electrokinetic restoration efficiency.

Description

An electric field monitoring device and method for electrokinetic remediation of polluted soil

technical field

The invention relates to the technical field of soil electric field monitoring in electrokinetic restoration, in particular to an electric field monitoring device and method for electrokinetic restoration of polluted soil.

Background technique

Electrodynamic remediation of polluted soil is currently an emerging technology. The electrokinetic remediation of polluted soil is to insert electrodes into the polluted soil to form an electrode matrix, apply a weak direct current to form an electric field, and under the action of electrokinetic effect, the pollutants in the soil can be effectively removed.

The previous research results showed that during the electrokinetic remediation process, the degradation efficiency of organic pollutants in soil was positively correlated with the potential drop (Li et al., 2014), and the migration rate of heavy metal pollutants was also closely related to the electric field strength. Therefore, electric field indicators such as electric field strength are important factors affecting the efficiency of electrokinetic remediation of contaminated soil.

As a complex medium different from water, the spatial distribution of the electric field intensity of soil under the condition of an external electric field can only be obtained by theoretical calculation (Li et al., 2010), and the inhomogeneity of the soil medium causes the actual electric field intensity Spatial difference from the theoretical value. In addition, the electric field index is not only affected by the applied voltage, but also affected by soil properties, such as soil type, moisture content, total amount of base ions, etc. In the process of electrokinetic remediation of contaminated soil, electrokinetic effects such as electrolysis and electromigration all cause changes in electrical indicators such as electric field strength.

How to monitor the temporal and spatial changes of electrical indicators such as electric field intensity in the process of electrokinetic restoration of contaminated soil in real time is of great significance for regulating the distribution of electric field in the process of electrokinetic restoration, improving the spatial uniformity of electrokinetic restoration efficiency, and maintaining the efficiency of electrokinetic restoration.

Contents of the invention

In order to monitor the temporal and spatial changes of electric field indicators such as electric field intensity in the process of electrokinetic restoration of polluted soil in real time, an electric field monitoring device and method for electrokinetic restoration of polluted soil are provided.

The technical solution adopted by the present invention to achieve the above purpose is: an electric field monitoring device for electric restoration of polluted soil, including a probe and a main control unit;

The probes are evenly inserted into the electric restoration soil, and are connected to the main control unit through wires for collecting analog voltage signals in the electric restoration soil and outputting them to the main control unit;

The main control unit is respectively connected to the probe, the constant negative terminal of the DC power supply, and the electrode, and is used to adjust the input analog voltage signal to a positive value, perform benchmark correction, and calculate the electric field strength value, so as to monitor in real time the process of electric restoration of polluted soil the electric field strength.

The probe is an iron-nickel alloy probe with a length of 5 cm to 15 cm and a diameter of 0.5 cm to 1.2 cm.

The main control unit includes an electrode polarity detection module, a reference negative pressure calibration module, an A/D module, a field strength conversion module, and a control module;

The electrode polarity detection module is respectively connected to the electrode and the control module, and is used to detect the positive and negative electrode polarity, and convert the first digital signal representing the positive and negative electrode polarity to the control module;

The reference negative pressure calibration module is respectively connected to the constant negative terminal of the DC power supply and the control module, and is used to receive the reference negative pressure value output by the constant negative terminal of the DC power supply and convert it into a second digital signal and output it to the control module;

The A/D module is respectively connected to the probe and the control module, and is used to receive the analog voltage signal output by the probe and convert it into a third digital signal representing the soil voltage and output it to the control module;

The control module is respectively connected to the electrode polarity detection module, the reference negative pressure calibration module, the A/D module and the field strength conversion module for receiving the first digital signal, the second digital signal and the third digital signal, and according to the first The digital signal and the second digital signal adjust the third digital signal to a positive value and perform reference correction, and output the fourth digital signal representing the corrected soil voltage to the field strength conversion module;

The field strength conversion module is connected to the control module, and is used to calculate and convert the received fourth digital signal, as well as the preset probe spatial relative position coordinates, electrode spacing, and reference negative pressure value, into an electric field strength value;

The A/D module adopts A/D678 chip.

The control module adopts ARM7 microprocessor.

When the first digital signal is 1, it means that the detected electrode polarity is positive at this time, and the control module does not change the positive or negative value of the third digital signal, and the third digital signal is still positive; the first digital signal is 0 When , it means that the polarity of the electrode is detected to be negative at this time, and the control module changes the value of the third digital signal to be positive or negative, and the third digital signal takes an absolute value.

An electric field monitoring method for electrokinetic remediation of contaminated soil, comprising the following steps:

a. Insert the electrodes in the polluted soil, and keep the position of the electrodes in the electrokinetic remediation soil evenly distributed; the electrodes are graphite electrodes, the number is M×N, where M and N are positive integers, and are used for the electrokinetics of polluted soil Remediation; insert probes in contaminated soil and keep the position of the probes in the electric remediation soil evenly distributed;

b. Pre-set the relative position coordinates of the probe in the main control unit, set the electrode spacing, and the reference negative pressure value; adjust the polarity switching controller to set the polarity switching interval;

c. Start the monitoring device and start monitoring the electric field change:

The probe outputs the collected analog voltage signal in the electrodynamic repair soil to the A/D module inside the main control unit, converts it into a third digital signal representing the soil voltage, and outputs it to the control module; the electrode polarity detection module detects the detected signal The first digital signal of positive and negative electrode polarity is output to the control module; the reference negative pressure calibration module converts the received reference negative voltage value of the constant negative terminal of the DC power supply into the second digital signal and outputs it to the control module; the control module receives the first 1 digital signal, the 2nd digital signal and the 3rd digital signal, and according to the 1st digital signal and the 2nd digital signal, adjust the 3rd digital signal to a positive value and perform reference correction, and output the 4th digital signal representing the corrected soil voltage To the field strength conversion module; the field strength conversion module calculates and converts the received 4th digital signal, as well as the preset probe spatial relative position coordinates, electrode spacing, and reference negative pressure value into electric field strength values, so as to monitor polluted soil in real time Electric field strength during electrokinetic restoration.

The present invention has the following advantages and beneficial effects:

1. Soil is different from water and other homogeneous environmental media. Changes in soil particles and moisture will affect the value of the electric field intensity. The present invention overcomes the influence of the electric field in the polluted soil by electrodynamic restoration by the complex soil medium, and realizes the complex soil medium condition. Monitoring of indicators such as electric field strength.

2. The monitoring device completes the calibration and conversion of electrical signals through a high-conductivity probe and a main control unit with functions of polarity detection, benchmark correction, and analog-to-digital conversion, and realizes real-time monitoring of the electric field strength of the polluted soil repaired electrically, thereby Optimize the electric field conditions to improve the electrokinetic remediation efficiency of polluted soil.

Description of drawings

Fig. 1 is the composition schematic diagram of monitoring device of the present invention;

Fig. 2 is a schematic diagram of the composition of the main control unit of the monitoring device of the present invention;

Figure 3 is a schematic diagram of electrode polarity and probe layout for electrodynamic remediation of oil-polluted brown soil;

Fig. 4 is the monitoring result of the electric field strength of the electrodynamic restoration of oil polluted brown soil;

Figure 5 is a schematic diagram of electrode polarity and probe layout for electrokinetic restoration of cadmium-contaminated sandy soil;

Figure 6 shows the monitoring results of the electric field strength for electrokinetic remediation of cadmium-contaminated sand.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1: an electric field monitoring device for electrodynamic remediation of contaminated soil includes a probe 1 and a main control unit 2; the probe 1 is an iron-nickel alloy probe with a length of 5 cm to 15 cm and a diameter of 0.5 cm to 1.2 cm, evenly inserted into the electric restoration soil 3, and connected to the main control unit 2 through wires, used to collect the analog voltage signal in the electric restoration soil 3 and output to the main control unit 2; the main control unit 2 is respectively connected to the probe 1, The constant negative terminal of the DC power supply 4 and the electrode 6 are used to adjust the input analog voltage signal to a positive value, perform benchmark correction, and calculate the electric field strength value, so as to monitor the electric field strength in the process of electrokinetic restoration of polluted soil in real time.

The DC power supply 4 is connected to the polarity switching controller 5, and the polarity switching controller 5 is connected to the electrode 6; the DC power supply 4 is used to provide a DC power supply of 20V to 36V for the electrode 6; the polarity switching controller 5 includes a time controller and a relay, It is used to control the polarity of the electrode 6 to switch between positive and negative according to the set time interval; the electrode 6 is a graphite electrode, the number is M×N, where M and N are both positive integers, and are used to pollute the soil electrical restoration.

As shown in Figure 2: the main control unit 2 includes an electrode polarity detection module 7, a reference negative pressure calibration module 8, an A/D module 9, a field strength conversion module 10, and a control module 11; the electrode polarity detection module 7 is respectively Connecting the electrode 6 and the control module 11 is used to detect the positive and negative polarity of the electrode 6, and convert it into a first digital signal representing the positive and negative polarity of the electrode 6 and output it to the control module 11; the reference negative pressure calibration module 8 is respectively Connect the constant negative terminal of the DC power supply 4 and the control module 11, for receiving the reference negative voltage value output by the constant negative terminal of the DC power supply 4 and converting it into a second digital signal and outputting it to the control module 11; the A/D module 9 is 12 bits The A/D converter adopts the A/D678 chip, which is respectively connected to the probe 1 and the control module 11, and is used to receive the analog voltage signal output by the probe 1 and convert it into a third digital signal representing the soil voltage and output it to the control module 11; Described control module 11 adopts ARM7 microprocessor, connects electrode polarity detection module 7, reference negative pressure calibration module 8, A/D module 9 and field intensity conversion module 10 respectively, is used for receiving the 1st digital signal, the 2nd digital signal. signal and the third digital signal, and according to the first digital signal and the second digital signal, adjust the third digital signal to a positive value and perform reference correction, and output the fourth digital signal representing the corrected soil voltage to the field strength conversion module 10 The field strength conversion module 10 is connected to the control module 11, and is used to calculate and convert the received 4th digital signal and the preset spatial relative position coordinates of the probe 1, the distance between the electrodes 6, and the reference negative pressure value into an electric field strength value, Therefore, the electric field strength during the electrokinetic remediation of contaminated soil can be monitored in real time.

Wherein, when the first digital signal is 1, it means that it is detected that the polarity of the electrode 6 is positive at this time, and the control module 11 does not change the positive or negative value of the third digital signal, and the third digital signal is still positive; the first digital signal When it is 0, it means that the polarity of the electrode 6 is detected to be negative at this time, and the control module 11 changes the value of the third digital signal to be positive or negative, and the third digital signal takes an absolute value.

Example 1

The contaminated soil repaired in this embodiment is the oil-contaminated soil configured in the laboratory. The soil collected is brown soil, which is passed through a 2mm sieve after natural air-drying in the room. The oil is collected from an oil pit in Shuguang Oil Production Plant of Liaohe Oilfield, and the oil content is 50g. /kg oil-contaminated soil. After oil and soil are mixed evenly, divide into 4 treatments, adjust the moisture content with deionized water to 5%, 10%, 15% and 25% respectively, and pack into the soil box respectively (long 30cm * wide 30cm * high 10cm ).

Arrange four electrodes 6 in the polluted soil as shown in Figure 3. The electrode 6 is made of graphite electrodes with a diameter of 1cm and a height of 11cm. The applied voltage is 30V, and the polarities of two adjacent electrodes are kept opposite. By adjusting the polarity switch The controller 5 realizes the timing switching of the electrode polarity interval of 4h. Arrange the probe 1 in the polluted soil according to Fig. 3, the material of the probe 1 is an iron-nickel alloy, the length of the probe is 10 cm, and the diameter is 1 cm.

The specific operation process includes:

The probe 1 is evenly inserted into the electric restoration soil 3, and is connected with the A/D module 9 inside the main control unit 2 through wires; the electrode 6 is connected with the electrode polarity detection module 7 inside the main control unit 2 through wires; the DC power supply 4 The constant negative terminal of is connected to the reference negative pressure calibration module 8 inside the main control unit 2 through wires.

After the connection is completed, the control flow is as follows:

Start the monitoring device, in the main control unit 2, preset the relative position coordinates of the probe space (as shown in Figure 5), the distance between the electrodes 6 is 30cm, the reference negative pressure value is 0V, the applied voltage is 30V, and the data acquisition time interval is 2h, start the data acquisition of the electric signal.

The probe 1 outputs the collected analog voltage signal in the electrically repaired soil 3 to the A/D module 9 inside the main control unit 2, converts it into a third digital signal representing the soil voltage, and outputs it to the control module 11; the electrode polarity detection module 7 Output the detected first digital signal representing the positive and negative polarity of the electrode 6 to the control module 11; the reference negative pressure calibration module 8 converts the received reference negative voltage value of the constant negative terminal of the DC power supply 4 into the second digital signal The signal is output to the control module 11; the control module 11 receives the first digital signal, the second digital signal and the third digital signal, and adjusts the third digital signal to a positive value and performs reference correction according to the first digital signal and the second digital signal , output the 4th digital signal representing the corrected soil voltage to the field strength conversion module 10; the field strength conversion module 10 receives the 4th digital signal, and the preset spatial relative position coordinates of the probe 1, the distance between the electrodes 6, and the reference The negative pressure value is calculated and converted into the electric field strength value, so as to monitor the electric field strength in the process of electrokinetic remediation of polluted soil in real time.

Verification of electric field strength monitoring results and theoretical values:

Electric field strength is the core indicator of electrokinetic restoration. It can be seen from Table 1 and Figure 4 that, compared with the calculation results of the electric field strength based on the point charge model, it can be seen that the soil moisture content has a great influence on the correlation between the monitored value and the theoretical value. Among them, when the soil moisture content is 25%, the linear correlation between the monitoring value and the theoretical value is good, the slope is approximately 1, and the difference between the monitoring value and the theoretical value is the smallest. Therefore, under the condition of suitable moisture content, the monitoring results can truly reflect the electric field strength of the electrokinetic remediation soil.

The test result of table 1 embodiment 1

Experimental treatment Moisture content (%) linear fit R ² Experiment 1 5 y=0.1484x+0.1252 0.990 Experiment 2 10 y=0.6592x+0.0511 0.992

Experiment 3 15 y=0.8611x+0.0187 0.992 Experiment 4 25 y=0.9903x-0.0081 0.997

Example 2

The polluted soil to be repaired is heavy metal cadmium polluted soil, the soil is sandy soil, and the cadmium content is 10ppm. Divide into 4 treatments, adjust moisture content to 10%, 15%, 20% and 25% with deionized water respectively, and pack into soil boxes (length 20cm×width 10cm×height 10cm) respectively.

Four electrodes 6 are arranged in the polluted soil as shown in Figure 5. The electrode 6 is made of graphite electrode with a diameter of 1 cm and a height of 11 cm. The applied voltage is 20V, and the polarity of the electrodes is not switched. Arrange the probe 1 in the polluted soil as shown in Fig. 5, the material of the probe 1 is an iron-nickel alloy, the length of the probe is 10 cm, and the diameter is 1 cm.

The specific operation process includes:

The probe 1 is evenly inserted into the electric restoration soil 3, and is connected with the A/D module 9 inside the main control unit 2 through wires; the electrode 6 is connected with the electrode polarity detection module 7 inside the main control unit 2 through wires; the DC power supply 4 The constant negative terminal of is connected to the reference negative pressure calibration module 8 inside the main control unit 2 through wires.

After the connection is completed, the control flow is as follows:

Start the monitoring device, in the main control unit 2, pre-set the relative position coordinates of the probe space (as shown in Figure 5), the size of the distance between the electrodes 6 is 20cm; the reference negative pressure value is 0V, the applied voltage is 20V, and the data acquisition time interval is 1h, start the data acquisition of the electrical signal.

The probe 1 outputs the collected analog voltage signal in the electrically repaired soil 3 to the A/D module 9 inside the main control unit 2, converts it into a third digital signal representing the soil voltage, and outputs it to the control module 11; the electrode polarity detection module 7 Output the detected first digital signal representing the positive and negative polarity of the electrode 6 to the control module 11; the reference negative pressure calibration module 8 converts the received reference negative voltage value of the constant negative terminal of the DC power supply 4 into the second digital signal The signal is output to the control module 11; the control module 11 receives the first digital signal, the second digital signal and the third digital signal, and adjusts the third digital signal to a positive value and performs reference correction according to the first digital signal and the second digital signal , output the 4th digital signal representing the corrected soil voltage to the field strength conversion module 10; the field strength conversion module 10 receives the 4th digital signal, and the preset spatial relative position coordinates of the probe 1, the distance between the electrodes 6, and the reference The negative pressure value is calculated and converted into the electric field strength value, so as to monitor the electric field strength in the process of electrokinetic remediation of polluted soil in real time.

Verification of monitoring results and theoretical values:

It can be seen from Table 2 and Figure 6 that when the moisture content of the sand is greater than 20%, the monitored value has a good linear correlation with the theoretical value, the slope is approximately 1, and the difference between the two is small. Therefore, under the condition of suitable moisture content, the monitoring results can truly reflect the spatial distribution of the electric field intensity of the electrokinetic remediation soil.

The test result of table 2 embodiment 2

Experimental treatment Moisture content (%) linear fit R ² Experiment 1 10 y=0.0707x+0.1625 0.835 Experiment 2 15 y=0.3902x+0.2771 0.972 Experiment 3 20 y=0.9424x+0.1860 0.998 Experiment 4 25 y=0.9707x+0.0576 0.997

The above content is a further detailed description of the present invention in conjunction with specific preferred implementation cases, and it cannot be assumed that the specific implementation of the present invention is limited thereto. On the premise of not departing from the concept of the present invention, some simple deduction or replacement can also be made, which should be considered as belonging to the protection scope of the present invention.

Claims (7)

1. An electric field monitoring device for electric restoration of polluted soil, characterized in that: comprising a probe (1), a main control unit (2); The probes (1) are evenly inserted into the electrodynamic restoration soil (3), and are connected to the main control unit (2) through wires for collecting analog voltage signals in the electrodynamic restoration soil (3) and outputting them to the main control unit ( 2); The main control unit (2) is respectively connected to the probe (1), the constant negative terminal of the DC power supply (4), and the electrode (6), and is used to adjust the input analog voltage signal to a positive value, perform benchmark calibration, and calculate the electric field Intensity value, so as to monitor the electric field intensity in the process of electrokinetic remediation of polluted soil in real time. 2. A kind of electric field monitoring device for electrodynamic remediation of polluted soil according to claim 1, it is characterized in that: described probe (1) is iron-nickel alloy probe, and probe length is 5cm～15cm, and diameter is 0.5cm～1.2cm. 3. A kind of electric field monitoring device for electrodynamic restoration of contaminated soil according to claim 1, characterized in that: the main control unit (2) includes an electrode polarity detection module (7), a reference negative pressure calibration module ( 8), A/D module (9), field strength conversion module (10), control module (11); The electrode polarity detection module (7) is connected to the electrode (6) and the control module (11) respectively, and is used to detect the positive and negative polarity of the electrode (6), and convert it into a positive and negative signal representing the positive and negative polarity of the electrode (6). The first digital signal is output to the control module (11); The reference negative pressure calibration module (8) is respectively connected to the constant negative terminal of the DC power supply (4) and the control module (11), for receiving the reference negative pressure value output by the constant negative terminal of the DC power supply (4) and converting it into the first 2 digital signals are output to the control module (11); The A/D module (9) is respectively connected to the probe (1) and the control module (11), and is used to receive the analog voltage signal output by the probe (1) and convert it into a third digital signal representing soil voltage and output it to the control module(11); The control module (11) is respectively connected to the electrode polarity detection module (7), the reference negative pressure calibration module (8), the A/D module (9) and the field strength conversion module (10), for receiving the first digital signal , the second digital signal and the third digital signal, and according to the first digital signal and the second digital signal, adjust the third digital signal to a positive value and perform reference correction, and output the fourth digital signal representing the corrected soil voltage to the field Strong conversion module (10); The field intensity conversion module (10) is connected to the control module (11), and is used for receiving the fourth digital signal, as well as the preset spatial relative position coordinates of the probe (1), the distance between the electrodes (6), and the reference negative pressure Values are calculated and converted to electric field strength values. 4. An electric field monitoring device for electrodynamic remediation of polluted soil according to claim 3, characterized in that: the A/D module (9) adopts an A/D678 chip. 5. An electric field monitoring device for electrodynamic remediation of polluted soil according to claim 3, characterized in that: the control module (11) adopts an ARM7 microprocessor. 6. An electric field monitoring device for electrokinetic remediation of contaminated soil according to claim 3, characterized in that: when the first digital signal is 1, it means that the polarity of the electrode (6) is detected to be positive at this time, The control module (11) does not change the positive and negative values of the third digital signal, and the third digital signal is still positive; when the first digital signal is 0, it means that the polarity of the electrode (6) is detected to be negative at this time, and the control module (11) Change the value of the third digital signal to be positive or negative, and take the absolute value of the third digital signal. 7. An electric field monitoring method for electrokinetic restoration of contaminated soil, characterized in that it comprises the following steps: a. Insert the electrode (6) in the polluted soil, and keep the position of the electrode (6) in the electrokinetic repair soil (3) to be evenly distributed; the electrode (6) is a graphite electrode, and the number is M×N, wherein M, N is a positive integer, and is used for electrokinetic restoration of polluted soil; inserting the probe (1) in the polluted soil, and keeping the positions of the probe (1) in the electrokinetic restoration soil (3) uniformly distributed; b. In the main control unit (2), pre-set the spatial relative position coordinates of the probe (1), set the electrode (6) spacing, and the reference negative pressure value; adjust the polarity switching controller (5) to set the polarity switching interval time; c. Start the monitoring device and start monitoring the electric field change: The probe (1) outputs the collected analog voltage signal in the electrically repaired soil (3) to the A/D module (9) inside the main control unit (2), converts it into a third digital signal representing the soil voltage, and outputs it to the control module (11); the electrode polarity detection module (7) outputs the first digital signal of the positive and negative polarity of the detected electrode (6) to the control module (11); the reference negative pressure calibration module (8) will receive The reference negative voltage value of the constant negative end of the DC power supply (4) is converted into the second digital signal and output to the control module (11); the control module (11) receives the first digital signal, the second digital signal and the third digital signal , and according to the 1st digital signal and the 2nd digital signal, adjust the 3rd digital signal to a positive value and perform benchmark correction, and output the 4th digital signal representing the corrected soil voltage to the field strength conversion module (10); the field strength conversion module (10) Calculate and convert the received fourth digital signal, and the preset spatial relative position coordinates of the probe (1), electrode (6) spacing, and reference negative pressure value into electric field strength values, so as to monitor the electric field of polluted soil in real time. Electric field strength during repair.