As the core of the new round of industrial revolution, the digital economy is a breakthrough for the economy to achieve green transformation. Its green, diverse and shared characteristics provide a possible path for cultivating new kinetic energy for economic development. In recent years, China’s digital economy industry has developed rapidly. From a domestic perspective, in 2019, the scale of the digital economy industry has increased from 2.6 trillion yuan in 2005 to 35.8 trillion yuan, accounting for 36.2% of GDP, an increase of 22 percentage points from 2005. Its growth rate is much higher than that of GDP, and it has become the main force driving the economy to shift gears. From an international perspective, it has become a major leader in the global digital economy industry, second only to the United States. The combined market value of digital platforms in China and the United States accounts for 90% of the total market value of the top 70 digital platforms in the world. Two of the world’s seven “super platforms” in the digital economy are companies, namely Alibaba and Tencent. The new industrial network chain structure formed under the digital background has promoted the deconstruction and reorganization of the existing industrial chain. Compared with the traditional industrial chain, it has the characteristics of being safer, more stable and more efficient, which provides a new idea and feasible path to optimize the industrial structure and achieve green development.

With the deterioration of human economic activities and production environment, soil pollution around the world has become increasingly serious, which has seriously affected the ecological structure and functional stability of soil. At present, many factories have left the urban area, and the old sites left behind are polluted and not suitable for planting plants or human life. And some oil refining and oil extraction factories have caused land pollution due to the leakage of crude oil. Due to the long-term industrialization, the “three wastes” (wastewater, waste gas, and waste residue) enter the soil through water bodies and the atmosphere. When accumulated to a certain extent, the ecological function of the soil will be degraded, which will have a certain impact on crops and groundwater, thereby reducing the yield and quality of food, thus posing a threat to human health. With people’s understanding of the importance of soil, soil heavy metal pollution has gradually become a hot spot in environmental science research. There are few studies on simulated soil pollution and remediation equipment in China, and less equipment used to study soil pollution diffusion and remediation laws. The research results of this paper enrich the research in this field. Based on the research on soil remediation technology and equipment at home and abroad, this paper fits the process of simulated soil remediation. It includes soil crushing, screening, simulated repair test, and test parameter monitoring on the soil to be tested. In this paper, the designed electrodynamic repair device is experimentally studied to demonstrate its feasibility. The device can be used for the remediation technology of soil heavy metal pollution, and provides a certain reference for the scientific research workers of soil pollution control.

In terms of theoretical research, experts and scholars at home and abroad have discussed the application and development prospects of the digital economy in various fields. This paper has done relevant research on various aspects and applications of the digital economy. Simon C proposes a representative measurement method to quantify the digital economy. The comparison is made by measuring the market capitalization of selected countries using a financial database, which measures and compares the digital economy between countries. The results show that the U.S. leads in every way, with the 11 largest companies by market capitalization all coming from the U.S. Germany should take policy measures to increase its competitiveness in this field. This approach can be applied to different countries seeking to benchmark their economic performance and formulate policy measures to keep their digital economy ahead of others (Simon et al., 2017). Drahokoupil J discusses the impact of the digital economy on the workforce. According to him, the digitization of the economy refers to how ICTs change the goods and services we produce, how they are produced, and where they are produced. This involves many aspects of society: how labor is exchanged on digital platforms and how consumers become producers (so-called prosumers), how mass production can be repurposed into local micro-production, how underutilized assets can be shared up close to zero marginal cost, how companies can re-examine their decisions about where to produce in light of the use of robots, and how new monopolies can emerge. The most important point is the impact of big data on the economic structure (Drahokoupil and Jepsen, 2017). Teoh C S examines national cybersecurity strategies for the digital economy. It aims to gain an in-depth understanding of the relationship between the development of national cybersecurity and the digital economy based on literature such as journal articles, global reports, current industry dynamics and market trends. He analyzed the cybersecurity of nine countries centered on the digital economy, and found that countries with a high degree of digital informatization rely less on national cybersecurity to strengthen confidence in the digital space. And the top ten countries in the existing digital economy have all implemented national cybersecurity strategies, providing the necessary foundation for the further vigorous development of the digital economy (Teoh and Mahmood, 2017). Alizadeh T discussed urban governance and company development in the digital economy from three different perspectives, combined with a specific case - the launch of Google Fiber in Kansas City. First, he scrutinized urban governance and the Fiber project. He highlighted the numerous regulatory concessions and incentives offered to Fiber during the construction phase. Second, he explores how pre-existing digital divides and socioeconomic inequalities affect Kansas City’s fibre plans. Finally, he discusses the significant policy implications of projects such as Fiber on urban governance, emphasizing the stark realities facing such businesses (Alizadeh et al., 2017). Markova O V studies corporate innovation activities in the context of the digital economy from both economic and legal perspectives. He pointed out that the innovation activities of enterprises also include the development of artificial intelligence and robotics, and the innovative behavior of enterprises also includes artificial intelligence and robotics. Under the existing artificial intelligence technology and application conditions, it is particularly important to ensure the security of the country in the context of digitalization. In this context, the strategic goal of ensuring information security is to protect the vital interests of individuals and society from internal and external threats related to the application of information technology for various purposes in violation of civil law. Therefore, innovation will increase the investment attractiveness of enterprises, and enterprises should maintain a balance between creative freedom and internal control measures. It self-regulates in the field of digital technology and establishes a unified legal framework in the economic field (Markova et al., 2021). Leahovcenco A discusses issues related to the definition of cybersecurity and its elements in order to address current cyber threats and reduce the use of malware and complex infrastructure. And he queried a lot of data about cyber attacks. He used correlation analysis to analyze the closeness of the relationship between the proportion of the digital economy in GDP and the GCI index, and proposed an improvement method (Leahovcenco, 2021). Miao Z breaks the traditional research on digital economy and value chain. He proposed the concept of digital economy value chain, and discussed its connotation, value activity composition, and characteristics of value chain. The value chain of the digital economy is driven by digital elements (data, digital technology and digital models), and is a combination of the digital economy and value chain. It is based on digital elements, and its essence is a chain based on the value creation of the digital economy. In the value chain of the digital economy, each value-added link can generate value, and the flow of the value chain is the process of value generation and transmission (Miao, 2021).

Figure 5 shows an electric repair device. The equipment includes a soil chamber, an anode chamber, a cathode chamber and a DC power supply. The soil chamber and the electrode chamber were separated by a porous plexiglass plate and filter paper to prevent soil particles from entering the electrode chamber. The volume of the cathode and anode electrode chamber is L×H×W = 15 cm × 10 cm×5cm, and the graphite electrode plate is placed in the cathode and anode electrode chamber. The size of the electrode plate for experiment is L×H×W = 1 cm × 13 cm × 10 cm. The size of the soil chamber is L×H×W = 25 cm × 10 cm × 10cm, and the size of the graphite plate as the electrode plate is L×H×W = 2 cm × 10 cm × 16 cm. Graphite electrode plate has good properties such as good conductivity, high temperature resistance, acid resistance, alkali corrosion resistance and easy processing, so graphite electrode plate is selected for the experiment. The sampling holes are distributed equidistantly in the soil chamber to facilitate sampling. The gas generated during electrolysis is discharged the electrode chamber. Before the experiment, the equipment must be sealed to ensure that the equipment does not leak during the experiment. A uniform soil sample was placed in the soil chamber and compacted uniformly without leaving pores to avoid preferential passage. There are two drainage holes on the sides of the cathode and anode electrode chambers respectively, and a peristaltic pump is used to connect the solution reservoir to circulate the electrolyte (Anbazhagan et al., 2021).

The process flow of simulated contaminated soil remediation is shown in Figure 6.

Clarify the specific object: Clarify the specific soil to be repaired, and determine the soil depth at the same time. Soil at different depths is polluted differently.

Soil borrowing: Take the soil of the land to be tested, and determine the basic properties of the soil, such as water content, PH value, density, organic matter content, etc.

Soil crushing and screening: removal, crushing and screening of non-soil components. Non-soil substances and lumpy soils have a great impact on the test results in a limited test space.

Simulated remediation test: Pour the soil into the soil chamber, carry out the remediation test of the contaminated soil, and record and organize the test results.

Contaminated soil removal: During the simulated soil contamination process, the contaminated soil was removed and the test equipment was cleaned.

Remediation soil treatment and backfilling: After removing the remediation soil, check the remediation soil to ensure that the treated soil will not cause secondary pollution to the surrounding environment again.

The original soil of the experiment was taken from 15 cm below the surface of the former site of the Jiangxi ammonia plant, and the collected soil was naturally air-dried and ground to pass through a 20-mesh sieve and stored for later use. The basic properties of soil are shown in Table 3.

A filter paper (or filter paper + fiber membrane) was placed between the electrode chamber and the soil chamber to isolate the soil and electrolyte, and 100 g of lead-contaminated simulated soil samples were filled in the soil chamber of the electrodynamic remediation device. Add 200 ml of working solution (distilled water or 0.1 mol/L KCl solution) to the two electrode chambers respectively, and after equilibrating for 12 h, supplement the working solution to the height of the overflow pipe, connect the electrodes to the DC power supply, apply a constant voltage, and start the repair experiment. KCl has good conductivity, is easy to ionize, and is cheap and easy to obtain, so it is selected as the electrolyte. The specific experimental conditions are shown in Table 4.

During the experiment, the ammeter was used to record the current curve in real time, and the pH value of the electrolyte was measured at the specified time interval. After the test, the electrolysis working liquid was collected, and the soil was taken out and divided into five parts. It is marked as A, B, C, D, E, representing soils between 0 and 2 cm, 2–4 cm, 4–6 cm, 6–8 cm and 8–10 cm from the anode, respectively. The changes of soil pH, current and the concentration of heavy metal cadmium were measured, and the adsorption rate was calculated.

(1) Changes in soil pH.

Figure 7 studies the effect of electrolyte type and remediation time on soil pH. Among them, the electrolyte of E1 is distilled water, the electrolyte of E2 is 0.1 mol/L KCl solution, the experimental voltage is 10V, and the soil remediation time is 24 h. As can be seen from Figure 7, no matter whether the electrolyte is distilled water or KCl solution, there is no significant difference in the characteristics of soil pH change, all showing that the pH of the soil near the anode is lower, and the pH of the soil near the cathode is higher. In E2, the region A near the anode had a pH of 3.18, while the region E near the cathode had a pH of 10.05. And with the extension of remediation time, the soil pH in the anode area gradually decreased, and the pH values of area A in E2 and E3 were 3.18 and 3.09, respectively. The soil pH in the cathode area gradually increased, and the pH values of area E in E2 and E3 were 10.05 and 10.13, respectively. It is shown that the type of electrolyte has no obvious effect on the change of soil pH when the electrodynamic remediation device remediates the contaminated soil, and all causes the soil pH to surge. And with the extension of remediation time, soil pH mutation tends to be further deteriorated.

The existing forms of heavy metals in soil are divided into ion exchange state, carbonate bound state, Fe-Mn oxidation state, reducible state and residual state, and their solubility decreases in turn. The research of Kaur T (Kaur et al., 2021) et al. showed that under the action of electric field and electrolyzed water, >90% ion exchange state, 45–75% carbonate bound state, 15–30% Fe-Mn oxidation state and 8–30% Fe-Mn oxidation state can be removed. 20% reducible heavy metal pollutants. Therefore, when using electrodynamics to remediate heavy metal-contaminated soils, soil pH should be considered, because it affects the existence of heavy metals and the desorption process from the soil surface.

(2) Changes in current.

It can be seen from Figure 8 that in the electrodynamic repair process, although the electrolyte type and the experimental voltage are different, the current change trend is generally the same. The current increases rapidly in a short time, and then gradually decreases and becomes stable after reaching the maximum value. When the electrolyte is KCL solution, the soil current is significantly higher than that of distilled water. Adding electrolyte to water will increase the conductivity of water, KCl is a strong electrolyte, there is the transfer of k+ and cl-charges, so the current is larger (Njoh et al., 2021). With the increase of voltage, the electromigration is enhanced. The greater the migration of heavy metal Cd to the cathode, the greater the current. At 6h, the currents of E1 and E2 both reached their peak values, which were 0.44 and 0.68mA, respectively, after which the current began to decrease. When the voltage is 20V, the maximum current reaches 0.75 mA respectively. After reaching the peak value, it gradually decreased, and dropped to 0.68, 0.55, 0.48 and 0.34 mA at different times.

(3) Changes in heavy metal concentrations.

Figure 9 shows the effect of electrolyte type and restoration time on the concentration of cadmium in soil. Among them, the electrolyte of E1 is distilled water, the electrolyte of E2 is 0.1 mol/L KCl solution, the voltages of E1 and E2 are both 10V, and the voltage of E4 is 20V. It can be seen from Figure 9 that the distribution of cadmium ions in the soil is not uniform. In the acidic area, the lead content is significantly reduced, and in the alkaline area, the lead content is relatively high, and there is a clear focusing phenomenon. This is because Cd2+ is more easily reduced under acidic conditions. With the prolongation of remediation time, the distribution of cadmium ions in the soil became more uneven. In E4, the lead concentrations in regions A, B, C, D and E were 0.22 mg/g, 0.64 mg/g, 0.79 mg/g, 1.41 mg/g and 1.22 mg/g.

(4) Heavy metal adsorption rate.

Figure 10 shows the variation of the adsorption rate of cadmium ions in soil with time under each experimental condition. The adsorption rate of cadmium ions changes the same under different electrolytes and voltage gradients. With the prolongation of remediation time, the adsorption rate of cadmium ions in soil also increased gradually. When the voltage increased from 10V to 20V, the adsorption rates of cadmium ions in soil at 6, 12, 24, 48 and 96 h were 2.6, 4.5, 6.2, 10.7 and 12.5%, respectively, and the average adsorption rate was 7.3%. It can be seen from the figure that the change trend of cadmium ion adsorption rate under different electrolytes is the same, and the adsorption rate gradually increases from 6 to 96h, but the upward trend is not obvious. With the increase of voltage, the adsorption rate of heavy metal cadmium ions gradually increased, and when the voltage was from 10V to 20V, the adsorption rate of cadmium ions increased significantly.

(5) Energy consumption.

Table 5 shows the power consumption (W/mg) of removing 1 mg of cadmium, and Figure 11 shows the change of power consumption with time under each experimental condition. The changes in energy consumption are roughly the same for different electrolytes and voltage gradients. As the repair time increases, the energy consumption also increases gradually. When the electrolyte is KCl, the energy consumption of soil at 6, 12, 24, 48 and 96 h is 0.3, 0.96, 1.42, 1.6 and 1.65W respectively, which is higher than that when the electrolyte is distilled water. When the voltage increased from 10V to 20V, the energy consumption of soil at each time point was 0.58, 1.24, 1.85, 2.27 and 2.38W respectively. It can be seen from the figure that the impact of voltage on energy consumption is greater than that of electrolyte on energy consumption, which shows that in the process of electrodynamic repair, the expected repair effect can be achieved by increasing the voltage (Arulnangai et al., 2021; Sangur et al., 2021).

In this paper, a remediation device for electrokinetic remediation of heavy metal geophysical soil is designed, and the relevant experimental parameters such as soil pH, current, heavy metal concentration and adsorption rate are measured. Based on the digital economy, this paper recycles the electrolyte to promote the application of the circular economy in environmental protection. The device fully reacts the electrolyte with soil heavy metal ions, and also has the advantage of resource reuse, has a good removal effect on soil heavy metal pollution, and is conducive to improving soil remediation efficiency. Through the above experiments, it is recommended to carry out the follow-up work from the following. In this experiment, the electrokinetic remediation of cadmium-contaminated soil samples was only studied, and other heavy metals and organic matter were not considered. Subsequent experiments may consider using other heavy metal-contaminated soils for research.