Heavy metals in soil, due to their high density and strong toxicity, are considered among the most dangerous environmental pollutants. Because conventional physical and chemical remediation methods are often expensive, there is growing interest in alternative, low-cost approaches for improving contaminated soils. Among these methods, phytoremediation, electrophytoremediation, and electrokinetic techniques have been widely applied for heavy metal removal. In this experimental study, soils contaminated with lead (Pb), cadmium (Cd), chromium (Cr), copper (Cu), and boron (B) were investigated under controlled conditions using 12 pots, including four control groups representing phytoremediation, electrophytoremediation, electrokinetic treatment, and reference samples. Mung bean, sunflower, and rapeseed were grown in the contaminated soils and exposed to a direct current (DC) voltage of 30 volts for 4 hours per cycle over a 30-day period. The results showed that graphite electrodes enhanced the efficiency of heavy metal removal, while electrical stimulation in the phytoremediation system increased the average soil pH. In the electrophytoremediation treatment, sunflower achieved the highest uptake of Cr, Cu, and B, whereas rapeseed accumulated the highest levels of Cd and Pb. In the phytoremediation treatment, mung bean showed the greatest uptake of Cr, Cu, and B, while sunflower recorded higher accumulation of Cd and B. Overall, the findings indicate that electric current has a stronger influence on metal uptake in sunflower compared to the other plants. The concentrations of heavy metals absorbed by plants per unit of dry biomass were measured using ICP analysis. The study concludes that electrophytoremediation is an efficient and promising approach for the remediation of soils contaminated with heavy metals.
EXTENDED ABSTRACT
Introduction
Soil contamination with heavy metals is recognized as one of the major environmental challenges worldwide. The accumulation of heavy metals in soil through industrial activities, agricultural practices, solid waste disposal, and the excessive use of chemical fertilizers can significantly reduce soil quality and threaten the health of humans and other living organisms. Heavy metals such as lead (Pb), cadmium (Cd), chromium (Cr), copper (Cu), and boron (B) are considered among the most hazardous soil pollutants due to their high toxicity, persistence, and potential for bioaccumulation within the food chain. Phytoremediation is a plant-based approach used to absorb, stabilize, or remove contaminants from soil. Because of its low cost, environmental friendliness, and suitability for large-scale applications, it has been widely recognized as an effective method for the remediation of contaminated soils. Nevertheless, the efficiency of phytoremediation may be limited under certain conditions and is influenced by factors such as plant species, contaminant concentration, and soil properties. In this context, the application of electric fields through electro-phytoremediation can enhance the mobility and uptake of contaminants, thereby improving the ability of plants to remove heavy metals from polluted soils. In the present study, the effectiveness of phytoremediation, electro-phytoremediation, and electrokinetic techniques in removing Pb, Cd, Cr, Cu, and B from contaminated soils was investigated. In addition, the uptake capacity of mung bean, sunflower, and canola plants for these elements was evaluated.

Materials and Methods
This study was carried out under greenhouse conditions using a pot experiment. A total of 12 pots, each containing 3 kg of soil, were prepared, and the soils were artificially contaminated with lead, cadmium, chromium, copper, and boron. The contaminants were introduced into the soil using Pb(NO₃)₂, CdCl₂, K₂Cr₂O₇, CuSO₄, and H₃BO₃ after the required amounts had been accurately calculated. Twelve seeds of sunflower, mung bean, and canola were sown in each pot. In addition, several uncontaminated pots were used as control treatments.
For the electro-phytoremediation experiment, graphite electrodes measuring 13 cm in length and 4 cm in width were employed. A direct current (DC) with a voltage of 30 V and a current intensity of 2–3 A was applied for 4 hours at predetermined intervals. The electric field treatment began on the tenth day after seed germination to allow sufficient time for the initial establishment of the plants. The investigated parameters included germination rate, plant growth, biomass production, and the efficiency of heavy metal removal. At the end of the growth period, soil samples and plant tissues, including roots, stems, leaves, and flowers, were harvested. The samples were thoroughly washed, dried, and prepared for analysis, and the elemental concentrations were determined using inductively coupled plasma (ICP) analysis. In the electrokinetic section of the experiment, soil samples were collected from the anode zone, cathode zone, and the central region of the pots at different time intervals, and the concentrations of the elements were subsequently measured.

Results and Discussion
The results indicated that the addition of heavy metals did not significantly affect seed germination; however, it led to a noticeable reduction in vegetative growth. At elevated boron concentrations, plants showed growth inhibition and eventual wilting, which necessitated adjustment of the boron levels. The findings from the electro-phytoremediation experiments revealed that the application of an electric current enhanced the uptake efficiency of heavy metals by the plants. In addition, the use of graphite electrodes significantly improved the overall removal efficiency of the target elements.
A comparison between phytoremediation and electro-phytoremediation showed that applying an electric current enhanced the transport and uptake of elements in plants. In most cases, element accumulation under electro-phytoremediation was higher than that observed under conventional phytoremediation. The electrokinetic results also revealed a progressive decrease in heavy metal concentrations across different soil zones over time. In the anode region, the concentrations of Cr, Cd, Pb, Cu, and B showed a clear downward trend, while a reduction in elemental levels was also observed in the cathode region. Furthermore, measurements of pH and electrical conductivity (EC) indicated that the electric field altered soil chemical conditions and facilitated ion mobility. The results further demonstrated that plant species and the specific characteristics of each element significantly influence the patterns of uptake and accumulation of heavy metals. Overall, sunflower exhibited the highest efficiency in accumulating Cr, Cu, and B, whereas canola showed greater effectiveness in the uptake of Cd and Pb. In addition, the application of an electric field increased elemental mobility in the soil and improved the overall efficiency of plant uptake.

Conclusion
The results of this study indicate that the simultaneous use of appropriate plant species and an applied electric field can serve as an effective, cost-efficient, and environmentally friendly strategy for the remediation of soils contaminated with heavy metals.