Search Results (59)

This paper aims to review the sources, occurrence patterns, and potential risks of antibiotic resistance genes (ARGs) in agricultural soils and discuss strategies for their reduction. The pervasive utilization of antibiotics has led to the accumulation of ARGs in the soil. ARGs can be transferred among microorganisms via horizontal gene transfer, thereby increasing the likelihood of resistance dissemination and heightening the threat to public health. In this study, we propose that physical, chemical, and bioremediation approaches, namely electrokinetic remediation, advanced oxidation, and biochar application, can effectively decrease the abundance of ARGs in the soil. This study also highlights the significance of various control measures, such as establishing a strict regulatory mechanism for veterinary drugs, setting standards for the control of ARGs in organic fertilizers, and conducting technical guidance and on-farm soil monitoring to reduce the environmental spread of ARGs and protect public health. Full article

In arid and semi-arid zones, reclaiming/restoring salt-affected soil is considered a significant challenge because of the limited amount of water available for soil washing. The reclaimed salt-affected soil is regarded as a valuable resource for increasing the production of food and feed. In the current study, soil electrokinetics (SEK) under pulsed-mode electric field operation was used to evaluate and optimize energy use efficiency for reclaiming salt-affected soils, which is one of the electro-agric technology branches that was suggested in 2021 to address the water crisis in arid and semi-arid regions. Under a fixed applied voltage of 5 V, or 1 V/cm, the calcareous, highly salinized soil under investigation was reclaimed. A 25% reduction in applied voltages with time OFF set at 15, 30, 60, and 120 min and a 50% reduction with time OFF set at 15, 30, 60, and 120 min were the two pulsed electric field techniques that were examined. The findings demonstrated that the removal of Na⁺ surpasses half (50%) in the majority of pulsed-mode studies. By decreasing the removed K⁺, which is crucial for plant growth, the pulsed modes of electric fields 25 and 50% showed an economic advantage over the control experiment, which operated with a continuous electric field. Throughout the control experiment, very little Ca²⁺ was removed. However, the amount of Ca²⁺ removed rose when the electric field’s pulsed mode was applied, and the removal percentages were higher for the pulsed 50% strategy than the pulsed 25% strategy. In nearly every segment of every experiment (control, pulsed 25%, and pulsed 50%), the pH levels exceeded the initial value of 8.05. The pulsed 25% strategy of the OFF time showed an improvement in current passing at the longest interval of 120 min; the pulsed 50% strategy of the OFF time showed an improvement in current passing at the shorter and longer intervals of 15, 60, and 120 min; however, the interval of 30 min had a negative effect. The cumulative EO flow at the time OFF interval of 60 min was improved by the pulsed 25% strategy throughout the first seven days of operation, and by the end of the trial, the control experiment exhibited high values. The highest values, however, were displayed by the pulsed 50% field at the time OFF interval of 60 min. The anolyte pH decreased for the majority of the time OFF intervals over the first seven days of the trial for both the 25% and 50% pulsed strategies. Lastly, in order to minimize the overall energy consumption, it is strongly advised that the pulsed mode of the electric field be used while reclaiming salt-affected soil. Full article

Polycyclic aromatic hydrocarbons (PAHs) are considered hazardous pollutants due to their negative impact on the environment and human health. PAHs can accumulate and be retained in the soil, so PAH pollution is a worldwide problem. This review paper highlights the sources of PAH soil pollution, factors affecting the bioavailability of PAHs in soil, and soil bioremediation methods, as well as the advantages and limitations of the application of these methods. Aspects regarding the impact of the application of surfactants are presented in order to obtain good bioavailability during PAH bioremediation. Bioremediation techniques of soil polluted by these hydrocarbons are addressed: phytoremediation, rhizoremediation, composting, vermiremediation, micoremediation, and electrokinetic bioremediation of PAH-polluted soils. A comprehensive overview of bioremediation technologies for PAH-polluted soils is needed so that the right soil remediation technology is chosen. It has been observed the bioremediation of contaminated soils through rhizoremediation proved to be an effective process, the future of organic pollutants in interaction with plants and microbes must be researched. Vermiremediation, electrokinetic bioremediation, and microcomposting are effective processes for treating soils in situ. Phytoremediation is a sustainable and ecological method of PAH depollution. It improves soil fertility by releasing different organic matter in the soil, and it can be applied on a large scale. Full article

This work compares two technologies for the remediation of metal-polluted mine tailings based on lab-scale bioleaching experiments performed in (a) conventional agitated slurry-phase reactors and (b) in situ electrokinetic percolation. While ex situ bioleaching in agitated reactors has been widely studied, only a few previous works have studied the in situ option that couples bioleaching and electrokinetics. Real mine tailings from an abandoned sphalerite mine in southern Spain were used. The leaching medium was externally generated in a bioreactor using an autochthonous acidophilic culture and then added to tailings in batch experiments. This medium enabled metal leaching from mine tailings without the stringent operating conditions required by a classic bioleaching process. Metal removal efficiencies and kinetic rate constants after 15 d of treatments were calculated. Additionally, advantages or disadvantages between the two methods were discussed. The results for the innovative EK-percolation method showed rates and efficiencies that were comparable to, and in some cases better than, those achieved with conventional stirred slurry systems. Full article

This study investigates the influence of four soil improvement methods—microbially induced carbonate precipitation (MICP), electrokinetics (EK), chemical additives, and a combination of EK and chemical additives—on the dispersivity, mechanical properties, and microstructure of dispersive soil. A series of tests was designed to evaluate the effectiveness of these methods on dispersive soil. Both the original and treated soil samples were tested to assess changes in soil properties, including dispersivity, plasticity, pH, unconfined compressive strength (UCS), shear strength, and microstructure. Dispersivity was assessed using pinhole tests, crumb tests, double hydrometer tests, and exchangeable sodium percentage tests. The experimental results indicate that the combined EK and chemical additives method significantly reduces the dispersivity and plasticity of the dispersive soil compared with the other methods, leading to improved UCS. The EK and chemical additive methods individually demonstrate effective modification under a voltage of 48V and an additive content of 4%, respectively, enhancing the shear strength of the dispersive soil. MICP does not significantly improve the dispersivity of dispersive soil, but it does enhance the shear strength of the treated soil, with a particularly notable increase in the internal friction angle. Overall, the combined method shows more remarkable improvements in the dispersive soil than any single method. In summary, the combination of EK and chemical additives has significant potential for improving the dispersivity and mechanical properties of dispersive soil. Full article

Phosphorus (P) is a key component that limits plant growth. P is a limited resource; hence, effective P management is needed to increase plant P consumption from the soil and reduce P input levels through fertilization. In light of these difficulties, the goal of this review is to investigate the role of soil electrokinetics (SEKs)—a physicochemical approach—as the main approach in our in-depth analysis of publication history across six P-management research search engines to ensure sustainable management. This review covers the management of P using the SEKs from a number of perspectives, such as P injection in soil to improve bioremediation efficiency; P specific and synergistic separation from other related elements; increasing plant P availability and reusing it as fertilizer; and P removal from soil and sewage sludge. In terms of P adsorption, after seven days on kaolin, no organic P adsorption was observed, while inorganic P adsorbed to a maximum of 73% after six days. This implies that in low-permeability soils, the organic P source can be a practical source of P during in situ bioremediation. With the use of chemical additives, the specific and synergistic separation of P from/with other elements was made possible. When compared to the region near the cathode, P availability for the plant was higher in the vicinity of the anode electrode. P can be recycled and used as fertilizer. The iron electrodes result in a noticeably greater removal of phosphate than titanium electrodes. Further research is required to offer a technical solution for the proper handling of P, as there has been little research on P management from many perspectives. Full article

Soft clay contamination is an increasingly global issue with significant implications for land development and human health. Electrokinetic remediation (EKR) has demonstrated significant potential for cleaning contaminated soils. It is crucial to develop efficient processes that minimize environmental impact and reduce costs. A series of citric acid (CA)-enhanced EKR tests were conducted using a novel experimental setup, with the electrolyte positioned above the soil surface, to examine the impact of four different electrode arrangements on the effectiveness of EKR. The position of the electrode end had a significant impact on the migration of ions in the anolyte and catholyte, which in turn affected the volume reduction in the anolyte, the magnitude of the current, and the migration of heavy metals. The electrode arrangement mode c (electrodes suspended in the electrolytes) can enhance the migration of the anolyte and reduce the drainage of the soil, making it an effective measure for improving the removal rate of heavy metals. After the heavy metal remediation is complete, the bearing capacity of the soil should be increased. Changing the electrode arrangement to mode d (anode suspended in the anolyte, a very small part of the cathode inserted into the soil) is an effective measure for reducing the soil water content and improving soil strength. Full article

Soil restoration by exploiting the principles and basics of electrokinetic (EK) has been extended to involve several categories, such as electrokinetic remediation in soil (SEKR), soil consolidation, the prevention of soil pollution, reclaiming salt-affected soil, the dewatering/dryness of wet soils, water reuse, seed germination, sedimentation, etc. As an extension of our recently published review articles on the soil electrokinetic (SEK) process intensification/optimization, the present review illustrates the effect of a reverse-polarity mode (RPM) on the efficiency of the SEK. Based on several searches of six database search engines, we did not find any relevant reviews focused on SEK improvements using the RPM. The influences of the RPM are described by various features, including (a) pollutant removal (organic, inorganic, and mixed pollutants) and (b) integration with other processes (phyto/bioremediation and Fenton oxidation), geosynthetics (consolidation, stabilization, and sedimentation), SEK operation conditions, and soil properties. Most of the RPM studies have focused on the remediation of organic pollutants. Several benefits can be gained from applying the RPM, such as (a) controlling the soil’s temperature, pH, and moisture values at desirable levels, (b) reducing a large number of chemical additives, (c) high remediation efficiency, (d) maintaining the indigenous fungal community’s appropriate diversity and abundance, (e) a stable and higher electric current, (f) enhancing microbial growth, etc. However, the hindrances to applying the RPM are (a) reducing the electroosmosis flow, (b) relatively high energy consumption, (c) reducing the diversity of soil microbes with a prolonged experiment period, (d) providing oxygen for a microbial community that may not be desirable for anaerobic bacteria, etc. Finally, the RPM is considered an important process for improving the performance of the SEK, according to experimental endeavors. Full article

Electrokinetic remediation (EKR) has shown great potential for the remediation of in situ contaminated soils. For heavy metal-contaminated soft clay with high moisture content and low permeability, an electrokinetic remediation method with electrolytes placed above the ground surface is used to avoid issues such as electrolyte leakage and secondary contamination that may arise from directly injecting electrolytes into the soil. In this context, using this novel experimental device, a set of citric acid (CA)-enhanced EKR tests were conducted to investigate the optimal design parameters for Cu- and Zn-contaminated soft clay. The average removal rates of heavy metals Cu and Zn in these tests were in the range of 27.9–85.5% and 63.9–83.5%, respectively. The results indicate that the Zn removal was efficient. This was determined by the migration intensity of the electro-osmotic flow, particularly the volume reduction of the anolyte. The main factors affecting the Cu removal efficiency in sequence were the effective electric potential of the contaminated soft clay and the electrolyte concentration. Designing experimental parameters based on these parameters will help remove Cu and Zn. Moreover, the shear strength of the contaminated soil was improved; however, the degree of improvement was limited. Low-concentration CA can effectively control the contact resistance between the anode and soil, the contact resistance between the cathode and soil, and the soil resistance by increasing the amount of electrolyte and the contact area between the electrolyte and soil. Full article

In recent years, with the escalation of food waste generation, stringent legal constraints on landfill usage and incineration have necessitated the exploration of alternative disposal methods, augmenting interest in diverse recycling strategies. Notably, carbonized food waste (CFW), a byproduct of food waste carbonization, has emerged as an efficacious adsorbent for pollutant removal. This study focuses on the application of in situ remediation techniques, specifically electrokinetic (EK) remediation combined with enhancers, to decontaminate soil afflicted with single or multiple heavy metals. The utilization of a permeable reactive barrier (PRB) infused with CFW aims to mitigate secondary environmental repercussions, including the propagation of contaminants in soil and groundwater. Experiments were conducted on clay samples contaminated with copper, lead, or a combination thereof. Observations revealed that the current density peaked during the initial 1–2 days of the experiment, experienced a resurgence post-electrode exchange, and subsequently diminished. The efficacy of metal removal was predominantly pronounced for copper, with remediation rates ranging from 85% to 92% in singly contaminated samples and 75% to 89% in dually contaminated samples after a 10-day treatment period, incorporating an electrode exchange on the eighth day. Conversely, the efficacy of lead removal was markedly lower, with rates of 0.6% to 33% in singly contaminated samples and 14% to 25% in combined contamination scenarios, suggesting the necessity for extended treatment durations. The post-experimental moisture content indicated successful enhancer injection. Additionally, pH measurements affirmed that heavy metals migrated effectively within the sample matrix, facilitated by the EK phenomenon after the electrode exchange. This study highlights the potential of CFW within PRBs for the remediation of heavy metal-contaminated soils, although the removal efficiencies between different metals is variable, emphasizing the need for tailored approaches in the treatment of lead-contaminated environments. Full article

Daily industrial activities pose a significant risk of environmental contamination through the release of toxic chemicals, including heavy metals, radionuclides and organic pollutants. Coastal marine areas, estuaries and harbors serve as primary hotspots for such pollution, with marine sediments acting as the ultimate sink for industrial and urban discharges, posing a serious environmental problem. Addressing this pressing issue requires the adoption of environmentally friendly technologies for the remediation and recovery of contaminated marine sediments. This paper provides a comprehensive review of different approaches for the remediation of contaminated sediments, focusing on the principle of electrokinetic remediation, with special emphasis on the use of microorganisms. A bibliometric analysis of key articles in the field is presented to elucidate the most important findings, particularly in the marine environment. The current state-of-the-art is reported for soil and sediment remediation approaches, with the first large-scale experiments and a preliminary cost estimate reported. However, the limited information available on the applicability of these techniques in the marine environment is highlighted. The limitations and risks associated with an inadequate implementation of this technique are discussed while acknowledging the advantages it offers for in situ remediation in marine environments. Full article

Rare earth elements (REEs) are essential raw materials for modern industries but mining them has caused severe environmental issues, particularly the recovery of heavy REEs (HREEs) from ion-adsorption deposits (IADs). Very recently, an emerging technology, electrokinetic mining (EKM), has been proposed for the green and efficient recovery of REEs from IADs. However, the conduction mechanism of the weathering crust soil, which is also a prerequisite for EKM, remains unclear, making the EKM process unpredictable. Here, we systematically investigated the conductivity of weathering crust soil in the presence of light REEs (LREEs, i.e., La³⁺ and Sm³⁺) and HREEs (Er³⁺ and Y³⁺), respectively. Results suggested that the voltage was dynamically and spatially redistributed by the movement of REEs and water during EKM, and the conventional assumption of the linear distribution of voltage leads to an inaccurate description of soil voltage. We proposed an improved Archie’s equation by coupling the mechanisms of liquid phase and solid-liquid interface conduction, which can predict soil conductivity more precisely. Moreover, the extended Archie’s equation is able to recalculate the voltage distribution at distinct times and spaces well during EKM. More importantly, the water content in field-scale weathered-crust soils can be retrieved by the newly proposed Archie’s equation, which helps optimize the leaching wells and improve the recovery rate of REE. This study focuses on the conduction mechanism of weathering crust soil, which provides a theoretical basis for better use of the EKM technology and promotes mining efficiency fundamentally. Full article

Electrokinetic remediation is a cost-effective and efficient method that utilizes electrical current to transport ions within the subsurface. This process aims to remediate soil contamination caused by industrial activities, which poses threats to wildlife, water quality, and air quality. To assess the impact of the electrokinetic process on tank leaching efficiency, two electrode configurations were tested: vertical and horizontal arrays. These tests considered variable electrode spacing and different voltages in the soil residue. Additionally, the movement of copper cations from the anode to the cathode under this process was investigated. Results show that the horizontal electrode array is more effective in transporting soil moisture because of its broader contact with the soil. After 20 days of using the electrokinetic method with vertical electrodes, the soil moisture content decreased by 12.28%; with horizontal electrodes, it dropped by 38.4%. Also, the concentration of copper in the soil near the cathode electrode increased from 0.54 to 0.77% after 20 days. The estimated copper ion content in the cathode area after 20 days was between 150 and 350 mol/m³, aligning closely with the measured value of 192.5 mol/m³. These results indicate that the electrokinetic process can significantly enhance copper recovery efficiency in tank leaching processes and curtail environmental side effects. Overall, this study provides valuable insights into the benefits of using the electrokinetic process to remediate leaching residue and improve the efficiency of industrial processes. Full article

The zeta potential of soils is an electric potential in the double-layer interface and is a physical property exhibited by any particle related to electrochemical attractive forces. On the other hand, the chemical aging phenomenon is seen as the chief mechanism of the aging of sands due to the dissolution and precipitation of minerals, resulting in the development of the cementation of particles in granular mediums. The present investigation focuses on determining whether granular materials can generate cementation due to electrokinetic forces, and if the zeta potential could be related as a measure of the potential of chemical aging. X-ray fluorescence and diffraction tests were performed to characterize four representative fractions of one kind of sand, and zeta potential studies were carried out to determine the electrical potential on the mineral surfaces of each one. Zeta potential analysis showed both dependence on the mineralogical content and the variation in the pH of the colloidal solution fluid because the increase in OH- ion concentrations increases the thickness of the diffuse double layer and the electrokinetic forces of attraction. Moreover, the zeta potential showed an increase in the thickness of the diffuse double layer, due to the electrokinetic forces, which can be associated with the development of cohesive forces with a dependence on the mineralogy of sands. Full article

Recently, electro-kinetic (EK) remediation has become more popular as a novel method for removing chromium contamination from soil. This approach, however, is ineffective since it uses both cationic and anionic forms of chromium. In this study, a membrane-based technique was employed to increase the efficiency of the electro-kinetic removal of chromium. Chromium removal from polluted sludge was studied using four bench-scale experiments. Two of these experiments employed distilled water (EK$-$1 and EK$-$2 and membrane), whereas the other used acetic acid as the catholyte (EK$-$3 and EK$-$4 and membrane). The pH, total chromium, and fractionation of chromium in the sludge were measured after remediation. In the EK$-$1, EK$-$2 and membrane, and EK$-$3 and EK$-$4 and membrane trials, the average removal efficiencies of total chromium were 47.6%, 58.6%, and 74.4%, 79.6%, respectively. In contrast to the electro-kinetic remediation strategy, which left approximately 80% of the sludge neutral or alkaline after treatment, the membrane created acidic soil conditions throughout the sludge. For example, the high field intensity used in the membrane tests may have helped to facilitate chromium desorption, dissolution, and separation from the sludge and enhanced chromium mobility. The findings show that the membrane can improve the effectiveness of chromium removal from sludge when utilized in the EK remediation process. Full article