Electric and magnetic fields characterized by high efficiency, low consumption and environment-friendly performance have recently generated interest as a possible measure to enhance the performance of the biological treatment process used to remove refractory organics. Few studies have been carried out to-date regarding the simultaneous application of electric and magnetic fields on biofilm process to degrade diclofenac. In this study, 3DEM-BAF was designed to evaluate the electrio-magnetic superposition effect on diclofenac removal performance, kinetics, community structure and synergistic mechanism. The results show that 3DEM-BAF could significantly increase the average removal rate of diclofenac by 65.30 %, 57.46 %, 9.48 % as compared with that of BAF, 3DM-BAF, 3DE-BAF, respectively. The diclofenac degradation kinetic constants and dehydrogenase activity of 3DEM-BAF were almost 6.72 and 2.53 times higher than those of BAF. Microorganisms of 3DEM-BAF in the Methylophilus and Methyloversatilis genera were distinctively enriched, which was attributed to the screening function of electric field and propagation effect of magnetic field. Moreover, three processes were found to contribute to diclofenac degradation, namely electro-magnetic-adsorption, electro-chemical oxidation and electro-magnetic-biodegradation. Thus, the simultaneous application of electric and magnetic fields on biofilm process was demonstrated to be a promising technique as well as a viable alternative in diclofenac degradation enhancement.

Applying an electric field to stimulate the microbial reductive dechlorination of polychlorinated biphenyls (PCBs) represents a promising approach for bioremediation of PCB-contaminated sites. This study aimed to demonstrate the biocathodic film-facilitated reduction of PCB 61 in a sediment-based bioelectrochemical reactor (BER) and, more importantly, the characterizations of electrode-microbe interaction from microbial and electrochemical perspectives particularly in a time-dependent manner. The application of a cathodic potential (−0.45 V vs. SHE) significantly improved the rate and extent of PCB 61 dechlorination compared to the open-circuit scenario (without electrical stimulation), and the addition of an external surfactant further increased the dechlorination, with Tween 80 exerting more pronounced effects than rhamnolipid. The bacterial composition of the biofilms and the bioelectrochemical kinetics of the BERs were found to be time-dependent and to vary considerably with the incubation time and slightly with the coexistence of an external surfactant. Excellent correlations were observed between the dechlorination rate and the relative abundance of Dehalogenimonas, Dechloromonas, and Geobacter, the dechlorination rate and the cathodic current density recorded from the chronoamperometry tests, and the dechlorination rate and the charge transfer resistance derived from the electrochemical impedance tests, with respect to the 120 day-operation. After day 120, PCB 61 was resistant to further appreciable reduction, but substantial hydrogen production was detected, and the bacterial community and electrochemical parameters observed on day 180 were not distinctly different from those on day 120.

In this study, we firstly used alginate to enhance an electrokinetic technology to remediate soil contaminated with divalent heavy metals (Pb²⁺, Cu²⁺, Zn²⁺). The mechanisms of alginate-associated migration of metal ions in electric field were confirmed. Alginate resulted in a high electrical current during electrokinetic process, and soil conductivity also increased after remediation. Obvious changes in both electroosmotic flow and soil pH were observed. Moreover, these factors were affected by increasing alginate dosage. The highest Cu (95.82%) and Zn (97.33%) removal efficiencies were obtained by introducing 1 wt% alginate. Alginate can desorb Cu²⁺ and Zn²⁺ ions from soil by forming unstable gels, which could be dissociated through electrolysis. However, Pb²⁺ ions did not easily migrate out of the contaminated soil. The density functional theory (DFT) calculations show Pb²⁺ ions could form a more stable coordination sphere in metal complexes than Cu²⁺ and Zn²⁺ ions. The metal removal efficiency was decreased by increasing alginate dosage at a high level. More alginate could provide more carboxyl ligands for divalent metal ions to stabilize gels, which were difficult to dissociate by electrolysis. In summary, the results indicate it is potential for introducing alginate into an electrokinetic system to remediate Cu- and Zn- contaminated soil.

In this work, soil contaminated by petroleum resins was remediated by electrokinetic-bioremediation (EK-BIO) technology for 60 days. A microbial consortium, comprising Rhizobium sp., Arthrobacter globiformis, Clavibacter xyli, Curtobacterium flaccumfaciens, Bacillus subtilis, Pseudomonas aeruginosa and Bacillus sp., was used to enhance the treatment performance. The results indicate that resin removal and phytotoxicity reduction were highest in the inoculated EK process, wherein 23.6% resins was removed from the soil and wheat seed germination ratio was increased from 47% to around 90% after treatment. The microbial counts, soil basal respiration and dehydrogenase activity were positively related to resins degradation, and they could be enhanced by direct current electric field. After remediation, the C/H ratio of resins decreased from 8.03 to 6.47. Furthermore, the structure of resins was analyzed by Fourier-transform infrared spectroscopy, elemental analysis, and ¹H nuclear magnetic resonance (¹H NMR) before and after treatment. It was found that the changes of the structure of resins took place during EK-BIO treatment and finally led to the reduction of aromaticity, aromaticity condensation and phytotoxicity.

In this study, an electrokinetic technique for remediation of Pb²⁺, Zn²⁺ and Cu²⁺ contaminated soil was explored using sodium alginate (SA) and chitosan (CTS) as promising biodegradable complexing agents. The highest Cu²⁺ (95.69%) and Zn²⁺ (95.05%) removal rates were obtained at a 2 wt% SA dosage, which demonstrated that SA significantly improved the Cu²⁺ and Zn²⁺ removal efficiency during electrokinetic process. The abundant functional groups of SA allowed metal ions desorption from soil via ion-exchange, complexation, and electrolysis. Pb²⁺ ions were difficult to remove from soil by SA due to the higher gelation affinity with Pb²⁺ than Cu²⁺ and Zn²⁺, despite the Pb²⁺ exchangeable fraction partially transforming to the reducible and oxidizable fractions. CTS could complex metal ions and migrate into the catholyte under the electric field to form crosslinked CTS gelations. Consequently, this study proved the suitability of biodegradable complexing agents for treating soil contaminated with heavy metals using electrokinetic remediation.

One of the topics gaining lots of recent attention is the antimony (Sb) pollution. We have designed a dual-functional electroactive filter consisting of one-dimensional (1-D) titanate nanowires and carbon nanotubes for simultaneous oxidation and sorption of Sb(III). Applying an external limited DC voltage assist the in-situ conversion of highly toxic Sb(III) to less toxic Sb(V). The Sb(III) removal kinetics and efficiency were enhanced with flow rate and applied voltage (e.g., the Sb(III) removal efficiency increased from 87.5% at 0 V to 96.2% at 2 V). This enhancement in kinetics and efficiency are originated from the flow-through design, more exposed sorption sites, electrochemical reactivity, and limited pore size on the filter. The titanate-CNT hybrid filters perform effectively across a wide pH range of 3–11. Only negligible inhibition was observed in the presence of nitrate, chloride, and carbonate at varying concentrations. Our analyses using STEM, XPS, or AFS demonstrate that Sb were mainly adsorbed by Ti. DFT calculations suggest that the Sb(III) oxidation kinetics can be accelerated by the applied electric field. Exhausted titanate-CNT filters can be effectively regenerated by using NaOH solution. Moreover, the Sb(III)-spiked tap water generated ∼2400 bed volumes with a >90% removal efficiency. This study provides new insights for rational design of continuous-flow filters for the decontamination of Sb and other similar heavy metal ions.

The application of a low-voltage electric field as an electron donor or acceptor to promote the bioremediation of chlorinated organic compounds represents a promising technology meeting the demand of developing an efficient and cost-effective strategy for in situ treatment of PCB-contaminated sediments. Here, we reported that bioanode stimulation with an anodic potential markedly enhanced dechlorination of 2,3,4,5-tetrachlorobiphenyl (PCB 61) contained in the sediment at an electronic waste recycling site of Qingyuan, Guangdong, China. The 110-day incubation of the bioanode with a potential poised at 0.2 V relative to saturated calomel electrode enabled 58% transformation of the total PCB 61 at the initial concentration of 100 μmol kg⁻¹, while only 23% was reduced in the open-circuit reference experiment. The introduction of acetate to the bioelectrochemical reactor (BER) further improved PCB 61 transformation to 82%. Analysis of the bacterial composition showed significant community shifts in response to variations in treatment. At phylum level, the bioanode stimulation resulted in substantially increased abundance of Actinobacteria, Bacteroidetes, and Chloroflexi either capable of PCB dechlorination, or detected in the PCB-contaminated environment. At genus level, the BER contained two types of microorganisms: electrochemically active bacteria (EAB) represented by Geobacter, Ignavibacterium, and Dysgonomonas, and dechlorinating bacteria including Hydrogenophaga, Alcanivorax, Sedimentibacter, Dehalogenimonas, Comamonas and Vibrio. These results suggest that the presence of EAB can promote the population of dechlorinating bacteria which are responsible for PCB 61 transformation.

In this work, bioremediation was applied with sinusoidal alternating current (AC) electric fields to remove petroleum hydrocarbon (TPH) for soil remediation. Applying AC electric field with bioremediation (AC+BIO) could efficiently remove 31.6% of the TPH in 21 days, much faster than that in the BIO only system (13.7%) and AC only system (5.5%). When the operation time extended to 119 days, the AC+BIO system could remove 73.3% of the TPH. Applying AC electric field (20–200 V/m) could maintain the soil pH at neutral, superior to the direct current electric field. The maximum difference between soil temperature and the room temperature was 1.9 °C in the AC (50 V/m) +BIO system. The effects of AC voltage gradient (20–200 V/m) on the microorganisms and TPH degradation efficiency by AC+BIO were investigated, and the optimized AC voltage gradient was assessed as 50 V/m for lab-scale experiments. The microbial community structures in the BIO and AC+BIO systems were compared. Although Pseudomonas was the dominant species, Firmicutes became more abundant in the AC+BIO system than the BIO system, indicating their adaptive capacity to the stress of the AC electric field. Real petroleum-contaminated soil was used as a reaction matrix to evaluate the performance of AC+BIO in the field. The initial current density was about 0.2 mA/cm², voltage gradient was about 20 V/m, and the average TPH degradation rate was 8.1 μg/gdᵣy ₛₒᵢₗ per day. This study provided insights and fundamental supports for the applications of AC+BIO to treat petroleum-polluted soils.

This study was carried out to investigate the efficacy of electrokinetics to remediate two identical soft kaolinite clay slurries with a water content of 70%. The first slurry was contaminated with copper at a concentration of 150 mg/kg of dry soil and the second with cadmium at the same concentration. The tests were performed in four identical electrokinetic columns (two for the electrokinetics tests and two for control) with a volume capacity of 14 L. An electric field intensity of 140 V/m was applied during 118 h of remediation with the top electrode serving as the anode (+ ve) and the bottom electrode acting as the cathode (− ve). The results showed that electrokinetics removed 2070 mL of water from the soil with copper contamination (compared to only 693 mL in the control test) and 1828 mL of water from the soils with cadmium contamination (compared to 839 mL in the control test). Electrokinetics was successful in removing significant portion of the copper and cadmium from most of the contaminated soil with the highest removal in copper (67%) and in cadmium (89%) in the soil sections near the anode. Electrokinetics was more effective in mobilizing the cadmium in the clay soil as compared to copper. Energy consumption determination revealed that electrokinetic remediation was successful in the removal of copper and cadmium from the section near the anode at rates of 77 and 100 mg/kg per kWh, respectively.

Dust particles suspended in the atmosphere have been a big headache for electric power transmission industry in China. As transmission lines pass through dusty or air-polluted areas, dust contaminants are likely to deposit and accumulate on line insulators, which is one of the greatest causes of flashover and failure of power transmission. To study the statistical characteristics of this type of contamination, dust samples were collected and measured, and a physical model was set up to explain the deposition and accumulation mechanism of the particles. The trajectories of particles were tracked using fluid mechanics and contact mechanics, and an adhesion criterion was proposed. Simulation software was then applied to validate the model; further different environmental factors were studied that would affect the particle size distribution. The results show that under natural contamination conditions, the particle size distribution on the surface of the insulator shows a certain concentration at size ranges 1~100 μm and basically obeys a log-normal distribution. In addition, relative humidity, air velocity, and the charge accumulated on the surface all have significant influences on particle size distribution characteristics, while the effect of the electric field is mainly reflected in the difference in the number concentration of particle adhesion.