Although widely used in permeation reaction barrier(PRB)for strengthening the removal of various heavy metals,zero-valent iron(ZVI)is limited by various inherent drawbacks,such as easy passivation and poor electron tr...Although widely used in permeation reaction barrier(PRB)for strengthening the removal of various heavy metals,zero-valent iron(ZVI)is limited by various inherent drawbacks,such as easy passivation and poor electron transfer.As a solution,a synergistic system with PRB and electrokinetics(PRB-EK)was established and applied for the efficient removal of Cr(Ⅵ)-contaminated groundwater.As the filling material of PRB,ZVI/Fe_(3)O_(4)/activated carbon(ZVI/Fe_(3)O_(4)/AC)composites were synthesized by ball milling and thermal treatment.A series of continuous flow column experiments and batch tests was conducted to evaluate the removal efficiency of Cr(Ⅵ).Results showed that the removal efficiency of Cr(Ⅵ)remained above 93%even when the bed volume(BV)reached 2000 under the operational parameters(iron/AC mass ratio,2:1;current,5 m A).The mechanism of Cr(Ⅵ)removal by the PRB-EK system was revealed through field emission scanning electron microscopy images,X-ray diffraction,X-ray photoelectron spectroscopy,Fe^(2+) concentration,and redox potential(E h)values.The key in Cr(Ⅵ)reduction was the Fe^(2+)/Fe^(3+) cycle driven by the surface microelectrolysis of the composites.The application of an externally supplied weak direct current maintained the redox process by enhancing the electron transfer capability of the system,thereby prolonging the column lifetime.Cr(Ⅵ)chemical speciation was determined through sequential extraction,verifying the stability and safety of the system.These findings provide a scientific basis for PRB design and the in-situ remediation of Cr(Ⅵ)-contaminated groundwater.展开更多
Loess as a subcategory of collapsible soils is a well-known aeolian deposit generally characterized as a highly-porous medium with relatively low natural density and water content and a high percentage of fine-grained...Loess as a subcategory of collapsible soils is a well-known aeolian deposit generally characterized as a highly-porous medium with relatively low natural density and water content and a high percentage of fine-grained particles.Such collapsible soil sustains large stresses under a dry condition with natural water content.However,it can experience high and relatively sudden decreases in its volume once it reaches a certain water content under a certain load and therefore,the natural condition of the soil might not be suitable for construction if the possibility of the exposure of the soil to excessive water exists during the lifetime of the project.This research presents the utilization of an innovative method for stabilization and improvement of Gorgan loessial soil.This method uses electrokinetics and nanomaterials to instigate additives to move through soil pores,as an in situ remedial measure.To assess the acceptability of this measure,the deformability and strength characteristics of the improved collapsible soil are measured and compared with those of the unimproved soil,implementing several unsaturated oedometer tests under constant vertical stress and varying matric suction.The result emphasizes the importance of the matric suction on the behavior of both improved and unimproved soils.The test results indicate that the resistance of the soil was highly dependent on the water content and matric suction of the soil.The oedometer tests on samples improved by 3%lime and 5%nanomaterials show considerable improvement of the collapse potential.Results also reveal that stabilized samples experience notably lower volume decrease under the same applied stresses.展开更多
Metal and acid ions contamination of soil in China is serious. To find an efficient solution for remediating the combined pollution,electrokinetics( EK) coupled with chitosan( CTS)permeable reactive barrier( EK/CPRB) ...Metal and acid ions contamination of soil in China is serious. To find an efficient solution for remediating the combined pollution,electrokinetics( EK) coupled with chitosan( CTS)permeable reactive barrier( EK/CPRB) was used to investigate the performances of metal and acid ions remediation. Adsorption characteristics of Zn^(2+),Fe^(3+),Ca^(2+),SO_4^(2-) and NO_3^- onto CTS were also conducted. The results showed the sorption of Zn^(2+),Fe^(3+),Ca^(2+),SO_4^(2-) and NO_3^- on CTS could be well described by Freundlich model. When the CTS dosage is 8 g,the total removal efficiency for Zn^(2+),Fe^(3+),Ca^(2+),SO_4^(2-) and NO_3^- is 86. 8%,90. 2%,92. 4%,90. 0% and 82. 5%,respectively. CTS enhanced ions remediation efficiencies significantly compared with the single EK system,especially for SO_4^(2-) and NO_3^-. The results indicate EK/CPRB system is suitable for the remediation of soil contaminated by both metal ions and acid ions.展开更多
Electrogravitics and electrokinetics can be traced to T. Townsend Brown’s first article “How I Control Gravity” (Science and Invention, 1929) with the unexplained alignment of the “molecular gravitors”. Brown rep...Electrogravitics and electrokinetics can be traced to T. Townsend Brown’s first article “How I Control Gravity” (Science and Invention, 1929) with the unexplained alignment of the “molecular gravitors”. Brown reported that the dielectrics had high propulsive force when the “differently charged elements” were aligned with the voltage source. Perhaps electrogravitics was also revealed in the article “Gravity Nullified: Quartz Crystals Charged by High Frequency Currents Lose Their Weight” which appeared two years earlier in the same magazine in September of 1927. The editors had a change of heart however, in the following issue, they rescinded the article. Much of what we know about T. T. Brown is from his numerous patents and articles, reprinted inElectrogravitics Systems Volume I, by this author who was fortunate to correspond with him in 1981 when he was at the University of Florida. A sample of his detailed correspondence is contained in the out-of-print book,?Ether-Technology:?A Rational Approach to Gravity-Control?by Rho Sigma (1977) and in the recent?Defying Gravity:?The Parallel Universe of T. Townsend Brown,?Paul Schatzkin, (2009, Embassy Books). Also, a five-minute Brown-Bahnson Lab video online shows many of the experimental models that Brown developed toward 1960 with colleague Agnew Bahnson? (http://www.youtube.com/watch?v=Rp4hygoD3RU).展开更多
[Objectives]This study was conducted to explore the removal performance and mechanism of heavy metal Cd in soil by combining electrokinetic technology and modified biochar.[Methods]The electrokinetics-magnetic/alkali ...[Objectives]This study was conducted to explore the removal performance and mechanism of heavy metal Cd in soil by combining electrokinetic technology and modified biochar.[Methods]The electrokinetics-magnetic/alkali composite-modified biochar method was applied to remediate Cd-contaminated soil.[Results]When remediating the soil for 120 h under electric field strength of 2 V/cm with 0.1 mol/L citric acid as the electrolyte,the current periodically varied with the remediation time.Cd^2+in the soil dissociated and migrated from the soil surface,and the addition of the magnetic/alkali composite-modified biochar in the cathode area affected the hydrolysis balance of heavy metal Cd^2+ions and maintained soil pH in a low range.The exchangeable Cd content at the test sampling points near the cathode area was relatively high,and the organic Cd area was evenly distributed.The average removal rate of Cd in the soil was up to 90.31%.The hexagonal anode device configuration enhanced the electromigration performance and made the soil pH and conductivity change within a certain range,which was beneficial to the migration of Cd2+and improved the removal rate of soil heavy metal Cd.[Conclusions]This study provides a theoretical basis for the treatment of soil heavy metal pollution and the resource utilization of composite-modified biochar.展开更多
We analytically describe the slip length of the surfactant-covered bubble film under the joint actions of pressure gradient and electric field.Considering the Marangoni effect,the slip length and consequent zeta poten...We analytically describe the slip length of the surfactant-covered bubble film under the joint actions of pressure gradient and electric field.Considering the Marangoni effect,the slip length and consequent zeta potential of the liquid‒vapor interface significantly reduced compared to the Marangoni-free interface at low surfactant concentrations,due to the surfactant accumulation at downstream of the bubble liquid film.In addition,we discovered that the friction coefficient of the liquid‒vapor interface becomes field dependent in a regime of strong coupling among volume flow,surfactant transport,and ionic current at the liquid‒vapor interface.We use the Onsager reciprocal relationship to describe the electrokinetic effects within a bubble film,including flow velocity,ionic current,and surfactant transport,which can describe theMarangoni effectswhile considering multi-physical effects.展开更多
The development of microengineered hydrogels has opened up unlimited possibilities for designing complex structures at the microscale. In this study, we constructed an origami-inspired tubular structure with controlle...The development of microengineered hydrogels has opened up unlimited possibilities for designing complex structures at the microscale. In this study, we constructed an origami-inspired tubular structure with controlled mechanical buckling based on optically induced electrokinetics(OEK). By inducing a stress gradient in the thickness, a tubular structure can be formed from a poly(ethylene glycol) diacrylate(PEGDA) hydrogel film of various shapes that have been custom fabricated. To achieve an ideal three-dimensional(3D) structure, the amplitude of the tubular structure can be controlled by adjusting the aspect ratios or polymerization time. Furthermore, the tubular structure can be manipulated for the collection and transportation of microspheres.In summary, we provide an effective method for designing 3D structures at the micro-nano scale. This forming method holds great potential for achieving various functions in tissue engineering, drug packaging, and transportation in the future.展开更多
Convenient non-invasive flow monitoring would facilitate the operation and control in microfluidic chips,but is challenging due to the small space of microchannels and complex operation required in traditional optical...Convenient non-invasive flow monitoring would facilitate the operation and control in microfluidic chips,but is challenging due to the small space of microchannels and complex operation required in traditional optical methods.In this work,we propose a novel non-invasive strategy to probe microfluidic flows via streaming potential phenomenon.By sealing one side of the microchannel with a piece of hydrogel film,streaming potential inside the channel can be clearly detected by electrodes at outer surface of the hydrogel due to ion diffusion in the hydrogel.Flow is detected without sensors contacting with the internal liquid.Moreover,the electrodes shape like a tiny probe,which can move around mapping the flow distribution in a chip with the spatial resolution of 1 mm and flow rate detection limit of 3μL·min–1.Bubbles inside the channels can also be detected,due to the fluctuation of streaming voltage when gas-liquid interface flows through the electrode,showing an easy and potential way for multi-functional flow monitoring in microfluidic chips.展开更多
The electrokinetic(EK)process has been proposed for soil decontamination from heavy metals and organic matter.The advantages of the EK process include the low operating energy,suitability for fine-grained soil deconta...The electrokinetic(EK)process has been proposed for soil decontamination from heavy metals and organic matter.The advantages of the EK process include the low operating energy,suitability for fine-grained soil decontamination,and no need for excavation.During the last three decades,enhanced and hybrid EK systems were developed and tested for improving the efficiency of contaminants removal from soils.Chemically enhanced-EK processes exhibited excellent efficiency in removing contaminants by controlling the soil pH or the chemical reaction of contaminants.EK hybrid systems were tested to overcome environmental hurdles or technical drawbacks of decontamination technologies.Hybridization of the EK process with phytoremediation,bioremediation,or reactive filtermedia(RFM)improved the remediation process performance by capturing contaminants or facilitating biological agents’movement in the soil.Also,EK process coupling with solar energy was proposed to treat off-grid contaminated soils or reduce the EK energy requirements.This study reviews recent advancements in the enhancement and hybrid EK systems for soil remediation and the type of contaminants targeted by the process.The study also covered the impact of operating parameters,imperfect pollution separation,and differences in the physicochemical characteristics and microstructure of soil/sediment on the EK performance.Finally,a comparison between various remediation processes was presented to highlight the pros and cons of these technologies.展开更多
Ion-absorption deposits(IADs)of rare earth elements(REEs)constitute the main economic resources of the essential heavy rare earth elements(HREE).Nonetheless,the existing leaching methods for extracting REEs from IADs ...Ion-absorption deposits(IADs)of rare earth elements(REEs)constitute the main economic resources of the essential heavy rare earth elements(HREE).Nonetheless,the existing leaching methods for extracting REEs from IADs face limitations stemming from significant environmental consequences and a poor REE recovery rate.In a recent development,electrokinetic mining(EKM)has emerged as a novel technology for extracting REEs from ion-adsorption deposits,demonstrating the potential for environmentally friendly and efficient recovery of REEs from weathering crusts.However,the transport mechanism of REE in weathering crust soil in an applied electric field remains poorly understood,and the influence of the EKM process has yet to be studied.In this study,we systematically investigated the transport characteristics of REE in weathering crust soil under the influence of an electric field.We demonstrate that the transport of REE is simultaneous with the transport of water,H+,and OH-in the applied electric field,where the EKM process is influenced by the voltage gradient,initial soil water content,electrode numbers,and power-on time.Under the optimal EKM conditions,78,8%of REE is recovered from a 45 kg-scale weathering crust soil.Additionally,we identify the transport diversity between light REE(LREE)and HREE,which assists in the separation and pre-enrichment of LREE and HREE.Furthermore,we demonstrate that the mechanism for REE transport under an electric field involves a combination of electromigration,electroosmosis,and electrolysis working synergistically.This study provides new perspectives on the transport behavior and mechanism of REEs in weathering crust soil under an electric field.These findings pave the way for the practical implementation of EKM technology.展开更多
Slow release of emerging contaminants limits their accessibility from soil to pore water,constraining the treatment efficiency of physio-chemical treatment sites.DC fields mobilize organic contaminants and influence t...Slow release of emerging contaminants limits their accessibility from soil to pore water,constraining the treatment efficiency of physio-chemical treatment sites.DC fields mobilize organic contaminants and influence their interactions with geo-matrices such as zeolites.Poor knowledge,however,exists on the joint application of heating and electrokinetic approaches on perfluorooctanoic acid(PFOA)transport in porous media.Here,we investigated electrokinetic PFOA transport in zeolite-filled percolation columns at varying temperatures.Variations of pseudo-second-order kinetic constants(kPSO)were correlated to the liquid viscosity variations(η)and elctroosmotic flow velocities(vEOF).Applying DC fields and elevated temperature significantly(>37%)decreased PFOA sorption to zeolite.A good correlation betweenη,vEOF,and kPSO was found and used to develop an approach interlinking the three parameters to predict the joint effects of DC fields and temperature on PFOA sorption kinetics.These findings may give rise to future applications for better tailoring PFOA transport in environmental biotechnology.展开更多
Microflow driven by AC electrothermal pumping electrolytes with high conductivity fluid （ACET） effect is explored in order to seek new methods for （more than 0. 02 S/m） at microscale. Based on the ACET theory, a p...Microflow driven by AC electrothermal pumping electrolytes with high conductivity fluid （ACET） effect is explored in order to seek new methods for （more than 0. 02 S/m） at microscale. Based on the ACET theory, a physical model for particle trapping is established by a set of electrostatics, heat transfer and fluid dynamic equations. Further, fluid velocity fields are predicted using the software FEMLAB. Experiments are performed which verify the numerical results. The experimental results show that with appropriate electrode design, ACET effect can work on fluids with conductivity up to I. 53 S/m and trap particles at a low voltage. ACET devices can be readily integrated on chip into a microsystem. This offers insight into designing ACET lab-chips.展开更多
To improve the conventional electrokinetic remediation of Pb-contaminated soil,the Pb-contaminated soil near a lead acid battery factory in the Pearl River Delta region of China was electrokinetically remedied with po...To improve the conventional electrokinetic remediation of Pb-contaminated soil,the Pb-contaminated soil near a lead acid battery factory in the Pearl River Delta region of China was electrokinetically remedied with polarity exchange technique.The variations in Pb removal efficiency and the soil p H value with the treatment time and the exchange polarity interval were determined.It is found that the removal efficiency of Pb reaches a maximum of 87.7% when the voltage gradient is 1 V/cm and the exchange polarity interval is 48 h.This value is far higher than that obtained with conventional electrokinetic remediation（61.8%）.Additionally,the ＂focusing effect＂ which appears in the conventional electrokinetic remediation can be avoided,and thus additional chemicals are not needed for the polarity exchange technique.The mechanism of Pb electromigration behavior in soil during the treatment with the polarity exchange technique was described.展开更多
Since the early 1980’s there have been several different strategies designed and applied to the remediation of subsurface environment including physical, chemical and biological approaches.They have had varying degre...Since the early 1980’s there have been several different strategies designed and applied to the remediation of subsurface environment including physical, chemical and biological approaches.They have had varying degrees of success in remediating contaminants from subsurface soils and groundwater.The objective of this review is to examine the range of technologies for the remediation of contaminants, particularly petroleum hydrocarbons, in subsurfaces with a specific focus on bioremediation and electrokinetic remediation.Further, this review examines the efficiency of remediation carried out by combining bioremediation and electrokinetic remediation.Surfactants, which are slowly becoming the selected chemicals for mobilizing contaminants, are also considered in this review.The current knowledge gaps of these technologies and techniques identified which could lead to development of more efficient ways of utilizing these technologies or development of a completely new technology.展开更多
The mature fine oil sand tailings(MFT) remain as slurry in the tailings pond for long time. The dewatering and consolidation of MFT for sustainable management is an important task for the mining industry. The objectiv...The mature fine oil sand tailings(MFT) remain as slurry in the tailings pond for long time. The dewatering and consolidation of MFT for sustainable management is an important task for the mining industry. The objective of this study is to accelerate electrokinetic settling of MFT solids in suspensions in presence of optimal coagulant. In the first phase, optimal coagulant and coagulant dosage for settling of suspension are identified, i.e., ferric chloride at 350 mg/L. It is found that the chemical treatment is not much effective; the final solid content of the sediment is only 6.48% from an initial of 5%. In the second phase,combined coagulation and electrokinetic treatment is carried out to enhance the settling effect. The direct electric current is applied in continuous and intermittent modes on MFT suspensions placed in electrokinetic cell. The results show the final solid content reaches 23.74% under the combined application of350 mg/L ferric chloride and 218.75 V/m applied voltage gradient in the continuous mode. The intermittent current mode with 40% save in power consumption produces a settled sediment having 20.84% final solid content.展开更多
To explore the application of the characteristics of metallic microparticles, alternating current electric trapping of the SU-8 microrods coated with a thin gold layer by the chemical approach is investigated. Positiv...To explore the application of the characteristics of metallic microparticles, alternating current electric trapping of the SU-8 microrods coated with a thin gold layer by the chemical approach is investigated. Positive dielectrophoresis is used to absorb the gold-coated SU-8 microrods at the edge of the parallel electrodes, thereby forming chains to connect the electrodes. This is a fast automatic microcircuit formation process. Moreover, a non-charged molecule is modified on the surface of the gold-coated SU-8 microrod, and the modified microrods are controlled by the alternating electric field to form a number of chains. The different chains between the parallel electrodes consist of various parallel circuits. In order to compare these chains with different electric surfaces, the impedances of the metallic and modified microrods are measured and compared, and the results show that the gold-coated microrods act as pure resistors, while the microrods functionalized by a non-charged molecule behave as good capacitors.展开更多
We designed a new downhole electrokinetic logging tool based on numericalsimulations and petrophysical experiments. Acoustic and electric receivers cannot be arrangedat the same depth, and the proposed composite elect...We designed a new downhole electrokinetic logging tool based on numericalsimulations and petrophysical experiments. Acoustic and electric receivers cannot be arrangedat the same depth, and the proposed composite electrokinetic logging tool offers a solutionto this problem. The sound field characteristics of the detectors were tested in a water tank inthe laboratory. Then, we calculated the sound pressure of the radiated acoustic field and thetransmitting voltage response of the transmitting transducers; in addition, we analyzed thedirectivity and application of the acoustic transmitting probe based on linear phased array.The results suggest that the sound pressure generated at 1500 mm spacing reaches up to 47.2k Pa and decreases with increasing acoustic source frequency. When the excitation signalsdelay time of adjacent acoustic transmitting subarrays increases, the radiation beam of themain lobe is deflected and its energy gradually increases, which presumably enhances theacoustoelectric conversion efficiency.展开更多
In the present paper we give a brief summary of some recent theoretical advances in the treatment of inhomogeneous fluids and methods which have applications in the study of dynamical properties of liquids in situatio...In the present paper we give a brief summary of some recent theoretical advances in the treatment of inhomogeneous fluids and methods which have applications in the study of dynamical properties of liquids in situations of extreme confinement, such as nanopores, nanodevices, etc. The approach obtained by combining kinetic and density functional methods is microscopic, fully self-consistent and allows to determine both configurational and flow properties of dense fluids. The theory predicts the correct hydrodynamic behavior and provides a practical and numerical tool to determine how the transport properties are modified when the length scales of the confining channels are comparable with the size of the molecules. The applications range from the dynamics of simple fluids under confinement, to that of neutral binary mixtures and electrolytes where the theory in the limit of slow gradients reproduces the known phenomenological equations such as the Planck–Nernst–Poisson and the Smolochowski equations. The approach here illustrated allows for fast numerical solution of the evolution equations for the one-particle phase-space distributions by means of the weighted density lattice Boltzmann method and is particularly useful when one considers flows in complex geometries.展开更多
Electrokinetic(EK)micromixers have been widely studied in the past decade for biochemical applications,biological and chemical analysis,etc.Unfortunately,almost all EK mixers require different electrical conductivity ...Electrokinetic(EK)micromixers have been widely studied in the past decade for biochemical applications,biological and chemical analysis,etc.Unfortunately,almost all EK mixers require different electrical conductivity between the two fluids to be mixed,which has greatly limited their wide applications,in cases where the two streams to be mixed have equivalent electrical conductivity.Here we show that mixing enhancement between two fluids with identical conductivity can be achieved in an EK micromixer with conductive sidewalls,where the electric field is in transverse direction of the flow.The results revealed that the mixing became stronger with increased conductivity value.This mixing method provides a novel and convenient strategy for mixing two liquids with the same or similar electrical conductivity in microfluidic systems,and could potentially serves as a powerful tool for sample preparation in applications such as liquid biopsy,and environmental monitoring,etc.展开更多
The seismoelectrical method(also called the Electroseismic method or seismo-electric) is based on the generation of electromagnetic fields in soils and rocks by seismic waves.Although the method is not reported to det...The seismoelectrical method(also called the Electroseismic method or seismo-electric) is based on the generation of electromagnetic fields in soils and rocks by seismic waves.Although the method is not reported to detect groundwater flow,it does measure the hydraulic conductivity,which is related to permeability and,therefore,to the potential of groundwater flow.Electroseismic technology is an effective tool for the siting of water wells。展开更多
基金financial support from the National Natural Science Foundation of China(Nos.21906044 and 21477034)the Key Science and Technology Program of Henan Province,China(No.132102210129)+3 种基金the Basic Scientific and Technological Frontier Project of Henan Province(No.162300410046)the Innovation Scientists and Technicians Troop Construction Projects of Henan Province,the Scientific Research Foundation from Soochow University(No.Q416000117)the Technology Department of the Henan Science and Technology Fund Project(No.202102310603)the Cultivating National Scientific Research Project Funds,Henan Normal University(No.5101219170804)。
文摘Although widely used in permeation reaction barrier(PRB)for strengthening the removal of various heavy metals,zero-valent iron(ZVI)is limited by various inherent drawbacks,such as easy passivation and poor electron transfer.As a solution,a synergistic system with PRB and electrokinetics(PRB-EK)was established and applied for the efficient removal of Cr(Ⅵ)-contaminated groundwater.As the filling material of PRB,ZVI/Fe_(3)O_(4)/activated carbon(ZVI/Fe_(3)O_(4)/AC)composites were synthesized by ball milling and thermal treatment.A series of continuous flow column experiments and batch tests was conducted to evaluate the removal efficiency of Cr(Ⅵ).Results showed that the removal efficiency of Cr(Ⅵ)remained above 93%even when the bed volume(BV)reached 2000 under the operational parameters(iron/AC mass ratio,2:1;current,5 m A).The mechanism of Cr(Ⅵ)removal by the PRB-EK system was revealed through field emission scanning electron microscopy images,X-ray diffraction,X-ray photoelectron spectroscopy,Fe^(2+) concentration,and redox potential(E h)values.The key in Cr(Ⅵ)reduction was the Fe^(2+)/Fe^(3+) cycle driven by the surface microelectrolysis of the composites.The application of an externally supplied weak direct current maintained the redox process by enhancing the electron transfer capability of the system,thereby prolonging the column lifetime.Cr(Ⅵ)chemical speciation was determined through sequential extraction,verifying the stability and safety of the system.These findings provide a scientific basis for PRB design and the in-situ remediation of Cr(Ⅵ)-contaminated groundwater.
文摘Loess as a subcategory of collapsible soils is a well-known aeolian deposit generally characterized as a highly-porous medium with relatively low natural density and water content and a high percentage of fine-grained particles.Such collapsible soil sustains large stresses under a dry condition with natural water content.However,it can experience high and relatively sudden decreases in its volume once it reaches a certain water content under a certain load and therefore,the natural condition of the soil might not be suitable for construction if the possibility of the exposure of the soil to excessive water exists during the lifetime of the project.This research presents the utilization of an innovative method for stabilization and improvement of Gorgan loessial soil.This method uses electrokinetics and nanomaterials to instigate additives to move through soil pores,as an in situ remedial measure.To assess the acceptability of this measure,the deformability and strength characteristics of the improved collapsible soil are measured and compared with those of the unimproved soil,implementing several unsaturated oedometer tests under constant vertical stress and varying matric suction.The result emphasizes the importance of the matric suction on the behavior of both improved and unimproved soils.The test results indicate that the resistance of the soil was highly dependent on the water content and matric suction of the soil.The oedometer tests on samples improved by 3%lime and 5%nanomaterials show considerable improvement of the collapse potential.Results also reveal that stabilized samples experience notably lower volume decrease under the same applied stresses.
基金National Natural Science Foundations of China(Nos.21477018,21007010)the Fundamental Research Funds for the Central Universities,China(No.15D111323)+1 种基金Hunan Province Ministry of Transportation Scientific Research Projects,China(Nos.200908,201105)Ministry of Transport Science and Technology Program,China(No.2010353343290)
文摘Metal and acid ions contamination of soil in China is serious. To find an efficient solution for remediating the combined pollution,electrokinetics( EK) coupled with chitosan( CTS)permeable reactive barrier( EK/CPRB) was used to investigate the performances of metal and acid ions remediation. Adsorption characteristics of Zn^(2+),Fe^(3+),Ca^(2+),SO_4^(2-) and NO_3^- onto CTS were also conducted. The results showed the sorption of Zn^(2+),Fe^(3+),Ca^(2+),SO_4^(2-) and NO_3^- on CTS could be well described by Freundlich model. When the CTS dosage is 8 g,the total removal efficiency for Zn^(2+),Fe^(3+),Ca^(2+),SO_4^(2-) and NO_3^- is 86. 8%,90. 2%,92. 4%,90. 0% and 82. 5%,respectively. CTS enhanced ions remediation efficiencies significantly compared with the single EK system,especially for SO_4^(2-) and NO_3^-. The results indicate EK/CPRB system is suitable for the remediation of soil contaminated by both metal ions and acid ions.
文摘Electrogravitics and electrokinetics can be traced to T. Townsend Brown’s first article “How I Control Gravity” (Science and Invention, 1929) with the unexplained alignment of the “molecular gravitors”. Brown reported that the dielectrics had high propulsive force when the “differently charged elements” were aligned with the voltage source. Perhaps electrogravitics was also revealed in the article “Gravity Nullified: Quartz Crystals Charged by High Frequency Currents Lose Their Weight” which appeared two years earlier in the same magazine in September of 1927. The editors had a change of heart however, in the following issue, they rescinded the article. Much of what we know about T. T. Brown is from his numerous patents and articles, reprinted inElectrogravitics Systems Volume I, by this author who was fortunate to correspond with him in 1981 when he was at the University of Florida. A sample of his detailed correspondence is contained in the out-of-print book,?Ether-Technology:?A Rational Approach to Gravity-Control?by Rho Sigma (1977) and in the recent?Defying Gravity:?The Parallel Universe of T. Townsend Brown,?Paul Schatzkin, (2009, Embassy Books). Also, a five-minute Brown-Bahnson Lab video online shows many of the experimental models that Brown developed toward 1960 with colleague Agnew Bahnson? (http://www.youtube.com/watch?v=Rp4hygoD3RU).
基金Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX20_2582)。
文摘[Objectives]This study was conducted to explore the removal performance and mechanism of heavy metal Cd in soil by combining electrokinetic technology and modified biochar.[Methods]The electrokinetics-magnetic/alkali composite-modified biochar method was applied to remediate Cd-contaminated soil.[Results]When remediating the soil for 120 h under electric field strength of 2 V/cm with 0.1 mol/L citric acid as the electrolyte,the current periodically varied with the remediation time.Cd^2+in the soil dissociated and migrated from the soil surface,and the addition of the magnetic/alkali composite-modified biochar in the cathode area affected the hydrolysis balance of heavy metal Cd^2+ions and maintained soil pH in a low range.The exchangeable Cd content at the test sampling points near the cathode area was relatively high,and the organic Cd area was evenly distributed.The average removal rate of Cd in the soil was up to 90.31%.The hexagonal anode device configuration enhanced the electromigration performance and made the soil pH and conductivity change within a certain range,which was beneficial to the migration of Cd2+and improved the removal rate of soil heavy metal Cd.[Conclusions]This study provides a theoretical basis for the treatment of soil heavy metal pollution and the resource utilization of composite-modified biochar.
基金National Natural Science Foundation of China,Grant/Award Numbers:12388101,12241201Innovation Capability Support Programof Shaanxi,Grant/Award Number:2024RS-CXTD-15。
文摘We analytically describe the slip length of the surfactant-covered bubble film under the joint actions of pressure gradient and electric field.Considering the Marangoni effect,the slip length and consequent zeta potential of the liquid‒vapor interface significantly reduced compared to the Marangoni-free interface at low surfactant concentrations,due to the surfactant accumulation at downstream of the bubble liquid film.In addition,we discovered that the friction coefficient of the liquid‒vapor interface becomes field dependent in a regime of strong coupling among volume flow,surfactant transport,and ionic current at the liquid‒vapor interface.We use the Onsager reciprocal relationship to describe the electrokinetic effects within a bubble film,including flow velocity,ionic current,and surfactant transport,which can describe theMarangoni effectswhile considering multi-physical effects.
基金supported by the National Natural Science Foundation of China(Grant No.62273289)the Youth Innovation Science and Technology Support Program of Shandong Province(Grant No.2022KJ274)。
文摘The development of microengineered hydrogels has opened up unlimited possibilities for designing complex structures at the microscale. In this study, we constructed an origami-inspired tubular structure with controlled mechanical buckling based on optically induced electrokinetics(OEK). By inducing a stress gradient in the thickness, a tubular structure can be formed from a poly(ethylene glycol) diacrylate(PEGDA) hydrogel film of various shapes that have been custom fabricated. To achieve an ideal three-dimensional(3D) structure, the amplitude of the tubular structure can be controlled by adjusting the aspect ratios or polymerization time. Furthermore, the tubular structure can be manipulated for the collection and transportation of microspheres.In summary, we provide an effective method for designing 3D structures at the micro-nano scale. This forming method holds great potential for achieving various functions in tissue engineering, drug packaging, and transportation in the future.
基金supported by the National Natural Science Foundation of China(Grant Nos.51976141,52006123,62161160311).
文摘Convenient non-invasive flow monitoring would facilitate the operation and control in microfluidic chips,but is challenging due to the small space of microchannels and complex operation required in traditional optical methods.In this work,we propose a novel non-invasive strategy to probe microfluidic flows via streaming potential phenomenon.By sealing one side of the microchannel with a piece of hydrogel film,streaming potential inside the channel can be clearly detected by electrodes at outer surface of the hydrogel due to ion diffusion in the hydrogel.Flow is detected without sensors contacting with the internal liquid.Moreover,the electrodes shape like a tiny probe,which can move around mapping the flow distribution in a chip with the spatial resolution of 1 mm and flow rate detection limit of 3μL·min–1.Bubbles inside the channels can also be detected,due to the fluctuation of streaming voltage when gas-liquid interface flows through the electrode,showing an easy and potential way for multi-functional flow monitoring in microfluidic chips.
文摘The electrokinetic(EK)process has been proposed for soil decontamination from heavy metals and organic matter.The advantages of the EK process include the low operating energy,suitability for fine-grained soil decontamination,and no need for excavation.During the last three decades,enhanced and hybrid EK systems were developed and tested for improving the efficiency of contaminants removal from soils.Chemically enhanced-EK processes exhibited excellent efficiency in removing contaminants by controlling the soil pH or the chemical reaction of contaminants.EK hybrid systems were tested to overcome environmental hurdles or technical drawbacks of decontamination technologies.Hybridization of the EK process with phytoremediation,bioremediation,or reactive filtermedia(RFM)improved the remediation process performance by capturing contaminants or facilitating biological agents’movement in the soil.Also,EK process coupling with solar energy was proposed to treat off-grid contaminated soils or reduce the EK energy requirements.This study reviews recent advancements in the enhancement and hybrid EK systems for soil remediation and the type of contaminants targeted by the process.The study also covered the impact of operating parameters,imperfect pollution separation,and differences in the physicochemical characteristics and microstructure of soil/sediment on the EK performance.Finally,a comparison between various remediation processes was presented to highlight the pros and cons of these technologies.
基金Projects supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA0430205)Guangdong Major Project of Basic and Applied Basic Research(2019B030302013)+2 种基金National Natural Science Foundation of China(42102037,42272158)Guangdong Basic and Applied Basic Research Foundation(2023A1515012927)Science and Technology Planning of Guangdong Province,China(2023B1212060048)。
文摘Ion-absorption deposits(IADs)of rare earth elements(REEs)constitute the main economic resources of the essential heavy rare earth elements(HREE).Nonetheless,the existing leaching methods for extracting REEs from IADs face limitations stemming from significant environmental consequences and a poor REE recovery rate.In a recent development,electrokinetic mining(EKM)has emerged as a novel technology for extracting REEs from ion-adsorption deposits,demonstrating the potential for environmentally friendly and efficient recovery of REEs from weathering crusts.However,the transport mechanism of REE in weathering crust soil in an applied electric field remains poorly understood,and the influence of the EKM process has yet to be studied.In this study,we systematically investigated the transport characteristics of REE in weathering crust soil under the influence of an electric field.We demonstrate that the transport of REE is simultaneous with the transport of water,H+,and OH-in the applied electric field,where the EKM process is influenced by the voltage gradient,initial soil water content,electrode numbers,and power-on time.Under the optimal EKM conditions,78,8%of REE is recovered from a 45 kg-scale weathering crust soil.Additionally,we identify the transport diversity between light REE(LREE)and HREE,which assists in the separation and pre-enrichment of LREE and HREE.Furthermore,we demonstrate that the mechanism for REE transport under an electric field involves a combination of electromigration,electroosmosis,and electrolysis working synergistically.This study provides new perspectives on the transport behavior and mechanism of REEs in weathering crust soil under an electric field.These findings pave the way for the practical implementation of EKM technology.
基金supported by the National Natural Science Foundation of China(No.42277011)the fellowship of the China Postdoctoral Science Foundation(Nos.2023T160667 and 2022M713300)。
文摘Slow release of emerging contaminants limits their accessibility from soil to pore water,constraining the treatment efficiency of physio-chemical treatment sites.DC fields mobilize organic contaminants and influence their interactions with geo-matrices such as zeolites.Poor knowledge,however,exists on the joint application of heating and electrokinetic approaches on perfluorooctanoic acid(PFOA)transport in porous media.Here,we investigated electrokinetic PFOA transport in zeolite-filled percolation columns at varying temperatures.Variations of pseudo-second-order kinetic constants(kPSO)were correlated to the liquid viscosity variations(η)and elctroosmotic flow velocities(vEOF).Applying DC fields and elevated temperature significantly(>37%)decreased PFOA sorption to zeolite.A good correlation betweenη,vEOF,and kPSO was found and used to develop an approach interlinking the three parameters to predict the joint effects of DC fields and temperature on PFOA sorption kinetics.These findings may give rise to future applications for better tailoring PFOA transport in environmental biotechnology.
基金US National Science Foundation ( No ECS-0448896)Tennessee Science Alliance Award
文摘Microflow driven by AC electrothermal pumping electrolytes with high conductivity fluid （ACET） effect is explored in order to seek new methods for （more than 0. 02 S/m） at microscale. Based on the ACET theory, a physical model for particle trapping is established by a set of electrostatics, heat transfer and fluid dynamic equations. Further, fluid velocity fields are predicted using the software FEMLAB. Experiments are performed which verify the numerical results. The experimental results show that with appropriate electrode design, ACET effect can work on fluids with conductivity up to I. 53 S/m and trap particles at a low voltage. ACET devices can be readily integrated on chip into a microsystem. This offers insight into designing ACET lab-chips.
基金Project(21003054)supported by the National Natural Science Foundation of ChinaProject(2013CXZDA013)supported by the Scientific Research Foundation of the Education Department of Guangdong Province,China
文摘To improve the conventional electrokinetic remediation of Pb-contaminated soil,the Pb-contaminated soil near a lead acid battery factory in the Pearl River Delta region of China was electrokinetically remedied with polarity exchange technique.The variations in Pb removal efficiency and the soil p H value with the treatment time and the exchange polarity interval were determined.It is found that the removal efficiency of Pb reaches a maximum of 87.7% when the voltage gradient is 1 V/cm and the exchange polarity interval is 48 h.This value is far higher than that obtained with conventional electrokinetic remediation（61.8%）.Additionally,the ＂focusing effect＂ which appears in the conventional electrokinetic remediation can be avoided,and thus additional chemicals are not needed for the polarity exchange technique.The mechanism of Pb electromigration behavior in soil during the treatment with the polarity exchange technique was described.
基金funded through Cooperative Research Center for Contamination Assessment and Remediation of the Environment (CRC CARE)the University of Newcastle.
文摘Since the early 1980’s there have been several different strategies designed and applied to the remediation of subsurface environment including physical, chemical and biological approaches.They have had varying degrees of success in remediating contaminants from subsurface soils and groundwater.The objective of this review is to examine the range of technologies for the remediation of contaminants, particularly petroleum hydrocarbons, in subsurfaces with a specific focus on bioremediation and electrokinetic remediation.Further, this review examines the efficiency of remediation carried out by combining bioremediation and electrokinetic remediation.Surfactants, which are slowly becoming the selected chemicals for mobilizing contaminants, are also considered in this review.The current knowledge gaps of these technologies and techniques identified which could lead to development of more efficient ways of utilizing these technologies or development of a completely new technology.
基金the support of The University of Western Ontario and the Natural Science and Engineering Research Council of Canada (NSERC)
文摘The mature fine oil sand tailings(MFT) remain as slurry in the tailings pond for long time. The dewatering and consolidation of MFT for sustainable management is an important task for the mining industry. The objective of this study is to accelerate electrokinetic settling of MFT solids in suspensions in presence of optimal coagulant. In the first phase, optimal coagulant and coagulant dosage for settling of suspension are identified, i.e., ferric chloride at 350 mg/L. It is found that the chemical treatment is not much effective; the final solid content of the sediment is only 6.48% from an initial of 5%. In the second phase,combined coagulation and electrokinetic treatment is carried out to enhance the settling effect. The direct electric current is applied in continuous and intermittent modes on MFT suspensions placed in electrokinetic cell. The results show the final solid content reaches 23.74% under the combined application of350 mg/L ferric chloride and 218.75 V/m applied voltage gradient in the continuous mode. The intermittent current mode with 40% save in power consumption produces a settled sediment having 20.84% final solid content.
基金supported by the National Natural Science Foundation of China(Grant No.51075087)the Funds from the State Key Laboratory of Fluid Power Transmission and Control,Zhejiang University,China(Grant Nos.GZKF-201107 and GZKF-201004)the Foundation from the China Scholarship Council(Grant No.2009612129)
文摘To explore the application of the characteristics of metallic microparticles, alternating current electric trapping of the SU-8 microrods coated with a thin gold layer by the chemical approach is investigated. Positive dielectrophoresis is used to absorb the gold-coated SU-8 microrods at the edge of the parallel electrodes, thereby forming chains to connect the electrodes. This is a fast automatic microcircuit formation process. Moreover, a non-charged molecule is modified on the surface of the gold-coated SU-8 microrod, and the modified microrods are controlled by the alternating electric field to form a number of chains. The different chains between the parallel electrodes consist of various parallel circuits. In order to compare these chains with different electric surfaces, the impedances of the metallic and modified microrods are measured and compared, and the results show that the gold-coated microrods act as pure resistors, while the microrods functionalized by a non-charged molecule behave as good capacitors.
基金supported by the National Science Foundation of China(No.61102102,11134011,11204380 and 11374371)Major National Science and Technology Projects(No.2011ZX05020-009)+1 种基金Science and Technology Project of CNPC(No.2014A-3912 and 2011B-4001)Petro China Innovation Foundation(No.2014D-5006-0307)
文摘We designed a new downhole electrokinetic logging tool based on numericalsimulations and petrophysical experiments. Acoustic and electric receivers cannot be arrangedat the same depth, and the proposed composite electrokinetic logging tool offers a solutionto this problem. The sound field characteristics of the detectors were tested in a water tank inthe laboratory. Then, we calculated the sound pressure of the radiated acoustic field and thetransmitting voltage response of the transmitting transducers; in addition, we analyzed thedirectivity and application of the acoustic transmitting probe based on linear phased array.The results suggest that the sound pressure generated at 1500 mm spacing reaches up to 47.2k Pa and decreases with increasing acoustic source frequency. When the excitation signalsdelay time of adjacent acoustic transmitting subarrays increases, the radiation beam of themain lobe is deflected and its energy gradually increases, which presumably enhances theacoustoelectric conversion efficiency.
文摘In the present paper we give a brief summary of some recent theoretical advances in the treatment of inhomogeneous fluids and methods which have applications in the study of dynamical properties of liquids in situations of extreme confinement, such as nanopores, nanodevices, etc. The approach obtained by combining kinetic and density functional methods is microscopic, fully self-consistent and allows to determine both configurational and flow properties of dense fluids. The theory predicts the correct hydrodynamic behavior and provides a practical and numerical tool to determine how the transport properties are modified when the length scales of the confining channels are comparable with the size of the molecules. The applications range from the dynamics of simple fluids under confinement, to that of neutral binary mixtures and electrolytes where the theory in the limit of slow gradients reproduces the known phenomenological equations such as the Planck–Nernst–Poisson and the Smolochowski equations. The approach here illustrated allows for fast numerical solution of the evolution equations for the one-particle phase-space distributions by means of the weighted density lattice Boltzmann method and is particularly useful when one considers flows in complex geometries.
基金partially supported by the North American Mixing Forum (NAMF), NSF CAREER (CBET-0954977)the National Natural Science Foundation of China(21705055)+1 种基金Science and Technology Development Planning Program of Jilin Province(20190201178JC)Jilin Province Industrial Technology Research and Development Project(2019C048-5)
文摘Electrokinetic(EK)micromixers have been widely studied in the past decade for biochemical applications,biological and chemical analysis,etc.Unfortunately,almost all EK mixers require different electrical conductivity between the two fluids to be mixed,which has greatly limited their wide applications,in cases where the two streams to be mixed have equivalent electrical conductivity.Here we show that mixing enhancement between two fluids with identical conductivity can be achieved in an EK micromixer with conductive sidewalls,where the electric field is in transverse direction of the flow.The results revealed that the mixing became stronger with increased conductivity value.This mixing method provides a novel and convenient strategy for mixing two liquids with the same or similar electrical conductivity in microfluidic systems,and could potentially serves as a powerful tool for sample preparation in applications such as liquid biopsy,and environmental monitoring,etc.
文摘The seismoelectrical method(also called the Electroseismic method or seismo-electric) is based on the generation of electromagnetic fields in soils and rocks by seismic waves.Although the method is not reported to detect groundwater flow,it does measure the hydraulic conductivity,which is related to permeability and,therefore,to the potential of groundwater flow.Electroseismic technology is an effective tool for the siting of water wells。
