DC Voltage Gradient Research Articles

Enhanced of electro-kinetic technology for removal of lead ions from silty clay contaminated soil using EDTA and multi anode electrode

The techniques of fixed and approaching anodes have been utilized in this study using polygonal electrodes arranged in the form as one cathode and four anodes. Disodium ethylenediaminetetraacetic acid (EDTA-Na2) and Distilled Water (DW) was used as purging solutions in the treatment of lead contaminated soil with a concentration of (750 mg / kg). In all experiments was applied a 1.5 V/cm as a constant DC voltage gradient. Results showed that the pH value decreases especially in the approaching anode technique. The average lead removal efficiency at both line of sampling points A and B in EK-3 (fixed anode technique) was 64 and 67%, respectively, and in EK-4 (approaching anode technique) was 68.1 and 71%, respectively, when was used 0.2 M EDTA as purging solution. And that reduction rate was lower when Distilled Water is used.

Experimental studies of: Laminate composition, drill bit wear out, and chloride ion concentration as factors affecting CAF formation rate

In industrial, aerospace, medical and other mission critical electronics employing high density interconnection PCBs, high DC voltage gradient and adverse environmental conditions facilitate Conductive Anodic Filament (CAF) formation. To prevent catastrophic failures caused by CAF short circuits, monitoring of manufacturing process and proper laminate selection is essential. The purpose of presented work was to evaluate CAF resistance level of FR4, low CTE, CAF resistant and BT/epoxy-based laminates. Test coupons comprising 90 potential hole-hole failure points with 250 μm spacing were fabricated and subjected to accelerated CAF test for 600 h in 85 °C, 87% RH. Surface insulation resistance measurements were performed to monitor coupons' condition. Time to failure of examined samples, microscopic inspection results and failure root-cause analysis are presented.

Optimizing Native Ion Mobility Q-TOF in Helium and Nitrogen for Very Fragile Noncovalent Structures

The amount of internal energy imparted to the ions prior to the ion mobility cell influences the ion structure and thus the collision cross section. Non-covalent complexes with few internal degrees of freedom and/or high charge densities are particularly sensitive to collisional activation. Here, we investigated the effects of virtually all tuning parameters of the Agilent 6560 IM-Q-TOF on the arrival time distributions of ubiquitin7+ and found conditions in which the native state prevails. We discuss the effects of solvent evaporation conditions in the source, of the entire pre-IM DC voltage gradient, of the funnel RF amplitudes. We also report on ubiquitin7+ conformations in different solvents, including native supercharging conditions. Collision-induced unfolding (CIU) can be conveniently provoked either behind the source capillary or in the trapping funnel. The softness of the instrumental conditions behind the mobility cell was further optimized with the DNA G-quadruplex [(dG4T4G4)2·(NH4+)3-8H]5-, for which ion activation results in ammonia loss. To reduce the ion internal energy and obtain the intact 3-NH4+ complex, we reduce the post-IM voltage gradient, but this results in a lower IM resolving power due to increased diffusion behind the drift tube. The article describes the various trade-offs between ion activation, ion transmission, and ion mobility performance for native MS of very fragile structures. Graphical Abstract ᅟ.

Remediation of Contaminated Soil with Petroleum Industrial Wastewater

The contamination of soil with the wastes of oil industry products that are complex mixtures of hydrocarbons increased recently due to the large development of oil industries in Iraq. This study deals with the remediation of low permeability contaminated clayey soil by using the enhanced electrokinetic technique (EK). The contaminated soil samples obtained from Thi-Qar oil refinery plant in Al-Nassyriah city, where the byproducts of refinery plant are disposed into that site. The byproduct contaminant treated as total petroleum hydrocarbons (TPH) to avoid dealing and complexity of treating the individual minerals and compounds consisting the contaminant. The initial concentrations of TPH were (702.7, 1168, 1235) ppm in the contaminated soil samples NA10, NA11, and NA12 respectively. The remediation technique includes a bench-scale experimental study by applying the enhanced electrokinetic test on the soil sample NA12 that contains the higher concentration of TPH in compared with other soil samples. A constant DC voltage gradient of 1.0 VDC/cm was applied for a period of 10 days. This echnology was enhanced by using flushing solution of ethanol and deionized water, which was mixed in ratios of 30% and 70% respectively. The results of this study showed that the removal of TPH at the anode was about 15% and the concentration of TPH decreased at anode, which reflect the migration of TPH towards the cathode.

Enhancement Solution to Improve Remediation of Soil Contaminated with Lead by Electrical Field

A laboratory investigation of six different tests were conducted on silty clay soil spiked with lead in concentrations of 1500 mg/kg. A constant DC voltage gradient of 1 V/cm was applied for all these tests with duration of 7 days remediation process for each test. Different purging solutions and addition configurations, i.e. injection wells, were investigated experimentally to enhance the removal of lead from Iraqi soil during electro-kinetic remediation process. The experimental results showed that the overall removal efficiency of lead for tests conducted with distilled water, 0.1 M acetic acid, 0.2 M EDTA and 1 M ammonium citrate as the purging solutions were equal to 18 %, 37 %, 42 %, and 29 %, respectively. However, introducing the injection wells as another enhancement technique into the tests used the same purging solutions mentioned above which have vital role in increasing the removal efficiency up to 59 %.
 

Effect of Alternative Electrolytes on Enhanced Electrokinetic Remediation of Hexavalent Chromium in Clayey Soil

Hexavalent chromium is mobile and hazardous in the environment. Electrokinetic remediationof chromium (IV)-contaminated soils is intended either to remove or to reduce Cr (VI) to Cr (III). This studyexamines the effectiveness of utilizing EDTA and acetic acid solutions as alternative electrolytes in theelectrokinetic (EK) process, with coupled nano-scale zero-valent iron (nZVI) as a barrier for the remediationof Cr (VI)-contaminated clay. An nZVI barrier was installed adjacent to the anode, and different electrolytesolutions (0.1 M EDTA and 1 M acetic acid) were used to investigate the effect of both on the electrokineticremediation efficiency. Soil was contaminated to 300 ppm of Cr (IV), and a constant DC voltage gradient of1 V/cm was applied to the soil sample for 72 h. It was found that an nZVI permeable reactive barrier (PRB)could improve the Cr (VI) remediation efficiency and reduce electrical energy consumption. Results alsoshowed that acetic acid as electrolyte promoted the reduction of Cr (VI) to Cr (III), while EDTA applicationas electrolyte led to more chromium removal and reduction than an EK-nZVI barrier.

Pulsed electrokinetic removal of Cd and Zn from fine-grained soil

Pulsed electrokinetics studies were carried out to optimize the removal of Zn and Cd from fine-grained soils and to observe the effects of varying the pulse frequency, pulse time ratio (on/off), and DC voltage gradient. Existing forms of heavy metals in the soil matrix were determined using a sequential extraction method. The strongly bound fraction (bound to organic matter and residuals) that is difficult to remove from the soil matrix comprised 74 and 62% of the total Zn and Cd, respectively. In the electrokinetic remediation experiments, MgSO4 was employed to increase the ionic strength of the soil for 2 weeks. Transportation of heavy metals was influenced by the frequency, pulse ratio, and the voltage gradient of the pulsed electric field. Extraction efficiency of Zn and Cd near the anode was correlated positively with the voltage gradient at a given pulse and ratio. A high pulse frequency (1,800 cycles/h) enhanced the removal efficiency of the heavy metals compared to a low pulse frequency (1,200 cycles/h) at a supplied voltage gradient of 1 V/cm. Although pulsed electrokinetics was more effective in extracting and desorbing ions near the anode than conventional electrokinetics, its ability to transport heavy metals from the anode to the cathode was relatively small. Total removals with pulsed electrokinetics were 21–31% for Zn and 18–24% for Cd. In summary, pulsed electrokinetics can enhance removal efficiency of heavy metals and is beneficial with regard to electrical energy consumption.

Construction of a hybrid quadrupole/fourier transform ion cyclotron resonance mass spectrometer for versatile MS/MS above 10 kDa

Technological advancements including an open-cylindrical Penning trap with capacitively coupled ICR cell, selective ion accumulation with a resolving quadrupole, and a voltage gradient used during ion extraction from an octopole ion trap, have individually improved dynamic range and sensitivity in Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS). Documented here is a new instrument utilizing these technologies toward the robust detection and fragmentation of biomolecules >10 kDa. Up to 55-fold enhancement in ion population by selective ion accumulation combined with 10- to 20- fold signal-to-noise improvement by application of a DC voltage gradient to an accumulation octopole during the ion transfer event offers improved signal-to-noise (or speed) of MS/MS experiments, for proteins from Methanococcus jannaschii and Saccharomyces cerevisiae whole cell lysates. After external quadrupole filtering with a 40 m/ z window, three proteins were fragmented (and identified) in parallel from the database of Methanococcus jannaschii. Electron capture dissociation (ECD) of an intact yeast protein provides extensive sequence information resulting in a high degree of localization for an N-terminal acetylation. Hybrid fragmentation, infrared multiphoton dissociation (IRMPD) followed by low energy electrons (ECD), with the electron source located laterally off the z-axis and external to the magnet bore, presents a strategy for identification of proteins by means of the sequence tag approach. Automated implementation of diverse MS n approaches in a Q-FTMS instrument promises to help realize “top-down” proteomics in the future.

Sequentially Enhanced Electrokinetic Remediation of Heavy Metals in Low Buffering Clayey Soils

This paper presents the results of an experimental investigation undertaken to evaluate different purging solutions to enhance the removal of multiple heavy metals, particularly chromium, nickel, and cadmium, from a low buffering clay, specifically kaolin, during electrokinetic remediation. Experiments were conducted on kaolin spiked with Cr(VI), Ni(II), and Cd(II) in concentrations of 1,000, 500, and 250 mg/kg, respectively, which simulate typical electroplating waste contamination. A total of five different tests were performed to investigate the effect of different electrode purging solutions on the electrokinetic remedial efficiency. A constant DC voltage gradient of 1 V/cm was applied for all the tests. The removal of heavy metals from the soil using tap water as the purging solution was very low. When 1 M acetic acid was used as the purging solution in the cathode, the removal of chromium, nickel, and cadmium was increased to 20, 19, and 13%, respectively. Using 0.1 M ethylene diamine tetraacetic acid as the purging solution in the cathode, 83% of the initial Cr was removed; however, the nickel and cadmium removal was very low. A sequentially enhanced electrokinetic remediation approach involving the use of water as a purging solution at both the anode and cathode initially, followed by the use of acetic acid as the cathode purging solution and a NaOH alkaline solution as the anode purging solution was tested. This sequential approach resulted in a maximum removal of chromium, nickel, and cadmium of 68–71, 71–73, and 87–94%, respectively. This study shows that the sequential use of appropriate electrode purging solutions, rather than a single electrode purging solution, is necessary to remediate multiple heavy metals in soils using electrokinetics.

Electrokinetic remediation of clayey soils containing copper(II)-oxinate using humic acid as a surfactant

The utility of humic acid (HA) as a surfactant for use in the electrokinetic remediation (ER) of the clayey soils containing copper(II)-oxinate (Cu(OX) 2) was examined. A small simulator of ER was devised, which consisted of three types of artificial soils on the basis of the commercial kaolin: kaolin, kaolin + HA and kaolin + Cu(OX) 2. The layers of kaolin containing HA and Cu(OX) 2 were sandwiched between two kaolin layers. In all experiments, a constant dc voltage gradient of 2.2 V/cm was applied through the soil for 30 h, and the pH of the solution in the anodic chamber was maintained at 7.0. Generally, HA has a negative charge at a neutral pH. However, the HA was mainly transferred to the cathodic chamber. This shows that the driving force of the HA in the system used herein is predominantly due to electroosmotic flow. Moreover, the amount of Cu(OX) 2 removed from the clayey soils in the presence of HA was three times larger than those in the absence of HA. This can be attributed to the fact that the water solubility of Cu(OX) 2 is enhanced by the presence of HA. Thus, we conclude that HA has a potential for use as an amendment for the ER of hydrophobic chemicals, such as Cu(OX) 2.

Using the direct current voltage gradient technology as a quality control tool during construction of new pipelines

External coatings on buried pipelines offer the first line of defence against corrosion with cathodic protection systems in place to protect bare metal at coating defects. Holiday detection, before pipelaying, does not guarantee pipelines are without coating defects after pipelaying. The coating is more than likely to be damaged during pipe construction. The DC voltage gradient (DCVG) method, to locate coating defects on underground pipelines, was initially used for rehabilitation of older pipelines. This technique is now increasingly gaining popularity as a good quality control tool when used on newly laid pipelines to detect coating damage, most of which could be attributed to construction work. On a recently built 50 km long gas pipeline coated with fusion bonded epoxy (FBE), it was proved that more than 80% of defects located after pipelaying were due to mechanical damage during construction. The factory related defects seen were in the form of pinholes or pimples most of which could not be seen by the naked eye and relied on holiday detection for identification.

The Responses of Mammalian Spinal Axons to an Applied DC Voltage Gradient

We have imposed a steady, rostrally negative, weak (ca 0.4 mV/mm) voltage gradient across transections of ascending white matter tracts in the adult guinea pig using an implanted stimulator and electrodes for about 1 month. We have evaluated the projections of these axons relative to the transection approximately 2 months postinjury by anterograde transport of injected tetramethylrhodamine-conjugated dextran and the use of an indwelling marker device which locates the plane of the original transection. Tract tracing was accomplished with conventional epifluorescence microscopy and confocal laser microscopy. Sham-treated control spinal cords contained well-filled lateral and dorsal column ascending tracts terminating caudal to the lesion which formed at the level of the hemisection. Electric field-treated spinal cords contained similarly labeled columns of axons that penetrated the lesion within the caudal segment of the spinal cord, branched within it, and in some cases such branches projected across the plane of transection. Ascending axons also passed around the lesion through undamaged parenchyma, branched repeatedly at the plane of the hemisection, and passed into the rostral segment of the spinal cord. Spear-shaped endings typical of growth cones were found at the terminals of these processes which often branched again within the rostral segment. Centrally projecting fibers, their processes, and the overall level of branching in these projections was not observed in our previous studies using high molecular weight horseradish peroxidase tracers.

Vacuum flashover on diamond-like carbon-coated insulators

Thin coatings of diamond-like carbon (DLC) were applied to cylindrical alumina and high temperature polyimide insulator samples. The coated insulators and uncoated controls were tested for resistance to surface flashover in vacuum under a dc voltage gradient. The DLC-coated insulators had significantly higher flashover potential than the controls and showed no visible tracking on their surface, even after multiple discharges. DLC coatings, applied at temperatures <350/spl deg/C, show promise for improving the performance of HV vacuum feedthroughs, switches, and in other applications.

Study of use of ultrasound technology to prepare polymer-impregnated concrete

Low intensity ultrasound waves (20 kHz, 0.19 to 0.57 W/cm 2 based on concrete area) have been applied to enhance the efficiency of impregnating a monomer into hardened concrete, without prior drying, for subsequent in situ polymerization. It was found that methyl methacrylate could be impregnated into partly air-dried Portland cement concrete, without removing the free water in the specimen, to approximately 80 percent of the depth of that into a similar, previously oven-dried specimen. A systematic study has been carried out to assess the relationship between impregnation depth and the following parameters: ultrasound energy density, impregnation time, gap distance between the ultrasound horn and the specimen surface, and the applied DC voltage gradient. The results of the experiments and a proposed mechanism for the ultrasound enhancement are presented in this paper.

Phase focusing in linear-beam devices

The phenomenon of phase focusing in linear-beam devices is investigated theoretically by modifying the nonlinear interaction equations for devices such as the traveling-wave amplifier (TWA) to accommodate spatially-varying parameters and then investigating their use under a variety of operating conditions. Phase focusing can be accomplished either by tapering the RF circuit phase velocity or by applying a dc voltage gradient along the beam or structure. Both approximate analytical solutions and general computer solutions are presented for each of the phase-focusing techniques. The analytic solutions yield profiles which are explicit functions of tube length and these are compared with more general computer solutions where space-charge effects are included. An experimental S-band high-power TWA was constructed with a variable-pitch helix designed on the basis of the hard-kernel-bunch theory. Experimental data indicate an efficiency improvement from 18 per cent to 35 per cent and an improvement in the gain-frequency characteristics.