Electroosmotic dewatering of clays. I. Influence of voltage

Lockhart, N.C.

doi:10.1016/0166-6622(83)80015-8

Cited by 85 publications

(22 citation statements)

References 7 publications

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“…As discussed by Bjerrum et al (1967), excessive current density tends to dry out the soil around the anode very rapidly, thereby disguising the true potential benefit of electrokinetic dewatering. As shown by Nicholls and Herbst (1967) and Lockhart (1983a), electrokinetic dewatering is much more energy efficient at lower voltage gradients. In addition to this benefit, a lower voltage gradient also resulted in a lower pH rise of the drainage water at the cathode (Veal et al 2000;Lockhart 1983a).…”

Section: Voltage Gradient and Current Densitymentioning

confidence: 85%

“…As shown by Nicholls and Herbst (1967) and Lockhart (1983a), electrokinetic dewatering is much more energy efficient at lower voltage gradients. In addition to this benefit, a lower voltage gradient also resulted in a lower pH rise of the drainage water at the cathode (Veal et al 2000;Lockhart 1983a). A lower voltage gradient (or lower current density) has the obvious disadvantage that the rate of dewatering is lower than at a high voltage gradient, although the energy efficiency is better.…”

Section: Voltage Gradient and Current Densitymentioning

confidence: 85%

“…A lower voltage gradient (or lower current density) has the obvious disadvantage that the rate of dewatering is lower than at a high voltage gradient, although the energy efficiency is better. Conditions can be further optimized by starting at a low voltage gradient and gradually increasing it as dewatering proceeds (Lockhart 1983a). The debate over voltage gradient versus current density is not fully resolved, although intuitively current density seems more appropriate, which is supported by the observations of Shang et al (1995).…”

Section: Voltage Gradient and Current Densitymentioning

confidence: 99%

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Dewatering of mine tailings using electrokinetic geosynthetics

Fourie

Johns²,

Jones³

2007

Can. Geotech. J.

111

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Many mining operations produce tailings that dewater very slowly under self-weight consolidation. One way of reducing the water content of such tailings is by electroosmotic dewatering. Although the technique has been used with some success in civil engineering applications, it is still largely seen as a solution of last resort. This is probably due to the high energy costs reported in the literature, as well as problems of very rapid corrosion of metal electrodes. This paper describes a study using newly developed electrokinetic geosynthetics (EKGs) as electrodes for the in situ dewatering of mine tailings. Laboratory tests were undertaken on mineral sands tailings in both a purpose-built testing cell and a laboratory testing tank using EKGs, followed by an outdoor experiment in a tank containing approximately 9 m3 of the tailings. This test was run for over 2 months. Energy consumption in the outdoor test was less than 1 kWh per dry tonne of material dewatered and there was no sign of electrode deterioration even after 2 months of usage. The results point to a potentially powerful technique for reducing the water content of tailings ponds in situ, thus increasing storage space, improving stability, and facilitating closure of these facilities.Key words: tailings, dewatering, electroosmosis, electrokinetic geotextiles, consolidation.

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Section: Voltage Gradient and Current Densitymentioning

confidence: 85%

Section: Voltage Gradient and Current Densitymentioning

confidence: 85%

Section: Voltage Gradient and Current Densitymentioning

confidence: 99%

See 1 more Smart Citation

Dewatering of mine tailings using electrokinetic geosynthetics

Fourie

Johns²,

Jones³

2007

Can. Geotech. J.

111

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“…Aluminum electrodes were adopted due to its availability and common use in previous research. [28][29][30][31] Additional small holes perforated the tubes to discharge water. A layer of silica sand with a thickness of Drying Technology approximately 70 mm, which corresponded to a uniform loading of 1.5 kPa, was spread on the specimens to simulate the combined action of electro-osmosis and loading, as is shown in Fig.…”

Section: Apparatusmentioning

confidence: 99%

Electro-Osmotic Dehydration of Hangzhou Sludge with Selected Electrode Arrangements

et al. 2015

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Electro-osmosis is considered a promising technique for the dehydration of sludge with low permeability and high water content. With little information available on the optimal electrode arrangement for electro-osmosis, comparisons of rectangular, hexagonal and staggered arrays were performed based on laboratory experiments and theoretical analysis. Experimental results identified that favorable electro-osmotic effects were produced by the hexagonal array with regard to drainage, water content and shear strength of treated soils compared to the other two arrays examined; the average coefficient of energy dissipation of the hexagonal array was 39% lower than that of the rectangular array and 53% lower than that of the staggered array. This finding demonstrates that the hexagonal array was less energy consuming. To describe the electro-osmotic efficiency, the effective electric field theory previously proposed was used to calculate proportions of effective field areas; the results shows that the hexagonal array performed best, followed by the rectangular and finally the staggered arrays. It is thus concluded that the hexagonal array was most effective and was thus recommended Drying Technology 2 as the primary pattern for application. The validity of the effective electric field theory in estimating electric field distributions for electro-osmosis was also confirmed by comparing theoretical predictions and experimental results.

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“…The EOD is carried out by applying an electric field between two electrodes submerged in the 'wet clay, either by means of an imposed voltage through an external power supply [I, 81 of by creating a "battery effect" (called the Galvani dewatering) by the proper combination of the anode and 1.he cathode [3]. One may conduct EOD either under continuous IDC or with periodic power interruption, when a DC power supply is used to drive the EOD [8,91.…”

Section: Vijhmentioning

confidence: 99%

The Significance of Current Observed During Combined Field and Pressure Electroosmotic Dewatering of Clays

Vijh

1999

Drying Technology

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CLAYSAshok K. V i h lnstitut de recherche d'Hydro-Quebec (IREQ) 1800 boul. Lionel-Boulet Varennes, QuCbec Canada J3X IS1 Key Words: Combined electroosmotic dewatering: currents in electroosmotic dewatering; electrokinetic effects in terms of irreversible thermodynamics; electrochemical/electrical currents; hydrodynamic currents; electroosmotic currents. ABSTRACTThe nature of current observed during combined field and pressure electroosmotic dewatering of clays is analysed in terms of the phenomenological relations of irreversible thermodynamics. It is shown that the total water removing current consists of three components:(I) electrical current;(2) hydrodynamic current;(3) electroosmotic current.The significance of these currents is quantitatively described and provides the theoretical basis for the extremely high dewatering efficiencies (in terms of litres of water removed per ampere-hour) observed during the electroosmotic dewatering process.Copyrmght 0 1999 by Marcel Dckker. Inc.

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Electroosmotic dewatering of clays. I. Influence of voltage

Cited by 85 publications

References 7 publications

Dewatering of mine tailings using electrokinetic geosynthetics

Dewatering of mine tailings using electrokinetic geosynthetics

Electro-Osmotic Dehydration of Hangzhou Sludge with Selected Electrode Arrangements

The Significance of Current Observed During Combined Field and Pressure Electroosmotic Dewatering of Clays

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