• Clean Technology
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• v.16 no.2
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• pp.145-152
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• 2010

Various technical methods are applied for removing water from the water-retaining media, and the energy efficiency is the main concern in those methods. The electroosmotic process is studied as an efficient way for dewatering. An experimental electroosmotic reactor is designed and used for evaluating the effects of operational variables. The operational variables such as the electrical fields and the structure of water-retaining medias were studied. Three different shapes of polarized electric fields in ranges of 0-100 V/cm and 0-10 kHz are used as the source of electric voltage. The effect of electroosmotic process with respect to the structural variation is estimated by filling the electroosmotic reactor with the glass beads in 0.18 mm, 0.35 mm and 1.2 mm in diameters. 6% of water removal is obtained in the simulating electroosmotic reactor of glass beads. The estimated energy consumption in the simulating electroosmotic was 330~490 cal/g-water.

• Applied Chemistry for Engineering
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• v.34 no.3
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• pp.272-278
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• 2023

In this study, we analyzed the effects of current density and electroosmotic phenomena on the desalination performance of electrodialysis (ED). We conducted ED experiments under constant voltage conditions, changing the concentration of the concentrate solution from 10 to 200 g/L. During the ED operation, we measured the current density and charge supplied to the stack, the concentration of the diluted and concentrated solutions, and the amount of water transported by electroosmosis to analyze desalination performance. As the concentration of the concentrated solution increased, the selectivity of the ion exchange membrane decreased, resulting in a decrease in current efficiency. Moreover, the current efficiency was found to be influenced by the current density supplied. When the current density exceeded 15 mA/cm², back diffusion of ions was suppressed, leading to an increase in current efficiency. We also investigated the specific water transport by electroosmosis during the ED operation. We found that the amount of water transported increased proportionally to the concentration ratio of the concentrated and diluted solutions. When the concentration ratio exceeded 100, the specific water transport rapidly increased due to osmotic pressure, making it challenging to obtain a concentrated solution greater than 200 g/L.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.10a
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• pp.153-155
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• 1998

PTFE 합성공정에서 대량으로 사용하는 고가의 음이온계 유화제를 분리/회수하는 것은 경제적인 문제 뿐만 아니라 환경적으로도 매우 중요하다. 음이온계 유화제의 회수에는 Water-evaporation, ion-exchange, freezing, electrodialysis등의 방법을 사용할 수 있다. 그러나 회수에 드는 경비가 높고 장치가 복잡하다는 단점이 잇다. 반\ulcorner에 막분리 공정은 장치가 간단하고 상대적으로 경비가 적게 든다는 장점이 있다. 본 연구에서는 음이온계 유화제를 분리/회수하기 위해서 역삼투 공정을 사용하였다. 그러나 역삼투 공정과 같이 압력을 분리의 구동력으로 하는 막분리 공정에서는 농도분극 및 막오염 현상에 의한 투과량의 감소가 심각하게 일어나며 전체적으로 막분리 공정의 경제성을 떨어뜨리는 주된 요인이 된다. 특히 이온성 막을 사용할 경우 막과 이온성 용질간의 정전기적 포텐셜이 화학적 포텐셜과 함께 투과분리의 구동력을 이루게 되므로 투과거동이 매우 달라지게 된다. 본 연구에서는 막 재료의 이온특성과 음이온성 용질의 농도에 따른 막오염 현상의 관찰 및 이것이 투과거동에 미치는 영향을 관찰하였다. 이를 위해 Sodium alginate, Chitosan, Poly(vinyl alcohol)을 이용하여 각각 음이온성, 양이온성, 중성 막을 제조하여 투과거동을 관찰하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6B
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• pp.661-667
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• 2006

In this study, an experiment of sewage sludge dewatering is carried by using electrokinetic method, and the electrokinetic dewatering efficiency of digested sludge is analyzed. Digested sludge without coagulants is selected and gravitational and pressing dewatering methods are applied in combination with electro-osmotic and electro-osmotic pulse technology. After the test of digested sludge, dewatering test of thickened sludge is carried to evaluate the electrokinetic dewatering feasibility of thickened sludge. Under the condition of constantly applied voltage, however, electrical resistance increases with decreasing of water content so that dewatering rate decreases with time. To reduce such a hindrance caused by constantly applied voltage, electro-osmotic pulse technology which is considered to reduce the difference of water content with height, is applied. For the application of electro-osmotic pulse, the dewatered flow rate and the dewatered volume became more increasing from the middle of the dewatering process than that of continuous voltage. Through the test of thickened sludge, electro-osmotic dewatering combined with gravitational and expression also showed high dewatering rate, which proved the possibility of using electrokinetic dewatering.

• Korean Chemical Engineering Research
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• v.56 no.5
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• pp.679-686
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• 2018

Reverse osmosis (RO) concentration of sodium chloride, sodium acetate, and sodium citrate solutions has been performed by polyamide RO membrane. Concentration polarization phenomena was also studied by changing pressure, solute kinds, and initial solution concentration. Pressure effect on permeation flux was that the increase of flux was accompanied by the increase of pressure. Flux increase was observed by the decrease of initial solution concentration. Surface concentration on the RO membrane increases and so flux declines due to the concentration polarization. In the later phase of concentration, concentration polarization effect was decreased by the back diffusion of solute from the polariztion layer. In case of sodium citrate, its large ion size and charge density resulted in the discrepancy between theory and experimental data of concentration polarization. It may be due to electric repulsion on the membrane surface.

• Membrane Journal
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• v.11 no.1
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• pp.22-28
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• 2001

Various charged homogeneous membranes were fabricated by blending of ionic polymer with a non-ionic polymer with different ratios. In this study. sodium alginate, chitosan and poly(vinyl alcohol) were employed as anionic. cationic and non-ionic polymers, respectively. The permcation and separation behaviors of aquCOll::; salt solutions have been investigated through the charged membranes. As the content of ionic polymer increases in the membrane, the hydrophilicity of the membrane increases and pure water flux as well as solution flux increases correspondingly, indicating that the permeation performance through the membrane is cletemunecl mainly by its hydrophilicity-, Electrostatic interaction between the charged membrane and ionic solute molecules, that is. Donnan exclusion was observed to be attributed to salt rejection to a great deal of extent, and molecular sieve mechanism was effective [or the separation of the salt solution under a similar electrostatic circumstance of solutes.

• Journal of Soil and Groundwater Environment
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• v.10 no.5
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• pp.11-17
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• 2005

Characteristics of phenanthrene removal in the Electrokinetic (EK)-Fenton process were investigated in a 2-dimensional test cell in a viewpoint of the effect of gravity and electrosmotic flow (EOF). When the constant voltage of 100 V was applied to this system, the current decreased from 1,000 to 290 mA after 28 days, because soil resistance increased due to the exhaustion of ions in soil by electroosmosis and electromigration. Accumulated EOF in two cathode reservoirs was 10.3 L and the EOF rate was kept constant for 28 days. At the end of operation, the concentration of phenanthrene was observed to be very low near the anode and increased in the cathode region because hydrogen peroxide was supplied from anode to cathode region following the direction of EOP. Additionally, the concentration of phenanthrene decreased at the bottom of the test cell because the electrolyte solution containing hydrogen peroxide was largely transported toward the bottom due to a low capillary action in the soil with high porosity. Average removal efficiency of phenanthrene by EK-Fenton process was 81.4% for 28 days. In-situ EK-Fenton process would overcome the limitations of conventional remediation technologies and effectively remediate the contaminated sites.

• Membrane Journal
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• v.26 no.4
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• pp.273-280
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• 2016

Pressure assisted forward osmosis (PAFO) is recently introduced because of its improved process efficiency to overcome drawbacks of forward osmosis (FO) such as low water flux and reverse solute diffusion. However, it is known that membrane fouling becomes deteriorated by additional hydraulic pressure applied in PAFO compared to FO. This study was performed to investigate possibility of intermittent pressure-assisted forward osmosis (I-PAFO) operation for fouling mitigation using colloidal silica particles as model foulants. FO, PAFO were operated as well to compare with. Two different solution pH conditions (pH 3, 10) were applied to see the effect of electrostatic interactions between the membrane and silica particles on fouling tendency. In the results, higher water flux was observed during pressurization and pressure relaxation periods in I-PAFO than water flux of PAFO, and FO on both pH conditions. Water flux decreased less in I-PAFO than PAFO after fouling. It resulted in higher water flux recovery in I-PAFO than PAFO after physical cleaning.

• Transactions of the KSME C: Technology and Education
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• v.1 no.1
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• pp.69-73
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• 2013

This study is about the secondary concentration technology using electrodialysis process for minimum discharge and maximize recovery ratio from seawater desalination by reverse osmosis process. The experimental method adopted the constant voltage driving method and, concentrated/desalination volume capacity ratio changes, voltage changes and electrolyte types. Multi-ion membrane is used, aiming to derive conditions to minimize the TDS concentration of desalination water, to minimize the volumes of secnodary concentraion water and minimizing the power efficiency. The results of this study are as follows. The optimal ratio of concentraion/desalination volume is 1:5, the final TDS concentration of desalinated water is 5.32g/l, the final secnodary concentrated water salinity is 17.07% and electric energy demands of desalinated water is $16.74kWh/m^3$.

• Journal of computational fluids engineering
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• v.11 no.3 s.34
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• pp.46-51
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• 2006

This paper presents the numerical results of fluid flow and mixing in a microfluidic device for electro-osmotic flow (EOF) with an trapezoidal electrode array on the bottom wall (ETZEA). Differently from previous EOF in a channel which only transports fluid in colloidal system. ETZEA can also be utilized to mix a target liquid with a reagent. In this study we propose a method of controlling fluid flow and mixing enhancement. To obtain the flow and mixing characteristics, numerical computations are performed by using a commercial code, CFX-10, and a self-made code LBM-D. It was found that the flow near the trapezoidal electrode in the ETZEA is of 3-D complex flows due to the zeta potential difference between the trapezoidal electrode and channel walls, and as a consequence the hetrogeneous zeta potential on the electrodes plays an important role in mixing the liquid.