• 대한환경공학회지
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• 제28권11호
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• pp.1162-1167
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• 2006

대형선박에서 적절한 처리없이 배출되는 발라스트수에 의한 해양 생태계의 파괴가 최근 전세계적으로 환경오염 문제로 대두되고 있다. 그 결과, 국제해사기구(IMO)는 공해로 배출되기 전 발라스트수의 적절한 처리를 강제하는 국제협약을 시행할 예정이다. IMO의 발라스트수 처리 기준을 준수하기 위해, 여과, UV 자외선, 오존 처리 등과 같은 몇몇 공정들이 연구되고 있다. 발라스트수의 살균은 매우 짧은 수리학적 체류시간 내에 처리되어야 하기 때문에, 전기화학적 처리 공정은 우수한 공정이 된다. 불용성 전극을 이용한 전기화학적 처리 공정에서 미생물의 살균능은 낮은 pH조건하에 전류밀도와 체류시간이 증가함에 따라 증가하였다. 살균처리 후 미생물의 형상을 전자현미경과 광학현미경으로 관찰하여 전기화학적으로 미생물이 살균된 형태를 확인하였다.

• 한국수소및신에너지학회논문집
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• 제27권4호
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• pp.372-377
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• 2016

The carbon felt used as the electrode of vanadium redox flow battery (VRFB) requires imprived electrochemical activity for better battery performance and efficiencies. Many efforts have been tried to improve electrochemical activity of the carbon felt as electrodes. In this study the alkali solution, KOH, is applied on surface treatment of the carbon felt electrode. The carbon felts were treated with KOH under room temperature and $80^{\circ}C$. The isopropyl alcohol was applied to improve wettability of the carbon felt during KOH treatment. The KOH treated carbon felt was analyzed by using the X-ray photoelectron spectroscopy (XPS). The XPS analysis of carbon felt electrode revealed on increase in the overall surface oxygen content of the carbon felts after KOH treatment. Also, cyclic voltametry tests showed electrochemical characteristics enhancement of the carbon felt.

• 한국표면공학회지
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• 제36권3호
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• pp.277-283
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• 2003

Electrochemical techniques were used to study the surface treatment for improving the pitting corrosion resistance of 304L stainless steel by inhibitors in chloride medium. Sodium molybdate (in concentration range : 0.005-80 g/l) , sodium nitrite (in concentration range : 0.001-50 g/l) and their mixture were used for this study. It was found that, molybdate and nitrite were good passivators for 304L stainless steel, but molybdate was not able to prohibit the pitting ; nitrite prevented pitting corrosion of 304L stainless steel only at the concentration more than 25 g/l. The relationship between pitting potentials and concentrations of inhibitors in the logarithm expression obeyed the linear function. It was found that the surface treatment by mixture of two inhibitors enables stainless steel to have increased the corrosion resistance , the pitting corrosion of 304L stainless steel was completely prohibited by the mixtures of molybdate and nitrite in ratio min, with $m\;\geq\;3\;and\;n\;\geq\;10$. The interesting cases on electrochemical measurement of threshold of inhibitors concentration combination for optimum surface treatment were described.

• Membrane and Water Treatment
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• 제9권3호
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• pp.189-194
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• 2018

Electrochemical reduction of nitrate was studied using Zn, Cu and (Ir+Ru)-Ti cathodes and Pt/Ti anode in a cell divided by an ion exchange membrane. During electrolysis, effects of the different cathode types on operating parameters (i.e., voltage, temperature and pH), nitrate removal efficiency and by-products (i.e., nitrite and ammonia) formation were investigated. Ammonia oxidation rate in the presence of NaCl was also determined using the different ratios of hypochlorous acid to ammonia. The operating parameter values were similar for all types of cathode materials and were maintained relatively constant. Nitrate was well reduced and converted mostly to ammonia using Zn and Cu cathodes. Ammonia, produced as a by-product of nitrate reduction, was oxidized in the presence of NaCl in the electrochemical process and the oxidation performance was enhanced upon increasing the hypochlorous acid-to-ammonia ratio to 1.09:1. Zn and Cu cathodes promoted the nitrate reduction to ammonia and the produced ammonia was finally removed from solution by reacting with hypochlorite ions. Using Zn or Cu cathodes, instead of noble metal cathodes, in the electrochemical process can be an alternative technology for nitrate-containing wastewater treatment.

• 한국건설순환자원학회논문집
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• 제11권2호
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• pp.138-144
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• 2023

본 연구에서는 알칼리 침출수의 수서환경 완화를 위한 전기화학적 처리에 대한 효과를 평가하였다. 시멘트 페이스트의 표면을 개질하기 위해 1,000 mA/m² 의 직류를 양극 graphite를 통해 외부 메쉬로 4주 동안 통전한 후, 물 속의 알칼리 침출이 자연적으로 치유되는 것을 방지하기 위해 시멘트 페이스트 시편을 밀폐된 상태의 정지된 물에 침지시켰다. 물 속에서 100일간의 모니터링 한 결과, 전기화학적 처리를 한 시편의 pH 값은 약간 증가한 반면, control 시편의 pH의 경우 13.2를 나타내어 훨씬 더 높은 pH값을 나타내었다. 또한, pH 모니터링 이후 시멘트 페이스트 시료에 대한 pH 프로파일은 전기화학적 처리가 시멘트 매트릭스의 높은 알칼리도 확보에 효과적임을 알 수 있었다. 알칼리 침출 공정에서 얻은 알칼리침출수는 다프니아 마그나의 생태학적 테스트에 사용되었다. Control 시편은 표준 Daphnia Magna를 대부분 고정시킨 반면, 전기화학적 처리기법의 경우 생태학적으로 매우 우수하다는 것을 확인하였다.

• Journal of Electrochemical Science and Technology
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• 제12권3호
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• pp.339-345
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• 2021

Spent activated carbons (SACs) collected from a water treatment plant were regenerated and then adopted as electrochemical material in capacitors. The SACs used in this study were regenerated via two steps, namely thermal and chemical activation. However, during the activation process, the adsorbates were converted into ashes, which caused pore blockage and decreased specific surface area. The regenerated SACs were washed with acid solutions with different levels of acidity (strong: HCl, mild: H₃PO₄, and weak: H₂O₂) to remove the ashes. The regenerated SACs washed with HCl exhibited the highest specific surface area, although their capacitance was not the highest. Conversely, the specific surface area of regenerated SACs washed using H₃PO₄ was slightly lower than that of HCl, but exhibited higher capacitance and electrochemical stability. Although the strong acid removed the generated ashes in the pores efficiently, it could adversely affect their structural stability, which would lead to lower capacitance.

• Journal of Electrochemical Science and Technology
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• 제15권1호
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• pp.190-197
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• 2024

A commercial PbO₂ mesh cylinder electrode was utilized as the anode for the electrochemical degradation of the textile effluent after the biological treatment with the titanium cylinder as the cathode in a self-made tube electrolyzer. The electrochemical performances of the PbO₂ electrode in tube electrolyzer under different initial pH, electrolyte flow rates, current densities and times of the electrochemical degradation were investigated. The experimental results illustrated that the PbO₂ electrode can reduce the chemical oxygen demand (COD) of the textile effluent from 94.0 mg L^-1 to 65.0 mg L^-1 with the current efficiency of 88.3%, the energy consumption of 27.7 kWh kg^-1 (per kilogram of degraded COD) and the carbon emissions of 18.0 kg CO₂ kg^-1 (per kilogram of degraded COD) under the optimal operating conditions. In addition, the COD of the textile effluent could be reduced from 94.0 mg L^-1 to 22.0 mg L^-1 after the fifth electrochemical degradation. Therefore, PbO₂ mesh cylinder electrode in the tube cylinder was promising for the electrochemical degradation of the textile effluent.

• 한국구조물진단유지관리공학회 논문집
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• 제17권5호
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• pp.67-76
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• 2013

본 연구에서는 전기방식 종류에 따른 문헌 고찰 및 굳지 않은/굳은 상태의 콘크리트에 대해 전기방식 적용 시 방식 효과와 관련하여 연구를 실시하였다. 굳은 콘크리트의 경우 우선적으로 철근의 부동태피막 파괴를 유도하기 위하여 NaCl을 혼입한 후, 2주일동안 250, 500, $750mA/m^2$의 방식전류를 통전하였다. 그 후 부동태피막 복원화와 염소 이온 추출에 대해서 정량화를 실시하였다. 동시에, 굳지 않는 상태의 콘크리트에 대해서는 굳은 상태와 동일한 양의 방식전류를 타설 직후부터 동일한 기간동안 통전하여 전기방식을 실시하였다. 후광산란(Backscattered electron; BSE) 이미지를 이용하여 철근-콘크리트 계면을 관찰하였으며, 염소이온 확산에 대해서 염소이온 이동 속도와 철근 부식 저항성에 대한 콘크리트의 성질 변화에 대해 측정하였다. 결과적으로 보면, 전기 방식은 부동태피막 복원화에 매우 효육적이며, 콘크리트 내의 염소이온 중 63-73% 정도가 추출되는 것으로 확인 되었다. 굳지 않는 상태의 콘크리트에 전기방식을 적용할 경우, 철근 표면에서 $Ca(OH)_2$ 층이 조밀하게 되어 철근 부식 저항성이 향상되었다. 다만, 방식 전류에 따라 콘크리트 표면 염화물량이 증가하는 경향이 나타나는 것을 확인 할 수 있다.

• Journal of Electrochemical Science and Technology
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• 제4권3호
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• pp.113-118
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• 2013

Fluorophosphate, $Na_2MnPO_4F$ as new cathode material was synthesized by carbothermal treatment method. Prepared $Na_2MnPO_4F$ has particle size under 100 nm and residual carbon exists in surface of $Na_2MnPO_4F$. Additional carbon coating was performed in order to increase the electrochemical properties. Even capacity and overpotential were improved by carbon coating using mechanical ball milling, the reduced crystallinity limited the drastic improvement of the electrochemical properties. To solve this problem, re-heat treatment was involved to recover crystallinity and then notable improvement of electrochemical properties was obtained. Specific amount of $Li^+$ that participates in electrochemical $Li^+$ insertion / extraction reaction, was x = 1 in $Li_xNa_{2-x}MnPO_4F$ within the voltage range of 2.0 to 4.8 V. The doubled capacity by 2 electron reaction can be obtained when NMPF is charged to higher voltage over 4.8 V.

• Journal of Electrochemical Science and Technology
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• 제3권1호
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• pp.24-28
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• 2012

The electrocatalytic activities and surface roughness of indium-tin-oxide (ITO) electrodes have been investigated after thermal treatment at 100, 150, or $200^{\circ}C$ for 30 min, 2 h, or 8 h. To check electrocatalytic activities, the electrochemical behavior of four electroactive species (p-hydroquinone, $Ru(NH_3){_6}^{3+}$, ferrocenemethanol, and $Fe(CN){_6}^{4-}$) has been measured. The electron transfer rate for p-hydroquinone oxidation and ferrocenemethanol oxidation increases with increasing the incubation temperature and the incubation period of time, but the rate for $Ru(NH_3){_6}^{3+}$ is similar irrespective of the incubation temperature and period because $Ru(NH_3){_6}^{3+}$ undergoes a fast outer-sphere reaction. Overall, the electrocatalytic activities of ITO electrodes increase with increasing the incubation temperature and period. The surface roughness of ITO electrodes increases with increasing the incubation temperature, and the thermal treatment generates many towering pillars as high as several tens of nanometer.