높은 안전성과 견고한 기계적 특성을 가진 고체상 슈퍼커패시터는 차세대 에너지 저장 장치로서 세계적 관심을 끌고 있다. 슈퍼커패시터의 전극으로서 경제적인 탄소 기반 전극이 많이 사용되는데 수계 전해질을 도입하는 경우 소수성 표 면을 가진 탄소 기반 전극과의 계면 상호성이 좋지 않아 저항이 증가한다. 이와 관련하여 본 연구에서는 전극 표면에 산소 플라즈마 처리를 하여 친수화된 전극과 수계 전해질 사이의 향상된 계면 성질을 기반으로 더 높은 전기화학적 성능을 얻는 방법을 제시한다. 풍부해진 산소 작용기들로 인한 표면 친수화 효과는 접촉각 측정을 통해 확인하였으며, 전력과 지속시간을 조절함으로써 친수화 정도를 손쉽게 조절할 수 있음을 확인하였다. 수계 전해질로 PVA/H3PO4 고체상 고분자 전해질막을 사 용하였으며 프레싱하여 전극에 도입하였다. 15 W의 낮은 전력으로 5초간 산소 플라즈마 처리를 시행하는 것이 최적 조건이 었으며 슈퍼커패시터의 에너지 밀도가 약 8% 증가하였다.

The removal of organic carbon and nutrients (i.e. N and P) from wastewater is essential for the protection of the water environment. Especially, nitrogen compounds cause eutrophication in the water environment, resulting in bad water quality. Conventional nitrogen removal systems require high aeration costs and additional organic carbon. Microbial electrochemical system (MES) is a sustainable environmental system that treats wastewater and produces energy or valuable chemicals by using microbial electrochemical reaction. Innovative and cost-effective nitrogen removal is feasible by using MESs and increasing attention has been given to the MES development. In this review, recent trends of MESs for nitrogen removal and their mechanism were conclusively reviewed and future research outlooks were also introduced.

전기화학적 처리를 통해 합성폐수 내의 질산성 질소, 인을 제거하는 새로운 폐수처리 공정 시스템 개발을 위한 연구를 수행하였다. 전류밀도에 따른 제거율은 전류밀도가 높아질수록 질산성 질소의 높은 제거효율을 얻었고, 전극 스위칭시간에 따른 N03-제거율은 스위칭 간격이 1 min일 때 높은 질산성 질소 제거효율을 얻었다. 전류밀도에 따른 총인 제거율은 전류밀도와 간격의 변화에 크게 영향을 받지 않으면서 90%이상 처리되는 것으로 나타났고, 스위칭시간(1 min간격)의 증가에 따른 총인 제거율은 증가 한 것으로 나타났다. 반면 COD의 경우는 전기화학적 처리를 통해서는 처리되지 않는 것으로 나타났으며 오히려 전극이 용출되면서 증가하는 결과를 얻었다. 또한, 전극의 소모율은 스위칭 간격이 짧을수록 적은 것으로 나타났다. 최종적으로 전기화학적 처리(전류밀도 50 mA/cm2, 스위칭 간격 1 min, 유량 540 mL/min)를 통해 질소 98.1%, 인 90% 이상의 제거 효율을 얻을 수 있었다.

Volatile organic compounds(VOCs) are toxic carcinogenic compounds found in wastewater. VOCs require rapid removal because they are easily volatilized during wastewater treatment. Electrochemical advanced oxidation processes(EAOPs) are considered efficient for VOC removal, based on their fast and versatile anodic electrochemical oxidation of pollutants. Many studies have reported the efficiency of removal of various types of pollutants using different anodes, but few studies have examined volatilization of VOCs during EAOPs. This study examined the removal efficiency for VOCs (chloroform, benzene, trichloroethylene and toluene) by oxidization and volatilization under a static stirred, aerated condition and an EAOP to compare the volatility of each compound. The removal efficiency of the optimum anode was determined by comparing the smallest volatilization ratio and the largest oxidization ratio for four different dimensionally stable anodes(DSA): Pt/Ti, IrO2/Ti, IrO2/Ti, and IrO2-Ru-Pd/Ti. EAOP was operated under same current density (25 mA/cm2) and electrolyte concentration (0.05 M, as NaCl). The high volatility of the VOCs resulted in removal of more than 90% within 30 min under aerated conditions. For EAOP, the IrO2-Ru/Ti anode exhibited the highest VOC removal efficiency, at over 98% in 1 h, and the lowest VOC volatilization (less than 5%). Chloroform was the most recalcitrant VOC due to its high volatility and chemical stability, but it was oxidized 99.2% by IrO2-Ru/Ti, 90.2% by IrO2-Ru-Pd/Ti, 78% by IrO2/Ti, and 75.4% by Pt/Ti anodes The oxidation and volatilization ratios of the VOCs indicate that the IrO2-Ru/Ti anode has superior electrochemical properties for VOC treatment due to its rapid oxidation process and its prevention of bubbling and volatilization of VOCs.

Indirect oxidation using chlorine species oxidizing agents is often effective in wastewater treatment using an electrochemical oxidation process. When chlorine ions are contained in the wastewater, oxidizing agents of various chlorine species are produced during electrolysis. In a ballast water management system, it is also used to treat ballast water by electrolyzing seawater to produce a chlorine species oxidizer. However, ballast water in the brackish zone and some wastewater has a low chlorine ion concentration. Therefore, it is necessary to study the chlorine generation current efficiency at various chlorine concentration conditions. In this study, the chlorine generating current efficiency of a boron-doped diamond(BDD) electrode and insoluble electrodes are compared with various chloride ion concentrations. The results of this study show that the current efficiency of the BDD electrode is better than that of the insoluble electrodes. The chlorine generation current efficiency is better in the order of BDD, MMO(mixed metal oxide), Ti/RuO2, and Ti/IrO2 electrodes. In particular, when the concentration of sodium chloride is 10 g/L or less, the current efficiency of the BDD electrode is excellent.

전해정련을 이용한 폐 피복관 처리의 타당성을 살펴보기 위하여, 500℃의 LiCl-KCl 용융염 내에서 표면이 산화된 10 g 규모의Zircaloy-4 피복관 및 순수한 Zircaloy-4 피복관의 전기화학적 거동을 살펴보았다. 산화된 Zircaloy-4 피복관이 담긴 basket을 작업전극으로하여 전압-전류 관계를 측정한 결과, 산화되지 않은 Zircaloy-4 피복관과 비교해 Zr의 산화 peak는 Ag/AgCl 기준전극 대비, 약 -0.7 V ~ -0.8 V로 유사한 반면, 산화 전류의 크기는 확연하게 감소하는 것으로 나타난다. 이러한 결과는 -0.78V의 일정전위를 가한 전기화학적 용해 실험에서 살펴본 전류-시간 곡선에서도 유사하게 나타나며, 피복관 조각들의 평균 두께 및 무게 변화로부터 확인할 수 있다. Zircaloy-4 피복관이 산화되었을 경우, 표면의 산화막이 피복관의 전도성에 영향을 주어 basket 내 위치에 따라 전기화학적 용해의 균일성 및 속도를 떨어뜨리는 것으로 나타나지만, 표면의 미세한 결함과 Zr 산화물의 상 특성으로 인해 전기화학적 용해가 진행되는 것으로 판단된다.

Boron doped fullerene C60 (B:C60) films were prepared by the thermal evaporation of C60 powder using argon plasma treatment. The morphology and structural characteristics of the thin films were investigated by scanning electron microscope (SEM), Fourier transform infra-red spectroscopy (FTIR) and x-ray photo electron spectroscopy (XPS). The electrochemical application of the boron doped fullerene film as a coating layer for silicon anodes in lithium ion batteries was also investigated. Cyclic voltammetry (CV) measurements were applied to the B:C60 coated silicon electrodes at a scan rate of 0.05 mVs-1. The CV results show that the B:C60 coating layer act as a passivation layer with respect to the insertion and extraction of lithium ions into the silicon film electrode.

The commercial activated carbons are typically prepared by activation from coconut shell char or coal char containing lots of inorganic impurities. They also have pore structure and pore size distribution depending on nanostructure of precursor materials. In this study, two types of commercial activated carbons were applied for EDLC electrode by removing impurities with acid treatments, and controlling pore size distribution and contents of functional group with heat treatment. The effect of the surface functional groups on electrochemical performance of the activated carbon electrodes was investigated. The initial gravimetric and volumetric capacitance of coconut based activated carbon electrode which was acid treated by HNO3 and then heat treated at 800℃ were 90 F/g and 42 F/cc respectively showing 94% of charge-discharge efficiency. Such a good electrochemical performance can be possibly applied to the medium capacitance of EDLC.

The electrochemical oxidation of p-methoxyphenol and hydroquinone for wastewater treatment application was investigated on platinum anode. At the cyclic voltammetry, it was observed that nagative shift of peak potential of p-methoxyphenol and hydroqinone as the pH of electrolytes increases and the peak current showed higher at strong electrolytes than weak electrolytes. In the case of p-methoxyphenol, the optimum electrode potential of controlled potential electrolysis was observed at the potential region of 0.8-1.0 (V vs. SCE) and hydroquinone was showed at the potential of l.0(V vs. SCE). Specially the oxidation rate of p-methoxyphenol and hydroquinone was showed high value in the acid electrolytes.

In this work, we prepared a heterojunction anode with a surface layer of SnO2-Sb-Ni (SSN) on a Ti/IrO2 electrode by thermal decomposition to improve the electrochemical activity of the Ti/IrO2 electrode. The Ti/IrO2-SSN electrode showed significantly improved electrochemical activity compared with Ti/IrO2. For the 0.1 M NaCl and 0.1 M Na2SO4 electrolytes, the onset potential of the Ti/IrO2-SSN electrode shifted in the positive direction by 0.1 VSCE and 0.4 VSCE, respectively. In 2.0-2.5 V voltages, the concentration in Ti/IrO2-SSN was 2.59-214.6 mg/L Cl2, and Ti/IrO2 was 0.55-49.21 mg/L Cl2. Moreover, the generation of the reactive chlorine species and degradation of Eosin-Y increased by 3.79-7.60 times and 1.06-2.15 times compared with that of Ti/IrO2. Among these voltages, the generation of the reactive chlorine species and degradation of Eosin-Y were the most improved at 2.25 V. Accordingly, in the Ti/IrO2-SSN electrode, it can be assumed that the competitive reaction between chlorine ion oxidation and water oxidation is minimized at an applied voltage of 2.25V.

1900년대 초부터 금속 가공 장비의 수명 연장 및 가공물의 품질 향상을 위해 금속 가공 공정에 절삭유가 이용되어 왔다. 금속 가공 특성에 따라 절삭효율 향상을 위해 각종 첨가제를 포함시켜 여러 종류의 절삭유가 제조되고 있으며, 일반적으로 수용성과 비수용성으로 분류된다. 비수용성 절삭유의 경우, 폐유처리과정에서 유독성 물질 발생, 발연･발화 등의 문제로 수용성 절삭유의 사용이 점차 증가해 왔으며, 국내에서 이용되는 절삭유의 60% 이상이 수용성 절삭유이다. 사용된 수용성 절삭유는 비수용성 절삭유와 같이 소각처리 하기에는 비용이 크며, 수계로 유출시 COD 약 30,000~100,000ppm의 고농도 유기성분에 의해 인근 수계를 오염시킬 수 있으므로 각별한 처리가 필요하다. 따라서 본 연구에서는 Ti-IrO2전극을 이용하여 NaCl 첨가, 인가전압 변화를 통해 수용성 절삭유 내 오염물질의 전기화학적 처리에 미치는 영향을 검토하고, 수용성 절삭유의 전기화학적 처리에 대한 기초자료를 제공하고자 한다. 시료는 U사의 W1-1종 수용성 절삭유를 이용하였으며 증류수와 혼합하여 5% 농도의 인공 시료를 제조하였다. 시료의 특성은 Table 1, 실험 조건은 Table 2에 나타내었다.

Generally, metal working fluids (MWFs) are used to reduce friction in metalworking processes. In addition to mineral oils, MWFs contain many chemical substances, such as anticorrosive agents, extreme-pressure additives, and stabilizers, as well as high concentrations of organics and ammonia nitrogen. Accordingly, MWFs must be managed to advanced treatment for hydro-ecological conservation. This study investigated the removal efficiency of ammonia nitrogen from MWFs according to operating time, applied voltage, distance between electrodes, and NaCl concentration using aluminum in a batch-type reactor. The experimental results were as follows: First, without NaCl, removal efficiencies of ammonia nitrogen were 69.6%, 37.9%, and 22.7%, when the distance between electrodes was adjusted to 1, 4, and 7 cm, respectively, at 15 V for 60 min. Secondly, without NaCl, removal efficiencies of ammonia nitrogen were 49.5 and 90.9% when the voltage was adjusted to 5 V and 10 V, respectively, for 60 min and 94.6% at 15 V for 40 min. Lastly, with the addition of NaCl 10 mM, the removal efficiency of ammonia nitrogen was 40.3% and 11.5% greater than that of no addition of NaCl at 5 V for 60 min and at 10 V for 30 min.

An electrochemical treatment has great efficiency for the removal of non-biodegradable material and it has high applicability in wastewater treatment due to its short operating time. The purpose of this study using an electrochemical process is to provide fundamental data on the cutting fluid treatment, which has difficulties in the treatment of nonbiodegradable material. The results are as follows. Experimental data in relation to applied voltage and concentration of NaCl are outlined. With no addition of NaCl, and an applied voltage of 5 V, 10 V, or 15 V for 60 mins, the removal rates of CODMn were 29.87%, 55.32%, and 67.27% for each voltage. The removal rates of CODCr were 39.51%, 70.73%, and 85.37%, respectively. The removal rates of CODMn and CODCr increased with increasing applied voltage. These experimental results showed that the removal rate of COD with varying concentrations of NaCl (0 mM, 5 mM, 10 mM) increased increasing NaCl concentration.

The present study, a modified electrochemical treatment was applied to concrete to mitigate the leaching of alkali ions from concrete. The current ranged 500 mA/m2 and duration was 2weeks. Electrochemical treatment applied in concrete quantity of alkali ions leaching and the limit depth of concrete were decreased, through electrochemical treatment is very high inhibitory effect of the alkali ion is determined leaching.

This paper presents the results of the electrochemical treatment of chemical oxygen demand(COD) and total nitrogen(T-N) compounds in the wastewater generated from flue gas desulfurization process by using a lab-scale electrolyzer. With the increase in the applied current from 0.6 Ah/L to 1.2 Ah/L, the COD removal efficiency rapidly increases from 74.5% to 96%, and the T-N removal efficiency slightly increases from 37.2% to 44.9%. Therefore, it is expected that an electrochemical treatment technique will be able to decrease the amount of chemicals used for reducing the COD and T-N in wastewater of the desulfurization process compared to the conventional chemical treatment technique.

In this study, the inhibitive effect of electrochemical treatment subjected to fresh and hardened concrete and literature reviews in terms of the treatment were performed. In hardened concrete, chloride ions are mixed during casting to destroy the passivity of steel, and then the current was provided for 2 weeks with 250, 500 and 750 mA/m2. After completion of electrochemical treatment, the extraction of chloride ions was quantified and repassivation of steel was observed. Simultaneously, the equated levels of current density for 2 weeks were applied to fresh concrete. Steel-concrete interface in concrete was observed by BSE image analysis and the concrete properties in terms of the diffusivity of chloride ions and the resistance of steel corrosion was measured. As the result, electrochemical treatment is very effectiveness to rehabilitate the passive film on the steel surface and 63-73% of chloride ions in concrete were extracted by the treatment. As the treatment was applied to fresh concrete, the resistance of steel corrosion was improved due to the densification of Ca(OH)2 layers in the vicinity of steel. However, an increase in the current density resulted in an increase in surface chloride content of concrete.

Electrochemical treatments have been applied to many concrete structures. However, excessive current density degrades the bond strength by the change of microstructure at the steel-concrete interface. In this study, the optimal current density of electrochemical treatment without a influence on the bond strength could be derived from related literatures.