• 미생물학회지
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• 제36권4호
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• pp.279-284
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• 2000

페놀을 유일한 탄소 및 에너지원으로 이용할 수 있는 Rhodococcus sp. CP01을 침출수로부터 분리하고 회분식 및 연속배양 체제에서 크롬(VI)을 동시에 환원시키는 능력을 추정하였다. 크롬(VI) 환원의 최적 pH 7.0과 페놀 농도 1,000 mg/L에서 최소배지에 주어진 0.25 mM의 크롬(VI)은 CP01 균주에 의해 60시간만에 완전히 환원되었으며, 이때 크롬의 환원속도는 4.17 $\mu$M/hr, 페놀의 분해속도는 38.4 mg.$L^{-1}$.$hr^{-1}$로 측정되었다. 수리학적 체류시간을 100hr으로 유지한 호기성 연속배양 체제에서 크롬(VI)의 농도를 0.0625, 0.125, 그리고 0.25 mM로, 페놀 농도를 1,000~4,000 mg/L까지 변화시키면서 46인간 운전한 결과, 크롬(VI) 0.125 mM과 페놀 3,000 mg/L일 때 유사 steady state에 이르렀으며 이때 크롬의 환원율은 거의 100%로 일정하게 유지되었다. 이 구간에서 계산된 specific reduction rate는 0.34 mg Cr(VI).g $protein^{-1}$.$hr^{-1}$로서 glucose를 생장기질로 이용한 기존의 연구 결과와 유사한 수준으로 나타났다. 이상의 결과로부터 본 연구는 중금속 크롬(VI)과 방향족 화합물인 페놀을 동시에 효과적으로 제거할 수 있는 생물학적 처리 가능성을 보여 주었다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2005년도 INTERNATIONAL SYMPOSIUM ON SOIL & GROUNDWATER ENVIRONMENT
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• pp.183-184
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• 2005

• 한국광물학회지
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• 제21권2호
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• pp.161-175
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• 2008

제주도 화산회 기원 토양시료들은 전형적인 안디졸에 해당하는데 낮은 pH, 높은 수분함량, 높은 유기물함량, 식질-미사질 토성을 보여주었다. 결정질 광물 중 현무암 기원의 감람석, 휘석 등의 철고토광물과 자철석 및 적철석 등의 산화철이 주구성광물로 관찰되며 이차광물인 깁사이트가 일부 심토에서 나타나는 것이 특징이다. 그밖에 제주도 화산회 토양은 비정질 알로판 광물과 ferrihydrite 등의 결정도가 낮은 광물을 상당량 포함하고 있다. 주성분원소는 비화산회토양에 비해 상대적으로 낮은 $SiO_2$ 함량과 높은 $A1_2O_3$ 및 $Fe_2O_3$ 함량을 보이는데 이는 전형적인 화산회토의 특성을 반영한다. 토양 내 중금속 함량 중에서 Zn, Ni, Co, Cr은 각자 $84{\sim}198$, $56{\sim}414$, $38{\sim}150$, $132{\sim}1164\;mg\;kg^{-1}$의 범위를 보여 일반적인 세계 토양 내 함량범위를 초과하는 것으로 나타났다. 특히 Cr의 경우 1,000 ppm 이상의 함량을 가지는 토양 시료도 존재하는 등 제주도 화산회 토양은 높은 Cr 함량을 보이는 것이 특징이다. 제주도 토양의 환원능은 평균 $6.53\;mg\;L^{-1}$ reduced Cr(VI)로서 내륙의 비화산회토양에 비해 5.1배 이상 큰 것으로 나타났다. 비화산회토양의 경우 토양 환원능은 토양의 이화학적 인자 중 총 탄소함량과 매우 좋은 상관관계(R = 0.90)를 보이고 있는 것으로 보고되었으나, 총 탄소함량이 일반 토양에 비해 20배 이상 큰 제주도 화산회 토양의 경우 환원능은 탄소함량과는 오히려 약한 음의 상관관계를 보여주고 있다(R = -0.469). 이러한 결과는 제주도 화산회 토양의 환원능을 제어하는 인자가 탄소함량뿐만 아니라 또 다른 토양 이화학성에 있음을 지시한다. 주성분 원소조성과 환원능의 상관관계분석결과 화산회토 특성을 반영하는 Al과 Fe 원소와 정의 상관관계(R = 0.793, R = 0.626)를 보여주었다. 또한 중금속 원소 중 Ni, Co, Cr 등은 제주도 화산회 토양의 환원능과 정의 상관관계(R = 0.538, R = 0.647, R = 0.468)를 보이고 있다. 산화환원전위에 민감한 Cr 원소의 경우 제주도 화산회토양의 높은 환원능으로 인해 유해하고 이동성이 높은 6가 크롬의 생성 및 이동이 매우 제한될 것으로 판단된다. 또한 제주도 화산회 토양의 환원능을 제어하는 인자는 비정질인 알로판 광물 및 ferrihydrite 등의 화산회토 특성과 밀접한 관련이 있는 것으로 판단된다.

• 한국석유지질학회:학술대회논문집
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• 대한자원환경지질학회/한국석유지질학회/한국암석학회 2000년도 추계공동학술발표회 초록집
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• pp.38-38
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• 2000

• Journal of Electrochemical Science and Technology
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• 제11권3호
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• pp.291-309
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• 2020

Chromium was electrodeposited from deep eutectic solvents-based Cr³⁺ electrolytes on HB-pencil graphite electrode. Factors influencing the electrochemical behavior and the processes of Cr nucleation and growth were explored using cyclic voltammetry and chronoamperometry techniques, respectively. Cr³⁺ reduction was found to occur through an irreversible diffusion-controlled step followed by another irreversible one of impure diffusional behaviour. The reduction behavior was found to be greatly affected by Cr³⁺ concentration, temperature, and type of hydrogen bond donor used in deep eutectic solvents (DESs) preparation. A more comprehensive model was suggested and successfully applied to extract a consistent data relevant to Cr nucleation kinetics from the experimental current density transients. The potential, the temperature, and the hydrogen bond donor type were estimated to be critical factors controlling Cr nucleation. The nucleation and growth processes of Cr from either choline chloride/ethylene glycol (EG-DES) or choline chloride/urea (U-DES) deep eutectic solvents were evaluated at 70℃ to be three-dimensional (3D) instantaneous and diffusion-controlled, respectively. However, the kinetics of Cr nucleation from EG-DES was found to be faster than that from U-DES. Cr nucleation was tending to be instantaneous at higher temperature, potential, and Cr³⁺ concentration. Cr nuclei electrodeposited from EG-DES were characterized at different conditions using scanning electron microscope (SEM). SEM images show that high number density of fine spherical nuclei of almost same sizes was nearly obtained at higher temperature and more negative potential. Energy dispersive spectroscopy (EDS) analysis confirms that Cr deposits were obtained.

• 한국환경농학회지
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• 제29권4호
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• pp.402-407
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• 2010

Zerovalent iron (ZVI) is one of the most commonly used metallic reducing agents for the treatment of toxic contaminants in wastewater. Traditional ZVIs are less effective than nanoscale ZVI (nZVI) due to prolonged reaction time. However, the reactivity can be significantly increased by reducing the size of ZVI particles to nanoscale. In this study, nZVI particles were synthesized under laboratory condition and their efficiency in removing hexavalent chromium (Cr(VI)) from aqueous solutions were compared with commercially available ZVI particles. The results showed that the synthesized nZVI particles (SnZVI) reduced >99% of Cr(VI) at the application rate of 0.2% (w/v), while commercial nZVI (CnZVI) particles resulted in 59.6% removal of Cr(VI) at the same application rate. Scanning electron micrographs (SEM) and energy dispersive spectra (EDS) of the nZVI particles revealed the formation of Fe-Cr hydroxide complex after reaction. Overall, the SnZVI particles can be used in treating chromium contaminated wastewater.

• 대한금속재료학회지
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• 제46권10호
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• pp.652-661
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• 2008

Reduction of NOx in emission gas, improvement of engine efficiency, and extension of warranty period has made demands for developing materials more corrosively resistant to the inner-muffler environments or predicting the lifetime of materials used in muffler more precisely. The corrosion inside muffler has been explained with condensate corrosion mainly though thermal oxidation experiences prior to condensate corrosion. Hence, the aim of this study is to describe how the thermal oxidation affects the corrosion of stainless steel exposed to the inner-muffler environments. Auger electron spectroscopy and electrochemical tests were employed to analyze oxide scale and to evaluate corrosion resistance, respectively. Thermal oxidation has different role of condensate corrosion depending on the temperature: inhibiting condensate corrosion below $380^{\circ}C$ and enhancing condensate corrosion above $380^{\circ}C$. The low temperature oxidation causes to form compact oxide layer functioning a barrier for penetrating condensate into a matrix. Although though thermal oxidation caused chromium-depleted layer between oxide layer and matrix, the enhancement of the condensate corrosion in high temperature oxidation resulted from corrosion-induced crevice formed by oxide scale rather than corrosion in chromium-depleted layer. It was proved by aids of anodic polarization tests and measurements of pitting corrosion potentials. By the study, the role of high temperature oxidation layer affecting the condensate corrosion of stainless steels used as muffler materials was well understood.

• Environmental Engineering Research
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• 제23권1호
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• pp.92-98
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• 2018

Suitability of aluminium-based water treatment sludge (WTS), a waste product from water treatment facilities, was assessed for removal of heavy metals from an electroplating wastewater which had high concentrations of copper and chromium along with other heavy metals. Batch tests with simulated wastewater in single- and multi-metal solutions indicated the influence of initial pH and WTS dose on removal of six metals namely Cu(II), Co(II), Cr(VI), Hg(II), Pb(II) and Zn(II). In general, removal of cationic metals such as Pb(II), Cu(II) and Zn(II) increased with increase in pH while that of anionic Cr(VI) showed a reduction with increased pH values. Tests with multi-metal solution showed that the influence of competition was more pronounced at lower WTS dosages. Column test with diluted (100 times) real electroplating wastewater showed complete removal of copper up to 100 bed volumes while chromium removal ranged between 78-92%. Other metals which were present in lower concentrations were also effectively removed. Mass balance for copper and chromium showed that the WTS media had Cu(II) and Cr(VI) sorption capacities of about 1.7 and 3.5 mg/g of dried sludge, respectively. The study thus indicates that WTS has the potential to be used as a filtration/adsorption medium for removal of metals from metal-bearing wastewaters.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 총회 및 춘계학술발표회
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• pp.143-146
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• 2004

Natural zeolites have exhibited high sorption capacity for inorganic cations including heavy metals and ammonium. Moreover, they were proven to be effective for environmental applications such as permeable barriers for controlling the spread of cation-contaminated groundwater. However zeolites have little or no affinity for anionic species like chromium, as they possess a net negative structural charge. To achieve the simultaneous sorption for anionic contaminants, surfactant-modified zeolite (SMZ) has been employed as the possible sorbents. Current study focuses on simultaneous removal of heavy metals having different ionic form in aqueous solution, cadmium (C $d^{2+}$) and chromium (Cr $O_{4}$$^{2-}$), using newly developed materials, ZanF. ZanF, a potential alternative to SMZ, was derived from zeolite modified by Fe(II) chloride followed by reduction with sodium borohydride. Batch experiments were performed to estimate the removal efficiency of ZanF at different conditions. Under different pH ranging from 2 to 6, removal efficiency was investigated. And C $d^{2+}$ removal efficiency was estimated by varying background concentration of Cr $O_{4}$$^{2-}$, and vice versa. With the test results, ZanF was expected to be a possible reactive materials alternative to SMZ in permeable reactive barriers (PRBs) for treating the contaminated groundwater with cationic and anionic heavy metals.als.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2002년도 총회 및 춘계학술발표회
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• pp.58-61
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• 2002

An alternative to pump and treat groundwater remediation is the use of reactive barriers. Zero valent iron (ZVI) is particularly useful as a reductant of chlorinated hydrocarbons because of its low cost and lack of toxicity ZVI can drive the dechlorination of chlorinated organic compounds and the reduction of chromium from the Cr(Ⅵ) to the Cr(III) state. The contaminants in subsurface environment usually exist as the mixed compounds. Therefore, the objective of this research is to study the effect of the other compounds on TCE removal by ZVI. The removal mechanism of TCE by ZVI is separated the dechlorination and sorption. TCE removal by ZVI slightly increased in presence of naphthalene as the non-reduced compound. TCE removal by ZVI remarkable decreased in presence of carbon tetrachloride, nitrate, and chromate as the reduced compounds. This research suggests that the effect of the coexisted compounds on the removal chlorinated compounds by reactive barrier technology should be considered for practical application.