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UV Absorbance Ratio Index with Size Exclusion Chromatography (URI-SEC) as an NOM Property Indicator
윤여민(Yeo Min Yoon),허남국(Nam Guk Her),Gary Amy 대한환경공학회 2006 대한환경공학회 학술발표논문집 Vol.2006 No.12
An advanced approach is presented for identifying and characterizing biopolymers of natural organic matter (NOM) in water samples. It involves a simple method based on a ratio of peak heights of high performance size exclusion chromatography (HPSEC) chromatograms based on ultraviolet absorbance (UVA) at 210 nm and 254 nm. The HPSECsystem eliminates inorganic interferences and makes it possible to obtain ratio values associated with organic components as a function of molecular weight (MW). Certain biopolymers show a distinctive ultraviolet absorbance ratio index (URI, UVA(210)/UVA(254)) because they contain different compositional proportions of UV-absorbing functional groups and sp2-hybridized carbon. URI values were found to be the lowest for humic acids (1.59 for a humic acid, highest aromaticity), intermediate for fulvic acids (1.88for a fulvic acid, intermediate aromaticity), and highest for proteins (13.50 for BSA, lowest aromaticity). URI increases with eutrophication of natural waters by the increase of microbially derived components that have a high functional group proportion with a low sp2-hybridized carbon, and increases with ozonation by the cleavage of unsaturated bonds (decrease in unsaturated bonds and increase in functional group proportions).
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Arsenic Removal from Water Using Various Adsorbents
Shahnawaz Sinha,Gary Amy,Yeo Min Yoon,Nam Guk Her 대한환경공학회 2011 Environmental Engineering Research Vol.16 No.3
The equilibrium and kinetic adsorption of arsenic on six different adsorbents were investigated with one synthetic and four natural types (two surface and two ground) of water. The adsorbents tested included magnetic ion exchange resins (MIEX), hydrous ion oxide particles (HIOPs), granular ferric hydroxide (GFH), activated alumina (AA), sulfur modified iron (SMI), and iron oxide-coated microsand (IOC-M), which have different physicochemical properties (shape, charge, surface area, size, and metal content). The results showed that adsorption equilibriums were achieved within a contact period of 20 min. The optimal doses of adsorbents determined for a given equilibrium concentration of Ceq = 10 μg/L were 500 mg/L for AA and GFH, 520-1,300 mg/L for MIEX, 1,200 mg/L for HIOPs, 2,500 mg/L for SMI, and 7,500 mg/L for IOC-M at a contact time of 60 min. At these optimal doses, the rate constants of the adsorbents were 3.9, 2.6, 2.5, 1.9, 1.8, and 1.6 1/hr for HIOPs, AA, GFH, MIEX, SMI, and IOC-M, respectively. The presence of silicate significantly reduced the arsenic removal efficiency of HIOPs, AA, and GFH, presumably due to the decrease in chemical binding affinity of arsenic in the presence of silicate. Additional experiments with natural types of water showed that, with the exception of IOC-M, the adsorbents had lower adsorption capacities in ground water than with surface and deionized water, in which the adsorption capacities decreased by approximately 60-95%.
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주파수 변화 및 보조제 첨가에 따른 나프탈렌 및 페놀의 초음파 분해효율 비교
박종성(Jong Sung Park),허남국(Nam Guk Her) 大韓環境工學會 2010 대한환경공학회지 Vol.32 No.7
최근 초음파를 이용한 유기오염물질의 분해 연구가 진행 중이며, 보다 향상된 초음파 조건을 찾는 연구가 주목을 받고 있다. 본 연구에서는 초음파에 의한 분해 대상물질로 나프탈렌 및 페놀을 선정하여 다양한 주파수(28 kHz, 580 kHz, 1,000 kHz) 및 보조제(TiO₂, H₂O₂, FeSO₄, Zeolite, Cu) 첨가 효과를 비교·분석하여 초음파 처리 시스템의 최적 분해효율 조건을 확인하였다. 주파수 변화에 따른 초음파 분해효율은 나프탈렌과 페놀 모두에서 580 kHz가 가장 우수한 효율을 보였으며, OH 라디칼 역시 동일 주파수에서 가장 많이 발생한 점을 미루어 볼 때, 580 kHz 근처의 초음파 영역에서 최적의 열분해 및 산화분해를 일으킬 수 있는 공동현상 조건이 형성된다는 것을 확인하였다. 100 mg/L의 다양한 보조제를 첨가하여 초음파 분해효율을 비교한 결과 FeSO₄의 분해효율 및 kl값이 무첨가 초음파 반응에 비해 약 1.8배씩 우수하게 조사되었으며, 이것은 초음파와 펜톤 반응이 연계되어 OH 라디칼 생성을 촉진시켜 대상물질의 산화분해를 향상시킨 것으로 판단된다. 그러나 초음파와 펜톤 연계시스템은 배치식 조건에서만 제한적으로 적용 가능할 것이며, 연속식 초음파 시스템에서는 철의 손실, 반옹조의 부식 및 새로운 오염물질을 발생시키는 문제를 야기할 수 있다. 이에 반해 TiO₂를 첨가한 초음파 분해속도가 무첨가 반응보다 약 20%이상 향상된 점을 감안할 때, 초음파와 연계된 연속식 처리 공정에서는 TiO₂가 효과적인 보조제로 사용될 수 있을 것이다. The research seeks to find the optimal conditions for sonodegradation of naphthalene and phenol as exemplary organic pollutants to be subjected to ultrasound in varying frequencies (28 kHz, 580 kHz, and 1,000 kHz) and in the presence of different kinds of additive (TiO₂, H₂O₂, FeSO₄, Zeolite, and Cu). In cases of both naphthalene and phenol, 580 kHz of ultrasound has proven to be the most effective among others at sonodegradation. Based on the observation that OH radicals are also produced in maximum under exposure of 580 kHz of ultrasound, we concluded that this frequency of ultrasound creates hospitable condition for the combined process of degradation by pyrolysis and oxidization. FeSO₄`s degradation rate and k1 value have increased by approximately 1.8 times compared with the results of the solutions without any additives. This seems to be the result of ultrasound reaction which, accompanied by Fenton`s reaction, increased the oxidative degradation and the production of OH radicals. However, application of ultrasound and Fenton`s reaction is limited to the batch type conditions, as its use in continuous system can cause loss of iron or decay of the cistern, thereby creating additional pollutants. When the additive is replaced with TiO₂, on the contrary, the rate of sonodegradation has increased up to 20% compared to when there was no additive. We therefore conclude that TiO₂ could prove to be an effective additive for ultrasound degradation in continuous treatment system.
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