• Advances in environmental research
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• 제9권3호
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• pp.191-214
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• 2020

The rise in population and industrialization accounts for the generation of a huge amount of wastewaters. The treatment of this wastewater is obligatory to safeguard the environment and various life forms. Conventional methods for high strength wastewater treatment coming out to be ineffective. Advanced oxidation processes (AOPs) for such wastewater treatment proved to be very effective particularly for the removal of various refractory compounds present in the wastewater. Ozone based AOPs with its high oxidizing power and excellent disinfectant properties is considered to be an attractive choice for the elimination of a large spectrum of refractory compounds. Furthermore, it enhances the biodegradability of wastewaters after treatment which favors subsequent biological treatments. In this review, a detailed overview of the AOPs (like the Fenton process, photocatalysis, Electrochemical oxidation, wet air oxidation, and Supercritical water oxidation process) has been discussed explicitly focusing on ozone-based AOPs (like O₃, O₃/H₂O₂, O₃/UV, Ozone/Activated carbon process, Ozone/Ultrasound process, O₃/UV/H₂O₂ process). This review also comprises the involved mechanisms and applications of various ozone-based AOPs for effective municipal/industrial wastewaters and landfill leachate treatment. Process limitations and rough economical analysis were also introduced. The conclusive remarks with future research directions also underlined. It was found that ozonation in combination with other effective AOPs and biological methods enhances treatment efficacies. This review will serve as a reference document for the researchers working in the AOPs field particularly focusing on ozone-based AOPs for wastewater treatment and management systems.

• Elastomers and Composites
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• 제52권3호
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• pp.180-186
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• 2017

In this work, the effect of low-temperature dehydration of a poly(styrene-co-styrenesulfonic acid) (PSSA) membrane was investigated by differential scanning calorimetry, fourier transform infrared spectroscopy (FT-IR), electron magnetic resonancespectroscopy (EMR), and $^1H$- and $^{13}C$ solid-state nuclear magnetic resonance spectroscopy. These analyses were performed at room temperature for powdered PSSA specimens with and without dehydration and the following key observations were made. First, FT-IR analysis showed that low-temperature dehydration not only transformed the [${SO_3}^-{\cdots}H^+$] ionic pair in the non-hydrated PSSA to an $SO_3H$ group, but also induced the formation of -C=C- double bonds in the dehydrated PSSA. Second, the ${-SO_3}^{\bullet}$ radical was unambiguously identified by EMR spectroscopy. Third, H-abstraction was detected by $^1H$ magic-angle spinning spectroscopy. Finally, an unexpected color shift from white for the non-hydrated PSSA to a yellowish brown for the dehydrated sample was observed. In order to explain these experimental results, it was proposed that the formation of the intermediate hydrogen ($H^{\bullet}$) or hydroxyl radical ($HO^{\bullet}$) species was initiated by the dehydration process. The sespecies attacked the $SO_3H$ group and the tertiary proton at the ${\alpha}-carbon$, resulting in the formation of $-SO^{\bullet}$ radicals and -C=C- double bonds, which correlated with the color shift in the dehydrated PSSA sample. The semechanisms are useful for understanding the simultaneous loss of an aromatic ring and -SO- groups in the PSSA fuel cell membrane.

• 한국자원식물학회지
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• 제21권1호
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• pp.91-95
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• 2008

본 연구에서는 ${O_2}^-,{\cdot}OH$ radical, NO, $ONOO^-$ 자유라디칼을 유발시키는 in vitro assay system과 free radical-induced oxidative stress에 의한 단백질 손상에 대한 진흙버섯속에 속하는 상황버섯 물 추출물의 항산화 효과를 측정하였다. 상황버섯 물 추출물의 ${O_2}^-,{\cdot}OH$ radical, NO, $ONOO^-$ 자유라디칼 억제효과에서는 실험에 사용된 양성 대조물 보다는 낮게 나타났으나 모든 실험계에서 대조군에 비해 뚜렷하게 자유라디칼 소거효과를 나타냈다. 또한 상황버섯 물 추출물은 산화적 스트레스에 의한 단백질 손상 억제효과에서도 대조군에 비해 명확한 저해효과를 나타냈다. 그러므로 상황버섯의 항산화 효과는 상황버섯의 약리학적 효능을 설명하는데 중요한 기초 자료라고 사료된다.

• 한국환경보건학회지
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• 제24권3호
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• pp.63-69
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• 1998

The treatment of soils and water contaminated with MTBE using the Fenton oxidation was investigated. The effects of dosage of $H_{2}O_{2}$, and Fe$^{2+}$ concentrations, and solution pH on transformation and mineralization in soil were evaluated. Generation of TBA and acetone following Fenton-oxidation of MTBE in water and generation of acetone following Fenton-oxidation of TBA were observed. Therefore TBA and acetone are degradation intermediates of MTBE. There was a large difference of treatment efficiency in Fenton oxidation of MTBE between soil and water system. This may be caused by the complex nature of soil, soil organic matter which can consumed OH $\cdot$ radicals, and interacting with inorganic-soil constituents. The pH of soil was observed to have a significant effect on the chemical oxidation efficient of MTBE in soil The data demonstrated that optimal pH range were pH 3~4 and around 6. The soil batch studies demonstrated that treatment efficiency of MTBE was enhanced by adding additional ferrous salts but Fenton-oxidation occurred in no additional iron which indicated that iron in soil can catalyze the Fenton-oxidation. The most effective parameter of Fentonoxidation was $H_{2}O_{2}$/Fe$^{2+}$ ratio which theocratical ratio is 0.5. The optimal range of this ratio was found to be 0.6~2.3. In evaluating effect of $H_{2}O_{2}$ dosage on treatment efficiency, the increase of $H_{2}O_{2}$ did not always lead to increase of decompositions of MTBE in soil. Fenton oxidation was effective in destroying MTBE in aqueous extracts of contaminated soil and water. Experimental data provided evidence that the Fenton oxidation can effectively remediate MTBE-contaminated water and soil.

• 한국생산제조학회지
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• 제21권4호
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• pp.575-581
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• 2012

The electrochemical oxygen demand (ECOD) is an additional sum parameter, which has not yet found the attention it deserves. It is defined as the oxygen equivalent of the charge consumed during an electrochemical oxidation of the solution. Only one company has yet developed an instrument to determine the ECOD. This instrument uses $PbO_2$-electrodes for the oxidation and has been successfully implemented in an automatic on-line monitor. A general problem of the ECOD determination is the high overpotential of electrochemical oxidations of most organic compounds at conventional electrodes. Here we present a new approach for the ECOD determination, which is based on the use of a solid composite electrodes with highly efficient electro-catalysts for the oxidation of a broad spectrum of different organic compounds. Lead dioxide as an anode material has found commercial application in processes such as the manufacture of sodium per chlorate and chromium regeneration where adsorbed hydroxyl radicals from the electro-oxidation of water are believed to serve as the oxidizing agent. The ECOD sensors based on the Au/$PbO_2$ electrode were operated at an optimized applied potential, +1.6 V vs. Ag/AgCl/sat. KCl, in 0.01 M $Na_2SO_4$ solution, and reduced the effect of interference ($Cl^-$ and $Fe^{2-}$) and an expended lifetime (more than 6 months). The ECOD sensors were installed in on-line auto-analyzers, and used to analyze real samples.

• International Journal of Vascular Biomedical Engineering
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• 제2권2호
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• pp.1-9
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• 2004

The history of studies in biology regarding reactive oxygen species (ROS) is approximately 40 years. During the initial 30 years, it appeared that these studies were mainly focused on the toxicity of ROS. However, recent studies have identified another action regarding oxidative signaling, other than toxicity of ROS. Basically, it is suggested that ROS are reactive, and degenerate to biomolecules such as DNA and proteins, leading to deterioration of cellular functions as an oxidative stress. On the other hand, recent studies have shown that ROS act as oxidative signaling in cells, resulting in various gene expressions. Recently ROS emerged as critical signaling molecules in cardiovascular research. Several studies over the past decade have shown that physiological effects of vasoactive factors are mediated by these reactive species and, conversely, that altered redox mechanisms are implicated in the occurrence of metabolic and cardiovascular diseases ROS is a collective term often used by scientist to include not only the oxygen radicals($O2^{-{\cdot}},\;{^{\cdot}}OH$), but also some non-radical derivatives of oxygen. These include hydrogen peroxide, hypochlorous acid (HOCl) and ozone (O3). The superoxide anion ($O2^{-{\cdot}}$) is formed by the univalent reduction of triplet-state molecular oxygen ($^3O_2$). Superoxide dismutase (SOD)s convert superoxide enzymically into hydrogen peroxide. In biological tissues superoxide can also be converted nonenzymically into the nonradical species hydrogen peroxide and singlet oxygen ($^1O_2$). In the presence of reduced transition metals (e.g., ferrous or cuprous ions), hydrogen peroxide can be converted into the highly reactive hydroxyl radical (${^{\cdot}}OH$). Alternatively, hydrogen peroxide may be converted into water by the enzymes catalase or glutathione peroxidase. In the glutathione peroxidase reaction glutathione is oxidized to glutathione disulfide, which can be converted back to glutathione by glutathione reductase in an NADPH-consuming process.

• Environmental Analysis Health and Toxicology
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• 제24권2호
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• pp.137-148
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• 2009

This study quantitatively investigated the emissions of indoor air pollutants associated with the utilization of air fresheners indoors, and evaluated individual exposure to five specified indoor air pollutants, which were chosen on the basis of selection criteria. An electrically-polished stainless steel chamber (50L) was employed to achieve this purpose. Test air fresheners were selected through three steps: first, on the basis of market sales; second, on the basis on a preliminary head-space study; and lastly, on the basis of emissions of toxic compounds (benzene, ethyl benzene, limonene, toluene, and xylene). The empirical mathematical model fitted well with the time-series concentrations in the environmental chamber (in most cases, determination coefficient, $R^2{\gtrsim}$0.9), thereby suggesting that the empirical model was suitable for testing emissions. The concentration equilibrium appeared 180 min after the introduction of sample air fresheners into the chamber. Both the chamber concentrations of emission rates or factors varied greatly according to air freshener type. It is noteworthy that although benzene, ethyl benzene, toluene, and xylene were emitted from all test air fresheners, their exposure levels were not significant enough to result in any significant health risk. However, certain type of air fresheners were observed to emit significant amount of limonene, which is potentially reactive with ozone to generate secondary pollutants with oxidants such as ozone, hydroxyl radicals, and nitrogen oxides. The exposure levels to limonene associated with the utilization of three air fresheners were estimated to be 13 to 175 times higher than that of other air fresheners. This information can help consumers to select low-pollutant-emitting air fresheners.

• 상하수도학회지
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• 제23권5호
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• pp.669-678
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• 2009

The reduction of excess activated sludge from petrochemical plant was investigated by the electro fenton (E-Fenton) process using electrogenerated hydroxyl radicals which lead to mineralization of activated sludge to $CO_2$, water and inorganic ions. Factors affecting the disintegration efficiency of excess activated sludge in E-Fenton process were examined in terms of five criteria: pH, $H_2O_2/Fe^{2+}$ molar ratio, current density, initial MLSS (mixed liquid suspended solids) concentration, $H_2O_2$ feeding mode. TSS total suspended solid and $TCOD_{cr}$ reduction rate increased with the increasing $H_2O_2/Fe^{2+}$ molar ratio and current density until 42 and $6.7 mA/cm^2$, respectively but further increase of $H_2O_2/Fe^{2+}$ molar ratio and current density would reduce the reduction rate. On the other hand, as expected, increasing pH and initial MLSS concentration of activated sludge decreas TSS and $TCOD_{cr}$ reduction rate. The E-Fenton process was gradually increased during first 30 minutes and then linearly proceed till 120 minutes. The optimal E-Fenton condition showed TSS reduction rate of 62~63% and $TCOD_{cr}$ (total chemical oxygen demand) reduction rate of 55~56%. Molar ratio $H_2O_2/Fe^{2+} = 42$ was determined as optimal E-Fenton condition with initial $Fe^{2+}$ dose of 5.4 mM and current density of $6.7{\sim}13.3 mA/cm^2$, initial MLSS of 7,600 mg/L and pH 2 were chosen as the most efficient E-Fenton condition.

• Advances in Traditional Medicine
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• 제5권2호
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• pp.92-99
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• 2005

Asclepias curassavica. Linn, an erect, simple (or) much branched perennial herb with a somewhat woody base, belonging to the family Asclepiadaceae. It has been reported to have multiple pharmacological effect of anti-inflammatory, cardiotonic, anticancer, anthelmintic and to treat piles and gonorrhoea. It is to be expected that several activities might be related to a possible antioxidant action from this plant. The hydro alcoholic extract of Asclepias curassavica was tested in vitro for its antioxidant activities, such as DPPH radical, nitric oxide radical, superoxide anion radical, lipid peroxidation assay, hydroxyl radical, reducing power, and total phenol content. The extract exhibited scavenging potential with $IC_{50}$ value of $8.7\;{\mu}g/ml,\;198.4\;{\mu}g/ml\;and\;21.7\;{\mu}g/ml$ for DPPH, nitric oxide and superoxide anion radicals. The values were found to higher than those of Vitamin-C, rutin, and curcumin, as standards. The extract showed 50% protection at the dose of $134.2\;{\mu}g/ml\;and\;41.4\;{\mu}g/ml$ in lipid peroxidation as well as deoxyribose degradation, those values more to that of standard, vitamin E $(IC50\;values,\;119.2\;{\mu}g/ml\;and\;32.5\;{\mu}g/ml,\;respectively)$. The reducing power of the extract depends on the concentration and amount of extract. Since a significant amount of polyphenol could be detected by the equivalent to $0.0495\;{\mu}g$ of pyrocatechol from 1 mg of extract. It can be concluded that hydro alcoholic extract of aerial part of Asclepias curassavica could be considered as potent antioxidant, which makes it suitable for the prevention of human disease.

• 한국환경과학회지
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• 제24권11호
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• pp.1315-1329
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• 2015

The objective of this study was to investigate anticytotoxic and antioxidatative capacities of ethanol extracts from Acer tegmentosum Maxim (A. tegmentosum) stem in vitro. The extract at concentration of 200 ug/mL inhibited 10 and 20 ug/mL arsenic trioxide-induced cytotoxicity of HepG2 cells by 79.3 and 57.5%, respectively. The extract at concentration of 200 ug/mL inhibited 0.2 and 0.5 mM t-BHP-induced cytotoxicity of HepG2 cells by 66.3 and 35.7%, respectively. Antioxidative effects of the extract were examined via measurement of ABTS, superoxide, and peroxyl radical scavenging activities. ABTS radical scavenging activity of the extract was higher than that of ${\alpha}$-tocopherol. Superoxide scavenging activity of the extract was higher than that of catechin. Oxygen radical absorbance capacity of the extract was higher than that of ascorbic acid. Cupric reducing antioxidant capacity of the extract was higher than that of ${\alpha}$-tocopherol. The extract at concentrations of 100 and $500{\mu}g/mL$ inhibited 10 mM t-BHP-induced lipid peroxidation of HepG2 cells by 38.2 and 80.7%, respectively. The extract prevented supercoiled DNA strand breakage induced by hydroxyl or peroxyl radical. Total phenolic and flavonoid contents of the extract at concentration of $100{\mu}g/mL$ were 71.3 nmol/mL gallic acid and 18.8 nmol/mL catechin equivalents, respectively. Thus, strong cytoprotective and antioxidant effects of A. tegmentosum stem extract seem to be due to, at least in part, the prevention from free radicals-induced oxidation as well as high levels in polyphenolic contents.