Application of Various Adsorbents to Remove Micro-Pollutants in Aquatic System

Untreated or insufficiently treated pharmaceuticals and endocrine disrupting compounds (EDCs) as well as heavy metals have influenced the ecosystem and their exposures in the water system have threatened human health; causing cancers and adverse health effect to immune system. While various water treatment techniques have been applied to solve this problem, adsorption has been considered as one of the most efficient and manageable water purification techniques. Advanced analysis methods for aqueous contaminants have improved comprehension, allowing proficiency about the fate of trace leveled emerging contaminants, thus allowed to reveal the adsorption mechanisms of each pollutant. This dissertation focuses on the investigation of adsorption for micro-pollutants in aquatic environment via the application of different types of carbonaceous (powdered activated carbon, carbon nanotubes, and biochars) and biodegradable (chitosan) adsorbent. The effect of water chemistry conditions such as pH, concentration of ionic strength induced species and natural organic matters were considered as significant factors to increase or decrease the adsorption capacity of each adsorbent. This study also illuminates the use of biochar, byproduct of bio-oil, with simple chemical activation as an efficient adsorbent for pharmaceutical and EDCs removal. In-depth analysis about adsorption between these micro-pollutants and biochars was performed by characterization of physicochemical properties by nuclear magnetic resonance analysis in conjunction with molecular modeling subsequently interpreting the binding energy. Aromaticity and composition of carbonaceous structure of adsorbent controlled the adsorption capacity, while hydrophobicity of adsorbates influenced the adsorption affinity toward the adsorbents. More specifically, the presence of adsorption competitors resulted in less effective binding due to a combination of less favorable binding energy, polarity, and π-energy with the adsorbent and electrostatic repulsion from the cosolutes that occupied adsorption sites

A Study on the onset of civil conflict

Thesis(Master) --KDI School:Master of Public Policy,2015The author broadly categorizes the models of civil war literatures on conflict onset into five dimensions: government, individual, geo-political, regional, and international. From empirically testing the models from each dimension, this study was able to find largely consistent results with major works on the topic. The following indicators were significant from the testing: on government dimension, the government’s capacity to repress and contain dissents; on individual dimension, the private incentives such as lootable primary commodities and opportunity costs proxied by education and income; on geo-political dimension, natural resource sites and the history of conflict; on regional dimension, regional spill-over effects through population movement and neighboring conflicts; finally, on international dimension, peacekeeping operations on the prevention of recurring civil war. This study used panel IV regression with an endogenous variable, GDP per capita instrumented with the access to electricity (% of household). Additionally, this study used dynamic panel models for the estimation of the effect of peacekeeping operations on the recurrence of civil war to supplement more commonly used survival analysis, which does not include temporal variations of independent variables. The findings suggest that there are specific conditions that favor the onset of civil war, and that civil wars are not necessarily accidental or idiosyncratic. Based on this findings, the author argues that the international efforts should be a two-tracked approach: one with immediate intervention to halt conflicts and regional spill-over; and the other with a more targeted approach to economic and social development.I. INTRODUCTION II. LITERATURE REVIEW Government dimension Individual dimension Geopolitical dimension Regional dimension International dimension IV. EMPIRICAL ANALYSIS OF THE THEORIES OF CIVIL WAR ONSET Research Data Models and Hypotheses Testing V. CONCLUSION VI. REFERENCESmasterpublishedChanil JUNG

Effects of molecular crowding and confinement on the spatial organization of a biopolymer

A chain molecule can be entropically collapsed in a crowded medium in a free or confined space. Here, we present a unified view of how molecular crowding collapses a flexible polymer in three distinct spaces: free, cylindrical, and (two-dimensional) slit-like. Despite their seeming disparities, a few general features characterize all these cases, even though the phi(c)-dependence of chain compaction differs between the two cases: a > a(c) and a a(c) (applicable to a coarse-grained model of bacterial chromosomes), chain size depends on the ratio a phi(c)/a(c), and "full'' compaction occurs universally at a phi(c)/a(c) approximate to 1; for a(c) > a (relevant for protein folding), it is controlled by phi(c) alone and crowding has a modest effect on chain size in a cellular environment (phi(c) approximate to 0.3). Also for a typical parameter range of biological relevance, molecular crowding can be viewed as effectively reducing the solvent quality, independent of confinement.NSERC (Canada)Korea Institute of Science and Technology Information (KISTI)Basic Science Research Program [2015R1D1A1A09057469]KIAS (Korea Institute for Advanced Study

How are molecular crowding and the spatial organization of a biopolymer interrelated

In a crowded cellular interior, dissolved biomolecules or crowders exert excluded volume effects on other biomolecules, which in turn control various processes including protein aggregation and chromosome organization. As a result of these effects, a long chain molecule can be phase-separated into a condensed state, redistributing the surrounding crowders. Using computer simulations and a theoretical approach, we study the interrelationship between molecular crowding and chain organization. In a parameter space of biological relevance, the distributions of monomers and crowders follow a simple relationship: the sum of their volume fractions rescaled by their size remains constant. Beyond a physical picture of molecular crowding it offers, this finding explains a few key features of what has been known about chromosome organization in an E. coli cell.NSERC (Canada)Korea Institute of Science and Technology Information (KISTI)Basic Science Research Program [2015R1D1A1A09057469]KIAS (Korea Institute for Advanced Study

Mitigation and Degradation of Natural Organic Matters (NOMs) During Ferrate(VI) Application for Drinking Water Treatment

Ferrate(VI), as an alternative for pre-oxidation in drinking water treatment, has recently captured renewed interest. However, the knowledge in ferrate(VI) chemistry remains largely undeveloped. The information regarding ferrate(VI) reactions with natural organic matters (NOMs), an important water matrix component affecting water treatment, is highly limited. In this study, bench scale tests were performed to study ferrate(VI) decay and reactions with NOMs in a typical surface water matrix. Results showed that ferrate(VI) decay exhibited a pseudo 2nd-order reaction pattern (k obs = 15.2-1.6 mM -1 min -1 and 36.3-4.0 mM -1 min -1 with 1.0-7.0 mg/L Fe(VI) at initial pH 7.8 and 5.8, respectively), suggesting that self-decomposition is principally responsible for ferrate(VI) consumption. Ferrate(VI) tended to attacked electron-rich moieties in NOM molecules, but had limited capability to mineralize NOMs. Consequently, ferrate(VI) effectively reduced UV 254 and specific UV absorbance (SUVA 254 ), but poorly removed dissolved organic carbon (DOC). Generally, lower pH and higher ferrate(VI) dose favored the NOM destruction. Fe(VI) (3.0 mg/L) could remove 16% of initial DOC (4.43 mg/L), 56% of initial UV 254 (0.063 cm -1 ), and 48% of initial SUVA 254 (0.033 cm -1 (mg/L) -1 ) at pH 5.80. Further organics analyses indicate that ferrate(VI) readily degraded hydrophobic and transphilic NOM fractions, but scarcely decomposed hydrophilic fraction. Fluorescence excitation-emission matrix (EEM) and fluorescence regional integration (FRI) analyses revealed that ferrate(VI) preferentially reacted with fulvic-like (region III) and humic-like (region V) substances and certain aromatic proteins (region II), difficultly decomposed soluble microbial byproducts (region IV), and rarely oxidized aromatic proteins in region I

Chemical Oxidation for Mitigation of UV-Quenching Substances (UVQS) from Municipal Landfill Leachate: Fenton Process Versus Ozonation

UV-quenching substance (UVQS), as an emerging municipal solid waste (MSW)-derived leachate contaminant, has a potential to interfere with UV disinfection when leachate is disposed of at publicly owned treatment works (POTWs). The objective of this study was to evaluate and compare two chemical oxidation processes under different operational conditions, i.e. Fenton process and ozonation, for alleviation of UV254 absorbance of a biologically pre-treated landfill leachate. Results showed that leachate UV254 absorbance was reduced due to the UVQS decomposition by hydroxyl radicals (·OH) during Fenton treatment, or by ozone (O3) and ·OH during ozonation. Fenton process exhibited a better treatment performance than ozonation under their respective optimal conditions, because ·OH could effectively decompose both hydrophobic and hydrophilic dissolved organic matter (DOM), but O3 tended to selectively oxidize hydrophobic compounds alone. Different analytical techniques, including molecular weight (MW) fractionation, hydrophobic/hydrophilic isolation, UV spectra scanning, parallel factor (PARAFAC) analysis, and fluorescence excitation-emission matrix spectrophotometry, were used to characterize UVQS. After either oxidation treatment, residual UVQS was more hydrophilic with a higher fraction of low MW molecules. It should be noted that the removed UV254 absorbance (ΔUV254) was directly proportional to the removed COD (ΔCOD) for the both treatments (Fenton process: ΔUV254 = 0.011ΔCOD; ozonation: ΔUV254 = 0.016ΔCOD). A greater ΔUV254/ΔCOD was observed for ozonation, suggesting that oxidant was more efficiently utilized during ozonation than in Fenton treatment for mitigation of the UV absorbance

A ring-polymer model shows how macromolecular crowding controls chromosome-arm organization in Escherichia coli

Abstract Macromolecular crowding influences various cellular processes such as macromolecular association and transcription, and is a key determinant of chromosome organization in bacteria. The entropy of crowders favors compaction of long chain molecules such as chromosomes. To what extent is the circular bacterial chromosome, often viewed as consisting of “two arms”, organized entropically by crowding? Using computer simulations, we examine how a ring polymer is organized in a crowded and cylindrically-confined space, as a coarse-grained bacterial chromosome. Our results suggest that in a wide parameter range of biological relevance crowding is essential for separating the two arms in the way observed with Escherichia coli chromosomes at fast-growth rates, in addition to maintaining the chromosome in an organized collapsed state. Under different conditions, however, the ring polymer is centrally condensed or adsorbed onto the cylindrical wall with the two arms laterally collapsed onto each other. We discuss the relevance of our results to chromosome-membrane interactions

Expansion dynamics of a self-avoiding polymer in a cylindrical pore

Inspired by recent bacterial chromosome experiments in narrow channels, we simulate the expansion (and internal) dynamics of a self-avoiding polymer under cylindrical confinement. The chain is trapped in a piston, compressed up to $20\%$ of its equilibrium length, and released unidirectionally from the right end of the piston. Our results suggest that the chain initially expands like a concentrated hard-sphere system, enters a subdiffusive regime at an intermediate time, and eventually relaxes globally to its equilibrium size. Using our results, we test a few theoretical models (e.g., a Flory-type approach), in which the blob-blob or monomer-monomer interaction determines “expansion forces,” clarifying their applicability. Our results can be used for exploring further the polymer aspect of bacterial chromosomes

Role of Baroclinic Trough in Triggering Vertical Motion during Summertime Heavy Rainfall Events in Korea

The nature of the vertical motion responsible for the summertime heavy rainfall events (HREs) in South Korea is quantitatively examined. By compositing 318 HREs from June to September in 1979-2018, it is found that the synoptic conditions of the HREs are typically characterized by a developing surface cyclone with a southwesterly low-level jet on its southeastern flank and an upper-level trough to the west of the HREs. This baroclinic environment allows for well-organized vertical motion over South Korea at the equatorward side of the upper-level jet entrance. The relative importance of dynamic and diabatic forcings in driving the vertical motion is further quantified by solving the quasigeostrophic omega equation. It turns out that the dynamic forcing, defined as Q-vector convergence, is comparable to the diabatic forcing in the developing stage of the HREs. The diabatic forcing, however, becomes more important in the mature stage as latent heating rapidly increases. The decomposition of the Q vector into the transverse (cross-isentropic) and shearwise (along-isentropic) components reveals that the dynamic uplift is largely caused by the shearwise Q-vector convergence, which is closely related to the developing trough in the upper to middle troposphere on the west of the HREs. This result indicates that the HREs in South Korea are organized by the baroclinic trough coupled to moist processes, with a minor contribution of the thermally direct secondary circulation at the entrance region of the upper-level jet.N

Characterization of Ultraviolet-Quenching Dissolved Organic Matter (DOM) in Mature and Young Leachates Before and After Biological Pre-Treatment

The discharge of municipal landfill leachate into publicly owned treatment works (POTWs) is a common leachate management practice in the United States. However, the benefits of this option have diminished in many POTWs because leachate can significantly interfere with UV disinfection due to the introduction of UV-quenching substances (UVQS). This study aims to characterize UV-quenching dissolved organic matter (DOM) in different raw and sequencing batch reactor (SBR) pre-treated landfill leachates. Nine leachate samples, including four raw mature leachates, four SBR pre-treated mature leachates, and one young raw leachate, were investigated. The mature leachates, regardless of raw or SBR pre-treated ones, had lower biodegradability (low BOD5/COD), higher specific UV absorbance (SUVA), greater hydrophobic fraction, and more high molecular weight (MW) organic compounds than the young leachate. SUVA served as a useful indicator for the characterization of UV-quenching DOM, which exponentially declined with increasing BOD5/COD. The high SUVA of the mature leachates suggests a highly aromatic and hydrophobic character with a high fraction of aquatic humic matter and high MW compounds. In contrast, the low SUVA of the young leachate implies the presence of a high fraction of non-humic matter, a highly aliphatic character, and more low MW molecules. After the mature leachates were biologically pre-treated, the SUVA increased due to the partial degradation of high MW compounds. Results from fluorescence excitation-emission matrix (EEM) analysis could effectively reflect the variation of hydrophobic DOM, but poorly indicated the presence of hydrophilic DOM