Seongpil Jeong

Preparation of chitosan self-aggregates as a gene delivery system

Hydrophobically modified chitosan containing 5.1 deoxycholic acid groups per 100 anhydroglucose units was synthesized by an EDC-mediated coupling reaction. Formation and characteristics of self-aggregates of hydrophobically modified chitosan were studied by fluorescence spectroscopy and dynamic light scattering method. The critical aggregation concentration (cac) of the self-aggregate was determined by measuring the fluorescence intensity of pyrene as a fluorescent probe. The cac value in PBS solution (pH 7.2) was 1.7x10(-2) mg/ml. Mean diameter of self-aggregates in PBS solution (pH 7.2) was 162 +/- 18 nm with an unimodal size distribution. Charge complex formation between self-aggregates and plasmid DNA was confirmed by electrophoresis on an agarose gel. Migration of DNA on an agarose gel was completely retarded above a charge ratio ( +/-) of 4/1 at pH 7.2. The free DNA dissociated from the complexes was observed by electrophoresis above pH 8.0 at a fixed charge ratio of 4/1. An efficient of COS-1 cells was achieved by self-aggregates/DNA complexes.

Oxidation of bisphenol A by UV/S2O : Comparison with UV/H2O2

The UV/S2O process was applied to decompose bisphenol A (BPA), which is a representative endocrine-disrupting chemical (EDC), and was comared with the UV/H2O2 process. The BPA degradation efficiency by UV/S2O was increased by increasing S2O concentration or decreasing BPA concentration. The presence of humic acid caused an inhibitory effect. The BPA oxidation rate by UV/S2O was increased in the following order: neutral pH (pH i=7)<acidic pH (pH i=4)<basic pH (pH i=10). The main oxidizing species in the UV/S2O system was sulphate radical (SO ), whereas the main oxidizing species in the UV/H2O2 system was OH radical (OHċ). Compared with UV/H2O2, the UV/S2O process showed higher performance for not only BPA degradation but also its mineralization, which means that SO is a more effective oxidant for BPA than the OH ċ. The results shown in this study imply that the SO -based UV/S2O process can be an excellent alternative process for the widely used UV/H2O2 process, with higher remediation performance.

Application of three different water treatment technologies to shale gas produced water

Abstract Shale gas produced water is a hypersaline wastewater that is generated during the shale gas development process called as a hydraulic fracturing. The produced water contains many substances including inorganic salts, organic compounds, and particulates. The treatment process of the produced water is mainly composed of four parts: oil and water separation, removal of suspended solids, removal of organics, and salts removal. This study focuses on the total dissolved salts removal through applying three different desalination techniques – membrane distillation (MD), reverse osmosis (RO), and evaporative crystallization (EC). The experiments were conducted using synthetic shale gas produced water to understand the changes of chemical properties in permeate and concentrate. In the permeate solution, MD and EC showed more than 99% of salts removal efficiency for all ions, but RO showed relatively low efficiency. In the concentrate solution, the concentrations of all ions varied according to the type of ions and applied treatment methods.

Indoor radon measurements of the multi-storey buildings in Seoul, Korea

Most people are exposed to various kinds of indoor pollutants due to spending most of their time indoors. Unlike other anthropogenic pollutants of the indoor environment, radon gas is a naturally formed radioactive pollutant and it has been known as a second major contributor to lung cancer. However, most radon studies have focused on underground facilities and one-story buildings because the dominant source of indoor radon was known as the soil gas which was emitted from cracks or pores of the wall on the ground. Three study areas were selected for this research: the first and the second floor of a two-storey building (area A), the third floor of a newly built four-storey building (area B), and the 11th floor of a 15-storey apartment house (area C). Radon concentrations were measured by means of etched-track detectors (passive method) and by continuous measurements (active method). The active method was only used in area B because of continuous pump noise of the measuring device. Radon concentrations were monitored by the passive method for 3 or 4 months according to the study area. Continuous measurements were conducted for 3 months using the radon monitoring instrument (RAD7). The measuring protocol for the active method was ‘sniff’. The average radon concentrations determined by the passive and the active methods in area B were 2.9 and 1.8 pCi/L, respectively. The radon concentration measured by the passive method was 1.6 times higher than that measured by the active method. The average radon concentration in area C was 1.7 pCi/L (range 1.3–2.1 pCi/L) and slightly higher than that in area A (average 1.3 pCi/L with a range of 0.6–2.1 pCi/L). The results suggest that more detailed studies on the sources and rates of radon emissions are needed for multi-storey buildings.