Ja-Won Shin

The enhancement of ammonium removal from ethanolamine wastewater using air-cathode microbial fuel cells coupled to ferric reduction.

A microbial fuel cell (MFC) with biological Fe(III) reduction was implemented for simultaneous ethanolamine (ETA) degradation and electrical energy generation. In the feasibility experiment using acetate as a substrate in a single-chamber MFC with goethite and ammonium at a ratio of 3.0(mol/mol), up to 96.1% of the ammonium was removed through the novel process related to Fe(III). In addition, the highest voltage output (0.53V) and maximum power density (0.49Wm(-2)) were obtained. However, the ammonium removal and electrical performance decreased as acetate was replaced with ETA. In the long-term experiment, the electrical performance markedly decreased where the voltage loss increased due to Fe deposition on the membranes.

Properties of synthetic monosulfate as a novel material for arsenic removal.

Monosulfate was examined as a novel material for As(V) removal since its layered double hydroxide structure was expected to possess a high capacity for anion exchange. Phase-pure monosulfate was synthesized by hydration at 80-90°C for 36 h using a stoichiometric mixture of tricalcium aluminate (calcined at 1300°C) and gypsum. The analyses of PXRD, WDXRF, and FE-SEM confirmed the successful synthesis of highly pure monosulfate with a negligible impurity of ettringite. Batch experiments were carried out to investigate the kinetics of As(V) removal by monosulfate. A close relationship between As(V) uptake and sulfate release was observed. The intercalation of arsenate in the interlayer of monosulfate was confirmed by PXRD and FT-IR analyses. From a series of equilibrium batch experiments, it is seen that initial sorption of As(V) on monosulfate follows Langmuir isotherm, whereas further injection of As(V) caused transformation of monosulfate to ettringite, which was confirmed by FE-SEM micrographs. However, after the transformation, the solid phases in the equilibrium experiments were found to significantly lose their ability to take up As(V) in exchange for sulfate. A possible explanation for this result was hypothesized and discussed in the context of the literature.

Electrochemical reduction of trichloroethylene using zero-valent iron bipolar packed-bed electrodes

AbstractBipolar electrode system has been known to be more efficient than monopolar electrode system in electrolytes of low electrical conductivity. In this study, the bipolar packed-bed electrodes system was investigated to degrade trichloroethylene (TCE) in groundwater which has a poor inherent conductivity of groundwater. Direct current was supplied to columns packed with sand and zero-valent iron (ZVI). The external current makes the ZVI granules in the column act as bipolar electrodes. As a result, TCE was reduced up to 72% with HRT of 62 min. On average, the TCE reduction in 0.13 mM lasted for the experiment period of 1100 h with the electric current of 20 mA. The dominant by-product was ethane, which is a final product of TCE reduction pathways. However, in the column without supplied current, TCE was barely reduced during the experiment. Low concentrations of dechlorinated hydrocarbons were detected compared with the column with current supply, with acetylene showing the highest concentration. No ...

Dechlorination of liquid wastes containing chlorinated hydrocarbons by a binder mixture of cement and slag with Fe(II)

Iron-based degradative solidification/stabilization (DS/S-Fe(II)) is a modification of conventional solidification/stabilization (S/S) that incorporates degradative processes for organic contaminant destruction with immobilization. This study investigated the effectiveness of a binder mixture of Portland cement and slag in a DS/S-Fe(II) system to treat trichloroethylene (TCE), 1,1-dichloroethylene (1,1-DCE), vinyl chloride (VC), trichloromethane (CF), and dichloromethane (MC), which are major chlorinated hydrocarbons contained in waste oils and waste organic solvents. For TCE, 1,1-DCE, and VC, degradation experiments were conducted using three different binder combinations with Fe(II) (cement/Fe(II), slag/Fe(II), and cement/slag/Fe(II)). When cement and slag were mixed at a 1:1 ratio (% wt), the TCE and 1,1-DCE dechlorination rate was enhanced compared to that when cement or slag was used alone with Fe(II). Also, batch experiments were conducted in the solid phase consisting of cement, slag, sand, and Fe(II) to treat liquid wastes that contain chlorinated compounds at high concentrations. TCE was completely removed after 5 days in the cement/slag/sand/Fe(II) system, in which the initial TCE concentration was 11.8mM, with Fe(II) concentration of 565 mM. While the CF concentration was decreased by 95% after 5 days when the initial CF and Fe(II) concentration was 0.25 mM and 200 mM, respectively. However, MC was not degraded with the cement/slag/Fe(II) system.