Kyung-Duk Zoh | Seoul National University (original) (raw)

Papers by Kyung-Duk Zoh

This study used an ozone/ultraviolet/hydrogen peroxide (O 3 /UV/H 2 O 2) system to remove carbama... more This study used an ozone/ultraviolet/hydrogen peroxide (O 3 /UV/H 2 O 2) system to remove carbamazepine (CBZ) from water using a second-order response surface methodology (RSM) experiment with a five-level full-factorial central composite design (CCD) for optimization. The effects of both the primary and secondary interactions of the photocatalytic reaction variables, including O 3 concentration (X 1), H 2 O 2 concentration (X 2), and UV intensity (X 3), were examined. The O 3 concentration significantly influenced CBZ and total organic carbon (TOC) removal as well as total inorganic nitrogen ion production (T-N) (p b 0.001). However, CBZ, TOC removal , and T-N production were enhanced with increasing O 3 and H 2 O 2 concentrations up to certain levels, and further increases in O 3 and H 2 O 2 resulted in adverse effects due to hydroxyl radical scavenging by higher oxidant and catalyst concentrations. UV intensity had the most significant effect on T-N production (p b 0.001). Complete removal of CBZ was achieved after 5 min. However, only 34.04% of the TOC and 36.99% of T-N were removed under optimal concentrations, indicating formation of intermediate products during CBZ degradation. The optimal ratio of O 3 (mg L − 1): H 2 O 2 (mg L − 1): UV (mW cm − 2) were 0.91:5.52:2.98 for CBZ removal, 0.7:18.93:12.67 for TOC removal, and 0.94: 4.85:9.03 for T-N production, respectively.

The levels of 14 micropollutants including nine pharmaceuticals, two pesticides, and three endocr... more The levels of 14 micropollutants including nine pharmaceuticals, two pesticides, and three endocrine dis-ruptors were measured in a water treatment plant (WTP) in Seoul, Korea. Among the measured micropol-lutants, 12 (excluding atrazine and triclocarban) were found in the influent and effluent from the WTP, at levels ranging from 2 to 482 ng L À1. The removal efficiencies of the detected micropollutants in the WTP ranged from 6% to 100%. Among them diclofenac, acetaminophen, caffeine, carbamazepine, and 2,4-D were effectively removed (>80%). Metoprolol was unlikely to be removed (6%) in the WTP process. Concentrations of acetaminophen, metoprolol, ibuprofen, and naproxen were higher in winter, while levels of herbicides of 2,4-dichloro-phenoxyacetic acid (2,4-D) were higher in summer. Metoprolol was hardly removed in the water treatment process. Laboratory experiments showed that compounds with log K ow > 2.5 (especially bisphenol-A, 2,4-D, carbamazepine, triclocarban and 4-nonylphenol) were effectively removed by coagulation process, and adsorption effect increased in proportion with hydrophobic-ity of micropollutants and the turbidity of water. Sunlight photodegradation also effectively removed sulfamethoxazole, sulfamethazine, caffeine, diclofenac, ibuprofen, and acetaminophen, which are photo-sensitizes. Chlorination was relatively not effective for the removal of micropollutants due to the lower chlorine dosage (2 mg L À1), lower contact time (1 h), and already lower levels of micropollutants at the chlorination stage at WTP. Our results imply that micropollutants during coagulation stage at WTP can be removed not only by coagulation itself, but also by adsorption to clay particle especially for high tur-bidity water, and by sunlight photodegradation in the areas open to the atmosphere.

$Research paper thumbnail of The influence of geometrical characteristics on the photocatalytic activity of TiO 2 nanotube arrays for degradation of refractory organic pollutants in wastewater$

Water Science & Technology, 2015

ABSTRACT The effects of geometrical characteristics such as surface area (SA) and porosity of TiO... more ABSTRACT The effects of geometrical characteristics such as surface area (SA) and porosity of TiO 2 nanotube arrays (TNAs) on its photocatalytic activity were investigated by applying variable voltages and reaction times for the anodization of Ti substrates. While larger surface area of nanotubes was observed under higher applied potential, the porosity of TNAs decreased by increasing anodizing voltage. Under applied potential of 80 V, the SA of TNAs increased from 0.164 to 0.471 m2/g as anodization time increased from 1 to 5 hours, respectively. However, no signiﬁcant effect on the porosity of TNAs was observed. On the other hand, both SA and porosity of TNAs, synthesized at 60 V, increased by augmenting the anodization time from 1 to 3 hours. But further increasing of anodization time to 5 hours resulted in a decreased SA of TNAs with no effect on their porosity. Accordingly, the TNAs with SA of 0.368 m2/g and porosity of 47% showed the highest photocatalytic activity for degradation of 4-chlorobenzoic acid (4CBA). Finally, the degradation of refractory model compounds such as, carbamazepine (CZP) and bisphenol-A (BPA) was tested and more than 50% of both compounds could be degraded under UV-A irradiation (λ max ¼ 365 nm).

Environmental monitoring system has been adopted and supplemented as inspection measures for the ... more Environmental monitoring system has been adopted and supplemented as inspection measures for the quantitative and qualitative changes of environmental impact assessment (EIA). This study compares the results of environmental impact assessment with the results of post-environmental investigation using a correction and principal component analysis (PCA) in the housing development project. Correlation analysis showed that most of air quality variables including TSP, , CO were linearly correlated with each other in the environmental impact assessment and the post-environmental investigation. In the water quality, pH and BOD were well correlated with the DO and SS, respectively. As a result of correlation analysis in the noise and vibration, noise in day and night and vibration in day and night were related to each other between EIA and the post-environmental investigation. From the results of analysis of soil, Cu with Cd, Cu with Pb, and Cd with Pb were related to each other in EIA. Pri...

Water Science & Technology Water Supply

First, a continuous flow TiO2/UV reactor was designed and developed in order to examine E. coli d... more First, a continuous flow TiO2/UV reactor was designed and developed in order to examine E. coli disinfection effect using UV light. The optimum conditions for disinfection such as flow rate, light intensity, TiO2 concentration, initial E. coli concentration were examined. The results are as follow (i) The use of the quartz device and TiO2 (anatase) resulted in killing of E. coil within minutes. (ii) Photocatalytic disinfection with UV light in the presence of TiO2 more effectively killed E. coli than UV or TiO2 adsorption only. (iii) As flow rate increased, the survival ratio of E. coli decreased, but over 3 L/min of flow rate, the efficiency was limited. (iv) E. coli survival ratio decreased linearly with increasing UV light intensity. (v) The dosage of TiO2 affected the E. coli disinfection efficiency, and above 0.1 wt% TiO2 concentration, the disinfection was less effective because TiO2 particles may result in screening off the light. (ri) The disinfection reaction follows first-...

Objectives: This study was aimed at determining the optimum coagulation dosage in a high turbid k... more Objectives: This study was aimed at determining the optimum coagulation dosage in a high turbid kaolin water sample using streaming current detection (SCD) as an alternative to the jar test. Methods: SCD is able to optimize coagulant dosing by titration of negatively charged particles. Kaolin particles were used to mimic highly turbid water ranging from 50 to 600 NTU, and polyaluminum chloride (PAC, 17%) was applied as a titrant and coagulant. The coagulation consisted of rapid stirring (5 min at 140 rpm), reduced stirring (20 min at 70 rpm), and settling (60 min). To confirm the coagulation effect, a jar test was also compared with the SCD titration results. Results: SCD titration of kaolin water samples showed that the dose of PAC increased as the pH rose. However, supernatant turbidity less than 1 NTU after coagulation was not achieved for high turbid water by SCD titration. Instead, a conversion factor was used to calculate the optimum PAC dosage for high turbid water by correla...

This study investigated the degradation of phenol using sonication and/or UV-C. The effects of fr... more This study investigated the degradation of phenol using sonication and/or UV-C. The effects of frequency, temperature, pH in solution, argon purging, with UV intensity were estimated in sonication-only, UV-only, and the combined reaction of sonication with UV. The optimum condition for degrading phenol in the sonication-only reaction was 35 kHz, , and pH 4. As this condition approximately 30% degradation of phenol was achieved within 360 min. However, phenol in the UV-only at under the same condition was completely degraded within 60 min. In the combined system of sonication with UV, the degradation of phenol was well fitted to first-order rate model, and phenol was completely degraded within 360 min and 45 min at UV intensity of () and (), respectively. Adding methanol, as a radical scavenger, in the phenol degradation in the sonication reaction indicates that OH radical is a major factor in the degradation of phenol. The order of degradation efficiencies of phenol was in the order...

Micropollutants emerge in surface water through untreated discharge from sewage and wastewater tr... more Micropollutants emerge in surface water through untreated discharge from sewage and wastewater treatment plants (STPs and WWTPs). Most micropollutants resist the conventional systems in place at water treatment plants (WTPs) and survive the production of tap water. In particular, pharmaceuticals and endocrine disruptors (ECDs) are micropollutants frequently detected in drinking water. In this review, we summarized the distribution of micropollutants at WTPs and also scrutinized the effectiveness and mechanisms for their removal at each stage of drinking water production. Micropollutants demonstrated clear concentrations in the final effluents of WTPs. Although chronic exposure to micropollutants in drinking water has unclear adverse effects on humans, peer reviews have argued that continuous accumulation in water environments and inappropriate removal at WTPs has the potential to eventually affect human health. Among the available removal mechanisms for micropollutants at WTPs, coag...

Journal of Hazardous Materials, 2015

Chemosphere, Jan 21, 2015

The adsorptive properties of graphene oxide (GO) were characterized, and the binding energies of ... more The adsorptive properties of graphene oxide (GO) were characterized, and the binding energies of diclofenac (DCF) and sulfamethoxazole (SMX) on GO adsorption were predicted using molecular modeling. The adsorption behaviors of DCF and SMX were investigated in terms of GO dosage, contact time, and pH. Additionally, the effects of sonication on GO adsorption were examined. GO adsorption involves "oxygen-containing functional groups" (OCFGs) such as COOH, which exhibit negative charges over a wide range of pH values (pH 3-11). DCF (-18.8kcalmol(-1)) had a more favorable binding energy on the GO surface than SMX (-15.9kcalmol(-1)). Both DCF and SMX were removed from solution (adsorbed to GO), up to 35% and 12%, respectively, within 6h, and an increase in GO dosage enhanced the removal of DCF. Electrostatic repulsion occurred between dissociated DCF/SMX and the more negatively charged GO at basic pH (>pKa). The sonication of GO significantly improved the removal of DCF (75%)...

Water science and technology : a journal of the International Association on Water Pollution Research, 2005

Photocatalytic degradation of methyl parathion was done using a circulating TiO2/UV and TiO2/sola... more Photocatalytic degradation of methyl parathion was done using a circulating TiO2/UV and TiO2/solar reactor. Indoor experimental results showed that, under the photocatalysis conditions, parathion was more effectively degraded than under the photolysis and TiO2 only conditions. Parathion (38 microM) was completely degraded under photocatalysis within 90 min, and more than 80% TOC decrease after 150 minutes. The main ionic byproducts during the photocatalysis were measured, and almost complete nitrogen recovery was achieved as mainly NO3- NO2-, and NH4+, and 80% of sulfur as recovered as SO4(2)-. Organic intermediates such as nitrophenol and methyl paraoxon were also identified during the photocatalysis of parathion, and these were further degraded after 90 minutes. Microtox bioassay using Vibrio fischeri was used in evaluating the toxicity of solutions treated by photocatalysis and photolysis of parathion. The results showed that the acute toxicity expressed as EC50 almost reduced af...

Korean Journal of Environmental Health Sciences, 2012

Atmospheric Environment, 2015