Daewon Pak

Design parameters for an electrochemical cell with porous electrode to treat metal–ion solution

An electrochemical reactor was designed and operated to treat the solution containing copper ions. Design parameters for the electrochemical reactor using the porous cathode and RuO2/IrO2/Ti anode were investigated. The porous cathode was prepared by the electroless nickel deposition on polyurethane. The apparent current, the gap between cathode and anode, and hydraulic retention time (HRT) were selected as design parameters. The copper removal rate increased with an increase in apparent current. It was not affected by the gap between the cathode and the anode. A reduction in hydraulic retention time stimulated the mass transfer toward the electrode and increased the cathodic current efficiency. Dimensional analysis was conducted to obtain the design equation for scale-up of the electrochemical reactor. The dependence of Sh on Re, Sc, and characteristic lengths, DC/A/L and DW/C/L, was described in the form of a power series. The coefficients were obtained from experimental data.

Ammonium exchange and bioregeneration of bio-flocculated zeolite in a sequencing batch reactor

Natural zeolite was added to the sequencing batch reactors to assess its role in ammonium exchange. Even though the biofilm was fully developed on the zeolite surface, ammonium removal and the biological regeneration of the zeolite occurred constantly during the anoxic-fill phase and the reaction phase, respectively. However, the specific nitrification rate of the bio-flocculated zeolite was lower than that observed in the control on account of the limited ammonium release to the liquid phase.

Biosorption of Heavy Metal Ions by Immobilized Zoogloea and Zooglan

ImmobilizedZoogloea and zooglan in calcium alginate-silica matrix was shown to have a high adsorption capacity for Cu and Cd ions. Our results showed that Cu-ion uptake in the presence of Ca and Mg ions can be enhanced using immobilizedZoogloea and zooglan. Heavy metal ion adsorption efficiency decreased in the following order: Cu > Cd > Zn > Cr. The adsorbed metal ions were desorbed completely using sulfuric acid. ImmobilizedZoogloea and zooglan which was repetitively regenerated adsorbed heavy metal ions without a loss of adsorption capacity.

Development of Preparation Technology for TiO 2 Nanotube Photocatalyst

Abstract In this study TiO 2 nanotube was grown on Ti by anodic oxidation to be used as a photocatalyst. The growth and formation of TiO 2 nanotube was monitored during anodization in ethylene glycol electrolyte by changing voltage and composition of electrolyte. Commercially available titanium plate (purity>99.8%, thickness:1mm) Applied voltage and concentration of NH 4 F and H 2 O were varied to find the optimum condition. Applied voltage is important to make TiO 2 nanotube and the electrolyte containing ethylene glycol, 0.2 wt% NH 4 F and 2 vol% H 2 O was confirmed to be the optimum conditions for the formation and growth of TiO 2 nanotubes. Key words : Anodizing, Current density, Photocatalyst, TiO 2 nanotube 1. Introduction 1)인류의 기술과 환경은 ‘삶의 질’ 향상이란 명분 아래 과학기술의 놀라운 진보를 거듭해 왔지만 그로 인해 생겨난 환경오염문제로 인해 생태계는 생존의 커다란 위협을 맞고 있다. 인간생활 및 산업 활동에 의해 무방비 상태로 배출되는 생활하수, 공업폐수 등으로 인해 우리나라 뿐 만 아니라 전 세계적으로 환경오염의 피해가 날로 심각해져 가고 있으며, 무분별한 벌목과 토목건설 등의 파괴는 자연 본연의 자정 능력을 상당 부분 상실하게 만들어 스스로의 자정을 기대하기 어려운 실정이다. 오늘날에는 이러한 오염원을 제거･정화하기 위한 다양한 방법들이 연구되고 있다 .일반적으로 사용되는 하수와 공업 오･폐수 처리 기술에는 미생물을 이용한 생물학적 처리 기술과 여과, 응집, 침전, 부상, 흡수, 흡착, 산화와 환원 등을 이용하는 물리･화학적 처리 기술 등이 있는데, 생물학적 처리의 경우 반응시간이 오래 걸리고 난분해성 유기물 처리 시 급작스런 오염물질 부하에 적절하게 대응하지 못하며 pH, 온도, 유기물 부하 등 운전 조건이 까다로운 문제점이 있다 . 물리학적 처리 기술은 수중의 큰 용존 물질이나 부유 물질을 제거하는 전처리 방법에는 효과적 일수 있지만 근본적인 폐

A Study on Biogas Yield According to Food Waste Leachate Acid Fermentation Conditions

This study performed acid fermentation pre-treatment to improve production efficiency of methane that is produced as a product in case of anaerobic fermentation by using food waste leachate, and attempted to confirm the acid fermentation optimum through the BMP test by using pre-treated food waste leachate to increase the yield of methane. As a result of the BMP experiment by using acid fermented food waste leachate, the highest yield of methane of 0.220 L/g VS was confirmed in the HRT three-day condition, and in the initial BMP test by pH, pH 6 was 19,920 mg/L that the highest VFA and acetic acid/TVFA(76.2%) were shown. At this time, it was confirmed that the yield of methane was mostly within 10 days that was reduced to around one-third compared to the general methane fermentation (within 30 days). As the yield of methane was 0.294 L/g VS, it showed a high efficiency of around 1.3 times compared to the control group.

Effect of torrefaction on enzymatic saccharification of lignocellulosic biomass

Abstract - This study is to investigate the effect of torrefact ion on enzymatic hydrolysis of lignocellulosic biomass for bio-ethanol production. As a pretreatment, the torr efaction of lignocellulosic biomass was conducted in temperature of 250 ∼350℃ in the absence of oxygen. Tween-80, nonionic surfactant, was tested to enhance saccharification efficiency by coping with hy drophobicity resulted from torrefaction. As a result, the glucose production from enzymatic hydrolysis of b iomass pretreated by torrefaction was greater than that obtained from the non-pretreated biomass. Sugar conve rsion was higher when the biomass was saccharified with addition of tween-80. It was found that torre faction can be applied as a preptreatment for lignocellulosic biomass and tween-80 is needed to enhance i ts enzyme saccharification. Key words : lignocellulosic biomass, pretreatment, saccharification, Tween-80, enzymatic hydrolysis † To whom corresponding should be addressed.Professor, Department of Environmental Energy Engineering,The Graduate School of Energy and EnvironmentSeoul National University of Science and TechnologyTel : 02-970-6595 E-mail : daewon@seoultech,ac,kr

The Characteristics of Hydrogen Production According to Electrode Materials in Alkaline Water Electrolysis

Abstract - This study confirmed the characteristics of hydrogen production according to electrode materials by producing non-diaphragm alkaline water electroanalyzer that can be controlled at medium temperature to produce hydrogen. As a result of the electrochemical characteristics by electrode material (IrO 2 /Ti, RuO 2 /Ti, Ti), the highest efficiency was found in RuO 2 /Ti, as a result of hydrogen production experiment by electrolyte concentration, electrolyte concentration has a t endency to be proportional to hydrogen production and the condition of 30% KOH showed the highest hydr ogen production as 118.9 m 3 /m 3 /day. In the experiment that confirmed hydrogen production according to electrode materials, in case of combination of anode (IrO 2 /Ti) and cathode (RuO 2 /Ti), it was 157.55 m 3 /m 3 /day that showed a higher hydrogen production by around 6.97% than that of IrO 2 /Ti and cathode. It is presumed that the improvement of electrochemical activation of DSA electrode increases hydrog en production and influences the impro-vement of durability compared to the former electrode so that i t enables stable alkaline water electrolysis.

Comparison of pretreatment of fallen leaves for application evaluation by Bio-ethanol raw material

This study is to compare characteristics of saccharification reactions applying to enzymatic hydrolysis of pretreated fallen leaves for bio-ethanol production. It experimented pretreatment of acid, alkaline in the chemical. This experiment includes preteatment of acid and alkaline in chemical, soaking, shaking and autoclaving method, which were applied to biomass. In result, the glucose production from alkaline-NaOH method was 263 mg glucose/ g biomass comparing with them of acid-HCl method. Thus, alkaline-NaOH method is superior than the acid-HCl method for chemical preteatment of fallen leaves. Also, when various chemical treatments were compared, they were all. Based on the results of this study, we found that leaves, one of biomass, are possible in pretreatment and enzymatic hydrolysis process, and they are likely to affect bio-ethanol production in the future.

Effect of temperature on torrefaction of food waste to produce solid fuel

In this study, the torrefaction of food waste was conducted to characterize its product, to find out effect of the operating temperature and to assess the feasibility of being used as fuel. The operating temperature was varid from 180 270 and heat was provided by using nitrogen gas or waste oil heat carrier. The solid yield and moisture content were reduced were reduced as temperature increased. The moisture content reduction and thermochemical conversion were observed at higher than 240 . At low operating temperature, heat transfer efficiency was higher with wast oil heat carrier. As temperature increases, there was not difference in heat transfer efficiency of two different heating methods. The lower heating value product was increased from 660 to 6,400 Kcal/kg with nitrogen gas and 6,890 Kcal/kg with waste oil heat carrier. The elemental analysis indicates that, as temperature increases, the carbon content of product increases and oxygen content decreases. From the analysis of O/C and H/C, the torrefaction product was close to low grade coal. The characteristics of fuel converted from the food subsequent thermochemical treatment.

Characteristics of Anaerobic Acid Fermentation with Food waste leachate by Reactor Type of Retention Time for Landfill Site Injection

In order to increase landfill gas (LFG) production with food waste leachate, this study was confirmed to be acidogenetic conditions for landfill site injection. Thereby, it was conducted for acidogenetic treatments to determine the decrease in viscosity and VFA production. After acidogenesis treatments, solubility of food waste leachate increased approximately 15%, and as a result, UASB and CSTR were similar by reactor type using the change of retention time. Based on the result of the change in viscosity by reactor type, efficiency of UASB showed approximately 11.38% of higher decrease in viscosity as 76.95±3.27% vs. CSTR. Also, VFA production showed the higher increase of 2.01 times (UASB) and 1.76 times (CSTR) respectively at the point of increasing retention time from 3 to 5 days. From the above results, efficiency of UASB in a reactor was relatively higher because large molecular lead to longer retention time than small molecular due to having screen effect in the fixed media.