ng-Gyu Seo

Assessment of Microwave/UV/O3 in the Photo-Catalytic Degradation of Bromothymol Blue in Aqueous Nano TiO2 Particles Dispersions

In this study, a microwave/UV/TiO2/ozone/H2O2 hybrid process system, in which various techniques that have been used for water treatment are combined, is evaluated to develop an advanced technology to treat non-biodegradable water pollutants efficiently. In particular, the objective of this study is to develop a novel advanced oxidation process that overcomes the limitations of existing single-process water treatment methods by adding microwave irradiation to maximize the formation of active intermediate products, e.g., OH radicals, with the aid of UV irradiation by microwave discharge electrodeless lamp, photo-catalysts, and auxiliary oxidants. The results of photo-catalytic degradation of BTB showed that the decomposition rate increased with the TiO2 particle dosages and microwave intensity. When an auxiliary oxidant such as ozone or hydrogen peroxide was added to the microwave-assisted photo-catalysis, however, a synergy effect that enhanced the reaction rate considerably was observed.

Photocatalytic Activity of Titanate Nanotube Powders in a Hybrid Pollution Control System

The photocatalytic activity on decomposition of Rhodamine B (RB) of titanate nanotubes (TNTs) synthesized by alkali hydrothermal treatment method was evaluated using a microwave/UV/photocatalyst hybrid system. The effects of each element technique as well as the synergy effects on decomposition of organic material were investigated. When TNTs were ion-exchanged with HCl, Na

Contribution of Dissolved Oxygen to Methylene Blue Decomposition by Hybrid Advanced Oxidation Processes System

Experimental results of photocatalysis under high dissolved oxygen (DO) concentration conditions are reported. Methylene blue was used as the organic pollutant to be degraded by a novel microwave/UV/DO/TiO2 photocatalyst hybrid system. The degradation rate increased with TiO2 nanoparticle dosages and DO concentration. However, inhibition of photocatalysis due to bubbles produced by DO generator was also observed. When the DO generator was used to increase the DO concentration in the pollutant solution treated by the microwave-assisted UV-TiO2 photocatalysis, the decomposition rate constant was highest among all the experimental conditions tested in this study. This result demonstrated that high concentration of DO can enhance the photocatalytic reaction rate by causing a synergistic effect of constituent techniques.

Contribution of Dissolved Oxygen to Methyl Orange Decomposition by Liquid Phase Plasma Processes System

Degradation of methyl orange (MO) in liquid phase plasma (LPP) was investigated. A bipolar pulsed power supply was used to generate discharges in the aqueous solution. Properties of generated plasma were investigated by electrical and optical emission spectroscopy methods. The MO decomposition rate increased with increasing levels of applied voltage, pulse width and frequency. The concentrations of activated species, including OH• radicals, were increased by the supply of DO. The concentration of OH• increased with increasing DO concentration up to 50 ppm. Further increase in the DO concentration, however, reduced the OH• concentration because of recombination of OH• radicals. The trend of MO decomposition rate with varying DO concentration was the same as that observed for the OH• concentration, suggesting that OH• radicals play a critical role in the decomposition of MO. Therefore, the LPP process for MO decomposition should be operated with an optimum DO concentration where the OH• radical concentration becomes highest.

Odors Removal by using Manganese Oxide Catalysts

The objective of this study was to assess the catalytic activities of manganese oxide (MnO, , , and ) catalysts for odors (acetaldehyde and propionaldehyde) removal. We used a fixed bed reactor as the experimental apparatus and the catalytic performance were carried out over the temperature range of . The properties and performance of catalysts were characterized by the X-ray diffraction (XRD) and Brunauer Emmett Teller (BET). The catalytic activities of manganese oxide catalysts for acetaldehyde combustion were in the order of MnO , and it is similar to that of propionaldehyde combustion. We also confirmed that the reactions have well followed the kinetic model of Power-Rate Law and the reaction order (n) is 1 for both of the acetaldehyde and propionaldehyde combustion. In addition, the reaction activation energy of acetaldehyde and propionaldehyde combustion over were found to be for 487~503 K and for 473~533 K, respectively.

Catalytic Characteristics of Mn-PC for VOCs Combustion

In this study, the catalytic activity of Mn-Phthalocyanine (Mn-PC) for VOCs (acetadehyde, propionaldehyde and toluene) combustion was determined. The reaction was carried out in a fixed bed reactor at the temperature range of . We investigated the physicochemical properties of Mn-PC before and after the pretreatment (air, , 1 hr, 60 cc/min) by TGA (Thermogravimetric Analyzer), BET (Brunauer Emmett Teller), EA (Elemental Analyzer), XRD (X-ray Diffractometer) and SEM (Scanning Electronic Microscope). By TGA analysis, 88 wt.% mass loss of Mn-PC was found at . The BET surface area of Mn-PC increased after the pretreatment. The decomposition and combustion of organic components in Mn-PC were observed by EA analysis. We also confirmed that Mn-PC had transformed into a new manganese oxide phase () after the pretreatment by XRD analysis. By SEM analysis, many of the micropores generated during the pretreatment were found. The catalytic activity of Mn-PC with the pretreatment for propionaldehyde combustion was higher than that of and fresh Mn-PC. It showed the catalytic activity of Mn-PC with the pretreatment for VOCs combustion by the order of toluene

Reduction of Fluoride in Water Phase by Micro-Nano Bubble Pretreatment Process

Fluoride is important to aquatic environment and health aspects, and the optimal fluoride concentration in water is below 1 mg/L. In this study, the micro-nano bubble pretreatment was applied to remove fluoride ions in the water phase. The pH control by calcium hydroxide (Ca(OH)₂), and coagulation processes with poly aluminum chloride (PAC), aluminum sulfate (Alum), F900 and two kinds of polymer named as A-polymer and A430P polymer were applied for the pretreated wastewater. In results, the combination of PAC and A430P polymer with micro-nano bubble pretreated wastewater showed a higher fluoride removal than the case of other combinations. In chemical oxygen demand (COD) removal, the combination of Alum and A430P polymer with micro-nano bubble pretreated wastewater showed the best removal efficiency (64.6%) while the COD removal without pretreatment was 71.4% for fluoride and 57.2% for COD.

Environmental Applications of Nano-Sized Recycled Aggregates: The Effect of Sterilization and Adsorption

To evaluate the sterilize efficiency of nano-sized recycled aggregates (RAs), several types of RAs were examined for the purpose of environmental stamping out procedure. The poultry (e.g., chicken) was selected as a target livestock of epidemic disease, and the blast furnace slag (BFS), fly ash (FA), slaked lime (SL), nano-cerium (n-Ce) and shell (Sh) were used as the RAs materials. The fermented solution of effective microorganisms (EM) was added to decompose the target livestock. Various kinds of lab-scale reactor were operated to examine the effects of RAs volume; high and low volume of RAs (e.g., 1.89 w/v% and 1.14 w/v% of RA in solution, respectively), and the effects of EM concentration (e.g., concentrated solution (100%) and diluted solution (12.5%)) with tested in different reaction time. The number of microorganisms after batch tests was counted for the sterilized effects of RAs, and organic matters (e.g., chemical oxygen demand (COD)) and inorganic matters (e.g., suspended solids (SS), heavy metals and potential ions) were analyzed before and after adsorption process. The cases of SL and n-Ce showed high removal of microorganism in the batch of high concentrated EM for 20 days. However the other RA materials were less effective on the sterilization especially in lower volume of RAs. In diluted EM (e.g., 12.5%) tests, most RAs have high sterilization efficiencies in the short periods of batch reaction regardless of RAs types, and it was more effective with longer reaction time. The BFS and n-Ce exhibited higher surface area than others and they adsorbed highly heavy metals in water. The results suggested that the concentration of target organism was the most important to determine sterilization and adsorption properties of RAs.

Nano-Sized Fume Biogas Production from Food Waster Using Semi-Continuous Anaerobic Digester

In this study, the nano-sized fume biogas production from food waste was investigated using lab scale semi-continuous stirred tank reactor (SCSTR) at 35 °C with 30d HRT and 30L working volume. The mesophilic digestion test was performed with three different feed materials (food waste) and food to microorganism (F/M) ratios (0.13, 0.34, and 0.27) in the same experiment. The results showed that the F/M ratios significantly affected the biogas production rate. The highest production rate was obtained at F/M ratio of 0.13. Nano-sized fume biogas produced in anaerobic digestion consists of 68.7% CH4, 31.2% CO2 and 30~200 nm particle. The average nano-sized fume biogas and methane production of digester were 29.96 L/Kg versus day-1 and 20.58 L/Kg versus day-1, respectively. The CH4 could be calculated as the heat energy 1.85 Kcal/Kg VS day-1. The digestion was operated without addition of chemicals or nutrients into the system.

Impact of Nano-Pore Structure in Harden Non-Sintering Cement.

This study investigates the nano pore structure of non-sintering cement (NSC) matrix. The result of pore structure properties showed no considerable difference in the total pore volume, but presented a large distinction in distribution of pore diameter by cement mixing ratio. The pore-diameter of NSC paste shows that occupation ratio of pore diameter below 10 nm was larger and was smaller than ordinary Portland cement (OPC) and blast-furnace slag cement (BSC) at pore diameter of over 10 nm. The reasons are due to the hydrate such as C-S-H gel and ettringite which formed dense nano pore structure of NSC matrix.