Seung Jai Kim

A study of photocatalysis of TiO2 coated onto chitosan beads and activated carbon

Titanium dioxide has been thought of as a safe, effective light scatterer which is widely used in cosmetics, sunscreens, and even food as a whitening agent. The development of environmental purification technology using a TiO2 photocatalyst, which removes organic contaminants by forming OH radicals through redo reactions, has recently attracted great attention. While TiO2 is chemically activated when exposed to UV light in sunlight or a fluorescent lamp, it generates strong oxidization and deoxidization. In addition, TiO2 is used for various purposes because of its properties, such as not melting neither in acid nor alkaline conditions, generating great photochemical stability and strong oxidization, and has a wide range of application in industries. TiO2 can be easily found around us in wide usage such as a whitening pigment. In addition, there are many experiments going on in various areas using its properties such as disassembling of organic compounds, sterilizing, deodorizing and purifying water. Salmonella choleraesuis subsp. is an important component of the porcine respiratory disease complex (PRDC). The recognition of S. choleraesuis subsp. as an important and common cause of swine respiratory disease and the emergence of porcine reproduction and respiratory syndrome (PRRS) as a new swine disease have both occurred only relatively recently. The objective of this study was to evaluate the effect of bactericidal agents in the presence of TiO2 on selected typical food bacteria, S. choleraesuis subsp. However, TiO2 powder could not be used satisfactorily due to its poor separability from the suspension and flowability. Therefore, in this experiment TiO2 was coated on activated carbon and chitosan beads for the easy recovery of the photocatalyst from the system after photo-reactions. We established the response surface methodology (Box–Behnken design) to investigate the principal parameters such as TiO2 concentration, UV illumination time, temperature and pH for their influence on cell death. According to the result of the experiment, it was found that TiO2 is a strong anti-bacterial agent against S. choleraesuis subsp.

Characterization of PM2.5 aerosols dominated by local pollution and Asian dust observed at an urban site in Korea during aerosol characterization experiments (ACE)--Asia Project.

Abstract Daily fine particulate matter (PM2.5) samples were collected at Gwangju, Korea, during the Aerosol Characterization Experiments (ACE)–Asia Project to determine the chemical properties of PM2.5 originating from local pollution and Asian dust (AD) storms. During the study period, two significant events occurred on April 10–13 and 24–25, 2001, and a minor event occurred on April 19, 2001. Based on air mass transport pathways identified by back-trajectory calculation, the PM2.5 dataset was classified into three types of aerosol populations: local pollution and two AD aerosol types. The two AD types were transported along different pathways. One originated from Gobi desert area in Mongolia, passing through Hunshandake desert in Northern Inner Mongolia, urban and polluted regions of China (AD1), and the other originated in sandy deserts located in the Northeast Inner Mongolia Plateau and then flowed southward through the Korean peninsula (AD2). During the AD2 event, a smoke plume that originated in North Korea was transported to our study site. Mass balance closures show that crustal materials were the most significant species during both AD events, contributing ~48% to the PM2.5 mass; sulfate aerosols (19.1%) and organic matter (OM; 24.6%) were the second greatest contributors during the AD1 and AD2 periods, respectively, indicating that aerosol properties were dependent on the transport pathway. The sulfate concentration constituted only 6.4% (4.5 µg/m3) of the AD2 PM2.5 mass. OM was the major chemical species in the local pollution-dominated PM2.5 aerosols, accounting for 28.7% of the measured PM2.5 mass, followed by sulfate (21.4%), nitrate (15%), ammonium (12.8%), elemental carbon (8.9%), and crustal material (6.5%). Together with substantial enhancement of the crustal elements (Mg, Al, K, Ca, Sc, Ti, Mn, Fe, Sr, Zr, Ba, and Ce), higher concentrations of pollution elements (S, V, Ni, Zn, As, Cd, and Pb) were observed during AD1 and AD2 than during the local pollution period, indicating that, in addition to crustal material, the AD dust storms also had a significant influence on anthropogenic elements.

Simultaneous removal and recovery of cadmium and cyanide ions in synthetic wastewater by ion exchange

Simultaneous removal and recovery of cyanide and cadmium ions using a strong-base anion exchange resin was studied on the basis of formation of Cd-CN complexes at high pH in synthetic wastewater containing cyanide and cadmium ions. Strong-base anion exchange resin particles, of Dowex1X8-50, were contacted with synthetic aqueous solutions. For different molar ratios between cyanide and cadmium, ion exchange characteristics of cadmium-cyanide complexes were studied experimentally in a batch reactor. Treatment efficiencies of packed and fluidized beds were compared under various conditions. Several regenerants, NaSCN, NaCN, and NaOH, were used to regenerate the exhausted resin. The rates of regeneration and recovery for the various regenerants were estimated and discussed. The resin used in this work, Dowex1X8-50, can exchange about 6.6 CIST meq./g resin and 3.2 Cd2+ meq./g resin of cyanide and cadmium ions as complexes, respectively. Free cyanide ion has a lower selectivity than Cd-CN complexes on the anion exchange resin. The degree of treatment efficiency applied in this study was greater in the fluidized bed than packed bed. NaSCN was the best regenerant among regenerants used for regeneration of resin saturated with Cd-CN complexes.

Adsorption Equilibrium Characteristics of 2,4-Dichlorophenoxyacetic Acid and 2,4-Dinitrophenol on Granular Activated Carbons

Adsorption characteristics of 2,4-Dichlorophenoxyacetic acid (2,4-D) and 2,4-Dinitrophenol (2,4-DNP) onto granular activated carbon (GAC) were studied to obtain basic information on their removal from aqueous solution. Single component adsorption equilibria of 2,4-D and 2,4-DNP dissolved in water have been measured for three kinds of GACs (F400, SLS103, and WWL). In case of 2,4-D, the magnitude of adsorption capacity was in the order of F400> SLS103>WWL, and that for 2,4-DNP was SLS103> F400> WWL. The influence of temperature and initial pH of aqueous solution on adsorption has been discussed in detail by using the Sips equation.

Adsorption of chlorinated volatile organic compounds in a fixed bed of activated carbon

Adsorption isotherms of dichloromethane and 1,1,2-trichloro-1,2,2-trifluoroethane on an activated carbon pellet, Norit B4, were studied. For these chemicals, the Sips equation gave the best fit for the single component adsorption isotherm. The adsorption affinity on activated carbon was greater for dichloromethane than that of 1,1,2-trichloro-1,2,2-trifluoroethane. An experimental and theoretical study was made for the adsorption of dichloromethane and 1,1,2-trichloro-1,2,2-trifluoroethane in a fixed bed. Experimental results were used to examine the effect of operation variables, such as feed concentration, flow rate and bed height. Intraparticle diffusion was able to be explained by a surface diffusion mechanism. An adsorption model based on the linear driving force approximation (LDFA) was found to be applicable to fit the experimental data.

Effect of pH on adsorption of 2,4-dinitrophenol onto an activated carbon

The adsorption characteristics of 2,4-dinitrophenol from water onto a granular activated carbon, F-400, were studied at pH 4.3, 7 and 10. Adsorption equilibria of 2,4-dinitrophenol on GAC could be represented by Sips equation. Equilibrium capacity increased with decreasing pH. The differences in the rates of adsorption are primarily attributable to the differences in the equilibrium at the various pHs. Intraparticle diffusion was explained by surface diffusion mechanism. An adsorption model based on the linear driving force approximation (LDFA) was used for simulating the adsorption behavior of 2,4-dinitrophenol in a fixed bed adsorber.

Removal and recovery of heavy metal ions in fixed and semi-fluidized beds

Uptakes of heavy metal ions such as Pb2+ and Ni2+ were studied experimentally in fixed and semifluidized beds packed with a strong cation exchange resin, Amberlite 200. Single and binary aqueous solutions of lead and nickel ions were passed through ion exchange columns, and the exit concentrations were measured to get the breakthrough behavior of the ions. From the exit concentration profiles, the breakthrough time and the ion exchange capacity were evaluated. After removal of heavy metal ions from binary solution of lead and nickel ions until the breakthrough time, two metal ions were recovered by precipitation and resolubilization of lead. In this paper, the recovery yield and separation efficiency are rigorously discussed.

Preparation of a clinoptilolite-type korean natural zeolite

A clinoptilolite-type natural zeolite was pretreated by HC1, NaOH, and NaCl solutions to improve the ion-exchange capacities for heavy metal ions such as copper, lead, cadmium, and cesium. The pretreated natural zeolite was experimentally investigated based on chemical analyses, X-ray diffraction, and BET experiments etc. From experimental data, it was shown that the pretreatment with NaCl gave the best ion-exchange capacity for all metal ions encountered. The ion-exchange capacity of the NaCl-treated sample is comparable with that of a commercialized natural zeolite, chabazite. On the other hand, the HCl-treated sample has very low ion-exchange capacities for all metal ions even though it has high specific surface area and total pore volume. It was proven by chemical analyses that a strong acid like HC1 can damage the structure of the zeolite by extracting aluminum and iron from their skeletal units.

Particle velocity and circulation rate in liquid spouted beds

In this work, the particle velocity and circulation rate in water spouted beds of small glass particles are experimentally studied. The pathline, velocity and residence time of particles 0.53 to 1.40 mm in diameters were measured in the annulus of half-cylindrical columns 40, 60 and 90 mm in diameters. The particle velocity in the annulus and circulation rate increase practically linearly with fluid flowrate. As the column diameter was increased, the average particle velocity in the annulus was decreased, but the particle circulation rate was increased.

A Study of Adsorption Behavior of 2,4-Dichlorophenoxyacetic Acid onto Various GACs

Adsorption and desorption of 2,4-dichlorophenoxyacetic acid (2,4-D) onto granular activated carbon (GAC) were studied to get basic information on their removal from aqueous solution. Single species adsorption equilibria of 2,4-D dissolved in water have been measured using F400, SLS103, and WWL. Equilibrium capacity increased with decreasing pH. The magnitude of adsorption capacity of 2,4-D was the order of F400> SLS103>WWL. Kinetic parameters were measured in a batch adsorber to analyze the adsorption rate of 2,4-D. The internal diffusion coefficients were determined by comparing the experimental concentration curve with that predicted from the surface diffusion model (SDM) and Pore diffusion model (PDM). The linear driving force approximation (LDFA) model was used to simulate isothermal adsorption behaviors in a fixed bed adsorber and successfully simulated experimental adsorption breakthrough behavior under various operation conditions.