Papers by Author: Yeong Seok Yoo

Abstract: In this study, composition for bottom ash and fly ash of MSWI was analyzed and zeolite was synthesized in order to expand its recycling on high quality and mass consumption. Analysis of ash its characteristics was performed by XRF, XRD, SEM, EDX, TG/DTA. Bottom/fly ash was fired for elimination of unburned carbon at 750°C/12 hr, crushed and synthesized to zeolite in 1, 2, 3, 4, 5 M NaOH solutions under 105°C/24hr by hydrothermal method. Calcite and calcium-silicate compound was mainly contained in bottom ash and CaCl₂∙4H₂O, Ca (OH)₂, NaCl, and calcite and KCl in fly ash. Especially amount of Cl was much contained in fly ash due to Korean food waste characteristics. Bottom ash could synthesize Zeolites in form of sodalite under 3~4 M NaOH and fly ash could synthesize Zeolite A under 1~2 M NaOH. In addition, zeolite synthesized with bottom ash had higher specific surface area and zeolite from fly ash had higher CEC value. Accordingly, ash from MSWI could be recycled for further valuable uses such as non-point pollutant control and/or soil amendment.

Abstract: In this study, carbonized porous media was manufactured using sewage sludge and analyzed for pollutants removal characteristics. Sewage sludge produced by activated sludge sewage treatment contained much organics to be carbonized, so it was mixed with other mixtures, extruded and formed in ∅ 5~10 mm ball shape, and sintered at 900°C and 1 hour in furnace for carbonization under N₂ purge. The characteristics of the porous media was BET 35 m²/g and average pore size 39.3Å, pore volume 0.0092 cm³/g, Iodine number 45.9 and bulk density 0.91 cm³/g. Experiments were performed for SS, phosphate, nitrate and heavy metals (Cu, Zn). Its removal characteristics of SS and fertilizer components were compared with gravel’s used in filtration and its heavy metals removal was characterized by derivation of its adsorption equilibrium equations. In result, the carbonized porous media could be utilized as massive adsorption media for pollutant removal or fertilizer adsorption in fields of roof planting or non-point source pollutants control.

Abstract: This study was carried out to investigate adsorption characteristics on NO2 and SO2 for two kinds of media, ie the carbonated media and its zeolite coated media with sewage sludge. Porous media was manufactured through processes of drying, extruding, forming, carbonation and washing. Zeolite was coated on the media, and then thermally treated. Test of NO2 and SO2 removal was peformed by detecting NO2 and SO2 concentration at inlet and outlet of the reactor continuously flowing the mixed gas. Zeolite coated media showed higher than carbonization media in removal efficiency of NO2 and SO2. Also, zeolite coated media took shorter time for achieving in 84% removal of SO2 than carbonated media. And, zeolite coated media showed that removal efficiency of NO2 and SO2 maintained high in early stage as well as time elapsing. It make possible the zeolite coated media remove SO2 and NO2 for long time. As a result, micro pore in zeolite could increase breakthrough time and adsorption capability, compared to macro pore in carbonated media. Zeolite coating on porous media would be effective on removal of SOx and NOx.

Abstract: Natural soil would be used for planting on paved area ground, but it had been replaced by the light weighted artificial soil to minimize burden of the structure. But, the existing light weighted soil had nearly capacity of fertilizer adsorption due to its glassy surface. In this study, the artificial soil prepared by sewage sludge was manufactured, tested characteristics as soil and examined on planting. The developed soil was analyzed through specific gravity, pH, water content, volatile matter and was tested on adsorption capacity of Cu. In addition, planting examination analyzed the leaf growth of planting and mouseear cress plant's pollen. As the result, the developed artificial soil showed to be color yellowish brown, bulk density 0.6g/cm3, pH 8~9, volatile matter 0.3, CEC 10, pressure strength 25 ton/m2, hydrophilic and non-toxic, which was suitable for rooftop gardening. Also, periodic growth rate and development of leaves was satisfactory as natural soil and growth and numbers of pollens were good. Consequently, the developed artificial soil with porosity and capacity of fertilizer adsorption could be usefully applicable to planting on the paved area.

Abstract: The objective of this research was to make brick from waste materials, such as MSWI fly ash, water sludge and coffee sludge. It was made by mixing raw materials, drying at room temperature for 24 hrs, and at 60°C ~ 100°C for 1hrs. The dried bricks sintered to 1100 ~ 1150°C by 5°C/min and then kept at that temperature for 2hrs. Compressive strength, water absorption were measured to discuss the characteristics of brick prepared. Toxicity characteristic leaching procedure(TCLP) test is also used to evaluate the environmental safety. The optimum condition was obtained at the mixing ratio as followed; 20:19.5:0.5:60 of MSWI fly ash, water sludge, coffee sludge and clay. Considering the value of compressive strength and water adsorption for prepared brick, it can be used as an alternative brick.

Abstract: In this work, inorganic paste was made from melting slag (MS) of MSWI ash and MSWI bottom ash (MBA) by geopolymer technique. Heavy metals such as Pb and Cu are highly contained in MBA. In the view of environmental protection and resource conservation, recycling of MSWI ash is desirable. MS and MBA were mixed to make inorganic paste. Compressive strength was measured to evaluate the characteristics of inorganic paste after the period of 1, 3 and 7day. Compressive strength of almost 90 MPa was obtained at the mixing ratio of MS : MBA = 9 : 1. And the crystalloid and crystal structure was analyzed by FTIR and XRD. Korea Standard leaching Test (KSLT) is also used to evaluate the environmental safety of inorganic paste. The leached concentration of Pb and Cu were 0.44 ppm and 0.15 ppm, respectively. According to this result, heavy metals were safety immobilized and stabilized.

Abstract: Zeolite has been used as catalyzer, absorbent, ion-exchange matter and dehydrating agent due to its excellent catalytic property and ion-exchange. In recent years, many studies have been conducted to apply zeolite as new materials such as zeolite membranes and zeolite sensor films. To introduce properties of zeolite, it should be examined how zeolite could be reacted other materials. In this study, it is investigated whether zeolite is successfully synthesized or not when clay and/or sewage sludge coexist with zeolite precursor. Zeolite precursor was made of liquid sodium silicate and sodium aluminate. Mixing ratio of caly and/or sewage sludge is 0-10%(wt.). To compare two processes, the mixture was synthsized by hydrothermal method and high temperature sintering process. It is synthesized by hydrothermal with sintering at high temperature process. The resulting materials were characterized by XRD and SEM. As a result, various type of zeolite such as zeolite X, zeolite A and zeolite P1 was successfully synthesized by hydrothermal method when clay and/or sewage coexist with zeolite precursor. However, zeolite was rarely synthesized by high temperature sintering process. Therefore, when preperation of zeolite material mixed with other material such as clay and sewage sludge, hydrothermal method is more effective than sintering at high temperature process.

Abstract: Zeolite are used as adsorbent, catalyst and ionexchang material. But it limited to extend the usage of the zeolite since almost zeolite synthesized by hydrothermal method. The purpose of this study was to synthesis zeolite by calcination at high temperature due to extend the application of zeolite, as ceramics process. The effect of aging temperature and time, crystallization temperature on the synthesis of zeolite has been studied. Aging was performed at room temperature~70°C during 0~3days. After aging, zeolite precursor sinter for 1 hours at 300, 400, 500°C in furnace. The resulting materials were characterized by XRD, TG, SEM When the aging time is less than 1 day zeolite was not synthesized. But zeolite A obtained from precursor of aging time is more than 1 day at all firing temperature. As a result the aging time and aging temperature is increased, the zeolite synthesis time is decreased. Therefore aging is benefit process on synthesis of zeolite at high temperature.

Abstract: This study was conducted to synthesize zeolitic materials using sewage sludge by molten-salt method the effective method was investigate to reduce the thermal treatment time by adding zeolite seed and excessive sodium hydroxide. To synthesis zeolitic materials, sewage sludge was used as Si and Al sources, also Na2SO4 and NaOH were added as stabilizer and mineralizer respectively. Sewage sludge was prepared by calcination at 550°C/3hr to remove organic materials. As a result of thermal treatment at 950°C for 6~24hrs, more than 18 hours was required to synthesize zeolitic materials without adding zeolite seed. On the other hand, it is observed that hydroxyl-sodalite was synthesized in 9 hours thermal treatment and Na-P1 also in 12 hours when zeolite seed was added, but no other differences were observed when excessive sodium hydroxide was added. Consequently, the overall reaction time required could be reduced by adding zeolite seed and changing thermal treatment temperature. However, addition of NaOH does not show significant effect on the reduction of zeolite synthesis time.

Abstract: This study is about the development of porous material which shapes Ø3~8mm bead with sewage sludge by molten-salt method. The development of porous material was conducted by 2 different processes. One is made by molding sewage sludge into beads with pelletizer and then coating the beads with molten-salt and lastly sintered at 1050°C, and the other is mixing sewage sludge with molten-salt which is using synthesized zeolite, and then molding the mixture into beads with pelletizer. The molded mixture is finally sintered at 1050°C. We evaluated the value of developed material as sorbent and artificial soil for tree-planning by analyzing surface area, distribution of pore size, and cation exchange capacity(CEC). According to the results, surface coated porous material have 92.8m2/g of surface area and CEC 98.9meq/100g and the mixture sewage sludge with molten-salt have 104.1m2/g of surface area and CEC 140.8meq/100g. Thus, developed porous material can be applied to various uses as sorbent and artificial soil.