Papers by Author: Woo Keun Lee

Abstract: Significant amounts of fluorescent light have been discarded every year. Mercury is released into the atmosphere in the recycling process of it, if improperly treated. The adsorption method is used to remove mercury discharged from the recycling step of fluorescent light.We studied the impregnation condition of adsorbent made from sewage sludge. And also adsorption characteristics of mercury were evaluated by impregnated adsorbent.According to our results, the adsorption efficiency of mercury was increased by impregnating adsorbent with chlorine and iodine. The adsorption capacity was described by Langmuir isotherm model.

Abstract: In this work, pastes were prepared from slag and MSWI bottom ash by geopolymer technique. And its physical property was evaluated with mixing ratio of sodium silicate and potassium silicate. The amounts of leaching products, such as silica, alumina and calcium ions were changed for mixing ratio of raw materials. The compressive strength was increased with the increment of leaching amount of silica, alumina and calcium ions.

Abstract: Fe2O3 content affects the physical property of geopolymer paste made from waste materials. The effect of Fe2O3 was evaluated in this research. Geopolymer paste was made from the mixtures of mine tailing, melting slag, and alkali activator. Fe2O3 was added to discuss its effect with increasing the content. Compressive strength was 73.6 MPa without adding Fe2O3. But it was lowered to 32.5 MPa at the addition of 5wt. According to the analyzing results of XRD, SEM and EDS, Fe2O3 inhibited the geopolymer formation. Therefore, it is necessary to control the content of Fe2O3 to enhance the physical characteristics of geopolymer paste through the process of preparation.

Abstract: 8,285 tons/day of sewage sludge was discharged in 2009. Our study investigated improving sewage sludge’s recyclability by making lightweight bricks from it. The bricks’ compressive strength, specific gravity, water absorption and so on were measured to evaluate its characteristics. Its compressive strength ranged from 1.11 MPa to 10.92 MPa (3-class clay brick, the Korean standard, is 10.78 MPa or more). Its highest compressive strength was obtained at the mixing ratio of SS:MBA:BFS:WA = 6:1:1:2, and its range of specific gravity was 0.73–1.02 g/cm3. Heavy metal did not leach from it. Therefore, sewage sludge can be prepared and used to make lightweight brick.

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: Municipal Solid Waste Incinerator (below MSWI) ash is used to develop inorganic binder for preparing geopolymer concrete in this study. Toxic substituents, such as heavy metals are de-toxificated by above-mentioned new solidity technique. Slag and coal fly ash are used as active filler to enhance compressive strength. MSWI ash was mixed with slag and coal fly ash to make geopolymer concrete. They were solidified under alkali condition and dried at 50°C and 80°C, respectively. Compressive strength was measured to evaluate the characteristics of specimens for the period of 3, 7 and 14 days. Compressive strength measurements show a maximum strength of almost 13.7 MPa after 14 days. The mineral phases of specimen were analyzed by XRD. And the morphology was analyzed by the photo of SEM. The micro-structure of inorganic binder prepared was analyzed by FTIR. Korea Standard leaching Test (KSLT) and TCLP method are used to the environmental safety of inorganic binder. Raw FA measured concentrations of Cu and Pb were 0.30 ppm and 28.31 ppm, respectively. Leaching amounts of heavy metal were noticeably reduced after the solidification of MSWI as with active filler. It is possible to de-toxificate MSWI ash by new solidity techniques. And it may be used as alternative concrete.

Abstract: In this study, we investigate to use waste rock as a filler for filling the cavity of abandoned mines. We discuss that waste rock can be used as a filler in the side of environmental and structural stability. Waste rocks from four mines, such as Samgi, second Yeonwha, Dongwon and Dogye, are used. Leaching tests are conducted to check the environmental stability by four methods of Soil Leaching Test, MALT, TCLP and KSLT. According to the results, Cu, Cd, Cr and As were not detected and other metals leached below 0.5 ppm. Compressive strength of waste rock and crushed waste rock are measured to evaluate the structural stability. Mixtures of crushed waste rock are used to evaluate the possibility of enhancing compressive strength. Mixture 1 is composed of 11.1% of above 13.2mm, 22.2% of 9.5-13.2mm, 33.3% of 6.7-9.5mm, 22.2% of 3.5-6.7mm and 11.1% of 2.0-3.5mm. And mixture 2 is composed of 50% of above 13.2mm and 50% of 9.5-13.2mm. Compressive of the latter was more than that of the former. Waste rock can be probably used as a filler, considering the compressive strength of commercialized filler, or 40 Kg/cm2.

Abstract: The object of this study is to prepare adsorbents to remove heavy metals from abandoned mine residues. There are many factors that affect the adsorptivity of prepared adsorbents. The adsorptivity of prepared adsorbents is evaluated by cation exchange capatity(CEC). The maxium CEC value is obtained by Dongwon mine residues treated with NaOH. The optimum condition at that time is 75/25 wt% of mixing ratio of Dongwon mine residues and NaOH under N2 atmosphere at the activation temperature of 500°C. The CEC value was 95meq/100g at this condition. 99.5% of Pb was removed under the condition of 50 mg/L, pH 5 and reaction time of 1hr.

Abstract: Spent foundry sand (SFS) from cast iron industry mixed with loess was characterized to recycle spent foundry sand as ceramic support materials. Since SFS mostly consists of sand including binding agents and residue [1], it was used as permeable media, and loess, which has highly adsorptive and reactive properties, was used as support materials Leaching tests such as Korean Leaching Test (KLT) and TCLP (Toxicity Characteristics Leaching Procedure) showed that spent foundry sands from cast iron industry were not hazardous. Turbidity in furan sand was much higher than that in other sands, and turbidity was almost not changed with increasing amount of loess. The order of ORP (oxidation-reduction potential) in spent foundry sands was green sand > furan sand > CO2 sand. ORP was decreased with the amount of sand in furan sand and CO2 sand but was increased with the amount of sand in green sand. Hence, mixture of SFS and loess can be used as ceramic support materials with reductive or oxidative capability.