Papers by Author: Gi Chun Han

Abstract: Bottom ash generated from municipal solid waste incinerators in metropolitan areas contain calcium and aluminum compounds. As a result of a carbonation reaction, calcite and a calcium aluminum compound (Na6CaAl6Si6O24, Ca2Al2SiO7) as well as amorphous aluminum oxide can be found in bottom ash. Due to this, Cu and Pb leaching concentrations decrease via a carbonation process. Recently, the study of artificial carbonation reaction has been actively investigated, but most of these studies have been carried out utilizing an aqueous solution method with high water content. In this study, the carbonation reaction takes place in an aqueous environment, but does not occur on the surface of the particle. However, to cause the encapsulation of a particle with calcite, calcium aluminum compound and amorphous aluminum oxide, these must be formed on the surface of particle. Therefore in this study, a low water content encapsulation method of bottom ash from municipal solid waste incinerator was investigated with a view to immobilize Cu and Pb via a carbonation reaction. As seem in the results, the encapsulation effect appeared to be successful, with a water content of 20%.

Abstract: In this study, the degree of the substitution of Cr3+ and Cr6+ into the ettringite structure has been investigated to extent the immobilization potential of ettringite in the field under specific conditions. Aqueous suspension containing calcium hydroxide, alumium sulfate, CrCl2(trivalent chromium) and CrO3(hexavalent chromium) was subjected to ultrasound irradiation under atmospheric pressure to investigate their effects on synthesis of Cr-ettringite. In the result, the substitution of Cr3+ into Al site takes place in ettringite structure in solution with Cr3+, and monosulfate/friedel’ salt phase is also formed by occurrence of extra Al ion in solution. However, in the case of Cr6+, owing to a higher affinity of sulfate anion to form ettringite than that of Cr6+,
most of Cr6+ did not substituted into the crystal structure of ettringite.

Abstract: Bottom ash contains many ferrous materials (e.g. ferrous metals, Fe3O4, Fe2O3, FeS). In addition, ferrous metals include the heavy metals, as Ni and Cr have a chemical attraction to iron, with Cu used to coat with Ni and Cr metals for polishing or to prevent corrosion. For ferrous metals, the formation of a Fe3O4-Fe2O3 double layer (similar to pure Fe) was found during air-annealing in an incinerator (1000
C). A strong thermal shock, such as that which takes place during water-cooling of bottom ash, leads to the breakdown of this oxidation layer, facilitating the degradation of ferrous metals and the formation of corrosion products. Therefore, Fe-ion (heavy metal) oxides can be formed on ferrous metals, and magnetic separation can separate it from bottom ash. Thus, in this study the objection is to investigate the separation ratio of heavy metals by magnetic separation along with the mineralogical formation of Fe-ion (a heavy metal).

Abstract: Most carbonation processes utilizing municipal solid waste incineration bottom ash characteristically involve a high water content (over 100%). In this work, we developed an improved carbonation process, utilizing various water contents. In addition, we investigated the characteristics of a carbonation reaction using municipal solid waste incinerator bottom ash as a function of water content and their effects on the stabilization of copper and lead. As a result of such a carbonation reaction, the effect on the stabilization of heavy metals can be obtained. Due to this, the leaching concentrations of these were reduced. In a high water content, calcium aluminum compounds via carbonation reaction adsorbed Cu and Pb ions. Where a low water content (especially 30%) is present, particle surfaces are surrounded by calcium aluminum compounds of bottom ash as a result of the carbonation process. The leaching concentration of Cu and Pb were decreased through the carbonation process.

Abstract: In this paper, the application of wastes as raw materials to cementitious mineral was investigated. A rolling slag, which contains plenty of heavy metals, was used as a raw material to synthesize calcium sulfoaluminate. It was found that the suitable burning temperature of CSA clinker is between 1,250°C and 1,300°C, and the residual content of heavy metals in the CSA clinker turned out sequentially as Cu, Zn, Cr, and Pb. According to the results of the investigation, it is believed that a large amount of the Cu, Zn and Cr present in the raw materials were fixed in the CSA clinker formed during the sintering process. It was further found that the distortion of the crystal morphology of hydrate, which was ettringite, took place according to the substitution of heavy metals during the hydration process.

Abstract: This study focused on the synthesis of zeolite from coal bottom ash and the CEC assessment of synthesized products. To that end, zeolificaion tests were carried out at four temperature levels (80, 100, 120, 150oC) and five NaOH concentration levels (1, 2, 3, 4, 5M) by the alkali hydrothermal method. Consequently, NaP1, hydroxy-sodalite, and tobermorite were produced from coal bottom ash. NaP1 with an excellent cation exchange capability had a high crystallinity at below 2M NaOH and 120 oC; and the maximum CEC value was 160meq/100g at 2M NaOH and 120 oC under the given conditions.