Gi-Chun Han

Environmental Remediation and Conversion of Carbon Dioxide (CO2) into Useful Green Products by Accelerated Carbonation Technology

This paper reviews the application of carbonation technology to the environmental industry as a way of reducing carbon dioxide (CO2), a green house gas, including the presentation of related projects of our research group. An alternative technology to very slow natural carbonation is the co-called ‘accelerated carbonation’, which completes its fast reaction within few hours by using pure CO2. Carbonation technology is widely applied to solidify or stabilize solid combustion residues from municipal solid wastes, paper mill wastes, etc. and contaminated soils, and to manufacture precipitated calcium carbonate (PCC). Carbonated products can be utilized as aggregates in the concrete industry and as alkaline fillers in the paper (or recycled paper) making industry. The quantity of captured CO2 in carbonated products can be evaluated by measuring mass loss of heated samples by thermo-gravimetric (TG) analysis. The industrial carbonation technology could contribute to both reduction of CO2 emissions and environmental remediation.

Leachability of Arsenic and Heavy Metals from Mine Tailings of Abandoned Metal Mines

Mine tailings from an abandoned metal mine in Korea contained high concentrations of arsenic (As) and heavy metals [e.g., As: 67,336, Fe: 137,180, Cu: 764, Pb: 3,572, and Zn: 12,420 (mg/kg)]. US EPA method 6010 was an effective method for analyzing total arsenic and heavy metals concentrations. Arsenic in the mine tailings showed a high residual fraction of 89% by a sequential extraction. In Toxicity Characteristic Leaching Procedure (TCLP) and Korean Standard Leaching Test (KSLT), leaching concentrations of arsenic and heavy metals were very low [e.g., As (mg/L): 0.4 for TCLP and 0.2 for KSLT; cf. As criteria (mg/L): 5.0 for TCLP and 1.5 for KSLT].

Effect of Hydraulic Activity on Crystallization of Precipitated Calcium Carbonate (PCC) for Eco-Friendly Paper

Wt% of aragonite, a CaCO3 polymorph, increased with higher hydraulic activity (°C) of limestone in precipitated calcium carbonate (PCC) from the lime-soda process (Ca(OH)2-NaOH-Na2CO3). Only calcite, the most stable polymorph, was crystallized at hydraulic activity under 10 °C, whereas aragonite also started to crystallize over 10 °C. The crystallization of PCC is more dependent on the hydraulic activity of limestone than CaO content, a factor commonly used to classify limestone ores according to quality. The results could be effectively applied to the determination of polymorphs in synthetic PCC for eco-friendly paper manufacture.

Neutralizing capacity of bottom ash from municipal solid waste incineration of different particle size

This study measures the neutralizing capacity of bottom ash from municipal solid waste incineration of different particle sizes. We examine the effect of particle size on the weathering process, a method popularly used for stabilization of heavy metals in incineration of bottom ash. The distribution of particle sizes in municipal solid waste incineration bottom ash is rather broad, ranging from fine powder to as large as 40 mm in diameter. Although considered a by-product highly suitable as a road construction material, the high level of heavy metal leaching is an obstacle to its reuse. Weathering, a method used to reduce heavy metal leaching, is a lengthy process taking over thee months to complete. The chief reaction involved in weathering is carbonation occurring between Ca(OH)2 in bottom ash and CO2(g) in the atmosphere. During this process, CaCO3 is produced, causing the pH level to drop from over 12 to about 8.2 and reducing heavy metal leaching. In this paper, we attempt to determine the particle size best suited for reducing the period required for weathering bottom ash by identifying characteristics of different particle sizes that affect heavy metal leaching and neutralization.

Effect of Carbonation in Removal of Chloride from Municipal Solid Waste Incineration Bottom Ash

ABSTRACT Most of chloride in municipal solid waste incineration bottom ash are easily soluble in water. As a reason of that, bottom ash limited its use as a road materials and cement contrete as well as landfill. Thus, the characteristic of chloride in bottom ash was investigated, though the distribution of chloride from based on particle size, characteristic of friedels salt(3CaO•Al2O3• CaCl2•10H2O) in bottom ash and the removal of friedels salt via caibonation process. As a result, the content of chloride was increased with the smaller particle size, especially friedels salt too. The soluble chloride like KCl, NaCl in bottom ash was possible to be removed by washing process, reversely friedels salt (insoluble) was difficult. But friedels salt could be removed via carbonation process because that has difficulties of preventing progressive carbonation and in controlling the activity of CO2.

Recovery of Aggregates from Waste Concrete by Heating and Grinding

ABSTRACT This research virus carried put to recycle the aggregates in the waste concrete. The recycled aggregates below 25 mm produced by the company I. a construction waste processing company were divided into several pans. According as the particle size was decreased, the amount of cement mortar, absorption ratio and abrasion ratio of recycled aggregate were increased. When they were heated at 200~500°C and ground by ball mill, the amount of cement mortar separated from the recycled aggregates was increased according to increase in temperature. When the aggregates such as granite and gneiss were heated above 550°C, their compressive strength was declined for α-SiO2 contained in them was transformed into β-SiO2. Thus, the waste concrete was heated at 400~500°C and ground by ball mill for 1 hr not to deteriorate the aggregate in concrete. As a result, the specific gravity, the absorption ratio, and the abrasion ratio of the aggregates become above 2.5, below 3.0%, and below 40%.

Identification of Calcium Sulphoaluminate Formation between Alunite and Limestone.

This study was carried out to identify the conditions of formation of calcium sulphoaluminate (3CaO·3Al2O3·CaSO4) by the sintering of a limestone (CaCO3) and alunite [K2SO4·Al2(SO4)3·4Al(OH)3] mixture with the following reagents: K2SO4, CaCO3, Al(OH)3, CaSO4·2H2O, and SiO2. When K2SO4, CaCO3, Al(OH)3, CaSO4·2H2O were mixed in molar ratios of 1:3:6:3 and sintered at 1,200∼1,300 °C, only 3CaO·3Al2O3·CaSO4 and calcium langbeinite (2CaSO4·K2SO4) were generated. With an amount of CaO that is less than the stoichiometric molar ratio, 3CaO·3Al2O3·CaSO4 was formed and anhydrite (CaSO4) did not react and remained behind. With the amount of CaSO4 that is less than the stoichiometric molar ratio, the amounts of 3CaO·3Al2O3·CaSO4 and 2CaSO4·K2SO4 decreased, and that of CaO·Al2O3 increased. In the K2SO4-CaO-Al2O3-CaSO4-SiO2 system, to stabilize the formation of 3CaO·3Al2O3·CaSO4, 2CaSO4·K2SO4, and β-2CaO·SiO2, the molar ratios of CaO: Al2O3: CaSO4 must be kept at 3:3:1 and that of CaO/SiO2, over 2.0; otherwise, the generated amount of 3CaO·3Al2O3·CaSO4 decreased and that of gehlenite (2CaO·Al2O3·SiO2) with no hydration increased quantitatively. Therefore, if all SO3(g) generated by the thermal decomposition of alunite reacts with CaCO3 (or CaO, the thermal decomposition product of limestone) to form CaSO4 in an alunite- limestone system, 1 mol of pure alunite reacts with 6 mol of limestone to form 1 mol of 3CaO·3Al2O3·CaSO4 and 1 mol of 2CaSO4·K2SO4.

Change of Mineral Phases in Carbonation Reaction of MSWI Bottom Ash

ABSTRACT Municipal solid waste incineration(MSWI) bottom ash consists of glassy materials, ceramics, ferrous materials mainly. Therefore, in some European countries, it is used as construction material. But, the bottom ash is more considered as a chemically reactive material that releases hazardous heavy metals. In order to manage the bottom ash, understanding of the carbonation process is necessary. Because their influence on carbonation reaction in bottom ash may has a significant effect on the leaching characteristics of contaminants such as heavy metals. To gain a proper appreciation of the carbonation role of mineral constituent in bottom ash, it is essential to understand the relationships between their morphology, composition and their influence on carbonation reaction. Therefore, we carried out the study on mineral constituent of bottom ash and their influence on carbonation reaction.

Recovery of ferromagnetic material by wet magnetic separation in coal bottom ash

ABSTRACT A coal ash generated from a coal-fired power plant largely divided into fly ash and bottom ash. All of the coal fly ash has been recycled and the coal bottom ash (CBA) in only a part restricted within narrow field. But, many researchers have investigated the study about recycling of CBA by physical separation because it has various materials such as silicate, aluminate, unburned carbon and magnetic-substance. For example, it is easy to be removed by magnetic separation in the case of magnetic-substance contained in CBA. Thus, we investigated the recovery of ferromagnetic material by wet magnetic separation in CBA. For this study, we researched the recovery rate of ferromagnetic material, such as iron and magnetite through wet magnetic separator at various magnetic forces and confirmed the distribution of ferromagnetic material as a various particle size.

Effects of Leaching of Heavy Metals in Cement-based Recycling via Carbonation of Municipal Solid Waste Incineration Bottom Ash

ABSTRACT The paper describes the effect of replacing part of Portland cement with municipal solid waste incineration (MSWI) bottom ash with various treatments such as washing and carbonation. MSWI bottom ash was subjected to washing or carbonation treatment to reduce the chloride content and expansion property. And mortars using each bottom ash were manufactured. Results showed that MSWI bottom ash is potentially attractive as mineral addition if chloride is removed and aluminium particles are stabilized.