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The brief review on Coal origin and distribution of rare earth elements in various Coal Ash Samples
Ramakrishna, Chilakala,Thenepalli, Thriveni,Nam, Seong Young,Kim, Chunsik,Ahn, Ji Whan The Korean Society for Energy 2018 에너지공학 Vol.27 No.2
Rare earth elements together with Y and Sc (REEs) are essential in the development of technology for clean and efficient use of energy. In recent years coal deposits have much attention and attracted as a promising alternative raw sources for rare earth elements, not only because the REEs concentrations in many coals or coal ashes are equal to or higher than those found in conventional types of REEs ores but also because of the world wide demand for REEs in recent years has been greater than supply. In the coal ashes, REEs are mainly associated with carbonates, silicates and aluminosilicates in ashes at 800 and $1100^{\circ}C$. These elements are known to be powerful environmental tracers in natural biogeochemical compartments. In this study, to reviewed the REEs originating and distribution patterns in coal ash samples from the bedrock and/or soil weathering that were entrapped by lichens and mosses was investigated. The REEs patterns of different organisms species allowed minor influence of the species to be highlighted compared to the regional lithology.
Ramakrishna, Chilakala,Thenepalli, Thriveni,Huh, Jae-Hoon,Ahn, Ji Whan The Korean Ceramic Society 2016 한국세라믹학회지 Vol.53 No.1
In this paper, we have developed a simple, new and economical carbonation method to synthesize a pure form of aragonite needles using dolomite raw materials. The obtained aragonite Precipitated Calcium Carbonate (PCC) was characterized by XRD and SEM, for the measurement of morphology, particle size, and aspect ratio (ratio of length to diameter of the particles). The synthesis of aragonite PCC involves two steps. At first, after calcinated dolomite fine powder was dissolved in water for hydration, the hydrated solution was mixed with aqueous solution of magnesium chloride at $80^{\circ}C$, and then $CO_2$ was bubbled into the suspension for 3 h to produce aragonite PCC. Finally, aragonite type precipitated calcium carbonate can be synthesized from natural dolomite via a simple carbonation process, yielding product with average particle size of $30-40{\mu}m$.
( Ramakrishna Dadigala ),( Rajkumar Bandi ),( Chan-woo Park ),( Song-yi Han ),( Azelia Wulan Cindradewi ),( Jeong-ki Kim ),( Gu-joong Kwon ),( Seung-Hwan Lee ) 한국목재공학회 2021 한국목재공학회 학술발표논문집 Vol.2021 No.2
Preparation of Pd nanoparticles (PdNPs) on cellulose nanofibrils (CNF) by a rapid microwave approach is reported here. Variation of solution pH revealed that the neutral pH is optimal for the maximum adsorption of Pd<sup>2+</sup> ions on CNF surface. Subsequent reduction of Pd<sup>2+</sup> ions was achieved using ethylene glycol (EG) as reducing agent under microwave irradiation. Effect of EG amount and microwave irradiation time was also studied. Comparative experiments under conventional heating revealed that 2 h of time is required for complete reduction whereas the microwave irradiation offered in just 120 s. In transmission electron microscopic images PdNPs exhibited spherical morphology and homogenously deposited on CNF with uniform size distribution. Binding interactions between PdNPs and CNF were studied by fourier transform infrared and x-ray photoelectron spectroscopy analysis. X-ray diffraction patterns unveiled the face centered cubic (FCC) crystal structure of PdNPs. Peroxidase mimicking activity of the nanohybrid (PdNPs/CNF) was studied by catalyzing the H<sub>2</sub>O<sub>2</sub> mediated oxidation of 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). Change in the solution color from colorless (ABTS) to blue (ox-ABTS) provides a visual sensing platform for the rapid detection of toxic chemicals and biomolecules.
Extraction of Precipitated Calcium Carbonate from Oyster Shell waste and Its Applications
Ramakrishna, Chilakala,Thenepalli, Thriveni,Nam, Seong Young,Kim, Chunsik,Ahn, Ji Whan The Korean Society for Energy 2018 에너지공학 Vol.27 No.1
In this paper, we reported that the influence of advanced functional mineral filler calcium carbonate ($CaCO_3$) extracted from oyster shell waste, which are rich mineral sources of $CaCO_3$. Oyster Shells, available in abundance, have no eminent use and are commonly regarded as waste. Their improper disposal causes a significant level of environmental concern and also results in a waste of natural resources. Recycling shell waste could potentially eliminate the disposal problem, and also turn an otherwise useless waste into high value added products. Oyster shell waste calcination process to produce pure lime (CaO) which have good anti-microbial property for waste water treatment and then focuses on its current applications to treat the coffee waste and its effluents for biological treatment and utilization as a fertilizers.
Ramakrishna., CH,Thriveni., T,Nam, Seong Young,kim, Chunsik,Ahn, Ji Whan The Korean Society for Energy 2017 에너지공학 Vol.26 No.4
Coal-fired power plants supply roughly 50 percent of the nation's electricity but produce a disproportionate share of electric utility-related air pollution. Coal combustion technology can facilitate volume reduction of up to 90%, with the inorganic contaminants being captured in furnace bottom ash and fly ash residues. These disposal coal ash residues are however governed by the potential release of constituent contaminants into the environment. Accelerated carbonation process has been shown to have a potential for improving the chemical stability and leaching behavior of bottom ash residues. The aim of this work was to quantify the volume of $CO_2$ that could be sequestrated with a view to reducing greenhouse gas emissions and stabilize the contaminated heavy metals from bottom ash samples. In this study, we used PC boiler bottom ash, Kanvera reactor (KR) slag and calcined waste lime for measuring chemical analysis and heavy metals leaching tests were performed and also the formation of calcite resulting from accelerated carbonation process was investigated by thermo gravimetric and differential thermal analysis (TG/DTA).
Ramakrishna, Chilakala,Thenepalli, Thriveni,Nam, Seong Young,Kim, Chunsik,Ahn, Ji Whan The Korean Society for Energy 2018 에너지공학 Vol.27 No.1
In this paper, we investigated the alternative sources of limestone. Oyster shell waste originated from aquaculture that causes a major disposal landfill problem in coastal sectors in southeast Korea. Their inadequate disposal causes a significant environmental problems araised. Bio mineralization leads to the formation of oyster shells and consists $CaCO_3$ as a major phase with a small amount of organic matter. It is a good alternative material source instead of natural lime stone. The utilization of oyster shell waste for industrial applications instead of natural limestone is major advantage for conservation of natural limestone. The present work describes the limestone and oyster shells hydraulic activity and chemical composition and characteristics are most similar for utilization of oyster shell waste instead of natural limestone.