• Journal of Surface Science and Engineering
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• v.50 no.6
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• pp.531-535
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• 2017

Enormous amount of waste oyster-shell (OS) has a major disposal problem in coastal regions. OSs have attracted much attention for recycling, because these are mainly composed of calcium carbonate with rare impurities. In this study, we demonstrate the calcareous deposit films on steel plate by using OSs on the basic of cathodic protection technique. The composition of the OSs was analyzed by wavelength dispersive X-ray fluorescence spectrometer. Carbon dioxide gas was pumped into distilled water to make carbonic acid solution for dissolution of OS. The calcareous deposit was characterized by second electron microscope (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction. Corrosion rates were estimated by measurements of anodic polarization and immersion test. It is confirmed that calcareous deposits on steel plate are formed under all condition of cathodic protection by using waste OS from the SEM and EDX results. Calcareous deposits on steel by OS provide good corrosion resistance by acting as a barrier to oxygen supply to the steel surface.

• Environmental Engineering Research
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• v.13 no.3
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• pp.155-161
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• 2008

This study examined effects of the fermented leachate of food waste (FLFW) on nitrogen and phosphorous removal for domestic wastewater containing a low carbon-to-nitrogen (C/N) ratio in sequencing batch reactor (SBR). When the FLFW was not supplied in the process, release of phosphorus and excessive intake was not observed at both anaerobic and aerobic stages. On the other hand, when the FLFW was gradually added, active release of phosphorus and intake of phosphorus was noticed at an anaerobic stage and aerobic stage, respectively, resulting in improved phosphorus removal efficiency. The removal efficiency of nitrogen and phosphorus was increased from 75% and 37% (R-1, control test) to 97% and 80% (R-4, the highest substrate ratio test), respectively. In addition, although activity of the nitrogen oxidizing microorganisms was reduced when the reaction temperature was decreased to $10^{\circ}C$, the phosphorus removal efficiency was shown to increase with the addition of FLFW, indicating an independence from temperature. Overall, this study suggests that an efficient nutrients removal process can be successfully employed into a SBR when the FLFW is added to a wastewater which has a low C/N ratio.

• Environmental and Resource Economics Review
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• v.30 no.2
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• pp.269-297
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• 2021

Bioplastics are attracting attention as a substitute for conventional petroleum-based plastics because they are carbon neutral and can be biodegradable. This study estimated economic and environmental impact of regulating the petroleum-based plastics industry and fostering the bioplastics industry using a Recursive Dynamic CGE Model of the Korean Economy. Results show that the regulation of the conventional plastics industry exhibits a positive environmental impact by reducing greenhouse gases and plastic waste and a negative economic impact with a decrease in GDP. Meanwhile, fostering the bioplastics industry with regulation on conventional plastics industry has similar levels of greenhouse gas and waste reduction effects when there is only regulation on the conventional plastics industry. It is also shown that expanding the production of bioplastics industry offsets existing economic losses as a form of increased GDP. If petroleum-based plastics are replaced through the expansion of bioplastics production, it can contribute to the decoupling of greenhouse gas emissions and plastic waste from economic growth.

• Clean Technology
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• v.15 no.3
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• pp.147-153
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• 2009

Waste three-way catalysts were remanufactured by ultrasonic wave treatment followed by active component re-impregnation and the catalytic activities and surface properties of remanufactured catalysts were measured at various remanufacturing conditions. In case of the catalyst prepared by ultrasonic wave cleaning, the optimal period for elimination of surface contaminants from the waste catalyst was found to be about 5 minutes. The proper re-impregnation amounts of the active components for the best catalytic performance were investigated and the catalytic performance tests were also carried out with various temperature for the total hydrocarbon (THC), carbon monoxide (CO) and nitrogen oxides (NOx) conversions. The experimental results showed that the catalytic performances of the remanufactured catalysts were recovered almost the same level as those of the fresh catalyst except those of the NOx conversion.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.501-508
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• 2023

Addressing urban noise problems, this study develops eco-friendly, inorganic sound-absorbing panels, overcoming the limitations of traditional PMMA and cement-based panels. These conventional panels pose safety risks due to flammability and environmental concerns due to carbon emissions. Utilizing industrial waste, the research comprises two phases: initial tests for physical and performance characteristics (fluidity, density, compressive strength, sound absorption) and subsequent development of optimized panel mixtures. This approach aims to replace existing panels with sustainable, effective alternatives, significantly contributing to safer, environmentally responsible urban infrastructure. The findings of this study have implications for the sound panel market, offering novel solutions for noise control while aligning with environmental and safety standards.

• Journal of Korean Society on Water Environment
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• v.40 no.3
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• pp.131-139
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• 2024

This study investigated the chemical properties of Organic Soil Amendments (OSAs) made from organic waste. It also assessed the effectiveness of using these OSAs in the soil layer of Green Infrastructure (GI) to reduce stormwater runoff and non-point source pollutants. The goal was to improve the national environmental value through resource recycling and contribute to the circular economy transformation and carbon neutrality of urban GI. The OSAs used in this study consisted of spent coffee grounds and food waste compost. They were found to be nutrient-rich and stable as artificial soils, indicating their potential use in the soil layer of GI facilities. Applying OSAs to bio-retention cells and permeable pavement resulted in a reduction of approximately 11-17% in stormwater runoff and a decrease of about 16-18% in Total Phosphorus (TP) discharge in the target area. Increasing the proportion of food waste compost in the OSAs had a positive impact on reducing stormwater runoff and pollutant emissions. This study highlights the importance of utilizing recycled resources and can serve as a foundation for future research, such as establishing parameters for assessing the effectiveness of GI facilities through experiments. To enable more accurate analysis, it is recommended to conduct studies that consider both the chemical and biological aspects of substance transfer in OSAs.

• Applied Chemistry for Engineering
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• v.31 no.1
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• pp.7-12
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• 2020

Astragalus uliginosus L.-stems as a by-product of oriental medicine are produced largely in a northern area of Chungbuk province. These by-products do not have any demand and thus usually discarded into the fields as a waste. In this work, a biochar was prepared from the Astragalus uliginosus L.-stem waste for recycling. The biochar was used to investigate the removal characteristics of cadmium and manganese ions dissolved in water. When adsorption equilibrium experiments were performed to treat 50 and 100 mg/L of cadmium ions, the removal efficiencies of cadmium were 100 and 95%, respectively. In addition, the maximum of adsorption amount for manganese ions in 5 h at an initial concentration of 50 and 100 mg/L was found to be as 36.1 and 37.9 mg/g, respectively. Based on the experimental results, it was found that the adsorption amount of Astragalus uliginosus L.-stem biochar for the removal of both cadmium and manganese ions was four times higher than that of the activated carbon. The surface analysis of both biochar and activated carbon samples using X-ray photoelectron spectroscopy (XPS) analysis showed that the oxygen content and O/C ratio of biochar was 2.1 and 2.4 times higher than that of the activated carbon, respectively. In order to enhance the removal capability of manganese, 50 and 100 mg/L of manganese ions were operated at different temperatures. It was observed that these equilibrium was attained in 4 h under 45 ℃ and removal efficiencies were 92 and 53%, respectively. Consequently, the experimental results can be utilized as a new removal technology for eco-friendly and economically treating cadmium and manganese ions dissolved in water.

• Korean Journal of Materials Research
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• v.25 no.2
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• pp.75-80
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• 2015

The carbon dioxide($CO_2$) released while producing building materials is substantial and has been targeted as a leading contributor to global climate change. One of the most typical method to reducing $CO_2$ for building materials is the addition of slag and fly ash, like pozzolan material, while another method is reducing $CO_2$ production by carbon negative cement development. The MgO-based cement was from the low-temperature calcination of magnesite required less energy and emitted less $CO_2$ than the manufacturing of Portland cements. It is also believed that adding reactive MgO to Portland-pozzolan cements could improve their performance and also increase their capacity to absorb atmospheric $CO_2$. In this study, the basic research for magnesia cement using $MgCO_3$ and magnesium silicate ore (serpentine) as main starting materials, as well as silica fume, fly ash and blast furnace slag for the mineral admixture, were carried out for industrial waste material recycling. In order to increase the hydration activity, $MgCl_2$ was also added. To improve hydration activity, $MgCO_3$ and serpentinite were fired at $700^{\circ}C$ and autoclave treatment was conducted. In the case of $MgCO_3$ as starting material, hydration activity was the highest at firing temperature of $700^{\circ}C$. This $MgCO_3$ was completely transferred to MgO after firing. This occurred after the hydration reaction with water MgO was transferred completely to $Mg(OH)_2$ as a hydration product. In the case of using only $MgCO_3$, the compressive strength was 3.5MPa at 28 days. The addition of silica fume enhanced compressive strength to 5.5 MPa. In the composition of $MgCO_3$-serpentine, the addition of pozzolanic materials such as silica fume increased the compression strength. In particular, the addition of $MgCl_2$ compressive strength was increased to 80 MPa.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.163-169
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• 2019

Sn-Pb solder alloys in electronics rapidly has been replaced to Pb free solder alloys because of various environmental regulations such as restriction of hazardous substances directive (RoHS), European Union waste electrical, waste electrical and electronic equipment (WEEE), registration evaluation authorization and of chemicals (REACH) etc. Because Sn58%Bi (in wt.%) solder alloy has low melting point and higher mechanical properties than that of Sn-Pb solder, it has been studied to manufacture electronic components. However, the reliability of Sn58%Bi solder could be lowered because of the brittleness of Bi element included in the solder alloy. Therefore, we observed the microstructures of Sn58%Bi composite solders with various contents of Sn-decorated multiwalled carbon nanotube (Sn-MWCNT) particles and evaluated bonding strength of the FR-4 components assembled with Sn58%Bi composite solder. Also, microstructures and bonding strengths of the Sn58%Bi composite solder joints were evaluated with the number of reflows from 1 to 7 times, respectively. Bonding strengths and fracture energies of the Sn58%Bi composite solder joints were measured by die shear test. Microstructures and fracture modes were observed with scanning electron microscope (SEM). Microstructures in the Sn58%Bi composite solder joints were finer than that of only Sn58%Bi solder joint. Bonding strength and fracture energy of Sn58%Bi composite solder including 0.1 wt.% of Sn-decorated MWCNT particles increased up to 20.4% and 15.4% at 5 times in reflow, respectively.

• Carbon letters
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• v.12 no.3
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• pp.143-151
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• 2011

Bagasse fly ash (BFA) is one of the important wastes generated in the sugar industry; it has been studied as a prospective low-cost adsorbent in the removal of congo red (CR) from aqueous solutions. Chemical treatment with $H_2O_2$ was applied in order to modify the adsorbability of the raw BFA. Batch studies were performed to evaluate the influence of various experimental parameters such as dye solution pH, contact time, adsorbent dose, and temperature. Both the adsorbents were characterized by Fourier-transform infrared spectrometer, energy-dispersive X-ray spectrophotometer and nitrogen adsorption at 77 K. Equilibrium isotherms for the adsorption of CR were analyzed by Langmuir, Freundlich and Temkin models using non-linear regression technique. Intraparticle diffusion seems to control the CR removal process. The obtained experimental data can be well described by Langmuir and also followed second order kinetic models. The calculated thermodynamic parameters indicate the feasibility of the adsorption process for the studied adsorbents. The results indicate that BFA can be efficiently used for the treatment of waste water containing dyes.