• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.533-536
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• 2009

The gasification technology is a very flexible and versatile technology to produce a wide variety products such as electricity, steam, hydrogen, Fisher-Tropsch(FT) diesels, Dimethyl Ether(DME), methanol and SNG(Synthetic Natural Gas) with near-zero pollutant emissions. Gasification converts coal and other low-grade feedstocks such as biomass, wastes, residual oil, petroleum coke, etc. to a very clean and usable syngas. Syngas is produced from gasifier including CO, $H_2$, $CO_2$, $N_2$, particulates and smaller quantities of $CH_4$, $NH_3$, $H_2S$, COS and etc. After removing pollutants, syngas can be variously used in energy and environment fields. The pilot-scale coal gasification system has been operated since 1994 at Ajou University in Suwon, Korea. The pilot-scale gasification facility consists of the coal gasifier, the hot gas filtering system, and the acid gas removal (AGR) system. The acid gas such as $H_2S$ and COS is removed in the AGR system before generating electricity by gas engine and producing chemicals like Di-methyl Ether(DME) in the catalytic reactor. The designed operation temperature and pressure of the $H_2S$ removal system are below $50^{\circ}C$ and 8 kg/$cm^2$. The iron chelate solution is used as an absorbent. $H_2S$ is removed below 0.1 ppm in the H2S removal system.

• Advances in environmental research
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• v.3 no.2
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• pp.163-172
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• 2014

Magnetite was chosen as a typical adsorbent to study its phosphate adsorption capacity in water body with low concentration of phosphorus (below $2mg\;PL^{-1}$). Magnetite was collected from Luoyang City, Henan Province, China. In this research, three factors have been studied to describe the adsorption of phosphate on magnetite, which was solution concentration (concentration ranging from 0.1 to $2.5mg\;PL^{-1}$), suspension pH (1 to 13) and temperature (ranging from $10^{\circ}C$ to $40^{\circ}C$). In addition, the modified samples had been characterized with XRD and FE-SEM image. The results show that iron ions contains in magnetite were the main factors of phosphorus removal. The behavior of phosphorus adsorption to substrates could be fitted to both Langmuir and Freundlich isothermal adsorption equations in the low concentration phosphorus water. The theoretical saturated adsorption quantity of magnetite is 0.158 mg/g. pH has great influence on the phosphorus removal of magnetite ore by adsorption. And pH of 3 can receive the best results. While temperature has little effect on it. Magnetite was greatly effective for phosphorus removal in the column experiments, which is a more practical reflection of phosphorous removal combing the adsorption isotherm model and the breakthrough curves. According to the analysis of heavy metals release, the release of heavy metals was very low, they didn't produce the secondary pollution. The mechanism of uptake phosphate is in virtue of chemisorption between phosphate and ferric ion released by magnetite oxidation. The combined investigation of the magnetite showed that it was better substrate for water body with low concentration of phosphorus.

• Journal of Soil and Groundwater Environment
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• v.27 no.1
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• pp.25-30
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• 2022

Mackinawite (FeS), as a ubiquitous reduced iron mineral, is known as a key controller of redox reactions in anaerobic subsurface environment. The reaction of FeS with redox-sensitive toxic element such as arsenic is substantially affected by pH conditions of the given environments. In this study, the interaction of As(V) with FeS was studied under strict anaerobic conditions with various pH conditions. The pH-dependent arsenic removal tests were conducted under wide ranges of pH conditions and X-ray absorption spectroscopy (XAS) was applied to investigate the reaction mechanisms under pH 5, 7, and 9. The removal efficiency of FeS for As(V) showed the higher removal of As(V) under low pH conditions and its removal efficiency decreased with increasing pH, and no As(V) reduction was observed in 1 g/L FeS solution. However, XAS analysis indicated the reduction of As(V) to As(III) occurred during reaction between FeS and As(V). The reduced form of As(III) was particularly identified as an arsenic sulfide mineral (As₂S₃) in all pH conditions (pH 5, 7, and 9). As₂S₃ precipitation was more pronounced in pH 5 where the solubility of FeS is higher than in other pH conditions. The linear combination fitting results of XAS demonstrated that As(V) removal mechanism is concerted processes of As₂S₃ precipitation and surface complexation of both arsenic species.

• Journal of Soil and Groundwater Environment
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• v.11 no.4
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• pp.1-9
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• 2006

The purpose of this study is to evaluate laboratory experiments on arsenic and cadmium removal from tailings using apatite at the Ulsan Abandoned Iron Mine, and to develop a stabilization technique. The results of this study show that the permeability is decreased proportionally to the amount of apatite when it is added below 8%, while this is almost constant when the amount of apatite is added above 10%. The water extraction test from tailings using deionized water for several days shows that pH (7.4-8.4) is almost constant or slightly increased when apatite is added below 8%, while it is slightly decreased when apatite is added above 10%. According to TCLP test, reduction of concentrations of heavy metals in leachate is proportional to amount of apatite added. It seems that precipitates generated from leachate-apatite chemical reaction are not redissolved. As a result, cadmium and arsenic in leachate is mostly removed when apatite is added above 10%, and it is suggested that a proper technique should be selected for field application because either mixed or layered method shows almost same removal efficiencies of cadmium and arsenic in tailings.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1B
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• pp.79-84
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• 2012

Nitrate is a common contaminant in groundwater aquifer. The present study investigates the performance of the bipolar zero valent iron (ZVI, $Fe^0$) packed bed electrolytic cell in removing nitrate in different operating conditions. The packing mixture consists of ZVI as electronically conducting material and silica sand as non-conducting material between main cathode and anode electrodes. In the continuous experiments for the simulated wastewater (contaminated groundwater, initial nitrate about 30 mg/L as N and electrical conductivity about 300 ${\mu}S/cm$), over 99% removal of nitrate was achieved in the applied voltage 600 V and at the flow rate of 20 mL/min. The optimum packing ratio (v/v) and flow rate were determined to be 1:1~2:1 (silica sand to ZVI), 30 mL/ min respectively. Effluent pH was proportional to nitrate influx concentration, and ammonia which is the final product of nitrate reduction was about 60% of nitrate influx. Magnetite was observed on the surface of the used ZVI as major oxidation product.

• Resources Recycling
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• v.20 no.5
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• pp.34-39
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• 2011

Metallurgical grade silicon(MG-Si) was melted with Ca at 1500$^{\circ}C$ under Ar atmosphere. The sample was cooled at 10 $^{\circ}C$/min to room temperature and leached in aqua regia. In the present study, the effect of Ca addition and conditions of acid leaching on removal of Fe and P in MG-Si were investigated. CaSi$_2$ phase was formed at the grain boundary of MG-Si melting with Ca. Also FeSi$_2$ phase was precipitated in CaSi$_2$ phase. By the formation of CaSi$_2$ phase, 97% of Fe and 66 % of P were removed from Ca added MG-Si with the particle size of 600~850${\mu}m$ by aqua regia(more than 30%) leaching.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.3
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• pp.157-161
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• 2011

This study investigated decomposition the pathway and characteristics of fenitrothion, which is applied on the golf course for pesticide, by ZVI in batch reactor. The removal efficiencies of the pure fenitrothion and the commercial fenitrothion in Smithion by ZVI were compared. The fenitrothion was converted to 3-Methyl-4-nitrophenol and 4-Amino-m-cresol by ZVI. The fenitrothion decomposition rate by ZVI could be expressed by the first order reaction. As increasing the ZVI dosages, the first order rate constants and removal efficiencies increased. The surface area normalized rate constants for the pure fenitrothion and the commercial fenitrothion were 0.0398 and 0.1312 ($L/m^2{\cdot}hr$), respectively. The decomposition of the commercial fenitrothion in Smithion was faster than that of the pure fenitrothion by ZVI, the surfactant in Smithion lead to enhances solubility of fenitrothion and disperse ZVI.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.118-123
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• 2017

To manufacture MG-Si (Metallurgical grade silicon) for use in various industries, Acid leaching experiments were performed to remove aluminum (Al) and iron (Fe), which are the most common impurities found in the silicon raw material. The silicon raw material was reacted with five types of acids (HCl, HF, H2SO4, HNO3, H3PO4) at 1, 2, 4, and 6M; 1M HF showed the highest Al and Fe removal rates, 97.9% and 95.2%, respectively. HF, however, resulted in an 18% reduced yield due to the silicon corrosion properties. To minimize the yield reduction, 2M HCl, which has a second removal ratio result, was mixed with 1M HF and applied to the silicon raw material. The experiment was conducted to select the optimal conditions for the mixed solution, which were $80^{\circ}C$ and 2hr. Under the optimal conditions, the residual Al and Fe concentrations were 141 ppmw and 93 ppmw, respectively, and it very easy to produce MG-Si with 3N grade purity.

• Environmental Engineering Research
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• v.24 no.3
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• pp.474-483
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• 2019

In this study, iron (Fe) impregnated granular activated carbon (Fe-GAC) has been synthesized and characterized for various properties. Comparative studies have been performed for use of Fe-GAC as an adsorbent as well as a catalyst during catalytic oxidation of hydroquinone (HQ). In the batch adsorption study, effect of process parameter like initial HQ concentration ($C_o=25-1,000mg/L$), pH (2-10), contact time (t: 0-24 h), temperature (T: $15-45^{\circ}C$) and adsorbent dose (w: 5-50 g/L) have been studied. Maximum HQ adsorption efficiency of 75% was obtained at optimum parametric condition of: pH = 4, w = 40 g/L and t = 14 h. Pseudo-second order model best-fitted the HQ adsorption kinetics whereas Langmuir model best-represented the isothermal equilibrium behavior. During oxidation studies, effect of various process parameters like initial HQ concentration ($C_o:20-100mg/L$), pH (4-8), oxidant dose ($C_{H2O2}:0.4-1.6mL/L$) and catalyst dose (m: 0.5-1.5 g/L) have been optimized using Taguchi experimental design matrix. Maximum HQ removal efficiency of 83.56% was obtained at optimum condition of $C_o=100mg/L$, pH = 6, $C_{H2O2}=0.4mL/L,$ and m = 1 g/L. Overall use of Fe-GAC during catalytic oxidation seems to be a better as compared to its use an adsorbent for treatment of HQ bearing wastewater.

• The Journal of Engineering Geology
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• v.19 no.3
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• pp.389-400
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• 2009

Iron and manganese contents are usually over the limit of drinking water standard (0.3 mg/L) in unconsolidated aquifer of river bank filtration site in Nakdong river. Surge block and air surging techniques used in this study are useful tools to remove the slime within gravels and pebbles, to increase permeability of aquifer, to provide oxygen into aquifer, and to discharge iron and manganese oxides from a well. Surging activity brought about $5{\sim}8$ and $5{\sim}9$ times decreases in $Fe_{(total)}$ and $Fe^{2+}$ contents, and also 10 times decrease in $Mn^{2+}$ contents compared to non-surging condition, respectively. Additionally, iron oxide and manganese oxide increased up $1{\sim}1.2$ times after surging. This result shows that air injection into the aquifer can help iron and manganese content decreased and in-situ treatment technology needs to be introduced in river bank filtration project in South Korea.