• Journal of Korean Society of Environmental Engineers
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• v.34 no.3
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• pp.189-194
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• 2012

In this study, a 3-stage biological aerated filter (BAF) system was proposed to enhance nitrogen removal in the treatment of low carbon to nitrogen ratio (C/N ratio) municipal wastewater. Laboratory experiments were conducted to evaluate the effects of dynamic-flow at the HRT of 6 h. Results of the long-term operation of 3-stage BAF systems showed that the dynamic-flow enabled the total nitrogen removal (T-N) removal efficiency of the system to be about 7 % higher than that of non-dynamic-flow system in treating domestic wastewater due to the more efficient use of organic substrates. The overall $NH_4$-N removal performance was stable during the operational period due to the unique system configuration where independent nitrification occurred. It was concluded that the 3-stage BAF system proposed in this study provided excellent performance in the removal of nitrogen by employing dynamic-flow and three columns functioning as sorption, denitrification and nitrification, respectively.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.2
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• pp.51-58
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• 2017

We investigated the efficiency of natural zeolite with different cation exchange capacity (CEC) as capping material for the remediation of marine sediments contaminated with heavy metals. Three different zeolite with high CEC (HCzeo, 163.74 cmolc/kg), medium CEC (MCzeo, 127.20 cmolc/kg), and low CEC (LCzeo, 70.62 cmolc/kg) were used. The surface area of the zeolite was in decreasing order: HCzeo ($59.43m^2/g$) > MCzeo ($52.10m^2/g$) > LCzeo ($10.12m^2/g$). The results of mineralogical composition obtained from X-ray diffraction (XRD) show that LCzeo was mainly composed of quartz and albite. In the XRD result of MCzeo and HCzeo, the peaks of clinoptilolite, heulandite, and mordenite were also observed along with that of quartz and albite. Sorption equilibrium onto the HCzeo, MCzeo, and LCzeo was reached in 6 h at initial concentration of 10 mg/L and 100 mg/L. Higher adsorption of Cd and Zn onto the zeolite with higher CEC were achieved but adsorption of Cu and Ni were not dependent on the CEC of zeolite. It can be concluded that the zeolite with high cation exchange ability is recommended for the contaminated sediments with Cd and Zn but the inexpensive zeolite with low CEC for Cu and Ni.

• Journal of Korean Society on Water Environment
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• v.20 no.3
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• pp.256-264
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• 2004

Adsorption characteristics of three endocrine disruptors, amitrol, nonylphenol, and bisphenol-A, were evaluated depending on the type and service duration of activated carbon (AC). Bituminous coal-, wood-, and coconut-based coals were tested. Bituminous coal-based AC (BCAC) had the greatest sorption capacity for the three chemicals tested, followed by wood-based AC (WAC) for nonylphenol and coconut palm-based AC (CAC) for bisphenol-A. During the column test, amitrol removal efficiency increased over time, indicating that hydrophilic endocrine disruptors are biodegraded in the AC column. Removal efficiencies of hydrophobic compounds such as nonylphenol and bisphenol-A decreased over time since the main removal mechanism was adsorption. The order of the amitrol removal was: BCAC-5.9 yr, CAC-3.l yr > BCAC-2.2 yr > BCAC-virgin > CAC-virgin > WAC-virgin > WAC-3.l yr. In general, used AC had greater removals than virgin AC. The order of the bisphenol-A removal was: CAC-virgin > BCAC-2.2 yr > CAC-3.l yr > WAC-virgin > BCAC-5.9 yr > WAC-3.l yr. The order of the nonylphenol removal was: BCAC-virgin > WAC-virgin > CAC-3.1 yr, WAC-3.1yr> BCAC-2.2 yr > BCAC-5.9 yr > CAC-3.1 yr. Bituminous coal AC performed the best over time. Endocrine disruptors such as these three compounds appear to be removed effectively by activated carbon through biodegradation and adsorption. Wood and coal based among the virgin ACs and 3.1 years used wood base among the used ACs appeared the lowest carbon usage rate(CUR) for nonylphenol removal by prediction model. Virgin and used coconut base ACs except BCAC had the lowest CUR for removal Bisphenol-A. Biodegradation of nonylphenol and Bisphenol-A did not occurred during the 9,800 bed volume experiment period. BCAC had the highest biodegradation capacity of 46% for amitrol among virgin ACs and the used coal based ACs had 33-44% higher biodegradation capacity than virgin's for amitrol so biodegradation is the effective removal technology for hydrophilic material such as amitrol.

• Clean Technology
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• v.16 no.2
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• pp.132-139
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• 2010

The Cu-Mn mixed oxide catalysts with different molar ratios of Cu/(Cu+Mn) prepared by co-precipitation method have been investigated in CO oxidation at $30^{\circ}C$. The catalysts used in this study were characterized by X-ray Diffraction (XRD), $N_2$ sorption, X-ray photoelectron spectroscopy (XPS), and $H_2$-temperature programmed reduction $(H_2-TPR)$ to correlate with catalytic activities in CO oxidation. The $N_2$ adsorption-desorption isotherms of Cu-Mn mixed oxide catalysts showed a type 4 having pore range of 7-20 nm and BET surface area was increased from 17 to $205\;m^2{\cdot}g^{-1}$ with increasing of Mn content. The XPS analysis showed the surface oxidation state of Cu and Mn represented $Cu^{2+}$and the mixture of $Mn^{3+}$ and $Mn^{4+}$, respectively. Among the catalysts studied here, Cu/(Cu+Mn) = 0.5 catalyst showed the highest activity at $30^{\circ}C$ in CO oxidation and the catalytic activity showed a typical volcano-shape curve with respect to Cu/(Cu+Mn) molar ratios. The water vapor showed a prohibiting effect on the efficiency of the catalyst which is due to the competitive adsorption of carbon monoxide on the active sites of catalyst surface and finally the formation of hydroxyl group with active metals.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.4
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• pp.278-286
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• 2009

In this study, four natural Mn oxides ($NMO_1-NMO_4$) was characterized using x-ray diffraction, scanning electron microscopy, and their removal efficiency for 1-naphthol (1-NP) in aqueous phase, using batch reactor, was investigated. The results were compared with one another and a synthetic manganese oxide, birnessite. The NMOs have a various Mn minerals including pyrolusite (${\beta}-MnO_2$), cryptomeltane (${\alpha}-MnO_2$) as well as birnessite (${\delta}-MnO_2$) depending on their sources, which results in different removal efficiencies (removals, kinetics) and reaction types (sorption or oxidative-transformation). The comparative study showed that $NMO_1$ (electrolytic Mn oxide) have a higher removal efficiency for 1-NP via oxidative-transformation compared to birnessite. The 1-NP removals by NMOs were followed by pseudo-first order reaction, and the surface area-normalized specific rate constants ($K_{surf},\;L/m^2$ min) determined were in order of $NMO_1(3.31{\times}10^{-3})$>${\delta}-MnO_2(1.48{\times}10^{-3}){\fallingdotseq}NMO_3(1.46{\times}10^{-3})$>$NMO_2(0.83{\times}10^{-3})$>$NMO_4(0.67{\times}10^{-3})$. From the solvent extraction experiments with the Mn oxide precipitates after reaction, it was observed that the oxidative-transformation rates of 1-NP were in order of $NMO_1{\fallingdotseq}{\delta}-MnO_2$>$NMO_3$>$NMO_4{\gg}NMO_2$ and the analysis of HPLC chromatogram and UV-Vis. absorption ratios ($A_{2/4}$, $A_{2/6}$) on the supernatant confirmed that the reaction products were oligomers formed by oxidative-coupling reaction. Results from this study proved that natural Mn oxide (except $NMO_2$) used in this experiment can be effectively applied for the removal of naphthols in aqueous phase, and the removal efficiencies are depending on the surface characters of the Mn oxides.

• Journal of Environmental Impact Assessment
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• v.29 no.5
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• pp.350-362
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• 2020

In this study, nano Fe°-impregnated biochar (INPBC) was prepared using pruning residues and one-pot synthetic method and evaluated its performance as an amendment agent for the stabilization of arsenic-contaminated soil. For the preparation of INPBC, the mixture of pruning residue and Fe (III) solution was heated to 220℃ for 3hr in a teflon-sealed autoclave followed by calcination at 600℃ under N₂ atmosphere for 1hr. As-prepared INPBC was characterized using FT-IR, XRD, BET, SEM. For the stabilization test of as-prepared INPBC, As-contaminated soils (Soil-E and Soil-S) sampled from agricultural sites located respectively near E-abandoned mine and S-abandoned mine in South Korea were mixed with different of dosage of INPBC and cultivated for 4 weeks. After treatment, TCLP and SPLP tests were conducted to determine the stabilization efficiency of As in soil and showed that the stabilization efficiency was increased with increasing the INPBC dosage and the concentration of As in SPLP extractant of Soil-E was lower than the drinking water standard level of Ministry of Environment of South Korea. The sequential fractionation of As in the stabilized soils indicated that the fractions of As in the 1st and 2nd stages that correspond liable and known as bioavailable fraction were decreased and the fractions of As in 3rd and 4th stages that correspond relatively non-liable fraction were increased. Such a stabilization of As shows that the abundant nano Fe° on the surface of INPBC mixed with As-contaminated soils played the co-precipitation of As leaching from soil by surface complexation with iron. The results of this study may imply that INPBC as a promising amendments for the stabilization of As-contaminated soil play an important role.

• Korean Journal of Food Science and Technology
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• v.39 no.5
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• pp.534-540
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• 2007

In this study, waxy rice starch was chemically modified using phosphorous oxychloride ($POCl_3$, 0.002-0.008%). Then the physicochemical properties of resulting cross-linked waxy rice starches were investigated in order to reduce the steeping time of Yukwa (a Korean oil-puffed rice snack) processing. The swelling powers of the cross-linked waxy rice starch samples were higher than the native waxy rice starch at temperatures above $60^{\circ}C$, and their increases were proportional to the $POCl_3$, concentration. The solubility of the cross-linked waxy rice starch was lower (1.6-3.4%) than the native waxy rice starch (2.7-6.1%). However, the moisture sorption isotherm of the cross-linked waxy rice starch was not significantly different from the native waxy rice starch. The rapid visco analyze. (RVA) pasting temperatures $(65.4-67^{\circ}C)$ of the cross-linked waxy rice starch were lower than those of the native starch $(67^{\circ}C)$. The RVA peak viscosities (287-337 RVU) of the cross-linked waxy rice starch were higher than that of native starch (179 rapid visco units (RVU)), and increased with increasing $POCl_3$ concentration. For the differential scornning calorimeter thermal characteristics, although Tc shifted toward higher temperatures with cross-linking, the To, Tp, and amylopectiin melting enthalpy of the cross-linked waxy rice starch showed no differences compared to the native waxy rice starch. The X-ray diffraction patterns of both the native and cross-linked waxy rice starches showed typical A-type crystal patterns, suggesting that cross-linking mainly occurs in the amorphous regions of starch granules. Therefore, the cross-linking reaction did not change the crystalline region, but altered the amorphous region of the waxy rice starch molecules, resulting in changes of solubility and RVA pasting properties in the cross-linked waxy rice starch. In summary, since cross-linked waxy rice starch has a high puffing efficiency and no browning reaction, it may be applicable for Yukwa processing without a long steeping process.

• Journal of Soil and Groundwater Environment
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• v.11 no.1
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• pp.14-22
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• 2006

Laboratory column experiment for simultaneous removal of Cd and Cr(VI) were conducted using newly developed material of Fe-loaded zeolite having both reduction ability and sorption capacity. The solution containing Cd and Cr(VI) was injected into the column and the breakthrough curves (BTCs) for the contaminants were observed at the effluent port. Cd breakthrough was not initialized until Cr(VI) breakthrough was completed. Therefore it could be concluded that overall efficiency of Fe-loaded zeolite should be determined by the reactivity for Cr(VI). The relative concentration of Cr(VI) BTC increased to the unit value while initial breakthrough was delayed and the propagation of breakthrough was slowed. In order to quantitatively describe the shape of Cr(VI) BTC, new parameters of ${\alpha}\;and\;{\beta}$ designated to be shape parameters, were defined and applied in contaminant transport concentration. These parameters were employed to represent the degree of initial breakthrough delay and the degree of breakthrough propagation, respectively. As initial contaminant concentration increased, ${\alpha}$ decreased, which indicated the delay of BTC's initiation. And as initial contaminant flow rate increased, ${\beta}$ decreased, which represented the faster propagation of the BTC. From these results, Fe-loaded zeolite was found to be an effective reactive material for PRBs against heavy metals having different ionic forms in groundwater. And it could be expected that as groundwater flows faster, the propagation of breakthrough would be faster and as contaminant concentration is higher, the initial point of breakthrough would appear earlier.

• Korean Chemical Engineering Research
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• v.47 no.3
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• pp.349-354
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• 2009

In this study, a bubbling fluidized-bed reactor was used to study $CO_2$ capture from flue gas using a potassium-based dry sorbent. A dry sorbent, manufactured by the Korea Electric Power Research Institute, consists of 35% of $K_2CO_3$ for $CO_2$ absorption and 65% of supporters for mechanical strength. $H_2O$, a reactant of the carbonation reaction, was supplied in the reactor as a form of saturated water vapor at a given temperature. The experiment of the regeneration reaction was performed by raising up to a given temperature using $N_2$ as a fluidization gas. It was indicated that sorption capacity and regenerability of dry sorbents showed high-efficiency at $1.97\;mol\;H_2O/mol\;CO_2$ and $400^{\circ}C$, respectively. The regenerated sorbent samples were analyzed by TGA to confirm the extent of the reaction. When the regeneration temperature was $150^{\circ}C$, the regenerability of dry sorbents was about 60%, which was capable of applying those sorbents to a two-interconnected fluidized-bed reactor system with continuous solid circulation. The results obtained in this study can be used as basic data for designing and operating a large scale $CO_2$ capture process with two fluidized-bed reactors.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.4
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• pp.247-256
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• 2013

In this study, alginate beads containing birnessite (Bir-AB), a highly reactive oxidative catalyst for the transformation of phenolic compounds, was prepared and its 1-naphthol (1-NP) removal efficiency was investigated in a batch test. Based on scanning electron microscopy image, it can be inferred that the alginate gel cluster acts as a bridge which bind the birnessite particles together. Kinetic experiment with Bir-AB of different mixing ratios of birnessite to alginate (Bir : AG=0.25 : 1~1 : 1 w/w) indicate that pseudo-first order kinetic constants, $k(hr^{-1})$ for the 1-NP removals increased about 1.5 times when the birnessite mixing ratio was doubled. The removals of 1-NP was found to be dependent on solution pH and the pesudo-first order rate constants were increased from 0.331 $hr^{-1}$ at pH 10 to 0.661 $hr^{-1}$ at pH 4. The analysis of total organic carbon for the reaction solutions showed that a higher removal of dissolved organic carbon was achieved with Bir-AB as compared to birnessite. HPLC chromatographic analysis of the methanol extract after reaction of 1-NP with Bir-AB suggest that the reaction products could be removed through incorporation into the aliginate beads as a bound residue. Mn ions produced from the oxidative transformation of 1-NP by birnessite were also removed by sorption to Bir-AB. The Bir-AB was recovered quantitatively by simple filtration and was reused twice without significant loss of the initial reactivity.