• Clean Technology
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• v.18 no.3
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• pp.272-279
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• 2012

In this study, an environmental-friendly cleaning agent utilizing organic acids and various additives has been developed and applied to the field for removal of scale deposited on the cleaning beds or distribution reservoirs of the waterworks. As an analytical result of scale on the cleaning beds, we found that it consists of mainly metallic oxides such as $SiO_2$, $Al_2O_3$, $Fe_2O_3$, and MnO. Malic acid, malonic acid, and citric acid showed relatively better solvency on $Al_2O_3$, $Fe_2O_3$, and MnO except $SiO_2$ among various organic acids. Mixed organic acid solutions of malic acid, malonic acid, and citric acid were prepared with certain weight ratios and their solvencies on mixed metal oxides of $Al_2O_3$, $Fe_2O_3$, and MnO were investigated. The experimental results showed that an 10% mixed organic acid solution prepared with weight ratio of malic acid : malonic acid : citric acid = 6 : 2 : 2 were found to have best scale solvency power of about 29%. The formulated cleaning agents with a small amount of nonionic surfactant showed much better solvency on mixed oxides than mixed organic solution alone. Especially, the formulated cleaning agent with 0.2 wt% LA-7 surfactant appeared to have best scale removal efficiency of about 35%. However, the formulated cleaning agent with disinfectants such as NaClO, $H_2O_2$ and $Ca(ClO)_2$ showed poor solvency on mixed oxides. It is inferred that surfactants are able to improve scale removal efficiency due to their capability of emulsification, and disinfectants cause to degrade scale solvency in water because of their oxidation. Based on these basic experimental results, formulated cleaning agents have been prepared with mixed organic acid solution, nonionic surfactants, and disinfectants and successfully applied to removal of scales on the cleaning beds and distribution reservoir at city D waterworks.

• Membrane Journal
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• v.26 no.2
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• pp.116-125
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• 2016

This study described a synthesis of MF having a arsenic removal characteristics and the fundamental research was performed about the simultaneous removal system of both As(III) and As(V) ions with the composite nanofiber membrane (PMF) based on PVdF and MF materials for the water-treatment application. From the TEM analysis, the shape and structure of MF materials was investigated. The mechanical strength, pore-size, contact angle and water-flux analysis for the PMF was performed to investigate the possibility of utilizing as a water treatment membrane. From these results, the PMF11 showed the highest value of mechanical strength ($232.7kgf/cm^2$) and the pore-diameter of composite membrane was reduced by introducing the MF materials. In particular, their pore diameter decreased with an increase of iron oxide composition ratio. The water flux value of PMF was improved about 10 to 60% compared with that of neat PVdF nanofiber membranes. From the arsenic removal characterization of prepared MF materials and PMF, it was shown the simultaneous removal characteristics of both As(III) and (V) ions, and the MF01, in particular, showed the highest adsorption-removal rate of 93% As(III) and 68% As(V), respectively. From these results, prepared MF materials and PMF have shown a great potential to be utilized for the fundamental study to improve the functionality of water treatment membrane.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2008.10a
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• pp.205-207
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• 2008

• 한국전기화학회:학술대회논문집
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• 2004.04a
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• pp.19-19
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• 2004

• Journal of the Korean Magnetics Society
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• v.9 no.3
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• pp.131-135
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• 1999

The electronic structures and properties of layered perovskite $LaSrMnO_4$ and $SR^2MnO_4$ have been determined using the local-density full potential Imearized augmented plane wave method. The total energy calculations show that the antiterromagnetic state has lower energy than the ferromagnetic state in $LaSrMnO_4$. The jahn-Teller distortion of Mn-O octahedron produces the energy gap and the $3z^2-r^2$ orbital ordering, which stabilizes 2 dimensional antiferromagnetis state.

• Economic and Environmental Geology
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• v.47 no.4
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• pp.431-439
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• 2014

The purposes of this research were to investigate the enrichment of metal-reducing bacteria from KURT groundwater and the identification of the microbial diversity by 16S rRNA as well as to examine microbial Fe(III)/Mn(IV) reduction and to analyze morphological features of interactions between microbes and precipitates and their mineralogical composition. To cultivate metal-reducing bacteria from groundwater sampled at the KURT in S. Korea, different electron donors such as glucose, acetate, lactate, formate, pyruvate and Fe(III)-citrate as an electron accepter were added into growth media. The enriched culture was identified by 16S rRNA gene sequence analysis for the diversity of microbial species. The effect of electron donors (i.e., glucose, acetate, lactate, formate, pyruvate) and electron acceptors (i.e., akaganeite, manganese oxide) on microbial iron/manganese reduction and biomineralization were examined using the 1st enriched culture, respectively. SEM, EDX, and XRD analyses were used to determine morphological features, chemical composition of microbes and mineralogical characteristics of the iron and manganese minerals. Based on 16S rRNA gene analysis, the four species, Fusibacter, Desulfuromonas, Actinobacteria, Pseudomonas sp., from KURT groundwater were identified as anaerobic metal reducers and these microbes precipitated metals outside of cells in common. XRD and EDX analyses showed that Fe(III)-containing mineral, akaganeite (${\beta}$-FeOOH), reduced into Fe(II)/Fe(III)-containing magnetite ($Fe_3O_4$) and Mn(IV)-containing manganese oxide (${\lambda}-MnO_2$) into Mn(II)-containing rhodochrosite ($MnCO_3$) by the microbes. These results implicate that microbial metabolism and respiratory activities under anaerobic condition result in reduction and biomineralization of iron and manganese minerals. Therefore, the microbes cultivated from groundwater in KURT might play a major role to reduce various metals from highly toxic, mobile to less toxic, immobile.

• 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.

• Economic and Environmental Geology
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• v.41 no.3
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• pp.327-334
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• 2008

Understanding the chemical characteristics of sediments and the nutrient diffusion from sediments to the water body is important in the management of surface water quality. Changes in chemical properties and nutrient concentration of a submerged soil were monitored for 6 months using a microcosm with the thickness of 30cm for upland soil and 15cm of water thickness above the soil. The soil color changed from yellowish red to grey and an oxygenated layer was formed on the soil surface after 5 week flooding. The redox potential and the pH of the pore water in the microcosm decreased during the flooding. The nitrate concentration of the surface water was continuously increased up to $8\;mg\;l^{-1}$ but its phosphate concentration decreased from $2\;mg\;l^{-1}$ to $0.1\;mg\;l^{-1}$ during flooding. However, the concentrations of $NH_4^+$, $PO_4^{3-}$, Fe and Mn in the pore water were increased by the flooding during this period. The increased $NO_3^-$ in the surface water was due to the migration of $NH_4^+$ formed in the soil column and the oxidation to $NO_3^-$ in the surface water. The increased phosphate concentration in the pore water was due to the reductive dissolution of Fe-oxide and Mn-oxide, which scavenged phosphate from the soil solution. The oxygenated layer played a role blocking the migration of phosphate from the pore water to the water body.

• Resources Recycling
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• v.11 no.4
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• pp.44-50
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• 2002

Characteristics on the sulfuric acid leaching of zinc and manganese from the spent zinc-carbon battery powders obtained by cushing and magnetic separation, were investigated with the variation of sulfuric acid concentration, reaction temperature, stir-ring speed and solid/liquid ratio. The sample powders were composed of Zn metal, ZnO, $MnO_2$ and $Mn_2$$O_3$. and it was found that the selective leaching of zinc was difficult in this system. At the condition of S/L ratio 1:10, IM H$_2$$SO_4$, $60^{\circ}C$ and 200 rpm, leaching rate of Zn and Mn are 92% and 35% respectively. The concentration of Zn and Mn in the leaching solution are 19.5 g/l, 7.8 g/l and pH of that solution is 0.75. It was confirmed at reducing agent should be added to increase e leaching rate of manganese with sulfuric acid.

• Clean Technology
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• v.17 no.1
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• pp.41-47
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• 2011

[ $MnO_2$ ]catalysts were prepared by precipitation method using potassium manganate and manganese acetate. The effect of calcination temperatures of $MnO_2$ catalysts for CO oxidation has been studied and their physicochemical properties were studied by X-ray diffraction (XRD), $N_2$ sorption, temperature programmed reduction of $H_2$ ($H_2-TPR$), and temperature programmed desorption of CO (CO-TPD) techniques. $MnO_2$ calcined at $300^{\circ}C$ catalyst has a large surface area $181m^2/g$ having a narrow pore size distribution at 9 nm. The results of XRD and $H_2-TPR$ showed that the catalysts calcined at different temperatures showed mixed oxidation states of Mn such as $Mn^{4+}$ and $Mn^{3+}$. CO-TPD showed that the quantity of $CO_2$ desorbed was decreased with increasing the calcination temperatures. The catalytic activity over the catalyst calcined at $300^{\circ}C$ exhibited the highest conversion reaching to 100% at $200^{\circ}C$. $H_2O$ vapor showed an inhibiting effect on the efficiency of the catalyst because of co-adsorption with CO on the active sites of manganese oxide catalysts and the initial catalytic activity of CO oxidation could be regenerated by removing $H_2O$ vapor in the reactants.