• Korean Journal of Soil Science and Fertilizer
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• v.26 no.4
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• pp.294-298
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• 1993

The relationship between pH and the activity of ferrous iron in the reduced soil under water-logging was investigated theoretically and experimentally. The results of this study revealed, contrary to hitherto assumed, that the $pH-Fe^{+{+}}$ relationship in the commonly occurring rice soils under reduced condition is close to that in $FeCO_3-CO_2-H_2O$ system, being remote from that in $Fe_3(OH)_8-H_2O$ system and $Fe(OH)_2-H_2O$ system. This indicates that the activity of ferrous iron in the reduced rice soils under water-logging is likely to be governed by $FeCO_3$, neither by $Fe_3(OH)_8$, nor by $Fe(OH)_2$.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.8
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• pp.553-563
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• 2011

This study investigated the effects of elevated $CO_2$ and nitrogen addition on the anaerobic decomposition mediated by microorganisms to determine the microbial metabolic pathways in the degradation of organic matters of the sediments. There were statistically significant differences(P < 0.05) in the rates between denitrification and methanogenesis upon increased $CO_2$ concentration, nitrogen addition, in the presence of plants. Based on the assumption that anaerobic degradation of organic matter mainly occurs through denitrification, iron reduction, and methanogenesis, methanogenesis is the dominant pathways in the decomposition of organic matter under the condition of elevated $CO_2$ and nitrogen addition. In addition, the altered environment increased anaerobic carbon decomposition. Therefore, it can be concluded that freshwater wetland sediments have positive effects on the global warming by the increased methanogenesiss as well as increased anaerobic carbon decomposition.

• Korean Journal of Environment and Ecology
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• v.33 no.5
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• pp.596-604
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• 2019

This study conducted a sediment culture experiment to investigate the effects of sediment oxygen demand (SOD) and environmental factors on sediment and water quality. We installed a leaching tank in the laboratory, cultured it for 20 days, and analyzed the relationship between P and Fe in the sediment. As a result, the dissolved oxygen of the water layer decreased with time, while the oxidation-reduction potential of the sediment progressed in the negative direction to form an anaerobic reducing environment. The SOD was measured to be 0.05 mg/g at the initial stage of cultivation and increased to 0.09 mg/g on the 20th day, indicating the tendency of increasing consumption of oxygen by the sediment. The change is likely to have caused by oxygen consumption from biological-SOD, which is the decomposition of organic matter accumulated on the sediment surface due to the increase of chl-a, and chemical-SOD consumed when the metal-reducing product produced by the reduction reaction is reoxidized. The correlation between SOD and causality for sediment-extracted sediments was positive for Ex-P and Org-P and negative for Fe-P. The analysis of the microbial community in the sediment on the 20th day showed that anaerobic iron-reducing bacteria (FeRB) were the dominant species. Therefore, when the phosphate bonded to the iron oxide is separated by the reduction reaction, the phosphate is eluted into the water to increase the primary productivity. The reduced substance is reoxidized and contributes to the oxygen consumption of the sediment. The results of this study would be useful as the reference information to improve oxygen resin.

• Resources Recycling
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• v.31 no.2
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• pp.12-19
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• 2022

The study was conducted to develop a vanadium recovery process using reduction pre-treatment in the Vanadium TitanoMagnetite (VTM) The sample for the research was provided by the Gwan-in Mine in Pocheon, Gyeonggi-do. The vanadium content of the sample is 0.54 V₂O₅% and vanadium is concentrated mainly in magnetite and ilmenite. Magnetic separation of the sample can increase vanadium content up to 1.10 V₂O₅%. To increase the vanadium content further, reduction pre-treatment was performed, which is a process of concentrating vanadium present in the iron by reducing iron in magnetite using carbon(C). Based on this reduction pre-treatment, the magnetic separation process was developed, which achieved a vanadium grade of 1.31V₂O₅% and 79.68% recovery. In addition, XRD analysis of the vanadium concentrate before and after reduction and the final vanadium concentrate was performed to confirm the behavior of vanadium by reduction pre-treatment.

• Resources Recycling
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• v.7 no.1
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• pp.34-40
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• 1998

This shdy was invcsligated on reduction rate of EAF dust wth solid carbon cantents. The rate equation for reduction ofEAF dust was obtaincd in the tempcrahlrc range cot 910-108O"C, and the ratio of zinc removal and metallization raho of ironoxides to thc reaction time was also analysed. From the XRD analysis for slag residues '||'&'||'er reaction, the cxistcncc DI themixture of Akemmite[Ca2MgSi2O.] and SiO, was identified.ed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2B
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• pp.187-192
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• 2011

Nitrate nitrogen is common contaminant in groundwater aquifers, its concentration is regulated many countries below 10 mg/L as N (As per WHO standards) in drinking water. An attempt was made to get optimal results for the treatment of nitrate nitrogen in groundwater by conducting various experiments by changing the experimental conditions for ZVI bipolar packed bed electrolytic cell. From the experimental results it is evident that the nitrate nitrogen removal is more effective when the reactor conditions are maintained in acidic range but when the acidic environment changes to alkaline due to the hydroxide formed during the process of ammonia nitrogen there by increasing the pH reducing the hydrogen ions required for reduction which leads to low effectiveness of the system. In the ZVI bipolar packed bed electrolytic cell, the packing ratio of 0.5~1:1 was found to be most effective for the treatment of nitrate nitrogen because ZVI particles are isolated and individual particle act like small electrode with low packing ratio. It is seen that formation of precipitate and acceleration of clogging incrementally for packing ratio more than 2:1, decreasing the nitrate nitrogen removal rate. When the voltage is increased it is seen that kinetics and current also increases but at the same time more electric power is consumed. In this experiment, the optimum voltage was determined to be 50V. At that time, nitrate nitrogen was removed by 94.9%.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.12
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• pp.1262-1267
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• 2008

Reductive discolorization studies were conducted. Azo-dyes usually have biological toxicity and it is known that the dyes are hardly removed by biological treatments. One of the simplest way to remove the color is to break the azo-bond and it is possible to break the bond with zero-valent metals. Three types of azo-dyes (Cibacron Briliant Yellow 3G-P (CBY3G-P), Benzopurpurin 4b (B-4B), Chicago sky blue 6b (CSB6B)) were tested. All tested azo-dyes were highly pH dependent and lower pH was preferred. The reaction mechanism was reductive cleavage and amines were expected as products. The dissolved iron ions from zero-valent iron can also remove the color through coagulation and precipitation and a set of experiments were conducted to evaluate the contribution by the dissolved iron. The results indicated that the contribution were also dependent on the type of dyes. This study showed that the reductive cleavage using zero-valent iron could be an alternative for the azo-dye waste water.

• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.24-28
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• 2018

The redox flow battery (RFB) is a large-capacity energy storage equipment, and the vanadium redox flow cell is a typical RFB, but VRFB is expensive. Iron-chrome RFBs are economical because they use low-cost active materials, but their low performance is a urgent problem. In this study, the crossover of iron and chromium ion through Nafion membrane and the stability of Nafion membrane in HCl solution were investigated. The permeability of iron and chrome ion through Nafion were $5.5{\times}10^{-5}$ and $6.0{\times}10^{-5}cm^2/min$, respectively, which was 18.9~20.7 times higher than that of vanadium ion ($2.9{\times}10^{-6}cm^2/min$). The crossover of iron and chromium ions were shown to be a cause of performance decrease in Iron-chrome RFB. As the temperature increases, the crossover increases rapidly (activation energy 38.8 kJ/ mol), indicating that operation at low temperature is a methode to reduce the performance loss due to crossover. Nafion membranes were relatively stable in 3 M HCl solution.

• Resources Recycling
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• v.7 no.2
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• pp.39-45
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• 1998

We smelted thc pellets made by mixing the distilled carbon from wlISte Lires, LD converter dust and slag with reduction process in the revcrberatory furnace. Thc obtained results are as follows 1) The removal mte of zinc appears above 97% after T reducing the pellets at $1300^{\circ}C$ for Ihr and the zinc content in the residue are 0.1~D.2%. 2) Under the mixing condition of 500 g LD dust. 150-200 g LD slag and 30-50 g distilled carbon of waste lires the removal raho of zinc shows above 95%, while t the 50-60% Fe remains in the residue. 3) After smelting at $1350^{\circ}C$ for 3hrs, the recovery ratio of pig iron reduced from lhe p pellets containing 15-20% LD slag and 4.1-7.2% distilled carbon of waste tires appears in the range of 89.3-92%. 4) Tbe c chemical composition of the recovered pig iron is 1.7%C, O.05%P, 0.05%S and balance Fe. 5) Tbe recovered dust from the d dust collcctor alter finishing the reduction rcaction appears as a crude zinc oxide conLaining 60% zinc.

• Resources Recycling
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• v.7 no.3
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• pp.27-35
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• 1998

EAF dust generated from electric arc steelmaking process is classified as "hazardous" materials by tbe environmental regulation because of the existence of water leachable heavy metals such as Fe, Zn, Pb, and Cd. However, Fe and Zn among t the elements in the dust can be recovered to high valuable materials by applying a proper process. Therefore, in order to study t the possibility of recovery of iron from EAF dust, the effect oE carbon content and basicity, of synthesized EAF dust on the reduction rate of iron oxide was studied. Experimental results are as follows: TIle softening and melting temperature of the slag w was illcreased with increasing carbon addition amount [or carbon reduction eqUIvalent. At the carbon addition amount of 100% for carbon reduction equivalent and basicity of 1.7, reduction rate of $Fe_2O$ in the slag was the highest. The reaction order fur reduction of $Fe_2O$ by carbon was nearly first order.