• Resources Recycling
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• v.31 no.1
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• pp.12-20
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• 2022

The smelting reduction of spent lithium-ion batteries results in metallic alloys containing Co, Cu, Fe, Mn, Ni, and Si. A process to separate metal ions from the sulfuric acid leaching solution of these metallic alloys has been reported. In this process, ionic liquids are employed to separate Fe(III) and Cu(II). In this study, D2EHPA and Cyanex 301 were employed to replace these ionic liquids. Fe(III) and Cu(II) from the sulfate solution were sequentially extracted using 0.5 M D2EHPA with three stages of cross-current and 0.3 M Cyanex 301. The stripping of Fe(III) and Cu(II) from the loaded phases was performed using 50% (v/v) and 60% (v/v) aqua regia solutions, respectively. The mass balance results from this process indicated that the recovery and purity percentages of the metals were greater than 99%.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.149-152
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• 2008

The reaction between iron oxide and ferrous iron is known to be the adsorption of ferrous iron onto the oxide surfaces that produces Fe(II)-Fe(III) (hydr)oxides and ferrous oxide oxidized to ferric ion which is the reducing agent of the target compounds. In our investigations on DS/S using ferrous modified steel slag, the results did not follow the trends. FeO and Fe(II), the major component of steel slag, were used to investigate the degradation of TCE. Degradation did not take place for the first and suddenly degraded after awhile. Degradation of TCE in this system was unexpected because Fe(II)-Fe(III) (hydr)oxides could not be produced in absence of ferric oxide. In this study, the characteristics of FeO/Fe(II) system as a reducing agent were observed through the degradation of TCE, measuring byproducts of TCE and the concentration of Fe(II) and Fe(III). Adsorption of ferrous ion on FeO was observed and the generation of byproducts of TCE showed the degradation of TCE by reduction in the system is obvious. However it did not correspond with the typical reducing mechanisms. Future research on this system needs to be continued to find out whether new species are generated or any unknown mineral oxides are produced in the system that acted in the degradation of TCE.

• Journal of Microbiology and Biotechnology
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• v.13 no.3
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• pp.366-372
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• 2003

The production of microbiologically enriched cultures that degrade cis- 1,2-dichloroethylene(DCE) under anaerobic conditions was investigated. Among 80 environmental samples, 19 displayed significant degradation of $10{\mu}M$ cis-DCE during 1 month of anaerobic incubation, and one sediment sample collected at a landfill area (Nanji-do, Seoul, Korea) showed the greatest degradation ($94\%$). When this sediment culture was subcultured repeatedly, the ability to degrade cis-DCE gradually decreased. However, under Fe(III)-reducing conditions, cis-DCE degradation by the subculture was found to be maintained effectively. In the Fe(III)-reducing subculture, vinyl chloride (VC) was also degraded at the same extent as cis-DCE No accumulation of VC during the cis-DCE degradation was observed. Thus, Fe(III)-reducing microbes might be involved in the anaerobic degradation of the chlorinated ethenes. However, the subcultures established with Fe(III) could function even in the absence of Fe(III), showing that the degradation of cis-DCE and VC was not directly coupled with the Fe(III) reduction. Consequently, the two series of enrichment cultures could not be obtained that degrade both cis-DCE and VC in the presence or absence of Fe(III). Considering the lack of VC accumulation, both cultures reported herein may involve interesting mechanism(s) for the microbial remediation of environments contaminated with chlorinated ethenes. A number of fermentative reducers (microbes) which are known to reduce Fe(III) during their anaerobic growth are potential candidates involved in cir-DCE degradation in the presence and absence of Fe(III).

• Journal of the Korean Chemical Society
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• v.55 no.3
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• pp.463-471
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• 2011

A novel $N_2O_2$ Schiff base ligand, N,N'-bis(4-methoxysalicylidene)phenylendiamine(4-$CH_3O$-Salphen), has been synthesized. It has been revealed that the compound is very useful for the spectrophotometric quantification of Fe(II) and Fe(III) ions in aqueous solutions, such as mineral water, hot spring water, sea water, and waste water. The optimum conditions for the quantitative analysis are the followings; [4-$CH_3O$-Salphen]=$4.0{\times}10^{-4}\;M$, DMF/$H_2O$=70/30(v/v), pH=3.4~3.8, T= at $55^{\circ}C$, and prereaction time=1.0 hr. The sample of single valence state was prepared by the preliminary oxidation or reduction using $H_2O_2$ ($5.0{\times}10^{-4}\;M$) and $NH_2OH{\cdot}HCl$ ($5.0{\times}10^{-4}\;M$). The quantitative analyses of Fe(II) and Fe(III) ion were performed by measuring the absorbance at 434 nm and 456 nm, respectively. The estimated mean values agreed well with the standard values within the range of 2.00~6.90%. The limit of detection was 27.9 ng/mL for Fe(II) and 55.8 ng/mL for Fe(III).

• Journal of Microbiology and Biotechnology
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• v.15 no.4
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• pp.780-786
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• 2005

The biomass of the brown seaweed, Ecklonia, was used to remove Cr(VI) from wastewater. Previously, Cr(VI) was removed through its reduction to Cr(III) when brought into contact with the biomass. In this study, the effects of ionic strength, background electrolytes, and Cr(III), Ni(II), Zn(II), and Fe(III) on the Cr(VI) reduction were examined. An increased ionic strength inhibited the Cr(VI) reduction. The presence of other heavy metals, such as Cr(III), Ni(II), or Zn(II), only slightly affected the Cr(VI) reduction, while Fe(III) enhanced the reduction. Although the above various parameters could affect the reduction rate of Cr(VI) by Ecklonia biomass, these effects were relatively smaller than those of pH and temperature. In addition, the previously derived rate equation was found to be applicable over a range of ionic strengths and with different background electrolytes. In conclusion, Ecklonia, bioniass may be a good candidate as a biosorbent for the removal of Cr(VI) from wastewaters containing various other impurities, and scale-up to a practical process may be accomplished using the previously derived rate equation.

• Journal of Korea Soil Environment Society
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• v.4 no.2
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• pp.11-31
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• 1999

Removal of hexavalent chromium from artificial groundwater (AGW) by granular activated carbon (GAC) was investigated in batch and continuous-flow column studies. Experimental parameters that were examined included solution pH, presence of dissolved oxygen (DO), and GAC pretreatment with Fe(II). As the solution pH increased from 4 to 7.5, the amount of Cr(VI) removed by both GACs decreased significantly. Exclusion of DO from the experimental systems resulted in greater removal of Cr(VI) from solution, possibly as a result of reduction to Cr(III). However, pretreatment of the GAC with a reductant (Fe(II)) did not improve Cr(VI) removal. Equilibration With 0.01 M $K_2$$HPO_4$[to extract adsorbed Cr(VI)] followed by a wash with 0.02 N $K_2$$HPO_4$[to remove precipitated/sorbed Cr(III)] proved to be a viable approach for the regeneration of carbons whose Cr(VI) removal capacities had been exhausted. The performance of the regenerated carbons exceeded that of the virgin carbons, primarily because of the favorable adsorption of Cr(VI) at lower pH values and the reduction of Cr(VI) to Cr(III), The presence of Cr(III) in acid wash solutions provides direct evidence that Cr(VI) is reduced to Cr(III) in GAC systems under relatively acidic conditions. GAC performance over five complete cycles was consistently high, which suggests that such a system will be able to function over many operation cycles without deleterious effects.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.250-253
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• 2002

Remediation of groundwater using zero valent iron filings has received considerable attention in recent years. However, zero valent iron is gradually transformed to iron(III) oxides at permeable reactive barriers, so the reduction of iron(III) oxides can enhance the longevity of the reactive barriers. In this study, microbial reduction of Fe(III) was performed in anaerobic condition. A medium contained nutrients similar to soil solution. The medium was autoclaved and deoxygenated by purging with 99.99% $N_2$ and pH was buffered to 6, while the temperature was regulated as 2$0^{\circ}C$. Activity of iron reducing bacteria were not affected by chlorinated organics but affected by iron(III) oxide. Although perchloroethylene(PCE) was not degraded with only ferric oxide, PCE was reduced to around 50% with ferric oxide and microorganism. It shows that reduced iron can dechlorinate PCE.

• Journal of the Mineralogical Society of Korea
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• v.29 no.2
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• pp.73-78
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• 2016

The oxidation states of structural Fe in clay minerals often reflect the paleo-redox conditions of the depositional environments. It is inevitable to utilize the high resolution of transmission electron microscopy (TEM) to investigate the mechanism of mineral transformation at nano-scale. The applications of TEM- electron energy loss spectroscopy (EELS) for quantification of $Fe(III)/{\Sigma}Fe$ from the K-nontronite formation associated with structural Fe(III) reduction in nontronite under deep subseafloor environment were demonstrated. In particular, quantification of the changes in Fe-oxidation state at nanoscale is essential to understand the mechanisms of minerals formation. The procedure of EELS acquisition, quantitative determination of Fe-oxidation states, and advantages of EELS techniques were discussed.

• Journal of Soil and Groundwater Environment
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• v.16 no.6
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• pp.58-65
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• 2011

The bacterial uranium(VI) reduction and its resultant low solubility make this process an attractive option for removing U from groundwater. An impact of aqueous suspending iron phase, which is redox sensitive and ubiquitous in subsurface groundwater, on the U(VI) bioreduction by Shewanella putrefaciens CN32 was investigated. In our batch experiment, the U(VI) concentration ($5{\times}10^5M$) gradually decreased to a non-detectable level during the microbial respiration. However, when Fe(III) phase was suspended in solution, bioreduction of U(VI) was significantly suppressed due to a preferred reduction of Fe(III) instead of U(VI). This shows that the suspending amorphous Fe(III) phase can be a strong inhibitor to the U(VI) bioreduction. On the contrary, when iron was present as a soluble Fe(II) in the solution, the U(VI) removal was largely enhanced. The microbially-catalyzed U(VI) reduction resulted in an accumulation of solid-type U particles in and around the cells. Electron elemental investigations for the precipitates show that some background cations such as Ca and P were favorably coprecipitated with U. This implies that aqueous U tends to be stabilized by complexing with Ca or P ions, which easily diffuse and coprecipitate with U in and around the microbial cell.

• Journal of the Korean Society of Safety
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• v.4 no.1
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• pp.71-74
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• 1989

The $\alpha$-Fe$_2$O$_3$ gas sensor, prepared by the precipitation of Fe(OH)$_3$ from a solution of iron(III) sulfate and tin (IV) chloride, was composed of fine particles and was superior in sensitivity to other $\alpha$-Fe$_2$O$_3$. The gas sensitivity was found to depend on the amounts of remaining sulfate ion the microstructure and a small amount of iron(II) species generated through the reduction of $\alpha$-Fe$_2$O$_3$. The sensing mechanism of $\alpha$-Fe$_2$O$_3$gas sensor was confirmed to be due to the reduction of $\alpha$-Fe$_2$O$_3$ to the low resistive Fe$_3$-xO$_4$ by combustible gas and to depend on the crystral structure.