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Lee, Giehyeon,Faure, Gunter,Bigham, Jerry M.,Williams, David J. Wiley (John WileySons) 2008 Journal of environmental quality Vol.37 No.2
<P>Ocoee Lake No. 3 is the first reservoir receiving suspended sediments contaminated with trace metals discharged by acid mine effluents from the Ducktown Mining District, Tennessee. Bottom sediments (0-5 cm) from the lake were sampled to assess the potential for future adverse environmental effects if no remediation controls or activities are implemented. The sediments were found to include a major component (173 +/- 19 g kg(-1)) that dissolved in 6 mol L(-1) HCl within 24 h. This acid-soluble and relatively labile fraction contained high concentrations of Fe (460 +/- 40 g kg(-1)), Al (99 +/- 11 g kg(-1)), Mn (10 +/- 8 g kg(-1)), Cu (2000 +/- 700 mg kg(-1)), Zn (1300 +/- 200 mg kg(-1)), and Pb (300 +/- 200 mg kg(-1)). When the pH of water in contact with the sediment was decreased experimentally from 6.4 to 2.6, the concentrations of dissolved trace metals increased by factors of 2200 for Pb, 160 for Cu, 21 for Zn, 9 for Cd, 8 for Ni, and 5 for Co. The order in which metals were released with decreasing pH was the reverse of that reported for pH-dependent sorption of these metals in upstream systems. Substantial release of trace metals from the sediment was observed even by a modest decrease of pH from 6.4 to 5.9. Therefore, the metal-rich sediment of the lake should be considered as potentially hazardous to bottom-dwelling aquatic species and other organisms in the local food chain. In addition, if the reservoir is dredged or if the dam is removed, the accumulated sediment may have to be treated for recovery of sorbed metals.</P>
Lee, Giehyeon,Song, Kyungsun,Bae, Jongseong Elsevier 2011 Geochimica et cosmochimica acta Vol.75 No.17
<P><B>Abstract</B></P><P>Permanganate (MnO<SUB>4</SUB><SUP>−</SUP>) has widely been used as an effective oxidant for drinking water treatment systems, as well as for in situ treatment of groundwater impacted by various organic contaminants. The reaction stoichiometry of As(III) oxidation by permanganate has been assumed to be 1.5, based on the formation of solid product, which is putatively considered to be MnO<SUB>2</SUB>(s). This study determined the stoichiometric ratio (SR) of the oxidation reaction with varying doses of As(III) (3–300μM) and MnO<SUB>4</SUB><SUP>−</SUP> (0.5 or 300μM) under circumneutral pH conditions (pH 4.5–7.5). We also characterized the solid product that was recovered ∼1min after the oxidation of 2.16mM As(III) by 0.97mM MnO<SUB>4</SUB><SUP>−</SUP> at pH 6.9 and examined the feasibility of secondary heterogeneous As(III) oxidation by the solid product. When permanganate was in excess of As(III), the SR of As(III) to Mn(VII) was 2.07±0.07, regardless of the solution pH; however, it increased to 2.49±0.09 when As(III) was in excess. The solid product was analogous to vernadite, a poorly crystalline manganese oxide based on XRD analysis. The average valence of structural Mn in the solid product corresponded to +III according to the splitting interval of the Mn3s peaks (5.5eV), determined using X-ray photoelectron spectroscopy (XPS). The relative proportions of the structural Mn(IV):Mn(III):Mn(II) were quantified as 19:62:19 by fitting the Mn2p<SUB>3/2</SUB> spectrum of the solid with the five multiplet binding energy spectra for each Mn valence. Additionally, the O1s spectrum of the solid was comparable to that of Mn-oxide but not of Mn-hydroxide. These results suggest that the solid product resembled a poorly crystalline hydrous Mn-oxide such as (Mn<SUP>II</SUP><SUB>0.19</SUB>Mn<SUP>III</SUP><SUB>0.62</SUB>Mn<SUP>IV</SUP><SUB>0.19</SUB>)<SUB>2</SUB>O<SUB>3</SUB>·<I>n</I>H<SUB>2</SUB>O, in which Mn(II) and Mn(IV) were presumably produced from the disproportionation of aqueous phase Mn(III). Thermodynamic calculations also show that the formation of Mn(III) oxide is more favorable than that of Mn(IV) oxide from As(III) oxidation by permanganate under circumneutral pH conditions. Arsenic(III), when it remained in the solution after all of the permanganate was consumed, was effectively oxidized by the solid product. This secondary heterogeneous As(III) oxidation consisted of three steps: sorption to and oxidation on the solid surface and desorption of As(V) into solution, with the first step being the rate-limiting process as observed in As(III) oxidation by various Mn (oxyhydr)oxides reported elsewhere. We also discussed a potential reaction pathway of the permanganate oxidation of As(III).</P>
이기현(Giehyeon Lee) 대한지질학회 2021 대한지질학회 학술대회 Vol.2021 No.10
환경지구화학 연구는 광범위한 물리화학적 조건에서 일어나는 다양한 원소들의 순환과 이들의 거동을 조절하는 주요 (생)지화학 반응경로를 규명함으로써 인간활동을 포함한 수많은 요인들에 의한 자연환경 변화 및 이로 인한 생태계의 영향을 이해하고 예측하기 위한 기본적인 정보를 제공한다. 이를 위해서는 자연환경을 구성하는 주요 성분들의 지화학적 반응성을 좌우하는 물리화학적 특성을 이해하는 것이 필수적이다. 특히, 철과 망간은 각각 유-무기 물질과의 높은 반응성으로 인해 다양한 (생)지화학 반응에 참여하며 주요 원소 및 오염물질들의 거동을 직접적으로 조절하는 가장 중요한 원소들로서 이들의 지화학적 특성을 이해하기 위한 연구가 활발히 수행되고 있다. 자연환경에는 수십 가지 이상의 다양한 준안정-안정상의 철/망간 광물들이 역동적인 광물 형성 및 상전이 반응을 통해 순환하며 여러 지질학적 환경에 널리 분포한다. 그러나 다양한 철/망간 고체상들은 일반적으로 결정도가 낮은 나노입자로 형성되거나 토양 내 미량으로 존재하기 때문에 전통적인 분석방법(e.g., XRD, SEM, TEM)을 통해 정확한 광물동정과 물리화학적 특성을 규명하는데 큰 제한이 있다. 이를 극복하기 위해 1990년대 이후 선진국을 중심으로 다양한 분야의 지화학 연구에 가속기 분석기법인 X-선 흡수분광분석이 광범위하게 활용되어 왔다. 본 발표에서는 X-선 흡수분광분석을 활용한 철/망간 지화학 특성 규명에 대한 본 연구실의 최근 연구사례들을 소개하고자 한다.
Qasim, Ghulam Hussain,Lee, Sangwook,Lee, Giehyeon,Lee, Woojin,Hong, Yongseok,Han, Seunghee The Royal Society of Chemistry 2018 Environmental science Vol.4 No.10
<P>A series of batch experiments were conducted to identify the effects of dissolved oxygen (DO) and nitrate on the removal and reduction of Hg(ii) by a pumice supported nanoscale zero-valent iron (p-nZVI) composite. After the adsorption and consecutive reduction of Hg(ii) in an anoxic solution, zero-valent iron, and ferrous and ferric irons were found on the surface of the p-nZVI with a chain-like structure; while in the oxic solution, a thick ferric shell was found on the surface of the p-nZVI with collapsed chain structures. In Hg(ii) sorption isotherm tests, with 25, 250, 1000, and 2500 nM of Hg(ii), the Hg(ii) sorption capacity of the p-nZVI was 6.1 mg g<SUP>−1</SUP> in the oxic aqueous solution and 1.5 mg g<SUP>−1</SUP> in the anoxic aqueous solution. While the adsorption of Hg(ii) was more favorable in the presence of DO, the headspace Hg(0), as well as dissolved Fe(ii), was largely increased in the absence of DO. The removal of Hg(ii) in oxic and anoxic suspensions was not affected by nitrate levels ranging from 0.08 to 8 mM. In contrast, Hg(0) concentration in headspace increased with an increase of nitrate, which was related to the enhanced dissolved Fe(ii) production. The experimental results of this study suggest that the absence of DO and the presence of nitrate in groundwater could significantly increase Hg(0) in groundwater and adjacent atmosphere during the usual remediation process using relevant nZVI techniques. The effective capture and treatment methods of Hg(0) should be developed for better application of p-nZVI-based technologies.</P>