Hi-Soo Moon

Arsenic removal using steel manufacturing byproducts as permeable reactive materials in mine tailing containment systems

Steel manufacturing byproducts were tested as a means of treating mine tailing leachate with a high As concentration. Byproduct materials can be placed in situ as permeable reactive barriers to control the subsurface release of leachate from tailing containment systems. The tested materials had various compositions of elemental Fe, Fe oxides, Ca-Fe oxides and Ca hydroxides typical of different steel manufacturing processes. Among these materials, evaporation cooler dust (ECD), oxygen gas sludge (OGS), basic oxygen furnace slag (BOFS) and to a lesser degree, electrostatic precipitator dust (EPD) effectively removed both As(V) and As(III) during batch experiments. ECD, OGS and BOFS reduced As concentrations to <0.5mg/l from 25mg/l As(V) or As(III) solution in 72 h, exhibiting higher removal capacities than zero-valent iron. High Ca concentrations and alkaline conditions (pH ca. 12) provided by the dissolution of Ca hydroxides may promote the formation of stable, sparingly soluble Ca-As compounds. When initial pH conditions were adjusted to 4, As reduction was enhanced, probably by adsorption onto iron oxides. The elution rate of retained As from OGS and ECD decreased with treatment time, and increasing the residence time in a permeable barrier strategy would be beneficial for the immobilization of As. When applied to real tailing leachate, ECD was found to be the most efficient barrier material to increase pH and to remove As and dissolved metals.

Removal capacity of water plant alum sludge for phosphorus in aqueous solutions

Abstract Alum sludge, which is a waste product from a potable water treatment process, was tested as an inexpensive alternate adsorbent for phosphorus in wastewater. The sludge was composed dominantly of sand size aggregates, and could remain stable in aqueous media. The majority of reactive Al in alum sludge was present as an amorphous phase, and seemed to be the major absorbent for P. The batch sorption test showed that the removal of P was influenced by the solubility of Al, Fe and organic carbon depending on pH condition. The acidic condition favored the removal of P, and there was a side effect in the P removal process such as dissolution of Al and organic C at acidic (pH < 4) and alkaline (pH < 8) conditions. The pH range from 4 to 6 was effective for all inorganic and organic phosphates with a low solubility of Al and organic C. The maximum adsorption capacity of alum sludge was calculated as 25,000 mg/kg for orthophosphate, and followed the order: orthophosphate > pyrophosphate > triphosphate > organic phosphate (adenosin). From the column test with a 30 mg/L orthophosphate solution at a flow rate of 3.0 ml/min, the alum sludge removed P to less than 1.0 mg/L over 250 pore volumes at initial pH 4, and 200 pore volumes at initial pH 5, respectively.

The occurrence and dispersion of potentially toxic elements in areas covered with black shales and slates in Korea

Abstract Potentially toxic heavy metals together with other elements are present in some natural geological materials and the Okchon black shale in Korea provides an important example of this. The dispersion of these elements in the rocks and soils derived from this shale are examined. Geochemical surveys were undertaken in 11 study areas in the Okchon Zone underlain by black shales, slates, phyllites and limestones. After appropriate preparation of rocks and soils, samples were analysed for multi-elements by INAA, ICP-AES and ICP-MS. Some potentially toxic elements are highly enriched in the Okchon black shales and soils developed from these shales in the Dukpyungri and Majeonri areas. In particular, mean concentrations in soils in the Dukpyungri area are 34 μg/g As, 43 μg/g Mo and 3.4 μg/g Se which are significantly higher than the worldwide average for soils. The degree of enrichment decreases in the order: forest > upland farm = paddy > playground soils, and discriminant analysis by geochemical characteristics separates soils in the black shale area from those in other rock areas in terms of Se, Zn, Mo and Cd.

Enrichment of potentially toxic elements in areas underlain by black shales and slates in Korea

The Okchon black shale in Korea provides an important example of natural geological materials containing toxic elements; the Chung-Joo, Duk-Pyung, Geum-Kwan, I-Won and Chu-Bu areas are underlain by these black shales and slates of the Guryongsan Formation. This formation is part of the Okchon Group which is found in the central part of Korea. Geochemical surveys were undertaken in these five study areas in the Okchon Zone in order to examine the level of enrichment and dispersion patterns of potentially toxic elements in rocks and soils. After appropriate preparation, samples were analysed by instrumental neutron activation analysis and inductively coupled plasma atomic emission spectrometry for a range of elements. Arsenic, Cu, Mo, V, U and Zn are highly enriched in the Okchon black shales and their mean concentrations are significantly higher than those in black slates. These elements are closely associated with one another from a geochemical viewpoint and may be enriched simultaneously. Mean concentrations of As, Mo and U in soils derived from black shales occurring in the Duk-Pyung and Chu-Bu areas are higher than the permissible level suggested by Kloke (1979), and the enrichment index decreases in the order of Duk- Pyung > Chu-Bu > Chung-Joo > Geum-Kwan = I-Won areas. Uranium-bearing minerals such as uraninite and brannerite have been identified in black shales from the Chung-Joo area by electron probe micro-analysis. Uraninite grains are closely associated with monazite and pyrite with a grain size ranging from 2μm to 10μm whereas brannerite grains occur as a euhedral form 50μm in diameter.

CRYSTAL STRUCTURES OF BIOTITE AT HIGH TEMPERATURES AND OF HEAT-TREATED BIOTITE USING NEUTRON POWDER DIFFRACTION

The crystal structure of biotite-1 M from Bancroft, Ontario, with the formula:

Electro‐enhanced remediation of trichloroethene‐contaminated groundwater using zero‐valent iron

\left( {{{\rm{K}}_{1.96}}{\rm{N}}{{\rm{a}}_{0.13}}{\rm{C}}{{\rm{a}}_{0.01}}} \right)\left( {{\rm{M}}{{\rm{g}}_{3.15}}{\rm{Fe}}_{2.59}^{2 + }{\rm{T}}{{\rm{i}}_{0.17}}{\rm{M}}{{\rm{n}}_{0.09}}} \right)\left( {{\rm{S}}{{\rm{i}}_{5.98}}{\rm{A}}{{\rm{l}}_{1.92}}{\rm{T}}{{\rm{i}}_{0.10}}} \right){{\rm{O}}_{20}}\left[ {{{\left( {{\rm{OH}}} \right)}_{1.47}}{{\rm{F}}_{1.98}}} \right]

New occurrence and characterization of Ni-serpentines in the Kwangcheon area, Korea

(K1.96Na0.13Ca0.01)(Mg3.15Fe2.592+Ti0.17Mn0.09)(Si5.98Al1.92Ti0.10)O20[(OH)1.47F1.98], was determined by Rietveld refinement using high-resolution neutron powder diffraction at in situ temperatures ranging from 20 to 900°C. The room-temperature structure of the samples heated to between 400 and 900°C using an electric furnace in air was also refined. The crystal structures were refined to an RP of 2.98 — 5.06% and Rwp of 3.84–6.77%. For the in situ heating experiments in a vacuum, the unit-cell dimensions increased linearly to 600°C. The linear expansion coefficient for the c axis was 1.65 × 10−5°C−1, while those for the a and b dimensions were 4.44 × 10−6°C−1 and 5.21 × 10−6°C−1, respectively. Accordingly, the increase in the unit-cell volume up to 600 C occurred mainly along the c axis, resulting from the expansion in the K coordination sphere along that direction. Results for all K−O bonds were analyzed in terms of the lattice component and an inner component of the structural strain. The ditrigonal distortion decreased (3.76 at 20°C to 1.95 at 600°C) with temperature, because the shorter bonds expanded and the longer bonds contracted. The increase in the interlayer separation and the decrease in the interlayer octahedral flattening angle confirmed that the c-dominated expansion occurred in the interlayer region. In the case of the ex situ-heated samples, the cell dimensions decreased sharply at temperatures over 400 C. The octahedral sheet thickness and mean distance decreased linearly due to oxidation of octahedral Fe. However, the interlayer separation and mean distance decreased at temperatures over 400°C. At 400°C, dehydroxylation began to increase and interlayer regions became more constricted. The overall cell parameters decreased rapidly with increasing temperatures due to dehydroxylation. The large inner strain components in the K−O bonds also resulted in an increase in the considerable ditrigonal distortion (3.57° at 400°C to 6.15° at 900°C).

Mineralogy and chemistry of the opaques of Cox's Bazar (Bangladesh) beach sands and the oxygen fugacity of their provenance

Abstract The objective of this study was to develop and evaluate electro‐enhanced dechlorination of trichloroethene (TCE) in groundwater using Fe°. A bench‐scale flow‐through Fe° reactor column with direct current was tested to increase the efficiency of Fe° medium by providing an external supply of electrons. The bench‐scale column tests confirmed that the application of direct current with Fe° was highly effective in enhancing the rate of TCE dechlorination. The t1/2 for the TCE dechlorination without current was 10.3 hours and the t1/2 for the TCE dechlorination with current was about 1 hour. The dechlorination mechanism appears to be reductive dechlorination, with the electrons supplied by the iron oxidation and external direct current power supply serving as the source of the electrons.

Ge-incorporation into 6-line ferrihydrite nanocrystals

Abstract Pecoraite and nepouite, Ni-serpentines, occur in the serpentinized ultramafic rocks in the Kwangcheon area, Korea, where the parent rock is classified as harzburgite and/or lherzolite. Pecoraite was precipitated twice from the solution; the early-formed pecoraite coexists with magnetite, millerite, and polydymite both in the Buk- and Nam-sites, while the late-formed pecoraite appears as well-grown colloform and opaque-free phase only in the Buk-site. The typical colloform texture of the late-formed pecoraite strongly indicates that it was precipitated from the solution in supergene conditions. Pecoraite is characterized by its extremely high Ni content and the difference in Fe content between the early- and late-formed pecoraite. Nepouite is distinguished from pecoraite by its prismatic morphology and the large degree of isomorphous substitution between Ni and Mg. The phase relations among coexisting magnetite-millerite-polydymite assemblage with the earlyformed pecoraite suggest that the pecoraite might have precipitated in the extremely limited ƒo2 and ƒs2 environment from the highly Ni-concentrated solutions and is stable at 25°C and 1 bar.

Iron reduction by a psychrotolerant Fe(III)-reducing bacterium isolated from ocean sediment

Abstract The heavy minerals of Coxs Bazar beach sands (Bangladesh) are dominated by hornblende, opaque minerals, garnet and epidote. Opaque minerals consist primarily of ilmenites (both unaltered and altered) with magnetite, rutile, pyrite and some hydroxides. A large part of ilmenites (about 50% of the unaltered ilmenites) exsolves hematite in different textural patterns. Exsolutions of ilmenite-hematite-rutile and ilmenite-rutile are insignificant. In hematite host, the first-generation coarser ilmenite lamellae contain less FeTiO3 ( ∼ 84 mol%) than the second-generation finer ilmenite lamellae ( ∼ 93 mol% FeTiO3). No significant difference in chemical composition is observed in the coarse and fine lamellae of hematite exsolved in ilmenites. Exsolution features and compositions of ilmenites (e.g., MgO% 0.5) point to an igneous source. Titanomagnetite (± exsolved ilmenite) and optically homogeneous magnetite are common. A regular partitioning of Cr, V, Al, Mg and Mn between coexisting titanomagnetite and ilmenite suggests chemical equilibrium. The distribution of MnO between coexisting ilmenite and titanomagnetite and the plot of MgO vs. TiO2 of ilmenite intergrowth in titanomagnetite suggest their origin in intrusive igneous rocks. The approximate temperature and oxygen fugacity as estimated from the microprobe analyses of coexisting titanomagnetite-ilmenite phases range from 645° to 850°C and 10−13 to 10−19, respectively, suggesting a crustal origin.