Chul-Min Chon

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.

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:

Preparation of Calcined Zirconia-Carbon Composite from Metal Organic Frameworks and Its Application to Adsorption of Crystal Violet and Salicylic Acid

\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]

Geochemical Distributions of Heavy Metals and Cr Behavior in Natural and Cultivated Soils of Volcanic Jeju Island, 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).

Soil characteristics and phosphorus accumulation in surface soil in relation to geological and land-use conditions

Zirconia-carbon (ZC) composites were prepared via calcination of Zr-based metal organic frameworks, UiO-66 and amino-functionalized UiO-66, under N2 atmosphere. The prepared composites were characterized using a series of instrumental analyses. The surface area of the ZC composites increased with the increase of calcination temperature, with the formation of a graphite oxide phase observed at 900 °C. The composites were used for adsorptive removal of a dye (crystal violet, CV) and a pharmaceutical and personal care product (salicylic acid, SA). The increase of the calcination temperature resulted in enhanced adsorption capability of the composites toward CV. The composite calcined at 900 °C exhibited a maximum uptake of 243 mg·g−1, which was much greater than that by a commercial activated carbon. The composite was also effective in SA adsorption (102 mg·g−1), and N-functionalization of the composite further enhanced its adsorption capability (109 mg·g−1). CV adsorption was weakly influenced by solution pH, but was more dependent on the surface area and pore volume of the ZC composite. Meanwhile, SA adsorption showed strong pH dependence, which implies an active role of electrostatic interactions in the adsorption process. Base-base repulsion and hydrogen bonding are also suggested to influence the adsorption of CV and SA, especially for the N-functionalized composite.

Heavy Metal Effects on the Biodegradation of Fluorene by Sphingobacterium sp. KM-02 in liquid medium

ABSTRACT Volcanic ash soils, representative soil series (Andisols) on Jeju Island, Korea were collected to investigate the geochemical and mineralogical characteristics. Distributions of heavy metals and Cr behavior, in particular, were further assessed according to land uses (natural or cultivated). The natural soil samples had ferromagnesian minerals mostly in mineralogy, high levels of organic matter, silty textures, and acidic pH. Low amounts of SiO2 and high contents of Al2O3 and Fe2O3, were found in the Jeju soils, which are typical characteristics of Andisols compared to other soil orders. The mean total concentrations of Zn (127 mg/kg), Ni (183 mg/kg), Co (84 mg/kg), and Cr (677 mg/kg) were higher than worldwide values in most of the natural soils. Especially, Cr was a main soil contaminant, exceeding 1000 mg/kg in some soil series. The relationships between heavy metals and major elements indicated a ferromagnesian mineral origin for heavy metals and secondary associations with Fe and Al oxides during weathering processes. Cultivated soils also had similar volcanic ash soil properties, but showed more clayey textures, greater SiO2, and lower Al2O3 and Fe2O3 contents compared to natural soils. The average heavy metal content was not affected by cultivation, and characteristic behavior was maintained, except for slight increases in Cu, Pb, and Zn contents in surface soils because of fertilizer inputs. The only distinct decrease was in Cr content in the surface and subsurface of cultivated soils. This decrease might reflect the formation of a soluble organic complex of Cr(III), based on the significant increase in the sodium pyrophosphate-extracted fraction in sequential extractions. However, the high reducing capacities of volcanic ash soils compared to inland non-volcanic soils suggest that the potential for contamination by Cr(VI) can be significantly very low.

Beam-induced redox transformation of arsenic during As K-edge XAS measurements: availability of reducing or oxidizing agents and As speciation

Abstract Effects of parent rocks and types of land use on soil physical and chemical properties and the phosphorus (P) accumulation in surface soil were examined in a small watershed. The soil developed from granite with a coarse texture, and felsic chemical and mineralogical compositions showed a coarser texture, lower contents of organic matter, water-soluble cations and anions and a lower cation exchange capacity (CEC) than soil developed from andesite. Farmland soils exhibited higher pH and electrical conductivity values, a lower ignition loss and CEC and a coarser texture compared with forest soils from the same parent rocks. The farmland soils contained greater amounts of total P, water-soluble reactive P, organic P and adsorbed inorganic P, and showed a higher degree of P saturation (DPS) than the forest soils in the following order: upland field > orchards > paddy fields > forest. The DPS of the farmland soils (28.2–93.1%) indicated that the soils showed a high potential to release P in the surface water and that careful management was required to reduce P release for the preservation of surface water quality.

Interaction of Sb(III) with iron sulfide under anoxic conditions: Similarities and differences compared to As(III) interactions

The heavy metal effects on the degradation of fluorene by Sphingobacterium sp. KM-02 was determined in liquid cultures. The results showed that 10 mg/L cadmium, copper, zinc, and lead not only affected the growth of KM-02 with fluorene but also the ability of growing or resting cells to degrade this compound. Growth and fluorene degradation were strongly inhibited by cadmium and copper at 10 mg/L, while the inhibitory effect of zinc and lead at the same concentration or at 100 mg/L were not significant. In contrast, arsenic did not affect degradation or growth, even at very high concentrations of 100 mg/L. Subsequent analyses additionally revealed that concentrations of arsenic remained unchanged following incubation, while those of cadmium and copper decreased significantly.

Bioremediation of Heavy Metal Contaminated Mine Wastes using Urease Based Plant Extract

During X-ray absorption spectroscopy (XAS) measurements of arsenic (As), beam-induced redox transformation is often observed. In this study, the As species immobilized by poorly crystallized mackinawite (FeS) was assessed for the susceptibility to beam-induced redox reactions as a function of sample properties including the redox state of FeS and the solid-phase As speciation. The beam-induced oxidation of reduced As species was found to be mediated by the atmospheric O2 and the oxidation products of FeS [e.g. Fe(III) (oxyhydr)oxides and intermediate sulfurs]. Regardless of the redox state of FeS, both arsenic sulfide and surface-complexed As(III) readily underwent the photo-oxidation upon exposure to the atmospheric O2 during XAS measurements. With strict O2 exclusion, however, both As(0) and arsenic sulfide were less prone to the photo-oxidation by Fe(III) (oxyhydr)oxides than NaAsO2 and/or surface-complexed As(III). In case of unaerated As(V)-reacted FeS samples, surface-complexed As(V) was photocatalytically reduced during XAS measurements, but arsenic sulfide did not undergo the photo-reduction.