Haruhiko Seyama

Sorption of Co(II), Ni(II), and Zn(II) on Biogenic Manganese Oxides Produced by a Mn-Oxidizing Fungus, Strain KR21-2

Abstract The characteristics of Co(II), Ni(II), and Zn(II) sorption on freshly produced biogenic Mn oxides by a Mn-oxidizing fungus, strain KR21-2, were investigated. The biogenic Mn oxides showed about 10-fold higher efficiencies for sorbing the metal ions than a synthetic Mn oxide (γ-MnO2) on the basis of unit weight and unit surface area. The order of sorption efficiency on the biogenic Mn oxides was Co(II) > Zn(II) > Ni(II), while that on the synthetic Mn oxide was Zn(II) > Co(II) > Ni(II). These sorption selectivities were confirmed by both sorption isotherms and competitive sorption experiments. Two-step extraction, using 10 mM CuSO4 solution for exchangeable sorbed ions and 10–20 mM hydroxylamine hydrochloride for ions bound to reducible Mn oxide phase, showed higher irreversibility of Co(II) and Ni(II) sorption on the biogenic Mn oxides while Zn(II) sorption was mostly reversible (Cu(II)-exchangeable). Sorptions of Co(II), Ni(II), and Zn(II) on the synthetic Mn oxide were, however, found to be mostly reversible. Higher irreversibility of Co(II) and Ni(II) sorption on the biogenic Mn oxides may partly explain higher accumulation of these metal ions in Mn oxide phases in natural environments. The results obtained in this study raise the possibility to applying the biogenic Mn oxide formation to treatment of water contaminated with toxic metal ions.

X-ray photoelectron spectroscopic study of montmorillonite containing exchangeable divalent cations

Montmorillonite containing divalent Mg, Ca, Sr, Ba or Cd as an exchangeable cation has been studied by X-ray photoelectron spectroscopy and X-ray-induced Auger electron spectroscopy. The relative atomic abundances of the exchangeable cations in the montmorillonite samples, obtained by X.p.s. measurements, are consistent with the cation-exchange capacity of the montmorillonite. A comparison of the photoelectron binding energies and Auger electron kinetic energies of the exchangeable cations with those of corresponding halides and oxides reveals that they fall among those of corresponding cations in typical ionic compounds such as fluorides and chlorides. On the other hand, the bonding state of the non-exchangeable Mg ion in montmorillonite lattice, as indicated by the Mg ls and KL2, 3L2, 3 Auger electron energies, is similar to that of magnesium oxide and distinguishable from that of the exchangeable Mg ion.

Biogeochemistry of manganese oxide coatings on pebble surfaces in the Kikukawa River System, Shizuoka, Japan

The biogeochemistry of Mn-oxide coatings formed over submerged pebble surfaces on the streambed of the Kikukawa river system has been investigated. Located in central Shizuoka, Japan, this system drains strongly acidified soils under tea plantations. Besides containing high amounts of Mn (up to 450 μg/cm2), the coatings are capable of scavenging and accumulating other elements including Ba, Zn, Ni, Co, W, Mo and Sb. When suspensions of the coating material were incubated with 0.2 mM Mn2+, the Mn(II) ion was microbially transformed into Mn-oxides. When the same suspensions were spread on agar plates containing acetate, yeast-extract, and 1.0 mM Mn2+ (AY agar medium) both Mn-oxidizing bacteria and fungi appeared, indicating the existence of a diversity of Mn-oxidizing microorganisms in the system. Plate counts using two agar culture media with varied nutrient levels indicated that the ability of these microorganisms to oxidize Mn(II) was strongly dependent on nutrient supply. The relatively nutrient-poor AY agar medium was more conducive to microbial growth than the K1 agar medium with a higher organic nutrient content. Concentrations of Mn dissolved in the stream waters did not correlate well with the amounts of solid Mn on submerged pebbles. Thus, factors other than dissolved Mn concentration (e.g., organic nutrient supply and pH) determined the ability of microorganisms to oxidize Mn in the streambeds. A survey of dissolved Mn in streams and water draining tea plantations combined with chemical analysis of Mn in the underlying soils indicate that the soils have been strongly acidified through excessive applications of N-fertilizers. As a result, Mn was leached from the soil column into the Kikukawa river system. Biogenic Mn-oxide coatings on streambeds can therefore serve as an indicator of soil acidification and metal leaching from soils of the corresponding watershed.

Bonding-state characterization of the constitutent elements of silicate minerals by X-ray photoelectron spectroscopy

X-ray photoelectron and X-ray-induced Auger electron spectra of silicate minerals have been measured. The systematic shifts of the photoelectron binding energies of Si, O and tetrahedrally coordinated Al ions in the silicate framework suggest that the negative charge on the framework is delocalized over these ions. On the other hand, it is deduced from the photoelectron binding and Auger electron kinetic energies that the octahedrally coordinated Al and Mg ions in the silicate mineral are not subject to a strong effect from the negative charge on the silicate framework. A comparison of the Na 1s binding and KL23L23 Auger kinetic energies of the exchangeable Na ion in the silicate mineral with those of sodium halides reveals that the bonding state of the exchangeable Na ion is comparable to those of Na ions in sodium chloride and fluoride.

Nuclear magnetic resonance and X-ray photoelectron spectroscopic investigation of lithium migration in montmorillonite

When Li-saturated montmorillonite is heated to 200–300 °C, the Li ions migrate from interlayer positions to sites in the layer structure. However, the identity of these sites has not been clearly established. Here we have investigated the migration of Li ions in montmorillonite, after heat treatment at 250 °C, using chemical and instrumental analyses. The latter include X-ray diffractometry (XRD), 7Linuclear magnetic resonance (NMR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Heating causes a large reduction in cation exchange capacity (CEC) and an almost complete loss of interlayer expansion with glycerol as shown by XRD. Static and magic angle spinning (MAS) 7Li-NMR spectroscopy shows that the quadrupole coupling constant of Li increases markedly over the corresponding value for unheated Li-montmorillonite (where Li occupies exchange sites in the interlayer space) and for hectorite (where Li is located in the octahedral sheet). This would indicate that, in heated montmorillonite, Li occupies structural sites of low symmetry which, however, cannot be identified with octahedral vacancies in the layer structure as is commonly assumed. XPS shows that the binding energy (BE) for Li in unheated montmorillonite is comparable to that for other exchangeable cations. Heating broadens the Li 1s band and decreases the BE. The BE for Li in heated montmorillonite is significantly higher than that in either spodumene or lepidolite, where Li is known to occupy octahedral sites. The combined data suggest that heating induces Li to migrate from interlayer sites to ditrigonal cavities in the tetrahedral sheet, rather than into vacancies in the octahedral sheet, of montmorillonite.

Surface characterization of acid-leached olivines by X-ray photoelectron spectroscopy

Abstract X-ray photoelectron spectroscopy was used to study the surface alteration of olivines (fayalite and forsterite) during acid dissolution (0.05 mol 1 −1 H 2 SO 4 at room temperature for one day). The abundances of Fe and Mg, relative to Si, in the near surface of olivines decreased after acid dissolution. The divalent cations in the fayalite were removed more readily than those in the forsterite. After acid dissolution, the Si 2s and O 1s spectra of fayalite were deconvoluted to contributions from unleached and leached phases. The Si 2s and O 1s binding energies were higher for the leached phase relative to the unleached phase, and comparable to those of silicon dioxide (quartz and silica gel), indicating that SiO 2 · n H 2 O formed on the mineral surface. Scanning electron micrographs of the leached olivine grains showed a harshly etched structure for fayalite and a locally etched structure for forsterite, indicating that the dissolution proceeded heterogeneously.

Production of Biogenic Manganese Oxides by Anamorphic Ascomycete Fungi Isolated from Streambed Pebbles

We characterized the production of biogenic Mn oxides by four anamorphic ascomycete fungi isolated from streambed pebbles with Mn oxide coatings. Based on the 18S rRNA gene sequences, one strain was related to members of the order Xylariales and the other three were within distinct lineages of the Pleosporales. These strains oxidized Mn(II) to deposit Mn oxides when their growth approached the stationary phase. The fungal Mn oxides showed X-ray diffraction patterns typical of poorly crystalline vernadite (δ -MnO2), and X-ray absorption near-edge structure spectroscopy confirmed that the Mn phases consisted predominantly of Mn(IV). Mn(II) oxidation in the four strains proceeded enzymatically. The Mn(II)-oxidizing proteins were inhibited by azide and o-phenanthroline, and the proteins also oxidized typical laccase substrates including 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), showing the role of laccase or a laccase-like metalloenzyme. The mineralogical traits of the biogenic Mn oxides, and the participation of laccase-like enzymes, are in accordance with our previous results obtained with one Hypocreales ascomycete. In conclusion, phylogenetically diverse ascomycetes may use this common enzymatic system to produce solid Mn phases similar to δ -MnO2.

Adsorption of some heavy metals by natural zeolites : XPS and batch studies

Abstract The adsorption of some heavy metal ions by mordenite and clinoptilolite has been investigated using batch techniques and X‐ray photoelectron spectroscopy (XPS). At 10‐5 M of Pb, Cu, Cd, and Zn, and in the presence of 10‐3 M Ca as a competing cation, the preferential sequence of adsorption was Pb > Cu > Cd > Zn for mordenite, and Pb > Cu > Zn > Cd for clinoptilolite. The adsorption capacities and removal efficiencies of the zeolites for the two highly toxic heavy metals, Cd and Pb, were also determined at a low‐to‐medium concentration range (10‐6 to 10‐3 M), and at a zeolite:solution ratio of 50:30 (mg:mL), in competition with 10‐3 M of Ca. Below 10‐4 M, both mordenite and clinoptilolite removed Pb from the solution almost completely. As Pb concentration increased, removal efficiency decreased. However, the zeolite samples (particularly mordenite) were not effective in reducing Cd concentrations to the legal μg/L level. Solution pHs and the photoelectron binding energies of adsorbed Pb(4f7/2) and ...

Characterization of arsenic in lake sediments by X-ray photoelectron spectroscopy

Arsenic in the sediments of Lake Usori (Usori-ko or Osoresan-ko) and Lake Mashu (Mashu-ko) has been characterized by X-ray photoelectron spectroscopy (XPS) and X-ray induced Auger electron spectroscopy and shown to exist as sulfide and arsenite, respectively. In the Lake Mashu sediment, surface concentration of As determined by XPS was significantly higher than the average concentration.

Removal of heavy metal cations by biogenic magnetite nanoparticles produced in Fe(III)-reducing microbial enrichment cultures

The biogenic magnetite nanoparticles presented here had a high capacity of adsorbing metal cations, which was approximately 30- to 40-fold greater than commercially available magnetite. These results suggest the potential application of microbial magnetite formation in the removal of toxic metal cations from water.