Effect of particle size on the colonization of biofilms and the potential of biofilm-covered microplastics as metal carriers

Wu, C.*; Tanaka, Kazuya; Tani, Yukinori*; Bi, X.*; Liu, J.*; Yu, Q.*

Science of the Total Environment, 821, p.153265_1 - 153265_9, 2022/05

https://doi.org/10.1016/j.scitotenv.2022.153265

Microplastics (MPs) with different particle sizes were co-cultured with a model freshwater fungus, strain KR21-2, to form biofilms on their surface. We also determined the changes in surface physicochemical properties of the biofilm-covered MPs (BMPs) and the heavy metal adsorption capacity of the original MPs and BMPs. The results revealed that the biofilms improve the adsorption of heavy metals on MPs, and the particle size of MPs plays a crucial role in biofilm colonization and adsorption of heavy metals by BMPs.

Sorption of Pu(IV) on biogenic Mn oxide and complexation of Pu(IV) with organic ligands secreted by fungal cells

Tanaka, Kazuya; Tani, Yukinori*; Kozai, Naofumi; Onuki, Toshihiko

Journal of Radioanalytical and Nuclear Chemistry, 331(2), p.1109 - 1114, 2022/02

https://doi.org/10.1007/s10967-021-08178-w

We investigated the sorption of Pu(IV) on biogenic Mn oxide produced by Mn(II)-oxidizing fungus. The sorption of Pu(IV) on biogenic Mn oxide was similar to that of U(VI) and different from that of Th(IV), possibly due to oxidation of Pu(IV) to Pu(VI). When Pu(IV) was sorbed on hyphae only, it was desorbed into the solution phase over time. Pu(IV) could be solubilized by complexation with organic ligands secreted by fungal cells. In particular, Pu(IV) desorption was observed under circumneutral pH conditions.

Sequestration and oxidation of Cr(III) by fungal Mn oxides with Mn(II) oxidizing activity

Suzuki, Ryohei*; Tani, Yukinori*; Naito, Hirotaka*; Miyata, Naoyuki*; Tanaka, Kazuya

Catalysts, 10(1), p.44_1 - 44_15, 2020/01

https://doi.org/10.3390/catal10010044

We prepared biogenic Mn oxides (BMOs) using strain KR21-2, and subsequently conducted single or repeated treatment experiments in Cr(NO) at pH6.0. Under aerobic conditions, newly formed BMOs exhibited a rapid production of Cr(VI) without a significant release of Mn(II), demonstrating that newly formed BMO mediates a catalytic oxidation of Cr(III) with a self-regeneration step of reduced Mn. In anaerobic solution, newly formed BMOs showed a cessation of Cr(III) oxidation in the early stage of the reaction, and subsequently had a much smaller Cr(VI) production with significant release of reduced Mn(II).

Hydrological and climate changes in southeast Siberia over the last 33 kyr

Katsuta, Nagayoshi*; Ikeda, Hisashi*; Shibata, Kenji*; Kokubu, Yoko; Murakami, Takuma*; Tani, Yukinori*; Takano, Masao*; Nakamura, Toshio*; Tanaka, Atsushi*; Naito, Sayuri*; et al.

Global and Planetary Change, 164, p.11 - 26, 2018/05

https://doi.org/10.1016/j.gloplacha.2018.02.012

Paleoenvironmental and paleoclimate changes in Siberia were reconstructed by continuous, high-resolution records of chemical compositions from a sediment core retrieved from the Buguldeika Saddle, Lake Baikal, dating back to the last 33 cal. ka BP. The Holocene climate followed by a shift at ca. 6.5 cal. ka BP toward warm and dry, suggesting that the climate system transition from the glacial to interglacial state occurred. In the last glacial period, the deposition of carbonate mud from the Primorsky Range was associated with Heinrich events (H3 and H1) and the Selenga River inflow was caused by meltwater of mountain glaciers in the Khamar-Daban Range. The anoxic bottom-water during Allerod-Younger Dryas was probably a result of weakened ventilation associated with reduced Selenga River inflow and microbial decomposition of organic matters from the Primorsky Range. The rapid decline in precipitation during the early Holocene may have been a response to the 8.2 ka cooling event.

Thermal expansion of a Au-Al-Yb intermediate valence quasicrystal

Watanuki, Tetsu; Kashimoto, Shiro*; Ishimasa, Tsutomu*; Machida, Akihiko; Yamamoto, Shin*; Tanaka, Yukinori*; Mizumaki, Masaichiro*; Kawamura, Naomi*; Watanabe, Shinji*

Solid State Communications, 211, p.19 - 22, 2015/06

https://doi.org/10.1016/j.ssc.2015.03.008

The thermal expansion of a Au-Al-Yb intermediate-valence quasicrystal has been studied by X-ray diffraction measurements. We have found anomalous thermal expansion behavior, namely zero thermal expansion below 50 K. By comparison with an isostructural Au-Al-Tm quasicrystal, the contribution of the Yb valence variation was extracted, and it was shown that its negative thermal expansion component due to the valence shift toward the divalent state by cooling compensated for the positive thermal expansion of the original lattice.

Specific sorption behavior of actinoids on biogenic Mn oxide

Tanaka, Kazuya*; Tani, Yukinori*; Onuki, Toshihiko

Chemistry Letters, 40(8), p.806 - 807, 2011/08

https://doi.org/10.1246/cl.2011.806

We made sorption experiments of actinides on Mn oxide in dilute NaCl solution. Sorption affinity of actinides on synthetic Mn oxide was Th(IV) U(VI) Np(V). The specific sorption behavior of actinides on biogenic Mn oxide was observed. Thorium sorbed on biogenic Mn oxide was desorbed into solution with increasing time. Neptunium was not sorbed on biogenic Mn oxide. The specific sorption behavior is possibly due to organic ligands released from microorganisms and surface property of biogenic Mn oxide.

Ce oxidation by Mn oxide produced by Acremonium sp. strain KR21-2

Tanaka, Kazuya; Tani, Yukinori*; Onuki, Toshihiko

no journal, , 

no abstracts in English

Fungus activity promoted transformation of REEs during bio-oxidation of Mn(II)

Yu, Q.; Onuki, Toshihiko; Tanaka, Kazuya*; Kozai, Naofumi; Sakamoto, Fuminori; Tani, Yukinori*

no journal, , 

Intermediate-valence icosahedral Au-Al-Yb quasicrystal

Watanuki, Tetsu; Kashimoto, Shiro*; Yamazaki, Teruo*; Kawana, Daichi*; Machida, Akihiko; Tanaka, Yukinori*; Ishimasa, Tsutomu*; Sato, Taku*

no journal, , 

A quasiperiodic, intermediate-valence (IV) system is realized in an icosahedral Au-Al-Yb quasicrystal. X-ray absorption spectroscopy near the Yb L3-edge indicates that quasiperiodically arranged Yb ions assume a mean valence of 2.61, between a divalent state (4f14, J = 0) and a trivalent one (4f13, J = 7/2). Magnetization measurements demonstrate that the 4f holes in this quasicrystal have a localized character. The magnetic susceptibility shows a Curie-Weiss behavior above 100 K with an effective magnetic moment of 3.81 muB per Yb. Moreover, a crystalline approximant to this quasicrystal is an IV compound. We propose a heterogeneous IV model for the quasicrystal, whereas the crystalline approximant is most likely a homogeneous IV system. At temperatures below 10 K, specific heat and magnetization measurements reveal non-Fermi-liquid behavior in both the quasicrystal and its crystalline approximant without either doping, pressure, or field tuning.

Application of solvent extraction to the recycling process of electroless nickel plating baths

Naganawa, Hirochika; Tanaka, Mikiya*; Saki, Yukinori*

no journal, , 

Electroless nickel plating is an important surface finishing technology; however, the treatment of a large amount of spent baths should be established from both the environmental and economic viewpoints. Solvent extraction is a useful separation technology which utilizes the distribution of a solute between aqueous and organic phases. The present authors have developed a nickel recycling process from the spent baths using solvent extraction. This process was applied to a plating plant initially using a conventional mixer-settler and then a new apparatus called emulsion flow extractor. In this presentation, the laboratory-scale experimental results and practical operation data will be presented.