研究者詳細 - 市野　良一

論文 - 市野　良一

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Recovery of rare-earth elements from neodymium magnets using molten salt electrolysis 査読有り国際誌

Kamimoto Y., Itoh T., Kuroda K., Ichino R.

Journal of Material Cycles and Waste Management 19 巻 ( 3 ) 頁： 1017 - 1021 2017年7月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Material Cycles and Waste Management

Rare-earth elements are used in neodymium magnets, and these elements are critical to Japanese industry. In this study, we focused on the electrochemical behavior of neodymium magnets for the recovery of rare-earth elements using molten salt electrolysis. The influence of the rare-earth elemental composition of the neodymium magnets on their anodic polarization behavior and oxidation mechanism was studied. The use of potentiostatic electrolysis enabled selective leaching of rare-earth elements from neodymium magnets in the potential range from −1.8 to −0.8 V. The oxidation potential limits the oxidation stage, enabling rare-earth elements to be leached from mixed neodymium magnets simultaneously.

DOI： 10.1007/s10163-016-0563-3

Phosphorus removal and magnetic separation using magnetic schwertmannite 査読有り国際共著国際誌

Kamimoto Y., Yamauchi K., Hagio T., Ichino R., Min K.S., Kwon K.H., Kim Y.J., Jung Y.J.

Desalination and Water Treatment 63 巻頁： 463 - 468 2017年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Desalination and Water Treatment

Phosphorus is an eutrophication agent for aquatic environment. An adsorption method is used for phosphorus removal; however, solid–liquid separation of adsorbent and the limit of adsorption relative to particle size are problematic. This study focused on phosphorus removal using schwertmannite combined with magnetite (magnetic schwertmannite). Magnetite is a ferromagnetic material. The magnetic schwertmannite with more than 33.7 mass% of magnetite content demonstrated good magnetic separation. The optimum adsorption pH was found to be 2.5, and the adsorption amount decreased with increase in solution pH. The maximum adsorption amount for phosphate was observed to be 1.42 mmol/g, and the adsorption isotherm was approximated by the Langmuir equation. The maximum adsorption amount was more than twice that previously reported because the particle size used in the current study was smaller than that used previously.

DOI： 10.5004/dwt.2017.11452

Removal properties of phosphate with ettringite 査読有り国際共著国際誌

Kamimoto Y., Onda K., Ichino R., Min K.S., Kwon K.H., Jung Y.J.

Desalination and Water Treatment 63 巻頁： 478 - 482 2017年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Desalination and Water Treatment

This work has performed the feasibility of utilizing synthetic ettringite as an adsorbent for phosphate removal in lab-scale experiments. Studies were focused on the influence of solution pH for the removal properties of phosphate. Ettringite was stable in the alkaline condition, and it was quickly decomposed in acid condition. Calcium and aluminum compound was formed at each pH condition. Phosphate removal performance was increased with the increase of solution pH. It was shown that the phosphate removal mechanism was influenced not only ion-exchange but also phosphate compound formation. The inside of large size ettringite residue was kept ettringite structure, and the phosphate was removed by ettringite surface only.

DOI： 10.5004/dwt.2017.11454

Ti<inf>3</inf>AlC<inf>2</inf> MAX Phase: A surprising candidate material for highly selective and efficient gold recovery from strong acid solutions 査読有り国際共著国際誌 Open Access

Thaveemas P., Phouthavong V., Hagio T., Dechtrirat D., Chuenchom L., Nijpanich S., Chanlek N., Park J.H., Ichino R.

Separation and Purification Technology 343 巻 2024年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Separation and Purification Technology

Given the scarcity of natural gold sources and associated mining challenges, the recovery of gold from secondary sources, such as electronic equipment waste (e-waste), becomes imperative. E-waste is typically treated with aqua regia to obtain highly acidic gold-containing solutions, which are subsequently processed by various methods to recover gold. Gold recovery materials offer numerous benefits but often exhibit insufficient selectivity, efficiency, and cost-effectiveness. To address this problem, we herein used a nonmodified pristine Ti-Al-C MAX phase (Ti3AlC2) to realize the one-pot room-temperature recovery of gold from highly acidic solutions (pH < 1) in the form of easily collectable bulky ball-shaped Au0 aggregates. High gold selectivity (Kd = 2.03 × 106 mL/g) and extraction efficiency (∼99 %) were observed even in the presence of interfering metal ions (Pd2+, Pt4+, Co2+, Ni2+, Cu2+, Zn2+), and the maximum gold extraction capacity (>6000 mg/g) surpassed that of previously reported gold recovery materials. The recovered gold was highly pure (>90 mass%) and contained minimal amounts of the original MAX phase, which obviated the need for intensive postpurification. The results of instrumental analyses suggested that gold recovery relied on electron transfer, similar to cementation, and primarily involved the reduction of solution-phase Au3+ to Au0 via electron transfer from the Ti and Al of Ti3AlC2. Thus, our work demonstrates the significant potential of pristine Ti3AlC2 for the energy-efficient recovery of gold from highly acidic solutions and paves the way for the efficient valorization of e-waste.

DOI： 10.1016/j.seppur.2024.127113

Magnetically separable TiO<inf>2</inf>/SnO<inf>2</inf>/Fe<inf>3</inf>O<inf>4</inf>-based nanocomposite photocatalyst for organic dye removal under low-power ultraviolet-visible light irradiation 査読有り国際共著

Juabrum S., Nijpanich S., Chanlek N., Kidkhunthod P., Poo-arporn Y., Nakajima H., Rujirawat S., Yimnirun R., Nanan S., Pinitsoontorn S., Praserthdam P., Phouthavong V., Park J.H., Hagio T., Ichino R.

Journal of Water Process Engineering 66 巻 2024年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Water Process Engineering

The photocatalytic removal of organic dyes from wastewater is typically accomplished using metal-doped semiconductor and binary/ternary nanocomposite powders, which feature a high specific surface area to volume ratio but are difficult to recover and reuse. Herein, a separable and reusable TiO2/SnO2/Fe3O4-based nanocomposite photocatalyst with the average particle size of 12.50 nm was synthesized using a simple sol-gel method. XRD, XAS and XPS analysis show that the synthesized photocatalyst mainly composed of anatase TiO2, SnO2, hematite, and magnetite. Its ability to promote the photodegradation of a model organic dye, reactive red 141 (RR141), was also evaluated under low-power UV–visible light irradiation (15-W LED light bulb). The synergy between adsorption and photocatalytic processes resulted in efficient (93 % of RR141 and 91 % of Tetracycline removed after 240 min) and rapid pseudo-first-order rate constant degradation in comparison with commercial P25-TiO2 due to much narrower band gap energy, which were determined as 1.70 and 2.49 eV, allowing electron-hole pairs generation in the visible region. The nanocomposite could be easily recovered using an external magnet and reused at least five times with no significant drop in performance. Thus, this study paves the way for effective wastewater treatment under practically relevant conditions and contributes to the establishment of a greener society.

DOI： 10.1016/j.jwpe.2024.105883

Tribocatalytic Reaction Enabled by TiO<inf>2</inf> Nanoparticle for MoDTC-Derived Tribofilm Formation at ta-C/Steel Contact 査読有り国際共著 Open Access

Matsukawa D., Park J.H., Lee W.Y., Tokoroyama T., Kim J.I., Ichino R., Umehara N.

Coatings 14 巻 ( 6 ) 2024年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Coatings

Tribochemically produced triboproducts are becoming increasingly important in tribosystems and serve to improve system performance by preventing friction or wear. Diamond-like carbon (DLC) is chemically stable, which features a trade-off with tribological pros and cons. Chemically stable DLC is thermally stable and suppresses surface damage in a high-temperature operating environment; however, it causes a detrimental effect that hinders the formation of a competent tribofilm. In this study, we dispersed highly reactive TiO2 nanoparticles (TDONPs) in molybdenum dithiocarbamate (MoDTC)-containing lubricant for adhering triboproducts on the DLC surface. In addition, TDONPs contributed to the decomposition of triboproducts by promoting the decomposition of MoDTC through its catalytic role. Rutile TDONPs were more helpful in reducing friction than anatase TDONPs and improved the friction performance by up to ~100%.

DOI： 10.3390/coatings14060773

Removal of heavy metals by BEA zeolite/Fe<inf>3</inf>O<inf>4</inf> composite prepared via dry-gel conversion method using agrowaste-derived raw material 査読有り国際共著

Phouthavong V., Hagio T., Park J.H., Nijpanich S., Duangkhai K., Rujiravanit R., Thaveemas P., Chounlamany V., Kong L., Li L., Ichino R.

Solid State Sciences 149 巻 2024年3月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Solid State Sciences

Using agrochemicals are considered as an anthropogenic source of heavy metal contamination in water, and ecofriendly remediation tools for removal is desired. Here, we demonstrate material circulation by converting SiO2 extracted from agrowaste: rice husk ash, into an easily collectable adsorbent: BEA zeolite/Fe3O4 composite, through dry-gel conversion technique. In addition, the synthesized BEA zeolite/Fe3O4 composite was tested for removal of heavy metals for the first time. Instrumental analyses confirmed that incorporated Fe3O4 particles inside BEA zeolites showed no severe effects on its morphologies. Pseudo-second order kinetic and Langmuir isotherm models were found best described the adsorption of three typical toxic heavy metals: Pb(II), Cu(II), Zn(II). Moderate adsorption capacities of 0.675, 0.310, and 0.308 mmol/g for Pb(II), Cu(II), and Zn(II), respectively, following the selectivity order: Pb(II) > Cu(II) ≈ Zn(II) were obtained. The composite adsorbent exhibits magnetic collectability, reusability and stability, indicating its practicality for removal of heavy metals from water.

DOI： 10.1016/j.solidstatesciences.2024.107473

Super hardening of Fe–W alloy plating by phase transformation of amorphous to metal carbides-dispersed nanocrystalline alloys and application as promising alternative for hard chromium plating 査読有り

Park J.H., Kim J.I., Shinohara Y., Hagio T., Umehara N., Ichino R.

Surface and Coatings Technology 477 巻 2024年2月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Surface and Coatings Technology

Despite the superior hardness, wear resistance, and corrosion resistance of hard chromium (Cr) plating using toxic hexavalent chromium (Cr6+), the gradual restriction on the use of Cr6+ in industrial fields necessitates the development of an alternative, harmless plating material with excellent performance. Here, we report the fabrication of super-hard plating by the simple annealing of electrodeposited Fe–W–C plating as a promising alternative for hard Cr plating. Amorphous-structured Fe–W–C plating, including co-deposited citric acid-derived carbon, forms uniformly dispersed ternary metal carbides inside the plating during annealing, which changes the plating structure from amorphous to nano-carbide-dispersed alloys. The phase-transformed, nanocrystalline Fe–W–C alloy annealed at 700 °C exhibited a maximum hardness of 20.5 GPa, which surpassed the hardness of hard Cr plating (12.5 GPa). The ball-on-disc tribo-test and corrosion test results further demonstrated the superior wear and anti-corrosion properties of the carbide-dispersed Fe–W–C alloy plating compared with hard Cr plating. This study develops the applicability of this super-hard plating as a new hard coating material that overcomes the limitations of conventional metal plating without using any toxic chemical.

DOI： 10.1016/j.surfcoat.2024.130388

c面配向六方晶酸化タングステン膜の分子ふるい型分離膜としての可能性査読有り国際共著国際誌

萩尾健史, 國司寛人, 和田慎太郎, 寺尾年弘, 木下空, プッタヴーンワンパサート, ニッチパーニッチスーピンヤー, パクジェヒョク, 市野良一

ゼオライト 41 巻 ( 1 ) 頁： 9 - 19 2024年1月

担当区分：最終著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本ゼオライト学会

カーボンニュートラルおよび持続可能な社会の実現に向け，エネルギー消費の大きい分離プロセスの省エネルギー化や資源循環に貢献する分離膜は益々注目されている。その中で，膜材料の検討は分離特性を決定づける重要な研究要素の一つである。分子サイズのミクロ細孔を有する無機結晶（ミクロ多孔無機結晶）は分子ふるいとも呼ばれる有望な分離膜材料である。筆者らは，この分子ふるい型膜材料として新たに六方晶酸化タングステンの可能性を提案してきた。同材料は，結晶のc軸と並行な一軸細孔を有するため，そのc面配向膜は分子ふるい型分離膜として機能すると予想されるが，分離膜材料としては検討されてこなかった。本稿では，筆者らが種々の対策によって緻密なc面配向六方晶酸化タングステン膜の合成に挑戦し，液分離並びにガス分離への適用可否を検討した結果を紹介する。得られた膜は，水／酢酸の混合溶液から水を選択的に分離できることが確認された。また，各種液およびガス分子の透過特性を調査した結果，ミクロ細孔を利用した小分子向けの分子ふるい型分離膜として機能するであろうことを見出した。本発見は膜材料の選択肢拡大に寄与すると期待される。

DOI： 10.20731/zeoraito.41.1.9

Facile Synthesis of Spherical Porous Tricobalt Tetroxide and Metal Cobalt for High Quality Cobalt Production and Recycling 査読有り国際共著 Open Access

Matsunaga S., Suzuki T., Hagio T., Park J.H., Kamimoto Y., Ichino R., Takeshita K., Sato F., Sasaya K., Iguchi T., Tsunekawa M.

MATERIALS TRANSACTIONS 64 巻 ( 12 ) 頁： 2739 - 2747 2023年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：公益社団法人日本金属学会

Liquid-phase synthesis is suitable for controlling the morphological and structural properties of functional inorganic materials and such control is important because they strongly affect the functionality of the product. Cobalt-based materials is one group of materials that requires control of powder morphology and structure. Cobalt is an important metal element used in various industrial fields such as secondary batteries, superalloys, permanent magnets, hard metals, and catalysts. The ever-growing demand of cobalt highlights that there is an urgent necessity to develop high quality material synthesis methods and to secure cobalt resources for countries that rely on import like Japan. Especially, technologies to recycle cobalt in a form reusable for secondary batteries and catalysts are desired because further increase in demand is anticipated. Meanwhile, spherical porous tricobalt tetroxide secondary particles obtained by calcination of spherical cobalt carbonate precursors have been reported to be promising materials for battery applications. Moreover, porous metal cobalt obtained by hydrogen reduction of tricobalt tetroxide is known to be effective for catalyst applications. However, conventional methods to synthesize spherical cobalt carbonate requires addition of additives in the reaction mixtures or otherwise requires hydrothermal treatment in pressure vessels. These are unfavorable to develop a practical and sustainable process for cobalt-based material production and recycling. In this study, a facile room temperature synthesis method to prepare spherical cobalt carbonate precursors from solutions of cobalt chloride and ammonium hydrogen carbonate that does not require any additives or hydrothermal treatment is developed by optimizing the carbonate solution concentration, carbonate/cobalt salt molar ratio, and stirring time during reaction. Furthermore, we succeeded in obtaining porous tricobalt tetroxide and porous metal cobalt that carry on the exterior spherical morphology of the original cobalt carbonate precursor by calcination and hydrogen reduction. The developed process shall contribute to realize high quality cobalt-based material production and recycling.

DOI： 10.2320/matertrans.m-m2023809

AC Electromagnetic Field Controls the Biofilms on the Glass Surface by Escherichia coli & Staphylococcus epidermidis Inhibition Effect 査読有り国際共著 Open Access

Aoyama N., Kanematsu H., Barry D.M., Miura H., Ogawa A., Kogo T., Kawai R., Hagio T., Hirai N., Kato T., Yoshitake M., Ichino R.

Materials 16 巻 ( 21 ) 2023年11月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials

Biofilms, mainly comprised of bacteria, form on materials’ surfaces due to bacterial activity. They are generally composed of water, extracellular polymeric substances (polysaccharides, proteins, nucleic acids, and lipids), and bacteria. Some bacteria that form biofilms cause periodontal disease, corrosion of the metal materials that make up drains, and slippage. Inside of a biofilm is an environment conducive to the growth and propagation of bacteria. Problems with biofilms include the inability of disinfectants and antibiotics to act on them. Therefore, we have investigated the potential application of alternating electromagnetic fields for biofilm control. We obtained exciting results using various materials’ specimens and frequency conditions. Through these studies, we gradually understood that the combination of the type of bacteria, the kind of material, and the application of an electromagnetic field with various low frequencies (4 kHz–12 kHz) changes the circumstances of the onset of the biofilm suppression effect. In this study, relatively high frequencies (20 and 30 kHz) were applied to biofilms caused by Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis), and quantitative evaluation was performed using staining methods. The sample surfaces were analyzed by Raman spectroscopy using a Laser Raman spectrometer to confirm the presence of biofilms on the surface.

DOI： 10.3390/ma16217051

Gas permeation properties of c-plane aligned hexagonal tungsten oxide membranes formed by multi-stage synthesis 査読有り国際共著国際誌

Wada S., Hagio T., Kunishi H., Park J.H., Phouthavong V., Yamada Y., Terao T., Li X., Nijpanich S., Ichino R.

Journal of the Korean Ceramic Society 60 巻 ( 6 ) 頁： 967 - 978 2023年11月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Korean Ceramic Society

Crystalline microporous membranes are promising tools for gas separation because their molecular dimension pores allow us to accurately sieve molecules by size. Recently, microporous hexagonal WO3 was reported as a new potential membrane material and its membrane was found to enable separation of water from water/acetic acid mixtures. Pore size of hexagonal WO3 seemed to be also suitable for separation of small gasses; however, its gas permeation properties have not been reported. Additionally, densification of membranes by decreasing intercrystalline gaps are extremely important in gas separation. One effective method to densify polycrystalline membranes is to repeat membrane synthesis, namely multi-stage synthesis. Here, we attempt to prepare dense hexagonal WO3 membranes on porous tubular supports by multi-stage synthesis and examined their densification and gas permeation properties. Densification was confirmed by permeation of SF6 (gas molecule larger than pores of hexagonal WO3), and its potential for separating small gasses was considered from single gas permeation of He and He/SF6 permselectivity. The results indicated that the multi-stage synthesis is effective to densify the membranes and He/SF6 permselectivity reached 42.8 for three-stage synthesis under modified conditions, implying hexagonal WO3 is a potential membrane material for small gas separation.

DOI： 10.1007/s43207-023-00321-5

Synthesis of Sulfur-Doped Magnetic Iron Oxides for Efficient Removal of Lead from Aqueous Solutions 査読有り国際共著 Open Access

Xu J., Pan M., Zou C., Huang X., Hagio T., Ichino R., Kong L., Li L.

Water (Switzerland) 15 巻 ( 20 ) 2023年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Water (Switzerland)

Heavy metal pollution poses an environmental risk, and its efficient removal and facile separation from water remains a challenge. Magnetic iron oxide, an eco-friendly, relatively stable, and easy-separation material, has been regarded as one of the most applicable adsorbents for water treatment. However, the limited adsorption capacity has restricted its applications. Herein, sulfur-doped magnetic Fe3O4 (Sx–Fe3O4) adsorbent was fabricated using a calcination method for the efficient removal of Pb(II) from water. In contrast to undoped Fe3O4, the introduction of doped sulfur greatly enhanced the adsorption performance of S–Fe3O4 over four times, with a maximum capacity of 333.33 mg g−1, which was synthesized at 300 °C with a raw molar ratio of S–Fe of 5. Based on the structure and morphology analysis, it was demonstrated that sulfur was successfully doped into the Fe3O4 structures, which resulted in Fe3O4 with active sulfur sites accordingly contributing to the adsorption enhancement through the combination of strong soft–soft interactions between soft base sulfur and soft acid Pb(II) along with surface adsorption. Sx–Fe3O4 could maintain the adsorption performance in the presence of competing ions. Furthermore, although the sulfur doping process exhibited slight side effects on the magnetic property, magnetic Sx–Fe3O4 maintained the high separation potential. This study presented a promising strategy to enhance the adsorption performance of Fe3O4 through sulfur doping for Pb(II) removal from water.

DOI： 10.3390/w15203667

Preparation and Characterization of TiO<inf>2</inf>-Coated Hollow Glass Beads for Functionalization of Deproteinized Natural Rubber Latex via UVA-Activated Photocatalytic Degradation 査読有り国際共著 Open Access

Nijpanich S., Nimpaiboon A., Rojruthai P., Park J.H., Hagio T., Ichino R., Sakdapipanich J.

Polymers 15 巻 ( 19 ) 2023年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Polymers

The photochemical degradation of natural rubber (NR) is a prevalent method used to modify its inherent properties. Natural rubber, predominantly derived from the Hevea Brasiliensis tree, exhibits an exceptionally high molecular weight (MW), often reaching a million daltons (Da). This high MW restricts its solubility in various solvents and its reactivity with polar compounds, thereby constraining its versatile applications. In our previous work, we employed TiO2 in its powdered form as a photocatalyst for the functionalization of NR latex. However, the post-process separation and reuse of this powder present substantial challenges. In this present study, we aimed to functionalize deproteinized NR (DPNR) latex. We systematically reduced its MW via photochemical degradation under UVA irradiation facilitated by H2O2. To enhance the efficiency of the degradation process, we introduced TiO2-coated hollow glass beads (TiO2-HGBs) as photocatalysts. This approach offers the advantage of easy collection and repeated reuse. The modified DPNR showed a reduction in its number-average MW from 9.48 × 105 to 0.28 × 105 Da and incorporated functional groups, including hydroxyl, carbonyl, and epoxide. Remarkably, the TiO2-HGBs maintained their performance over seven cycles of reuse. Due to their superior efficacy, TiO2-HGBs stand out as promising photocatalysts for the advanced functionalization of NR across various practical applications.

DOI： 10.3390/polym15193885

Room-Temperature Bulk Supramolecular Polymer Based on C<inf>3</inf>-Symmetrical Benzene-1,3,5-tricarboxamides Having Two-Armed Alkyl Groups as Side Chains 査読有り国際誌

Ishigaki Y., Yamanaka M., Hagio T., Ichino R.

ChemistrySelect 8 巻 ( 35 ) 2023年9月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ChemistrySelect

To develop a bulk supramolecular polymer based on 1,3,5-benzenetricarboxamide (BTA) without crystallinity at room temperature, C3-synmetrical BTA derivatives with two-armed alkyl groups were synthesized and characterized. IR and XRD measurements of the BTA derivatives suggested that the higher-order structure obtained using these materials was hexagonal columnar, owing to the characteristic three-fold hydrogen bonding. In DSC measurements, BTA having 10-nonadecyl groups (10NDBTA) showed only a single transition point at 233 °C and maintained its mesophase down to −50 °C, whereas the other BTA derivatives showed a transition peak in the range of 20 to 131 °C and another in the range of 204 to 239 °C, corresponding to alkyl melting and dissociation of the stacked BTA cores, respectively. 13C-SSNMR measurement of 10NDBTA indicated that not only the 10-nonadecyl groups of the side chains but also the BTA cores forming the main chain of the supramolecular polymer show a unique high mobility even at ambient temperature.

DOI： 10.1002/slct.202300805

Utilization of agricultural waste to herbicide removal: Magnetic BEA zeolite adsorbents prepared by dry-gel conversion using rice husk ash–derived SiO<inf>2</inf> for paraquat removal 査読有り国際共著国際誌 Open Access

Phouthavong V., Hagio T., Park J.H., Nijpanich S., Srihirunthanon T., Chantanurak N., Duangkhai K., Rujiravanit R., Chounlamany V., Phomkeona K., Kong L., Li L., Ichino R.

Arabian Journal of Chemistry 16 巻 ( 8 ) 2023年8月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Arabian Journal of Chemistry

This study presents a method that will allow for the sustainable utilization of rice husk ash-SiO2 (RHAS), an agricultural-waste–derived material, as a bulky solid SiO2 source in the zeolite beta (BEA)/Fe3O4 composite (magnetic RHAS-BEA) synthesis via a dry-gel conversion method for the removal of paraquat, a typical herbicide, from aqueous solutions. Ultrasonic waves were used to facilitate the formation of uniform Fe3O4-contained dry precursor gel before converting to the magnetic BEA zeolite composite for the first time. Magnetic RHAS-BEA was then characterized and compared with a non-magnetic sample (RHAS-BEA) using X-ray diffraction and field-emission scanning electron microscopy. In terms of adsorption, we found that paraquat had a high adsorption rate on the samples and conformed to a pseudo-second-order kinetic model. The adsorption behavior of paraquat on the synthesized RHAS-BEA and magnetic RHAS-BEA obeyed the Langmuir adsorption isotherm model. The synthesized adsorbents were reusable for at least four cycles, via thermal regeneration at 450 °C. The inclusion of Fe3O4 particles in magnetic RHAS-BEA disrupted neither the crystallization of the BEA zeolite nor the adsorption of paraquat and enabled easy collection via an external magnet.

DOI： 10.1016/j.arabjc.2023.104959

An effective strategy for improving the performance of electrodeposited Fe-W alloy plating: Tailoring microstructure by graphene incorporation 査読有り国際共著国際誌 Open Access

Shinohara Y., Park J.H., Hagio T., Kim J.I., Lee W.Y., Umehara N., Ichino R.

Materials and Design 230 巻 2023年6月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials and Design

Despite the excellent performance of hard Cr plating using hexavalent chromium (Cr6+), its use is being restricted owing to recent environmental regulations. Electrodeposited Fe-W alloy is considered a possible alternative, but its high coefficient of friction (COF), high wear rate owing to tribo-oxidation, and high corrosion rate hinder its practical application. In this study, we attempted to solve these problems by modifying the microstructure of Fe-W alloy by incorporating 2D-structured graphene. The effect of graphene incorporation on the structure of the Fe-W alloy and its properties, especially microhardness, wear, and corrosion resistance, were investigated. The results showed the graphene effectively modified the columnar structure of the Fe-W alloy by inhibiting the vertical growth of clusters during electrodeposition, leading to fragmentation of the vertical cluster boundaries. This improved the hardness by as much as 17 % up to 9.1 GPa, and the corrosion resistance by changing the corrosion mechanism from localized corrosion to uniform corrosion. In addition, the graphene reduced the COF and wear rate by reducing the Fe2O3 formed by tribo-oxidation to a lower oxidation state. The structural modification of the plating by graphene incorporation thus provides an effective solution to improving the performance of Fe-W alloys.

DOI： 10.1016/j.matdes.2023.111938

Improvement in the corrosion resistance of electrodeposited Ni-W alloy by MWCNT co-deposition and prevention of metal-carbon interfacial corrosion by carbide formation 査読有り

Park J.H., Hagio T., Ichino R.

Journal of Alloys and Compounds 939 巻 2023年4月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Alloys and Compounds

Composite plating is an effective method which can enhance the properties of conventional metal plating by co-deposition of composite materials. In this study, multi-walled carbon nanotubes (MWCNTs) were used as a composite material to improve the corrosion resistance of Ni-W alloys, and the effect of the MWCNTs addition on the anti-corrosion properties was discussed. The corrosion current density of the Ni-W/MWCNTs composite decreased approximately 4 times from 16.6 to 4.6 μA·cm-2 in 3 wt% NaCl solution compared to the pristine Ni-W; this showed that the co-deposition of MWCNTs was effective for improvement in the corrosion resistance. However, the interfacial corrosion between the metal matrix and MWCNTs occurred in the high potential region and degraded the passivation properties of plating. This interfacial corrosion is caused by the high O content due to the hydroxyl groups on the acid-treated MWCNTs surface and the difference in W concentration between the interface of MWCNTs and the Ni-W matrix. Heat treatment in Ar atmosphere removes these hydroxyl groups and diffuses Ni and W into MWCNTs to form metal carbide (Ni6W6C), effectively alleviating interfacial corrosion. This study presents interfacial corrosion can be effectively mitigated by forming metal carbides at the interface of carbon materials in metal/carbon composites.

DOI： 10.1016/j.jallcom.2023.168788

Preliminary Study on Electrodeposition of Copper Platings and Codeposition of Carbon Nanotubes from Organic Solvent 査読有り国際誌 Open Access

Park J.H., Fujita Y., Hagio T., Phouthavong V., Kamimoto Y., Bessho T., Ichino R.

Coatings 13 巻 ( 4 ) 2023年4月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Coatings

Metal/carbon composite plating is an effective strategy for improving and adding properties to metal plating by incorporating carbon materials into the metal matrices. Copper (Cu) is widely applied, particularly in the areas of heat management and electronic packaging owing to its high thermal and electrical conductivities, which can be further improved together with improvements in mechanical properties by compositing it with carbon nanotubes (CNTs). However, because hydrophobic CNTs are hardly dispersible in aqueous solutions, additional intense acid treatment or the addition of dispersants is required for their dispersion. Moreover, previous studies have reported that these methods suffer from deterioration of composite material performance through the destruction of the CNT surface or the inclusion of dispersants into the plating. Therefore, in this study, the electrodeposition of a Cu/CNT composite in a non-aqueous solvent that can disperse CNTs without any additional treatment is investigated. The experimental results show that it is possible to deposit Cu from a N-methyl-2-pyrrolidone containing copper iodide and potassium iodide. Furthermore, Cu/CNT composite platings containing CNTs up to 0.12 mass% were prepared by constant current electrolysis, and applying pulse electrolysis can increase the CNTs content up to 0.22 mass%.

DOI： 10.3390/coatings13040802

Dry-gel conversion synthesis of magnetic BEA-type zeolites for antibiotics adsorption 査読有り国際共著

Phouthavong V., Hagio T., Nijpanich S., Park J.H., Hiraiwa M., Srihirunthanon T., Chantanurak N., Rujiravanit R., Kamimoto Y., Li X., Kong L., Li L., Ichino R.

Journal of Sol-Gel Science and Technology 105 巻 ( 2 ) 頁： 511 - 524 2023年2月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Sol-Gel Science and Technology

The dry-gel conversion method (DGC) is a promising synthesis protocol for preparing magnetic zeolite composites as it yields homogeneous composite particles with more rapid crystallization, smaller reactor volume, and less waste production than the conventional hydrothermal method. This work investigates the optimal conditions for preparing magnetic BEA-type zeolites using the DGC method, including the gel/water ratio, crystallization temperature and time. Precursor dry-gel incorporating well-dispersed magnetite was subjected to crystallization under water vapor atmosphere with a gel/water ratio of 0.5–2, crystallization temperature of 140–200 °C for 1.5–12 h, followed by characterization using X-ray diffraction and scanning electron microscopy. The optimum conditions were found to be gel/water ratio of 1 and crystallization at 180 °C for 12 h. Magnetic properties of collected samples were evaluated using a vibrating-sample magnetometer after calcination at 400–500 °C for 12 h. Products calcined below 450 °C showed good magnetic properties. Adsorption of sulfadiazine using the BEA and magnetic BEA-type zeolites was evaluated in a 10–50 mg/l range. Results revealed favorable multilayer-type adsorption of sulfadiazine onto both non-magnetic and magnetic BEA-type zeolites (Freundlich model). These indicate that DGC method is suitable for preparing high-silica magnetic BEA-type zeolites with potential for antibiotic removal. Graphical Abstract: [Figure not available: see fulltext.].

DOI： 10.1007/s10971-022-06025-2

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