Hideki Koyanaka

Characteristics of a bioxalate chelating extraction process for removal of chromium, copper and arsenic from treated wood

The disposal of wood waste treated with chromated copper arsenate (CCA) is a problem in many countries. We have proposed a novel chelating extraction technique for CCA-treated wood using bioxalate, a solution of oxalic acid containing sufficient sodium hydroxide to adjust the pH to 3.2, which is an effective way to obtain an extraction efficiency of 90% for chromium, copper, and arsenic. The purpose of the present study was to investigate the characteristics of bioxalate extraction of CCA-treated wood. Extractions of CCA-treated western hemlock chips with solutions of bioxalate, oxalic acid, and sodium hydroxide were carried out. The use of bioxalate was confirmed as the most effective extraction technique for chromium, copper and arsenic, with an efficiency of 90%. Extraction with simple oxalic acid was ineffective for copper (less than 40% extraction efficiency), but effective for chromium and arsenic, with 90% efficiency. Sodium hydroxide showed a similar tendency, being ineffective for chromium and copper (less than 20% extraction efficiency), but relatively effective for arsenic (around 70-80% efficiency). We also discovered an interesting phenomenon whereby the addition of sodium hydroxide to a simple oxalic acid solution during the oxalic acid extraction progress resulted in dramatically increased extraction efficiency for copper, chromium and arsenic, up to 90%. Although oxalic acid was ineffective for copper extraction, the addition of sodium hydroxide during the oxalic acid extraction process rendered it effective.

Hydrogen Gas Sensor using Nano-sized R-MnO2 Powder

Nano-powder of R-type manganese dioxide (RMO) was used for a hydrogen gas sensor. We prepared a pellet (diameter: 2 cm, thickness: 0.5mm) of RMO, and set it in between a couple of Pt mesh sheets to make a SOFC cell. The cell showed a maximum output voltage of 0.3V with good response to hydrogen gas supplied at room temperature. We measured the variation of the output voltage by using different concentration of hydrogen gas (0.1- 99.9 %) and their flow rate (10- 100 ml/min). Furthermore, other crystal structure types of manganese dioxide were tested for comparison. Consequently, only RMO showed good suitability as a hydrogen gas sensor, usable over a wide range of hydrogen gas concentrations.

5.5.3 Proton conduction in electrolyte made of manganese dioxide for hydrogen gas sensor

We propose a network model of oxygen-pairs to store and conduct protons on the surface of manganese dioxide with a weak covalent bond like protons stored in pressured ice. The atomic distances of oxygen-pairs were estimated between 2.57 and 2.60 angstroms in crystal structures of ramsdellite-type and lambda-type manganese dioxides by using protonated samples and inelastic neutron scattering measurements. Good properties for a hydrogen gas sensor using electrolytes made of manganese dioxides that contain such oxygen-pairs were confirmed experimentally.

Direct-DME SOFC for Intermediate Operation Temperature Using Proton Conductor as the Electrolyte

Faculty of Industrial Science and Technology, Tokyo University of Science, 102-1 Tomino, Oshamanbe, Hokkaido 049-3514, Japan Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan Department of Frontier Materials and Functional Engineering, Graduate School of Engineering, Iwate University, Morioka, Iwate 020-8551, Japan Institute for Integrated Cell-Material Sciences, Kyoto University, Kyoto, 606-8501, Japan