Japan Geoscience Union Meeting 2016

Presentation information


Symbol B (Biogeosciences) » B-CG Complex & General

[B-CG09] Interrelation between Life, Water, Mineral, and Atmosphere

Mon. May 23, 2016 3:30 PM - 5:00 PM A02 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Kentaro Nakamura(Department of Systems Innovation, School of Engineering, University of Tokyo), Tsubasa Otake(Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University), Yohey Suzuki(Graduate School of Science, The University of Tokyo), Ken Takai(Extremobiosphere Research Center, Japan Agency for Marine-Earth Science & Technology), Yuichiro Ueno(Department of Earth and Planetary Sciences, Tokyo Institute of Technology), Takeshi Naganuma(Graduate School of Biosphere Science), Takeshi Kakegawa(Graduate School of Science, Tohoku University), Tadashi Yokoyama(Department of Earth and Space Science, Graduate School of Science, Osaka University), Fumito Shiraishi(Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University), Chair:Kentaro Nakamura(Department of Systems Innovation, School of Engineering, University of Tokyo)

4:30 PM - 4:45 PM

[BCG09-10] Selenite sorption on magneaium oxide under the highly alkaline conditions

*Shun Miyasita1, Kesuke Fukushi2, Shoji Morodome3 (1.Division of Environmental Science and Engineering, Graduate School of Natural Science and Technology, Kanazawa University, 2.Institute of Nature and Environmetal Technology, Kanazawa University, 3.Kunimine Industries co., LTD.)

Keywords:Selenite, Magnesium Oxide, Metastable Phase, Magnesium Hydroxide, Alkaline Conditions

Selenium occurs widely throughout nature. It is one of essential the elements for human, but it shows toxicity at degree to double of the necessary quantity. Selenium is environmental standard designation item.
After earthquake disaster, the contribution of the nuclear power generation in the electricity source of supply in Japan decrease, while that the thermal power generation increases. In coal-fired station, the selenium concentrations more than industry waste water regulation (100ppb) in the drainage has been reported to occur in a desulfurization processes of the gases which is generated during burnt coral (Central Research Institute of Electric Power Industry, 2005). The solutions used in the desulfurization processes is kept alkaline in order to facilitate the dissolution gases.
Selenium mainly exists as selenite(HxSeO42-x, Se(Ⅵ)) or selenite(HySeO32-y, Se(Ⅳ)) in solution. Most of selenium exists as selenite in waste water in desulfurization process (Central Research Institute of Electric Power Industry, 2005). A general selenite removal method in the solution includes the adsorption on iron oxide. However, adsorption significantly decrease under the alkali condition because the surface charge of iron oxide become to minus at alkaline conditions (Fukushi, 2008). Therefore, the effective removal of selenite under the alkali condition is expected.
The anions of which oxygens coordinate to the center atom are called oxyanions. There are many oxyanions which cause the water pollutions, e.g., arsenite and bronate. It is reported that magnesium oxide (MgO) has ability for the removals of aresnite and bronate (Liu et al., 2011; Fuente and Eugenio, 2006). It can be expected that MgO has ability for removal for selenite in solution. MgO is metastable phase under the Earth surface environmental, and it transforms to brucite (Mg(OH)2) in solution with time (Yabe et al., 2011). Liu et al., (2011) studied the removal of arsenite from solution by MgO with high sace area. They suggested that the tranformation in solution is related to the uptake of arsenite, i.e., the sorption mechanism of aresenite on MgO under the high arsenite concentration condition is formation of an “arsenite-Mg compound” following transformation to Mg(OH)2. Their study was conducted under the very high sorbate concentration (>1ppm) condition. There were no arguments about the mechanisms under the low concentration condition with sub-ppm order. The water pollution related to selenium mainly becomes problem with low concentration around the waste water satandards (100ppm order). It is thought that understanding the sorption behavior in the low concentration condition is necessary. I conducted bacth sorption experiments of selenite by MgO and magnesium hydroxide which is stable phase in this study to examine the selenite uptake behavior and mechanism on MgO.