Sorption of Eu(III) on Granite: EPMA, LA鈥揑CP鈥揗S, Batch and Modeling Studies
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- 作者：Keisuke Fukushi ; Yusuke Hasegawa ; Koushi Maeda ; Yusuke Aoi ; Akihiro Tamura ; Shoji Arai ; Yuhei Yamamoto ; Daisuke Aosai ; Takashi Mizuno
- 刊名：Environmental Science & Technology
- 出版年：2013
- 出版时间：November 19, 2013
- 年：2013
- 卷：47
- 期：22
- 页码：12811-12818
- 全文大小：414K
- 年卷期：v.47,no.22(November 19, 2013)
- ISSN：1520-5851
文摘
Eu(III) sorption on granite was assessed using combined microscopic and macroscopic approaches in neutral to acidic conditions where the mobility of Eu(III) is generally considered to be high. Polished thin sections of the granite were reacted with solutions containing 10 渭M of Eu(III) and were analyzed using EPMA and LA鈥揑CP鈥揗S. On most of the biotite grains, Eu enrichment up to 6 wt % was observed. The Eu-enriched parts of biotite commonly lose K, which is the interlayer cation of biotite, indicating that the sorption mode of Eu(III) by the biotite is cation exchange in the interlayer. The distributions of Eu appeared along the original cracks of the biotite. Those occurrences indicate that the prior water鈥搑ock interaction along the cracks engendered modification of biotite to possess affinity to the Eu(III). Batch Eu(III) sorption experiments on granite and biotite powders were conducted as functions of pH, Eu(III) loading, and ionic strength. The macroscopic sorption behavior of biotite was consistent with that of granite. At pH > 4, there was little pH dependence but strong ionic strength dependence of Eu(III) sorption. At pH < 4, the sorption of Eu(III) abruptly decreased with decreased pH. The sorption behavior at pH > 4 was reproducible reasonably by the modeling considering single-site cation exchange reactions. The decrease of Eu(III) sorption at pH < 4 was explained by the occupation of exchangeable sites by dissolved cationic species such as Al and Fe from granite and biotite in low-pH conditions. Granites are complex mineral assemblages. However, the combined microscopic and macroscopic approaches revealed that elementary reactions by a single mineral phase can be representative of the bulk sorption reaction in complex mineral assemblages.