Enhanced Removal of Uranium(VI) by Nanoscale Zerovalent Iron Supported on Na鈥揃entonite and an Investigation of Mechanism

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• 作者：Gudong Sheng ; Xiaoyu Shao ; Yimin Li ; Jianfa Li ; Huaping Dong ; Wei Cheng ; Xing Gao ; Yuying Huang
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：April 24, 2014
• 年：2014
• 卷：118
• 期：16
• 页码：2952-2958
• 全文大小：342K
• 年卷期：v.118,no.16(April 24, 2014)
• ISSN：1520-5215

文摘

The reductive removal of U(VI) by nanoscale zerovalent iron (NZVI) was enhanced by using Na⁺-saturated bentonite (Na鈥揵ent) as the support, and the mechanism for the enhanced removal were investigated comprehensively. Under the same experimental conditions, NZVI supported on the negatively charged Na鈥揵ent showed much higher removal efficiency (99.2%) of cationic U(VI) than either bare NZVI (48.3%) or NZVI supported on the positively charged bentonite (Al鈥揵ent) did. Subsequent experimental investigations revealed the unique roles of bentonite on enhancing the reactivity and reusability of NZVI. First, Na鈥揵ent can buffer the pH in reaction media, besides preventing NZVI from aggregation. Second, Na鈥揵ent promoted the mass transfer of U(VI) from solution to NZVI surface, leading to the enhanced removal efficiency. Third, the bentonite may transfer some insoluble reduction products away from the iron surface according to X-ray absorption fine structure (XAFS) study. Finally, Na鈥揵ent as the adsorbent to Fe(II) makes it more reactive with U(VI), which enhanced stoichiometrically the reduction capacity of NZVI besides accelerating the reaction rate.