KTH Chemical Science and Engineering, Nuclear Chemistry, Royal Institute of Technology, SE-10044 Stockholm, Sweden.
J Contam Hydrol. 2010 Jul 30;116(1-4):16-23. doi: 10.1016/j.jconhyd.2010.04.007. Epub 2010 Jun 19.
Selenium is a trace element of concern in several geochemical contexts, due to the potentially high mobility of the selenium oxyanions and the narrow range between deficiency and toxicity of the element. For high level nuclear waste repositories the long-lived fission product 79Se has been identified as a potential key dose contributor for the long-term safety. This paper deals with the catalytic effect of Pd(s) on the H2 reduction of selenium oxyanions which was studied experimentally in aqueous solutions containing bicarbonate and chloride. Pd-catalysts and hydrogen have been proposed for the remediation of various groundwater contaminants and can also serve as a model substance for catalytic noble metal inclusions present in spent nuclear fuel. In this study selenite (SeO3(2)--) was found to adsorb on Pd. In the presence of hydrogen the rate of selenite removal increased yielding elemental Se. However, no adsorption or reduction of selenate (SeO4(2)--) was observed. A simple radiation chemical experiment revealed a notable barrier towards stepwise one-electron reduction of selenate to selenite. This provides an explanation for the lower reactivity of selenate in systems where reductive immobilization of selenite as well as selenate is thermodynamically favorable.
硒是几种地球化学环境中关注的微量元素，这是由于硒的含氧阴离子的潜在高迁移性和该元素的缺乏与毒性之间的狭窄范围。对于高水平核废料处置库，长寿命裂变产物 79Se 已被确定为长期安全的潜在关键剂量贡献者。本文研究了钯（s）对含有碳酸氢盐和氯化物的水溶液中硒含氧阴离子的 H2 还原的催化作用。钯催化剂和氢气已被提议用于修复各种地下水污染物，并且还可以作为存在于乏核燃料中的催化贵金属夹杂物的模型物质。在这项研究中，发现亚硒酸盐（SeO3（2）--）吸附在 Pd 上。在氢气存在下，亚硒酸盐的去除速率增加，生成元素硒。然而，没有观察到硒酸盐（SeO4（2）--）的吸附或还原。简单的辐射化学实验揭示了硒酸盐逐步单电子还原为亚硒酸盐的明显障碍。这为在热力学上有利于亚硒酸盐和硒酸盐的还原固定的系统中硒酸盐较低的反应性提供了解释。
