Department of Environmental Engineering and Earth Sciences, Clemson University, 342 Computer Court, Anderson, South Carolina 29625, United States.
Department of Chemistry, Clemson University, 219 Hunter Laboratories, Clemson, South Carolina 29634, United States.
Environ Sci Technol. 2020 Dec 1;54(23):15004-15012. doi: 10.1021/acs.est.0c04429. Epub 2020 Nov 9.
The influence of temperature on the adsorption of metal ions at the solid-water interface is often overlooked, despite the important role that adsorption plays in metal-ion fate and transport in the natural environment where temperatures vary widely. Herein, we examine the temperature-dependent adsorption of uranium, a widespread radioactive contaminant, onto the ubiquitous iron oxide, hematite. The multitemperature batch adsorption data and surface complexation models indicate that the adsorption of uranium, as the hexavalent uranyl (UO) ion, increases significantly with increasing temperature, with an adsorption enthalpy (Δ) of +71 kJ mol. We suggest that this endothermic, entropically driven adsorption behavior is linked to reorganization of the uranyl-ion hydration and interfacial water structures upon U adsorption at the hematite surface. Overall, this work provides fundamental insight into the thermodynamics driving metal-ion adsorption reactions and provides the specific enthalpy value necessary for improved predictive geochemical modeling of U adsorption in the environment.
温度对固-水界面上金属离子吸附的影响常常被忽视，尽管吸附在自然环境中金属离子的归宿和迁移中起着重要作用，而自然环境中的温度变化范围很广。在此，我们研究了普遍存在的氧化铁、赤铁矿对广泛存在的放射性污染物铀的温度依赖型吸附。多温度批吸附数据和表面络合模型表明，铀（六价铀酰UO22+）的吸附随着温度的升高而显著增加，吸附焓（ΔH）为+71 kJ/mol。我们认为，这种吸热的、熵驱动的吸附行为与铀酰离子水合和界面水结构在赤铁矿表面吸附铀时的重新组合有关。总的来说，这项工作为金属离子吸附反应的热力学驱动力提供了基本的认识，并为改善环境中铀吸附的预测地球化学模型提供了必要的特定焓值。
