The present work highlights the utility of isothermal solution calorimetry as a reliable and convenient tool for the determination of enthalpy of extraction (ΔH_extr) of metal ions under biphasic solvent extraction conditions. In comparison to the conventional indirect method based on Van't Hoff isotherm analysis, calorimetric method offers the flexibility of direct enthalpy measurements under a variety of operating conditions. The ΔH_extr of Eu(III) at different HNO₃ concentrations was measured for N,N,N’,N’-tetraoctyldiglycolamide (TODGA) and N,N-di-octyl-2-hydroxyacetamide (DOHyA) solvents for the first time using this method. A strong dependence of ΔH_extr with changes in aqueous phase acidity as well as the concentration of solvent phase was discerned during the measurements. Parallel measurements using DLS spectroscopy divulged that the observed decrease in ΔH_extr is a consequence of the aggregation of extractants. The pivotal role of aggregation of solvents on the extraction enthalpy of solvent extraction systems was demonstrated by a comparison of the results in two solvent systems with different aggregation properties.

目前的工作强调了等温溶液量热法作为一种可靠且方便的工具的实用性，用于测定双相溶剂萃取条件下金属离子的萃取焓 (ΔH _{extr )。}与基于范特霍夫等温线分析的传统间接方法相比，量热法提供了在各种操作条件下直接进行焓测量的灵活性。首次测量了N,N,N',N'-四辛基二甘醇酰胺(TODGA)和N,N-二辛基-2-羟基乙酰胺(DOHyA)溶剂中Eu(III)在不同HNO ₃浓度下的ΔH _extr使用这种方法。_{在测量过程中发现 ΔH extr}与水相酸度以及溶剂相浓度的变化有很强的相关性。使用 DLS 光谱的平行测量表明，观察到的 ΔH _extr下降是萃取剂聚集的结果。通过比较具有不同聚集特性的两种溶剂系统的结果，证明了溶剂聚集对溶剂萃取系统的萃取焓的关键作用。