Cation Identity Affects Nonadditivity in Salt Mixtures Containing Iodide and Sulfate
Cation Identity Affects Nonadditivity in Salt Mixtures Containing Iodide and Sulfate
复制标题
DOI：
10.1007/s10953-021-01125-z
复制
发表时间：
2021-11-12
影响因子：
1.2
通讯作者：
Cremer, Paul S.
中科院分区：
文献类型：
--
作者：
Bui, Pho T.;Cremer, Paul S.
在含盐混合溶液中测定了聚n -异丙基丙烯酰胺的云点温度。溶液由SO42-，强水合阴离子，I-，弱水合阴离子，或两种阴离子和常见的碱金属反离子Li+， Na+， K+或Cs+组成。在0.2 mol.L-1 M2SO4的存在下，增加MI浓度，观察到无加性行为。虽然在所有四种金属反阳离子中都观察到云点温度的复杂变化，但它们之间的影响程度有很大差异。更具体地说，在每种情况下，SO42-都能从I-中吸引阳离子，但其倾向取决于阳离子-碘化物与阳离子-硫酸盐相互作用的相对强度。当反离子从它身上剥离出来时，I-变得更加水合，表现得更像一个强水合阴离子。采用竞争结合模型来确定在I-存在的情况下与SO42-结合的阳离子的比例，从而可以对所有四种阳离子产生的强水合I-离子的比例进行定性比较。K+对SO42-的相对亲和力最大。因此，用该阳离子进行的实验导致最大比例的I-水化程度更高，并表现出最强的非加性行为。相比之下，Cs+对SO42-的相对亲和性最弱，导致非加性最不明显。这项工作表明，当存在弱和强水合阴离子时，反阳离子的身份在盐混合物的非加性行为中起着关键作用。
The cloud point temperature of poly(N-isopropylacrylamide) was measured in aqueous solutions containing salt mixtures. Solutions were made with SO42-, a strongly hydrated anion, I-, a weakly hydrated anion, or both anions together with a common alkali metal counterion: Li+, Na+, K+ or Cs+. Nonadditive behavior was observed when the MI concentration was increased in the presence of 0.2 mol.L-1 M2SO4. Although complex changes in the cloud point temperature were observed with all four metal counter cations, the magnitude of the effects differed substantially amongst them. More specifically, SO42- was able to attract cations away from I- in each case, but its propensity to do so depended on the relative strength of the cation-iodide versus the cation-sulfate interactions. When the counterion was stripped away from it, I- became more hydrated and acted more like a strongly hydrated anion. A competitive binding model was employed to determine the fraction of cations bound to SO42- in the presence of I-, allowing for a qualitative comparison of the fraction of strongly hydrated I- ions that was produced with all four cations. K+ showed the greatest relative affinity for SO42-. As such, experiments performed with this cation led to the greatest fraction of I- that was more hydrated and displayed the strongest nonadditive behavior. By contrast, Cs+ showed the weakest relative affinity for SO42-, resulting in the least pronounced nonadditivity. This work demonstrates that the identity of the counter cation plays a critical role in the nonadditive behavior of salt mixtures when both weakly and strongly hydrated anions are present.[GRAPHICS].