CO2诱导的水相悬浮液中介电表面的剧烈放电
CO2-induced Drastic Decharging of Dielectric Surfaces in Aqueous Suspensions
AI总结：
研究空气中CO2对水相悬浮液中聚合物胶乳颗粒表面电荷的剧烈放电影响，结合电导实验与PBC模型计算，揭示了CO2通过提高表面基团有效pKa抑制解离的机制。
摘要：
我们研究了空气中的CO2对悬浮在水相电解质中的羧酸盐稳定的聚合物胶乳颗粒电荷状态的影响。我们将基于Hessinger电导率模型解释的电导实验与采用电荷调节边界条件的Poisson-Boltzmann cell (PBC)模型计算相结合。在没有CO2的情况下，少数弱酸性表面基团发生解离，且只有部分反离子实际对电导率有贡献。剩余的反离子可以与添加的其他离子（如Na+、K+或Cs+）自由交换。从PBC计算中，我们推断出相应的pKa为4.26，以及与自由移动的反离子数量合理吻合的重整化电荷。将无盐和CO2的悬浮液与周围空气平衡后，会导致剧烈的放电，这远远超过了溶解的CO2及其解离产物的预期效应。此外，未观察到反离子交换。为了重现实验结果，我们必须假设有效pKa为6.48。CO2对表面基团解离状态的直接影响解释了我们最近关于CO2诱导ζ-电位降低的发现，并支持了由分子CO2引起额外电荷调节的假设。鉴于带电表面与水相电解质接触的重要性，我们预计我们的观察对从海水淡化到生物膜的应用具有重大的理论挑战和重要意义。
英文摘要：
We study the influence of airborne CO2 on the charge state of carboxylate stabilized polymer latex particles suspended in aqueous electrolytes. We combine conductometric experiments interpreted in terms of Hessinger's conductivity model with Poisson-Boltzmann cell (PBC) model calculations with charge regulation boundary conditions. Without CO2, a minority of the weakly acidic surface groups are dissociated and only a fraction of the total number of counter-ions actually contribute to conductivity. The remaining counter-ions exchange freely with added other ions like Na+, K+ or Cs+. From the PBC-calculations we infer a corresponding pKa of 4.26 as well as a renormalized charge in reasonably good agreement with the number of freely mobile counter-ions. Equilibration of salt- and CO2-free suspensions against ambient air leads to a drastic de-charging, which exceeds by far the expected effects of to dissolved CO2 and its dissociation products. Further, no counter-ion-exchange is observed. To reproduce the experimental findings, we have to assume an effective pKa of 6.48. This direct influence of CO2 on the state of surface group dissociation explains our recent finding of a CO2-induced decrease of the ζ-potential and supports the suggestion of an additional charge regulation caused by molecular CO2. Given the importance of charged surfaces in contact with aqueous electrolytes, we anticipate that our observations bear substantial theoretical challenges and important implications for applications ranging from desalination to bio-membranes.
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