selective liquid-liquid phase transfer

该提案的目标是在液-液界面对亚微米粒子（< 500 nm）进行多维分离。分选的多维方面是指(1)物料分选和(2)粒度分选。材料特异性分离是通过目标颗粒的选择性疏水性来实现的。这种疏水性依赖于离子表面活性剂的静电驱动吸附，这将通过使用可水解的金属阳离子作为表面和表面活性剂之间的连接剂来辅助。这种吸附途径具有物质特异性的优点，即它创建了一个分离标准，并且是可逆的。特别是后一点是非常重要的，因为粒子的疏水性可以通过水相中ph值的变化来具体解决。颗粒在液-液界面中的稳定性主要取决于颗粒的大小。在给定的润湿角和界面张力下，大颗粒比小颗粒更有效地捕获在界面中。对于足够小的粒子，我们可以期待一个完全的相转移。这种转移发生的确切尺寸将取决于界面张力和润湿角。后两个量受表面活性剂的种类和浓度以及盐浓度的影响，这为调节分离提供了一种手段。多维分离的一般思路是使用定义明确的皮克林乳剂作为分离工具。连续相将是具有特定化学成分（pH、可水解盐、离子表面活性剂）的水悬浮液（SiO2、Al2O3和/或TiO2，尺寸范围在20-500 nm）。这是为了实现目标颗粒的选择性疏水作用。颗粒要转移到的油相是长链正构烷烃。一旦水相和油相发生乳化，预计小的目标颗粒将转移到油相中，较大的颗粒将被困在水-油界面中。剩余相的所有颗粒将留在水相中。完成分离的关键步骤是控制较大颗粒从界面上的释放。这将通过冷冻乳液的油相来实现。这一步骤将使小颗粒留在凝固的油滴内部，而大颗粒仍与水相接触。为了将这些颗粒转移回水相，我们将研究几种策略：油滴的表面熔化，以及为了利用疏水作用的可逆性而调整水化学的组合。针对不同的化学分离参数，用多维分离函数对整个过程进行量化。

The goal of the proposal is the multidimensional separation of submicron particles (< 500 nm) at liquid-liquid interfaces. The multidimensional aspect of the separation refers to (1) material-specific separation and (2) size-specific separation.The material-specific separation is achieved by selective hydrophobization of the target particles. This hydrophobization relies on the electrostatically driven adsorption of ionic surfactants, which will be assisted by the use of hydrolysable metal cations that act as linkers between the surfaces and the surfactant. This adsorption route has the advantage of being material specific, i. e. it creates a separation criterion, and it is reversible. Especially the latter point is of great importance, since the hydrophobicity of the particles can be addressed specifically by pH-changes in the aqueous phase. The stability of particles in liquid-liquid interfaces depends critically on the particle size. For a given wetting angle and interface tension, large particles are trapped more effectively in interfaces than small ones. For small enough particles one can expect that a complete phase transfer. The exact size at which this transfer occurs will depend on the interface tension and the wetting angle. The latter two quantities are influenced by the type and concentration of the surfactant as well as by the salt concentration, which offers a means to regulate the separation.The general idea for the multidimensional separation is to use a well-defined Pickering emulsion as a separation tool. The continuous phase will be an aqueous suspension (SiO2, Al2O3 and/or TiO2 in the size range of 20-500 nm) of defined chemical composition (pH, hydrolysable salt, ionic surfactant). This serves the purpose of achieving the selective hydrophobization of the target particles. The oil phase into which the particles are to be transferred will be a long-chained n-alkane. Once the aqueous and oily phase are emulsified, it is expected that small target particles will be transferred into the oily phase and larger particles are trapped in the aqueous-oil interface. All particles of the remaining phase(s) will remain in the aqueous phase. The essential step to finalize the separation is a controlled release of larger particles from the interface. This will be achieved by freezing the oily phase of the emulsion. This step will keep the small particles within the interior of the solidified oil drops while the larger particles remain in contact with the aqueous phase. Several strategies will be examined in order to transfer these particles back into the aqueous phase: Surface melting of the oil drops and a combination involving an adjustment of the aqueous chemistry in order to exploit the reversibility of the hydrophobization. The entire process will be quantified with multidimensional separation functions for different chemical separation parameters.