Liquid-solid-solution phase separation

The methods and literature are briefly reviewed for solid-suspension separations, solution-phase separations, liquid-phase separations, and gas-phase separations. In the terminology used, the objective is to separate a feed stream (or streams) into a permeate phase and a reject phase, either of which may contain the compon-ent(s) of more interest. For a single membrane, say, the permeate phase remains on the feed side or high-pressure side of the membrane, and is subsequently discharged, whereas the reject or raffinate phase builds up on the opposite or low-pressure side of the membrane, and is then discharged. 

Figure 1.9 (a) Phase separation of diblock copolymer (polystyrene-p-polyferrocenyldimethylsilane) guided by substrate strips (adapted from [39] with permission) (b) scheme of liquid-solid-solution (LSS) phase separation and transfer synthetic strategy (reproduced from [41] with permission). 

In 2005, Li et al developed a general liquid-solid-solution (LSS) strategy for the controlled synthesis of various nanocrystals, including lanthanide-doped UCNPs. In the LSS strategy, oleic acid also acts as a stabihzing agent. Reactants exist in different phases, and reactions occur oifly at the interfaces. This phase separation and transfer mechanism enables a controllable synthesis of monodisperse nanocrystals. Li et further extended this LSS strategy to produce... 

In Section 3.3.7.S, the equilibrium partitioning of a species between a liquid phase and a solid phase was briefly considered for three types of liquid-solid equilibria. The separation between two species i and j for such liquid-solid two-phase systems is briefly considered here. There are systems where three phases can be present for example, two immiscible solid phases and a saturated solution, as in the case of solid salt, ice and a saturated salt solution. Figure 4.1.10 shows a temperature vs. composition phase diagram where solid phase 1 coexists with solid phase 2 and a saturated liquid solution at the eutectic point E. Below the eutectic temperature T, immiscible pure solid phase 1 and 2 are present together. For these and more complex systems, the reader should refer to appropriate texts (Darken and Gurry, 1953 DeHoff, 1993). Separation between species i and j in simpler two-phase systems described in Figures 3.3.6A, where the solid phase is a homogeneous solution, will be determined now. 

The ions in an electrolyte solution can arise in two major ways. They may already be present in the pure compound, as in ionic solids. When such a solid is placed in water, the ions separate and move throughout the solution. However, some compounds that form ions in water are not considered to contain ions when pure, whether in the solid, liquid, or gas phase. Hydrochloric acid, HQ, and sulfuric acid, H2S04, are good examples of the second type of compound. They form molecular liquids (or solids, if cold enough). But in water they form ions HC1 gives hydrogen ion, H+(aq), and chloride ion, G (aq) H2SO ... 

The vast majority of modem liquid chromatography systems involve the use of silica gel or a derivative of silica gel, such as a bonded phase, as a stationary phase. Thus, it would appear that most LC separations are carried out by liquid-solid chromatography. Owing to the adsorption of solvent on the surface of both silica and bonded phases, however, the physical chemical characteristics of the separation are more akin to a liquid-liquid distribution system than that of a liquid-solid system. As a consequence, although most modern stationary phases are in fact solids, solute distribution is usually treated theoretically as a liquid-liquid system. 

Strictly speaking, the term racemic mixture applies only when the mixture of molecules is present as separate solid phases, but in this book we shall use this expression to refer to any equimolar mixture of enantiomeric molecules, liquid, solid, gaseous, or in solution. 

A brief discussion of sohd-liquid phase equihbrium is presented prior to discussing specific crystalhzation methods. Figures 20-1 and 20-2 illustrate the phase diagrams for binary sohd-solution and eutectic systems, respectively. In the case of binary solid-solution systems, illustrated in Fig. 20-1, the liquid and solid phases contain equilibrium quantities of both components in a manner similar to vapor-hquid phase behavior. This type of behavior causes separation difficulties since multiple stages are required. In principle, however, high purity... 

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