Aqueous phase composition

Hydration gives rise to effects on pore filling and the consequent enhancement of mechanical performance (low-porosity pastes are stronger than high-porosity ones). The first fast hydration step is followed by a relatively dormant period that may last 6 months or more, depending on temperature, particle size, and aqueous phase composition. In order to control the hydration step, alkyl sulfonate salts surface-active substances (SAS) are used. 

In short, the use of average bulk aqueous-phase composition to assess the importance of various oxidation pathways can lead to erroneous results if the composition of drops varies significantly with particle size. 

In most bioseparations, a waste stream will be generated which has no commercial value. Depending on the nature of this waste stream, it may not be possible to dispose of the material easily without further processing. For example, solvent-rich mother filtrates in antibiotics production are usually distilled to separate the solvent and aqueous phases so that the aqueous phase composition is acceptable for discharge to the sewer and the solvent phase can be reused or incinerated as a smaller volume of material. 

Local equilibrium is assumed at the membrane-water interface. Thus, ai values at both the feed surface ( ai,i) and the sweep surface ( ai,ii) can be computed using the computed average selectivity coefficient value in Step 1 and the known aqueous phase compositions from Step 2. Since Tai> 9 ai,i> 9 Ai,m and the membrane thickness L are known, the interdiffusion coefficient 5ai,h can be calculated. Note that 5ai,h is not constant and it changes with time with the change in membrane composition. 

In the case of Ni, the situation is even more complex since the stoichiometric equations reported in the literature differ widely depending on the diluents used, on the aqueous phase compositions, or on the extractant concentrations employed. A discrimination procedure of the equilibrium models corresponding to the back-extraction reactions has been reported previously by taking into account the expressions given in Table 37.1 and obtaining the best results with the following equation [59] ... 

In this analysis we have also included the effect of the aqueous phase composition (pH, sugars, ethanol, hydrocolloids, salts, etc.) and the processing conditions (temperature). By incorporating solutes in the aqueous phase, we hope to approach the behavior of a simple well-defined model of complex, real food formulations. 

Equilibrium spreading pressures (iTe) of proteins and LMWE at the air-water interface as a function of pH and temperature were also studied (Patino and Martin, 1994 Nino et al., 2001,2005). The equilibrium spreading pressure is a measure of the surface activity of spread films at equilibrium. The magnitude of He was dependent on the emulsifier and on the aqueous phase composition. Eor example, the minimum for 7 and 11S soy globulin fractions at pH 5 as compared with Tig on aqueous solutions at pH different to pi can be explained by the fact that the protein is more difficult to convert into a monolayer at its isoelectric point. This behavior is not observed for globular milk proteins (like WPl). 

To analyze the effect of emulsifier concentration and aqueous phase composition on the kinetics of diffusion (fcdifr)/ the evolution of the slope of tt vs. 9 or E vs. 9 is of great utility (Nino et al., 2003). We have observed that fcdiff increases with the emulsifier concentration in the bulk phase according to the Ward and Tordai equation. The presence of sucrose in the aqueous phase increases the diffusion of proteins towards the interface. However, is lower in ethanol aqueous solutions than in water. In addition, decreases with increasing ethanol or at higher sucrose concentrations in the aqueous phase (Nino et al., 2003). 

In summary, tensiometry and surface rheology give complementary information about emulsifier adsorption and interactions at fluid interfaces as a function of emulsifier concentration, aqueous phase composition, and the scale of adsorption time. 

The structural characteristics of the monolayer also depend on the aqueous phase composition. The results suggest that there was an increase in the lipid-subphase interactions when ethanol was added to the aqueous phase. Ethanol molecules tend to be located at the interface between lipid molecules. Thus (i) van der Waals interactions are possible, which explain the monolayer condensation observed from the isotherms and (ii) in addition, dipole-dipole interaction with the polar group produces mono-layer instability by dissolution into the bulk phase. 

Nino, Ma.R.R. and Ratino, J.M.R. Effect of the aqueous phase composition on the adsorption of bovine serum albumin to the air-water interface, Ind. Eng. Chem. Res., 41,1489, 2002. 

Joubran, R.F., Cornell, D.G. and Parris, N. (1993) Microemulsions of triglyceride and non-ionic surfactant-effect of temperature and aqueous phase composition. Colloid Surf. A, 80, 153— 157. 

The efficiency and selectivity of metal salt extraction by ABC extractants and their dependence on extractant composition, aqueous phase composition, pH, and temperature have been reviewed and analyzed [30,31]. 

Equilibrium aqueous phase composition (%) Equilibrium [HsPO/iltora) (mM) Selectivity H2SO4/ H3PO4 ... 

Table 11 Effects of Aqueous Phase Composition on H2SiFa Extraction and on F/PO4 Selectivity ...

Supported liquid membrane extraction (SLME) is emerging as a fast and efficient sample preparation technique. Aromatic aminophosphonate isolation from water samples based on SLME allowed the identification and study of the operational parameters (pEI and ionic strength of the aqueous phase, composition of the membrane phase, and concentration of analytes) as well as the structure-extraction efficiency relationship. 

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