Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

It was found that the tetra alkyl ammonium halides can solute-out the water soluble polymers and solute out by electrolyte in aqueous solutions and form the aqueous biphasic systems (ABS). To investigate these new kinds of ABS, vapor - liquid equilibria (VLE), vapor - liquid - liquid equilibria (VLLE) and liquid - liquid equilibria (LLE) measurements were carried out for ternary systems containing tetra alkyl ammonium bromides (TAAB): tetra methyl ammonium bromide (TMAB), tetra ethyl ammonium bromide (TEAB), tetra propyl ammonium bromide (TPAB) and tetra butyl ammonium bromide (TBAB); electrolytes: NaCl, NaNO3, Na2CO3 and Na3Cit; and polymers: polypropylene glycol400 (PPG400) and polyethylene glycol400 (PEG400) at different temperatures. It was found that in these systems the solutingout effect and then the tendency to ABS formation increases by increasing the difference between the hydrophilicity of two components. In the case of TAAB + polymer aqueous systems, the polymer is solute out by the more hydrophilic component TAAB and therefore ABS are formed for aqueous solutions containing PPG (which is more hydrophobic than PEG) and TMAB/TEMB (which are more hydrophilic than TPAB and TBAB). In these types of ABS, the soluting-out effects increase with an increase in temperature. On the other hand, in the case of TAAB p salt aqueous systems, the TAAB is solute out by salt which is the more hydrophilic than TAAB and therefore aqueous solutions containing (TBAB p NaNO3, Na2CO3 and Na3Cit), (TPAB and TEAB p Na2CO3 and Na3Cit) and (TMAB p Na2CO3) are undergoing phase separation and their soluting-out effects increase with decreasing temperature. The isopiestic measurements of the investigated systems show that the constant water activity lines of aqueous PPG + TAAB systems show the positive and the negative deviation from the semi-ideal behavior respectively in biphasic and monophasic area, but those of aqueous salt + TAAB systems show the negative deviation in both biphasic and monophasic area. However, the constant water activity lines of the systems with soluting-in effect, show the positive deviation from the semi-ideal behavior.