COACERVATION IN AQUEOUS-SOLUTIONS OF SHORT-CHAIN TETRAALKYLAMMONIUM BROMIDE AND SODIUM-SILICATE

Coacervation (liquid/liquid separation) takes place in aqueous solutio ns containing short chain tetraalkylammonium (TAA) and silicate ions w hen other ions (Na+, Br-) are present. The TAA bromide is predominantl y present in the upper layer and the sodium silicate is mainly present in the lower layer. The coacervation can be described using the activ ity coefficients of the two separate salts and a Redlich-Kister type e xcess Gibbs free energy. Since part of the Gibbs free energy is depend ent on the enthalpy of hydrophobic hydration of the TAA ions, the driv ing force for coacervation is ascribed to a mismatch of the hydration layers around the silicate and TAA ions.