Osmotic coefficient data for NaOH–NaCl–NaAl(OH) 4–H 2O system measured by an isopiestic method and modeled using Pitzer's model at 298.15 K

Abstract

Osmotic coefficient data were obtained for the aqueous solutions of NaOH–NaCl–NaAl(OH) 4. The solutions were prepared by dissolving AlCl 3·6H 2O in aqueous NaOH solutions. The osmotic coefficients of the solutions were measured by an isopiestic method at 25°C. The osmotic coefficient data were used to evaluate the unknown binary and mixing parameters of Pitzer's model for the aqueous NaOH–NaCl–NaAl(OH) 4–H 2O system. The binary Pitzer's parameters, β (0), β (1), and C φ , for NaAl(OH) 4 were found to be −0.0083, 0.0710, and 0.00184 respectively. These binary parameters were obtained from the data on the ternary system. This was necessary since it was not possible to prepare a single (NaAl(OH) 4) solution. The mixing parameters, Θ OH −Al(OH) − 4 , Θ Cl −Al(OH) − 4 , Ψ Na +OH −Al(OH) − 4 , and Ψ Na +Cl −Al(OH) − 4 were found to be −0.2255, −0.2430, −0.0388, and 0.2377 respectively. The experimental osmotic coefficient data were correlated well with Pitzer's model using the parameters obtained.