Co-precipitation of radium in high ionic strength systems: 1. Thermodynamic properties of the Na–Ra–Cl–SO4–H2O system – Estimating Pitzer parameters for RaCl2

Co-precipitation of radium in high ionic strength systems: 2. Kinetic and ionic strength effects

“…Their extrapolated parameters for Ra 2+ -Cl À interaction, together with Paige et al's (1998) parameters for Ra 2þ -SO 2À 4 and Ra 2þ -HSO À 4 interactions, have been used in the thermodynamic calculations made in the present study. As shown by Rosenberg et al (2011), as NaCl concentration increases, the c Ra 2þ =c Ba 2þ ratio decreases, but the decrease is not substantial. Close to halite saturation, its value is $0.75.…”

“…In many natural and anthropogenic environments, NaCl is the main electrolyte, and the most significant interaction is with Cl À . Rosenberg et al (2011) have discussed the difficulties that radioactive safety issues pose for the experiments required to evaluate the RaCl 2 parameters. It is common to assume that the Pitzer parameters of similar ions, in this case those of Ra 2+ and Ba 2+ , are identical.…”

“…This assumption will yield equal activity coefficients for both ions in any given solution (i.e., c Ra 2þ =c Ba 2þ ¼ 1). One alternative to this procedure has been presented by Rosenberg et al (2011), who extrapolated the RaCl 2 parameters (b (0) Ra-Cl , b (1)…”

“…(5), (6), and (3). While this approximation may be valid for relatively dilute solutions, it may not be the case for high ionic strength solutions (Langmuir and Riese, 1985;Rosenberg et al, 2011).…”

Estimation of the Pitzer Parameters for 1–1, 2–1, 3–1, 4–1, and 2–2 Single Electrolytes at 25 °C

“…In fact, this is an important drawback of the Pitzer model since in many cases the experiments required to obtain the parameters in the Pitzer equations are very difficult to perform, e.g. experiments involving radioactive species 3 . Therefore, finding a way to correlate the virial terms in the Pitzer equation with the properties of the solution is highly important.…”