Measurement of Setschenow constants for six hydrophobic compounds in simulated brines and use in predictive modeling for oil and gas systems

Abstract

Treatment and reuse of brines, produced from energy extraction activities, requires aqueous solubility data for organic compounds in saline solutions. The presence of salts decreases the aqueous solubility of organic compounds (i.e. salting-out effect) and can be modeled using the Setschenow Equation, the validity of which has not been assessed in high salt concentrations. In this study, we used solid-phase microextraction to determine Setschenow constants for selected organic compounds in aqueous solutions up to 2-5 M NaCl, 1.5-2 M CaCl2, and in Na-Ca binary electrolyte solutions to assess additivity of the constants. These compounds exhibited log-linear behavior up to these high NaCl concentrations. Log-linear decreases in solubility with increasing salt concentration were observed up to 1.5-2 M CaCl2 for all compounds, and added to a sparse database of CaCl2 Setschenow constants. Setschenow constants were additive in binary electrolyte mixtures. New models to predict CaCl2 and KCl Setschenow constants from NaCl Setschenow constants were developed, which successfully predicted the solubility of the compounds measured in this study. Overall, data show that the Setschenow Equation is valid for a wide range of salinity conditions typically found in energy-related technologies.

Effect of Sodium Sulfate, Ammonium Chloride, Ammonium Nitrate, and Salt Mixtures on Aqueous Phase Partitioning of Organic Compounds

“…Such correlations had previously been observed between NaCl and (NH 4 ) 2 SO 4 , 5 between NaCl and KCl, and between NaCl and CaCl 2 . 15 The observations that the salt effect follows a specific order and K S for different salts are significantly correlated suggests that the identity of the salts determines the order of the salt effect (ion−water interaction), while the identity of the organic solutes determines its specific value (organic−water or organic−ion interaction). The K S for a specific compound is largely determined by the salt species' properties.…”

“…Little is known about the salt effect in salt mixtures, even though salts are usually present as mixtures. To the best of our knowledge, the salt effect for salt mixtures has been reported only for naphthalene at moderate ionic strengths in binary mixtures of NaCl with MgCl 2 , Na 2 SO 4 , CaCl 2 , KBr, and CsBr, for fluorene and thiophene in Na–Ca brines, and for glyoxal in (NH 4 ) 2 SO 4 and NH 4 NO 3 mixtures . With respect to whether the effect of multiple salts in a mixed solution is additive, contradictory results have been found.…”

“…Poulson et al hypothesized that toluene’s dipole moment might allow for additional interactions in mixed electrolyte systems that could cause the nonadditive effect. However, the presence of a dipole moment in thiophene had no effect on the additivity of NaCl and CaCl 2 Setschenow constants . Clearly, the literature on this issue is inconsistent, and no general conclusion can be drawn from the small number of studies that vary in terms of scope, quality, and the treatment of uncertainty.…”

“…However, the presence of a dipole moment in thiophene had no effect on the additivity of NaCl and CaCl 2 Setschenow constants. 15 Clearly, the literature on this issue is inconsistent, and no general conclusion can be drawn from the small number of studies that vary in terms of scope, quality, and the treatment of uncertainty. Findings are generally qualified or their validity is limited to the specific salts and organic compounds being studied.…”

Morphologies Observed in Ultraflexible Microemulsions with and without the Presence of a Strong Acid

“…We use as model system octan-1-ol/ethanol/water mixtures, since thermodynamic data as well as the solubility of many added solutes are available. − We want to extend the previous analysis to regions all around the phase transition border, using a comparative experimental and theoretical approach. To do this, small and wide-angle X-ray scattering experiments (SWAXS) have been performed to reveal the structuring of the yet uninvestigated part of the phase diagram.…”