SXLSQA, A Computer Program for Including Both Complex Formation and Activity Effects in the Interpretation of Solvent Extraction Data

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Abstract
A previously reported computer program for the interpretation of solvent extraction data in systems that can include two extractants, one acidic and one neutral, has been extended to treat the effects of: (1) variation of activity coefficients of solute species and of water activity in the aqueous phase, calculated by the Pitzer treatment; (2) variation of activity coefficients of solute species in the organic phase, calculated by the Hildebrand-Scott treatment; and (3) product species formed in the aqueous phase. The interaction parameters of the Pitzer treatment and the solubility parameters of the Hildebrand-Scott treatment can be refined along with the formation constants of various assumed product species to fit the data. Like its predecessor, the program is capable of fitting simultaneously a variety of data, including the distribution of an extractable cation, anion, or water, as well as spectra, vapor pressure, or heats of mixing for the organic phase. Use of the program is illustrated by modeling the extraction of water and HNO3 from aqueous nitric acid by di(2-ethylhexyl)sulfoxide in dodecane.