On the modelling of multicomponent acid extraction with long-chain aliphatic amines

The solvent extraction of phosphoric, hydrochloric, sulphuric, hydrofluosilicic and hydrofluoric acids with long-chain aliphatic amins is modelled. Pure acid equilibria are based on existing isotherms or calculated extraction constants when only experimental data are available. For binary mixtures binary combinations of acid complexes are added. In the aqueous phase Bromley's model for electrolytes is used for calculation of ionic activity coefficients and the appropriate association/dissociation equilibria taken into account for calculation of ionic strength. For the organic phase an empirical model for the non-ideal behaviour of phosphoric acid is used. For multicomponent mixtures at low acid concentrations the model calculates the extraction of phosphoric, hydrochloric and sulphuric acid almost quantitatively. For hydrofluosilicic and hydrofluoric acid the calculations are less precise and further information is needed about the different fluoride exchange equilibria involved

Solvent extraction of hydrofluosilicic acid with alamine 336

Extraction constants for the solvent extraction of hydrofluosilicic acid with Alamine 336 have been determined. Two species were identified, (R3NH+ )2 SiF62- and R3NH+ HSiF6, whose respective extraction constants were determined to be log K21 = 7.42 and log K11 = 2.60. For the dissociation of hydrofluosilicic acid the activity coefficient model presented by Bromley was adapted to sulphuric acid and the values used for hydrofluosilicic acid. The effect of the diluent was experimentally investigated

Solvent Extraction of Phosphoric Acid with Long Chain Tertiary Amines

Solvent extraction of phosphoric acid with Alamine 336 and tri-n-octylamine in toluene has been investigated. The activity of phosphoric acid is expressed as a polynomial of ionic strength and Bromley's model for electrolyte solutions is employed for calculation of ionic activity coefficients. Three species R3N (H3P04) n with n = 1, 2 and 3 in the organic phase are taken into account for explanation of the distribution equilibria. The extraction constants have been determined as log K11 = 2.05, log K12 = 3.61 and log K13 = 3.84 respectively. Aggregation and other non-ideal behaviour in the organic phase are described by letting the corresponding activity coefficient quotients be a function of the total concentration of acid in the organic phase