Software for computation of aqueous phase species distributions and solvent extraction with liquid cation exchangers
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implicitly allowing for the presence of species which do not form complexes to an appreciable extent, such as Na ÷ or CIO4 ions. The composition and overall stability constants of any number of hydroxo complexes and complexes with anionic ligands are entered. The formation of acid-ligand species such as HSO2 is taken into consideration. The aqueous phase species distributions are calculated by considering the following equilibria: a M + bOH = Ma(OH)b
[1]
/3o~ _ [M.(OH)b] [M].[OH] b
[2]
c M + dL + e H L = McLd(HL)e
[31
for which
and
for which [McLa(HL)e]
[41
~cLd,e = [MlC[LIa[HL] e
REFERENCES 1. R.M. Pytkowicz: Activity Coefficients in Electrolyte Solutions, CRC Press, Boca Raton, FL, 1979, vol. II, pp. 40-58. 2. R.A. Robinson and R. H, Stokes: Electrolyte Solutions, 2nd ed., Butterworths and Co. Ltd., London, 1959, p. 502.
for any inorganic ligand L. Charges have been omitted in the above equations for simplicity. The total amount of metal and inorganic ligand in solution is then: [Mlaq = /~M[M]
[5]
[L]tot = ~L[L]
[6]
where
Software for Computation of Aqueous Phase Species Distributions and Solvent Extraction with Liquid Cation Exchangers
=
t + E a/:3°,~ [M]~-I[OH] b + a,b
E cB~,a,~ [MI~-I[L]a+e[H]eK;
[7]
c,d,e
and D. POUILLON and F.M. DOYLE
/3L = 1 + Kb[H] + ~'~ (d + e)/3c.a.elM] r c[L]d+e-I [H] Kb e
There are numerous circumstances in the chemical processing of materials where it is necessary to know the distribution of species in aqueous solutions, or to predict the partition of a component between immiscible phases. We encountered this need when developing a model to predict the solvent extraction behavior of liquid cation exchangers. Accordingly, we have developed interactive programs for calculating aqueous phase species distributions and solvent extraction behavior. These programs, which are written in Professional Fortran to run on an IBM PC/XT, along with the source codes, are available to any interested parties from the senior author. The program SPECIES calculates aqueous phase species distributions as a function of pH. The user is requested to specify the cation which forms complexes, and the anionic ligand of the system. The concentrations of cation and anion are specified independently and need not be equivalent, thus D. POUILLON, formerly Graduate Student in the Department of Materials Science and Mineral Engineering, University of Califomia, Berkeley, is with the Belgian Army. F.M. DOYLE is Assistant Professor, Department of Materials Science and Mineral Engineering, Umversity of California, Berkeley, CA 94720. Manuscript submitted May t, 1987. METALLURGICALTRANSACTIONS B
e
c,d,e
[8] (Kb is the equilibrium constant for the reaction H + L = HL).
For each pH value considered, SPECIES solves these equations for M and L, the concentrations of free cation and anionic ligand, in an iterative fashion, then uses these values to calculate the concentrations of the individual species in solution. The flowchart for these operations is given in Figure 1. The output is directed simul
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