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SEPARATION PROCESSES BY NON-DISPERSIVE LIQUID-LIQUID EXTRACTION. MATHEMATICAL MODELLING OF THE SEPARATION SELECTIVITY

B. Galan
Dpto. Química. Avda. los Castros s/n. 39005. Santander, Spain

A. I. Alonso
Departamento de Química, Universidad de Cantabria. Avda de Los Castros s/n. 39005 Santander, Spain

M. F. San Roman
Dpto. Química. Avda. los Castros s/n. 39005. Santander, Spain

A. Irabien
Departamento de Ingenieria Quimica y Quimica Inorganica, ETSII y T., Universidad de Cantabria, Avda. Los Castros, s/n, 39005 Santander, Espana

I. Ortiz
Dpto. de Quimica. E.T.S.I.I. y T. Universidad de Cantabria. Avda. de los Castros S/N. 39005, Santander, Spain

ABSTRACT

A mathematical model for the description of the separation selectivity of two metals in hollow fiber modules under non-steady state conditions has been developed in this work, taking as example the separation of nickel and cadmium from highly concentrated solutions. Starting with the mathematical description of the mass transport kinetics of the individual metals in the NDSX system, (eight partial differential equations, extraction and back-extraction modules; four algebraic equations, four equilibrium constants; and six total differential equations, stirred tanks) the separation selectivity of the metals working in a non-steady state requires the addition of five partial differential equations and four integral equations. Although the complexity of the resultant model is high, it is important to remark that the kinetic modelling reported in this work requires only the determination of four parameters: two equilibrium parameters and two membrane mass transport coefficients. The resolution of the equations has been carried out using a software package called gPROMS.