KINETIC MODELING OF CADMIUM REMOVAL FROM PHOSPHORIC-ACID BY NONDISPERSIVE SOLVENT-EXTRACTION

In this work it is reported that the kinetic modelling of the separati on of cadmium from phosphoric acid by non-dispersive solvent extractio n. Using Cyanex 302 as selective extractant, the extraction step was c arried out in a hollow fibre module containing polypropylene fibres, w hereas the concentration step required a ceramic module with tubular c hannels due to the high acidity of the backextraction agent. Applicati on of the methodology previously reported by the authors led to the de velopment of a kinetic model with three design parameters, i.e., equil ibrium constant of the extraction reaction (ke'=6 x 10(3) mol(-2)/l(-2 )), membrane mass transport coefficient of the extraction module (K-me =8.33 x 10(-8) m/s) and of the backextraction module (K-ms=3.33 x 10-8 m/s), that described satisfactorily the behaviour of the separation-c oncentration system. Thus, in this work a new application of the non-d ispersive solvent extraction technology is presented, characterising a t the same time the behaviour and parameters of a new type of contacto r, i.e., a tubular ceramic module.