CHLORIDE SULFATE ION-EXCHANGE KINETICS OIL FIBROUS RESINS - 2 INDEPENDENT MODELS FOR FILM DIFFUSION CONTROL/

Fibrous ion exchangers appear to be very promising for full scale appl ications in water conditioning (demineralization, softening), wastewat er treatment for pollutant control, as well as for applications in new areas promoted by the physical structure of the materials. The kineti c performances of these exchangers appear to be faster than traditiona l bead-shaped resins. In a previous paper, the kinetic behavior of chl oride/sulfate ion exchange system on fibrous resins was investigated i n a wide range of liquid-phase concentrations (i.e., 0.006-1.8 N). The Nernst-Planck model was adopted for data correlation, and the rate-de termining step was associated with the mass transfer resistance to the interdiffusion of ions in the liquid film around the microfibers. In the present paper, the same data are revisited on the basis of an alte rnative model for film diffusion control, based on the numerical solut ion of a phenomenological equation accounting for the selectivity of t he resin toward the exchanging counterions. In this context, equilibri um studies were also carried out and criticized to get relevant data f or model implementation. Both kinetic models gave equivalent results i n experimental data correlation, thus confirming the exposed surface a rea of the fibrous exchangers, a more important factor with respect to selectivity in determining the peculiar kinetic performance of these materials.