Boron mass transfer during seeded microfiltration.

Seeded microfiltration combines the processes of microfiltration and sorption of a solute onto a solid particle, including ion exchange. The process can be performed for investigations in simple stirred cells, for laboratory mass transfer analysis, and for process-scale applications in crossflow filtration systems. Seeded microfiltration of boron at feed concentrations of up to 4 ppm using a N-glucamine type ion exchange resin showed that the process was dependent on the internal diffusion of boron inside the resin particle, with an effective particle diffusivity of 5.5 x 10−10m2 s−1. The kinetics of the process were modelled by a coupled mass transfer model, based on a well mixed stirred system, aqueous film diffusion, particle diffusion and a Langmuir type isotherm for the equilibrium conditions. The modelling suggests that a resin particle diameter of 50μm would provide improved boron extraction performance, whilst easily being retained within the microfiltration process. A comparison of the analysis of mass transfer between a conventional batch stirred cell and the continuously fed seeded microfiltration system shows that the continuously fed system has many advantages for the laboratory investigation of mass transfer parameters.