(302a) Experimental and Theoretical Investigation of Rejection Coefficients of Nanoparticles in Porous Membranes

Nanoparticles (NPs) are often detected in wastewater effluents due to their extensive usage in the consumer product, pharmaceutical and NPs manufacturing industries. The particles require unique membrane separation systems due to their size, shape and surface charges.

In the present work, a series of experiments were designed to steady the rejection of gold NPs.  Spherical and capsule shaped gold-particles were synthesized and functionalized using organic compounds to yield negative charges on the particle surface. These gold-particle dispersions were filtered through polycarbonate track-etch membranes with pore size ranging from 0.015 to 0.8 micron. In addition, a computational model was developed to predict the combined effect of steric, hydrodynamic and electrostatic interactions on the rejection coefficient of NPs in a porous membrane. The non-linear Poisson-Boltzmann equation was used to determine the electrostatic particle-wall interaction energy, and a fluid dynamic model that includes particle shape was developed to determine the hydrodynamic interactions. These were then incorporated into a membrane rejection model.

Rejection coefficients from experiments and theoretical modeling for both spherical and capsule particles with an aspect ratio (length/diameter) = 2 and relative particle diameters (particle diameter/ pore diameter) ranging from 0.1 to 0.8 will be presented. When particle and pore have the same charge, theoretical results predict that the rejection coefficient exceeds that of an uncharged system due to the stronger exclusion resulting from the electrostatic repulsive interactions between the particle and the pore. Model results also revealed that 99.99% particle rejection is predicted for a membrane with pore size 1.66 times larger than the particle diameter.Theoretical predictions and experimental results will be compared in this presentation.