AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Micro- and Ultra-filtration of Polystyrene Latex Nanoparticles through Nuclepore Filters: Experiments and Models
HANDOL LEE, Sheng-Chieh Chen, David Y. H. Pui, University of Minnesota
Abstract Number: 355 Working Group: Control Technology
Abstract Micro- and ultra-filtration are being widely applied to remove nanoparticles in drinking water and chemicals for their purifications. Up to date, the micro- and ultra-filtration filters are usually characterized by their geometric pore size. However, significant discrepancies between the prediction and experimental data are often observed especially for nanoparticles due to the complex surface interactions between filter and particle. For investigating the reason causes the discrepancy, nanoparticle retention efficiency under unfavorable conditions was carried out experimentally and theoretically simultaneously using Nuclepore filters and monodisperse standard PSL particles as model systems. In the experiments, PSL particles with 60~500 nm were used to challenge 50, 200 and 400 nm rated Nuclepore filters with different ionic strengths. The particle penetration was determined by taking the ratio of downstream particle concentration of the filter to that of upstream measured by nanoparticle tracking analysis (NTA) technique. In the theoretical modeling, capillary tube model was used to calculate the initial efficiency which latter was modified by considering the reentrainment. The former was mainly governed by the flow condition and the latter was by the DLVO surface interactions. Primary- and secondary-minimum deposition determined from the Maxwell approach were calculated to obtain the sticking coefficient, and the real deposition efficiency is then equal to the initial efficiency multiplied by the sticking coefficient. The torques analysis showed that the adhesion torque of a particle located in the primary minimum (0.3 nm) will be slightly larger than the drag torque, which resulted in the particle deposition on the pore walls. However, experimental data showed that the deposited particles on the pore wall most likely detached, indicating that particles should locate at a separation distance longer than the primary-minimum distance. By this assumption, the data are in very good agreement with model for all tested filter, particle and ionic strength conditions.