Nanotech 2010

Analysis of Membrane Filtration Efficiency for the Removal of Metal Oxide Nanoparticles from Aqueous Nanoparticle Suspension

S. Surawanvijit, M. Kim, Y. Cohen
Center for Environmental Implications of Nanotechnology, US

Keywords: nanoparticle, removal, coagulation, membrane filtration, isoelectric pH

Abstract:

The introduction of nanoparticles (NPs) into aqueous environment is expected to rise with increased manufacturing and use of nanoparticles. There is a need to identify efficient and methods for NP removal and such methods must be evaluated with respect to their effectiveness. In this study, the effectiveness pH adjustment and coagulation of NPs followed by membrane filtration to remove NPs from aqueous suspension was examined for metal oxide NPs. Pretreatment of NP suspension by pH adjustment toward the isoelectric pH of the NPs combined with coagulation was found to induce aggregation of NPs to form large flocs that enabled ultrafiltration (UF). A series of optimization studies revealed that commercial coagulants, followed by sedimentation was effective in removing about 70% of the NPs from suspensions of concentrations as low as 20 ppm. Subsequent crossflow membrane ultrafiltration of the supernatant allowed 95% overall nanoparticle removal. The impact of NP flocs on membrane fouling was evaluated via monitoring filtration flux. The formation of cake layer on the membrane surface was minimized through optimization of hydrodynamic conditions and solution chemistry. And the analysis of the membrane performance was conducted by evaluating membrane permeability and cake resistance due to chemical and physical fouling.
 
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