Analysis of Membrane Filtration Efficiency for the Removal of Metal Oxide Nanoparticles from Aqueous Nanoparticle Suspension with Feed Coagulation Pretreatment

摘要

Discharge of engineered nanoparticles (eNPs) into aquatic systems is expected to increase with the accelerated manufacturing and use of eNPs. Therefore, it is necessary to identify and evaluate efficient methods for eNPs removal from aqueous system. In this study, the effectiveness of pH adjustment and coagulation of nanoparticles to enable sedimentation in addition to removal by membrane filtration (e.g., ultrafiltration) was examined for TiO_2, ZnO, and CeO_2 nanoparticles. A series of optimization studies revealed that pretreatment of eNP suspensions by pH adjustment toward the isoelectric pH of the eNPs combined with coagulation using typical coagulants (e.g., ACH, FeCl_3, and polyDADMAC), followed by sedimentation was effective in removing a significant fraction (up to 70%) of the eNPs from suspensions of concentrations as low as 20 ppm. Subsequent ultrafiltration of the supernatant allowed nearly complete overall eNP removal.