Size separation of silver nanoparticles by dead-end ultrafiltration: Description of fouling mechanism by pore blocking model

•Purification and size separation of silver nanoparticles by dead-end ultrafiltration were studied.•Residual ions were eliminated by the washing method with citrate solution.•Size-based fractionation of silver nanoparticles was performed by the washing method.•Cake formation was identified to be the main fouling mechanism.

The aim of this study was to evaluate the application of dead-end ultrafiltration for the preparation of silver nanoparticles (AgNPs) with narrow size polydispersity. Aspects as the reaction yield, purification, size-based fractionation, and fouling mechanisms were analyzed. AgNPs were synthesized by chemical reduction, and diafiltration experiments were performed by the washing method. Our results suggest that the cut-off size of the membrane can be used as a primary criterion to define the particle size in the permeate, and eliminate Ag+ from a colloidal dispersion of AgNPs by removing NPs with a size less than the exclusion limit of the membrane. In addition, it was evidenced that ultrafiltration is not an effective method for elimination of AgNPs from aqueous effluents or for exact determination of reaction yield. In the prediction of J0, the lowest error was obtained for the cake formation (7.6% and J0=1.36×10−2 m/s) followed by internal and intermediate pore blocking models with 32.5 (J0=9.91×10−3 m/s) and 29.1% (J0=1.04×10−2 m/s), respectively. Cake formation was identified to be the main fouling mechanism associated with the filtration of the AgNP colloidal dispersion.

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