Amicon ultrafiltration cell

Membranes cast with 10 wt% PVDF-g-EGMP were cut into 45 mm diameter coupons and placed in a Amicon ultrafiltration cell (EMD Millipore, Burlington, MA, USA). Two ²³⁸Pu solutions were prepared for the study: a spiked DI water solution with an activity of 0.48 ± 0.01 Bq/mL and pH 6.61, and a synthetic seawater solution with an activity of 0.51 ± 0.01 Bq/mL and pH 6.58. Filtration and alpha spectrometry procedures were the same for DI water and synthetic seawater trials. The Amicon flow cell was filled with 10 mL of the prepared ²³⁸Pu solution. The cell was sealed and pressurized to 0.69 barg using a dry air cylinder to start filtration. Once all of the ²³⁸Pu solution was filtered, the cell was refilled with 10 mL DI water and pressurized to 0.69 barg to perform a wash cycle to remove Pu from the membrane pores. The membrane was removed once the cell was completely empty of its contents and depressurized. Membrane samples were dried for at least 1 h before alpha spectrometry measurements. Alpha spectrometry was performed by mounting the membranes in a custom acrylic holder placed 5 mm from the detector face, followed by counting for 5 h.

SN_TAE2020 was concentrated 10-fold with Amicon Ultrafiltration cell equipped with a 30 kDa cut-off PES Millipore Ultrafiltration Disc (Merck KGaA, Darmstadt, Germany). Then, retentate fraction (SNC_TAE2020) and permeate fraction (P_TAE2020) were collected.

The cell-free supernatant (SN TAE6080) was concentrated 10-fold with Amicon Ultrafiltration cell equipped with a 30 kDa cut-off PES Millipore Ultrafiltration Disc (Merck KGaA, Darmstadt, Germany). Then, retentate fraction (SNC) was collected.