*2.3. Membrane Preparation*

The Aquivion dispersion in water was cast on a Petri dish and dried at 80 ◦C in an oven. The resulting membrane was dissolved in propanol (1 g in 20 mL) at 80 ◦C. A weighted amount of pristine CeO2 or PDA coated CeO2 nanoparticles was added to 20 mL of the Aquivion dispersion in propanol. The mixtures were treated with ultrasounds for 10 min, stirred for 2 h, cast by an Elcometer Doctor Blade Film Applicator on a glass support and dried in an oven at 80 ◦C. After that, all membranes were treated according to the following procedure: 2 h in HCl 1 M, 1 h in H2O at room temperature, 2 h at 90 ◦C and 1 h at 160 ◦C. Composite membranes, 20–25 μm thick, containing 3% and 5% wt% of PDAx@CeO2 were prepared. The same procedure was used to prepare the neat Aquivion membrane.
