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Self-generated fluid pumping can be achieved with nanostructured Nafion polymer films using different cations as fuel in a wide range of salt concentrations (10-6M-10-2M). It turns out that such Nafion pumps efficiently capture divalent metal cations such as Cd2+, present in contaminated water samples, using the own capture of this ion as fuel to drive fluid pumping. The removal efficiency is >95% in Na+ concentrations typically found in drinking water (23 mg/L). Thus, this system has potential for effective and fast water purification strategies for environmental remediation 1. Here, we have characterized Nafion thin films (≈ 300 nm thick) spin-coated on newly designed 15 nm thick, 60 um × 700 um Si3N4 membranes with HAXPES at the GALAXIES beamline in SOLEIL using recently developed environmental liquid cells (see right insets in Fig. 1) [2]. The Nafion films were soaked in Cd2+ and Pb2+ salts (10-3 M). Figure 1 shows HAXPES spectra acquired with 6.1 keV photons of the F, O and N1s region across the Si3N4 membrane with the beam on (blue) and out (red) of the membrane, evidencing the presence of the Cd3p lines which implies that Cd2+ is efficiently absorbed by the Nafion film. Special care has been taken to mitigate beam damage artifacts, which are particularly detrimental for Nafion, after a systematic characterization. Future experiments using tested circulating liquid cells are foreseen [2].
1 Esplandiu, M.J., Reguera, D., Romero-Guzmán, D. et al. Nat Commun 13, 2812 (2022). https://doi.org/10.1038/s41467-022-30554-7
[2] F. Capone, O. Muntada, J. C. Ramírez, M. J. Esplandiu, R. Dedryvère, A. Grimaud, B. Lassalle-Kaiser, D. Céolin, F. Pérez-Murano, J.-P. Rueff, J. Fraxedas, J. Synchrotron Rad. 31, 1505-1513 (2024); https://doi.org/10.1107/S1600577524008865