  In this research, an electrically-polarized graphene-polylactic acid (E-GRP)
spacer is introduced for the first time by a novel fabrication method, which
consists of 3D printing followed by electrical polarization under a high
voltage electric field (1.5 kV/cm). The fabricated E-GRP was tested in an
osmotic-driven process (forward osmosis system) to evaluate its performance in
terms of water flux, reverse solute flux, and ion attraction compared to a 3D
printed non-polarized graphene-polylactic acid (GRP) spacer and a polylactic
acid (PLA) spacer. The use of the developed E-GRP spacer showed > 50% water
flux enhancement (32.4 +- 2 LMH) compared to the system employing the GRP (20.5
+- 2.3 LMH) or PLA (20.8 +- 2.1 LMH) spacer. This increased water flux was
attributed to the increased osmotic pressure across the membrane due to the
ions adsorbed on the polarized (E-GRP) spacer. The E-GRP spacer also retarded
the gypsum scaling on the membrane compared to the GRP spacer due to the
dispersion effect of electrostatic forces between the gypsum aggregation and
negatively charged surfaces. The electric polarization of the E-GRP spacer was
shown to be maintained for > 100 h by observing its salt adsorption properties
(in a 3 M NaCl solution).
