Efficacy of Electrically-Polarized 3D Printed Graphene-blended Spacers on the Flux Enhancement and Scaling Resistance of Water Filtration Membranes

Abstract

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 nonpolarized graphene-polylactic acid (GRP) spacer and a polylactic acid (PLA) spacer. The use of the developed E-GRP as a draw spacer showed >50% water flux enhancement (32.4 +/- 2 Liter/m(2)/h (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 local osmotic pressure across the membrane surface due to the ions adsorbed by the polarized (E-GRP) spacer. As a feed spacer, the E-GRP 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).