Development and evaluation of a novel feed spacer for forward osmosis membrane

Abstract

This paper introduces new feed spacer geometry for the forward osmosis (FO) membrane modules in an attempt to achieve more water flux than conventional models. The geometry is based on a mesh with star-shaped cross-section filaments, and it is optimized by using the response surface methodology (RSM) with a central composite design (CCD) in a series of numerical simulations. Filament thickness, filaments distance, and curvature radius are evaluated as main geometry parameters, while pressure drop and water flux are observed as responses. Two models are extracted with R2 of more than 99%. Results show the filament thickness and distance have a highly significant effect on responses. Simultaneous optimization of water flux and pressure drop predict the best results would be obtained with a filament thickness of 0.4 mm, a filament distance of 2.32 mm, and a curvature radius ratio of 0.7 with a desirability of 0.66. The vertical movement of filaments in the channel, zigzag, and uniform mode, negatively affect the spacer performance. The results of the newly developed spacer were compared with those of a commercial spacer with 31 mil thickness. The optimized spacer achieved 8% more water flux than the commercial 31-mil spacer in the proposed conditions. This research shows that the newly developed FO spacers could improve the performance of this process.