Transport of trace organic compounds through novel forward osmosis membranes: Role of membrane properties and the draw solution. (15th September 2018)

• Record Type: Journal Article
• Authors: Sauchelli, Marc; Pellegrino, Giuseppe; D'Haese, Arnout; Rodríguez-Roda, Ignasi; Gernjak, Wolfgang
• Is Part Of: Water research. Volume 141(2018)
• Page Start: 65
• Page End: 73
• Publication Date: 2018-09-15
• Subjects: Forward osmosis -- Thin-film composite membrane -- Trace organic contaminants -- Mass transport; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2018.05.003
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Forward osmosis (FO) offers to be a very promising technology for the removal of trace organic compounds (TrOCs) from contaminated wastewater, and with the recent developments in FO membranes, the effect of both a higher water flux and reverse salt flux on the rejection of TrOCs needs to be explored. In this study two novel thin-film composite (TFC) membranes with greater water permeability and selectivity than the benchmark cellulose tri-acetate (CTA) membrane were compared at bench-scale in terms of TrOCs permeability. By probing the solute-membrane interactions that dictate the transport of TrOCs through the two membranes in the absence and presence of a draw solution, several conclusions were drawn. Firstly, steric hindrance is the main TrOCs transport -limiting mechanism through TFC membranes unless the negative membrane surface charge is significant, in which case, electrostatic interactions can dominate over steric hindrance. Secondly, the increase in ionic strength induced by the draw solution in the vicinity of and perhaps inside the membrane seems to favour the rejection of TrOCs by "shrinking" the membrane pores or by "shielding" the negative surface charge. Lastly, during FO operation, solute concentration polarisation becomes detrimental when working at high water fluxes, whereas the reverse solute flux has no direct impact on the transport of TrOCs through the membrane. Graphical abstract: Image 1 Highlights: Permeability of TrOCs through two novel TFC-FO membranes differed significantly. Steric hindrance was the dominant rejection mechanism for the TFC-1 membrane. Electric repulsion and attraction governed TrOC transport through TFC-2. Partitioning of draw solute resulted in a pore size reduction for TFC-1. On TFC-2 the presence of the draw solute lead to shielding of electric effects.