Thin film composite (TFC) membranes promote the use of forward osmosis (FO) in seawater desalination and wastewater treatment. However, bidirectional mass transport phenomena in this process still hinder its wider application. A deeper understanding of ion transport mechanism for TFC membranes is crucial for the fabrication of FO membrane. In this work, we performed numerous experiments to investigate the influences of solution chemistry on ion mass transport in TFC FO membranes. Due to the negative charge of polyamide layer, the mass transports of cations were much larger than those of anions in FO processes, and monovalent cations with smaller hydrated radius could induce greater cation exchanges than divalent cations. Though anions did not participate in the cation exchange processes directly, cations paired with nitrate could transport through the membrane more readily than those paired with chloride or sulfate. Additionally, experiments with varying solution concentrations confirmed that there is an existence of cation transport bottleneck for FO membranes. We found that the cation transport capacity was largely determined by the concentration of feed solution. Similar results were also observed in FO membranes operating in pressure retarded osmosis mode.

Critical effect of solute species and concentrations on cation exchange behavior of thin-film composite membranes in forward osmosis

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.