Construction of 1D akaganeite-templated nanochannels in polyamide forward osmosis membrane for high flux separation and nutrient enrichment

To realize nutrient (NO3–-N and PO43−-P) enrichment through FO, this study focuses on tailoring polysulfone (PSF) support layer of TFC FO membrane using 1D akaganeite (Ak) as nano-template to improve the permeance and selective separation of nutrient ions. The incorporation and the subsequent removal of the nano-template from the PSF support layer instantly created porous structures with the desired nanochannel architectures. The separation performance of the resultant e-Ak/TFC membrane is superior to other as-synthesized TFC membranes due to the presence of highly permeable channels, lower membrane tortuosity of support layer and the formation of homogenous polyamide active layer. This restricts the back-diffusion of ions in the support layer, hence improving the effective driving force across the layer. The membrane demonstrated increased water flux from 6.5 for control TFC to 14.1 L/m2∙h for e-Ak/TFC membrane (∼2.2 times higher) along with high selectivity, JW/JS of 0.58 g/L and lower S value. NO3–-N and PO43−-P were effectively enriched in the feed side due to high ion removal efficiencies by the membrane (>97 %) with water reduction of approximately 25 %. We anticipate this work offers an insight into the design of FO membrane that is capable for desalination and enrichment of nutrient in wastewater.