Seawater pretreatment with an NF-like forward osmotic membrane: Membrane preparation, characterization and performance comparison with RO-like membranes

Abstract

A nanofiltration-like (NF-like) forward osmosis (FO) membrane was prepared by interfacial polymerization and applied for seawater pretreatment. The prepared NF-like FO membrane shows much higher water permeability and higher divalent salt to monovalent salt selectivity compared to a commercial reverse-osmotic-like (RO-like) FO membrane. The comparison between NF-like FO membrane and RO-like FO membrane in FO process was systematically investigated by using an antiscalent (sodium polyacrylate, PAANa) solution as draw solution. Both NF-like and RO-like FO process showed high rejection of alginate and sulfate. However, the water flux and monovalent salt (NaCl) passage in NF-like FO process were much higher, which enables the NF-like FO membrane to be a better candidate for pretreating seawater. The findings provide new insights on the design and preparation of FO membranes for seawater pretreatment.