Desalination of Brackish Water Using Nanofiltration: Performance Comparison of Different Membranes

Characterization and performance screening of NF membranes are essential to evaluate their suitability for application in brackish water desalination. In this study, two commercial and two fabricated nanoparticle-modified polyethersulfone membranes were studied and characterized. In addition, their performance in terms of flux and rejection was investigated. Based on these initial studies, the membranes' suitability for application in brackish water desalination could be ascertained. This information will also be helpful in further improvement of the membranes and in terms of optimizing their performance. The two commercial NF membranes are NF-1 and ASP30 and the two fabricated membranes are polyethersulfone-nanocomposite membranes (PES-5 % Fe3O4, PES-10 % Fe3O4). Pore size diameter, pore size distribution, and roughness were measured using atomic force microscopy. Surface cleanliness of membranes was investigated by field emission scanning electron microscopy. Hydrophobicity and hydrophilicity were also studied using the contact angle. Flux, permeability, and rejection rates were investigated for all membranes. The NF-1 commercial membrane had the highest rejection rate for divalent salt MgSO4, reaching 92 %, while fabricated membrane PES-5 % Fe3O4 had the highest rejection rate for monovalent NaCl salt, reaching 75 %. Commercial NF-1 and ASP30 membranes showed higher flux than fabricated membranes. ASP30 had the highest flux and permeability (176 and 12.77 l/m(-2)h(-1) bar(-1), respectively), while PES-5 % Fe3O4 fabricated membrane had the lowest (47.40 and 4.8 l/m(-2) h(-1) bar(-1), respectively).