Tuning polyamide membrane chemistry for enhanced desalination using Boc-protected ethylenediamine and its in situ Boc-deprotection

Freshwater scarcity driven by population growth and industrialization necessitates advanced desalination. This work enhances polyamide reverse osmosis membranes by tuning the active layer chemistry via Boc-protected ethylenediamine (EDA). One amine of EDA was protected (EDA-Boc) so the other could participate in interfacial polymerization (IP) with meta-phenylenediamine (MPD) and trimesoyl chloride (TMC), enabling in situ control of active-layer chemistry. After polymerization, Boc deprotection generated hydrophilic ammonium groups on the surface. Three membranes were fabricated and characterized: MPD-TMC (control), MPD-TMC-EDA-Boc, and MPD-TMC-EDA-Deboc. At 20 bar with 2000 ppm NaCl, MPD-TMC-EDA-Deboc showed 98 ± 0.5% salt rejection and 25 L m⁻² h⁻¹ flux, a 25% flux increase over the control. For seawater nanofiltration permeate (TDS 33,700 ppm), it achieved 97% rejection and 23 L m⁻² h⁻¹ at 20 bar. Antifouling improved with MPD-TMC-EDA-Deboc (95 ± 1% flux recovery) vs control (93 ± 1%). The Boc protection/deprotection strategy significantly improves polyamide desalination membrane performance.

Hilal Ahmad, Abdul Waheed, Fahad Ayesh Alharthi, Christopher Michael Fellows, Umair Baig, Isam H. Aljundi