(373a) Designing, Preparing and Characterizing Alkali Treated Graphitic Carbon Nitride Thin Film Composites (TFC) Membranes for Efficient Dye Salty Water Separation.

Ultra-high water permeance, almost zero salt rejection and ~100% dye rejection is of great interest for waste water treatment especially in textile dye-salty water separation. Herein, we fabricated alkali treated graphitic carbon nitride (GCN) ultrathin thin-film composite membranes using polydopamine (PDA) chemical crosslinking to have efficient dye separation from salts without sufficient loss in water passage. Crosslinking using PDA adhere GCN on commercial support such as polysulfone (PSF) and can fine tune surface channel sizes for effective dye water separation. First, the membranes were characterized using FTIR and water contact angle measurement to see incorporation of GCN/PDA on the surface of PSF supports. Moreover, GCN/PDA crosslinking conditions and GCN/PDA mass ratio was optimized for efficient dye-salty water separation. For e.g. 0.4 mg/0.4 mg loaded GCN/PDA on PSF20k support with crosslinking condition of 0-5ºC/30 mins and 23 ºC/10 mins showcases optimum separation performance (Water permeance: 345 ± 22 LMH/bar, % rejection of Congo red dye, 697 Da: 97.6 ± 0.4 and % rejection of Na₂SO₄ salt: 16 ± 0.5). Water permeance of GCN/PDA membrane is 30, 8 and 3.5 times higher than commercial NF-90 membrane, commercial ultrafiltration membranes (with molecular weight cutoff of 2000 Da) and graphene oxide (GO)/PDA crosslinked membranes, respectively. This efficient and attractive separation performance manifest application of GCN based membranes in dye-salty water separation.