Innovative high flux/low pressure blend thin film composite membranes for water softening

Nanofiltration (NF) thin film composite membranes were prepared via interfacial polymerization using piperazine with isophthaloyl chloride on porous PES/PAN blend membrane. The prepared membranes were characterized through chemical structure, morphology, surface charge studies and separation performance. All the variables are taken into consideration including reactive monomers amount. The monomers ratio were 1: 0.3: 0.3: 0.3 that corresponds to piperazine: sodium hydroxide: dodecyl sodium sulfate: isophthaloyl dichloride respectively. Soaking time for amine solution was 30 min, while it was 10 min in organic chloride solution. After interfacial polymerization the membranes have been annealed at temperature 80 °C for curing time 10 min. These were the optimum conditions which greatly enhanced the flux and the salt rejection of NF thin film composite membranes. The membranes have rejection percent in the order of 99.9, 99, 82, and 72% for Na2SO4, MgSO4, CaCl2, NaCl respectively without reducing water productivity. This study offers separation of 7000 ppm salt solution with low operating pressure (5 bars) compared with previous studies. The fabricated membranes were applied for 30 days with steady-state flux keeping their polyamide layers. As well; the fabricated membrane with the optimum operating conditions has a better fouling resistance for humic acid and molecular weight cut off 600 Da.