Antibacterial Properties Enhancement of Layer-by-Layer Self-Assembled Nanofiltration Membranes

Membrane technology is now being widely used in the field of water treatment for its unique advantages. Layer-by-layer (LbL) self-assembly technique is a convenient and versatile method of modified nanofiltration (NF) membranes fabrication, which can be used to control the thickness and the surface properties of membranes by chemical deposition of polyelectrolytes. Herein, a new kind of composite NF membrane with enhanced antibacterial properties was successfully fabricated through LbL self-assembly method, having polyether sulfone (PES) ultrafiltration (UF) membrane as support layer, N-[(2-hydroxy-3-trimethylammonium)propyl] chloride chitosan (HTCC) and polyacrylic acid (PAA) as active layer, and epichlorohydrin (ECH) as crosslinking reagent. Subsequently, nanosilver was finally loaded on the membrane surface by photoreduction technique. Our results revealed that the positively charged four semi-assembled membranes prepared using 5 g/L HTCC aqueous solution, 1 g/L PAA solution (pH = 6-8), and 0.5 g/L NaCl as supporting salt exhibited optimum performance. Atomic force microscopy and contact angle tests showed that the prepared membranes improved the surface roughness and hydrophilicity as compared to those of the polyether sulfone (PES) membranes. The retention test indicated that the (HTCC/PAA)4HTCC membranes exhibited highly-efficient removal of pharmaceuticals and personal care products in the order of Amlodipine > Atenolol > Carbamazepine > Ibuprofen. The X-ray Diffraction results confirmed the presence of nano-silver on the membrane surface. In addition, the prepared membranes exhibited excellent antibacterial activity, especially against gram-negative bacteria.