Improved performance of thin-film nanocomposite nanofiltration membranes as induced by embedded polydopamine-coated silica nanoparticles

We modified thin-film nanofiltration membranes by embedding in them silica nanoparticles (SiNPs) coated with polydopamine (PDA), which is well-known to mimic the adhesive characteristics of mussels. The coating process was triggered by the oxidative self-polymerization of dopamine on the surface of SiNPs, and the membranes were fabricated through interfacial polymerization (reaction between piperazine and trimesoyl chloride, TMC). Thin-film nanofiltration membranes embedded with PDA-SiNPs (TFNPDA-SiNPs) were compared with pristine polyamide membrane, as well as with polyamide membrane embedded with uncoated SiNPs. Energy-dispersive X-ray spectroscopy confirmed that TFNPDA-SiNPs contained more nanoparticles than the polyamide membrane with uncoated SiNPs. Accordingly, the hydrophilicity of TFNPDA-SiNPs was higher. TFNPDA-SiNPs fabricated from using a concentration of 0.35 g PDA-SiNPs/g TMC delivered the highest pure water flux of 80.0 ± 4.6 L⋅m−2⋅h−1 at 6 bar; salt rejections were as follows: RNa2SO4 = 97%; RMgSO4 = 94%; RMgCl2 = 68%; RNaCl = 35%. The TFNPDA-SiNPs also demonstrated the greatest antifouling ability, as its flux was the highest at the end of three cycles of antifouling tests, where bovine serum albumin was used as model protein foulant.