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Effect of (TiO<inf>2</inf>: ZnO) ratio on the anti-fouling properties of bio-inspired nanofiltration membranes

Abstract:

Membrane fouling and biofouling, which arises from the nonspecific interaction between the membrane surface and foulants, significantly impedes the efficient application of membrane technology. The addition of nanoparticles could have an impact on the properties of membranes used for nanofiltration. Nanoparticles can provide various functionalities to a membrane but, there are very few studies of the effect of mixing catalysts in PDA-modified membranes. In this study, polydopamine has been used to firmly bind a combination of nanoparticles on thin film composite (TFC) membranes. Two simple methods (a one-step and a two-step method) to assemble a multifunctional (TiO2, ZnO) layer of nanoparticles onto a commercial NF membrane as support have been evaluated by applying fast deposition of polydopamine (PDA). The membrane performance was evaluated based on the relative flux decline. Results show that the modification methods did not compromise the rejection of MgSO4, combined with an increase ∼15% in the rejection of NaCl. A 25% increase in the hydrophilicity of the modified membranes compared to pristine membrane was evidenced. In addition, the two-step modification method has antimicrobial activity for an ultralow load of 0.03 wt% ZnO nanoparticles; the antimicrobial activity increased when the membrane had a combination of TiO2:ZnO nanoparticles at 1:2 and 2:1 ratios using Bacillus Subtilis as model bacteria. The photocatalytic activity of the nanoparticles layer was demonstrated through the removal of methylene blue from a solution contacting the membrane when exposed to solar radiation.