Mitigation of Thin-Film Composite Membrane Biofouling via Immobilizing Nano-Sized Biocidal Reservoirs in the Membrane Active Layer

This work investigates the use of a silver-based metal–organic framework (MOF) for mitigating biofouling in forward-osmosis thin-film composite (TFC) membranes. This is the first study of the use of MOFs for biofouling control in membranes. MOF nanocrystals were immobilized in the active layer of the membranes via dispersion in the organic solution used for interfacial polymerization. Field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) characterization results showed the presence of the MOF nanocrystals in the active layer of the membranes. The immobilization improved the membrane active layer in terms of hydrophilicity and transport properties without adversely affecting the selectivity. It imparted antibacterial activity to the membranes; the number of live bacteria attached to the membrane surface was over 90% less than that of control membranes. Additionally, the MOF nanocrystals provided biocidal activity that lasted for 6 months. The immobilization improved biofouling resistance in the membranes, whose flux had a decline of 8% after 24 h of operation in biofouling experiments, while that of the control membranes had a greater decline of ∼21%. The better biofouling resistance is due to simultaneous improvement of antiadhesive and antimicrobial properties of the membranes. Fluorescence microscopy and FE-SEM indicated simultaneous improvement in antiadhesive and antimicrobial properties of the TFN membranes, resulting in limited biofilm formation.