Lysozyme Anti-Fouling Properties of Carbon Nanotube-Polypropylene Nanocomposite Feed Spacers for Reverse Osmosis Application

Fouling significantly negatively impacts the water treatment performance of full-scale reverse osmosis (RO) modules. This work evaluates and compares the antifouling properties of a commercial polypropylene (PP) and a laboratory-made nanocomposite feed spacer based on a polypropylene/multi-walled carbon nanotubes composite (CNT-PP) using lysozyme (LYZ) protein as a foulant model. The interaction between the protein and the spacers was monitored by fluorescence microscopy, finding the highest adhesion of LYZ on the PP compared with the CNT-PP spacer. By AFM and contact angle measurements, it was found that the highest roughness of the CNT-PP spacer can provide a larger surface area for water molecules, allowing the formation of an interfacial water layer that prevents LYZ adsorption over the spacer. Molecular dynamics simulations show a stronger binding affinity of LYZ to the PP structure than that of the CNT-PP spacer and the formation of an interfacial water layer on the CNT-PP surface. Permeate studies using spiral-wound modules show that the CNT-PP spacer has a mass transfer coefficient 2 times higher than that of the PP feed spacer. It was concluded that the CNT-PP spacer is promising to be used as an ecofriendly alternative in RO modules to mitigate LYZ in water treatment, especially for industry wastewater recycling.