Scaling and wetting are the main problems in the DCMD process that affect the long-term use of polypropylene (PP) membranes. To address this, robust superhydrophobic PP membranes were developed, though challenges remain in ensuring coating adhesion to low-energy PP surface and controlling coating thickness and porosity. This study employed the thermally induced phase separation (TIPS) method to fabricate PP membranes. To obtain superhydrophobic PP surfaces, a modification using silica nanoparticles (NP) functionalized by hexadecyltrimethoxysilane (HDTMS) with or without cyclic olefin polymer (COP) was explored. Therefore, the dispersion of the surface modifiers in different solvents was applied using a novel technique comprising simultaneous spray coating and phase separation. HDTMS-SiO2 NP were selected for their non-toxicity, cost-effectiveness, and ability to enhance surface roughness and reduce surface free energy. The COP roles are increasing coating layer strength, stability of nanoparticle immobilization, and adhesion of the coating to the substrate. The addition of a non-solvent for COP to the dispersion causes the formation of a more porous coating layer. The durable superhydrophobic PP membrane modified using a dispersion of HDTMS-silica NP in a solution of COP in toluene and the non-solvent acetone, showed an elevated water contact angle (WCA) (159.7°) and a reduced sliding angle (SA) (<10°). This membrane demonstrated constant flux and high rejection (99.99%) for various feeds (35 g/L and 100 g/L NaCl, and simulated seawater RO brine) in DCMD process for 24 h. This method offers durable and superhydrophobic coating on PP membranes with excellent stability and performance in MD desalination.

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