Integration of morphology engineering by β-FeOOH nanorod and fluorine-free hydrophobic modification of PVDF membrane for membrane distillation with excellent wetting and scaling resistance

Abstract

Membrane distillation (MD) is one of the most promising technologies for addressing freshwater scarcity. The membrane is the core component of MD and plays a vital role in determining its overall efficiency. However, severe wetting and scaling of commercial membranes are considered critical limitations of this process. Here these issues are addressed by two simple and effective eco-friendly approaches: I) the controlled in situ growth of FeOOH nanorod structures on a polyvinylidene fluoride (PVDF) matrix by a facile hydrothermal method, which effectively improves the water-repellent properties by creating a rough surface through the formation of additional air pockets on the membrane surface, and II) the fluorine-free chemical grafting of hexadecyltrimethoxysilane (HDTMS), which provides superior wetting resistance by virtue of a slippery surface with enhanced hydrophobicity. The combination of nanorod grafting with surface roughness features and HDTMS with its excellent hydrophobic characteristics resulted in superior wetting and scaling resistance. The prepared membrane exhibited an elevated water contact angle of similar to 142 degrees with a stable flux of similar to 33 kg m(-2) h(-1) over prolonged operation when exposed to both surfactant-containing hypersaline and scale-inducing saline feeds demonstrating superior wetting resistance, anti-scaling ability and strong potential towards practical application. This work highlights the importance of nanomaterial-based morphology control and fluorine-free hydrophobic modification as sustainable approaches for the development of robust membranes towards efficient MD processes.