Recycled-Polystyrene Reinforced Polyvinylidene Fluoride Membranes: Exploring Silicate Surface Modification for Vapor Passage During Saline Water Desalination

Abstract

This work describes developing, characterizing, and evaluating porous hydrophobic membranes for hard groundwater and seawater desalination. The hydrophobic membranes were prepared from polyvinylidene fluoride (PVDF) blended with triacetin, expanded polystyrene (EPS), and activated carbon. Membrane structural analysis with electron microscopy revealed a dual cross-sectional structure of elongated and narrow macro voids terminated by a spongy sub-structure. Further surface modification with silicone oil resulted in a significant increase in surface hydrophobicity to 120.14 (±5.27)°. Modification also led to an increase in surface pores, which led to a better permeate flux of 3.66 kg/m²h compared to the permeate flux of the pristine membrane of 0.67 kg/m²h. This increased flux can be explained by the improved surface porosity that enhanced vapor permeability, resulting in increased permeate flux. The membranes recorded over 99% salt rejection for both hard groundwater and seawater, which is acceptable for membrane distillation. Trace concentrations of Na, Cl, and Mg were detected on the active layer after seawater desalination, indicating the breakthrough of these ions and possible pore wetting. The main constituents of the foulants on the support layer were composed of sulfur (S) and silicon (Si).