Wetting study of Dual-Layer Hydrophilic/Hydrophobic Composite Membranes Coated with Nanoparticles for Membrane Distillation
Sprache des Vortragstitels:
Englisch
Original Tagungtitel:
Jahrestreffen der ProcessNet-Fachgruppen Mechanische Flüssigkeitsabtrennung und Membrantechnik
Sprache des Tagungstitel:
Deutsch
Original Kurzfassung:
Membrane distillation process is seldom employed in industrial scale since the presence of low surface tension materials in feed promotes membrane pore wetting. Membrane chemistry and geometrical structure play an important role to determine wetting by dictating surface tensions at macrostructures and surface roughness at microstructures. In this study, a dual layer hydrophilic/hydrophobic composite membrane for usage in membrane distillation (MD) was synthesized. The polymer solution composed of polyvinylidene fluoride 15% w/w in dimethylacetamide was cast on a non-woven hydrophilic support (NWS) layer atop and a pre-wetted hydrophobic NWS layer at the bottom to generate a difference in surfaces energy. To increase membrane roughness parameters and consequently membrane wetting resistibility, the phase inversion membrane was dip coated by SiO2 nanoparticles. Depositing nanoparticles (nPs) on membrane surface to form a microstructure on top of macrostructure as it is in natural superhydrophobic surfaces such as lotus leaf increases water repelling effect of the membranes. Atomic force microscope (AFM) and contact angle (?) goniometry are employed to measure the surface roughness and contact angle of the fabricated membranes. The contact angle measurements showed that the membranes maintained its superhydrophobicity (?>150°) against model wetting solutions (0.4 mM SDS). AFM measurement revealed that depositing nPs on membrane macrostructure increased membrane roughness by ~25%. A 6 h direct contact membrane distillation (DCMD) experiments in the presence of a surfactant (sodium dodecyl sulphate, SDS) with the concentration up to 0.4 mM did not show any contamination in permeate and kept the salt rejection to ~100%. The obtained flux in the DCMD experiments (~18 kg/m2/h) was comparable to other composite MD membranes