Zirconium dioxide membranes decorated by silanes based-modifiers for membrane distillation - Material chemistry approach

Zirconium dioxide membranes (3 nm and 200 nm) were chemically modified by silane-based modifiers with different degrees of fluorination. Comprehensive material characterization has been performed before and after the modification process by goniometric, and microscopic techniques. Wetting properties has been accomplished by applying the Zisman method, Kao diagram, spreading pressure, and critical surface tension. The mechanical, tribological, and separation features of all membranes were investigated as a function of grafting time for 5h, 15h, and 35h.The performance of the membrane was assessed in air-gap membrane distillation processes. Nonfluorinated membranes possessed better transport properties and better mechanical stability in comparison with fluorinated ones which enable the generation of porous, hydrophobic, crack-free material, optimized for MD. Grafting with short fluorocarbon chains (FC6) produced highly hydrophobic materials (CA =145 degrees) with low roughness (R-q = 6.58 nm) compared to grafting with long fluorocarbon chains (FC12). On the other hand, FC6 showed a highly permeable character and elimination of problems related to substantial flux reduction and pore blocking.