Growing nearly vertically aligned ZnO nanorod arrays on porous α-Al2O3 membranes to enhance the separation of MTBE from aqueous solution

The separation of methyl tertiary butyl ether (MTBE) from aqueous solution by pervaporation-based membrane technology has attracted much attention recently. The present work proposed a novel strategy to enhance the MTBE/water separation performance of porous α-Al 2 O 3 membranes. ZnO seeds were planted on the surface of α-Al 2 O 3 membranes by the deposition and decomposition of zinc acetate, followed by growing ZnO nanorod arrays (ZNA) on the seeded α-Al 2 O 3 membranes by hydrothermal reaction in the mixed hydrated zinc nitrate (HZN) and hexamethylenetetramine (HMTA) solution. Finally, the membranes were hydrophobized by grafting fluoroalkylsilane (FAS) onto their surface. The results show that the MTBE/water separation factor has been dramatically promoted from 7.7 for the α-Al 2 O 3 membranes to 55.7 for the ZNA-covered α-Al 2 O 3 membranes. The promotion may be attributed to the nearly vertically aligned ZnO nanorod arrays, which provide much surface area to load more fluorocarbon groups that are amiable to MTBE molecules and supply a superhydrophobic surface. The MTBE in the permeate mixture has been concentrated to as high as 72.9 wt%, in striking contrast to 4.6 wt% in the feed solution. The obtained membranes are highly stable upon long-term operation.