Highly Selective Zeolite Membranes as Explosive Preconcentrators

Highly selective thin zeolite MFI membranes are synthesized on porous stainless steel and α-alumina supports using a seeded growth method. An ultraviolet (UV) light treatment is employed as a low temperature alternative to remove the organic structure-directing agent (SDA) to avoid membrane cracking. The feasibility of the use of the MFI membranes as an explosive preconcentrator is examined by measuring the permeation of nitrogen (N(2), an air surrogate) and 1,3,5-trimethylbenzene (TMB) (a 2,4,6-trinitrotoluene (TNT) surrogate) in a mixture of N(2) and TMB. High N(2)/TMB selectivity (>10,000) and reasonable N(2) flux (13.5 mmol/m(2)·s) are observed. On the basis of the flux, a hollow fiber array based preconcentrator is proposed and estimated to provide 1000× concentration within about 1 min using a hollow fiber with a 50 μm internal radius. This high performance explosive preconcentrator may open a new venue for the detection of subppb or lower level of explosives simply in conjunction with conventional explosives detectors.