1. 15 Points By the use of a Langmuir-Blodgett method, very thin films can be prepared, and this method may be useful for high selectivity but low permeability polymers. A very thin film with a thickness of 10A of a special polymer possessing an oxygen permeability of 1 Barrer (1 Barrer =1010cm3(STP)cm/(cm2scmHg)) and a nitrogen permeability of 0.02 Barrer is deposited by this method on a composite membrane comprising 3 layers from top to bottom: (1) a 1-micron thick silicone rubber coating with an oxygen permeability of 550 Barrers and a nitrogen permeability of 260 Barrers, (2) a 0.02-micron thick, dense layer of polysulfone (PSF) with an oxygen permeability of 1.4 Barrers and a nitrogen permeability of 0.25 Barrer, which has a defect pore area of 0.02% caulked by the silicone rubber, and (3) a microporous PSF layer having an oxygen permeance of 0.2cm3 (STP) /(cm2scmHg). The dense and microporous PSF layers constitute a typical asymmetric PSF ultrafiltration membrane. The coating of a silicone rubber caulking layer on top of the PSF ultrafiltration membrane, in which the silicone rubber plugs up the defect pores in the dense PSF layer, makes the composite membrane useful for O2/N2 gas separation. (1) What are the O2/N2 selectivity and oxygen flux for the special polymer layer exposing to air (assuming a negligible pressure on the permeate side)? (2) Is it justifiable to neglect the permeation resistance of the microporous PSF layer by comparing this resistance with the other resistances? [Hint: The selectivity of O2/N2 in a microporous PSF support is typically about one.] (3) Calculate the oxygen fluxes and oxygenitrogen separation factors for the following two composite membranes: (a) Silicone rubber-coated PSF membrane (three layers) (b) Special polymer layer on top of the silicone rubber-coated PSF membrane (four layers)