Wiston Ho Assignments Solution Manual on Polymer Membrane Handbook

1. 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 thin film with a thickness 10 of special polymer processing an oxygen permeability of 1 Barrer [1 Barrer = 10 x 10-10 cm3(STP) / (cm2.s.cm Hg)] and nitrogen permeability of 0.02 Barrier deposited by this method on a composite membrane comprising an asymmetric polysulfone (PSF) ultrafiltration membrane with a microporous layer having an oxygen permeance of 0.2 cm3 (STP) / (cm2-s-cm Hg) and a 0.02 micron dense layer having an oxygen permeability of 1.4 Barrers and nitrogen permeability of 0.25 Barrer covered with a coating of silicone rubber with an oxygen permeability 550 Barrers and a nitrogen permeabkility 260 Barrers. The silicone rubber has a thickness of 1 micron above the PSF dense layer, and it has penetrated to all the defect pores in the entire dense PSF layer with a defect pore area of 0.02 %, but does not coat the microporous PSF layer. 1) What is the 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? 3) Calculate the oxygen fluxes and oxygen/nitrogen separation factors for the following two composite membranes: a. Silicone rubber-coated PSF membrane (three layers) b. Special polymer layer onto the silicone rubber-coated PSF membrane (four layers) This is the so-called ideal separation factor. 1) For cases in which the permeate pressure (P’’) cannot be ignored, prove that the true separation factor is related to in the following equation: Where r = p’’ /p is the ratio of the permeate pressure to the retentate pressure. Note: is equal to for r = 0. 2) For polyimide membrane process to recover hydrogen from a refinery waste stream from a hydrotreating operation, i.e., to separate hydrogen from methane, a methane-rich product contains 60 mol % methane and 40 mol% hydrogen. The ideal separation factor of hydrogen vs. methane is 125. If p’’ / p = 0.5, find the value of the true separation factor and the composition of the hydrogen-rich product. Explain physically why is so much less than and propose a way to increase . 3) Show that the value of is required to provide a given recovery of component j in the retentate (a given composition ), with fixed compositions of the binary feed and the permeate, is given by the following expression: 1. Name three polymers most commonly used in the preparation of microporous membranes via phase inversion for ultrafiltration and microfiltration. 2. Name the six steps in the membrane preparation via the phase inversion technique. 3. Show typical phase diagrams, including composition paths in a ternary system consisting of polymer (P), solvent (S) and nonsolvent (NS), in the membrane preparation via phase inversion for: 1) Instantaneous liquid-liquid demixing for the preparation of porous membranes for ultrafiltration and microfiltration 2) Delayed onset of liquid-liquid demixing for the preparation of dense membranes for gas/vapor separations and pervaporation. 4. In the membrane preparation via phase inversion for a ternary system consisting of polymer (P), solvent (S), and nonsolvent (NS): 1) Consider a system that demixes at 30 wt. % nonsolvent with the critical point located at 5 wt. % polymer. Draw the typical phase diagram for the ternary system with the demixing region and label various points and regions and tie line on the diagram. 2) Polymer solutions A and B consists of 15 wt. % polymer, 80 wt. % solvent and 5 wt. % nonsolvent and 30 wt. % polymer, 65 wt. % solvent and 5 wt. % nonsolvent, respectively. Mark the locations of the polymer solutions A and B in the phase diagram. Read more