PAMAM dendrimer composite membrane for CO2 separation:: Formation of a chitosan gutter layer

A poly(amidoamine) (PAMAM) dendrimer composite membrane with an excellent CO2/N-2 separation factor was developed in-situ. The In-situ Modification (IM) method was used to modify the surface of commercial porous membranes, such as ultrafiltration membranes, to produce a gas selective layer by controlling the interface precipitation of the membrane materials in the state of a received membrane module. Using the IM method, a chitosan layer was prepared on the inner surface of a commercially available ultrafiltration membrane as a gutter layer, in order to affix PAMAM dendrimer molecules on the porous substrate. After chitosan treatment, the PAMAM dendrimer was impregnated into the gutter layer to form a PAMAM/chitosan hybrid layer. The CO2 separation performance of the resulting composite membrane was tested at a pressure difference of 100 kPa and a temperature of 40 degrees C, using a mixed CO2 (5 vol%)/N-2 (95 vol%) feed gas. The PAMAM dendrimer composite membrane, with a gutter layer prepared from ethylene glycol diglycidyl ether and a 0.5 wt% chitosan solution of two different molecular weight chitosans, revealed an excellent CO2/N-2 separation factor and a CO2 permeance of 400 and 1.6 x 10(-7) m(3) (STP) m(-2) s(-1) kPa(-1), respectively. SEM observations revealed a defect-free chitosan layer (thickness 200 nm) positioned directly beneath the top surface of the UF membrane substrate. After PAMAM dendrimer treatment, the hybrid chitosan/PAMAM dendrimer layer was observed with a thickness of 300 nm. XPS analysis indicated that the hybrid layer contained about 20-40% PAMAM dendrimer. (c) 2006 Elsevier B.V. All rights reserved.