Structurally Functionalized Polyurethane Foam for Elimination of Lead Ions from Drinking Water
Pages 16-25
Nidal Abu-Zahra and Subhashini Gunashekar

DOI: http://dx.doi.org/10.6000/1929-5995.2014.03.01.3

Published: 02 April 2014

Abstract: Polyurethane foams functionalized with Sulfonic acid groups have been found to be strong cation exchangers. This novel property of the foam was used to exchange lead (Pb²⁺) ions from aqueous solutions. Polyurethane foam synthesis is based on addition polymerization of the highly reactive isocyanate (-NCO) groups of an isocyanate with the hydroxyl (–OH) groups of a polyol to form the urethane species. Toluene-2,4-2,6- diisocyanate was reacted with Polypropylene glycol 1200 in 2:1 molar ratio to form a linear pre-polymer. The linear pre-polymer was further polymerized using a chain extender, N, N-bis (2-hydorxyethyl)-2-aminoethane-sulfonic acid (BES). BES also acts as a functional group to exchange Pb²⁺ ions. A set of experiments were designed to study various process parameters. The functionalized polyurethane foam was characterized by Fourier transform infrared spectroscopy, gel permeation chromatography, scanning electron microscopy, and energy dispersive x-ray spectroscopy. The Pb²⁺ ion exchange capacity was determined using an Inductively Coupled Plasma Mass Spectrometer. The maximum Pb²⁺ ion exchange capacity of the foam was found to be 47 parts per billion per gram (ppb/g) from a 100 parts per billion (ppb) Pb²⁺ solution over a period of 60 minutes. A multistage batch filtration process increased the Pb²⁺ ion removal to 50-54 ppb/3g of foam over a period of 90 minutes.