(222b) Facilitated Transport Membranes for Environmental, Bio and Energy Applications

This presentation covers recent advances in facilitated transport membranes, including three areas: (1) the removal and recovery of heavy metals from waste waters by supported liquid membranes (SLMs) with strip dispersion, (2) the extraction and recovery of antibiotics from aqueous solutions by SLMs with strip dispersion, and (3) fuel processing with hydrogen sulfide- and carbon dioxide-selective membranes for fuel cells. These areas will be discussed together with our research results. New membrane technology based on SLMs with strip dispersion for the removal and recovery of metals, including chromium, copper, zinc, and strontium, from waste waters has been developed. The technology not only removes the targeted metal in the treated effluent allowable for discharge or recycle, but also recovers the metal at high concentration and purity suitable for resale or reuse. The stability of the SLM has been ensured by a modified SLM with strip dispersion, where the aqueous strip solution is dispersed in the organic membrane solution. The SLMs with strip dispersion have potential for extraction and recovery of antibiotics and biochemicals from fermentation broths and aqueous solutions. For example, Cephalexin has been extracted and concentrated significantly with a very high recovery.

Recently, we have synthesized hydrogen sulfide- and carbon dioxide-selective membranes by incorporating amino groups into crosslinked polyvinylalcohol and newly polymerized sulfonated polybenzimidazole copolymer matrixes for fuel processing for fuel cells. The membranes have shown high hydrogen sulfide and carbon dioxide permeabilities and selectivities vs. hydrogen, carbon monoxide and nitrogen up to 170oC. Hydrogen sulfide permeates through the membrane much faster than carbon dioxide. This allows the complete removal of hydrogen sulfide in the treated synthesis gas before water-gas-shift (WGS) reaction. Our initial experiments have shown a nearly complete removal of hydrogen sulfide from 50 ppm in the synthesis gas feed to about 10 ppb in the hydrogen product. Using the membrane, we have obtained <10 ppm carbon monoxide in the hydrogen product in WGS membrane reactor experiments via carbon dioxide removal. The data have been in good agreement with modeling prediction. We also removed carbon dioxide from a syngas containing 17% carbon dioxide to <30 ppm and obtained >98% carbon dioxide in the acid gas stream for sequestration.