An oxygen transport membrane made from La0.6Sr0.4Co0.2Fe0.8O3 (-) (delta) (LSCF6428) has been tested for air separation by oxygen permeation at 900 degrees C with the introduction of sulfur in the form of hydrogen sulfide. 200 ppm of hydrogen sulfide was fed either in the sweep-side (argon-side) or the air-side. The membrane was exposed to hydrogen sulfide for 100 h. Results show that the presence of hydrogen sulfide negatively influenced the oxygen permeation due to the formation of strontium sulfate blocking the oxygen permeation pathway. When the hydrogen sulfide was removed from the system, the oxygen permeation was partially restored in the case of argon-side contamination, while being fully restored in the case of air-side contamination. (C) 2014 Elsevier B.V. All rights reserved.