Boehmite, gamma-AlO(OH), recovered from aluminium dress tailings (ADT) and steel-pickling-chemical waste (SPW) were used to prepare 1-10 wt.% FeOx/Al2O3 catalysts. Surface and bulk properties of the catalysts were characterized by nitrogen sorptometry, thermogravimetry (TG) of adsorbed pyridine, X-ray photoelectron spectroscopy and X-ray powder diffractometry. The results have shown the catalysts to consist of highly dispersed alpha-Fe2O3 particles on high-surface area gamma-Al2O3, but cannot exclude the coexistence of monolayer species of Fe(II)-O and/or Fe(III)-O, as well as Fe(III) incursions into the support bulk structure. Activity tests of the catalysts towards ethanol dehydration (at 140-250 degrees C) in the gas phase, have revealed that increasing amounts of supported FeOx species could turn gamma-Al2O3 from being diethyl ether selective to ethene selective, without changing its originally high dehydration activity towards the alcohol, Consequent modifications of the surface acid site density have been correlated to observed changes in the alcohol dehydration rate. Hence, the switching of the catalyst selectivity to ethene formation has been suggested to follow suppression (or elimination) of bi-molecular reaction mechanism necessary for ether formation due to Fe(III) incursion into the support, and/or ether decomposition on Fe2O3 particles. (C) 2000 Elsevier Science B.V. All rights reserved.