Abstract
Magnetite (Fe 3O 4) crystalline membranes were prepared on a porous stainless steel support by a sol–gel method for the sake of hexavalent chromium [Cr (VI)] removal from aqueous solution. The impact of the fabrication parameters including concentrations of casting solutions, multiple coatings, sintering atmospheres and temperatures, as well as heating ramp rates was studied. The morphologies were characterized by scanning electron microscopy and Cr (VI) concentration was determined by spectrophotometry. Planar and continuous membrane was obtained when fired initially in air followed with N 2 and the air–nitrogen changing temperature was 400 °C. The membrane consisted of small cubic grains when the casting solution was 0.032 mol/L and the thickness was ∼5 μm. When the concentration was 0.065 mol/L, the membrane was composed of small cubic grains at the bottom and big pillar ones on the top and the thickness increased to ∼25 μm. Repeated coatings had no significant impact on the morphologies and thicknesses of the resultant membranes. When fired at 850 °C, pure magnetite membranes with clear cubic grains at the bottom and clear pillar ones on the top were obtained. Pillar grains can be obtained when sintered at a heating ramp rate of 1 °C/min. The Cr (VI) removal test exhibited an elimination efficiency of 92.5%, indicating a promising application to remove Cr (VI) from aqueous solution.
Published Version
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