Preparation of alumina-iron oxide compounds by gel evaporation method and its simultaneous uptake properties for Ni super(2) super(+), NH sub(4) super(+) and H sub(2)PO sub(4) super(-)

Fe sub(2)O sub(3)/Al sub(2)O sub(3) powders with a range of Fe/Al compositions were prepared by a gel evaporation method to investigate the effect of alumina on the product phases, magnetic properties and simultaneous adsorption of Ni super(2) super(+) (a model heavy metal cation), NH sub(4) super(+) (a model eutrophication-related cation) and H sub(2)PO sub(4) super(-) (a model harmful anion). Precursor gels were prepared by dissolving Fe(NO sub(3)) sub(3).9H sub(2)O and Al(NO sub(3)) sub(3).9H sub(2)O in ethylene glycol, evaporating to dryness, grinding and heating at 300-1000 super(o)C for 5h. The crystalline products were g-Fe sub(2)O sub(3) (maghemite), formed at 300-600 super(o)C, or a-Fe sub(2)O sub(3) (hematite) and AlFeO sub(3), formed >600 super(o)C. The temperatures of the phase change from g-Fe sub(2)O sub(3) to a-Fe sub(2)O sub(3) increased with increasing alumina additions. The resulting lattice parameters suggest that Al super(3) super(+) is incorporated into these phases up to about 15mol.% at 300 super(o)C, falling to 11mol.% in the g-Fe sub(2)O sub(3) formed at 600 super(o)C. The a-Fe sub(2)O sub(3) formed at 700 super(o)C contained 6mol.% Al, increasing to 14mol.% at 1000 super(o)C. The magnetic properties of the samples were measured using a vibrating sample magnetometer. The saturation magnetization values of the g-Fe sub(2)O sub(3)-containing samples increased with the addition of alumina to a maximum value of 61emu/g in the sample containing 95mol.% Fe sub(2)O sub(3) heated at 400 super(o)C. The simultaneous adsorption of Ni super(2) super(+), NH sub(4) super(+) and H sub(2)PO sub(4) super(-) from water was investigated by a batch method. The highest adsorption values were found for the sample containing 80mol.% Fe sub(2)O sub(3) heated at 600 super(o)C, which contained both g-Fe sub(2)O sub(3) and a-Fe sub(2)O sub(3). It was therefore concluded that the addition of alumina to iron oxide affects the crystalline phases and phase changes, and enhances the simultaneous cation and anion uptake ability of the materials.