The preparation, characterization, and sorption properties for Ni(II) of combined phases of iron oxyhydroxide and montmorillonite were investigated. Two different preparation procedures were explored. In the first method, Fe(III) was contacted with montmorillonite at pH 2.5, and ferrihydrite was formed on the montmorillonite surface by slowly raising pH to 8.0 (Fe-mont). In the second method, O-2 was bubbled through a solution (pH 7.0) containing Fe(II) and montmorillonite. This caused Fe(III) to precipitate as lepidocrocite (lep-mont). Batch adsorption experiments and the physical chemical properties of the solids, e.g. specific surface area, the point of zero charge, and the particle size distribution reflected a varying degree of interaction among the phases. In the Fe-mont system, a ferrihydrite coated montmorillonite surface was created. The result was an increase in specific surface area and sorption capacity for Ni(II) compared to the pure solids. The isoelectric point observed was typical for pure ferrihydrite. In the lep-mont system, predominantly separate phases of lepidocrocite and montmorillonite were created. The specific surface area, the isoelectric point, and the sorption capacity were significantly better predicted given the properties and weight fractions of the individual phases. (C) 2000 Elsevier Science B.V. All rights reserved.
