A simple and novel synthetic route to prepare anatase TiO2nanopowders from natural ilmenite via the H3PO4/NH3process

A simple and novel technique for the preparation of anatase TiO(2)nanopowders using natural ilmenite (FeTiO3) as the starting material is reported. Digesting ilmenite with concentrated H(3)PO(4)under refluxing conditions yields a white alpha-titanium bismonohydrogen orthophosphate monohydrate (TOP), Ti(HPO4)(2)center dot H2O, which can be easily isolated via gravity separation from unreacted ilmenite. The addition of ammonia to the separated TOP followed by calcination at 500 degrees C completes the preparation of anatase TiO2. Calcination at temperatures above 800 degrees C converts the anatase form of TiO(2)to the stable rutile phase. The removal of iron from ilmenite during the commercial production of synthetic TiO(2)is problematic and environmentally unfriendly. In the present study, the removal of iron was found to be markedly simple due to the high solubility of iron phosphate species in concentrated H(3)PO(4)with the precipitation of TOP. The titanium content of the prepared samples on metal basis with silica and phosphorous as major impurities was over 90%. Prepared TiO(2)samples were characterized using X-ray fluorescence, Fourier-transform infrared spectroscopy, Raman spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, high-resolution transmission electron microscopy, and X-ray diffraction analyses. The photocatalytic potentials of the commercial and as-prepared TiO(2)samples were assessed by the photodegradation of rhodamine B dye.