Abstract
The mineralogy of Nipe clay was characterized by means of X-ray diffraction (XRD), differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), BET surface area, and chemical analysts. The major components of the clay fraction are goethite, gibbsite, hematite and kaolinite. Goethite is the predominant iron oxide as indicated by the high intensity of the XRD peaks. The unit cell dimensions of goethite, estimated from the XRD data, were a = 4.603 Å, b = 9.806 Å and c = 3.002 Å. The unit cell dimensions of hematite were a = 5.037 Å, and c = 13.735 Å. The extent of aluminum substitution in goethite and hematite was also estimated from the XRD data. The mole % Al in goethite, based on the d (111) value, was 15.57 mole percent, whereas when the a-dimension of the unit cell was used, a value of 12.86 mole percent was obtained. The estimated mole percent Al substitution in hematite was 0.67. The hematite/goethite ratio as estimated from the relative intensities of the 104 peak of hematite and the 110 peak of goethite was 0.51. Kaolinite showed a high capacity to absorb IR radiation as indicated by strong absorption peaks around 1000 and 3700 cm-1. The surface area of the clay as determined by the BET method was 55.26 m2/g. The ratio of Feox/Fed was very low (1.17x10-2), indicating that the iron oxides occur in well crystallized form.