Iron removal from a kaolinitic clay by leaching to obtain high whiteness index.

Beige kaolin clays were crushed and sieved. The mineral was characterized by X-ray diffraction and chemically analyzed by atomic absorption spectrophotometry. The material below 37 microns was leached with oxalic acid. A study of main variables of the leaching process in different ranges was realized: time (0 to 120 min), temperature (25 to 100 C) and acid concentration (0.01 to 0.5 M). Crystallographic analysis of the initial sample indicates the presence of kaolinite, iron oxides in the form of magnetite and iron-titanium oxides. By this method it was possible to obtain iron extraction percentages over 80% and whiteness index above to 90%.