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

Abstract

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%.