Kaolin Bleaching by Leaching Using Phosphoric Acid Solutions

This paper presents a study of kaolin ore bleaching from the municipality of Agua Blanca of Iturbide, Hidalgo, Mexico. This process was carried out using solutions of phosphoric acid as the leaching reagent for the iron dissolution process. It is well known that iron oxide is the major contaminant of clay minerals and silicate used in industry. These contents should be decreased, usually by 0.1%, to achieve a required whiteness index of 90% (ISO) or higher. The whitening improves its economic value, making it possible to use it as a high-quality raw material in industries such as ceramics and paper. For this purpose, we examined the effect of parameters such as the concentration of the leaching reagent (0.10 M, 0.50 M, 1 M, and 3 M), temperature (298-373 K), and pH level (1, 2 and 3). The experimental results showed that the studied variables have a great influence over the ability to obtain an iron dissolution percentage of more than 98% after 2 hours and 373 K.