In the present study, oxalic acid was used as a leaching reagent to remove iron from a kaolin mineral. Statistical analysis was conducted to determine the most influential factors in the dissolution of iron from the kaolin mineral. Our goal was ferric iron solubilization and its reduction to ferrous iron to improve the iron removal in the acid medium. Leaching experiments were conducted at atmospheric pressure. A two-level factorial design of the type 2⁴ was utilized. The dependent variable was the percentage of dissolved iron, and the dependent variables in this study were acid concentration (0.35 and 0.50 M), temperature (75 °C and 100 °C), leaching time (2 and 4 h), and pH (1.5 and 2.5). An analysis of variance revealed that the effects of the factors temperature (b), pH (d), and the combined effects of temperature and time (bc) resulted in the maximum dissolution of iron of 88% at 100 °C, giving a kaolin mineral with a whiteness index 93.50%.

<p>This paper presents a study of kaolin ore bleaching from the municipality of Agua Blanca of Iturbide, Hidalgo, México. 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 .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, and3 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.</p>