Development of a Bleaching Process for a Kaolin of Industrial Interest by Oxalic, Ascorbic, and Sulfuric Acids: Preliminary Study Using Statistical Methods of Experimental Design

In the present work a preliminary study of iron removal from a yellow kaolin supplied by ECC International (Europe) Ltd. was performed using mainly oxalic and ascorbic acids in sulfuric acid solutions. The aim of the initial phase of research was to determine the effects of the main factors which can potentially influence the iron-removal process. Two-level fractional factorial experimentation was thus utilized to establish the main factors having an influence on the iron removal and to define a subsequent experimental test design. The factors involved in this study were: temperature, concentration of oxalic and ascorbic acids, mineral concentration, mixing conditions, and concentration of the sulfuric acid. The experimental results shown that the effect of oxalic and ascorbic acids and of the temperature are the most important. In the investigated conditions, the maximum iron extraction yield was 43−45% after 3−4 h of treatment indicating a limit of iron removal for the mineral. Further study is in progress to define the best operative conditions considering the economic point of view.