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 m ain factors which can potentially influence the iron-removal process. Two-level fractional factorial experimentation was thus utilized to es tablish the main factors having an influence on the iron removal and t o define a subsequent experimental test design. The factors involved i n this study were: temperature, concentration of oxalic and ascorbic a cids, mineral concentration, mixing conditions, and concentration of t he sulfuric acid, The experimental results shown that the effect of ox alic 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 fo r the mineral. Further study is in progress to define the best operati ve conditions considering the economic point of view.