ESR investigation of deferration treatment of iron-rich kaolinite clay from Deopani, Assam, India

• Published in: Current science (Bangalore) 2006-07, Vol.91 (1), p.86-90
• Main Authors: Sengupta, P., Saikia, N. J., Bharali, D. J., Saikia, P. C., Borthakur, P. C.
• Format: Article
• Language: English
• Subjects: Acid soils; Beneficiation; Clays; Electron paramagnetic resonance; Fractions; Hematite; Impurities; Kaolinite; Leaching; Minerals; RESEARCH COMMUNICATIONS
• ISSN: 0011-3891

Kaolin, available at Deopani, Assam, India, is yet to be commercially exploited due to lack of detailed characteristics and appropriate process for beneficiation. The characteristics of the clay, as revealed by chemical, XRD, FTIR and SEM-EDX analyses and beneficiation by physico-chemical methods were reported earlier. The Fe content of the clay could be reduced considerably from a high value of 9.48 to 1.0% by adopting simple beneficiation techniques due to favourable Femineralogical form, but it is difficult to remove the impurities completely. This communication reports the characteristics of the clay and its beneficiated products, as revealed by ESR investigation. The clay contains relatively high amounts of both structural and non-structural iron and minor amount of Mn. The g factors calculated from the ESR signals are used to investigate the effect of the beneficiation techniques employed on structural and non-structural Fe. Magnetic separation and size fractionation yield products with high amount of structural iron. Oxalic acid that acts both as a complexing and leaching agent at relatively low concentration preferentially leaches structural iron, and at higher concentration removal of non-structural iron is enhanced. Increase in temperature initially from ambient condition results in preferential removal of the non-structural iron and thereafter it becomes the same for both forms of iron.