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Title KINETICS AND MECHANISMS OF NITRIC ACID LEACHING OF ALUMINA FROM AMAGUNZE CLAY
Journal International journal of Engineering And Applied Science
Publisher Faculty of Engineering, Nnamdi Azikiwe University, Awka Nigeria.
Issue 1
ISSN 1119-8109
Pages 63-82
Subject Chemical Engineering
Date of Publication November 4, 2018

AUTHOR(S) Ikechukwu A. Nnanwube and Okechukwu D. Onukwuli

ABSTRACT

This study was concerned with the physicochemical characterization and kinetics study of Amagunze clay dissolution in nitric acid. The effects of acid concentration, temperature, particle size, stirring speed and solid/liquid ratio on the leaching of alumina from Amagunze clay were investigated. The X-ray fluorescence data revealed the presence of Al2O3 and SiO2 as major oxides. Metals such as Mg, K, Ca, andTi exist as minor elements while Cr, Zn, Mn and Sr exist as traces. The analysis of Amagunze clay by X-ray diffraction revealed the presence of microline and quartz. The FTIR result confirmed the results of XRF and XRD analysis by revealing the presence of relevant functional groups. Results of the leaching studies showed that alumina dissolution in nitric acid increased with increasing concentration of nitric acid, temperature and stirring rate, and decreased with increasing particle diameter and solid/liquid ratio. In 10M HNO3, at a temperature of 363K using 75µm particle diameter with solid/liquid ratio of 20g/L and stirring speed of 540 rpm, about 85.4% of alumina dissolved in 150 minutes. The activation energy, reaction order and Arrhenius constant calculated at the conditions above were 15.36 KJ/mol, 0.41, 0.586 s-1, respectively. The mechanism of dissolution of alumina was established to follow the shrinking core model for the surface chemical reaction mechanism. The XRD analysis of the post-leaching residue revealed the presence of microline and quartz. Hence, Amagunze clay has proved to be a viable alternative source for alumina production


Keywords: Alumina, Amagunze clay, Leaching, Kinetics, Nitric acid.




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