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Abstract

The dissolution kinetics of alumina in aqueous solution was studied in batch and continuous systems. Data were correlated by the kinetic equation C(t) = 1 − exp(−ktα). The parameter k was a function of temperature and acid concentration, while the parameter α remained constant.

The temperature variation of k was accurately represented by an Arrhenius-type equation with a temperature coefficient, 18,200 kJ/kmol. The data obtained in batch experiments were free of mass transport and mixing effects. Adsorption-desorption equilibrium of hydrogen ion at the alumina surface was observed. The results supported postulated reactions reported in the literature for alumina dissolution. The basic features of the mechanism include hydration of the aluminum oxide surface, hydrogen ion adsorption followed by reaction to form a positively charged surface species [Al(OH)2+], formation of stable surface species [AlOOH and (Al(OH)2)2 SO4], and desorption of products.