Form of Aluminum(III) in Dilute Aqueous Solution

Abstract

<p> Using a potentiometric method on 10^-4M and 10^-5M Al(NO3)3 solutions at constant ionic strength (0.1 M KNO3) and temperature (25°C), titration curves were defined and examined with respect to three variables (total aluminum concentration, pH range, and time) in order to assess the reversibility of the aqueous system.</p> <p> Increasing pH titration interval decreased reversibility while increasing time interval led to a slight increase in reversibility. Decreasing the total aluminum concentration also slightly improved reversibility. Overall, the reversibility of the system was observed to be poor.</p> <p> Computer models were compared to experimental titration data in order to derive the speciation schemes which best fit the data. Polynuclear hydrolysis schemes fit the data best for the concentration levels as follows: Al^3+, Al(OH)4^-, and Al6(OH)15^3+ for 10^-5M Alt. Al^3+, Al(OH)4^-, and Al8(OH)20^4+ and/or Al13(OH)32^7+ for 10^-4M Alt.