Thermodynamic Modeling and Experimental Studies of Bayerite Precipitation from Aluminate Solution: Temperature and pH Effect

Abstract

<em>Bayerite is one of the phases of aluminum hydroxide which is precipitated by the carbonation of aluminate solutions obtained from sintered nepheline syenite leaching. In this study, the conditions for the bayerite formation were predicted by thermodynamic modeling of the carbonation process and the Bromley- Zemaitis model was used for this purpose. Carbonation experiments were carried out at pH 11 and the temperature range of 50- 90 °C based on the data obtained from thermodynamic modeling results. XRD analysis of products showed that bayerite was the predominant phase at all temperatures. SEM and LDS analysis indicated that the bayerite precipitates had uniform morphology and bimodal particle size distribution with mean particle size of 4.6 μm at 50 °C to 12.9 μm at 90 °C. It was found that the d₅₀ increased slowly at the precipitation temperature ranging from 80 to 90 °C, from 12.6 to 12.9 μm and the effect of temperature was on the shape of particles. XRF analysis of the products indicated that the amount of Al₂O₃ and SiO₂ in the bayerites decrease by increasing the temperature. According to the thermodynamic modeling data and experimental results, the temperature of 80 °C and pH 11 were determined as optimal conditions for bayerite precipitation. </em>