Quartz crystal microbalance as a tool for scale deposition monitoring in Bayer process conditions

This paper describes the study of bayerite or gibbsite scale formation and growth from supersaturated sodium aluminate solutions using a quartz crystal microbalance. Analysis of frequency vs time curves and scanning electron microscopy images allowed us to propose a surface nucleation mechanism that leads to cementation of particles produced by catastrophic secondary nucleation. We also highlighted the influence of the filtration of the supersaturated sodium aluminate solution step on the scale nucleation kinetics. It was observed that use of filter with porosity below 2.5 μm delays the formation of scale.

► Use of quartz crystal microbalance in caustic supersaturated media. ► Nucleation by means of catastrophic secondary nucleation. ► Decreasing filter pore diameter increases induction time.