Scale Formation During the Bayer Process and a Potential Prevention Strategy

Five samples of scales collected from various locations in a high-temperature Bayer process plant were characterized via X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray spectroscopy, and X-ray photoelectron spectroscopy analyses. Then, a method for preventing the formation of scales was proposed. Results showed that the minerals in scales, such as hematite, hydroxyapatite, and sodium aluminate silicate hydrate, are arranged in a layered structure. The difference in arrangement resulted in variations in physical properties, including thickness and hardness. Hematite was facilitated to form thicker layers than magnetite during the scale formation process. Therefore, converting hematite into magnetite by adding a reductant (e.g., glycerol) during Bayer digestion is a feasible strategy for preventing the formation of scales.