Silicates such as sodium silicate and bentonite are used in the LKAB pelletizing plant as dispersant and external binder, respectively. Sodium silicate is of great importance in the dephosphorizing flotation of magnetite fines and bentonite is used as glue in the balling of green pellets. However, the fundamental action of sodium silicate in the flotation and its effect on the subsequent balling procedure is still not clear.
Moreover, the binding mechanism of “glue” particles, i.e. bentonite, in green pellets is not well understood although the role of this additive is believed to be related to its swelling property in water. This property may result in a release of small bentonite platelets and an increase in viscosity of the water medium.
The main objective of this work was to improve the understanding of interactions between magnetite and silicates, namely to acquire better knowledge about the mechanisms involved in the sorption of dissolved silicate (water-glass) from aqueous solution onto iron oxide surfaces and to elucidate the interaction between bentonite and magnetite. Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy was utilized to monitor the sorption of dissolved silicate species as well as the orientation of bentonite platelets settling onto magnetite.