![]() There are a few relevant studies on direct magnetite–silica interaction using AFM. However, the influence of calcium ions, commonly found in natural and process waters, on the interaction between magnetite and silica particles is scant in the literature, although it is well known that calcium ions can easily adsorb at negatively charged surface sites. A similar condensation reaction might also appear between magnetite and silica (SiO 2) particles. ![]() It is known that silicate anions adsorb onto magnetite even at alkaline solution (7 < pH < 9), although the magnetite surface is negatively charged, indicating a condensation reaction between silicate and magnetite. Interaction between natural magnetite and soluble silicate is of importance for mineral processing in processes such as flotation, dispersion, and agglomeration of iron ore concentrate. Synthetic nanomagnetite (Fe 3O 4) particles with spherical shapes and known chemical composition can also be used to model natural magnetite when natural particles cannot be used due to their larger size (smaller surface area per gram) and complex chemical composition. Iron oxide nanoparticles have attracted significant research interest due to their superparamagnetic properties and high potential to be used in biomedicine. Knowledge about the forces acting between particles in aqueous solutions is of fundamental importance in various applications, such as mineral processing, biomedicine, nanoelectronics, and adhesives. The measurement of force interactions between particles in predefined conditions was shown to significantly contribute to particle dispersion and adhesion studies. , has been proven to be a good technique for measuring interaction forces in aqueous medium for a variety of materials. ![]() A comparison of measured and calculated adhesion forces with a few contact mechanics models demonstrated an important impact of nanomagnetite layer nanoroughness.Ītomic force microscopy (AFM) using the colloidal probe technique, introduced by Ducker et al. It was shown that an increase of Ca 2+ concentration from 1 to 3.3 mM led to a less pronounced decrease of adhesion force with increasing pH. However, contributions from non-DLVO forces should also be considered. The good fitting of experimental data to the DLVO model and simulations supported this conclusion. The interaction forces on approach were due to van der Waals and electrical double-layer forces. The repulsion between nanomagnetite and silica was observed at alkaline pH and 1 mM Ca 2+ concentration, but no repulsive forces were observed at 3 mM Ca 2+ concentration. This study showed that the qualitative changes of the interaction forces with pH and Ca 2+ concentrations were consistent with the results from zeta-potential measurements. In this work, the interaction between nanomagnetite and silica particles was measured with AFM in aqueous Ca 2+ solution at different pH levels. In directly probing nanomagnetite–silica interaction, atomic force microscopy (AFM) using the colloidal probe technique has proven to be a suitable tool. Dispersion and aggregation of nanomagnetite (Fe 3O 4) and silica (SiO 2) particles are of high importance in various applications, such as biomedicine, nanoelectronics, drug delivery, flotation, and pelletization of iron ore.
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