Magnetite nanoparticles (MNs, 10 nm) are ubiquitous in natural environment and are widely used in many applications (environmental remediation, catalysis, energy storage, and medical therapy, etc.) due to their physical and chemical properties (optical, magnetic, semiconductor and large specific surface). However, stoichiometric MNs are drastically sensitive to the presence of oxygen and pH condition. This thesis aimed to study the evolution of the stoichiometry of magnetite and to develop predictive model of magnetite solubility under various parameters (pH, redox potential, oxidation, recharge, overloading of dissolved Fe(II), and the presence of organic ligands) by combining laboratory experimentation, synchrotron spectroscopy and geochemical modeling.
Keywords: magnetite, maghemite, stoichiometry, solubility, solid-solution, geochemical speciation model, XMCD