Résumé
Ion foam flotation (an industrial method) is based on the extraction and separation of ions by foams. The classical ion flotation process make use of ionic foaming agents (surfactants) to extract selectively ions by electrostatics interactions. To transform this process into pure non-electrostatic, superchaotropicity could become a driving force in this system. Superchaotropicity is the general property of low charge density nanometric size ions (nano-ions), which can adsorb strongly onto neutral hydrated surfaces. For example, the large size and low charge density of polyoxometalates (POMs), compared to classical ions, are responsible for this peculiar superchaotropic behavior. The objective of this work was to demonstrate the feasibility of an ion flotation process whose driving force and selectivity would be due to the affinity of superchaotropic nanoions for uncharged hydrated surfaces, i.e. a non ionic surfactant foam in a sort of superchaotropic flotation. For this work Molybdenum was chosen for the importance of finding new simple, selective and eco-friendly extraction methods to prevent pollution in the environment in mining industry and because the speciation of molybdate shows in acidic pH the formation of large polyoxo species such as the Mo36 which has a low charge density and for which we expect a strong superchaotropic property. In this regard, we apply the following chemical system composed of: molybdate and polyoxyethylene (10) oleyl ether (BrijO10®) in aqueous solution to investigate the superchaotropic behavior of polyoxomolybdate species. The extraction of Mo with foam was studied as a function of pH and Mo concentration. The adsorption of molybdate species on BrijO10 micelle was studied by SAXS experiment. The speciation of molybdate in the presence of BrijO10 was investigated by Raman spectroscopy.