Flotation of molybdate oxyanions in dilute solutions .2. Selective separation from phosphates, arsenates and silicates

Adsorbing colloid flotation was found to be an efficient method for selective separation of phosphates or silicates from aqueous solutions of molybdate oxyanions (binary mixtures); tertiary and quaternary mixtures of molybdates and arsenate, phosphate and silicate anions have been also separated effectively. The main parameters affecting this process, namely the concentrations of Fe(III) (used as co-precipitant), dodecylamine (used as surfactant or collector), molybdates, phosphates, arsenates and silicates, the pH of the solutions studied, as well as the addition of foreign ions (Cl- and SO42-) were investigated in detail. It was found that over 95% of the impurities (usually 15 mg/l each) can be selectively removed from aqueous solutions containing molybdates (at concentrations exceeding 200 mg Mo/l), when the solution pH was around 9 (+/-0.2), while the simultaneous co-removal (i.e. loss) of molybdates was around 20%, almost regardless of the initial concentrations of the other co-existing components.