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 se lective separation of phosphates or silicates from aqueous solutions o f molybdate oxyanions (binary mixtures); tertiary and quaternary mixtu res of molybdates and arsenate, phosphate and silicate anions have bee n also separated effectively. The main parameters affecting this proce ss, namely the concentrations of Fe(III) (used as co-precipitant), dod ecylamine (used as surfactant or collector), molybdates, phosphates, a rsenates and silicates, the pH of the solutions studied, as well as th e 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 molybdate s (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 mo lybdates was around 20%, almost regardless of the initial concentratio ns of the other co-existing components.