PURITY UPGRADE OF AMMONIUM PERRHENATE SOLUTIONS IN RESPECT OF MOLYBDENUM (VI) AT SORPTION RECOVERY OF RHENIUM (VII) FROM SOLUTIONS CONTAINING MOLYBDENUM (VI)

Abstract

The study covers the method of additional cleaning of ammonium perrhenate desorbates from molybdenum through sorption recovery of rhenium from Mo-containing solutions with Purolite A170 and A172 weak base anion exchange resins. The dependence of Re(VII) and Mo(VI) sorption using these resins on solution pH was studied under static conditions with the 1 M (NH 4 ) 2 SO 4 solution. It was found that the pH range at which the resins retain the ability of Re(VII) sorption extends to a weak-alkaline area. A significant decrease in Re(VII) adsorption begins when pH exceeds 7,5 Mo(VI) capacity of the resins decreases significantly when solution pH exceeds 5,0, and both anion exchange resins practically stop molybdenum sorption at above pH ~ 7,0. Reduction of Mo(VI) content in rhenium desorbates obtained in sorption recovery of Re(VII) from Mo-containing solutions with weak base anion exchange resins can be achieved as follows. First, major quantity of adsorbed Mo(VI) is desorbed from the loaded resin by ammonium sulfate solution when stirring the mixture and keeping pH constant in the 7,0–7,5 range by dosing the ammonia solution. Then the resin is separated from the Mo(VI)-containing ammonia solution, washed with water, and Re(VII) is desorbed by the ammonia solution in dynamic conditions. The proposed method was verified with anion exchangers loaded in sorption from the model solution with the following composition, g/L: 98 H 2 SO 4 , 4 Mo(VI), 0,5 Re(VII). It was shown that resin treatment with the ammonium sulfate solution removes at least 90 % of adsorbed molybdenum. A ratio of Re(VII) to Mo(VI) concentrations in ammonium perrhenate desorbates increases by 11 times with Purolite A170 resin, and by 20 times with Purolite A172 resin compared to the results obtained without an additional Mo(VI) washing. Re(VII) losses (reversible) with the Mo-containing desorbate are below 5,2 % of the adsorbed Re(VII) amount.