Synthesis of VOSO 4 from Alkaline Vanadium(V) Solution by Chemical Reduction and Precipitation

Vanadyl sulfate (VOSO4) is a raw material for the manufacture of vanadium redox flow battery, which is an important alternative to lithium-ion batteries. Therefore, recovery of pure VOSO4 from the resources containing vanadium is important. Since vanadium ions have several oxidation states in aqueous solution, precise control of solution pH and potential is needed to recover VOSO4 from the solution containing V(V) ions. In this work, a procedure was developed to recover pure crystalline VOSO4 from the alkaline solution containing V(V) ions. This procedure consisted of chemical reduction, precipitation, and crystallization. First, V(V) ions were successfully reduced to V(IV) ions at ambient temperature by using Na2SO3 as a reducing agent under the optimal conditions: 5:1 for the molar ratio of Na2SO3 to V(V), solution of pH 4, 8 hrs and 400 rpm. Second, VO(OH)2 was precipitated from the V(IV) solution by controlling pH at 5 with NaOH at ambient temperature. Third, VOSO4 solids were recovered at 25°C by crystallization of the sulfuric acid solution of pH 1 after dissolving VO(OH)2 precipitates. Characterization by XRD and ICP verified that crystalline VOSO4 solids with purity higher than 99.9% were obtained by this procedure from the alkaline solution containing V(V) ions. The procedure proposed in this work is simple and effective for the recovery of pure VOSO4 solids from pure V(V) solutions.