A Study of Direct NH4VO3 Crystallization from Dilute V Solutions and the Effect of Impurities (Fe, Mn) on Crystallization

Abstract Industrial side streams, such as steel slag, can contain significant amounts of vanadium (V), and its recovery is important for their beneficial use. This study presents a simple approach for recovery of NH 4 VO 3 by direct crystallization from (NH 4 ) 2 CO 3 matrix without significant reagent additions and a V separation stage. This study investigated several factors (seed crystals, ultrasonic pretreatment, pH, vanadium concentration [V], Fe and Mn impurities) affecting direct NH 4 VO 3 crystallization from dilute V-containing ([V] 1.2–2.4 g/L) synthetic solutions. Besides [V], pH had a significant effect on crystallization, especially in the presence of a main impurity Fe. Fe precipitated rapidly with an amorphous structure during pH adjustment. At sufficiently low pH (< 6.8), NH 4 VO 3 crystallized slowly after Fe-containing precipitate formation. The total V recovery (R%) reached 81% but due to co-precipitation of V and Fe, V losses (2–35%) varied depending on the variation in Fe concentration. To minimize V loss, washing the Fe-containing precipitate with an alkaline solution was carried out with promising results (V R% 16–80%). The presence of Mn increased V R% despite almost complete co-precipitation with NH 4 VO 3 . The utilization of seed crystals accelerated the crystallization, but the effect of a three-minute ultrasonic pretreatment had an insignificant effect. The method was applied to authentic leachates ([V] 1.6 g/L) which showed comparable results (V R% 81%). Based on SEM-EDS, NH 4 VO 3 crystals contained only marginally Si. This study demonstrates the significant applicability of direct NH 4 VO 3 crystallization for dilute V solutions and offers a functional method from an industrial perspective.