Tuning the Nucleation Rates for High-Efficiency Hydrolysis of Sodium Vanadate Solution

Comparedto the traditional ammonia salt method, hydrolysis forthe precipitation of vanadium is a clean method that does not produceammonia-bearing wastewater. In this study, a novel strategy of speedyacidification of static sodium vanadate (NaVO3) solutionand vanadium slag leaching solution for vanadium hydrolysis was proposedto achieve high-efficiency hydrolysis by tuning the nucleation rates.The results of the parameter experiments showed that NaVO3 solution could be rapidly nucleated within 10 s and completely hydrolyzedin 30 min at a higher pH value of 2.4 and a lower temperature of 80 & DEG;C, reaching the precipitation efficiency as high as 99%. Comparedto the conventional hydrolysis method, the new method could shortenthe reaction time, decrease the dosage of acid, and save energy. Thehydrolysis mechanism was studied by in situ focused-beam reflectancemeasurement and particle video microscopy, indicating that a greatamount of reactant was produced because of rapid reaction when H2SO4 was all poured into the static solution. Subsequently,local high supersaturation of the reactant led to the formation ofits autogenous crystal seed which resulted in red cake precipitation.In this way, the induced nucleation time of hydrolysis was shortenedthereby hydrolysis and vanadium precipitation were promoted. The operationprocess was simple, and acid consumption, reaction time, reactiontemperature, and production cost were effectively reduced, realizinghigh-efficiency vanadium precipitation. Finally, the kinetics of thehydrolysis process was investigated, and the chemical reaction wasthe rate-determining step and the apparent activation energy was foundto be 50.96 kJ/mol.