Compared
to the traditional ammonia salt method, hydrolysis for
the precipitation of vanadium is a clean method that does not produce
ammonia-bearing wastewater. In this study, a novel strategy of speedy
acidification of static sodium vanadate (NaVO3) solution
and vanadium slag leaching solution for vanadium hydrolysis was proposed
to 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 hydrolyzed
in 30 min at a higher pH value of 2.4 and a lower temperature of 80
°C, reaching the precipitation efficiency as high as 99%. Compared
to the conventional hydrolysis method, the new method could shorten
the reaction time, decrease the dosage of acid, and save energy. The
hydrolysis mechanism was studied by in situ focused-beam reflectance
measurement and particle video microscopy, indicating that a great
amount 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 of
its autogenous crystal seed which resulted in red cake precipitation.
In this way, the induced nucleation time of hydrolysis was shortened
thereby hydrolysis and vanadium precipitation were promoted. The operation
process was simple, and acid consumption, reaction time, reaction
temperature, and production cost were effectively reduced, realizing
high-efficiency vanadium precipitation. Finally, the kinetics of the
hydrolysis process was investigated, and the chemical reaction was
the rate-determining step and the apparent activation energy was found
to be 50.96 kJ/mol.