Release kinetics of vanadium from vanadium titano-magnetite: The effects of pH, dissolved oxygen, temperature and foreign ions

As part of a broader study of the environmental geochemistry behavior of vanadium (V), the release kinetics of V from the dissolution of natural vanadium titano-magnetite under environmentally relevant conditions was investigated. In both the acidic and basic domains, the V release rate was found to be proportional to fractional powers of hydrogen ion and dissolved oxygen activities. The dependence of the rate on dissolved oxygen can also be described in terms of the Langmuir adsorption model. The empirical rate equation is given by: r = k' alpha(H+)(alpha) K alpha(O-2)1 + k alpha(O-2) where, alpha = 0.099-0.265, k' = 3.2 x 10(-6)-1.7 x 10(-5), K = 2.7 x 10(4)-3.9 x 10(4) mol/L in acid solution (pH4.1), and alpha = -0.494 -(-0.527), k' = 2.0 x 10(4)-2.5 x 10(-11), and K = 4.1 x 10(3)-6.5 x 10(3) mol/L in basic solution (pH 8.8) at 20 degrees C. Based on the effect of temperature on the release rate of V, the activation energies ofminerals at pH 8.8were determined to be 148-235 kJ/mol, suggesting that the dissolution of vanadiumtitano-magnetite is a surface-controlled process. The presence of Na+, Ca2+, Mg2+, K+, NO3-, Cl-, SO42- and CO32- was found to accelerate the V release rates. This study improves the understanding of both the V pollution risk in somemine areas and the fate of V in the environment. (c) 2017 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.