Parametric Characterization of Tungsten Leaching in Concentrates of Spanish Origin

Tungsten leaching kinetics were investigated for three concentrates of Spanish origin containing wolframite, scheelite and mixed mineral phases under their respective optimum processing conditions. Experimental conversion data were analysed using classical shrinking-core equations and complementary biparametric models to identify the rate-controlling mechanisms governing tungsten dissolution. Among the mechanistic models evaluated, the Ginstling–Brounshtein equation consistently provided the best description of the experimental results for all concentrates, indicating that the overall leaching rate is controlled by a coupled reaction–diffusion mechanism in which internal diffusional resistance becomes increasingly important as dissolution proceeds. For scheelite, the apparent activation energy obtained from the Arrhenius analysis (−11.66 kJ mol−1) supports this interpretation, reflecting the macroscopic response of an evolving reaction–diffusion system rather than the intrinsic activation barrier of an elementary chemical reaction. Biparametric models slightly improved the statistical fit, with the Elovich equation providing the best representation for scheelite and the activated mixed concentrate, whereas Gompertz and Avrami models performed similarly for wolframite. The combined application of mechanistic and empirical kinetic models provides a robust framework for comparing the leaching behaviour of different tungsten concentrates and for supporting the design and optimisation of hydrometallurgical processes.