Understanding the enhanced removal of Bi(III) using modified crystalline antimonic acids: creation of a transitional pyrochlore-type structure and the Sb(V)-Bi(III) interaction behaviors

Abstract

The submicro-sized crystalline antimonic acids (C-SbA) with a transitional pyrochlore-type structure were synthesized through a facile thermolysis method and used as a precipitator for efficient removal of bismuth (Bi) ions from strong acid aqueous solution. The compositions, phases, morphologies and dissolution behaviors of C-SbA materials after thermolysis at different temperatures were analyzed and the effects of temperature, initial concentration, and competing ions on the interaction behaviors between C-SbA and Bi(III) were also investigated. The results show that the water-insoluble C-SbA become considerably dissolvable after heating at ∼350 °C due to the introduction of the mixed valence-state (III, V) and plenty of atomic vacancies. The Bi(III) removal capacity is as large as 250 mg g−1 by the C-SbA powders heated at 350 °C in a 2.0 g L−1 of Bi(III) and 2.0 mol L−1 of H2SO4 solution at 60 °C and the removal efficiency of Bi(III) is over 99%. The removal kinetics can be described by the pseudo-second-order kinetic model. It is found that Bi(III) ions are removed via the co-precipitation reaction between Bi(III) and Sb(V) and the formed bismuth antimonate (Bi3SbO7) nanocrystals are readily recovered together with C-SbA powders because they are inclined to nucleate on the surface of C-SbA particles. This study shows the promising prospect for the application of modified C-SbA in eliminating the group V elements in the copper electrolytes.