The effect of dopant’s valence (+III and +V) on the anion/cation uptake properties of antimony-doped tin dioxide

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Abstract Antimony is perhaps the most frequently used doping element of tin dioxide. Although antimony of different oxidation states have been used in the synthesis, the effect of dopant’s valence on ion exchange properties has not been investigated critically. In our study the valence of antimony had clear effects on the metal uptake properties of Sb-doped SnO2 materials. Extremely high Tc uptake (Kd > 100 000 mL g−1) on Sb(III)-doped material was observed in conditions under which Sb(V)-doped material did not show any Tc uptake. However, the Sb(V)-doped material showed good Ni2+ uptake properties (Kd up to 33 000 mL g−1), even at pH values below the material’s point of zero charge (pzc), while the Sb(III)-doped material showed Ni2+ uptake only at pH above its pzc. The cation uptake of Sb-doped SnO2 resembles typical weakly acidic cation exchanger character but the uptake of TcO4- does not follow a typical anion exchange pattern. Instead, we propose a sorption process related to redox reactions as the probable Tc uptake process.