Removal of silicon from vanadate solution using ion exchange and sodium alumino-silicate precipitation

The removal of silicon from vanadate solution using ion exchange and precipitation was studied. It was found that vanadium (V) with silicon can form heteropoly acids in the pH range of 2–13, and the composition of the heteropoly acids depends not only on the pH value but also on the vanadium (V) concentration. The vanadium and silicon were adsorbed by the resin D314 in the V/Si mol ratio of 1.2 from the feed solution containing V2O5 2.73 g/l and SiO2 3.76 g/l at pH 2.11. They were eluted from the loaded resin by 2 M NaOH in the same proportion. When the eluate pH was adjusted from 13.5 to 3.5, the V/Si mol ratio increased to 3.4 because of the precipitation of (NaVO3)n·(H2SiO3)m. Subsequent experiments found that the precipitation of sodium alumino-silicate was more effective and selective to remove silicon from the eluate. The removal of silicon was 97.3%, and the loss of vanadium was 1.6% by adding 1.1 times stoichiometry of AlCl3 at pH 8.0 and 90 °C for 1 h.

Research highlights
► Vanadium (V) with silicon can form heteropoly acids in the pH range of 2–13, and the composition of the heteropoly acids depends not only on the pH value but also on the vanadium (V) concentration.
► Vanadium (V) can condense with silicon to form the heteropoly acids provided that the bond of V―O―V can form in the solution.
► The use of sodium aluminosilicate precipitation is an effective and adequate method to remove silicon from the solution containing vanadium (V) solution.