Recovery of vanadium and tungsten from waste selective catalytic reduction catalysts by K2CO3 roasting and water leaching followed by CaCl2 precipitation

Waste selective catalytic reduction (SCR) catalysts are potential environmental hazards. In this study, the recovery of vanadium and tungsten from waste SCR catalysts by K 2 CO 3 roasting and water leaching was investigated. The roasting and leaching conditions were optimized: the leaching efficiencies of vanadium and tungsten were 91.19% and 85.36%, respectively, when 18 equivalents of K 2 CO 3 were added to perform the roasting at 900 °C for 2 h, followed by leaching at 90 °C for 1 h. Notably, in the described conditions, the leaching rate of silicon was only 28.55%. Titanates, including K 2 Ti 6 O 13 and KTi 8 O 17 , were also produced. Si removal was achieved in 85% efficiency adjusting the pH to 9.5, and the Si impurity thus isolated was composed of amorphous Si. Tungsten and vanadium were precipitated using CaCl 2 . At pH 10 and following the addition of 0.10 mol of H 2 O 2 and 16 equivalents of CaCl 2 , the precipitating efficiencies of tungsten and vanadium were 96.89% and 99.65%, respectively. The overall yield of tungsten and vanadium was 82.71% and 90.87%, respectively. Graphic abstract