Removal of Vand Fe from spent denitrification catalyst by using oxalic acid: Study of dissolution kinetics and toxicity

The selective dissolution of V and Fe from spent denitrification catalyst (SDC) with oxalic acid was investigated to minimise their environmental effects. The dissolution kinetics of different elements from SDC by using 0.1-1.5 mol L-1 oxalic acid concentration was studied at 60 degrees C-90 degrees C. V and Fe were preferentially released (65% and 81%) compared with Al, Ti and W within 5 min due to the redox reactions of oxalic acid. The dissolved fractions of Fe, V, Al, Wand Ti increased with the increase of oxalic acid concentration and reaction temperature. The dissolution kinetic experiments were analysed and controlled diffusion with n < 0.5 according to the Avrami dissolve reaction model (R-2 > 0.92). The Arrhenius parameters of the E-a values of Ti, W, V, Fe and Al from SDC with oxalic acid were 30, 26, 20, 19 and 11 kJ mol(-1), respectively. The obtained Avrami equation of V and Fe was successfully used to predict their leaching behaviour in oxalic acid. Toxicity characteristic leaching procedure revealed that the toxicity risk of Vand Fe metals from SDC after leaching with oxalic acid decreased to below 5 mg kg(-1) residua. Overall, the leaching residua by oxalic acid indicated its safety for the environment. (C) 2021, Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.

Automated summary

Selective dissolution of V and Fe from spent denitrification catalyst using oxalic acid can effectively reduce the environmental impact, with dissolution kinetics controlled by redox reactions and diffusion.