Recycling of spent catalysts used in sulfuric acid production

Abstract

This study focuses on support separation and precipitation of key elements, mainly vanadium, from spent catalysts used in sulfuric acid production. This vanadium recycling process is of particular importance because of the significant number of spent catalysts and their considerable economic value, as well as environmental issues. The paper describes a process for recovering vanadium from spent catalysts, using the acid leaching method (H2SO4, HNO3) with or without additives (H2O2), or simply with H2O. The leaching process was comprehensively monitored at all stages by mass balance analysis in the solution and solid phases, as well as by X-ray diffraction analysis. Leaching at 50 °C for 2 hours with H2SO4 (0.5 M) and H2O2 (0.5 M), with a solid-liquid ratio (S/L) of 1:25, with a leaching efficiency of 90.51% by weight of the vanadium present in the spent catalyst. Subsequent precipitation of the vanadium phases by the addition of NH3(aq) at pH = 7 into the solution using HNO3 with H2O2 resulted in an overall vanadium recovery of 36.31 wt.%. In contrast, leaching with water alone at room temperature dissolved 68.53% by weight of vanadium, achieving an overall yield of 34.39% by weight in the final solid. In particular, the choice of precipitating agent significantly influences the composition of the resulting solid