Separation of vanadium, tungsten and molybdenum from spent SCR catalysts solution by solvent extraction with primary amine N1923.

The large accumulation of spent selective catalytic reduction (SCR) catalysts cause waste of resources and environmental pollution. In this study, an efficient method is proposed to separate vanadium (V), molybdenum (Mo), and tungsten (W) from the leachate of hydrometallurgical treated spent SCR catalysts. First, V and W could be preferentially extracted by acidified primary amine N1923 and left Mo in the raffinate, then V and W were stripped selectively by sulfur acid and ammonia solution, respectively, leading to the separation of V, Mo, and W. Optimized experimental conditions were achieved as Initial pH of 6.7, phase ratio O/A of 1, contact time of 4 min and the concentration of primary amine N1923 was 10 % (v/v), under which V and W were extracted as high as 99.91 % and 96.86 % for the two-stage counter-current extraction, respectively, limiting Mo co-extraction to 5.84 %. The stripping ratio of V and W were up to 95.34 % and 95.50 % with sulfuric acid and ammonia, respectively and the organic phase was remained to recycle. The mechanism and process of extraction were analyzed using the slope method and the FT-IR spectra. In addition, the equations for the stripping of V and W with sulfuric acid and ammonia were deducted. Compared to traditional solvent extraction and chemical precipitation, this one-step-extraction-two-steps-stripping process shorten steps and is more efficient to separate three metals ions of V, Mo and W.