Weak interaction induced selective separation of V/Mo/Co from spent hydrodesulfurization catalyst leaching solution: Mechanism and strategy

Spent hydrodesulfurization catalysts contain more than 10 similar to 25 wt% V, Mo and Co, which are not only hazardous materials, but also can be considered as valuable secondary resources. The complete separation of these complex critical metals by solvent extraction still needs to be improved. Here, a selective extraction route for the separation of V/Mo/Co is proposed based on the weak interaction differences between extractants and metal, which is realized by theoretical calculation and experimental verification. This process does not require pretreatment of N1923 and Cyanex272 (C272), thus reduced the consume of acid and base as well as generation of waste water. With the preliminary results of V/Mo, Co/Mo, and V/Co separation, the weak interaction between extractants and metal molecules was revealed by quantum chemical calculations quantitatively. The molecular charge distribution, surface electrostatic potential distribution (ESP) and the average local ionization energy (ALIE) shows the priority reactivity of the metal molecules as: H6V10O28 > H2Mo4O13 > H4V4O12 > H3VO4 > H2MoO4. The independent gradient model based on Hirshfeld partition (IGMH) show differences in the weak interaction forces as: N1923-V>C272-Mo > C272-V>N1923-Mo > C272-Co. The selective separation process of V/Mo/Co was designed with the guide of above results. The combined recovery of the three metals V, Mo and Co amounted to 83.88 %, 87.08 %, and 99.01 %, respectively. The whole route reduces 3.92 t sulfuric acid and 7.83 t sodium hydroxide per solid, and reduces 1.99 t carbon emissions compared to the conventional route.