Recycling of Ni from leached spent catalyst residue by H2SO4 leaching and solvent extraction: leaching kinetics, purification and product preparation

Spent hydrodesulfurization catalyst (HDS) is considered as the important secondary resource for Mo and Ni. The separation of Mo from HDS was usually conducted by soda roasting and water leaching, while Ni remained in the leached residue. This study proposed a method to recover Ni from leached residue by H₂SO₄ leaching and solvent extraction, and Ni was recycled in the form of NiO. The results showed that the optimum Ni leaching process were conducted using 30% H₂SO₄ with liquid–solid ratio of 10 at 70 ℃ for 120 min. The optimal extraction was accomplished using 30% di-(2-ethylhexyl) phosphate (P204) saponification at pH value 6.0 with organic/aqueous (O/A ratio) of 1 for 1 min. Additionally, 20% H₂SO₄ could be used to strip Ni from organic phase with O/A ratio of 10. Finally, NiSO₄ was calcined at 850 ℃ for 1.0 h to obtain NiO. The Ni leaching kinetic analysis showed that the activation energy of Ni leaching process was 16.10 kJ/mol, which was accorded with the shrinkage unreacted kernel model controlled by internal diffusion. This study provided an alternative method to recycle Ni and given a deeper insight to the leaching mechanism during H₂SO₄ leaching Ni from spent catalyst.

Graphical abstract