Recovery of nickel and molybdate from ammoniacal leach liquor of spent hydrodesulfurization catalyst using LIX84 extraction

Ammonia leaching can achieve selective recovery of nickel and molybdenum without aluminum extraction from spent hydrodesulfurization catalyst. In this study, a method for selective nickel extraction by LIX84 from ammoniacal leach liquor is proposed. After a two-stage countercurrent extraction, 99.977% Ni was extracted, while 0.096% Mo, 0.431% Al and 2.812% P were co-extracted under LIX84 concentration of 5%, initial pH value of 11.5, and phase ratio (O/A) of 2/1.1. Then a 0.1 mol/L oxalic acid (initial pH 1.36) was used to strip Ni-loaded organic phase under the phase ratio (O/A) of 0.5. 99.91% nickel in organic phase can be stripped into aqueous phase, while 91.16% nickel in aqueous phase can be precipitated as pure nickel oxalate dihydrate, and the oxalic acid solution containing dissolved nickel can be returned to the next stripping process to achieve nickel recovery. Subsequently, ammonium molybdate product can be obtained from molybdenum-containing raffinate by evaporation and crystallization after impurity removal. In addition, thermodynamic calculations show that the nickel extraction process by LIX84 from ammoniacal solution is an endothermic reaction. The present approach may efficiently be applied to recovery of molybdenum and nickel from spent hydrodesulfurization catalyst as per the proposed schematic flow-sheet.

Automated summary

The study proposes a method to selectively recover nickel and molybdenum from spent hydrodesulfurization catalyst using ammonia leaching, achieving efficient nickel extraction and recovery. Results show that nickel and molybdenum can be effectively separated and extracted from the spent catalyst through countercurrent extraction and oxalic acid stripping.