Recovery of Nickel from Spent Industrial Catalysts Using Chelating Agents

Abstract

The extraction of nickel from a spent primary steam reformer catalyst from an ammonia plant was carried out by chelation using ethylenediaminetetraacetic acid (EDTA) as the chelating agent. Ni recovery was optimized by varying the particle size distribution of catalyst (pretreatment of spent catalyst), stirring speed, temperature (particularly in an autoclave, where temperatures ranging from 100 to 200 °C were used), EDTA concentration, and solid-to-liquid ratio. Approximately 95% Ni recovery was achieved in the Ni extraction carried out under hydrothermal conditions in an autoclave, at temperatures of 150 °C and higher, over a 4-h period. The resulting Ni−EDTA complex was then “dechelated” using a mineral acid (H2SO4 and HNO3), resulting in the formation of a nickel nitrate or sulfate solution and the precipitation of EDTA (about 97% of the initial weight of EDTA was recovered). However, the chelation performance of Ni was shown to decrease with every successive recovery of EDTA (in the case of dechelati...