Nickel catalysts used in various operations become spent after several cycles of use, for which a very simple and innovative process is developed at NML for recovery of nickel. The processing step consists of direct acid leaching in the presence of a promoter followed by impurity removal to produce nickel salt/metal. The novelty of the process is that it gives very high nickel recovery (99%) under the moderate conditions in presence of a little quantity of a promoter without which it is found to be very poor even at higher temperatures and acid concentration. High purity alumina is produced from the process as a part of the leached residue.
A smelting process is also developed for recovery of nickel as ferronickel from a variety of spent catalysts containing nickel in the range 8-25%. Various grades of ferronickel with a nickel content in the range of 20% to 80% have been produced.
National Metallurgical Laboratory (NML)
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