Recovery of Ni from a large excess of Al generated from spent hydrodesulfurization catalyst using picolylamine type chelating resin and complexane types of chemically modified chitosan

The total sulfuric acid leaching of hydrodesulfurization (HDS) catalyst yields an acidic solution rich in rare metals such as Mo, V, Co and Ni in addition to a large excess of Al. In previous work, for the purpose of separation and recovery of the rare metals from this solution, Mo and V were separated successfully using solvent extraction techniques leaving Ni and Co in the raffinate together with an appreciable amount of Al. The selective recovery of Ni from slightly acidic sulfate solution was attempted by means of ion exchange with Dowex XFS 4195 resin and complexane types of chemically modified chitosan. The batchwise experimental results showed good selectivity for Ni over Al for both chelating adsorbents. Fixed bed experiments using a packed column were also carried out. The breakthrough experimental results showed that a large amount of Al is immediately brokenthrough just after the initiation of the feed, while in the case of XFS 4195 resin, the breakthrough of Ni begins at 40 bed volumes (BV), suggesting that it is possible to purify Al free from Ni contamination by stopping the feed before 40 BV and, in the case of complexane types of chemically modified chitosan (DTPA-chitosan), the breakthrough of Ni begins at 5 BV. The loaded adsorbent can be eluted effectively with 0.5 M sulfuric acid and only a trace amount of Al is eluted while Ni is eluted concentrated to more than 10 times its concentration in the feed solution in the case of XFS 4195 resin and more than 23 times its concentration in the case of complexane types of chemically modified chitosan. These results indicate the successful separation and purification of small amounts of Ni from a large excess of Al with XFS 4195 resin and complexane types of chemically modified chitosan. (C) 1999 Published by Elsevier Science B.V. All rights reserved.