Targeted conversion of Ni in electroplating sludge to nickel ferrite nanomaterial with stable lithium storage performance

The recovery of heavy metals from industrial solid waste is of great significance for simultaneously alleviating heavy metal pollution and recycling valuable metal resources. However, the complex compositions of the multiple metallic electroplating waste severely limit the selective recovery of metal resources such as nickel. In this study, a kind of nickel-laden electroplating sludge was taken as an example and the Ni in it was targetedly converted into highly valuable NiFe2O4 (nickel ferrite) nanomaterials via a regulator assisted hydrothermal acid-washing strategy, eventually leading to selective extraction of Ni and Ca from the sludge. Sodium carbonate was the best regulator for the formation of NiFe2O4, and under the optimal conditions, the extraction rates of Ni and Ca are 96.70 % and 99.66 %, respectively. The as-prepared NiFe2O4 nanoparticles exhibited stable electrochemical Li-storage performances, such as a reversible capacity of approximate 316.94 mA h/g at 0.5 A/g and a long cycle life exceeding 100 cycles, with nearly no capacity decay. This work provides a facile and sustainable approach for targeted conversion of heavy metals in industrial solid waste to high-valuable functional materials and selective recovery of heavy metals from multi-metal solid wastes.