Nanostructured NiO derived from spent nickel catalyst as an efficient photocatalyst: Characterization, performance, and kinetic study

This study aimed to recover and regenerate nanostructured nickel oxide (NiO) from a spent nickel catalyst (SNC) using the simple and economical hydrometallurgical method. The experiment was carried out by exploring Ni leaching kinetic models, such as the shrinking-core model (SCM), logarithmic rate law, and the Avrami model. HCl was used as a lixiviant, achieving a high 99% Ni leaching efficiency (LE) at a solid/liquid ratio of 100 g/L and temperature of 70℃ The suitable mechanism for the Ni leaching from SNC using HCl solution is the Avrami model. The nanostructured NiO was successfully obtained by precipitation and sintering. Furthermore, XRD, SEM-EDX, TEM, Raman spectroscopy, and surface area analysis confirmed the formation of SNC-derived nanostructured-NiO (NiO-Cat) with needle-like nanosized particle size and a surface area of 77.2 m2/g. The NiO-Cat was examined for UV-irradiated photo-Fenton-like degradation activity on synthetic cationic and anionic dyes, including rhodamine B (RhB), methylene blue (MB), acid orange 7 (AO7), and methyl orange (MO), which showed degradation efficiency of 96%, 98%, 93%, and 83%, respectively, after 120 min of reaction. The overall process is economically and environmentally attractive. Meanwhile, the leaching and photocatalysis data can be further developed in the industry for equipment design.