Nickel recycling through bioleaching of a Ni/Al2O3 commercial catalyst

Bioleaching studies were carried out on a commercial nickel-based reforming catalyst using two acidophilic bacteria (Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans) under several types of bioleaching mode (one-step, two-step and spent medium-step) and catalyst pretreatment (with and without reduction). The highest percentage of nickel extraction was achieved using A. thiooxidans under spent medium-step (94.4 +/- 0.1%). The percentage of nickel extracted was constant (85.6 +/- 3.9%) up to a pulp density of 5% w v(-1), and it decreased at higher pulp densities due to acid depletion. In order to assess the potential reuse of the recovered metal, the nickel solution obtained by bioleaching was recycled by using it to prepare a new Ni/Al2O3 catalyst by impregnation of a commercial alumina support. Characterization of the catalyst prepared from recycled nickel showed that it had a high purity along with a suitable texture and metallic dispersion. Indeed, the activity of the new catalyst in the dry reforming of methane provided a high conversion of methane (99%) with good stability over time under the experimental conditions employed.