An investigation of bioleaching and valorization of hazardous zinc plant purification residue using Aspergillus niger

Solid waste deposits from mineralogical activities contain a significant amount of heavy metals. Hot filter cake is continuously produced and landfilled from zinc hydrometallurgical plants which is a potentially hazardous waste and an important secondary resource. Bioleaching is an eco-friendly and innovative method for recycling metals from this hazardous waste stream. In this study, biogenic reagents produced by Aspergillus niger followed by precipitation were employed to selectively recover zinc and cobalt in the forms of pure solutions, and manganese as a precipitate from the HFC. In the first step, 98%, 100%, and 99% of Zn, Co, and Mn were leached using a pulp density of 10 g L-1 by Aspergillus niger in a glucose medium. Then, Co and Mn were co-precipitated using 10 mol L-1 of NaOH at a pH of 14. Subsequently, 96.87% of Co was selectively leached from the residue with ammonium solution for 5 h, with the solid to liquid ratio of 10 g L-1, the pH of 8, and at 25 degrees C. At the end of the process, 94.63% of Mn was recovered in the forms of MnO and Mn3O4 as some added-value products. [Graphics] .

Automated summary

This study successfully recovered zinc, cobalt, and manganese from hazardous waste using biogenic reagents produced by Aspergillus niger.