The application of zinc calcine as a neutralizing agent for the goethite process in zinc hydrometallurgy

• + 35 μm zinc calcine particles serve as the neutralizer of goethite process.
• Leach residue presented in fragments or porous structures
• The particle size of leach residue was far larger than that of the precipitate.
• Leach residue could be easily separated from the precipitate.

The industrial application of the goethite process has been restricted due to the low recovery of zinc and the great loss of lead and silver in zinc calcine with iron residues. In this study, we examined the properties of + 35 μm zinc calcine and assessed its feasibility for serving as a neutralizing agent in the goethite process. Due to an insoluble fragment or porous structure, the particle size of + 35 μm zinc calcine only decreased slightly at pH 2–3 and 80–90 °C. Large differences between iron precipitate and leach residues in the particle size and specific gravity favored the separation, as proven by using the terminal settling velocity deduced from Stroke's law. A combined analysis of environmental scanning electron microscopy, X-ray diffraction, energy dispersive spectrometry, and laser particle size analysis provided a fundamental understanding of the properties and behaviors of different particles. This study proved that in the goethite process, + 35 μm zinc calcine was a suitable neutralizing agent that could work efficiently and be separated easily from iron residues in the goethite process. Moreover, it ensured the high recovery of valuable metals such as zinc, lead, and silver.