Mechanism and Application of Seed-Induced Goethite Crystal Growth for Iron Removal from Rich-Zinc Solution

Abstract

The goethite residue generated from zinc hydrometallurgy is classified as hazardous solid waste with a large quantity, and it also leads to a high loss of zinc. The study was conducted on removing iron from FeSO4-ZnSO4 solution, employing seed-induced nucleation methods. The iron removal rate, as well as the structure, morphology, and elemental content of the residue, were analyzed using ICP, XRD, FT-IR, and SEM, and the existing state of zinc was investigated by combining step-by-step dissolution using hydrochloric acid, along with TEM and XPS analysis. Moreover, iron removal tests were carried out in industrial solutions to examine the effect of seeds and solution pH for zinc loss and residue yield. The results showed that the addition of seeds enhanced the iron removal rate by 3%, increased the residual iron grade by 6.39%, and reduced the amount of zinc loss by 29.55% in the simulated solution. The induction of seeds could avoid the excessive formation of nuclei, resulting in stable growth and high crystallinity. In addition, the zinc content in the residue was determined through surface adsorption and crystal internal embedding, and the zinc distribution on the surface was dense, while the total amount of zinc within the crystal was significantly higher. The test results in the industrial solution demonstrated that the introduction of seeds expanded the pH growth range for goethite formation, and under optimal conditions, it reduced zinc loss by 50.91 kg·t-1Fe (34.12%) and iron residue by 0.17 kg·t-1Fe (8.72%) per ton of iron removal.

Keywords: iron removal, crystal growth, homogeneous and heterogeneous nucleation, goethite process, zinc hydrometallurgy