Recycling of industrial goethite wastes by thermal treatment

摘要

The solid ferrous residues called Paragoethite (P-Goethite), generated by one of the processes for the production of electrolytic zinc, are roasted and then reduced in order to transform ferric oxides into elemental iron. The reduction is performed at low temperature to prevent zinc being reduced and evaporated. The roasted, reduced material is then subjected to low intensity magnetic separation which gives rise to two products: magnetic and non-magnetic, enriched in iron and zinc, respectively. The process, already applied on other materials, is applied for the first time on P-Goethite in order to utilise it in iron making. This would liberate extensive areas now required as waste dumps that also constitute a possible environmental hazard due to the presence of harmful elements like cadmium and arsenic, in addition to lead and zinc. The concentration of zinc and lead in the magnetic fraction still prevents the use of P-Goethite in iron making, but the process could be improved enhancing the ferric oxide conversion and using magnetic separators more efficient for fine particles. Before running the thermal tests on the P-Goethite, the material was thoroughly characterised by means of chemical, size, petrographic and thermal analyses.