Assessment of the use potential of iron ore tailings in the manufacture of ceramic tiles : from tailings-dams to ‘‘brown porcelain”.

Abstract

Nearly half of the total iron ore volume extracted in mining operations is rejected as tailings and disposed of in containment dams that are liable for considerable environmental impact and human hazard in case of breaching. This work aims to expand the usage possibilities of iron ore tailings and help mitigate the negative impact of tailings-dams without sacrificing the opportunities provided by mining. Materials were collected from four tailings-dams, subjected to a dry separation procedure and characterized (particle size and morphology, chemical and mineralogical composition). Besides the recovered iron ore concentrate, two other powder fractions were produced (“clay” and “sand” fractions). The sands showed the greatest uniformity (particle size and shape, mineralogy and chemical composition) and may find use as aggregates in a variety of applications. This work shows that the clays can be used on their own in the production of ceramic tiles. They present adequate plasticity and dry strength, and develop mullite and glass upon firing, showing a rather amenable processing behaviour suitable for both artisanal and full-fledged industrial production. The resulting tiles are dimensionally homogeneous and very compact (vitrified products, classified in groups BIa, BIb or BIIa), with high mechanical strength. Either industrialised or artisanal, these materials can be used in the production of “brown porcelain” tiles and ware, showing a very appealing dark brown lustre.