Recovery of magnesium sulfate from a zinc tailing

The tailing from zinc mining (Willemitic ore), located in southeastern Brazil was used for the research. The form of zinc in nature is found in sulfides that has an association with other elements, such as lead, iron and silver. The minerals from which zinc is extracted are sphalerite (sulfides), smithsonite (carbonate), hemimorphite (silicate) and franklinite (oxide), and its main minerals found in Brazil are calamine, willemite and sphalerite. This tailing was characterized in order to investigate two routes for its recovery, pyrometallurgical and hydrometallurgical. The work aims to evaluate the possible applications of the waste and its return to the economic cycle. The investigation of new methods for the recovery and reuse of materials from waste are alternatives to be explored.

The reuse is a way to recover elements with added values for consumption, which can be used in the form of products or in agriculture. It is aimed to avoid the extraction of some elements with the improvement of recovery techniques from a waste that is destined only for disposal; for example, the tailing to obtain zinc from the flotation process, in which secondary minerals, such as magnesium, can be found. The use of the hydrometallurgical route that aims at the best conditions for the recovery of magnesium sulfate from acid leaching is an alternative to be applied. Therefore, chemical analysis is performed for both quantitative and qualitative of these elements. In leaching, equipment such as X-ray diffraction (XRD) is used to know the predominant phases formed in the leaching reaction, Scanning electron microscopy (SEM) to ascertain the behavior of the material from a microregion accompanied by Dispersive Energy Spectroscopy (EDS); ion chromatography (CI) and Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) for the characterization of the liquor acquired after leaching to perform mass balance of the process as a whole.

Techniques accompanied by purification steps such as precipitation and cementation are routes explored to obtain a product in which it can be used for agricultural purposes.