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Nowadays, Nexa Resources (ex-Votorantim Metais) operates two zinc mines in Brazil, represented by the Vazante unit in Vazante - MG and the Morro Agudo unit in Paracatu - MG. The present study was carried out at the Vazante unit, where zinc concentrate is produced from a silicate ore called Willemite (Zn2SiO4) through froth flotation processes. The two main objectives of the study were the determination of the maximum zinc recovery that could be obtained in flotation bench tests with specific controlled conditions and the mineral characterization of the tailings generated, using a SEM/EDS (scanning electron microscope with energy dispersive x-ray spectroscopy) with MLA (mineral liberation analyzer). The flotation results showed a maximum recovery of 91.91 % with 1.68 % of zinc in the tailings after an eleven-minute flotation. Considering the mean results of all the tests, the maximum zinc recovery obtained was 91.07 % with 1.75 % zinc grade in the tailings. Mineral characterization analysis showed that zinc minerals besides Willemite, such as Gahnite and Franklinite are present in the zinc tailings. In addition, the analysis demonstrated that the Willemite present in the tailings is very fine (80 % < 0.015 mm) and well liberated. With no liberation problems, it was concluded that the main reason responsible for preventing zinc recovery to increase even more along the flotation tests was the presence of the extremely fine Willemite minerals. The test results showed that, to increase zinc recovery, two main processes needed to be considered. The grinding process, that will need to be improved and carefully revised to reduce Willemite fine grain size generation; and the flotation process, regarding bubble formation, reagent addition, resident time and a redesign of flotation machines, aiming to increase the recovery of extremely fine Willemite ore particles.

The aim of this study is to characterize barite samples from Azara located in Nasarawa state, Nigeria, and determine their suitability for oil and gas applications. The mineralogy, chemical composition, morphology and specific gravity were determined using X-ray diffractometry, X-ray fluorescence (XRF), scanning electron microscope and energy-dispersive X-ray and optical microscope. Particle size analysis was done using wet sieve analysis and heavy liquid separation; lastly, a pycnometer was used to determine the specific gravity (SG). The results of the chemical composition by XRF revealed the presence of BaO, Fe2O3, SiO2, SO3 and SrO, while the minor minerals present were MgO, Al2O3, K2O, CaO, MnO and NaO and the trace minerals found were P2O5, Cl, NiO, CuO, ZnO and PbO and mineralogical analysis by X-ray diffractometry revealed the presence of 83% barite, 4% quartz and 14% siderite from the head sample. Wet sieve analysis showed that at −600 + 300-µm- and −150 + 75-µm-sieve size, the SG was slightly above 4.2 g/cm3 meeting the API requirements. The results obtained from the heavy liquid separation (HLS) using TBE (2.95 g/cm3) indicated that mineral liberation occurs at (−600 + 300 µm and −300 + 150 µm), with specific gravities of 4.35 g/cm3 and 4.48 g/cm3, respectively. In the sink fraction (−300 + 150 µm) of the HLS, there were 82% barite, 2% quartz and 17% siderite, while in the float fraction 9% barite, 64% quartz, 2% siderite, 12% feldspar and 14% microcline were found. The results indicate that Azara barite ore meets up with the API requirement for drilling mud and has provided relevant mineralogical information to be used to design mineral processing.

The Florida Canyon deposit hosted by a carbonate-evaporite sequence of the Pucara Group, Peru, has both Zn–Pb sulphide and Zn non-sulphide mineralisations. The mineralogical characterisatio...

Due to the environmental impact of construction and demolition waste (CDW), recycling is mandatory. It is also important that recycled concrete aggregates (RCA) are used in concrete to meet market demands. In the literature, the influence of RCAs on concrete has been investigated, but very limited studies have been conducted on how the origin of concrete waste and comminution processes influence RCA characteristics. This paper aims to investigate the influence of three different comminution and sizing processes (simple screening, crushing and grinding) on the composition, shape and porosity characteristics of RCA obtained from concrete block waste. Crushing and grinding implies a reduction of RCA porosity. However, due to the presence of coarse quartz rounded river pebbles in the original concrete block mixtures, the shape characteristics deteriorated. A large amount of powder (