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Leaching with Acids
Published in C. K. Gupta, T. K. Mukherjee, Hydrometallurgy in Extraction Processes, 2019
Pyrrhotite is the general name for iron sulfide minerals that occur as two principal structural and compositional types: hexagonal (Fe9S10) and monoclinic (Fe7S8). Leaching of pyrrhotite with HCl results in dissolution of iron and generation of H2S gas which is further treated for the recovery of elemental sulfur. This processing scheme has been the subject of three U.S. Bureau of Mines information circulars101–103 published in 1970. Ingraham et al.104 studied leaching of both stoichiometric (FeS) and nonstoichiometric (Fe7S8) pynhotite with HCl. The leaching reaction was reported as rapid, but when minimum conditions of acidity and/or temperatures were not met, the sulfur coating became protective and the reaction ceased. The authors also reported results of leaching with synthetic troilite, FeS, carried out in the absence of oxidants. The reaction conformed to the equation as given below: () FeS+2HCl→FeCl2+H2S
Interpreting geology from geophysics in poly-deformed and mineralised terranes; the Otago Schist and the Hyde-Macraes Shear Zone
Published in New Zealand Journal of Geology and Geophysics, 2019
Casey C. Blundell, Robin Armit, Laurent Ailleres, Steven Micklethwaite, Adam Martin, Peter Betts
In addition to magnetite, pyrrhotite may influence the magnetic susceptibility of rock. Pyrrhotite is ferrimagnetic in its monoclinic form and may carry significant remanence which is stable for geologically long periods of time at low temperatures (Clark 1997). Frequently found in association with pyrite, the formation of monoclinic pyrrhotite is controlled by sulphur availability and strongly reducing conditions. In reducing environments, pyrrhotite forms preferentially to pyrite, and may also be formed by the de-sulphurisation of pyrite during prograde metamorphism. Higher metamorphic grades also favour pyrrhotite (over pyrite) formation, and the cooling history of the environment will dictate crystal habit. The monoclinic (ferrimagnetic) form of pyrrhotite is unstable above ∼ 250°C and higher temperatures lead to hexagonal forms. The metamorphic breakdown of pyrite to pyrrhotite during regional metamorphism of the schists is thought to be a primary source of sulphur and gold in orogenic gold systems (Tomkins 2010), though pyrrhotite-bearing rock types are not well known near Macraes (Coote et al. 2011).
The Direct Leaching of Nickel Sulfide Flotation Concentrates – A Historic and State-of-the-Art Review Part I: Piloted Processes and Commercial Operations
Published in Mineral Processing and Extractive Metallurgy Review, 2023
Nebeal Faris, Mark I. Pownceby, Warren J. Bruckard, Miao Chen
A list of economically important nickel sulfide and arsenide minerals, as well as common sulfidic gangue in nickel sulfide deposits is presented in Table 3. Pentlandite is the most important nickel sulfide mineral and commonly occurs with pyrrhotite and chalcopyrite. Other nickel sulfides listed in Table 3 can be important where alteration has taken place. Violarite is a supergene alteration product of pentlandite and typically occurs in pyrite-violarite and transition zones above the primary zone (massive pentlandite-pyrrhotite ore) (Marston et al. 1981; Nickel, Ross, and Thornber 1974) and can be economically important during the mining of some massive nickel sulfide ores. Millerite forms as an alteration product of pentlandite (Bide, Hetherington, and Gunn 2008; Holwell et al. 2017) and is an important nickel sulfide mineral in some deposits such as Mt Keith, Black Swan and the Otter Shoot, Kambalda (Dowling et al. 2004; Grguric et al. 2007; Keele and Nickel 1974). Niccolite and gersdorffite can occur in nickel sulfide deposits as a result of hydrothermal alteration; their presence in nickel concentrates is undesirable due to the deleterious effects of As during smelting and typically requires dilution to an acceptable level by blending with low As concentrates (Grguric et al. 2007). Pyrrhotite, an iron sulfide, is the primary gangue sulfide that occurs in nickel sulfide deposits though it typically contains Ni, either in solid solution or as fine pentlandite intergrowths (Rezaei et al. 2017; Toguri 1975). Typically, the Ni concentration in solid solution in pyrrhotite is 0.4–0.6% and the presence of micron-size inclusions of pentlandite can raise the nickel content even higher (Rezaei et al. 2017; Toguri 1975). Hence during beneficiation of nickel sulfide deposits, nickel loss due to pyrrhotite rejection is inevitable.
The effects of various activators on flotation performance of lime-depressed pyrrhotite
Published in Canadian Metallurgical Quarterly, 2019
Jie Liu, Shuai Yuan, Yuexin Han, Yanjun Li
Pyrrhotite (Fe1−xS, where x typically varies between 0 and 0.2) is one of the most common sulfide minerals. It is usually associated with magnetite and base metal sulfides, as well as gold and platinum group minerals, and is frequently disposed as tailings in flotation processes [1–3]. The presence of pyrrhotite in concentrated minerals leads to a decrease in grade; increased sulphur and iron contamination results in an increase in smelting costs [4,5].