A comparative study of the thermal decomposition of pyrite under microwave and conventional heating with different temperatures

Zhang, Xiaoliang; Kou, Jue; Sun, Chunbao

doi:10.1016/j.jaap.2018.12.002

Cited by 38 publications

(9 citation statements)

References 61 publications

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“…Moreover, thermal oxidation of organic matter, which releases CO2 and H2O specially from above 420º C, could contribute to increase the pore-pressure. In addition, the presence of CO2 from organic matter and calcite decomposition speeds up the thermal oxidation of the pyrite 29 (Lv et al 2015;Zhang et al 2019), which leads to a more violent chemical reaction. The DSC curve showed that thermal oxidation of pyrites and organic matter are both exothermic reactions which locally accelerate the thermal oxidation of pyrite (Figure 4).…”

Section: Discussionmentioning

confidence: 99%

“…The wide occurrence of pyrite in different minerals and coals makes it one of the main sources of SO 2 (acid rain precursor) emission from various industrial activities, such as coal conversion (Seehra and Jagadeesh 1981), power production (Lv et al 2015), and cement production (Hansen et al 2003;Cheng et al 5 2014). Pyrite in auriferous and carbonaceous matters is usually found in association with valuable metallic elements such as Au, Ag, and Cu and their recovery includes the oxidative roasting of raw materials (Zhang et al 2019). Pyrite is common in sedimentary rocks studied as a potential host rock for radioactive waste like claystone, and its oxidation is harmful to the corrosion kinetics of metallic engineered components (Verron et al 2019).…”

Section: Introductionmentioning

confidence: 99%

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Temperature-Induced Explosive Behaviour and Thermo-Chemical Damage on Pyrite-Bearing Limestones: Causes and Mechanisms

et al. 2020

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In this investigation, two different varieties of 'Prada' limestones were studied: a dark grey texture, bearing quartz, clay minerals, organic matter and pyrites, and a light grey texture with little or no presence of such components. We have observed two effects of different intensity when heating the dark texture from 400º C: i) the explosion of certain samples and ii) greater thermal damage than in the light grey texture. Chemical and mineralogical composition, texture, microstructure, and physical properties (i.e. colour, open porosity, P and S-wave velocity) have been evaluated at temperatures of 105, 300, 400 and 500º C in order to identify differences between textures. The violence of the explosive events was clear and cannot be confounded with ordinary splitting and cracking on thermally-treated rocks: exploded samples underwent a total loss of integrity, displacing and overturning the surrounding samples, and embedding fragments in the walls of the furnace, whose impacts were clearly heard in the laboratory. Thermogravimetric results allowed the identification of a process of oxidation of pyrites releasing SO 2 from 400º C. This process jointly with the presence of micro-fissures in the 2 dark texture, would cause a dramatic increase in pore-pressure, leading to a rapid growth and coalescence of microcracks that leads to a process of catastrophic decay in rock integrity. In addition to the explosive events, average ultrasound velocities and open porosity showed a greater variation in the dark grey texture from 400º C. That results also points towards a significant contribution of oxidation of pyrites on the thermochemical damage of the rock, among other factors such as the pre-existence of microfissuresand the thermal expansion coefficient mismatch between minerals. Implications in underground infrastructure and mining engineering works are critical, as the explosive potential of pyrite-bearing limestones bear risk for mass fracturing and dramatic strength decay from 400º C. Moreover, SO 2 released has harmful effects on health of people and the potential to form acid compounds that corrode materials, shortening their durability and increasing maintenance costs.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Temperature-Induced Explosive Behaviour and Thermo-Chemical Damage on Pyrite-Bearing Limestones: Causes and Mechanisms

et al. 2020

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“…Heating in air results in evolution of SO 2 gas, and above 450°C, formation of hematite (Fe 2 O 3 ). The peak of reaction in argon is measured at 635°C (Thomas et al, 2003) and 665°C in nitrogen (Zhang et al, 2019). The reaction peak does not seem to shift to lower temperatures with lower pressures.…”

Section: Interventions II -Pyrite and Efflorescent Mineralsmentioning

confidence: 93%

A review of “pyrite disease” for paleontologists, with potential focused interventions

Tacker¹

2020

Palaeontol Electron

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A literature review of the chemical reactions involved in pyrite oxidation/hydration ("pyrite disease") in geological or fossil collections gives direction to a suite of focused interventions. Reactions on the pyrite surface lie at the heart of the chemical process, accompanied by the movement of electrons on and through the pyrite semiconductor. Control of these electrons ultimately may be futile, but examination of the reactions at the atomic level leads to new possibilities for treatment, and identifies why some treatments are ineffective. This review also identifies gaps in our understanding of the oxidation and hydration reactions. Fossil biomaterials-bone or shell-often contain or are partially replaced by pyrite. Acidity produced by pyrite decay destroys these materials. Older treatments focus on acid neutralization, and humidity control as solutions for megascopic problems. Focused interventions target specific steps in the chemical reactions at the atomic scale. Interventions are informed by identification of all the minerals participating in the process, and accurate characterization of the bone, pyrite and sedimentary matrix. Bone minerals and pyrite are structurally and chemically heterogeneous, so each intervention requires bench testing, complimented by analytical measurements. Chemically passivating the unreacted pyrite surface shows the greatest promise. Anticipation of a new specimen's susceptibility to decay is key. Decay may be accelerated using techniques of humidity buffering with saturated salt solutions. Conductivity of pyrite (which varies over four orders of magnitude) may be measured. A database of pyrite conductivity is highly desirable.

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“…An alternative to these techniques is the use of microwaves that through a heat source transforms the characteristics of the mineral, increasing the percentages of gold extraction in refractory minerals. Gaviria et al (2006), Daza et al (2011), Lovás et al (2011, Zhang et al (2019), McGill et al (2015, Xu (2015), Sun et al (2012).…”

Section: Introductionmentioning

confidence: 99%

Microwave treatment for gold minerals used in small-scale mining

Tovar

Gómez

Pinilla

et al. 2022

JART

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Gold mining in Colombia has produced wealth that has helped the social and economic development of the country. Studying its extraction process offers artisanal mining broad alternatives that are more profitable for its small-scale production. Through this research, the possibility is offered of extracting 93.10% of gold in 180 minutes from a refractory mineral of pyritic origin with economic and environmentally friendly techniques such as the use of pretreatment with microwave waves, exposing the mineral to 637ºC for a maximum time of 4 minutes, and the use of thiourea as leaching agent at concentrations of 0.1 M. When comparing gold extraction with thiourea without pretreatment, a low extraction percentage is shown, 19.98%. This microwave pretreatment process was carried out on a nickeliferous laterite mineral, however, the results were not as effective for the extraction of nickel, only 40.8% was obtained in 420 minutes, because the pretreatment with its exposure Microwaving was not efficient.

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A comparative study of the thermal decomposition of pyrite under microwave and conventional heating with different temperatures

Cited by 38 publications

References 61 publications

Temperature-Induced Explosive Behaviour and Thermo-Chemical Damage on Pyrite-Bearing Limestones: Causes and Mechanisms

Temperature-Induced Explosive Behaviour and Thermo-Chemical Damage on Pyrite-Bearing Limestones: Causes and Mechanisms

A review of “pyrite disease” for paleontologists, with potential focused interventions

Microwave treatment for gold minerals used in small-scale mining

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