Pyrite oxidation in the presence of calcite and dolomite: Alkaline leaching, chemical modeling and surface characterization

Bidari, Ehsan; Aghazadeh, Valeh

doi:10.1016/s1003-6326(18)64782-x

Cited by 18 publications

(7 citation statements)

References 48 publications

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“…The pH has a significant impact on Fe oxidation reactions based on Reactions and , where the oxidation rate is much faster at near-neutral pH compared with acidic pH. , At the reaction surface, the pH of the HFF is lower than 2 . Prior study shows that the pyrite oxidation rate decreased in the presence of calcite and dolomite when the pH is above 13 . This is not the case for our study because the rock matrix had a near-neutral pH before fluid exposure.…”

Section: Resultsmentioning

confidence: 73%

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Fe Oxidation and Species Distribution at the Rock–Fluid Interface of Marcellus Shale Reacted with Hydraulic Fracturing Fluid

et al. 2022

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Hydraulic fracturing of shale reservoirs resulted in significant opportunities for increased oil and gas production in the United States. Rock–fluid interactions can cause mineral dissolution and precipitation reactions that lead to permeability changes in the shale matrix, which ultimately may affect transport pathways and hydrocarbon production. Understanding the distribution of secondary precipitates, such as barite and Fe(III) (hydro)oxides, and cation leaching at the rock–fluid interface is an important step to further investigate how these geochemical processes can change permeability and transport pathways. In this study, thin sections of the fracture-matrix interface were made from reacted Marcellus shale cores. The thin sections were characterized using synchrotron X-ray fluorescence imaging and synchrotron X-ray absorption spectroscopy. Fe species with different oxidation states were identified in the maps, together with barite and Ca distribution. The results show that ferrihydrite, as newly formed Fe(III)-bearing precipitates, aligned well with the border of the Ca (e.g., calcite)-leaching region in the reaction front. Some Fe-containing clay also dissolved, but the dissolution region for the clay was not as deep as the calcite. The reaction front is about three times deeper in the direction parallel to the shale bedding than that perpendicular to the bedding. The Ca-leaching region can be an index for reaction front detection for Marcellus shale. Reactive transport modeling was conducted and the predicted Ca-leaching border aligns well with ferrihydrite precipitation, consistent with the experimental observation. The carbonate mineral dissolution can be crucial to promote fluid access into the shale matrix. Together with our previous study on the shale reactive surface, this follow-up study showed a similar Ca-leaching region and Fe(III) precipitate distribution in the matrix reaction front regardless of barite precipitation on the surface, indicating that the barite coatings on the surface may not pose a significant impact on reactive transport at the shale–fluid interface.

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Section: Resultsmentioning

confidence: 73%

“…20 Prior study shows that the pyrite oxidation rate decreased in the presence of calcite and dolomite when the pH is above 13. 37 This is not the case for our study because the rock matrix had a near-neutral pH before fluid exposure. Aqueous species can penetrate deep into the shale matrix via diffusion.…”

Section: Species Distributionmentioning

confidence: 79%

Fe Oxidation and Species Distribution at the Rock–Fluid Interface of Marcellus Shale Reacted with Hydraulic Fracturing Fluid

et al. 2022

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“…At the incipient stage of pyrite pre-oxidation, it could be suggested the CaOH + and MgOH + first rapidly occupy the active sites on the pyrite surface, and depress the xanthate collector adsorption [24,29]. When enlarging the pre-oxidation time in alkaline conditions, the dominant Ca-bearing species (CaCO 3 ) and Mg-bearing (Mg(OH) 2 ) favor the continuous coaggregation upon these Ca/Mg pre-loaded sites on the negative pyrite surface alongside the nucleation herein, further increasing the pyrite surface hydrophilicity [9,14,15,42,46]. The specific accumulation of secondary hydrophilic Ca/Mg/Fe-bearing minerals leads to a slightly increased hydrophilic coverage upon the pyrite surface, thus a slowly decreased pyrite floatability with increasing preoxidation time.…”

Section: Discussionmentioning

confidence: 99%

“…Traditionally, to reduce sulfur pollution in hydrometallurgy processes through effective pyrite removal, lime was utilized as a cost-effective pulp modifier to alleviate pyrite recovery by forming surface hydrophilic Ca-bearing minerals on pyrite [5][6][7]. Additionally, the surface dissolution of clay minerals such as serpentine, talc, calcite and dolomite also release Ca 2+ and Mg 2+ into flotation systems, which easily form the Ca/Mg hydroxy species/carbonates when pH is over 8 [8][9][10]. Similar to the influence of Ca-bearing minerals on pyrite flotation in alkaline conditions, Mg 2+ can also deteriorate the pyrite floatation recovery because hydrophilic MgOH + and Mg(OH) 2 precipitate attach onto the pyrite surface [11,12].…”

Section: Introductionmentioning

confidence: 99%

Insight on Exogenous Calcium/Magnesium in Weakening Pyrite Floatability with Prolonged Pre-Oxidation: Localized and Concomitant Secondary Minerals and Their Depression Characteristics

et al. 2022

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In this study, we investigated the localized and concomitant precipitation of calcium (Ca)/magnesium (Mg)-bearing species and iron oxides/oxyhydroxides, and their depression characteristics to the pyrite floatability in flotation process at pH 9 and pH 10.5 with prolonged pre-oxidation. Contrary to the depression characteristics at pH 9, the incipient (within aeration times of 30 min) depression of pyrite floatability in Ca/Mg-bearing solutions was more obvious at pH 10.5, while the subsequent decline was only slightly when the pre-oxidation time was expanded to 120 min and 360 min. The competitive adsorption among Ca/Mg-bearing species and potassium amyl xanthate (PAX, C6H11OS2K, collector) at specific sites onto the pyrite surface was demonstrated by the regularly decreased zeta potential of the pyrite surface pretreated in Ca/Mg-bearing solutions. Further scanning electron microscopy-energy dispersive spectrometry demonstrated the concomitant secondary Ca/Mg/Fe-bearing precipitates on the pyrite surface. X-Ray photoelectron spectroscopy suggested strong reprecipitation of iron oxides/oxyhydroxides on the pyrite surface via acid–base complexation among Ca/Mg hydroxy species and iron hydroxy species. Incipient occupation efficiency of specific reaction sites by Ca/Mg-bearing species, which were mainly controlled by the metastable distribution of Ca/Mg hydroxy species and their electrostatic affinity with pyrite surface, was the crucial factor that influenced the competitive adsorption of xanthate and pyrite floatability. More obvious incipient depression at pH 10.5 rather than at pH 9 contributed to more effective Ca/Mg-bearing species and their higher affinity to pyrite surface at pH 10.5. The localized and concomitant precipitation of secondary Ca/Mg/Fe-bearing species leads to a slightly increased hydrophilic coverage upon the pyrite surface, thus a slowly decreased pyrite floatability with increasing pre-oxidation time.

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“…However, the neutral and alkaline mine water is also common, because of the dissolution of alkaline minerals, such as calcite and dolomite. The net effect of which determines the pH value of coal mine water produces a high mineralization value [12,15].…”

Section: Introductionmentioning

confidence: 99%

Leaching Mechanisms of Trace Elements from Coal and Host Rock Using Method of Data Mining

Shan¹

2022

Artificial Intelligence

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Coal and host rock, including the gangue dump, are important sources of toxic elements, which have high-contaminating potential to surface and groundwater. Surface water in the coal mine area and groundwater in the active or abandoned coal mines have been observed to be polluted by trace elements, such as arsenic, mercury, lead, selenium, cadmium. It is helpful to control pollution caused by the trace elements by understanding the leaching behavior and mechanism. The leaching and migration of the trace elements are controlled mainly by two factors, trace elements’ occurrence and the surrounding environment. The traditional method to investigate elements’ occurrence and leaching mechanism is based on the geochemical method. In this research, the data mining method was applied to find the relationship and patterns, which is concealed in the data matrix. From the geochemical point of view, the patterns mean the occurrence and leaching mechanism of trace elements from coal and host rock. An unsupervised machine learning method, principal component analysis was applied to reduce dimensions of data matrix of solid and liquid samples, and then, the re-calculated data were clustered to find its co-existing pattern using the method of Gaussian mixture model.

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Pyrite oxidation in the presence of calcite and dolomite: Alkaline leaching, chemical modeling and surface characterization

Cited by 18 publications

References 48 publications

Fe Oxidation and Species Distribution at the Rock–Fluid Interface of Marcellus Shale Reacted with Hydraulic Fracturing Fluid

Fe Oxidation and Species Distribution at the Rock–Fluid Interface of Marcellus Shale Reacted with Hydraulic Fracturing Fluid

Insight on Exogenous Calcium/Magnesium in Weakening Pyrite Floatability with Prolonged Pre-Oxidation: Localized and Concomitant Secondary Minerals and Their Depression Characteristics

Leaching Mechanisms of Trace Elements from Coal and Host Rock Using Method of Data Mining

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