Characterization of phosphate coating formed on pyrite surface to prevent oxidation

Kollias, Konstantinos; Mylona, Evangelia; Adam, Kenneth R.; Chrysochoou, Maria; Papassiopi, Nymphodora; Xenidis, Anthimos

doi:10.1016/j.apgeochem.2019.104435

Cited by 29 publications

(4 citation statements)

References 52 publications

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Section: Interventions I -The Unaltered Pyritementioning

confidence: 99%

“…Later work showed that mainly Fe 2+ phosphates formed, with lesser amounts of Fe 3+ phosphate, iron hydroxides, and iron oxyhydroxides (Kollias et al, 2019). Kollias et al (2019) used a solution of pH 5.5 and found a reduction in sulfur oxidation of 60%. Limits to this technique are that it is only effective at pH>3.5, and that illumination negates the effects of the phosphate in solution, allowing pyrite to react as if no phosphate were present (Elsetinow et al, 2001).…”

Section: Interventions I -The Unaltered Pyritementioning

confidence: 99%

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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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Section: Interventions I -The Unaltered Pyritementioning

confidence: 99%

Section: Interventions I -The Unaltered Pyritementioning

confidence: 99%

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

Tacker¹

2020

Palaeontol Electron

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“…In natural oxic environments, the most common inorganic forms of arsenic and phosphorus are arsenate (H x AsO 4 x –3 ) and phosphate (H x PO 4 x –3 ), respectively. Both arsenate and phosphate are strongly adsorbed to mineral surfaces, especially to the surfaces of iron and aluminum (oxyhydr)oxides. ,− These species are both tetrahedral oxyanions with similar p K a values and thus may display strong competition for adsorption sites on metal oxide mineral surfaces. The competitive adsorption between arsenate and phosphate has been investigated in previous studies, but the majority of which were performed on iron (oxyhydr)oxide minerals and similar competition is poorly constrained on aluminum-bearing phases. − In addition, whether the co-adsorption of two oxyanions alters the coordination mechanism or adsorption equilibrium constant for each adsorbate remains uncharacterized with integrated applications of spectroscopy and quantitative models.…”

Section: Introductionmentioning

confidence: 99%

Effects of Phosphate Competition on Arsenate Binding to Aluminum Hydroxide Surfaces

Wang

et al. 2021

ACS Earth Space Chem.

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Aluminum hydroxide plays a substantial role in regulating the environmental fate and transport of arsenate and phosphate. These minerals display multiple types of surface reactive sites with distinct adsorption affinities. As arsenate and phosphate coexist in many natural systems, a detailed understanding of their interactive adsorption behaviors on aluminum hydroxides and the underlying binding mechanisms is thus required to develop predictive models of their fate and mobility. In this study, we explore how phosphate affects arsenate adsorption onto the aluminum hydroxide polymorphs gibbsite and bayerite and develop a unified surface complexation model (SCM) to predict arsenate adsorption under diverse conditions parameterized only from noncompetitive uptake data. Macroscopic studies show that both oxyanions behave similarly in individual adsorption experiments. The addition of phosphate reduces arsenate adsorption on both minerals with a greater effect observed on gibbsite. Extended X-ray absorption fine structure spectroscopy reveals that similar arsenate species occur on both minerals and are unchanged in the presence of phosphate. This indicates that competitive adsorption does not affect arsenate surface speciation. These results demonstrate that arsenate and phosphate primarily interact on aluminum hydroxide surfaces via site competition. Notably, their similar pK a values and adsorption affinities minimize modification of adsorption behavior from surface electrostatic effects. The SCMs demonstrate that multiple arsenate surface species are needed to reproduce the observed competitive uptake data, in apparent conflict with the spectroscopic results that reveal no change in coordination at different surface coverages. This indicates that the molecular-scale drivers of differences in surface complex stability are not only from distinct local coordination, instead other factors, such as hydrogen bonding among the adsorbates, surface oxygens, and interfacial water or different surface complexes coordinating to functional groups with distinct connections to the underlying mineral structure, may also play an important role.

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“…At present, an alternative strategy, namely passivation, has been developed to treat AMD at the source by suppressing the oxidation of pyrite and other sulfide minerals. The passivation method mainly focuses on using chemical passivation materials to come in contact with pyrite, where its surface will combine via ionic or covalent bonds to form a dense passivation film, thereby inhibiting the oxidation of iron in the pyrite lattice. , So far, a large amount of passivation materials including phosphates, silicates, triethylenetetramines hydroxyquinonline, silicate, catechol, phosphate, triethylenetetramine, and phospholipids have been reported. − Nevertheless, each of these passivators has its own drawbacks. For example, the formation of a phosphate or silicate passivation film may involve hydrogen peroxide or hypochlorite, which is more expensive.…”

Section: Introductionmentioning

confidence: 99%

Performance and Mechanisms of PropS-SH/HA Coatings in the Inhibition of Pyrite Oxidation

et al. 2021

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Acid mine drainage (AMD) entering the environment will cause long-term environmental pollution and ecological damage, the treatment or remediation for which has become a difficult worldwide problem. To control AMD at the source, a novel composite coating, hydroxyapatite (HA) as the filler embedded in a γ-mercaptopropyltrimethoxysilane (PropS-SH) coating, was introduced in this study. The performance and mechanisms of PropS-SH/HA coatings in the inhibition of pyrite oxidation were investigated by chemical leaching testing and material structure characterization. The results of the investigations revealed that the addition of an appropriate amount of HA can enhance the passivation efficiency of the PropS-SH coating. The best coating was obtained from 3% (v/v) of PropS-SH solution with 16 wt % HA, as this coating decreased pyrite oxidation by 78.7% (based on total Fe release). The main mechanism of PropS-SH/HA for the inhibition of pyrite oxidation involved the generation of a PropS-SH network through a polycondensation reaction. The addition of HA increased the stability of the passivation film composed of PropS-SH as well as the combining capacity of PropS-SH/HA through the formation of Si–O–Si and Fe–O–Si bonds, respectively.

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Characterization of phosphate coating formed on pyrite surface to prevent oxidation

Cited by 29 publications

References 52 publications

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

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

Effects of Phosphate Competition on Arsenate Binding to Aluminum Hydroxide Surfaces

Performance and Mechanisms of PropS-SH/HA Coatings in the Inhibition of Pyrite Oxidation

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