Re-Visiting the Quantification of Hematite by Diffuse Reflectance Spectroscopy

Cao, Wei; Jiang, Zhaoxia; Gai, Congcong; Barrón, Vidal; Torrent, J.; Zhong, Yi; Liu, Qingsong

doi:10.3390/min12070872

Cited by 8 publications

(5 citation statements)

References 77 publications

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“…The ∆R spectra of the untreated samples showed the presence of Fe(III) as goethite in the RBS and AQS samples (peaks at 420 and 500 nm), whereas the finer-grained SLT and CLY samples did not contain any discernible peaks due to the relatively low proportions of Fe(III). However, following thermal treatment, the presence of hematite (~560 nm) was observed in the ∆R spectra of all samples (Figure 2c,d) [65,84,85]. Interestingly, the hematite peak in the sand samples was located at 560 nm whereas the hematite peak in the thermally treated SLT and CLY samples was shifted down to 550 nm and exhibited a lower reflectance value despite higher initial bulk Fe concentrations.…”

Section: Fe Mineralogy and Transformations From Thermal Treatmentmentioning

confidence: 96%

“…The ∆R, or first-transform derivative of the reflectance, is highly reproducible and provides indicative information on Fe-oxide mineralogy. For example, Horneman et al [65] found that the ∆R at 520 nm is negatively correlated to the Fe(II)/Fe(Total) content in the sediment and can be used as a proxy for Fe(III); other authors noted that the ∆R spectra are sensitive indicators for hematite and goethite with peaks occurring between 555 and 575 for hematite and two peaks between 420-430 and 480 to 530 for goethite [82][83][84][85]. The ∆R spectra of the untreated and thermally treated sediment samples show contrasting results (Figure 2c,d).…”

Section: Diffuse Reflectance Measurementsmentioning

confidence: 99%

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Mineralogical Associations of Sedimentary Arsenic within a Contaminated Aquifer Determined through Thermal Treatment and Spectroscopy

et al. 2023

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Sedimentary arsenic (As) in the shallow aquifers of Bangladesh is enriched in finer-grained deposits that are rich in organic matter (OM), clays, and iron (Fe)-oxides. In Bangladesh, sediment color is a useful indicator of pore water As concentrations. The pore waters of orange sediments are usually associated with lower As concentrations (<50 µg/L) owing to abundant Fe-oxides which sorb As. Using this color signal as a guide, spectroscopic measurements alongside thermal treatment were extensively utilized for analyzing the properties of both Fe-oxides and clay minerals. This study uses Fourier transform infrared (FTIR) and diffuse reflectance (DR) measurements along with thermal treatment to evaluate the solid-phase associations of As from sediment collected along the Meghna River in Bangladesh. The samples analyzed in this study were chosen to represent the various lithologies present at the study site and included riverbank sands (1 m depth), silt (6 m depth), aquifer sand (23 m depth), and a clay aquitard (37 m depth). The concentrations of sedimentary As and Fe were measured by X-ray fluorescence, and the spectroscopic measurements were taken on the samples prior to the thermal treatment. For the thermal treatment, sediment samples were placed in a preheated furnace at 600 °C for 3 h. The thermal treatment caused a deepening of reddish-brown hues in all samples, and the greatest change in color was observed in the finer-grained samples. The FTIR spectral analysis revealed that the clay minerals were composed primarily of illite, smectite, and kaolinite. The DR results indicate that the majority of Fe in sands was present as goethite; however, in the clay and silt samples, Fe was incorporated into the structure of clay minerals as Fe(II). The amount of structural Fe(II) was strongly positively correlated with the sedimentary As concentrations, which were highest in the finer-grained samples. After thermal treatment, the concentrations of As in the finer-grained samples decreased by an average of 40%, whereas the change in the As concentrations of the sand samples was negligible. These findings indicate that significant proportions of solid-phase As may be retained by OM and Fe(II)-bearing clay minerals.

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Section: Fe Mineralogy and Transformations From Thermal Treatmentmentioning

confidence: 96%

Section: Diffuse Reflectance Measurementsmentioning

confidence: 99%

Mineralogical Associations of Sedimentary Arsenic within a Contaminated Aquifer Determined through Thermal Treatment and Spectroscopy

et al. 2023

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“…Diffuse reflectance spectroscopy (DRS) can detect minerals in a fast, non‐destructive, economic, and eco‐friendly way (Cao et al., 2022; Coblinski et al., 2021; Gras et al., 2014; Stenberg et al., 2010). It has been widely used for iron oxide quantification (e.g., hematite and goethite) (Balsam et al., 2014; Barrón & Torrent, 1986; Jiang et al., 2022; Liu et al., 2011; Scheinost et al., 1998; Torrent & Barrón, 2003), and is potential to be an alternate technique for the analysis of sedimentary samples in large quantities.…”

Section: Introductionmentioning

confidence: 99%

Semi‐Quantification of the Calcium Carbonate in Marine Sediments by Visible and Near‐Infrared Diffuse Reflectance Spectroscopy

Cao,

Liu,

Jiang

et al. 2024

Geochem Geophys Geosyst

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As one of the most widespread components in marine sediments, calcium carbonate (CaCO3) plays a crucial role in the global carbon cycle and climate changes. To efficiently semi‐quantify the CaCO3 concentration, a more effective, non‐destructive, economic, and accurate technique is required. Diffuse reflectance spectroscopy (DRS) has been widely used for the detection and quantification of minerals but has been less studied for CaCO3. This study synthesized a series of samples with well‐determined content of CaCO3 to analyze the visible and near‐infrared DRS characteristics. Results show that the intensity of the second derivative of Kubelka‐Munk (K‐M) remission functions of the DRS spectra at 2,340 nm (I2340) is linearly correlated with the CaCO3 content. Then, the new proxy I2340 was applied for marine sediments from the Pacific Ocean with known CaCO3 concentrations determined previously by chemical methods, and the robustness of the I2340 as the proxy for CaCO3 concentration was attested.

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“…(i) The first derivatives of diffuse reflectance spectral curves have been used to semi-quantitatively determine the amount of hematite in soil [15]. (ii) The application of the second-derivative curve of the Kubelka-Munk (K-M) remission functions has greatly reduced the detection limit of hematite [16]. Thus, DRS is superior to other methods such as Raman spectra and X-ray diffraction for quantifying hematite.…”

Section: Introductionmentioning

confidence: 99%

A New Perspective on the Applicability of Diffuse Reflectance Spectroscopy for Determining the Hematite Content of Fe-Rich Soils in the Tropical Margins of China

Li,

Lü,

Chen

et al. 2024

Minerals

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Hematite and goethite are widely occurring chromogenic iron oxides in soils and sediments that are sensitive to climatic dry/wet shifts. However, only by accurately quantifying the content or ratio of hematite and goethite can they be applied reliably to palaeoclimate reconstruction. Compared to the Loess Plateau of China, hematite in the soils of southern China has not been sufficiently studied. We used diffuse reflectance spectroscopy (abbreviation DRS, including the first-derivative curves and the second-derivative curves of the Kubelka–Munk remission functions), combined with ignition at 950 °C, and X-ray fluorescence (XRF) to quantify the hematite content of four tropical-margin iron-rich soil profiles with different matrix compositions in the Leizhou Peninsula, China. We also examined the application of hematite quantification parameters in soils with different matrix compositions under the same climatic conditions. Our main findings are as follows: (i) DRS first-derivative curves can reflect the presence of goethite and hematite in soils, and their relative contents can be compared within the same profile. (ii) The second-derivative curve of the Kubelka–Munk remission functions can reflect the relative proportions of goethite and hematite and provide information about the degree of Al substitution. (iii) Combined with calibration equations, soil redness can reliably quantify the hematite content, but it is necessary to consider the effect of mucilage envelopes in the process of hematite formation. Additionally, we summarize various methods used for quantifying hematite, and the influence of soil matrix compositions, with the aim of providing a reference for hematite quantification elsewhere. We also propose a new indicator (ΔHmRed/HmRed) to help detect iron hydroxide/iron oxide changes in soils.

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Re-Visiting the Quantification of Hematite by Diffuse Reflectance Spectroscopy

Cited by 8 publications

References 77 publications

Mineralogical Associations of Sedimentary Arsenic within a Contaminated Aquifer Determined through Thermal Treatment and Spectroscopy

Mineralogical Associations of Sedimentary Arsenic within a Contaminated Aquifer Determined through Thermal Treatment and Spectroscopy

Semi‐Quantification of the Calcium Carbonate in Marine Sediments by Visible and Near‐Infrared Diffuse Reflectance Spectroscopy

A New Perspective on the Applicability of Diffuse Reflectance Spectroscopy for Determining the Hematite Content of Fe-Rich Soils in the Tropical Margins of China

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