Preferential phosphate sorption and Al substitution on goethite

Hsu, Liang-Ching; Tzou, Yu-Min; Ho, Mon Shu; Sivakumar, Chandrasekar; Cho, Yen Lin; Li, Wen Hui; Chiang, Po‐Neng; Teah, Heng Yi; Liu, Yu Ting

doi:10.1039/c9en01435g

Cited by 14 publications

(6 citation statements)

References 55 publications

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“…The linearity observed in both theoretical and optimized site densities with respect to Al content points toward the direction of enhanced distribution of Al at the ferrihydrite surface compared to the bulk composition. A similar conclusion was reached by Hsu et al for Al substitution in goethite based on Fe-XAS and XPS analyses.…”

Section: Resultssupporting

confidence: 85%

“…There is currently no experimental evidence to support that Al necessarily substitutes Fe on the surface in a similar pattern as in the bulk structure of ferrihydrite. Recently, Hsu et al 35 showed Al segregation near the surface of Algoethites utilizing iron K-edge X-ray absorption (Fe-XAS) and X-ray photoelectron spectroscopy (XPS). Adams et al 33 modeled ζ-potential titrations with the 15-site model assuming a uniform distribution between the bulk and surface structure.…”

Section: Al-ferrihydrite Surface Structure and Surface Complexation M...mentioning

confidence: 99%

“…Al dopants tend to increase the surface charge density and point of zero charge (PZC) of iron oxides as Al content increases. ,,, Ion uptake is affected to a smaller extent; Adra et al and Liang et al showed an increase of As(VI) and decrease of As(III) and Pb(II) adsorption with increasing Al content, nevertheless, other studies did not observe any significant changes. , Al substitution has shown to increase outer-sphere complexation of oxyanions, , while cation surface speciation was observed to be impacted . PO 4 has shown preferential adsorption to Al sites in both Al-ferrihydrites and Al-goethites. ,, …”

Section: Introductionmentioning

confidence: 97%

“…20 PO 4 has shown preferential adsorption to Al sites in both Alferrihydrites and Al-goethites. 24,35,36 Surface complexation models (SCMs) have the capability to accurately simulate solid−solution interactions incorporating molecular level evidence while also accounting for surface electrostatics. 37,38 The surface reactivity of ferrihydrite has been simulated using various formulations of SCMs, including a two-site model with strong/weak sites, 39 a goethite-based surface model, 1,4,40 and more recently, employing the Hiemstra 14 surface depletion model.…”

Section: Introductionmentioning

confidence: 99%

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Interfacial Properties of Al-Ferrihydrites: Surface Complexation Modeling as a Probe of Surface Structure

Bompoti

Cruz-Hernández

Chrysochoou

et al. 2022

ACS Earth Space Chem.

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Surface reactivity of minerals is impacted by structural impurities in minerals that are prevalent in nature. In this study, we investigate the impact of Al substitution on ferrihydrite’s surface reactivity through surface complexation modeling. Al-bearing ferrihydrites were prepared with various amounts of Al, including 6, 12, and 18 mol % Al. Potentiometric titrations were simulated with a 1-pK charge distribution multisite complexation (CD-MUSIC) model and the MUlti-start optimization algorithm for surface complexation equilibrium parameters (MUSE). The surface structure model for Al-ferrihydrite was based on the assumptions that the total surface site density of Al-ferrihydrite is similar to pure ferrihydrite, the mol % Al corresponds to the respective percentage of the total site density of the mineral surface, and Al is substituting singly coordinated surface hydroxyls in Fe1 octahedral sites. Sensitivity analysis on the protonation constant and site density of Al sites revealed a nonuniform distribution of Al compared to the bulk composition. The results indicate a relative increase of AlOH sites on the Al-Ferrihydrite surface by 21% for 6 Al-Fh, 25% for 12 Al-Fh, and 30% for 18 Al-Fh, which suggests that the entire surface will contain only singly coordinated AlOH groups at 22 mol % Al, instead of the maximum of 29% based on a uniform distribution between bulk and surface. Overall, the findings of this study indicate that the influence of Al is higher than anticipated based on the molar ratio and provide insight into the distribution of impurities within the structure of ferrihydrite.

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Section: Resultssupporting

confidence: 85%

Section: Al-ferrihydrite Surface Structure and Surface Complexation M...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Interfacial Properties of Al-Ferrihydrites: Surface Complexation Modeling as a Probe of Surface Structure

Bompoti

Cruz-Hernández

Chrysochoou

et al. 2022

ACS Earth Space Chem.

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“…Ni et al found Al-substituted goethite presented with an increase in adsorption capacity of Cr(VI) compared with pristine goethite [55]. Hsu et al showed the maximum adsorption capacity of phosphate rose from 135 to 584 mmol/kg when Al/(Al + Fe) mol% changed from 0 to 17.4% [56]. Tufo et al suggested that a small incorporation of Al would enhance the adsorption properties of the goethite surface.…”

Section: Introductionmentioning

confidence: 99%

Efficient Nitrate Adsorption from Groundwater by Biochar-Supported Al-Substituted Goethite

et al. 2022

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Groundwater nitrate contamination is challenging and requires efficient solutions for nitrate removal. This study aims to investigate nitrate removal using a novel adsorbent, biochar-supported aluminum-substituted goethite (BAG). The results showed that an increase in the initial Al/(Al + Fe) atomic ratio for BAGs from 0 to 20% decreased the specific surface area from 115.2 to 75.7 m2/g, but enhanced the surface charge density from 0.0180 to 0.0843 C/m2. By comparison, 10% of Al/(Al + Fe) led to the optimal adsorbent for nitrate removal. The adsorbent’s adsorption capacity was effective with a wide pH range (4–8), and decreased with increasing ionic strength. The descending order of nitrate adsorption inhibition by co-existing anions was SO42−, HCO3−, PO43−, and Cl−. The adsorption kinetics and isotherms agreed well with the pseudo-first-order equation and Langmuir model, respectively. The theoretical maximum adsorption capacity was 96.1469 mg/g. Thermodynamic analysis showed that the nitrate adsorption was spontaneous and endothermic. After 10-cycle regeneration, the BAG still kept 92.6% of its original adsorption capacity for synthetic nitrate-contaminated groundwater. Moreover, the main adsorption mechanism was attributed to electrostatic attraction due to the enhancement of surface charge density by Al substitution. Accordingly, the BAG adsorbent is a potential solution to remove nitrate from groundwater.

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High-Grade REE accumulation in regolith: Insights from supergene alteration of an apatite-rich vein at the Kapunda Cu mine, South Australia

Bamforth,

Xia,

Tiddy

et al. 2024

Miner Deposita

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The stratiform and vein-hosted Kapunda Cu deposit in South Australia contains a saprolitized hydrothermal vein with 12.37 wt.% total rare earth oxide (TREO). The vein was analyzed by X-ray diffraction, scanning electron microscopy, synchrotron-based X-ray fluorescence microscopy and electron backscatter diffraction to understand the controls that govern high-grade REE accumulation during periods of intense weathering. Petrological assessments indicate the transformation of an apatite-calcite-aluminosilicate-bearing protolith to a supergene assemblage of Fe-oxides, kaolinite and REE-phosphate minerals that include rhabdophane-(Ce), monazite-(Ce) and florencite-(Ce). This transformation was facilitated by progressive acidification of the weathering fluid, which is indicated by: 1) the increasing crystallinity of authigenic Fe-oxides and kaolinite, which led to REE desorption; 2) the textural evolution and increase in grain size of authigenic REE-phosphates from nanoscopic crystallites, to acicular needles, to micro-scale hexagonal prisms; 3) the late dissolution of REE-phosphates; and 4) the replacement of goethite by jarosite, whose sulfate component originated from the oxidation and weathering of proximal sulfide minerals. Alongside the depletion of pH-buffering carbonate minerals that are indicated by the preservation of calcite menisci, this sulfide dissolution also facilitated acid generation. Results illustrate how highly acidic weathering fluids might facilitate either REE mobilization or REE accumulation in regolith. High-grade REE accumulation under acidic supergene conditions is prioritized when the host-rock contains a significant source of depositional ligands (i.e., phosphate in the form of apatite) that can be readily leached during intense weathering. Exploration companies should therefore assay routinely for REEs in any heavily weathered phosphatic rock, due to the observed efficiency of phosphate minerals as geochemical traps for REE accumulation.

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Preferential phosphate sorption and Al substitution on goethite

Abstract: The Al-substitution affected not only the basal spacing between adjacent lattice planes but also the structural arrangement in goethite which results in the Al-preferential PO4 sorption on Al-substituted goethite.

Cited by 14 publications

References 55 publications

Interfacial Properties of Al-Ferrihydrites: Surface Complexation Modeling as a Probe of Surface Structure

Interfacial Properties of Al-Ferrihydrites: Surface Complexation Modeling as a Probe of Surface Structure

Efficient Nitrate Adsorption from Groundwater by Biochar-Supported Al-Substituted Goethite

High-Grade REE accumulation in regolith: Insights from supergene alteration of an apatite-rich vein at the Kapunda Cu mine, South Australia

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