In situ ATR-FTIR investigation and theoretical calculation of the interactions of chromate and citrate on the surface of haematite (α-Fe<sub>2</sub>O<sub>3</sub>)

Gao, Weiguo; Liu, Xingchen; Chen, M. F.

doi:10.1039/c7ra04587e

Cited by 21 publications

(9 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This result contradicted the findings of previous studies, which implied that the IS complex formed mainly at low pH, whereas the outer-sphere complex was dominant at high pH. Gao et al (2017) tried to evaluate the interaction between citrate and chromate on hematite, and they observed the reduction of chromate to chromite by electron transfer from citrate. The structural configuration of citrate was presumed to be a monodentate or bidentate ring structure, but no detailed description was provided.…”

Section: Structural Configuration Of Organic Acidscontrasting

confidence: 81%

Factors modifying the structural configuration of oxyanions and organic acids adsorbed on iron (hydr)oxides in soils. A review

Han

Kim

2020

Environ Chem Lett

View full text Add to dashboard Cite

Oxyanions are ubiquitous in soils, organisms and the environment. Due to their unique chemical structure, oxyanions can be easily transferred into other systems. Carbonate (CO 3 2−), nitrate (NO 3 −), phosphate (PO 4 3−), silicate (SiO 4 2−) and sulfate (SO 4 2−) are the major oxyanions in organisms and the soil environment, whereas arsenate (AsO 4 3−), antimonate (SbO 4 3−), borate (BO 3 3−), selenate (SeO 4 2−), and tellurate (TeO 4 2−) are generally reported as toxic chemicals found at trace levels. Excessive oxyanions leached from soils into water have caused severe environmental problems. Here, we review the factors affecting the structural configuration of oxyanions and organic acids adsorbed on iron oxides and hydroxides. The configuration of oxyanions on iron (hydr)oxides is controlled by surface loading, pH, sample phase, competing ions and organic acids. Under conditions of low surface loading and low pH at the interface in the absence of competing ions, oxyanions with high affinity possibly form a complex with higher denticity. But an increase in pH decreases the number of sorption sites; thus, a transition from a tri-or bidentate complex to monodentate and outer-sphere complexes occurs.

show abstract

Section: Structural Configuration Of Organic Acidscontrasting

confidence: 81%

Factors modifying the structural configuration of oxyanions and organic acids adsorbed on iron (hydr)oxides in soils. A review

Han

Kim

2020

Environ Chem Lett

View full text Add to dashboard Cite

show abstract

“…Infrared (IR) studies of phosphate adsorption onto Fe‐oxides have shown that phosphate forms a mixture of different inner‐sphere surface complexes whose proportions vary with pH and surface coverage (Arai & Sparks, ; Elzinga & Kretzschmar, ; Elzinga & Sparks, ; Kubicki et al., ; Luengo, Brigante, Antelo, & Avena, ; Tejedor‐Tejedor & Anderson, ). The speciation of citrate at goethite and hematite surfaces is similarly complex and also consists of various complexes with variable abundance depending on pH and surface loading (Borer & Hug, ; Gao, Liu, & Chen, ; Lindegren & Persson, ; Lindegren, Loring, & Persson, ; Noerpel & Lenhart, ; Situm, Rahman, Goldberg, & Al‐Abadleh, ). The mechanistic complexity of phosphate and citrate adsorption makes it difficult to predict the behavior of these species in environments where both are present, highlighting the need for spectroscopic studies of dual‐sorbate systems.…”

Section: Introductionmentioning

confidence: 99%

Attenuated total reflectance–Fourier transform infrared study of the effects of citrate on the adsorption of phosphate at the hematite surface

Barreto

Elzinga

Alleoni

2020

Soil Science Soc of Amer J

View full text Add to dashboard Cite

Carboxylic acids affect the retention and solubility of phosphate in soils and rhizospheres, but spectroscopic studies addressing the mechanisms involved are scarce. Here, we used in situ attenuated total reflectance Fourier transform infrared spectroscopy to study the mechanisms of adsorption of orthophosphate and citric acid onto hematite in binary and ternary systems at pH 4.5, 5.5, and 6.5. In binary systems, phosphate adsorbed as a mixture of two inner‐sphere species assigned as monodentate and bridging complexes, with the fraction of bridging species increasing with decreasing pH. Citrate coordinated to the hematite surface through the carboxylate groups, which consisted of a mixture of inner‐sphere complexes and either noncoordinated or outer‐sphere complexes, with inner‐sphere complexation becoming more important at lower pH. Introduction of citrate into pre‐equilibrated phosphate–hematite systems induced desorption of both the monodentate and bridging phosphate species, with competitive effects increasing with decreasing pH. At pH 5.5 and 6.5, the bridging complexes were mobilized to a larger extent than initially present on the surface, indicating preferential desorption. Similarly, pre‐equilibration of hematite with citrate preferentially inhibited the formation of the bridging phosphate surface complexes. Their relatively strong susceptibility to interference by citrate suggests that the bridging phosphate species are protonated monodentate complexes engaged in hydrogen bonding to adjacent surface sites. The results of this study refine our understanding of the mechanisms of phosphate retention at Fe‐oxide mineral surfaces and demonstrate that carboxylic acids may affect not only phosphate solubility but also the speciation of phosphate associated with Fe‐oxides in soil and rhizosphere environments.

show abstract

“…Meanwhile, the absorbance of the shoulder peak at 1531 cm –1 exhibited a distinct decrease compared with that of the CA-Sch system, indicating the reduction of coordinated carboxylate groups. , This phenomenon might be attributed to the weakening of one coordinated carboxylate group under the effects of Cr(VI) adsorption. Gao et al found that electrons could be transferred from the carboxyl groups of CA to Cr(VI) via the Fe–O bond of hematite. Therefore, redox reactions may occur between the coordinated CA and Cr(VI) on the mineral surface, which will lead to the destruction of the surface geometry and produce changes in the bands of the IR spectra.…”

Section: Resultsmentioning

confidence: 99%

“…Citric acid (CA) is widely detected in acidic soil, sediment, and aquatic systems and commonly ranges from 0.01 to 1 mM . As well known, CA has three carboxyl groups, giving great complexation ability with iron oxides and forming inner or outer sphere complexes. , Meanwhile, CA could also act as a potential reductant for Cr(VI) in the presence of iron and manganese oxides or titanium oxides. − For example, Gao et al observed that the competitive adsorption and redox reactions both occurred between CA and Cr(VI) on the hematite surface. Jiang et al found that Cr(VI) could be reduced by CA over Sch in a homogeneous system under mimic solar light, which was prevalent in naturally contaminated environments.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Interactions Occurring Between Cr(VI) and Citric Acid-Schwertmannite Composites: A Macroscopic and In Situ ATR-FTIR Study

Liang

et al. 2022

ACS Earth Space Chem.

View full text Add to dashboard Cite

Organo-mineral composites play an important role in the mobility and bioavailability of toxic metals in natural environments. However, the interactions between heavy metals and composites remain ambiguous. In this study, citric acidschwertmannite (CA-Sch) composites were synthesized to investigate the interfacial behaviors of Cr(VI) adsorption via macroscopic experiments (adsorption kinetics, adsorption isotherms, and pH adsorption edge) coupled with in situ ATR-FTIR spectroscopy and XPS analysis. Macroscopic experimental results showed that the adsorption capacities and rate of Cr(VI) on CA-Sch composites presented a distinct decrease compared with those on Sch, wherein the former had a negative linear correlation with carbon loading content and the pH IEP of the composites. The structural sulfate and adsorbed CA could be substituted by Cr(VI) ions. In situ ATR-FTIR spectra of CA-Sch showed different responses after Cr(VI) adsorption, including a continuous release of structural sulfate and a slight weakening in the v as (COO − ) and v s (COO − ) of adsorbed CA, further revealing that Cr(VI) mainly coordinated to the CA-Sch composite surface via anion exchange with the tunnel structural sulfate, followed by an outer-sphere CA complex on the external surface. The coordination modes of Cr(VI) on the composite included monodentate (C 3v ) and bidentate (C 2v ) complexes. In addition, the analysis of element species content and XPS showed that partially adsorbed Cr(VI) on the CA-Sch composite was reduced to Cr(III) without being released into the solution. These findings advance our understanding of the interfacial behaviors of Cr(VI) on the CA-Sch composite surface and contribute to the evaluation of the fate of Cr(VI) in AMDcontaminated environments.

show abstract

In situ ATR-FTIR investigation and theoretical calculation of the interactions of chromate and citrate on the surface of haematite (α-Fe₂O₃)

Abstract: In situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy was used to study the molecular kinetics of Cr(VI) reduction by citric acid at the a-Fe 2 O 3 -water interface. Both citrate and Cr(VI) were adsorbed to the surface of a-

Cited by 21 publications

References 31 publications

Factors modifying the structural configuration of oxyanions and organic acids adsorbed on iron (hydr)oxides in soils. A review

Factors modifying the structural configuration of oxyanions and organic acids adsorbed on iron (hydr)oxides in soils. A review

Attenuated total reflectance–Fourier transform infrared study of the effects of citrate on the adsorption of phosphate at the hematite surface

Investigation of the Interactions Occurring Between Cr(VI) and Citric Acid-Schwertmannite Composites: A Macroscopic and In Situ ATR-FTIR Study

Contact Info

Product

Resources

About

In situ ATR-FTIR investigation and theoretical calculation of the interactions of chromate and citrate on the surface of haematite (α-Fe2O3)

Abstract: In situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy was used to study the molecular kinetics of Cr(VI) reduction by citric acid at the a-Fe 2 O 3 -water interface. Both citrate and Cr(VI) were adsorbed to the surface of a-

Cited by 21 publications

References 31 publications

Factors modifying the structural configuration of oxyanions and organic acids adsorbed on iron (hydr)oxides in soils. A review

Factors modifying the structural configuration of oxyanions and organic acids adsorbed on iron (hydr)oxides in soils. A review

Attenuated total reflectance–Fourier transform infrared study of the effects of citrate on the adsorption of phosphate at the hematite surface

Investigation of the Interactions Occurring Between Cr(VI) and Citric Acid-Schwertmannite Composites: A Macroscopic and In Situ ATR-FTIR Study

Contact Info

Product

Resources

About

In situ ATR-FTIR investigation and theoretical calculation of the interactions of chromate and citrate on the surface of haematite (α-Fe₂O₃)