An integrated flow microcalorimetry, infrared spectroscopy and density functional theory approach to the study of chromate complexation on hematite and ferrihdyrite

Kabengi, Nadine; Chrysochoou, Maria; Bompoti, Nefeli; Kubicki, James D.

doi:10.1016/j.chemgeo.2017.01.017

Cited by 27 publications

(20 citation statements)

References 52 publications

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“…The concentrations of Cr(VI) in our study (50-1000 μM) favored the formation of HCrO 4 − and CrO 4 2− , which minimized the magnitude of the strong overlapping peaks associated with Cr 2 O 7 2− . 51 Moreover, these concentrations were lower than the detection limit of ATR FTIR in solution (<10 mM). 6 Cr-O stretching vibrational peaks were therefore ascribed to the adsorbed Cr(VI) species on LEP surfaces.…”

Section: In Situ Atr-ftir Spectroscopymentioning

confidence: 92%

Molecular-scale study of Cr(vi) adsorption onto lepidocrocite facets by EXAFS, in situ ATR-FTIR, theoretical frequency calculations and DFT+U techniques

Guo

Jin

et al. 2022

Environ. Sci.: Nano

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Section: In Situ Atr-ftir Spectroscopymentioning

confidence: 92%

Molecular-scale study of Cr(vi) adsorption onto lepidocrocite facets by EXAFS, in situ ATR-FTIR, theoretical frequency calculations and DFT+U techniques

Guo

Jin

et al. 2022

Environ. Sci.: Nano

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“…The spectra were then converted to R-space by taking the Fourier transform of χ (k). Fitting was performed simultaneously on all datasets in R-space using Artemis [ 18 ] to determine the degeneracy (N), half-path length (R), and mean-square displacement (σ 2 ) of the backscatterers, in the k range 3–12. The fitting model was identical to the model used for chromate adsorption on hematite [ 46 ], for spectra collected under the same conditions.…”

Section: Methodsmentioning

confidence: 99%

“…However, other results show that several species under any given set of experimental conditions were required in order to explain all of the observed ATR FTIR peaks of phosphate adsorbed onto goethites [ 10 ]. Specifically for chromate adsorption on iron oxides, the authors have performed several studies on ferrihydrite using complementary techniques (ATR FTIR, EXAFS, micro-calorimetry) across a wide variety of experimental conditions [ 8 , 17 , 18 ]. Collectively, these studies have shown that three possible species are present on the surface (binuclear bidentate, monodentate and outer-sphere) and the relative proportion of these is highly dependent on parameters such as the pH, surface coverage, ionic strength and presence of Al in the structure.…”

Section: Introductionmentioning

confidence: 99%

Density functional theory modeling of chromate adsorption onto ferrihydrite nanoparticles

et al. 2018

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Density functional theory (DFT) calculations were performed on a model of a ferrihydrite nanoparticle interacting with chromate () in water. Two configurations each of monodentate and bidentate adsorbed chromate as well as an outer-sphere and a dissolved bichromate () were simulated. In addition to the 3-D periodic planewave DFT models, molecular clusters were extracted from the energy-minimized structures. Calculated interatomic distances from the periodic and cluster models compare favorably with Extended X-ray Absorption Fine Structure spectroscopy values, with larger discrepancies seen for the clusters due to over-relaxation of the model substrate. Relative potential energies were derived from the periodic models and Gibbs free energies from the cluster models. A key result is that the bidentate binuclear configuration is the lowest in potential energy in the periodic models followed by the outer-sphere complex. This result is consistent with observations of the predominance of bidentate chromate adsorption on ferrihydrite under conditions of high surface coverage (Johnston Environ Sci Technol 46:5851–5858, 2012). Cluster models were also used to perform frequency analyses for comparison with observed ATR FTIR spectra. Calculated frequencies on monodentate, bidentate binuclear, and outer-sphere complexes each have infrared (IR)-active modes consistent with experiment. Inconsistencies between the thermodynamic predictions and the IR-frequency analysis suggest that the 3-D periodic models are not capturing key components of the system that influence the adsorption equilibria under varying conditions of pH, ionic strength and electrolyte composition. Model equilibration via molecular dynamics (MD) simulations is necessary to escape metastable states created during DFT energy minimizations based on the initial classical force field MD-derived starting configurations.Electronic supplementary materialThe online version of this article (10.1186/s12932-018-0053-8) contains supplementary material, which is available to authorized users.

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“…A number of approaches exist for the removal of Cr(VI) from water, including oxidation-reduction reactions with iron oxides ( Johnston & Chrysochoou, 2012 ; Liu et al, 2018 ), electrocoagulation ( Martín-Domínguez et al, 2018 ), ion exchange ( Kabengi et al, 2017 ). Reverse osmosis and nanofiltration membranes have also been explored for Cr removal from drinking water ( Anand et al, 2018 ).…”

Section: Introductionmentioning

confidence: 99%

Synthesis and application of cationised cellulose for removal of Cr(VI) from acid mine-drainage contaminated water

Etale¹,

Nhlane²,

Mosai³

et al. 2021

AAS Open Res

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Background: Acid mine drainage (AMD) leads to contamination of surface and ground water by high levels of toxic metals including chromium. In many cases, these waters are sources of drinking water for communities, and treatment is therefore required before consumption to prevent negative health effects. Methods: Cationised hemp cellulose was prepared by etherification with two quaternary ammonium salts: 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHPTAC) and glycidyltrimethylammonium chloride (GTMAC) and examined for (i) the efficiency of Cr(VI) removal under acid mine-drainage (AMD) conditions, and (ii) antibacterial activity. Adsorbents were characterised by electron microscopy, Fourier transform infrared (FTIR), CP-MAS 13C nuclear magnetic resonance (NMR) spectroscopy, elemental composition and surface charge. Results: FTIR and solid state 13C NMR confirmed the introduction of quaternary ammonium moieties on cellulose. 13C NMR also showed that cationisation decreased the degree of crystallisation and lateral dimensions of cellulose fibrils. Nevertheless, 47 % - 72 % of Cr(VI) ions were removed from solutions at pH 4, by 0.1 g of CHPTAC and GTMAC-cationised cellulose, respectively. Adsorption kinetics followed the pseudo-second order model and isotherms were best described by the Freundlich and Dubinin-Radushkevich models. When GTMAC-modified cellulose was applied to AMD contaminated water (pH 2.7); however, Cr(VI) removal decreased to 22% likely due to competition from Al and Fe ions. Cationised materials displayed considerable antibacterial effects, reducing the viability of Escherichia coli by up to 45 % after just 3 hours of exposure. Conclusions: Together, these results suggest that cationised cellulose can be applied in the treatment of Cr(VI)-contaminated mine water particularly if pre-treatments to reduce Fe and Al concentrations are applied.

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An integrated flow microcalorimetry, infrared spectroscopy and density functional theory approach to the study of chromate complexation on hematite and ferrihdyrite

Cited by 27 publications

References 52 publications

Molecular-scale study of Cr(vi) adsorption onto lepidocrocite facets by EXAFS, in situ ATR-FTIR, theoretical frequency calculations and DFT+U techniques

Molecular-scale study of Cr(vi) adsorption onto lepidocrocite facets by EXAFS, in situ ATR-FTIR, theoretical frequency calculations and DFT+U techniques

Density functional theory modeling of chromate adsorption onto ferrihydrite nanoparticles

Synthesis and application of cationised cellulose for removal of Cr(VI) from acid mine-drainage contaminated water

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