Advances of molecular modeling of biogeochemical interfaces in soils

Tunega, Daniel; Gerzabek, Martin H.; Totsche, Kai Uwe

doi:10.1016/j.geoderma.2011.07.021

Cited by 5 publications

(1 citation statement)

References 9 publications

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“…To understand these experimental results at the atomic and molecular levels, we performed theoretical calculations based on density functional theory. These techniques have recently been successfully applied in the field of soil science. ,, The presence of the above-mentioned chemical groups indicates the similarity, at the molecular level, between the TPI-carbons and graphene oxide. , It is well-known that the most common oxide groups in graphene oxide are the epoxide and hydroxyl groups in the basal plane and the carboxyl group (and possibly some hydroxyl and carbonyl groups) at the crystallite edges. , We explored this similarity to construct simplified theoretical models for the TPI-carbons. A graphene nanocluster (C 54 H 18 molecule) was then used as a host for various oxygen chemical groups and Ca 2+ , making it possible to study their interactions.…”

Section: Resultsmentioning

confidence: 99%

Chemical Analysis and Molecular Models for Calcium–Oxygen–Carbon Interactions in Black Carbon Found in Fertile Amazonian Anthrosoils

Archanjo

Araújo

Silva

et al. 2014

Environ. Sci. Technol.

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Carbon particles containing mineral matter promote soil fertility, helping it to overcome the rather unfavorable climate conditions of the humid tropics. Intriguing examples are the Amazonian Dark Earths, anthropogenic soils also known as "Terra Preta de Índio'' (TPI), in which chemical recalcitrance and stable carbon with millenary mean residence times have been observed. Recently, the presence of calcium and oxygen within TPI-carbon nanoparticles at the nano- and mesoscale ranges has been demonstrated. In this work, we combine density functional theory calculations, scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier transformed infrared spectroscopy, and high resolution X-ray photoelectron spectroscopy of TPI-carbons to elucidate the chemical arrangements of calcium-oxygen-carbon groups at the molecular level in TPI. The molecular models are based on graphene oxide nanostructures in which calcium cations are strongly adsorbed at the oxide sites. The application of material science techniques to the field of soil science facilitates a new level of understanding, providing insights into the structure and functionality of recalcitrant carbon in soil and its implications for food production and climate change.

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Section: Resultsmentioning

confidence: 99%

Chemical Analysis and Molecular Models for Calcium–Oxygen–Carbon Interactions in Black Carbon Found in Fertile Amazonian Anthrosoils

Archanjo

Araújo

Silva

et al. 2014

Environ. Sci. Technol.

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Study of Carbon Nanostructures for Soil Fertility Improvement

Jório

Archanjo

Ribeiro-Soares

et al. 2015

Bioengineering Applications of Carbon Nanostructures

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Acidity of edge surface sites of montmorillonite and kaolinite

Liu

Sprik

et al. 2013

Geochimica et Cosmochimica Acta

194

160

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Acid-base chemistry of clay minerals is central to their interfacial properties, but up to 10 now a quantitative understanding on the surface acidity is still lacking. In this study, with first principles 11 molecular dynamics (FPMD) based vertical energy gap technique, we calculate the acidity constants of 12 surface groups on (010)-type edges of montmorillonite and kaolinite, which are representatives of 2:1 13 and 1:1-type clay minerals, respectively. It shows that ≡Si-OH and ≡Al-OH 2 OH groups of kaolinite 14 have pKas of 6.9 and 5.7 and those of montmorillonite have pKas of 7.0 and 8.3, respectively. For each 15 mineral, the calculated pKas are consistent with the experimental ranges derived from fittings of 16 titration curves, indicating that ≡Si-OH and ≡Al-OH 2 OH groups are the major acidic sites responsible to 17 pH-dependent experimental observations. The effect of Mg substitution in montmorillonite is 18 investigated and it is found that Mg substitution increases the pKas of the neighboring ≡Si-OH and ≡Si-19 OH 2 groups by 2~3 pKa units. Furthermore, our calculation shows that the pKa of edge ≡Mg-(OH 2 ) 2 is 20 as high as 13.2, indicating the protonated state dominates under common pH. Together with previous 21 adsorption experiments, our derived acidity constants suggest that ≡Si-O-and ≡Al-(OH) 2 groups are the 22 most probable edge sites for complexing heavy metal cations.

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Advances of molecular modeling of biogeochemical interfaces in soils

Cited by 5 publications

References 9 publications

Chemical Analysis and Molecular Models for Calcium–Oxygen–Carbon Interactions in Black Carbon Found in Fertile Amazonian Anthrosoils

Chemical Analysis and Molecular Models for Calcium–Oxygen–Carbon Interactions in Black Carbon Found in Fertile Amazonian Anthrosoils

Study of Carbon Nanostructures for Soil Fertility Improvement

Acidity of edge surface sites of montmorillonite and kaolinite

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