The conformational dynamics of humic polyanions in model organic and organo-mineral aggregates

Molecular simulation of humic substance–Ca-montmorillonite complexes

“…Published simulations between another model humic molecule and hydrated siloxane surfaces indicate that when such molecules are fully protonated, hydrophobic (Akim et al, 1998;Shevchenko and Bailey, 1998a,b) interactions are common, while when partial deprotonation results in the formation of carboxylate groups, other interactions prevail (Akim et al, 1998;Shevchenko and Bailey, 1998a;Shevchenko et al, 1999). Simulations of a variety of organic materials near smectite and other siloxane surfaces under dry conditions frequently suggest that organic molecules prefer to maximize contact with the mineral, promoting hydrophobic interaction (Shevchenko and Bailey, 1998a,b;Teppen et al, 1998Teppen et al, , 2002Haberhauer et al, 2001;Yu et al, 2000aYu et al, ,b, 2001Yu et al, , 2003.…”

“…The utility of existing published simulations as a probe to evaluate organomineral interactions in natural soils has been limited by their use of inappropriate model conditions, including physically unrealistic mineral species under vacuum or without hydrating water molecules (Schulten andLeinweber, 1996, 2000;Schulten and Schnitzer, 1997;Leinweber and Schulten, 1998;Schulten et al, 1998), and unhydrated monovalent cations (Akim et al, 1998;Shevchenko and Bailey, 1998a,b;Shevchenko et al, 1999), rather than hydrated polyvalent cations, to compensate negative charge.…”

The MS-Q Force Field for Clay Minerals: Application to Oil Production

“…5 The molecular dynamics of clay minerals has been more recently undertaken for gibbsite, kaolinite, pyrophyllite, and beidellite. 6 Enthalpies of adsorption for hydrocarbons on smectite clay 7 and trichloroethene in kaolinite and pyrophyllite 8 humic substances in soils (oxidized lignins) 9 from molecular modeling calculations have been reported. A test of commercial force fields for the modeling of aniline vermiculite and tetramethylammonium vermiculite has been reported.…”

Interaction of Natural Organic Matter with Layered Minerals: Recent Developments in Computational Methods at the Nanoscale

“…Ion bridging between NOM particles was also found to predominate near polyethersulfone membrane surfaces, while no evidence of NOM surface complexes was seen [101]. [86]; (b) lignin-carboxylate complex [104]; and (c) cutin-lignin-tannin complex [106]. Atoms are colored as followed: C (gray), H (white), O (red), N (blue).…”

“…It is a good computational analog of the Suwannee River NOM often used in experimental studies [99][100][101]. Other NOM models have been proposed based on pyrolysis measurements [102,103], lignin-carbohydrate complexes [104,105], and fulvic acid models based on oxysuccinic acid structures [106]. Representative structures of these models are shown in Figure 4.…”