Dissolved Organic Matter Adsorption to Model Surfaces: Adlayer Formation, Properties, and Dynamics at the Nanoscale

Abstract

Adlayers of dissolved organic matter (DOM) form on many surfaces in natural and engineered systems and affect a number of important processes in these systems. Yet, the nanoscalar properties and dynamics of DOM adlayers remain poorly investigated. This work provides a systematic analysis of the properties and dynamics of adlayers formed from a diverse set of eight humic and fulvic acids, used as DOM models, on surfaces of self-assembled monolayers (SAMs) of different alkylthiols covalently bound to gold supports. DOM adsorption to positively charged amine-terminated SAMs resulted in the formation of water-rich adlayers with nanometer thicknesses that were relatively rigid, irreversibly adsorbed, and collapsed upon air drying, as demonstrated by combined quartz crystal microbalance and ellipsometry measurements. DOM adlayer thicknesses varied only slightly with solution pH from 5 to 8 but increased markedly with increasing ionic strength. Contact angle measurements revealed that the DOM adlayers were relatively polar, likely due to the high water contents of the adlayers. Comparing DOM adsorption to SAM-coated sensors that systematically differed in surface charge and polarity characteristics showed that electrostatics dominated DOM-surface interactions. Laccase adsorption to DOM adlayers on amine-terminated SAMs served to demonstrate the applicability of the presented experimental approach to study the interactions of (bio)macromolecules and (nano)particles with DOM.

One-step synthesis of a novel N-doped microporous biochar derived from crop straws with high dye adsorption capacity

“…We suggest that it is mainly caused by strong electrostatic attraction between AO7 and carbon surfaces. Many reports demonstrate that electrostatic attraction is generally a more powerful adsorption mechanism when several interactions operate simultaneously such as Coulomb forces, van der Waals forces, and hydrophobic effect (Armanious et al 2014). It is understandable that the positively charged sites on NBC800 surfaces would act as high energy sites for AO7 adsorption, and thus prevent many negatively charged AO7 molecules further diffusing into the inner portions of micropores.…”

Effects of Adding Organic Matter to a Red-Yellow Latosol in the Sorption and Desorption of Tebuthiuron

“…Low hysteresis indicates a greater difficulty for the previously sorbed herbicide to be desorbed (Koskinen et al, 2006), that is, the energy to promote the desorption of the herbicide is higher than the one required for the sorption process (Koskinen et al, 2006). The organic matter of the soil usually presents great group diversity (Velten et al, 2011;Armanious et al, 2014). Thus, herbicide molecules and organic matter in the soil establish distinct connections, and the covalents associated to secondary connections, such as hydrogen and Van der Waals bondings (Armanious et al, 2014).…”

“…The organic matter of the soil usually presents great group diversity (Velten et al, 2011;Armanious et al, 2014). Thus, herbicide molecules and organic matter in the soil establish distinct connections, and the covalents associated to secondary connections, such as hydrogen and Van der Waals bondings (Armanious et al, 2014). The strength of the covalent bonding between components is high and, when other interactions occur simultaneously, the energy for the disruption of these bondings is high; this can reduce herbicide desorption (Benoit et al, 2008;Trubetskaya et al, 2014Okada et al, 2016.…”

Investigations of biofilms formed on silica in contact with aqueous formulations containing laccase and maltodextrin

“…The mass adsorbed was calculated using Sauerbrey equation due to the low changes in dissipation [32] (data not shown). The layer thickness of 2.3 nm reached after 74 min of contact was calculated having as reference the density of a hydrated protein layer of 1.3 g/cm 3 [33], the experimentally observed mass value of 320 ng/cm 2 and assuming an homogeneous surface coverage.…”