Adsorption Of Dicarboxylic Acids Research Articles

Nanoscale Forces between Basal Mica Surfaces in Dicarboxylic Acid Solutions: Implications for Clay Aggregation in the Presence of Soluble Organic Acids.

The stability of organomineral aggregates in soils has a key influence on nutrient cycling, erosion, and soil productivity. Both clay minerals with distinct basal and edge surfaces and organic molecules with reactive functional groups offer rich bonding environments. While clay edges often promote strong inner-sphere bonding of −COOH-laden organics, we explore typically weaker, outer-sphere bonding of such molecules onto basal planes and its significance in organomineral interactions. In this surface force apparatus study, we probed face-specific interactions of negatively charged mica basal surfaces in solutions containing carboxyl-bearing, low-molecular-weight dicarboxylic acids (DAs). Our experiments provide distance-resolved, nanometer-range measurements of forces acting between two (001) mica surfaces and simultaneously probe DA adsorption. We show that background inorganic ions display crucial importance in nanoscale forces acting between basal mica surfaces and in DA adsorption: Na+ contributes to strong repulsion and little binding of dicarboxylic anions, while small amounts of Ca2+ are sufficient to screen the basal surface charge of mica, facilitate strong adhesion, and enhance dicarboxylic anion adsorption by acting as cationic bridges. Despite reversible and weak adsorption of DAs, we resolve their multilayer binding via assembly of hydrophobic chains in the presence of Ca2+, pointing the importance of abundant, less reactive basal clay surfaces in organomineral interactions.

Chiral Surface from Achiral Ingredients: Modification of Cu(110) with Phthalic Acid

The adsorption of dicarboxylic acids is a classical model approach for understanding molecular recognition at surfaces. The interaction of achiral phthalic acid with an achiral Cu(110) surface has ...

Adsorption of dicarboxylic acids onto nano‐structured silver surfaces – surface‐enhanced Raman scattering studies of pH‐dependent adsorption geometries

Understanding and shaping adsorption orientations of molecular compounds on nano‐structured metallic surfaces is an important issue across many areas of contemporary research including the design of nano‐structured surfaces and catalytic processes. Here, we used surface‐enhanced Raman spectroscopy to study these orientations on nano‐structured silver surfaces using dicarboxylic acids (maleic acid and fumaric acid) as model substances.Results revealed a clear pH dependence of the observed adsorption geometries of dicarboxylic acids correlating well with the dissociation states of the two acidic groups. Our data demonstrate the potential of the technique and contribute to an improved understanding of adsorption orientations of molecules at the interface between nano‐structured metal surfaces and a liquid phase. Copyright © 2012 John Wiley & Sons, Ltd.

Effect of dehydration on dicarboxylic acid coordination at goethite/water interface

The adsorption of dicarboxylic acids by goethite at different pH conditions was investigated using in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) and ex situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Adsorption of dicarboxylic acids (succinic acid, glutaric acid, adipic acid, and azelaic acid) was the highest at pH 4 as compared with those at pH 7 and 9. The aliphatic chain length of the dicarboxylic acids greatly influenced the sorption amount at acidic pH: succinic acid [HOOC(CH2)2COOH] < glutaric acid [HOOC(CH2)3COOH] < adipic acid [HOOC(CH2)4COOH] < azelaic acid [HOOC(CH2)7COOH]. With in situ ATR-FTIR analysis, wet samples tend to have outer-sphere adsorption at all tested pHs. However, inner-sphere coordination between the carboxyl groups and goethite surface is dominant for freeze-dried complex samples with DRIFT analysis. The adsorption types, inner- or outer-sphere, depend on dicarboxylic acid species, pH, and solvent conditions (dry vs. wet). From the experimental data, we suggest that organic acids in an aqueous environment prefer to adsorb onto goethite by outer-sphere interaction, but inner-sphere complexation is favored under dry conditions. Thus, organic acids binding onto clay minerals under dry conditions are stronger than that under wet conditions, and we expect different conformations and aggregations of adsorbed organic acids as influenced by complexation types. In the environment, natural organic matter (NOM) may adsorb predominantly on positive charged mineral surfaces at the aqueous interface, which can convert onto inner-sphere coordination during dehydration. The stable NOM/mineral complexes formed by frequent wetting–drying cycles in nature may resist chemical/microbial degradation of the NOM, which will affect carbon storage in the environment and influence the sorption of organic contaminants.

Adsorption of Dicarboxylic Acids by Clay Minerals as Examined by in Situ ATR-FTIR and ex Situ DRIFT

The adsorption of dicarboxylic acids by kaolinite and montmorillonite at different pH conditions was investigated using in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) and ex situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The sorption capacity of montmorillonite was greater than that of kaolinite. Adsorption of dicarboxylic acids (succinic acid, glutaric acid, adipic acid, and azelaic acid) was the highest at pH 4 as compared with those at pH 7 and 9. These results indicate that sorption is highly pH-dependent and related to the surface characteristics of minerals. The aliphatic chain length of the dicarboxylic acids highly influenced the sorption amount at acidic pH, regardless of the clay mineral species: succinic acid [HOOC(CH2)2COOH] < glutaric acid [HOOC(CH2)3COOH] < adipic acid [HOOC(CH2)4COOH] < azelaic acid [HOOC(CH2)7COOH]. With in situ ATR-FTIR analysis, most samples tend to have outer-sphere adsorption with the mineral surfaces at all tested pHs. However, inner-sphere coordination between the carboxyl groups and mineral surfaces at pH 4 was dominant from DRIFT analysis with freeze-dried complex samples. The complexation types, inner- or outer-sphere, depended on dicarboxylic acid species, pH, mineral surfaces, and solvent conditions. From the experimental data, we suggest that organic acids in an aqueous environment prefer to adsorb onto the test minerals by outer-sphere complexation, but inner-sphere complexation is favored under dry conditions. Thus, organic acid binding onto clay minerals under dry conditions is stronger than that under wet conditions, and we expect different conformations and aggregations of sorbed organic acids as influenced by complexation types. In the environment, natural organic material (NOM) may adsorb predominantly on positively charged mineral surfaces at the aqueous interface, which can convert into inner-sphere coordination during dehydration. The stable NOM/mineral complexes formed by frequent wetting-drying cycles in nature may resist chemical/microbial degradation of the NOM, which will affect carbon storage in the environment and influence the sorption of organic contaminants.

An in situ ATR-FTIR study on the adsorption of dicarboxylic acids onto kaolinite in aqueous suspensionsDedicated to Professor F. Dörr on the occasion of his 80th birthday.

ATR-FTIR spectroscopy was used to investigate in situ the adsorption of simple compounds, such as dicarboxylic acids, hydroxybenzoic acids and resorcinol, onto the clay mineral kaolinite. Identification of the absorption bands was based on changes which occur in the spectra of the compounds on changing the pH value of the aqueous solution. The band shifts which occur in the spectra of the dicarboxylic acids as a result of the interaction with the kaolinite surface suggest inner-sphere complexes, where either one or both oxygen atoms of the carboxylic group are bound to the kaolinite surface. A comparison of the spectra of the dicarboxylic acids showed that small structural differences had a great influence on the kind of surface complex formed. In the case of the hydroxybenzoic acids and resorcinol, the band shifts were too small to make any statements regarding possible surface complexes.

Chemisorption of Dicarboxylic Acids on an Si(111) Surface and Subsequent Chemical Reactions at the Surface of Adsorbed Molecular Layers

Adsorption of dicarboxylic acids [2-(trifluoromethyl)terephthalic acid and α,ω-dicarboxyperfluoroalkanes] from a solution onto a fluorine-terminated silicon(111) [Si(111)] surface was examined. X-ray photoelectron spectroscopy and Fourier transform infrared attenuated total reflection revealed that one carboxyl end covalently bonds to the Si surface, and the other end is exposed at the monolayer−air or monolayer−liquid interface. The reactivity of exposed carboxyl groups in the monolayer was confirmed by the fact that the surface species can be converted to chloroformyl groups by chlorination reagents.

Adsorption of dicarboxylic acids on lithiated nickel oxide electrode

Adsorption of dicarboxylic acids on lithiated nickel oxide electrode

Adsorption of dicarboxylic acids on lithiated nickel oxide electrode

Adsorption of dicarboxylic acids on NiO electrodes was studied by means of the galvanostatic transient method, mainly for oxalic acid. The oxalate or hydrogen oxalate anion or both were concluded to adsorb on the electrode. The adsorption was maximal at a potential less positive than the flat-band potential of the electrode, owing to preferential adsorption of hydroxyl anion in the region above the maximum adsorption potential. The quantity of adsorption was dependent on carrier concentration of the electrode, and high for the electrode of high carrier concentration. This phenomenon is connected to the charged condition of the electrode that when the maximum adsorption takes place, positively charged sites remain on the surface of the electrode which is charged negatively as a whole and the amount of the sites is much more different between the electrodes of different N than their bulk carrier concentrations. Adsorptions of malonic and succinic acid were distinctly low compared with that of oxalic acid. The adsorbability was in the order; oxalic acid>malonic acid>succinic acid. This order was in accord with the stability constants of nickel dicarboxylic acid chelates.

Hydrogen-bonding and adsorption of dicarboxylic acids by alumina

Adsorption of succinic acid and adipic acid by the alumina trihydrate, Alcoa C730, from aqueous solution has been studied. The results could be satisfactorily interpreted in terms of a parallel orientation of acid molecules on the adsorbent surface, but the acid molecules seem to be associated with some water molecules in the adsorbed phase. The acid molecules in the adsorbed phase are thus linked by hydrogen-bonding intermolecularly with other acid molecules or with adjacent water molecules, and not with surface hydroxyl groups as is the case with monocarboxylic acids.