Sorption Of Aniline Research Articles

Role of pH in partitioning and cation exchange of aromatic amines on water-saturated soils

Predicting the reversible interactions between aromatic amines and soil is essential for assessing the mobility, bioavailability and exposure from contaminated sites. Reversible sorption mechanisms of aniline and α-naphthylamine were investigated by using single and binary solute sorption to five soils at several pH values, and by applying a distributed parameter (DP) model. The DP model assumes linear partitioning of the neutral species into soil organic matter domains and organic cation binding on negative-charged sites with the exchange coefficients represented by a Gaussian probability distribution. Sorption nonlinearity was attributed to cation exchange with varying site affinities, which was adequately simulated using the DP model. Greater uptake by hydrophobic partitioning and selectivity for cation exchange sites was observed for α-naphthylamine compared to aniline. Sorption of α-naphthylamine was not impacted quantitatively by aniline under those conditions examined; however, aniline sorption was reduced by α-naphthylamine with the largest reduction occurring in the soil with the lowest pH. DP model simulations showed that although hydrophobic partitioning increases with soil–solution pH, cation exchange still contributes significantly to the total sorption even at soil–solution pH values greater than p K a+2.

Sediment-associated reactions of aromatic amines. 1. Elucidation of sorption mechanisms.

Sorption of aromatic amines to sediments and soils can occur by both reversible physical processes and irreversible chemical processes. To elucidate the significance of these sorption pathways, the sorption kinetics of aniline and pyridine were studied in resaturated pond sediment. Aniline and pyridine behaved quite differently in the sediment-water systems. The sorption kinetics of pyridine were quite fast, reaching equilibrium within 1-2 h. In contrast, the sorption kinetics of aniline were characterized by a rapid initial loss of aniline from the aqueous phase followed by a much slower rate of disappearance. The rapid initial sorption of aniline upon respiking after an equilibration period of 200 h, and results of sorption kinetic studies as a function of substrate concentration, demonstrated that sorptive sites were not being saturated at the nominal concentration of aniline. Sequential extraction of a sediment treated with 14C-labeled pyridine and aniline suggested that pyridine was bound primarily through a reversible cation-exchange process, whereas aniline sorbed through both cation-exchange and covalent binding processes. At longer reaction periods sorption became increasingly dominated by covalent binding. The reaction kinetics for the slow, irreversible sorption of aniline appeared to be limited by the reactivity and/or availability of covalent binding sites. The initial rate and extent of aniline sorption was pH dependent (sorption increased with decreasing pH). At pH values above the pKa of aniline, sorption kinetics for the slower, irreversible loss of aniline were independent of pH.

Solvent effect on the sensitivity and selectivity of determining aniline and toluidines in the air by piezoelectric microweighing

Batch conditions were optimized for the sorption of aniline and toluidines from the air on polystyrene, polyethyleneglycol-2000, and polyethyleneglycol succinate using piezoelectric microweighing. It was found that the analytical signal of a quartz crystal resonator depended on the mass of the modifier on the electrode surface and on the solvent. The selectivity of modifiers with respect to the compounds studied was estimated.

Detecting aniline in air in systems based on piezoelectric quartz crystal resonators modified with poly(ethylene glycol succinate) under static and dynamic conditions

The optimal conditions have been found for aniline sorption on a film of poly(ethylene glycol succinate) by the piezoelectric quartz crystal microbalance method using bulk acoustic wave sensors based on AT-cut quartz crystals under static and dynamic conditions. The dependence of the analytical signal of the quartz crystal resonator on the modifier film mass, the volumetric flow rate of the carrier gas (air), and the sorption temperature has been investigated.

Sorption of Ionizable Organic Solutes by Surfactant-Modified Zeolite

We determined the sorption of ionizable organic solutes on a natural zeolite modified with hexadecyltrimethylammonium (HDTMA), a cationic surfactant. The sorption of benzene and its ionizable analogues phenol and aniline by surfactant-modified zeolite (SMZ), prepared at different HDTMA surface coverages, was affected by solution pH. All of the sorption isotherms were linear and could be described by a distribution coefficient (Kd). At neutral pH, the Kd values of benzene, phenol, and aniline on SMZ increased with HDTMA loading up to monolayer coverage of 100 mmol/kg. Beyond monolayer coverage, further increases in HDTMA loading did not increase the Kd values of the solutes at pH 7.0, where all species exist primarily in their neutral forms. The Kd values were consistent with the relative octanol−water partition coefficients of the three compounds, indicating that sorption of the neutral species was primarily by partitioning into the bound HDTMA organic pseudophase. Phenol sorption by SMZ treated to bilayer coverage increased as the pH, and hence fraction of anionic phenolate, increased. The counterion balance indicated that the increased retention of phenol was due partially to anion exchange of phenolate for bromide, the same mechanism responsible for sorption of inorganic anions by SMZ. In contrast, decreases in pH resulted in reduced aniline sorption due to a lower concentration of the neutral species and repulsion of the positively charged anilinium from SMZ treated to bilayer coverage. The results demonstrate that sorption of target species can be maximized by tailoring the HDTMA surface coverage to account for species and solution characteristics.

Use of Cetyltrimethylammonium Bromide-Bentonite To Remove Organic Contaminants of Varying Polar Character from Water

Cetyltrimethylammonium bromide (CTMAB)-bentonite was produced by the exchange of cetyltrimethylammonium (CTMA) cations for inorganic ions on the internal and external surfaces of bentonite. CTMAB-bentonite was used to remove organic contaminants of varying polar character from water. The properties and mechanisms for CTMAB-bentonite to sorb benzene, toluene, ethylbenzene, nitrobenzene, aniline, phenol, and p-nitrophenol in water were investigated in some detail. Benzene, toluene, and ethylbenzene sorption to CTMAB-bentonite was characterized by linear isotherms, indicating solute partition between water and the organic phase composed of the large alkyl functional groups of the CTMA cations. Phenol and p-nitrophenol sorption to CTMAB-bentonite was caused primarily by adsorption with relatively strong solute uptake. Their isotherms were nonlinear. Nitrobenzene and aniline sorption to CTMAB-bentonite was weak, and the isotherms were approximately linear. Their sorption was caused by both partition and solute uptake. The sorption data were also evaluated in terms of the octanol−water partition coefficients of the organic compounds.

Initial sorption of aromatic amines to surface soils

AbstractSorption of aniline, α‐naphthylamine, and benzidine to three silty clay loams was measured from CaCl, electrolyte solutions in single and binary solute systems after a 1‐d residence time. Soils varied in pH (4.4–7.2), cation‐exchange capacity (CEC, 10–30 cmolc/kg), and organic carbon content (OC, 1–3%). Plots of sorbed amine concentrations versus aqueous amine concentrations exhibited nonlinearity in the concentration range investigated. Sorption increased with decreasing soil‐solution pH for all solutes. Decreases in sorption with increasing CaCl2 concentrations were greatest at low pH. In binary solute experiments, α‐naphthylamine depressed the sorption of aniline and this depression increased with decreasing pH. Normalizing sorption to the cation‐exchange capacity of the protonated species compensated for most of the differences observed between soils at different pH values suggesting that cation exchange is the primary process occurring during initial contact times. In selected experiments, sorbed aromatic amines were extracted from soils with different solvents after a 1‐d incubation. At low initial concentrations (<0.01 mM) only a few percent of each amine was extractable; whereas 85% to 98% was recoverable at higher initial concentrations (1 mM). Although initial sorption appears to be to cation‐exchange sites, the inability to recover all of the sorbed amine suggests early covalent bond formation on highly reactive sites and/or sorption to high‐energy sites on clays or other soil constituents.

INITIAL SORPTION OF AROMATIC AMINES TO SURFACE SOILS

Sorption of aniline, α-naphthylamine, and benzidine to three silty clay loams was measured from CaCl, electrolyte solutions in single and binary solute systems after a 1-d residence time. Soils varied in pH (4.4–7.2), cation-exchange capacity (CEC, 10–30 cmolc/kg), and organic carbon content (OC, 1–3%). Plots of sorbed amine concentrations versus aqueous amine concentrations exhibited nonlinearity in the concentration range investigated. Sorption increased with decreasing soil-solution pH for all solutes. Decreases in sorption with increasing CaCl2 concentrations were greatest at low pH. In binary solute experiments, α-naphthylamine depressed the sorption of aniline and this depression increased with decreasing pH. Normalizing sorption to the cation-exchange capacity of the protonated species compensated for most of the differences observed between soils at different pH values suggesting that cation exchange is the primary process occurring during initial contact times. In selected experiments, sorbed aromatic amines were extracted from soils with different solvents after a 1-d incubation. At low initial concentrations (<0.01 mM) only a few percent of each amine was extractable; whereas 85% to 98% was recoverable at higher initial concentrations (1 mM). Although initial sorption appears to be to cation-exchange sites, the inability to recover all of the sorbed amine suggests early covalent bond formation on highly reactive sites and/or sorption to high-energy sites on clays or other soil constituents.

Interactions of aniline with soil and groundwater at an industrial spill site.

The interactions of aniline with soil at an industrial spill site were investigated. Sorption of aniline to the soil was observed to occur through a two-step mechanism. The first step was an ion exchange process with the protonated amine serving as an organic cation. This step was influenced by solution pH and ionic composition. The second step was covalent bonding most likely with quinone moieties and oxidation with polymerization of aniline. The extent of covalent bonding was influenced by the presence of oxygen and redox potential. The majority of aniline that was bound to the soil did not readily desorb under a variety of abiotic conditions. However, aniline was released to a significant extent in the presence of denitrifying and methanogenic microbial activity. Aniline in aqueous solution was readily biodegradable under aerobic and denitrifying conditions. Soil-bound aniline was observed not to be biodegradable. This paper provides an overview of results.

SORPTION OF ANILINE ON SELECTED ALFISOLS FROM THE EASTERN COAL REGION

The sorptive behavior of aniline was investigated in two Alfisols from eastern coal regions. Batch adsorption/desorption studies (soil/solution ratio 1:5, aniline concentration 25 to 400 ..mu..g/ml) were performed on the prominent genetic horizons of each soil. Sorption was evaluated as a function of equilibrium pH and ionic strength (Na/sub 2/SO/sub 4/) of the supporting electrolyte and on selected horizons treated to remove organic materials (H/sub 2/O/sub 2/ oxidation) and secondary iron components (oxalate and DCB-extractable). The behavior of aniline in the B horizons was concentration-dependent, and at higher concentrations (>75 ..mu..g/ml) sorption exceeded that of the upper or A horizons and was reversible. Aniline sorption was pH-dependent, reflecting different mechanisms and sites of sorption in the A and B horizons. Binding of aniline in the A horizons was greater below the compound pKa; maximum sorption in B horizons occurred above the pKa. Sorption in the A horizon was controlled primarily by partially irreversible interaction with organic materials; the high degree of sorption in the lower horizons may have resulted from proton transfer reactions and binding of the anilinium ion to interlayer areas of phyllosilicate minerals. 39 references, 5 figures, 2 tables.

Sorption of Aniline by Montmorillonite

AbstractSorption of aniline by montmorillonite was studied by infra‐red, X‐ray diffraction and differential thermal analysis methods. The amount of aniline sorbed and the type of bonding depend upon the interlayer cations: anilinium, H+‐ and Al3+‐ give anilinium aniline ions, NH44‐ammonium aniline ions, alkalis and alkaline earths except Cs are bonded to aniline through water bridges and transition metal cations are coordinated to aniline partly directly and partly through water bridges. Sorption does not occur in the complete absence of water.