Sediment-Associated Reactions of Aromatic Amines. 1. Elucidation of Sorption Mechanisms

Abstract

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.

Simultaneous removal of phosphate and phenanthrene by alum aided with low amounts of surfactant‐modified bentonite

“…Phenanthrene and phosphate adsorption onto organobentonite It is commonly accepted that sorption of organic compounds onto organoclay utilizes partitioning (dissolution), 12,13 and the characteristic sorption isotherm is linear. 14 sorption on 0.1 CEC organobentonite showed a different type of isotherm, illustrated in Fig.…”

Kinetics of Rapid Covalent Bond Formation of Aniline with Humic Acid: ESR Investigations with Nitroxide Spin Labels

“…2001 8 found sorbed aniline fractions of 0.18 and 0.16 at pH = 6.82 and 7.37, respectively. They 306 attributed them to rapid covalent binding of the neutral form of aniline but could not determine 307 the rate constants.…”

“…Aromatic amines, e.g. aniline (aminobenzene), are the building blocks 50 of many pesticides, veterinary pharmaceuticals, textile dyes and other classes of synthetic 51 chemicals and comprise an important class of environmental contaminants [8]. They are also 52 reductive transformation products of nitro-aromatic explosives such as 2,4,6-trinitrotoluene 53 (TNT) and received a great deal of attention in remediation of contaminated manufacturing sites 54 [9 -11].…”

“…Laccase is known to catalyze the formation of covalent bonds by oxidizing unreactive 324 hydroquinone moieties in humic substances to electrophilic quinone moieties [6,8,23]. We thus 325 incubated LHA with extracellular fungal laccase from Agaricus bisporus for three days at room 326 temperature and mixed it with anilino-NO.…”

Effects of Copper on the Sorption of Phthalate Esters to Yellow River Sediment

“…Much attention has been paid on sorption processes of HOPs and heavy metals in solid-liquid systems. The sorption of HOPs is principally by partition and adsorption in which the organic carbon in sediment plays a dominant role (Chiou et al 1979;Weber et al 2001;Sun et al 2006), while the dissolved organic carbon (Laor et al 1998;Laor and Rebhun 2002) and aqueous ionic strength (Means 1995) are among the important environmental factors that affect the sorption equilibrium. For the sorption of heavy metals, adsorption, complexation and precipitation dominate the sorption mechanism, which is closely associated with sediment components such as iron and manganese oxides, organic carbon, carbonates and clay minerals (Sparks 2003;Bradl 2004).…”