Role of Interlayer Hydration in Lincomycin Sorption by Smectite Clays

Abstract

Lincomycin, an antibiotic widely administered as a veterinary medicine, is frequently detected in water. Little is known about the soil-water distribution of lincomycin despite the fact that this is a major determinant of its environmental fate and potential for exposure. Cation exchange was found to be the primary mechanism responsible for lincomycin sorption by soil clay minerals. This was evidenced by pH-dependent sorption, and competition with inorganic cations for sorptive sites. As solution pH increased, lincomycin sorption decreased. The extent of reduction was consistent with the decrease in cationic lincomycin species in solution. The presence of Ca2+ in solution diminished lincomycin sorption. Clay interlayer hydration status strongly influenced lincomycin adsorption. Smectites with the charge deficit from isomorphic substitution in tetrahedral layers (i.e., saponite) manifest a less hydrated interlayer environment resulting in greater sorption than that by octahedrally substituted clays (i.e., montmorillonite). Strongly hydrated exchangeable cations resulted in a more hydrated clay interlayer environment reducing sorption in the order of Ca- < K- < Cs-smectite. X-ray diffraction revealed that lincomycin was intercalated in smectite clay interlayers. Sorption capacity was limited by clay surface area rather than by cation exchange capacity. Smectite interlayer hydration was shown to be a major, yet previously unrecognized, factor influencing the cation exchange process of lincomycin on aluminosilicate mineral surfaces.

Kinetic Study of Denatonium Sorption to Smectite Clay Minerals

“…K d (L/g) increased by 76% to 1.26 L/g from 0.30 L/g as the ionic strength decreased from 733 mM to 2.66 mM. An abundance of literature exists supporting the contention that ion exchange processes are strongly influenced by ionic strength (Sparks, 1995;Wang et al, 2009;Yang et al, 2009). Consequently, we conclude that denatonium sorbs to the smectite surfaces in a cation exchange process, where inorganic cations are replaced by denatonium ions.…”

Emerging organic contaminants in groundwater: A review of sources, fate and occurrence

“…Casey et al, 2004;Wang et al, 2009;Olshansky et al, 2011) Comparatively low partitioning coefficients (Kd) <2 have been reported for adsorption to aquifer sediments (Scheytt et al, 2005). These findings may have important implications for ionic EOC fate during changes in major ion chemistry (e.g.…”

Organic xenobiotics removal in constructed wetlands, with emphasis on the importance of the support matrix

“…The amphiprotic character of silanol and aluminol groups in clays surfaces is responsible for a pH-dependent surface charge in clays (however, water molecules associated with exchangeable cations and clay surfaces may obscure these charged adsorption sites; such effect is dependent on the hydration strength of the exchangeable ions [170][171][172][173][174][175]). Electrostatic interactions with the surface and mechanisms such as cation exchange, cation bridging with the surface, surface complexation, and hydrogen bonding seem to be involved in the capture of ionic and polar species from aqueous media [121][122][123][124][125]176].…”