Adsorption of Sulfonamide Antimicrobial Agents to Clay Minerals

Abstract

Adsorption of three sulfonamide antimicrobials to clay minerals was investigated as a function of pH, ionic strength, and type of exchangeable cation. Sulfonamide antimicrobial adsorption exhibited pronounced pH dependence consistent with sorbate speciation and clay properties. Sulfonamide antimicrobials did not intercalate into montmorillonite, and surface charge density influenced sorption by determining adsorption domain size. Adsorption edge data were best fit to a model including terms for the cationic and uncharged species. Adsorption of uncharged sulfamethazine to montmorillonite was relatively insensitive to pH, ionic strength, and type of exchangeable cation, while that to kaolinite was highly sensitive to ionic strength. Adsorption of cationic sulfamethazine to montmorillonite exceeded that of the neutral species by 1-2 orders of magnitude, but was unimportant for kaolinite atthe pH values examined. Cation exchange appeared to contribute to sorption of cationic sulfonamide species to montmorillonite. Anionic sulfamethazine adsorption was negligible. The nature of the sulfonamide R group influenced the degree of adsorption of cationic and neutral species. Our results highlight the importance of considering sulfonamide speciation and clay surface charge density in predicting the transport of these antimicrobials.

Effects of Sorbate Speciation on Sorption of Selected Sulfonamides in Three Loamy Soils

“…In general, at a lower pH, sorption of sulfonamides is enhanced primarily due to cation exchange of predominantly cationic forms of the adsorbate (17). Conversely, the observed reduction in the K D values at high pH could be attributed to the shift from cationic to anionic species of the sulfonamides, which are unavailable for cationic exchange or neutral adsorption into soil organic matter.…”

Joint antibacterial activity of soil-adsorbed antibiotics trimethoprim and sulfamethazine

“…Recent studies have reported that sulfonamides and diaminopyrimidines showed low sorption to soils (Leal et al, 2013;Sanders et al, 2008;Srinivasan et al, 2013;Thiele-Bruhn et al, 2004). H-bonding, cation bridging, ion-exchange, surface complexes and hydrophobic partition have been shown to be the main sorption mechanisms for sulfonamides (Gao and Pedersen, 2005;Kahle and Stamm, 2007;Leal et al, 2013). However, very few studies have investigated co-sorption of sulfonamides and diaminopyrimidines which are often used together.…”

Sorption of endrin to montmorillonite and kaolinite clays

“…As can be seen, an increase in ionic strength results in an increase in the sorption for both montmorillonite and kaolinite. The increase of sorption with the increase in the ionic strength maybe is due to the fact that solution ionic strength influences the double layer thickness of clays [23]. The addition of salt results in the compression of the diffuse double layer and facilitates the interaction between endrin molecules and clay surface.…”