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SORPTION OF SULFONAMIDE ANTIMICROBIALS TO CLAY AND NATURAL ORGANIC MATTER
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Paper number 701P0104, . (doi: 10.13031/2013.15833)Authors: J. Gao, J. A. Pedersen
Keywords: Sulfonamides, antimicrobial agent, adsorption, smectite, FTIR, HPLC, XRD
Sulfonamide antimicrobial agents are among the most commonly prescribed human drugs in the United States. After administration, they may be excreted as the unaltered parent compounds and acetylated metabolites in the urine and feces. Although the efficiency of on-site waste disposal systems for these compounds has not been investigated, conventional sewage treatment processes are ineffective in eliminating sulfonamide antimicrobials from wastewater. This suggests that septic system leach fields may represent a source of sulfonamide antimicrobial agents to the subsurface environment. The bioavailability and mobility of antimicrobial agents depends on their sorption to inorganic and organic soil constituents. We investigated the association of three sulfonamide antimicrobial agents with smectite clay and an organic soil. Sorption to both clay minerals and natural organic matter was relatively weak, suggesting that sulfonamides are mobile in subsurface environments. Sorption was strongly pH dependent with maximum sorption observed at proton activities at which the neutral species dominated sulfonamide speciation. Anionic species of sulfonamides did not appear to interact significantly with smectite clay surfaces. At high aqueous concentrations, the nature of the cation in the smectite exchange complex appeared to strongly influence the strength of adsorption for sulfamethazine but not for sulfamethoxazole or sulfapyridine.
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