Premium
Oxytetracycline Sorption to Organic Matter by Metal‐Bridging
Author(s) -
MacKay Allison A.,
Canterbury Brian
Publication year - 2005
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2005.0014
Subject(s) - sorption , chemistry , humic acid , organic matter , ligand (biochemistry) , sorbent , inorganic chemistry , nuclear chemistry , ion exchange , environmental chemistry , organic chemistry , adsorption , ion , fertilizer , biochemistry , receptor
The sorption of oxytetracycline to metal‐loaded ion exchange resin and to natural organic matter by the formation of ternary complexes between polyvalent metal cations and sorbent‐ and sorbate ligand groups was investigated. Oxytetracycline (OTC) sorption to Ca‐ and Cu‐loaded Chelex‐100 resin increased with increasing metal/sorbate ratio at pH 7.6 (OTC speciation: 55% zwitterion, 45% anion). Greater sorption to Cu‐ than Ca‐loaded resin was observed, consistent with the greater stability constants of Cu with both the resin sites and with OTC. Oxytetracycline sorption to organic matter was measured at pH 5.5 (OTC speciation: 1% cation, 98% zwitterion, 1% anion). No detectable sorption was measured for cellulose or lignin sorbents that contain few metal‐complexing ligand groups. Sorption to Aldrich humic acid increased from “clean” < “dirty” (no cation exchange pretreatment) < Al‐amended < Fe(III)‐amended clean humic acid with K d values of 5500, 32000, 48000, and 250000 L kg −1 C, respectively. Calcium amendments of clean humic acid suggested that a portion of the sorbed OTC was interacting by cation exchange. Oxytetracycline sorption coefficients for all humic acid sorbents were well‐correlated with the total sorbed Al‐plus‐Fe(III) concentrations ( r 2 = 0.87, log‐log plot), suggesting that sorption by ternary complex formation with humic acid is important. Results of this research indicate that organic matter may be an important sorbent phase in soils and sediments for pharmaceutical compounds that can complex metals by the formation of ternary complexes between organic matter ligand groups and pharmaceutical ligand groups.