Sorption characteristics of veterinary antibiotics chlortetracycline on manure

The sorption characteristics of high-use tetracycline veterinary antibiotics-chlortetracycline(CTC) on pig manure and chicken manure were investigated in laboratory according to the OECD guideline 106.The results showed that CTC was strongly and rapidly adsorbed to the two manures and Freundlich model could describe preferably the CTC nonlinear sorption isotherms.The adsorbed CTC was difficult to be desorbed by rain with desorption H of 1.522 for pig manure and 1.329 for chicken manure,respectively.Only 18.3%-20.4%,18.7%-19.4% and 55.7%-57.6% adsorbed CTC were desorbed by methanol,3(mol/L) NaCl and 3(mol/L) MgCl_2.The sorption of CTC on manure were affected by solution pH and ionic strength,the amount of adsorbed CTC on manure decreased with an increase of pH value and ionic strength,and greater sorption effect in the Ca systems than the Na systems was observed.These results suggest that organic matter and cation exchange mainly contribute to the sorption of CTC on manure.