Influence of Montmorillonite and Kaolinite on Tetracycline Adsorption

Batch equilibrium experiments were used to reveal tetracycline(TC)adsorption on two different mineral clays-montmorillonite and kaolinite. The experimental results showed that the adsorption isotherms were well described by Freundlich model. With the great variety of Kf values, tetracycline was adsorbed more strongly on montmorillonite than on kaolinite. In meantime, adsorption of TC on two clays decreased gradually with the increase of natural cation concentrations in solution, suggesting that the sorption process was largely dominated by cation exchange. Moreover, the different cations could result in the apparent difference of TC sorption when cations with higher valencies showed stronger adsorbilty on the surfaces of active sorption sites by the following order:M3(+Al3+)M2(+Ca2+)M(+K+). In addition, the sorption coefficients of tetracyclineed decreas with the increase of pH values within a range between 4.5 and 8.0.