Abstract Adsorption and desorption of flumequine (fluoro quinolone) on kaolinite, and the effects of pH, electrolyte, polyelectrolyte and polymers on adsorption are reported. Adsorption of flumequine in acid medium is of a specific nature and even the presence of ions (phosphate) and polymers which have a high affinity towards kaolinite did not alter adsorption. It is suggested that adsorption occurs in two stage, an initial rapid stages resulting from strong interactions, followed by a slower stage due to either diffusion or molecular rearrangement. The amount of adsoption varied with pH. At low pH, adsorbed flumequine is difficult to desorb by reducing the concentration of the adsorbate in the solution (i.e., adsorption was almost irreversible with respect to concentration). However, at constant high pH (> 6.0) adsorption seems to be reversible. Adsorption is found to be completely reversible to changes in pH. Variation in the solubility of flumequine (affinity with water) and variation in the amount of adsorption on kaolinite with pH are found to be related.