The objective of this research is to produce high surface area-activated carbon derived from cotton linter fibers by fused NaOH activation and to examine the feasibility of removing oxytetracycline (OTC) from aqueous solution. The cotton linter fibers activated carbon (CLAC) was characterized by N-2 adsorption/desorption isotherms, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The results showed that CLAC had a predominantly microporous structure with a large surface area of 2143 m(2)/g. The adsorption system followed pseudo-second-order kinetic model, and equilibrium was achieved within 24 h. The equilibrium data were described well by Langmuir isotherm. Thermodynamic study showed that the adsorption was exothermic reaction at low concentration and became endothermic nature with the concentration increasing. Competitive adsorption took place in the weakly acidic to neutral conditions. Under the strong acidity or strong alkaline condition, the adsorption of the oxytetracycline was hindered by electrostatic repulsion. The adsorption mechanism depended on the pH of the solutions as well as the pK(a) of the oxytetracycline. (C) 2011 Elsevier Inc. All rights reserved.