Cephalexin (CFX) antibiotic, a potent pharmaceutical water pollutant, was efficiently removed by activated carbon (AC) derived from a single-step pyrolysis of phosphoric acid-activated chitin. Experimental conditions such as temperature, CFX initial concentration, and solution pH were screened in batch adsorption. Phosphoric acid activation of chitin and subsequent pyrolysis tailored the Brunauer-Emmett-Teller surface area, total pore volume, and average pore diameter to 1199.02 m(2)/g, 0.641 cm(3)/g, and 21.37 angstrom, respectively. The Langmuir isotherm adequately described the equilibrium data for CFX adsorption on chitin-AC, with an R(2 )of 0.99 and a monolayer capacity of 245.19 mg/g at 50 degrees C. Chitin-AC showed higher adsorption capacity compared with other ACs derived from industrial and agricultural precursors. When activated by phosphoric acid, chitin-AC featured functional multi-sites for vast antibiotic adsorption treatment. Overall, chitin-AC could be a promising adsorbent for removal of CFX.