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The removal of BTEX (benzene, toluene, ethyl-benzene and p-xylene) from contaminated groundwater was evaluated by paper mill sludge-based activated carbon, prepared by chemical activation and pyrolysis. The effects of pH, time, adsorbent dosage and adsorbate concentration were studied through batch adsorption experiments. Selected physical and chemical characteristics of the adsorbents, such as specific surface area (613m2/g), pore volume distribution (micropore: 277cm3/g, mesopore: 365cm3/g) and surface functional groups (carboxylic, alkyl and aliphatic groups) were determined by N2 adsorption-desorption diagram and FTIR, respectively. The removal efficiency of the four target compounds would be more than 92%, which the initial concentrations of BTEX and the adsorbent dosage were 40 mg/l and 1000 mg/l, respectively. It was proved that pH and ionic strength have insignificant effects on the adsorption efficiency. The order of adsorption amount in all experiments was> ethyl-benzene> toluene> benzene. The kinetic data proved a closer fit to the pseudo-first-order model. The isotherm experimental data showed a better fit to either Freundlich or Langmuir model. In addition, a series of experiments was conducted to evaluate the capacity of the adsorbent in adsorbing the BTEX from a groundwater sample contaminated with gasoline.