NH4Cl-induced activated carbon (NAC) was investigated for its adsorption potential to remove diazinon pesticide from contaminated water. Tests were done to evaluate the effects of solution pH, NAC concentration, contact time, water impurities and solution temperature on adsorption of diazinon onto NAC. Results showed that the maximum adsorption rate was 97.5% of 20 mg/L diazinon, adsorbed onto NAC at a low solution concentration of 0.3 g/L and short contact time of 30 min at neutral pH. The effect of adding NaCl to the diazinon solution caused a slight reduction in humic acid, and ammonia nitrogen slightly improved the adsorption process. Diazinon adsorption process improved at the temperature range of 25-35 degrees C. The experimental adsorption data had the best fitness with the pseudo-second-order model. Equilibrium adsorption data could be better fitted with the Langmuir isotherm. The maximum adsorption capacity of diazinon on NAC, calculated by the Langmuir model, was determined at 250 mg/g. In addition, diazinon-contaminated surface water could be effectively treated using a relatively low concentration of NAC, 10 mg/L and in a short contact time of 30 min. Overall, the use of NAC demonstrated efficiency and can be presented as a promising adsorbent to eliminate the pesticide from contaminated streams. (C) 2012 Elsevier B.V. All rights reserved.