Biochars were produced from celery biomass by slow pyrolysis at 350 and 500 degrees C, and featured by high content of alkaline minerals namely salts of alkali and alkaline earth metals. The biochars' efficiency on removing Pb2+ from solution was investigated, and two biochars derived from celery stalk (StC350 and StC500) showed higher Pb2+ sorption capacity (288 and 304 mg/g) than most biochars reported previously. The sorption mechanisms involving precipitation, cation exchange and surface complexation are related to three biochar fractions namely water-soluble matter, acid-soluble substances and insoluble organic carbon. The relative contributions of water-soluble matter and acid-soluble substances to the total Pb2+ removal were 59.8% and 36.6% for the StC350 biochar, and 62.8% and 34.9% for the StC500 biochar, respectively. The results indicate that biochars derived from vegetable wastes are potential candidates for efficient sorption of heavy metals. (C) 2017 Elsevier Ltd. All rights reserved.