Hydrochar was produced from hydrothermal treatment of corn straw black liquor. Response surface methodology (RSM) and the central composite design (CCD) were employed for determination of optimal char with maximum Pb2+ removal capacity. The operational parameters such as hydrothermal temperature (A degrees C), duration (min) and solid liquid ratio (LSR) were chosen as independent variables in CCD. The statistical analysis indicates that the effects of hydrothermal temperature, duration, LSR and combined effect of hydrothermal temperature and duration are all significant for the Pb2+ removal capacity. The optimal condition for achieving the maximum Pb2+ adsorption capacity is obtained as the following: hydrothermal temperature (205 A degrees C), duration (28min), LSR (12) with Pb2+ removal capacity reaching 47mg/g. The BET specific surface area of char prepared at optimal conditions could reach 85m(2)/g.