Experimental investigation and mathematical modeling of physical activated carbon preparation from pistachio shell

•Taguchi’s experimental design was used in pyrolysis stage of pistachio shell to char.•In activation stage of pistachio shell char by steam, a mathematical modeling approach was used.•A changing structural parameter and overlapped random pore model was applied.•Model predictions were compared with experimental BET surface areas successfully.

The present work deals with a complete study on activated carbon production from physical activation of pistachio shell. The effect of different parameters was investigated in the pyrolysis stage (at 400–700 °C) and also activation stage (at 800–950 °C) of the preparation process for activated carbon. Parameters including particle size, carbonization temperature, heating rate, holding time, and the N2 flow rate were studied in the pyrolysis stage; and activation temperature and activation time were studied in the steam activation stage. Taguchi’s experimental design was used in the pyrolysis stage for analysis of the experimental data and results optimization. The pyrolysis temperature of 600 °C, heating rate of 20 °C/min, 1 h hold time, with N2 flow rate of 100 mL/min were the best conditions to produce a char with 350 m2/g. In the activation stage with steam, a mathematical modeling approach was used and the effects of operating temperature and reaction time were studied. The mathematical model is based on modification of a single pore model for estimation of pore growth rate, using a population balance equation, and applying a changing structural parameter overlapped random pore model. The model predictions were compared with the experimental BET surface areas and solid conversions at various times with good agreement. Finally, the activation energy of 126 kJ/mol was estimated for pistachio shell char activation by steam between 800 and 950 °C.