Preparation of porous carbon from date palm seeds and process optimization

The agricultural wastes like date palm seeds to be a suitable precursor for the preparation of porous carbon has been explored in the present work, utilizing phosphoric acid as the activating agent. The experimental methods reported in literature were chosen with certain modification in order to simplify the process. The process optimization was performed using the popular response surface methodology adopting a Box-Behnken design. Process optimization was performed to maximize the porous carbon Brunauer–Emmett–Teller (BET) surface area and the methylene blue (MB) adsorption capacity, with the process variables being the activation temperature, impregnation ratio (IR) and the activation time. The textural characteristics were assessed based on nitrogen adsorption isotherms, scanning electron microscopy, while the adsorption capacity was estimated using the MB adsorption. The optimized experimental conditions were identified to be an activation temperature of 500 °C, IR of 3.1 and activation time of 71.4 min, with the resultant porous carbon having BET surface area of 846.7 m²/g and MB adsorption capacity of 445.7 mg/g. The popular Langmuir and Freundlich adsorption isotherm models were tested, and a maximum monolayer adsorption capacity of the MB was estimated to be 345 mg/g, which compares with the highest of MB reported in literature, evidencing the suitability of the porous carbon for adsorption of macro-molecular compounds.