A comparison of microstructure and adsorption characteristics of activated carbons by CO2 and H3PO4 activation from date palm pits

This work attempts to compare the texture and the adsorption capacity of porous carbons prepared from date palm pits using CO2 and H3PO4 activation. The activation conditions were chosen based on the optimized parameters reported in the literature. The microstructure of the activated carbons was assessed based on nitrogen adsorption, SEM, and FT-IR, while the adsorption capacity was estimated using methylene blue (MB) adsorption. CO2 activation resulted in a microporous carbon with a yield of 44% and a BET surface area of 666 m2 · g-1, H3PO4 activation resulted in a mesoporous carbon with a yield of 14.8% and a BET surface area of 725 m2 · g-1. The average pore diameter of the activated carbons was estimated to be 1.51 and 2.91 nm for CO2 and H3PO4 activation respectively. The equilibrium adsorption isotherms for MB were fitted by the Langmuir and Freundlich models. The monolayer adsorption capacity of CO2 and H3PO4 activated carbons for MB from the Langmuir model were 110 and 345 mg · g-1 respectively under the optimized conditions. A highest MB adsorption capacity of 455 mg · g-1 was found for the H3PO4 activated carbon with a highest BET surface area.