Conversion of a mixture of date palm wastes to mesoporous activated carbon for efficient dye adsorption

In this study, we aimed to develop mixture activated carbon (MAC) from a mixture of date palm wastes (petiole, rachis and fiber) through hydrothermal carbonization and microwave-assisted H _3 PO _4 activation and evaluate its adsorption capacity to remove Remazol brilliant blue R (RBBR) from aqueous solution. The MAC was found to be mesoporous, with an average pore diameter and BET surface area of 2.61 nm and 641.23 m ^2 g ^−1 , respectively. The zeta potential and FTIR results demonstrated that the surface of MAC was negatively charged in its natural state and filled with functional groups such as phenyl, secondary amine, alkyne, aldehyde, and hydroxy groups. The adsorption capacity and percentage removal of RBBR increased and decreased, respectively, when the initial concentration increased. Maximum removal of RBBR was achieved at pH 3 (96.69 mg g ^−1 ) and at 30 °C of solution temperature (85.79 mg g ^−1 ). Langmuir and pseudo-first-order were the best isotherm and kinetic models for describing the RBBR-MAC adsorption system, respectively. The thermodynamic parameters of ΔH°, ΔS°, ΔG°, and E _a implied that this adsorption system was exothermic, increased randomness at the liquid-solid interface, and was spontaneous and controlled by the physisorption type of sorption, respectively.