Microwave-assisted preparation of mesoporous-activated carbon from coconut (Cocos nucifera) leaf by H3PO4 activation for methylene blue adsorption

Mesoporous-activated carbon was prepared from fallen coconut (Cocos nucifera) leaf, an agricultural waste through a microwave-induced H3PO4 activation process. The characterization of the coconut leaf-activated carbon (CAC) was evaluated through the iodine number, ash content, bulk density, and moisture content. Fourier transform infrared spectroscopy, scanning electron microscope, Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction, and pH(PZC). CAC has a mesopore content of 84% with an average pore size of 36.5 angstrom and a large BET surface area of 632m(2)/g. The uptake properties of the CAC with methylene blue was evaluated at different CAC dosage levels (0.2-10g/L), initial pH (3-10), methylene blue concentration (50-350mg/L), and time (0-360min) using batch mode operation. The kinetic profiles were described by the pseudo-second-order kinetics. The equilibrium data were well fitted to the Langmuir model with a maximum monolayer adsorption capacity of 250mg/g at 30 degrees C. Thermodynamic functions indicate a spontaneous and exothermic nature of the adsorption process. This study indicates that coconut leaves are a promising renewable precursor that can be utilized to develop an efficient mesoporous-activated carbon.