Mesoporous activated carbon from Pentace species sawdust via microwave-induced KOH activation: optimization and methylene blue adsorption

This work studied the optimization of preparation conditions of Pentace species sawdust activated carbon (PSAC) via microwave-induced KOH activation for the adsorption of methylene blue (MB) dye from aqueous solutions. The produced activated carbon was characterised through Brunauer-Emmett-Teller (BET) surface area and pore structural analysis, proximate and ultimate, scanning electron microscopy, and Fourier transform infrared spectroscopy. Response surface methodology technique was used to optimize the radiation power, radiation time and impregnation ratio for MB removal and PSAC yield through central composite design. The optimum preparation conditions for PSAC were obtained at a radiation power of 418W, radiation time of 6.4min, and an impregnation ratio of 0.5, which resulted in 27% PSAC yield and 93.74% MB removal. A mesoporous structure of PSAC was formed, with a BET surface area, total pore volume and average pore diameter of 914.15m(2)/g, 0.52cm(3)/g, and 3.19nm, respectively. The experimental kinetic data were well described by a pseudo-second-order model and intraparticle diffusion. Adsorption data fitted the Redlich-Peterson equation better than the Langmuir, Freundlich, Temkin, Dubinin-Radushkevich and Sips equations. However, the exponential value of Redlich-Peterson approached unity, hence, resulting in the original Langmuir equation, with adsorption capacity of 357.14mg/g. The adsorption performance was effectively preserved even after four consecutive cycles, demonstrating good regeneration ability.