Facile synthesis of micro-mesoporous activated carbon in ambient air via one and two - stage activation of palm kernel shell waste for methylene blue adsorption

Abstract

ABSTRACT The primary objective of this study was to discover the effects of one – and two-stage activation process on the synthesis and methylene blue (MB) adsorption performance of palm kernel shell-derived activated carbon using KOH as activator in ambient air. The two-stage process can produce a higher yield of porous carbon materials (PKSAC) in contrast to the one-stage process (RPKSAC). Significant differences in morphology, textural properties, organic structure and crystallinity of prepared activated carbons were observed. BET findings show that PKSAC had a higher specific surface area (1298 m2/g) and pore volume (0.58 cm3/g) with numerous micropores compared to RPKSAC (surface area: 1160 m2/g and Pore volume: 0.48 cm3/g), this may be attributed to reaction nature between activator and precursor as temperature increases, which determines the pore-forming path way. Moreover, PKSAC (MB adsorption capacity = 417 mg/g) absorbs 62 mg/g more than RPKSAC (MB adsorption capacity = 355 mg/g) due to its excellent surface textural property and oxygen-containing functional groups on the surface. Furthermore, Langmuir model fits the adsorption behaviour of PKSAC/MB adsorption system. The dye adsorption mechanism was dominated with physical, electrostatic, π–π and hydrogen bonding interactions. Thermodynamic parameters indicated that, the MB adsorption on the prepared activated carbon was spontaneous and endothermic. In conclusion, these results demonstrate that two-stage activation process enhances the adsorption ability of activated carbon, proving palm kernel shells as viable for activated carbon production.