Abstract
The discharges of dye-containing wastewater have predominantly been attributed to the textile industry, where methylene blue (MB) is the most commonly-used dye. The use of graphene-based adsorbents with sugar as the natural carbon source has been reported as a new milestone; however, the sustainability of entailing sugar in such engineering practices is questionable. Considering the generation of agricultural waste from palm oil mills in the context of Malaysia and the need of more sustainable carbon sources for the synthesis of graphene-based adsorbents, this study explored the synthesis of graphene shell composite (GSC), a new generation of graphene-based adsorbents, with oil palm frond (OPF) juice as the natural carbon source and with oil palm kernel shell as the base material. The synthesized GSC was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The adsorption performance was evaluated by studying the effect of synthetic MB solution concentration and the GSC mass. 75.45%–99.13% removal of MB ions from synthetic MB solution after 20 h of adsorption performance study suggested the applicability and effectiveness of the synthesized GSC in treating dye-containing wastewater. Further kinetics analysis revealed that the interactions between GSC and MB ions fitted the Freundlich isotherm (R2 = 0.9631-0.9689) and pseudo-second order isotherm (R2 = 0.9860-0.9980). Such findings reflect that the uptake of MB ions by GSC was mechanistically a multilayer adsorption, in which the MB ions approached the active sites on GSC surfaces and were continually adsorbed thereon through chemical bonding.