Abundant porous biochar derived from luffa vine for removal of methylene blue: Selective adsorption and mechanistic studies

The recycling of biomass from agriculture and forestry wastes can realize high-value utilization of waste and preparation of new biosorbent material for dyeing wastewater purification. In this study, the natural luffa vine (LV) waste, with abundant pore structure and high lignin content, was used to develop a novel LV-derived activated biochar (LVAC) with high adsorption capacity and superior selectivity toward methylene blue (MB) from wastewater through a simple one-step carbonization method. The obtained LVAC possessed big pore volume (0.6455 cm3·g−1) and large specific surface area (1075.17 m2·g−1). Importantly, benefiting from the multi-level porous structure and abundant exposed active sites, LVAC demonstrated a large adsorption capacity of 559.11 mg·g−1 toward MB, surpassing that of the majority of previously reported activated carbon. The behavior characteristics of MB adsorption fitted both Freundlich model and pseudo-second order (PSO) model, which was mostly ascribed to the synergistic effect among pore-filling, hydrogen bonds, electrostatic interactions, and π–π interactions. The removal efficiency of LVAC toward MB remained 83 % after eight adsorption–desorption cycles, indicating its excellent recyclability. This study demonstrates the significant potential of LVAC as a candidate for efficient MB removal.