High-Efficiency Adsorption of Methylene Blue by Balsa Wood Waste-Based Microporous Carbon

Biomass-based adsorbents for methylene blue (MB) currently face critical bottlenecks including raw material homogenization, insufficient adsorption capacity, and an unclear structure–activity relationship. To address these limitations, we prepared porous super activated carbon (SAC) with ultra-high specific surface area via KOH activation, using industrial balsa wood (Ochroma pyramidale) waste from the wind power industry as the precursor. The adsorption behavior and underlying mechanism of the as-prepared SAC towards MB were systematically investigated. The as-prepared SAC has an ultra-high specific surface area of 3833 m²/g, with a well-developed microporous structure matching the molecular size of MB. It exhibited a maximum monolayer MB adsorption capacity of 1037.76 mg/g, superior to similar biomass-based materials. Near-complete removal of high-concentration MB was achieved at an SAC dosage of 0.4 g/L, and the material maintained stable performance across a wide pH range of 4 to 10. The adsorption of MB onto SAC fitted well with the Langmuir isotherm and pseudo-second-order kinetic models, dominated by monolayer physisorption. The outstanding adsorption performance originated from the synergistic contribution of the pore confinement effect, π-π conjugation, electrostatic interaction, and hydrogen bonding. This work provides a new strategy for high-value utilization of balsa wood industrial waste and efficient treatment of dye wastewater.