Statistical modeling and mechanistic pathway for methylene blue dye removal by high surface area and mesoporous grass-based activated carbon using K₂CO₃activator

In this study, biomass of grass waste (GW) was utilized as sustainable precursor to produce highly porous activated carbon (GWAC) with mesoporosity using a K2CO3-assisted pyrolysis approach and tested for its methylene blue (MB) dye adsorption properties. The prepared GWAC was characterized using the various techniques of specific surface area (SSA), Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX), X-ray diffractometer (XRD), thermogravimetric analysis (TGA), and Fourier Transform Infrared (FT-IR) spectrophotometer. The characterization results indicate the successful conversion of GW into mesoporous GWAC with high and desirable surface area of 1245.6 m2/g. The adsorptive performance of GWAC towards MB uptake was evaluated. To attain higher performance of the activated carbon for MB adsorption, the adsorption key parameters such as GWAC dosage (A: 0.04-0.06 g/L), pH (B: 4-10), temperature (C: 30-60 °C), and time (D: 5-15 min) were optimized using the Box-Behnken design (BBD) method. The adsorption equilibrium data were accurately described by the Langmuir model, where the adsorption capacity (qm; 364.2 mg/g) was recorded at the optimized process temperature of 45 °C. The present research also examined the mechanisms associated with the removal of MB using GWAC and observed the contribution of various MB-GWAC surface interactions (e.g., electrostatic, π-π, and H-bonding interactions). The present investigation shows the utility and effectiveness of GW biomass based activated carbon due to its favorable mesoporosity and cationic dye uptake in aqueous media.