High surface area activated carbon with mesoporous structure from pyrolyzed Psidium guajava L. peel: Characterization and experimental design optimization for methyl violet 2B dye removal

Abstract

Herein, guava (Psidium guajava L.) peel (GP) was employed as a feedstock to produce a mesoporous and high surface area activated carbon (GP-AC) material by thermochemical pyrolysis process assisted ZnCl₂ activation. Several characterization methods such as XRD, specific surface area (BET), TGA FSEM-EDX, FTIR, and pH_pzc were employed to investigate the physicochemical properties of GP-AC. The BET result shows a high surface area of GP-AC (1267 m²/g) with a mesoporous structure and pore diameter (3.41 nm). The applicability of GP-AC as a sustainable adsorbent for methyl violet 2B (MV 2B) dye was evaluated and statistically optimized via Box Behnken design (BBD) and desirability function approach. The desirability ramp reveals the best MV 2B removal (97.2 %) was achieved after 17 min of the adsorption time, pH of 9.3 and GP-AC dose of 0.09 g/0.1L. According to the adsorption isotherm and kinetic investigations, the adsorption of MV 2B onto GP-AC surface was well explained by Langmuir and Freundlich isotherm models, and pseudo second order (PSO) respectively. The adsorption capacity of GP-AC adsorption for MV 2B dye was found to be 169.9 mg/g at 25 °C. The thermodynamic functions indicate a spontaneous and endothermic adsorption process for MV 2B dye by GP-AC. Various electrostatic forces, π-π attraction, and hydrogen bonding can be considered the most probable options for loading MV 2B dye onto GP-AC surface. Overall GP-AC shows preferable surface area and outstanding performance in eliminating MV 2B dye from the contaminated water.