High surface area and mesoporous activated carbon from KOH-activated dragon fruit peels for methylene blue dye adsorption:Optimization and mechanism study

In this study, an alternative precursor for production of activated carbon was introduced using dragon fruit (Hylocereus costaricensis) peel (DFP). Moreover, KOH was used as a chemical activator in the thermal carbonization process to convert DFP into activated carbon (DFPAC). In order to accomplish this research, several approaches were employed to examine the elemental composition, surface properties, amor-phous and crystalline nature, essential active group, and surface morphology of the DFPAC. The Brunauer-Emmett-Teller test demonstrated a mesoporous structure of the DFPAC has a high surface area of 756.3 m2·g-1. The cationic dye Methylene Blue (MB) was used as a probe to assess the efficiency of DFPAC towards the removal of MB dye from aqueous solution. The effects of adsorption input factors (e.g. DFPAC dose (A: 0.04–0.12 g·L-1), pH (B: 3–10), and temperature (C: 30–50 ℃)) were investigated and optimized using statistical analysis (i.e. Box–Behnken design (BBD)). The adsorption kinetic model can be best categorized as the pseudo-first order (PFO). Whereas, the adsorption isotherm model can be best described by Langmuir model, with maximum adsorption capacity of DFPAC for MB dye was 195.2 mg·g-1 at 50 ℃. The adsorption mechanism of MB by DFPAC surface was attributed to the electro-static interaction,π-πinteraction, and H-bonding. Finally, the results support the ability of DFP to be a promising precursor for production of highly porous activated carbon suitable for removal of cationic dyes (e.g. MB).