Sequestration of methylene blue dye from aqueous solution using microwave assisted dragon fruit peel as adsorbent

Abstract

Activated carbon (AC) was prepared from dragon fruit peel (DFP) for methylene blue (MB) dye removal from an aqueous system. The physicochemical activation technique involving chemical treatment using potassium hydroxide, CO2 gasification, and microwave heating techniques were used. Brauner–Emmet–Teller surface area and pore volume of the prepared from DFP activated carbon (DFPAC) were 725.80 m2/g and 0.388 cm 3/g, respectively. SEM images revealed that the prepared DFPAC poses an heterogeneous surface. The FTIR spectra revealed several important functional groups (including the hydroxyl OH, alkane CH, and alkene C≡C) on the surface of DFPAC. Proximate and elemental analysis showed remarkable increase in fixed carbon contents and elemental carbon from 11.38 to 70.11% and 25.6 to 73.36% for DFP and DFPAC, respectively. The MB-DFPAC adsorption system was best explained by Freundlich isotherm with a adsorption capacity of approximately 233 mg/g. The kinetic study showed that the pseudo-second order model best described the adsorption of MB-DFPAC systems. Thermodynamic investigations established an exothermic and spontaneous nature of MB-DFPAC systems with a decreased randomness at the solid–liquid interface, and the mechanism followed physisorption. DFPAC proved to be an excellent adsorbent for Methylene blue dye removal.