Tropical fruit wastes including durian seeds and rambutan peels as a precursor for producing activated carbon using H₃PO₄-assisted microwave method: RSM-BBD optimization and mechanism for methylene blue dye adsorption

Abstract

Herein, tropical fruit biomass wastes including durian seeds (DS) and rambutan peels (RP) were used as sustainable precursors for preparing activated carbon (DSRPAC) using microwave-induced H₃PO₄ activation. The textural and physicochemical characteristics of DSRPAC were investigated by N₂ adsorption-desorption isotherms, X-ray diffraction, Fourier transform infrared, point of zero charge, and scanning electron microscope analyses. These findings reveal that the DSRPAC has a mean pore diameter of 3.79 nm and a specific surface area of 104.2 m²/g. DSRPAC was applied as a green adsorbent to extensively investigate the removal of an organic dye (methylene blue, MB) from aqueous solutions. The response surface methodology Box–Behnken design (RSM-BBD) was used to evaluate the vital adsorption characteristics, which included (A) DSRPAC dosage (0.02–0.12 g/L), (B) pH (4–10), and (C) time (10–70 min). The BBD model specified that the DSRPAC dosage (0.12 g/L), pH (10), and time (40 min) parameters caused the largest removal of MB (82.1%). The adsorption isotherm findings reveal that MB adsorption pursues the Freundlich model, whereas the kinetic data can be well described by the pseudo-first-order and pseudo-second-order models. DSRPAC exhibited good MB adsorption capability (118.5 mg/g). Several mechanisms control MB adsorption by the DSRPAC, including electrostatic forces, π–π stacking, and H-bonding. This work shows that DSRPAC derived from DS and RP could serve as a viable adsorbent for the treatment of industrial effluents containing organic dye.

NOVELTY STATEMENT

The novelty of this research work comes from the conversion of the mixed biomass wastes from tropical fruit including durian seeds and rambutan peels as precursor for activated carbon (DSRPAC) using microwave assisted H₃PO₄ activation. The effectiveness of DSRPAC as promising adsorbent was tested for methylene blue (MB) dye adsorption. Furthermore, response surface methodology with Box Behnken design (RSM-BBD) was applied to optimize the adsorption key parameters. A tailored adsorption mechanism of MB on the surface of DSRPAC was proposed.

Keywords:

• Activated carbon
• activation
• adsorption
• durian seeds
• H₃PO₄
• methylene blue
• rambutan peels
• response surface methodology

Acknowledgments

The authors thank the faculty of applied sciences for the research facilities. The author (Zeid A. ALOthman) is grateful to the Researchers Supporting Project No. (RSP2023R1), King Saud University, Riyadh, Saudi Arabia.

Disclosure statement

No potential conflict of interest was reported by the author(s).