Comparative performance of fruit peel materials for methylene blue dye adsorption

The recycling fruit wastes of banana, pomelo, and mangosteen as biosorbents for eliminating methylene blue dye (MBD) were investigated in this study by synthesizing 3 materials of banana (Musa ABB cv. Kluai ‘Namwa’) powder beads (BPB), pomelo (Citrus maxima (Burm.f.) Merr) powder beads (PPB), and mangosteen (Garcinia mangostana Linn) powder beads (MPB) and characterizing with several techniques. Their MBD adsorption performances were examined by a series of batch experiments, desorption experiments, adsorption isotherms, kinetics, and thermodynamics studies. MPB had a higher specific surface area and pore volume than BPB and PPB, whereas its pore size was smaller than theirs. All materials had amorphous structures. BPB had rough surfaces, whereas PPB had coarse surfaces with layer structures. MPB had rough surfaces with irregular shapes. They consisted of carbon, oxygen, calcium, chloride, and sodium. The chemical functional groups of hydroxyl, methine, carbonyl, and ether were detected in all materials. The pH_pzc of BPB, PPB, and MPB were 5.41, 5.00, and 5.05. MPB showed a higher MBD removal efficiency of 98.92% and adsorption capacity (q_e) of 6.59 mg/g than BPB and PPB, and all materials could be reused for 3 cycles with the adsorption efficiency of more than 61%. Their adsorption patterns and mechanisms were described by Freundlich and pseudo-second-order kinetic models. BPB and MPB were endothermic processes, whereas PPB was an exothermic process.

Graphical abstract