Carboxylate-functionalized dragon fruit peel powder as an effective adsorbent for the removal of Rhodamine B (cationic dye) from aqueous solution: adsorption behavior and mechanism

Abstract

In this study, we used a simple and low-toxicity chemical treatment to make a carboxylate-functionalized dragon fruit peel powder (CF-DFPP) from dragon fruit peel to improve its capacity for adsorbing Rhodamine B (RhB) from an aqueous medium. Field Emission-Scanning Electron Microscopy/Energy-Dispersive X-ray (FE-SEM/EDX), point of zero charges (pH_PZC), Brunauer-Emmett-Teller (BET), and Fourier Transform Infrared (FT-IR) analyses were performed to characterize the adsorbent materials. The adsorption performance and mechanism for the removal of RhB were examined. The kinetic, isotherm and thermodynamic parameters were employed to evaluate the adsorption mechanism. Compared to other models, the Langmuir isotherm and PSO kinetic models better defined the experimental data. CF-DFPP adsorbent exhibited a maximum adsorption efficiency of 228.7 mg/g at 298 K for RhB adsorption. Thermodynamic analysis revealed that the adsorption of RhB by CF-DFPP was spontaneous (ΔG^o < 0) and exothermic (ΔH^o < 0) nature of the process. Different eluting agents were used in desorption tests, and NaOH was revealed to have greater desorption efficiency (96.8%). Furthermore, regeneration examinations revealed that the biosorbent could effectively retain RhB, even after six adsorption/desorption cycles. These findings demonstrated that the CF-DFPP might be a novel material for removing RhB from an aqueous medium.

Graphical Abstract

Novelty statement: To improve the efficiency of adsorbing Rhodamine B (RhB) from aqueous streams, a low-toxic carboxylate-functionalized (CF) dragon fruit peel powder sorbent material was synthesized. Following the chemical transfer, the surface area of DFPP was increased dramatically from 4.49 to 23.6 m²/g, resulting in a higher adsorption efficiency and reusability than previously reported. The choice of the CF significantly increases the number of anions and attracts the positively charged RhB, increasing the sorption tendency. Despite the abundance of material on the direct use of dragon fruit peel as an adsorbent, no research has been done on the adsorbent surface modification. As a result, an effort has been made to add a novel adsorbent to the adsorbents database in this approach.

Keywords:

• Adsorption
• dragon fruit peel
• mechanism
• regeneration
• rhodamine B

Additional information

Funding

The authors would like to acknowledge the research support from MOST 107-2625-M-224-002, MOST 108-2625-M-224-005, and MOST 110-2625-M-224-001, by the Ministry of Science and Technology (MOST), Taiwan.