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. 2019 May 15;14(5):e0216878.
doi: 10.1371/journal.pone.0216878. eCollection 2019.

Adsorption of Rhodamine B dye from aqueous solution onto acid treated banana peel: Response surface methodology, kinetics and isotherm studies

Adeleke Abdulrahman Oyekanmi  1 , Akil Ahmad  1 , Kaizar Hossain  1 , Mohd Rafatullah  1
Affiliations

Adsorption of Rhodamine B dye from aqueous solution onto acid treated banana peel: Response surface methodology, kinetics and isotherm studies

Adeleke Abdulrahman Oyekanmi et al. PLoS One. .

Abstract

The adsorption of rhodamine B (RhB) using acid modified banana peels has been examined. Chemical characteristics of the adsorbents were observed in order to determine active functional groups. The major functional groups on the surface were OH, C = O, C = C and C-O-C. Interactions between operational parameters were studied using the central composite design (CCD) of response surface methodology (RSM). The predictions of the model output indicated that operational factors influenced responses at a confidence level of 95% (P<0.05). The optimum conditions for adsorption were pH 2 at a 0.2 g/L dose within 60 minutes of contact time. Isotherm studies were carried out using the optimized process variables. The data revealed that RhB adsorption fitted the Langmuir isotherm equation while the reduction of COD followed the Freundlich isotherm. Kinetic experiments fitted the pseudo second order model for RhB removal and COD reduction. The adsorption mechanism was not the only rate controlling step. Diffusion through the boundary layer described the pattern of adsorption.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Chemical structure of Rhodamine B.
Fig 2
Fig 2. SEM images (a) Raw banana peel (b) Acid modified banana peel.
Fig 3
Fig 3. FT-IR spectrum for a) raw banana peel b) acid modified banana peel c) banana peel after adsorption of RhB dye.
Fig 4
Fig 4. Three dimensional response surface for illustrating the adsorption of a) RhB removal onto banana peel b) COD reduction onto banana peel.
Fig 5
Fig 5. Interaction between process variables (a) RhB removal (b) COD reduction.
Fig 6
Fig 6. Adsorption isotherms for RhB and COD by acid modified banana peel at 28 °C (a) Langmuir isotherms for RhB and COD (b) Freundlich isotherms for RhB and COD.
Fig 7
Fig 7. Kinetic studies for RhB adsorption and COD reduction onto acid modified banana peel (a) Pseudo first order kinetics for RhB and COD (b) Pseudo second order kinetics for RhB and COD (c) Elovich kinetic study for RhB and COD (d) Intraparticle transport for RhB and COD (Experimental conditions: Adsorbent mass 3.5 g/ 50 ml, temperature = 28 °C, pH 2, agitation speed = 150 rpm).
Fig 8
Fig 8. Schematic representation of adsorption mechanism of banana peel and its interaction with RhB.
See this image and copyright information in PMC

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