Fig 1.
Chemical structure of Rhodamine B.
Table 1.
The coded and un-coded levels of the independent variables.
Fig 2.
SEM images (a) Raw banana peel (b) Acid modified banana peel.
Fig 3.
FT-IR spectrum for a) raw banana peel b) acid modified banana peel c) banana peel after adsorption of RhB dye.
Table 2.
Regression coefficient for the adsorption of RhB and COD reduction and the significance of linear quadratic model.
Table 3.
Analysis of variance (ANOVA) of the quadratic model for removal of RhB and COD reduction onto banana peel.
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.
Interaction between process variables (a) RhB removal (b) COD reduction.
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.
Table 4.
Langmuir and Freundlich constants for the adsorption of RhB and COD reduction onto acid modified banana peel.
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).
Table 5.
Kinetic parameters for the adsorption of RhB and COD reduction onto acid modified banana peel at optimum condition.
Fig 8.
Schematic representation of adsorption mechanism of banana peel and its interaction with RhB.