Adsorptive removal of hazardous crystal violet dye onto banana peel powder: equilibrium, kinetic and thermodynamic studies

Abstract

In this study, banana peel powder (BPP) was used to remove carcinogenic crystal violet (CV) dye from aqueous solution. The BPP adsorbent was characterized by Fourier-Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM). In batch sorption experiments, the maximum removal of CV was recorded 93% at optimum levels of operating parameters, i.e., pH 7.0, adsorbent dosage 0.1 g, contact time 10 min, initial adsorbate concentration 90 ppm and temperature 20 ${}_{\mathrm{ }}{}^{\mathrm{o}}\mathrm{C}.$ The kinetics of the adsorption process was found best to follow the pseudo first order model with high value of ${\mathrm{R}}^2$ (0.9999) and low values of error functions. The Langmuir isotherm model was the best fit with high ${\mathrm{R}}^2$ (0.9552) low values of error models. The plots of Freundlich and D-R isotherms confirmed the feasibility ($\mathrm{n}\mathrm{ }$= 1.3109 ${\text{L g}}^{-1}$) and the physisorption nature (${\mathrm{E}}_{\mathrm{s}}$= 0.1107 ${\text{kJ mol}}^{-1}$) of the process respectively. The negative values of thermodynamic parameters $(\Delta \mathrm{G}$ & $\Delta \mathrm{H})$ revealed that the adsorption was spontaneous and exothermic in nature respectively. The results of the desorption study showed that 91% of the adsorbent was regenerated. The novelty of the present research is that no work has been reported till date to remove crystal violet dye by using banana peel specifically. The high adsorption and desorption efficiencies (>90%) suggest that BPP possesses characteristics to be used as an effective, fast and low-cost adsorbent for adsorption of CV dye from industrial effluents.

HIGHLIGHTS

• Adsorption technique was employed to remove crystal violet dye by using banana peel powder.

• The hydroxyl (${\mathrm{\text{OH}}}^{-}$) & carboxylate (${\mathrm{\text{OH}}}^{-}$) groups on adsorbent surface provided excellent binding with adsorbate molecules.

• Equilibrium attainment in 10 min at neutral pH.

• 93% adsorption and 91% desorption.

Graphical Abstract

Keywords:

• Adsorption
• desorption
• error analysis
• mechanism
• safe disposal

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