Evaluation of Cr(VI) Exposed and Unexposed Plant Parts of Tradescantia pallida (Rose) D. R. Hunt. for Cr Removal from Wastewater by Biosorption

Abstract

Phytoremediation is an efficient method for the removal of heavy metals from contaminated systems. A productive disposal of metal accumulating plants is a major concern in current scenario. In this work, Cr(VI) accumulating Tradescantia pallida plant parts were investigated for its reuse as a biosorbent for the removal of Cr(VI) ions. The effect of pH, contact time, sorbent dosage, Cr(VI) concentration and temperature was examined to optimize these process parameters. Results showed that Cr(VI) exposed/unexposed T. pallida leaf biomass could remove 94% of chromium with a sorption capacity of 64.672 mg g⁻¹. Whereas the kinetics of Cr(VI) biosorption was well explained by the pseudo second-order kinetic model, the Langmuir model better described the data on Cr(VI) sorption isotherm compared with the Freundlich model. The changes in the free energy (ΔG°), entropy (ΔS°) and enthalpy (ΔH°) were found to be −5.276 kJ mol⁻¹, 0.391 kJ mol⁻¹ K⁻¹ and 11.346 kJ mol⁻¹, respectively, which indicated the process to be spontaneous, feasible and endothermic in nature. FTIR spectra of T. pallida leaf biomass revealed the active participation of ligands, such as −NH, amide, hydroxyl and sulphonate groups present in the biomass for Cr(VI) binding, SEM analysis revealed a porous structure of the biosorbent for an easy uptake of Cr(VI).

Keywords::

• chromium(VI) removal
• Tradescantia pallida
• pseudo second-order kinetics
• Langmuir isotherm
• thermodynamics
• FTIR

Acknowledgments

The authors thank the Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, for providing the necessary facilities to carry out this research work. The authors also thank the Central Instrumentation Facility, IIT Guwahati, for FESEM analysis.