Kinetics, biochemical and factorial analysis of chromium uptake in a multi-ion system by Tradescantia pallida (Rose) D. R. Hunt

ABSTRACT

Discharge of wastewater from electroplating and leather industries is a major concern for the environment due to the presence of toxic Cr⁶⁺ and other ions, such as sulfate, nitrate, phosphate, etc. This study evaluated the potential of Tradescantia pallida, a plant species known for its Cr bioaccumulation, for the simultaneous removal of Cr⁶⁺, SO₄²⁻, NO₃⁻, and PO₄³⁻. The effect of different co-ions on Cr⁶⁺ removal by T. pallida was examined following the Plackett-Burman design of experiments carried out under batch hydroponics conditions. The results revealed a maximum removal of 84% Cr⁶⁺, 87% SO₄²⁻, 94% NO₃⁻ and 100% PO₄³⁻ without any phytotoxic effect on the plant for an initial Cr⁶⁺ concentration in the range 5–20 mg L⁻¹. SO₄²⁻ and NO₃⁻ enhanced Cr uptake at a high initial Cr concentration (20 mg L⁻¹), whereas PO₄³⁻ did not affect Cr uptake both at high and low initial Cr concentrations. The Cr⁶⁺ removal kinetics in the presence of different ions was well described by the pseudo-second-order kinetic model which revealed that both biosorption and bioaccumulation of the metal played an important role in Cr⁶⁺ removal. Increase in the total carbohydrate and protein content of the plant following Cr⁶⁺ and co-ions exposure indicated a good tolerance of the plant toward Cr⁶⁺ toxicity. Furthermore, enhancement in the lipid peroxidation and catalase activity in T. pallida upon Cr⁶⁺ exposure revealed a maximum stress-induced condition in the plant. Overall, this study demonstrated a very good potential of the plant T. pallida for Cr⁶⁺ removal from wastewater even in the presence of co-ions.

KEYWORDS:

• antioxidant enzymes
• chromium(VI) removal
• Co-ions
• kinetics
• Plackett–Burman
• Tradescantia pallida

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.