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

Discharge of wastewater from electroplating and leather industries is a major concern for the environment due to the presence of toxic Cr ⁶⁺ 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 Cr ⁶⁺ , SO ₄ ^2- , NO ₃ ^- , and PO ₄ ^3- . The effect of different co-ions on Cr ⁶⁺ 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% Cr ⁶⁺ , 87% SO ₄ ^2- , 94% NO ₃ ^- and 100% PO ₄ ^3- without any phytotoxic effect on the plant for an initial Cr ⁶⁺ concentration in the range 5-20 mg L ^-1 . SO ₄ ^2- and NO ₃ ^- enhanced Cr uptake at a high initial Cr concentration (20 mg L ^-1 ), whereas PO ₄ ^3- did not affect Cr uptake both at high and low initial Cr concentrations. The Cr ⁶⁺ 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 Cr ⁶⁺ removal. Increase in the total carbohydrate and protein content of the plant following Cr ⁶⁺ and co-ions exposure indicated a good tolerance of the plant toward Cr ⁶⁺ toxicity. Furthermore, enhancement in the lipid peroxidation and catalase activity in T. pallida upon Cr ⁶⁺ exposure revealed a maximum stress-induced condition in the plant. Overall, this study demonstrated a very good potential of the plant T. pallida for Cr ⁶⁺ removal from wastewater even in the presence of co-ions.