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 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.