Extraction of Chromium (VI) from Polluted Waters Using Powders of Leaves and their Ashes of some Herbal Plants

The sorption potentialities of biosorbents derived from plant materials is one of the main areas of present research in pollution control methods. In the present work, leaves powders and their ashes of Croton tiglium and Cassia occidentalis, have been explored for this sorption properties towards Chromium(VI) ions. A thorough investigation has been made in optimizing the various physicochemical parameters such as equilibration time, pH and sorption dosage for the maximum extraction of Chromium(VI) from waste waters. Ten fold excess of common cation ions present in natural waters, viz., Ca²⁺, Mg²⁺ , Cu², Zn²⁺, Ni^{2 +} and Fe²⁺ are found to have synergistic effect in increasing the % removal of Chromium. Anions like Phosphate, SO4 ^2-and Carbonate are found to be interfering with the extractability of Chromates in the order: PO4 ^3- > SO4 ^2- > CO3 ^2-. Monovalent ions: NO3 ^- , Chloride, and Fluoride are found to have marginal interference. More than 90.0% extraction of Chromium (VI) is observed with the developed active sorbents. The methodologies developed are applied to real samples of industrial effluents and polluted lakes and found be remarkably successful.