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Mobility of toxic metals, originating from natural or anthropogenic sources, from soil to groundwater is a matter of utmost concern to human health. Remediation of the contaminated groundwater is of the highest priority as groundwater is an alternate source of freshwater that is used all over the world for drinking purpose. Hence, in the present study, Pteris vittata L. is used as a simple, biodegradable and efficient biosorbent of toxic metals in its non-living and pelletized form by employing organic binders and a simple manual pellet press. The capacity of the pelletized Pteris vittata L. to sequester the metals Cd(II) and Cr(VI) from an aqueous solution is determined through the study on the effect of operating conditions, isotherm and kinetic models. The metal removal capacity of the biosorbent pelletized using corn starch as the binder is 13.51 mg/g for Cd(II) at pH 6 and 1.66 mg/g for Cr(VI) at pH 2 as obtained from the Langmuir isotherm model. The diffusion of the metal ions into the micropores of the pellets aids its biosorption. Physical adsorption, ion exchange, covalent bonding and complexation are deduced to be few of the biosorption mechanisms involved. The findings contribute to the existing data in the biosorption technology. The novelty lies in the use of a weedy fern, Pteris vittata L., pelletized with desired structural characteristics as a potential low-cost biosorbent of toxic metals from groundwater.

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Biosorption is a surface-dependent phenomenon. Surface modifications by chemical treatment methods could either improve or reduce the biosorption capacity of potential biosorbents. In the present work, pristine Pteris vittata L. pinnae (PPV) powder was treated separately with sodium hydroxide (NaOH), calcium chloride (CaCl), and nitric acid (HNO). The pristine and treated biosorbents were used to assess the biosorption of Pb(II), Cd(II), and Cr(VI) as a function of pH. Kinetics and adsorption isotherms were studied. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and scanning electron microscope combined with energy dispersive x-ray (SEM-EDX) spectroscopic techniques were used to characterize the biosorbents before and after chemical treatments. The possible functional groups contributing to the metal sorption were identified. Results revealed favorable biosorption of Pb(II), Cd(II), and Cr(VI) described by pseudo-second order kinetics. NaOH-treated P. vittata (NPV) showed higher biosorption capacity for Pb(II) and Cd(II) compared to that of PPV. ATR-FTIR studies indicated that -OH, -COOH, and -NH groups were mainly involved in Cr(VI) and -OH in Pb(II) and Cd(II) biosorption. The enhanced efficiency of NPV and CaCl treated P. vittata (CPV) in the uptake of Pb(II) and Cd(II) compared to PPV can be associated with their altered physicochemical characters.