Aquatic macrophytes for the effective remediation of hexavalent chromium from aqueous media in Continuous up-flow column

Abstract

A continuous up-flow column mode was employed using dried powder of Lemna gibba, a gibbous duckweed for the biosorptive remediation of hexavalent chromium from aqueous solution. Breakthrough curves under different flow rates and bed heights were used to study sorption performance of the biosorbent. The maximum Cr(VI) removal efficiency of 65.32 mg/g corresponding to 84.18% obtained at a flow rate of 2 mL min⁻¹ and bed height of 19 cm. The Bed Depth Service Time (BDST) model showed to be well agreeing with the experimental data (R² > 0.995). Desorption and regeneration studies showed that the biosorbent retained its adsorption efficiency well under three consequtive sorption-desorption cycles indicating good reusabilty and operational stability. Charaterization of the biosorbent was done before and after adsorbent using SEM, TEM, EDAX and XRD. While SEM and TEM showed noticiable modifications in surface after adsorption, EDAX confirmed the presence of Cr on the surface, and XRD further confirmed the surface structural changes, confirming its adsorption onto the biosorbent.