Biosorption Potential of Vetiveria zizanioides for the Removal of Chromium(VI) from Synthetic Wastewater

Abstract

In the field of wastewater management, it is a challenging issue to develop a cost-effective and environment-friendly adsorbent for the removal of toxic metals. In this study, Vetiveria zizanioides was used as an active bioadsorbent for the removal of Cr(VI) using raw and chemically modified grasses and roots. Batch experiments were conducted using raw and modified bioadsorbents to observe the sorption behavior and to evaluate the performance parameters like pH of the solution, initial concentration, contact time, adsorbent dose, and the system temperature. Results showed that acidic-modified bioadsorbents [i.e., Vetiveria zizanioides grass (AVG) and roots (AVR)] exhibited the highest removal efficiency of Cr(VI) from the synthetic wastewater. Characterization studies were performed to examine the changes in morphology and functional groups of the activated carbon through a scanning electron microscope (SEM) and a Fourier transform infrared spectrometer (FTIR) including proximate and elemental analysis, Brunauer-Emmett-Teller (BET) surface area, and pHzpc. Kinetic parameters were determined to achieve equilibrium for the proposed biosorption process and mass transfer resistance was investigated for diffusion rate. Values of qcal, i.e., 16.1 and 17.915 mg/g suggested that a pseudo-second-order model was applicable. Adsorbate–adsorbent interaction was investigated by using Langmuir, Freundlich, and Dubinin-Radushkevich isotherms. Maximum adsorption capacity was observed to be 8.429 and 9.199 mg/g using raw Vetiveria zizanioides grass (RVG) and roots (RVR), respectively. Results obtained from thermodynamic study clearly stated that process is endothermic and spontaneous in nature.