Biosorption of Vanadium (V) and Chromium (VI) using abscised coconut leaves powder: Equilibrium and continuous packed bed column studies

The presence of heavy metals such as Vanadium (V) and Chromium (VI) in industrial waste are detrimental and toxic to our agricultural systems. Strategies involving the removal of heavy metals from industrial waste are the need of the hour. A low-cost biosorbent using abscised coconut leaves (ACL) was employed for successful biosorption of toxic heavy metals, namely Vanadium and Chromium from industrial waste in this study. The zeta potential, BET surface area, SEM, EDAX, XRD, FTIR characterization of ACL powder was carried out. Maximum adsorption capacities of 46.95 mg·g⁻¹ for V (V) and 40.33 mg·g⁻¹ for Cr (VI) was observed. Equilibrium studies demonstrated that 98 % Vanadium (V) was removed at pH 2 for a sorbent dosage of 10 g·L⁻¹ and 100 mgLl⁻¹ of initial metal ion concentration, whereas 99 % Chromium (VI) was removed at pH 1 for a sorbent dosage 10 g·L⁻¹ and 100 mg·L⁻¹ of initial metal ion concentration. Zeta potential studies further confirmed the involvement of anionic adsorption mechanism for biosorption of heavy metals. Column studies were further carried out to study effect of bed height, metal ion concentration and flow rate. The Yoon Nelson model was found to be the best fit for the breakthrough curve data. Furthermore, the experimental data was also tested for Bed Depth Service Time model, which is useful for the scale up of the process. Considering the abundance of this biosorbent and simple method of preparation, ACL powder can be considered as a promising cost-effective option for heavy metal removal from water.