Utilization of Fennel biomass (Foeniculum vulgari) a medicinal herb for the biosorption of Cd(II) from aqueous phase

This work presents the biosorption potential of Fennel biomass for the effective removal of Cd(II) ions. The biosorption was maximum (92%) at pH 4.3. Maximum biosorption capacities of Cd(II) at 30, 40 and 50 °C temperatures were 21, 24 and 30 mg/g, respectively. The biosorption of Cd(II) was concentration dependent and increases from 0.49 to 9.3 mg/g with increase in concentration from 5 to 100 mg/L. Biosorption follows Freundlich isotherm at 50 °C. Mean free energies at different temperatures were in between 7.1 and 11.95 kJ/mol indicating chemical nature of biosorption process. Kinetics studies showed that pseudo-second-order kinetics model was applicable to the data. The process was endothermic and spontaneous, the spontaneity of the process increases with increase in temperature. Regeneration studies showed a decrease in the recovery of Cd(II) from 99.8% to 41.7% in five consecutive cycles. 80% of the Cd(II) in single and multi-metal systems was recovered in 10 mL. Breakthrough and exhaustive capacities of Cd(II) in single metal system were 10 and 40 mg/g. For multi-metal systems in double distilled water the breakthrough and exhaustive capacities of Cd(II) were 2 and 12 mg/g. In saline solution the breakthrough and exhaustive capacities of Cd(II) were 0.8 and 4 mg/g.