Biosorptive removal of nickel(II) ions from aqueous solutions by hass avocado (Persea Americana mill. Var. Hass) shell as an effective and low-cost biosorbent

This research work describes the utilization of Hass avocado shell (HAS), i.e., a waste material generated in large quantities from the fruit consumption, to detoxify and remove divalent nickel [Ni(II)] ions from aqueous solutions via bio-sorption. Batch studies reveal that the Ni(II) bio-sorption capacity of HAS is dependent on operating variables, such as solution pH, contact time and initial Ni(II) concentration. Ni(II) biosorption increases with increasing solution pH, shaking contact time and initial metal concentration. The Ni(II) biosorption kinetics is well described by the pseudo-second order model, whereas the Langmuir isotherm model best describes the Ni(II) equilibrium biosorption data. The Langmuir isotherm model predicts a maximum biosorption capacity of 126.3 mg g1, which adequately matches the experimental value of Ni(II) biosorption capacity at equilibrium (107.26 mg g2), and a biosorption equilibrium constant of 0.0124 L mg3, which indicates that the biosorption of Ni(II) ions onto HAS is favorable. Fourier transform infrared spectroscopy (FTIR) shows that the carboxyl and aromatic functional groups on the HAS surface could be the potential biosorption sites for Ni(H) biosorption. The present study proves that HAS can be used as an effective, low-cost and eco-friendly biosorbent to remediate Ni(II)-contaminated water and wastewater.