Screening of agricultural waste for Ni(II) adsorption: Kinetics, equilibrium and thermodynamic studies

This study reports the adsorption of Ni(II) ions onto waste powders prepared from egg plant (EGP), sweet potato (SWP) and banana peels (BNP). The influence of adsorption parameters, such as pH, contact time, adsorbent weight, adsorbate concentration and temperature were investigated. Equilibrium was described by the Langmuir and Freundlich models. Ni(II) uptake was very fast reaching a maximum within 20 min of adsorbent contact with metal solution. Comparison of removal capacities for EGP, SWP and BNP indicated that EGP was more effective in removing Ni(II) from aqueous solution. The kinetic data fitted the pseudo second order model. Thermodynamic parameters ΔH and ΔS were negative which suggest that adsorption process was spontaneous. The results of Fourier transform infrared (FTIR) indicated several binding and chelating ions, such as carboxyl, carbonyl and hydroxyl groups on the biomaterials surfaces were responsible for Ni(II) adsorption.