Optimization of Cd(II), Cu(II) and Ni(II) biosorption by chemically modified Moringa oleifera leaves powder

A cation exchange biosorbent was developed by chemically modifying the Moringa oleifera leaves powder by esterifying with NaOH followed by citric acid treatment. The modified biosorbent was characterized by FTIR, SEM and XRD techniques and was used for the removal of Cd(II), Cu(II) and Ni(II) from aqueous solution. Different operational parameters such as the effect of pH, biomass dose, equilibrium time and temperature and initial metal ion concentrations were studied. Experimental data were analyzed by kinetic parameters and found that biosorption of three metal ions followed pseudo-second-order. Equilibrium data were analyzed using the Langmuir, Freundlich, Dubinin–Radushkevich and Temkin isotherm models. The thermodynamic properties, ΔG°, ΔH° and ΔS° showed that biosorption of Cd(II), Cu(II) and Ni(II) onto CAMOL were spontaneous, endothermic and feasible in the temperature range of 293–313 K. Furthermore, the CAMOL can be regenerated and reused for the metal removal.