Biosorption of Pb(II) from aqueous solutions using chemically modified Moringa oleifera tree leaves

Moringa oleifera leaves (MOL); an agro-waste material has been used as a precursor to prepare a new biosorbent. The leaves were washed with base and citric acid, and obtained new chemically modified MOL biosorbent (CAMOL) for sequestration of Pb(II) from aqueous solution. The biosorbent was characterized by SEM, FTIR spectral and elemental analyses. The effect of experimental parameters such as pH, dose, initial concentration, contact time and temperature on the biosorption was studied. The kinetic data were analyzed using three adsorption kinetic models: the pseudo-first and second-order kinetics and intraparticle diffusion. The equilibrium data were analyzed using Langmuir, Freundlich, Dubinin–Radushkevick and Temkin isotherm models. Langmuir model provided the best correlation with biosorption capacity of 209.54 mg g−1 at 313 K. The thermodynamic properties, ΔG°, ΔH° and ΔS° showed that biosorption of Pb(II) onto CAMOL was spontaneous, endothermic and feasible in the temperature range of 293–313 K. Desorption experiments showed feasibility of regeneration of the biosorbent for further use after treating with dilute HCl. The presence of other common metal ions like Na+, K+, Ca2+ and Mg2+ did not affect the biosorption of lead. Investigations carried out proved that CAMOL is a biosorbent with good potential for removal of lead from the aqueous media.