Biosorption of Pb(II) from contaminated water onto Moringa oleifera biomass: kinetics and equilibrium studies

The present study aims at evaluating a batch scale biosorption potential of Moringa oleifera leaves (MOL) for the removal of Pb(II) from aqueous solutions. The MOL biomass was characterized by FTIR, SEM, EDX, and BET. The impact of initial concentrations of Pb (II), adsorbent dosage, pH, contact time, coexisting inorganic ions (Ca2+, Na+, K+, Mg2+, CO32-, HCO3-, Cl-), electrical conductivity (EC) and total dissolved salts (TDS) in water was investigated. The results revealed that maximum biosorption (45.83mg/g) was achieved with adsorbent dosage 0.15g/100mL while highest removal (98.6%) was obtained at adsorbent biomass 1.0g/100mL and pH 6. The presence of coexisting inorganic ions in water showed a decline in Pb(II) removal (8.5% and 5%) depending on the concentrations of ions. The removal of Pb(II) by MOL decreased from 97% to 89% after five biosorption/desorption cycles with 0.3M HCl solution. Freundlich model yielded a better fit for equilibrium data and the pseudo-second-order well described the kinetics of Pb(II) biosorption. FTIR spectra showed that -OH, C-H, -C-O, -C=O, and -O-C functional groups were involved in the biosorption of Pb(II). The change in Gibbs free energy (G = -28.10kJ/mol) revealed that the biosorption process was favorable and thermodynamically driven. The results suggest MOL as a low cost, environment-friendly alternative biosorbent for the remediation of Pb(II) contaminated water.