Nano Sized Moringa oleifera an Effective Strategy for Pb(II) ions Removal from Aqueous Solution

Abstract

Nano-sized  Moringa oleifera is considered an effective   biosorbent  with  high surface area from agricultural waste, low coast and environment-friendly which can be used for removal of  Pb²⁺ from waste water. Thus our study stem to investigate the ability of natural nano-sized biosorbents for removing  very toxic Pb²⁺ ions from aqueous solution. The investigated biosorbent (Moringa oleifera) was characterized by FTIR, SEM, TEM, XRD and EDX techniques. Moreover, the influence of pH, temperature, adsorbent dosage, contact time and initial metal ion concentration on adsorption process were investigated. The maximum biosorption capacities (q_m) of Pb²⁺ ions by Moringa oleifera was 37.9 mg/g. The lowest biosorption was observed (61.4%) for Pb²⁺ ions at pH 2.0 while the highest one (94.36%) at pH 5. The optimum contact time for the adsorption process was found to be at 60 minutes. The amount of Pb²⁺ ions adsorbed increases with increasing in initial metal ion concentration. Moreover, biosorption capacity (q_e) and removal efficiency of Pb²⁺ ions solutions increase as temperature increases. FT-IR data indicated that the adsorption of metal ions occurs on the surface of Moringa oleifera powder as the main functional groups that are responsible for metal ions binding are involved in the process. Furthermore, Thermodynamic studies confirmed that the biosorption process was endothermic and the positive value of ΔG^° is quite common when an ion-exchan­­ge mechanism applies in the biosorption. The Positive value of ΔS^◦ suggested an increase in randomness during the biosorption. The kinetics study of sorption indicates that the pseudo second-order model provides better correlation of the sorption data (R²=0.99) than the pseudo first-order model (R² = 0.91), confirming the chemisorption of metal ions solutions on Moringa oleifera. The Freundlich isotherm has agood fit with the experimental data (R² close to 1) compared to Langmuir isotherm (R²=0.99). This study shows that Moringa oleifera are available, low cost, effective and environment friendlly biosorbent for the removal of Pb²⁺ ions from aqueous environment.

Keywords: Lead, biosorption, Thermodynamics, kinetics, removal efficiency, Moringa oleifera, isotherm