Biosorption of Pb(II) onto Cocos Nucifera Shell and Moringa Oleifera Seeds

Abstract

The biosorption properties of Cocos nucifera shell and Moringa oleifera seeds for Pb(II) were investigated under batch mode. The optimum pH values obtained for the removal of Pb(II) by the Cocos nucifera shell and the Moringa oleifera seeds were 5 and 2, respectively. The equilibrium biosorption capacities obtained were 2.3 mg g−1 (Moringa oleifera seeds) and 1.6 mg g−1 (Cocos nucifera shell). The Freundlich isotherm model described the removal of Pb(II) by the biosorbents better than the Langmuir model. The Cocos nucifera shell sorbed 83.34% of the Pb(II) ions in 30 min, while 94.03% was sorbed by the Moringa oleifera seeds in the same time. The results indicated a fast kinetics for Pb(II) sorption by the biosorbents investigated. The biosorption of Pb(II) onto Cocos nucifera shell and Moringa oleifera seeds followed the pseudo second-order kinetics with R² values of 0.9997 and 0.9999, respectively. The second-order rate constant (k₂) obtained were 0.205 g mg⁻¹ min⁻¹ (Cocos nucifera shell) and 0.067 g mg⁻¹ min⁻¹ (Moringa oleifera seeds). The results indicate that intraparticle diffusion controls the rate of biosorption in this study. This study shows that Cocos nucifera shell and Moringa oleifera seeds can be important low-cost biosorbents for Pb(II) ions.

Keywords:

• Agricultural waste
• Biosorption
• Kinetics
• Mathematical modeling
• Metal removal
• Sorption

Acknowledgments

The authors are grateful to the Department of Chemical Engineering, Kumasi Polytechnic, Ghana for providing laboratory and secretarial facilities to undertake this research work. We wish to thank AngloGold Ashanti, Obuasi mine in Ghana for providing us with laboratory facility to conduct a part of this research. We are particularly thankful to the manager of the Environmental Department, Mr. Owusu Yeboah, for his guidance and technical support.