Melia azedarach Activated Carbon for Heavy Metals Removal: Isotherm, Kinetic and Response Surface Methodology Study

Muhammad, Imran-Shaukat and Rafeah, Wahi and Zainab, Ngaini (2023) Melia azedarach Activated Carbon for Heavy Metals Removal: Isotherm, Kinetic and Response Surface Methodology Study. PhD thesis, Faculty of Resource Science and Technology.

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Abstract

Excessive heavy metals discharge into the environment has become a great concern worldwide and needs an effective long-term solution. Melia azedarach tree is a member of the Meliaceae family and is used as a source of hard wood; however, the leaves and twigs are burnt due to lack of industrial applications. In this study, biomass from Melia azedarach leaves and twigs was used to prepare activated carbons via molten salt synthesis with ZnCl2 as activator, for the removal of Cu(II), Pb(II) and Ni(II) ions from aqueous medium. Both activated carbons were characterised, evaluated for batch adsorption and fitness with the kinetic and isotherm models. The central composite design (CCD) was applied to optimise the removal of Cu(II), Pb(II) and Ni(II) by relating the mutual interactions of the factors including adsorbent dosage, initial metal concentration and contact time. The surface area of activated carbon from Melia azedarach leaves (121.592 m2g-1) and twig (91.423 m2g-1) was substantially larger than the feedstock leaves (1.02 m2g-1) and twigs (0.485 m2g-1). The batch adsorption from both activated carbons for Pb(II) and Ni(II) removal followed the Freundlich isotherm, while Cu(II) adsorption followed the Temkin isotherm. Applying central composite design in response surface methodology, the optimised removal efficiency for Cu(II), Pb(II), and Ni(II) using Melia azedarach leaves activated carbon as adsorbent was determined to be 98.63%, 99.52% and 88.18% respectively while optimised adsorption capacity was found to be 192.12 mgg-1, 170.94 mgg-1, 160.77 mgg-1. On the other hand, the optimised removal efficiency for Cu(II), Pb(II), and Ni(II) using Melia azedarach twigs activated carbon as adsorbent was found to be 99.66%, 95.05% and 97.53% respectively while optimised adsorption capacity was determined to be 172.32 mgg-1, 254.59 mgg-1, 232.16 mgg-1 , optimised through central composite design in response surface methodology. The activated carbon derived from Melia azedarach biomass has demonstrated the capacity to be a value-added product as an adsorbent capable of adsorbing heavy metals from aqueous medium.

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