Melia Azedarach Sawdust-Based Activated Carbon, an Efficient Adsorbent for the Removal of Heavy Metals From Water

Abstract

Herein, an efficient adsorbent was prepared at high temperature using sawdust of Melia azedarach plant. The prepared adsorbent was characterized by instrumental techniques like EDX, XRD, SEM, FTIR, TGA, and surface area analyzer. The fabricated activated carbon (AC) was used as an adsorbent for the removal of Pb²⁺ Ni²⁺, and Cu²⁺ from aqueous solution utilizing batch adsorption approaches. At pH 6, the highest elimination of Pb²⁺ and Cu²⁺ was achieved, whereas for Ni²⁺ the optimum pH was 5. The recorded time interval for reaching equilibrium was 60 min in the case of Pb²⁺ and Ni²⁺ metal, whereas 80 min in the case of Cu²⁺ ion. The adsorbent was found to be more effective at high doses, with an optimum dose of 0.05 g. The isotherm models, including Langmuir, Freundlich, Temkin, Jovanovich, and Harkins-Jura models, were utilized to decide the best fit model for explaining the isotherm adsorption data. Out of the tested models, the Langmuir model was more effective with high R² values of 0.997, 0.991, and 0.984, respectively, for Pb²⁺, Ni²⁺, and Cu²⁺ ions. The pseudo-second order model best fitted the kinetics data with high R² values of 0.980, 0.991, and 0.987 correspondingly, for the mentioned ions. The estimated ∆H° values were −22.699, −31.147, and −33.199 J·mol⁻¹ respectively for Pb²⁺, Ni²⁺ and Cu²⁺, indicated the process to be an exothermic one. The favorable nature of the studied adsorption was obvious from the recorded negative values of Gibbs free energy. The fabricated AC could thus be considered as an efficient and cheap alternative to commercially available activated carbon; however, further confirmation and validation of the present findings by other researchers is mandatory.