Simultaneous Adsorption of Mercury (II) and Zinc (II) Ions from Aqueous Solution onto Activated Carbons Derived from a Lowland Bioresource Waste

Abstract

Adsorption of Hg(II) and Zn(II) ions from a binary solution was examined using activated carbons (ACs) prepared from a lowland bioresource waste (Theobroma cacao pod husk). The aim of the study was to determine the potential for utilizing the plant-based ACs as a low-cost adsorbent for removing the metal ions from a binary. Batch adsorption experimentations were conducted to evaluate the initial metal ion concentration and contact time on adsorption. Spectroscopic studies including FTIR, elemental analysis (EA) and SEM were used for its characterization. Equilibrium data was examined using a comparison of linear Langmuir, Freundlich and Temkin isotherm models. The Langmuir and Temkin isotherm model provided the best fit to the experimental data for both metal ions as indicated by the values of the regression coefficient. The kinetic rates were modeled by using the Lagergren-first-order, pseudo-second-order, Elovich and Intraparticle model. The pseudo-first order, pseudo-second order equations and Elovich equation gave the best fit to the experimental data. The presence of intra-particle diffusion mechanism was prominent, although it was not the sole rate-determining step. The results showed that ACs can be effective for removing Hg(II) and Zn(II) ions from solution.