Kinetic and equilibrium adsorption studies of Pb and Zn ions from aqueous solution onto plantain stalk (<i>Musa paradisiaca</i>)

Abstract

This study presents the sorption of Pb²⁺ and Zn²⁺ from aqueous solution by Musa Paradisiaca (plantain stalk) with respect to its equilibrium and kinetic behaviour. The optimum pH was found to be 5.0 and 6.0 for the sorption of the Pb (II) and Zn (II) ions respectively. At pH 5.0, the biomass sorbed 91.7% Pb(II) and 89.85% Zn(II), while at pH 6.0, the biomass sorbed 91.16% Pb (II) and 89.55% Zn (II). The contact time for the sorption was found to be rapid in the first 5mins. The amount of metal ion sorbed was found to be rapid from the lowest concentration, 10 mg/L to the highest concentration, 500 mg/L. The Langmuir and Freundlich model for dynamic metal ion uptake proposed were well fitted for Pb²⁺ and not well fitted for Zn²⁺. The structural groups of the adsorbent were characterized by Fourier transform infrared (FTIR) Spectrometry. The following were present; hydroxyl, carbonyl, amine and phosphate groups which confirms the potential processes of sorption of the biosorbent. The first order and second order rate equation were tested and it was found that pseudo-second-order is more suitable for the sorption, having the linear coefficient of determination R² value of 0.999. The result obtained from this study indicated that plantain stalk (Musa Paradisiaca) could be employed for the removal of heavy metal contaminants from industrial effluents.

Keywords: Plantain stalk, kinetics, adsorption, biosorbent