Biosorption of Mercury (II) from Aqueous Solutions by Moringa oleifera Bark: Equilibrium and Kinetic Studies

Abstract

A biosorbent prepared from Moringa oleifera bark was used to remove mercury (II) from aqueous solutions. The initial pH, biosorbent dose, contact time, and initial mercury concentrations, were evaluated. The ability of Moringa oleifera bark to remove mercury at various pH (1–8) was studied. The maximum capacity (q"max" ) of biomass Calculated from Langmuir isotherm was found to be 33.22mg Hg2+/g at pH 7.Biosorption equilibrium was established in approximately 120 min. The equilibrium data were described well by Langmuir and Freundlich models. Adsorption kinetics data were analyzed using the pseudo-first-, pseudo-second-order equations. Infrared (IR) spectra and X-ray diffraction (XRD) analysis of pure and mercury loaded biomass were performed. The adsorbed mercury on biomass was desorbed using 10 ml of 4.0 M HCl solution, which it could be reused for other biosorption assays. This study consider the possibility of using bark of Moringa oleifera tree as an inexpensive biosorbent for the removal of Hg (II) from contaminated chemical and mining industry wastewaters. It is also suggested that the dried biomass might be simply kept and used in a very low cost metal ion removal system.

Keywords: Biosorption, Moringa oleifera, mercury, isotherm, kinetic