Equilibrium modeling and pH-dependence of the adsorption capacity of Vitex doniana leaf for metal ions in aqueous solutions

This study involved the examination of biomass, Vitex doniana leaf powder, in the adsorption of heavy metals from water. The water samples were obtained from two sources in Nasarawa town in Nasarawa State, Nigeria; River Tammah (one of the two major river sources of water for drinking, domestic, irrigation and other agricultural uses in the town) and the confluence of two rivers called "Magami". Batch pH profile experiment for lead and iron indicated that metal ion binding capacity of the biomass increased as pH increased, but was the reverse for magnesium ions. Optimum uptake for lead and iron occurred at pH 7.0-7.8 for lead and 7.8 for Iron in water from river Tammah. Optimum uptake occurred at the same pH ranges for both Lead and Iron in water sample from Magami. In both cases optimum desorption occurred for magnesium ions. At room temperature and with good equilibrium the adsorption capacities of V. doniana leaf powder for lead and iron ions were 99.98 and 86%, respectively. V. doniana leaf powder therefore showed good binding capacity for lead and iron but was not efficient for magnesium.