Adsorption of lead and zinc on bed sediments of the river Kali

The adsorption characteristics of the bed sediments collected from the River Kali in western Uttar Pradesh, India, have been studied for the uptake of lead and zinc ions. The parameters controlling the uptake, viz. initial metal ion concentration, the solution pH, sediment dose, contact time, and particle size have been evaluated. The adsorption of metal ions increases with increasing initial metal ion concentration. The adsorption of the two metal ions on the bed sediments follows two phases: a linear phase of adsorption and then a quasi-equilibrium state (almost flat plateau). The quasi-equilibrium state was attained within 45 min for both the metal ions. It is observed that the extent of adsorption increases with the increase of pH of the solution and metal ion concentration decreases with increase in pH value. Further, the adsorption of metal ions increases with increasing adsorbent doses and decreases with adsorbent particle size. The geochemically important elements such as Fe and Mn have also been determined in various grain size fractions of the sediments and correlated with the adsorption of metal ions. The adsorption data of the two metal ions has also been analysed with the help of the Langmuir and Freundlich models to evaluate the mechanistic parameters associated with the adsorption process, viz. monolayer capacity and sorption intensity.