Competitive heavy metals adsorption on natural bed sediments of Jajrood River, Iran

The presence of heavy metal concentrations was examined in natural sediments from four sites along the Jajrood river in northeast of Tehran, the capital of Iran. Besides determination of elemental concentrations (Pb, Cu, Zn, Cd, Ni and Cr), X-ray fluorescence and X-ray diffraction tests were carried out to determine other chemical components in these adsorbents. Also the ability of sediments to adsorb these heavy metal ions from aqueous solutions was investigated. Results show that the extent of adsorption increases with increase in adsorbent concentration. The amount of adsorbed Pb, Cu and Zn in sediments was much greater than that of the other metals, and Cr was adsorbed much less than others. The adsorbabilities of sediments to heavy metals increased in the order of Pb > Cu > Zn > Cd > Ni > Cr. Based on the adsorption data, equilibrium isotherms were determined at selected areas to characterize the adsorption process. The adsorption data followed Freundlich and Langmuir isotherms in most cases. Correlation and cluster analysis was performed on heavy metals adsorption and sediment components at each site to evaluate main adsorbing compounds in sediments for each metal. Results demonstrated that heavy metals sorption is mostly related to load of organic matter in the Jajrood river sediments.