Study of adsorption of copper, lead, and zinc in their various chemical forms from the sediments of the Brahmaputra river, Assam, India

Abstract

AbstractThe natural organic matter and the iron and manganese oxides are potential adsorbing agents of heavy metals in sediments and create a sink for them to control their bioavailability and mobility in the aquatic environment. The salinity and pH of the surrounding water highly affect the fixation of heavy metals on the river sediments. The adsorption of copper, lead, and zinc ions in the Brahmaputra river sediment is analyzed by batch techniques. The parameters controlling these metal ions adsorption are solution pH, contact time, adsorbent amount, and adsorbate concentration. The equilibrium adsorption capacities of the sediment particles of the various sizes (< 53, 53–73, and 74–149 μm) are measured for copper, lead, and zinc ions and extrapolated using linear Freundlich and Langmuir isotherms. The results provide strong evidence to support the hypothesis of adsorption mechanism. It is found that the extent of adsorption is increasing with decreasing particle size, and this may be attributed to the enhancement of the surface area available for adsorption to occur. The sediment is studied for metal speciation, for nine heavy metals, to explain their behavior in the five sequential extraction steps. This is an interesting study as zinc is present in the air, soil, water, and almost all food items, and industries naturally release zinc into the environment.