Removal of heavy metals, lead, cadmium, and zinc, using adsorption processes by cost-effective adsorbents

Heavy metals have been utilized by human beings for thousands of years, and they pervade nearly all aspects in modern economic activities. However, heavy metal ions such as cadmium, lead, zinc, nickel, and copper are detected in waste streams from mining operations, battery manufacturing, electroplating, and smelting industries due to their extensive use. The adverse effects of heavy metals on human health have been studied by international organizations including the WHO. Although the emissions have declined in most developed countries, in some parts of the developing world, human exposure to heavy metals is still a severe problem. Various technologies of heavy metal removal from effluent have been investigated and reported in literature including precipitation, membrane filtration, coagulation, adsorption/ion exchange, and electrochemical treatment. In this chapter, adsorption studies of cadmium, lead, and zinc onto various low-cost adsorbent materials will be reviewed. The equilibrium isotherm, batch kinetic studies, the effect of variables including contact time, initial pH, adsorbate concentrations, dosage, and the application of adsorption models will be discussed.