In this study, cashew nut shells (CNS), waste from a cashew nut processing factory, have been used as an adsorbent for Pb(II) ions in water. Treatments of CNS with 1 M of H 2 So 4 , HNO 3, and NaOH solutions were performed to modify their surfaces and improve their adsorption capacities. characterization of untreated and chemical-treated CNS was carried out using nitrogen adsorption isotherm, elemental (CHN) analysis, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX). In the study of Pb(II) removal, various models of adsorption kinetics and isotherms were evaluated against the experimental data. the results showed that H 2 So 4-treated cnS exhibited the highest adsorption capacity. the chemical treatment removes impurities, alters the surface functional groups and improves specific surface areas and pore volumes of native CNS significantly. Surface adsorption and intra-particle diffusion steps were found to substantially affect the overall adsorption process of Pb(II) on H 2 So 4-treated cnS. owing to its easy preparation and comparable adsorption capacity, H 2 So 4-treated cnS has the potential to be developed as a low-cost adsorbent for the removal of pb(ii) from contaminated water. Water is a natural resource necessary for living and sustaining our ecosystem. The increases in human population and industrial processes have released more polluted water into the environment unless proper treatments are implemented effectively. Owing to the water solubility of heavy metals under favorable pH/Eh conditions, water is inevitably contaminated with heavy metals, mostly discharged from several industries 1. Such contaminated water leads to environmental problems and accumulation of heavy metals in the food chain which finally returns to human beings. Numerous disorders and diseases are caused by the deposition of heavy metals. Ions of lead, mercury, cadmium and chromium have been reported to be at the top of the toxicity list 2. Lead (Pb) ions contaminated in water are highly toxic to humans and the environment. The sources of lead include the steel and metal alloy industries, welding and electroplating processes, and manufactures of batteries, pigments and ammunition 2-4. The accumulation of lead in the human body at a certain level can seriously destroy the nervous system, organs (i.e., heart, kidneys, and reproductive system) and tissues 5,6. The World Health Organization specifies the maximum concentration of lead ions in drinking water as 0.01 mg/L 7. Several methods have been introduced to remove heavy metal ions from contaminated water such as chemical precipitation, membrane filtration, ion-exchange, electrochemical methods, flotation, and adsorption. Many methods have drawbacks which are high capital and operating costs, the requirement of extra chemicals and high energy, generation of hazardous sludge, and low performance for diluted wastewater 8. Among these methods, adsorption is very attractive owing to its easy operat...
