Chromium is one of the extremely toxic heavy metals found in various waters. Several processes such as chemical precipitation, membrane filtration, ion exchange and adsorption, have been reported to remove Cr(VI) ion from aqueous solutions. The latter is a more useful method for metal removal than other processes. The absorbents commonly recommended for Cr removal are alumina, silica and activated carbon. Many reports have appeared on the development of low-cost activated carbon adsorption from cheaper and readily available materials for the removal of heavy metals from waters. Walnut shells are an agricultural waste product which is mainly used as fuel. Carbon nanotubes (CNTs), on the other hand, are increasingly attracting interest since their discovery in 1990. Their small sizes, large surface areas, high mechanical strengths and remarkable electrical conductivities indicate their tremendous potential for future engineering applications. In this study, the adsorption of Cr(VI) ions from aqueous solutions is investigated under different conditions using two different nano-structured adsorbents namely CNTs and low cost activated carbons.

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