Abstract—Multiwall carbon nanotubes, prepared by chemical vapor deposition, have an average diameter of 60-100 nm as shown by High Resolution Transmittance Electron Microscope, HR-TEM. The Multiwall carbon nanotubes (MWCNTs) were further characterized using X-ray Diffraction and Raman Spectroscopy. Mercury uptake capacity of MWCNTs was studied using batch adsorption method at different concentration ranges up to 150 ppm. Mercury concentration (before and after the treatment) was measured using cold vapor atomic absorption spectroscopy. The effect of time, concentration, pH and adsorbent dose were studied. MWCNT were found to perform complete absorption in the sub-ppm concentrations (parts per billion levels) while for high concentrations, the adsorption efficiency was 92% at the optimum conditions; 0.1 g of the adsorbent at 150 ppm mercury (II) solution. The adsorption of mercury on MWCNTs was found to follow the Freundlich adsorption isotherm and the pseudo-second order kinetic model. Keywords—Cold Vapor Atomic Absorption Spectroscopy, Hydride System, Mercury Removing, Multi Wall Carbon Nanotubes. I. INTRODUCTION HE available source of clean water, the shrinking levels of surface water and waste waters pollution, and contamination of environment by toxic pollutants have emerged as the most serious problems facing our globe in the twenty-first century. Removal of inorganic and organic pollutants from waters is considered as one of the major investigations in the last few decades. Mercury is well known to be one of the most toxic metals known in natural ecosystems. During the 20 th century there were several major Hg poisoning catastrophes as Hg is deemed cumulative and persistent in human body and the environment as well [1]. Long-term exposure to very low levels of mercury even in water is dangerous for humans [2], [3]. It is known that Hg may be absorbed through the gastro- intestinal tract and through the skin and lungs [4]. Soluble compounds of mercury are particularly toxic because their adsorption is rapid. Nevertheless, Hg is still being used worldwide in applications such as barometers, thermometers, Yasser M. Moustafa is with the Analysis and Evaluation Department, Egyptian Petroleum Research Institute, EPRI, Cairo, Egypt (corresponding author e-mail: Corresponding author: ymoustafa12@yahoo.com). Rania E. Morsi and Mohammed Fathy are with the Analysis and Evaluation Department, Egyptian Petroleum Research Institute, EPRI, Cairo, Egypt. pumps, and lamps to name a few. Industries mainly responsible for the dispersion of mercury are: the chloro- alkali, paint, oil refining, and rubber processing and fertilizer industries [5]. An improved understanding of the toxic health effects of mercury and its bio-accumulative properties has led to greater regulatory control. The EPA has initiated regulations to control mercury emissions to air through the Clean Air Act (CAA); water through the Clean Water Act (CWA) Safe Drinking Water Act (SDWA); and from wastes and products through Resources Conservation and Recovery Act (RCRA) [6], [7]. The EPA has established a maximum contamination level (MCL) for mercury to be 2 μg/L in drinking water. The World Health Organization (WHO) also recommends a maximum uptake of 0.3 mg per week and 1 μg/L as the maximum acceptable concentration in drinking water [8]. Thus, accurate and precise qualitative and quantitative detection of mercury in aqueous media is highly recommended. The direct determination of trace concentrations of heavy metal ions has many problems. Such problems are associated with matrix interferences and low sensitivity, especially in extremely low concentrations. The direct determination by atomic spectroscopy can be problematic. For example, the determination of mercury by flame atomic absorption spectrometry is limited to high concentrations of mercury owing to the poor detection limit offered by the technique 200 μg /L. While the use of electro thermal atomic absorption spectrometry (ETAAS), although it allows better detection limits (2 μg /L, suffers from matrix interference as the high volatility of mercury restricts the ashing temperature. One of the most common analytical approaches for the determination of total mercury at lower concentrations is cold vapor atomic absorption spectrometry (CVAAS) with its high sensitivity and selectivity as well as extremely low detection limit (1 μg/L) [9]–[12]. A number of approaches have been suggested for the removal of mercury from aqueous solutions. The techniques include reduction, precipitation, ion exchange, reverse osmosis, adsorption, coagulation, etc. Though bulk techniques like simple filtration or precipitation are suitable for removing a significant fraction of the metal, they are unable to decrease the concentration of contaminant from percentage to ppm level and/or even in ppb level [13]. Thus, there is an urgent Mercury Removing Capacity of Multiwall Carbon Nanotubes as Detected by Cold Vapor Atomic Absorption Spectroscopy: Kinetic & Equilibrium Studies Yasser M. Moustafa, Rania E. Morsi, Mohammed Fathy T World Academy of Science, Engineering and Technology International Journal of Chemical and Molecular Engineering Vol:8, No:7, 2014 724 International Scholarly and Scientific Research & Innovation 8(7) 2014 scholar.waset.org/1307-6892/9999824 International Science Index, Chemical and Molecular Engineering Vol:8, No:7, 2014 waset.org/Publication/9999824